XSD Seminars

XSD Seminars are an open forum where speakers from the U.S. and abroad, as well as XSD, present their latest research. All are cordially invited to attend.

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Past Seminars

2014

Nov 18
Tuesday

Electrochemical and Local Structural Analysis of the Li3V(2-2x/3)Mgx(PO4)3/C (x=0, 0.15, 0.3, and 0.45) Cathode

Speaker: Soojeong Kim, University of Michigan
XSD Seminar
435/C010 @ 1:30 PM
View Description
Electrochemically stable phosphates promise high reversible capacity, high operating voltage, and good ion mobility and have the potential to provide electrochemically superior, environmentally friendly (Co-free) and affordable battery materials. Li3V(2-2x/3)Mgx(PO4)3/C (x=0, 0.15, 0.3, and 0.45) composite phosphate cathode materials show high reversible capacity, high operating voltage and good cycling stability. In order to understand the functioning of this cathode at the molecular level, we have determined the local vanadium structure as a function of state of charge using in-situ x-ray absorption spectroscopy (XAS). The Principal Components Analysis (PCA) method has been used to determine the number of components in the LVP system. The XAS results verify for the charge compensation involves V cycling between V3+ and V5+ during charge and discharge and shows that these changes in oxidation/reduction are accompanied by modest changes in V-O bond length but little apparent change the overall local structure of the V and its neighboring atoms. In contrast, there is a significant change in local structure if the cut-off potential is increased from 4.5V to 4.8 V. Once the electrode has been charged to 4.8V it undergoes an irreversible conversion to a distorted structure. While the vanadium is still redox active, it is not converted back to the starting form, even at potentials as low as 2.0 V cut off region. Although the details of the behavior depend on the level of Mg doping, similar results are found for all samples. These data provide for the first time a molecular level explanation for the observation that vanadium phosphate batteries suffer irreversible capacity loss if charges above 4.5 V
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Nov 17
Monday

Self-Assembly of Semiconducting Polymers and Fullerenes for Photovoltaic Applications

Speaker: Rachel Colleen Huber, University of California
XSD Seminar
435/C010 @ 1:30 PM
View Description
Here we present methodologies for control of nanoscale film morphology and self-assembly of semiconducting polymers and fullerenes for use in photovoltaic devices. These materials are of interest to the photovoltaic community due to their facile processing and relative low cost. Organic photovoltaics consist of a photo-absorbing electron-donating polymer and an electron-accepting fullerene, upon exposure to light an electron-hole pair (excition) is formed. This exciton can travel 10-20 nm before if finds a polymer-fullerene interface or it will recombine. Therefore, the study of the nanoscale morphology is pivotal towards understanding and improving device properties. First, we explore how the crystallinity of different molecular components of a blended film affects device performance. Using grazing incidence wide-angle X-ray scattering (GIWAXS) we find that two different device fabrication techniques require polymers with different crystallinities. Next, we examine a hydrogel network formed from a charged amphiphilic polymer, poly(fluorene-alt-thiophene) (PFT). This polymer self-assembles into rod-like structures in water and also shows improved conductivity in dried films due to its assembled structure. Here we use small angle X-ray scattering (SAXS) and TEM to confirm the nanoscale rod-like assembly, we then employ rheology to study how the three dimensional network is held together. The final section of this talk will examine the addition of a water-soluble fullerene, C60-N,N-dimethylpyrrolidinium iodide, to PFT as a step towards water-processable organic solar cells. Photoexcitation of aqueous assemblies of cationic polymers and fullerenes result in the formation of free charge carriers (polarons). These separated charge carriers are stable for days, which is unprecedented in polymer/fullerene solutions. We have shown that through fundamental studies of device architectures and intelligent molecular design, self-assembly has the power to provide a pathway towards improved photovoltaic device properties.
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Oct 8
Wednesday

The Role of Materials Science in Energy Efficient Information Processing Systems of the Future

Speaker: Dr. Supratik Guha, IBM Research
XSD Seminar
401/A1100 @ 10:00 AM
View Description
As conventional scaling of the microprocessor comes to an end, there is extensive interest in examining materials and devices that could form the underpinnings for transistors that might replace silicon some day, new memory elements, and data transport mechanisms. There is also the more far reaching interest in going beyond conventional computing and exploring non Boolean forms of logic, or computing that is deeply integrated with sensors. I will describe some of the work in these areas, using a few specific examples and case studies in carbon electronics, silicon photonics, and physical analytics. I will also describe some of the work in new materials for photovoltaics that has spun off from this materials activity.
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Oct 3
Friday

Peering into the Past: Using APS to Illuminate the Early Evolutionary History of Birds

Speaker: Peter J. Makovicky, Field Museum of Chicago
XSD Presentation
431/C010 @ 11:00 AM
View Description
Recent decades have seen a dramatic growth in the fossil record of birds and their feathered dinosaur relatives, both in quantity (number of species and specimens), and quality (preservation of soft tissues and gut content). Application of techniques including micro-CT and x-ray fluorescence hold great promise for informing hypotheses on early avian evolution, and the history of hallmark avian characteristic such as feather coloration.
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Sep 30
Tuesday

The Medipix 3RX Detector and Other New Products from Quantum Detectors

Speaker: Roger Goldsbrough and Brian McGregor, Quantum Detectors
XSD Presentation
431/C010 @ 2:00 PM
View Description
The APS detector pool will soon be testing the Medipix 3RX detector system known as Merlin. It offers significant advantages over Medipix 2 and many other detectors currently available on the market. Quantum Detectors will be here giving an overview of what we can expect from this detector.

Quantum Detectors will also tell you about some of their products that some APS beamlines are already benefiting from such as Xspress 3, which the detector pool have recently purchased to operate with the new Vortex ASIC. The combination will offer ≤3.9 Mcps count rates with excellent resolution and has been operating successfully on Mark Rivers beamline for the past few months. The V2F100 is 100X faster than industry standard and the Zebra choreographs beamline devices and triggers from encoder positions.
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Sep 18
Thursday

New Detector Solutions from Raptor Photonics

Speaker: Mark Donaghy, Raptor Photonics
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Raptor Photonics, a UK based technology company, is a leader in the design and development of high-end digital camera solutions. We are a spin-out from Andor Technology. We offer a range of sensors from large format CCDs, EMCCD and CMOS, with various coatings from X Ray to SWIR. Raptor has designed cameras for scientific, industrial and surveillance OEMs. Raptor has also designed cameras for X-Ray applications including direct and indirect sources.
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Sep 18
Thursday

Probing the Nano World with EXAFS and XANES

Speaker: Dr. Soma Chattopadhyay, Illinois Institute of Technology
XSD Presentation
401/B4100 @ 11:00 AM
View Description
EXAFS (extended x-ray absorption fine structure) and XANES (x-ray absorption near edge structure) spectroscopy are powerful characterization tools and have broad applications in material science, biology, chemistry, physics, environment, geology, engineering and nanoscale materials. I have used the quick-EXAFS and quick-XANES facility at 10 ID beamline of APS to do in-situ studies of battery materials during their cycling process, in-situ chemical synthetic reactions and also ex-situ studies of quantum-dots, oxides and metal nanoparticles. I shall present my results on the following topics:

(a) Characterization of biomolecule - inorganic nano-hyrbrids : the case of Au core- Ag shell nanoparticles inside apoferritin protein.
(b) In-situ study of the growth mechanism of Mo-doped metallic Fe and hollow g-Fe2O3 nanoparticles.
(c) Role of Sr dopants in improving the mechanical properties of Al-Si eutectic alloys used in car engines.
(d) The lung bacteria Pseudomonas aeruginosa’s defense against quantum dots and released toxic materials.
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Sep 15
Monday

Chemical Frustration: Lessons in Materials Design from Complex Intermetalic Phases

Speaker: Professor Daniel C. Frederickson, University of Wisconsin at Madison
XSD Presentation
431/C010 @ 11:00 AM
View Description
Intermetalic phases—solid state compounds that form upon alloying metallic elements together—comprise a realm of immense structural diversity: their structures range from simple variants of the familiar fcc, bcc and hcp lattices, to the giant cubic unit cells of NaCd2 (>1,000 atoms/cell) and Al55.4Cu5.4Ta3.9 (23,134 atoms/cell), to quasicrystals such as YbCd5.7 whose geometries defy description with 3-dimensional unit cells. A limiting factor in realizing the broad technological applications promised by this diversity of atomic arrangements is our inability to understand, let alone control, the crystal structures of these compounds. An emerging theme in the study of these phases is a link between structural complexity and the coexistence of mutually exclusive bonding or packing modes. One focus of our group’s research has been pursuing this theme using an interaction of theory and experiment. In this seminar, we will discuss some of our recent advances in this pursuit, including (1) the development of the DFT-chemical pressure analysis for creating graphical and intuitive representations of the tension between electronics and atomic size requirements, and (2) the revealing of an expanding range of structural features, including periodic interfaces and icosahedral clusters, as the products of chemical pressure release.
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Sep 9
Tuesday

Examining Relationships Between Synthesis, Structure and Magnetism in Nanomaterials with X-ray Spectroscopy

Speaker: Dr. George E. Sterbinsky, Brookhaven National Laboratory
XSD Presentation
401/A1100 @ 11:00 AM
View Description
This talk details synchrotron x-ray investigations of two ferromagnetic materials that show unexpected magnetic properties on the nanoscale: cobalt carbide nanoparticles and epitaxial lanthanum cobaltite thin films. Cobalt carbide is not known to be a strong ferromagnet in the bulk phase, yet nanoparticles of this material synthesized by wet chemical methods have properties comparable to known rare-earth free permanent magnets. Lanthanum cobaltite is a paramagnetic material that becomes ferromagnetic when synthesized as a thin film. To gain insight into the unique magnetic properties of these materials, a variety of x-ray spectroscopy based experiments were carried out. In lanthanum cobaltite, the effects of epitaxial strain on the atomic and electronic structures of the material were measured using x-ray absorption fine structure (XAFS) spectroscopy and x-ray diffraction. From the observed atomic and electronic structures, the nature of the strain induced magnetic phase is deduced. A combination of x-ray magnetic circular dichroism (XMCD) spectroscopy and time resolved quick XAFS spectroscopy was used examine the relationship between the Co-carbide nanoparticle synthesis and the resultant magnetic properties. These results give insight into how to tailor the synthesis of nanomaterials to optimize magnetic properties.
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Sep 5
Friday

Charge and Spin Density Waves Studied by Coherent X-ray Diffraction

Speaker: Vincent Jacques, CNRS
XSD Presentation
431/C010 @ 1:30 PM
View Description
Since the development of 3rd generation synchrotron sources, coherent x-ray diffraction has been used to probe many systems in a new way, through the defects they contain. Indeed, when defects are present in lattices, speckles appear on the detected Bragg reflections, and allow various investigations, as a function of time, temperature, pressure, electrical current, etc. We demonstrated recently that this technique can be used to detect a single dislocation in crystal, and now turn to the multi-dislocations case. Beyond atomic lattices, this method has also been used successfully to probe electronic and magnetic modulations like charge and spin density waves. This allowed in particular to detect density waves dislocations, to probe charge density waves in the static and electrically-driven states and to study the coexistence of charge and spin density waves in chromium.
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Sep 2
Tuesday

Bent Crystal Laue Analyzer (BCLA) for Copper Speciation Studies and Recent Progress on Optics Testing at 1-BM

Speaker: Naresh Kujala, Advanced Photon Source
XSD Presentation
401/A1100 @ 11:00 AM
View Description
In this talk, I will present the design of Bent Crystal Laue Analyzer (BCLA) detection system for copper speciation in biological samples. The analyzer has energy resolution of 14 eV@ Cu Kα line and it has notable advantages to resolve the Cu Kα1, Kα2, and Kβ fluorescence lines while offering a very low background. The designed BCLA will be used on copper speciation studies in biological samples with specific applications to cancer biology. I will also present newly reconfigured optics and detector test beamline (1-BM) at the Advanced Photon Source-Argonne National Laboratory. I will show the beamline experimental stations layout and beamline optical components. The beamline have two modes of operations: White beam mode and monochromatic beam mode. Here I will give an overview of the recent progress on optics testing including the testing of Kirkpatrick-Baez (K-B) mirrors and measurement of focus spot; X-ray microscopy experimental setup for investigating the performance of Multilayer Laue lens (MLL) and Fresnel Zone Plates; Silicon Bent Crystal Analyzer testing experimental setup; and Talbot x-ray grating Interferometry for measurement of coherence lengths. I will also discuss x-ray Topography for crystal studies. Finally, I will present the optical ray-tracing studies for test set-ups that take advantage of the polarization variation of the bending magnet radiation above and below the horizontal plane of the 1-BM beamline.
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Aug 29
Friday

Image Reconstruction Advancements for Absorption- and Phase-contrast Tomography

Speaker: Mark Anastasio, Washington University
XSD Presentation
401/A1100 @ 12:00 PM
View Description
In this talk we review recent advancements in image reconstruction methodologies for a variety of X-ray imaging problems. Even with hardware acceleration, the overwhelming majority of available iterative algorithms for 3D image reconstruction that implement non-smooth regularizers remain computationally burdensome and have not been translated for routine use in time-sensitive applications. In this work, two accelerated variants of the fast iterative shrinkage thresholding algorithm (FISTA) for image reconstruction in absorption- and propagation-based X-ray computed tomography (CT) are proposed. The first algorithm seeks to minimizes a penalized least squares (PLS) cost function involving a TV penalty while the second assumes a penalty formed as the sum of a TV penalty and a wavelet-sparsified l1-norm of the object. We also describe an improved image reconstruction approach for grating-based X-ray phase-contrast CT, in which the 2nd order statistical properties of the object property sinograms are exploited, including correlations between them. The problem is formulated within a multi-channel (MC) image reconstruction algorithm framework in which the three object properties are simultaneously estimated. An algorithm based on the proximal point algorithm and the augmented Lagrangian method are proposed to rapidly solve the MC reconstruction problem.
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Aug 29
Friday

Recent Development in Cryogenic X-ray Microscopy and Applications

Speaker: Si Chen, Advanced Photon Source
XSD Presentation
402/E1100 @ 11:00 AM
View Description
In this presentation, I will speak on the development in cryogenic X-ray fluorescence (XRF) microscopy in the past three years at the APS, including the Bionanoprobe (BNP) at LS-CAT and a cryojet-equipped microprobe at 2IDD beamline and their applications. Hard XRF microscopy is one of the most sensitive techniques for studying trace elements within biological samples and other soft materials. Conventional sample preparation methods usually involve dehydration, which removes water and may consequently cause structural collapse. Radiation-induced artifacts may also become an issue, particularly as the spatial resolution increases beyond the sub-micrometer scale. To allow imaging under hydrated conditions, close to the ‘natural state’, as well as to reduce structural radiation damage, we have developed the BNP. It is a scanning XRF nanoprobe with cryogenic capabilities, dedicated to studying trace elements in frozen-hydrated biological systems and other soft materials. It provides a spatial resolution of 30 nm for both two- and three-dimensional imaging. In addition to life sciences, other fields of research, such as materials science, also benefit from the use of BNP mainly due to its high spatial resolution and low temperature capabilities. To accommodate the increasing requests of performing cryogenic experiments, we have also developed a cryojet-equipped XRF microprobe by implementing a cryojet to the XRF microprobe at 2IDD beamline with optimized configuration. This technical innovation is highly transferable in the way that a cryojet can be integrated on most existing microprobes with minimal instrumentation.
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Aug 26
Tuesday

Ultrafast Studies of Atomic and Molecular Dynamics: Theory and Practice

Speaker: Paul Hockett, National Research Council of Canada
XSD Presentation
401/A1100 @ 11:00 AM
View Description
In this talk I will discuss ultrafast (femto-second) studies of electronic and nuclear dynamics in atomic and molecular systems, probed via photoionization in the low-energy (less than few eV) regime. Fundamentally there are two key aspects to such studies: the dynamics of the prepared wavepackets (with rotational, vibrational and/or electronic components), and the probe process itself [1]. Understanding both aspects provides a significant challenge to theory and experiment, particularly in complex light-matter interactions. Our recent work has begun to address some of these issues, and I will discuss some examples including atomic photoionization with shaped laser pulses [2], multi-dimensional experimental studies of dynamics in butadiene [3] and combined experimental and theoretical studies of excited state molecular dynamics of CS2 in the molecular frame [4]. The work will also be discussed in the context of similar methodologies applied in the atto-second and X-ray regimes, highlighting the underlying physics & outstanding issues common to these different fields.
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Aug 22
Friday

Multi-edge XAS Studies of Metalloproteins, Biomimetics, and Donor-acceptor Compounds

Speaker: Logan Giles, University of New Mexico
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Utilizing multiple beam lines and excitation edges, the geometric and electronic structural information of metalloproteins, biomimetic and donor-acceptor compounds were studied. The MOSC family of molybdenoenzymes, which were recently discovered, have been studied via Mo K-edge XANES and EXAFS to determine structural insight, which will be critical for further mechanistic studies. Also, a spectrochemical series of biomimetic model complexes of FeFe-Hydrogenase were studied using Fe, S, C, and O K-edges, and L-edges. This work allowed for the quantitative analysis of pre-edge features to be used for future synthetic work. Lastly, a series of Pt and Pd donor-acceptor complexes were analyzed via Pt, Pd, S, Se and Cl K-edges and L-edges. This work is still under way to help explain excited state triplet lifetimes.
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Aug 21
Thursday

X-ray Imaging of Ultrafast Phase Separation in Magnetite and Spin Injection into Copper

Speaker: Roopali Kukreja, Stanford University
XSD Presentation
432/C010 @ 10:00 AM
View Description
In recent years, there has been a renewed interest in magnetic materials and correlated oxides due to major advance in thin-film growth technology. Materials showing metal insulator transition with orders of magnitude drop in conductivity, have become a potential candidate for novel electronics and photonics devices. While in data storage, the discovery of the Giant Magnetoresistance (GMR) effect has revolutionized read head technology of the hard disk drives. The subsequent discovery of the Spin Transfer Torque phenomenon, where a spin current is used to switch the magnetization, promises to be a good candidate for Magnetic Random Access Memory devices.

In the first part of my talk I will focus on the metal insulator transition (verwey transition) in magnetite triggered by optical excitation. Magnetite (Fe3O4), is the first oxide where a relationship between electrical conductivity and fluctuating/localized charges was observed, with a drop in conductivity by two orders of magnitude at TV=123K. The Verwey transition is also accompanied by a structural change from monoclinic to cubic symmetry. Despite decades of research and indications that charge and orbital ordering play an important role, the mechanism behind the Verwey transition remains unclear. Recently, three-Fe-site lattice distortions called trimerons have been identified as the true microscopic face of electronic order in the low temperature-insulating phase. I have studied the real time response of insulating magnetite to optical excitation with ultrafast soft X-ray scattering as well as optical pump probe experiments and discovered this to be a two-step process. After an initial femtosecond (~300fs) destruction of individual trimerons in the corresponding lattice, a phase separation into residual insulating trimeron and cubic metallic phases on a 1.5 picosecond timescale is observed.

The second part of my talk involves understanding spin transport into the non-magnetic metal Cu from an adjacent Co ferromagnet. It has been predicted that a small non-equilibrium magnetization due to spin accumulation, builds up in Cu near the interface due to differential spin transport across the interface. I have developed an extremely sensitive detection method based on element specific x-ray magnetic circular dichroism microscopy coupled with synchronizing electrical and synchrotron pulses at MHz rates. The sensitivity of this technique has allowed me to detect the extremely small transient Cu magnetization of < 0.0001 B/atom and to show that its sign is the same as that in Co.
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Aug 20
Wednesday

Approaching Protein Dynamics with Coherent X-ray Scattering

Speaker: Dr. Luxi Li
XSD Presentation
436/C010 @ 11:00 AM
View Description
The diffuse scattering of protein crystals contains the information of dynamic disorders (e.g. the atomic and molecular fluctuations) and static disorders (e.g. mosaicity) in the crystals. The biological functions of proteins are related to the intramolecular motions, such as domain fluctuations. This work presents the first approach to protein dynamics in single crystals using X-ray Speckle Visibility Spectroscopy combining with the photon statistics analysis (XSVS-PS). The XSVS-PS technique was benchmarked with the well-known X-ray Photon Correlation Spectroscopy (XPCS) method on the study of Brownian motions in 1% Silica suspension [1]. XSVS is a single-shot technique, which is essential for samples suffering from radiation damage, especially for biological materials. The XSVS measurement on the Concanavalin A (ConA) crystal was performed at the APS 34-ID-C beamline with the fully coherent X-ray beam at room temperature. The diffuse scattering patterns about single Bragg peaks were recorded with a series of different integration times. The diffuse component about a [h0l] reflection peak of the ConA crystal indicates a static disorder on the surface of the crystal with a visibility around 0.6 independent of the integration time. The result supports that the XSVS-PS method is feasible for studying the collective motion of proteins in single crystals. However, the approaching of protein dynamics will need an increase of the X-ray coherent flux by one to two orders of magnitude, which will be achieved by the future MBA upgrade of APS.

[1] Luxi Li, P. Kwasniewski, D. Orsi, L. Wiegart, L. Cristofolini, C. Charona, A. Fluerasu, “Photon Statistics and Speckle Visibility Spectroscopy with Partially Coherent X-rays", J. Synchrotron Rad., accepted, 2014.
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Aug 19
Tuesday

Developing Insights into Catalytic Processes Through in situ Studies: Investigations of Size Selected Clusters and Solution Synthesized Nanoparticles

Speaker: Eric Tyo, Argonne National Laboratory, Material Science Division
XSD Presentation
401/A1100 @ 1:00 PM
View Description
To develop catalytic processes with higher selectivity and activity, fundamental insights need to be gained into the active site specific mechanisms occurring. The most effective way of gathering such insights is by performing in situ studies of well-defined systems. Soft-landed, size and composition selected subnanometer Ag clusters are active for the selective partial oxidation of propylene at relatively low temperatures. Temperature programmed reactivity (TPRx) was performed with in situ synchrotron X-ray characterization, Grazing Incidence Small Angle X-ray Scattering (GISAXS) and X-ray Absorption Spectroscopy (XAS), to determine structural morphology and oxidation state during catalytic activity. Au doped Cu3O4 nanoparticles are also investigated, in a similar method, for the oxidative dehydrogenation of cyclohexane. Significant influence in catalytic activity is observed due to the particle size and doping of Au. These investigations illustrate the power of in situ studies towards developing the fundamental understanding necessary for the directed design of next generation catalysts.
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Aug 19
Tuesday

High-pressure Single-crystal Neutron Scattering Study of the 245 Superconductor

Speaker: Wei Bao, Renmin University of China
XSD Presentation
401/A1100 @ 10:00 AM
View Description
The iron vacancy order and the block antiferromagnetic order exist in the new iron 245 superconductors [1,2]. The appearance of the superconductivity crucially depends on the perfectness of the vacancy order [3]. The magnetic and vacancy orders in superconducting (Tl,Rb)2Fe4Se5 (245) single-crystals were investigated using high-pressure neutron diffraction technique [4]. Similar to the temperature effect, the block antiferromagnetic order gradually decreases upon increasing pressure while the Fe vacancy superstructural order remains intact before its precipitous drop at the critical pressure Pc =8.3 Gpa. Combining with previously determined Pc for superconductivity, our phase diagram under pressure reveals an intimate connection among the block antiferromagnetic order, the Fe vacancy order and superconductivity for the 245 superconductor.

[1] W. Bao, Q. Huang, G-F. Chen et al., Chin. Phys. Lett. 28, 086104 (2011).
[2] F. Ye, S. Chi, W. Bao et al. Phys. Rev. Lett. 107, 137003 (2011).
[3] W. Bao, G-N Li, Q. Huang et al., Chin. Phys. Lett. 30, 027402 (2013).
[4] F. Ye, W. Bao, S. Chi et al., arXiv:1405.4020 (2014).
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Aug 18
Monday

Heterogenous Processing of Imaging Data Sets for High-throughout, Single Cell Characterization

Speaker: Dr. David Kissick, Univ. of Illinois at Urbana-Champaign
XSD Presentation
436/C010 @ 11:00 AM
View Description
Cell-to-cell variability and functional heterogeneity are integral features of multicellular organisms. Assays to elucidate these vital chemical variations are best performed with single cell samples because tissue homogenates average the biochemical composition of many cells and oftentimes include extracellular components. Numerous single cell microanalysis techniques have been developed, but many rely on molecular probes that often produce limited throughput or information. Mass spectrometry (MS) is an untargeted, multiplexed and sensitive analytical method that is well-suited for studying chemically complex single cells that have low analyte content. In this work, both Aplysia californica neurons and rat pituitary cells have beenare analyzed using optical microscopy-guided matrix-assisted laser desorption / ionization time-of-flight (MALDI-TOF) MS. The cells are dispersed onto a microscope slide to generate a sample where potentially hundreds to thousands of cells are separately located. Optical imaging is used to determine the cell coordinates on the slide, and the locations are used to automate MS analysis to each cell. While larger neurons can be directly localized, for the pituitary cells, the cells were labeled with a nuclear dye and dispersed onto a microscope slide, generating a sample where hundreds to thousands of cells were separately via fluorescent imaging to determine the cell coordinates on the slide, with the locations used to automate the MS analysis specifically to target each cell. The assay yielded a large amount of data, which was statistically analyzed using a heterogeneous computing module that parallelizes calculations to reduce processing time. For the pituitary cells, principal component analysis (PCA) was also applied to several thousand cells, with the results highlighting distinct cell types such as melanotrophs, originating from functionally different pituitary regions of the pituitary. Rare cells within the population were also found using a modified PCA method that focuses on signals described by the lower principal components. We demonstrate that the single cell MALDI-TOF MS approach described here can be used to achieve high-throughput analyses of cellular populations.
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Aug 14
Thursday

Direct and sequential multi-photon ionization of rare-gas atoms in the XUV

Speaker: Tommaso Mazza, European X-Ray Free Electron Laser Facility GmbH
XSD Seminar
401/A1100 @ 11:00 AM
View Description
The interaction of individual atoms with intense short-wavelength radiation is a fundamental issue in particular for atomic physics, but also in general for many other areas of FEL-based science. To understand the ionization dynamics and the role of sequential and direct multi-photon absorption processes, relevant information can be obtained experimentally from both ion and electron spectroscopy, supported by theoretical approaches. In this report the results of a broad investigation are presented, performed at different XUV photon energies delivered by the Free electron LASer in Hamburg (FLASH), on systems with electronic structures of different complexities (Ar and Xe atoms). At first, unexpectedly high charge states are reported for Argon at different photon energies. The comparison of the intensity dependent ion yield spectra with the results of rate equation calculations reveals the importance of excited states during the different steps of the ionization ladder. In addition, electron spectroscopy is used in combination to ab-initio calculations to provide a quantitative insight into the relevance of direct multi-photon absorption in the ionization process. The more complex and intriguing case of Xe shows, in contrast to the case of Ar, a more pronounced and photon energy dependent production of highly charged ions. The role of collective electronic response in the multiphoton ionization will be discussed considering the one photon and two-photon direct 4d electron emissions with respect to their dependence on the photon energy tuning in the region of the 4d->εf giant resonance.
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Aug 12
Tuesday

The Physics Endstation at the High Energy Beamline P07 at PETRA III

Speaker: Uta Rütt, Petra III Synchrotron, DESY
XSD Presentation
431/C010 @ 2:00 PM
View Description
The high energy materials science beamline at PETRA III (P07) is designed to cover photon energies from 50 to 200 keV. This beamline is jointly operated by Helmholtz Centre Geesthacht (2/3) and DESY (1/3), which is responsible for a triple axis diffractomer in the physics endstation. The instrument is designed for a broad variety of diffraction experiments covering scattering on surfaces as well as powder diffraction up to single crystal crystallography in different sample environments. The instrument is equipped with a sample stage for High Energy Micro Diffraction (HEMD), which allows highly precise positioning of the sample in real and angular space. In addition an Eulerian cradle is available to be mounted for crystallographic work on single crystals. For heavy components, like magnet cryostats, a different sample stage can be mounted in parallel to the HEMD sample stage. It´s able to carry components up to 350 kg. The beam can be focused by compound refractive lenses down to 2 μm x 40 μm at the sample position. For fast experiments with less resolution the setup behind the sample can easily be switched to a flat panel detector placed on the same stage as the point detector with analyzer. The detector to sample distance can be varied during the experiment between 0.5 and 3.5 m. Examples of the latest experiments will be presented and discussed.
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Aug 12
Tuesday

FTIR Spectral Micro-Tomography in Full Color

Speaker: C.J. Hirschmugl, University of Wisconsin-Milwaukee
XSD Presentation
401/A1100 @ 10:00 AM
View Description
The holy grail of chemical imaging is to provide spatially and temporally resolved information about heterogeneous samples on relevant scales. Synchrotron-based Fourier Transform infrared imaging1 combines rapid, non-destructive chemical detection with morphology at the micrometer scale, to provide value added results to standard analytical methods. Hyperspectral cubes of (x,y, z, Abs (l)) are obtained employing spectromicrotomography2, a label free approach, it inherently evaluates a broad array of wide organic materials, with minimal sample preparation and modification. Examples presented here (polymer composites, single cells and colonies of cells) demonstrate the broad applicability of this approach to detect complex chemical information of intact samples.
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Aug 5
Tuesday

The Sirius Project

Speaker: Harry Westfahl, Jr., Brazilian Synchrotron Light Laboratory, Campinas, Brazil
XSD Seminar
401/A1100 @ 11:00 AM
View Description
The Brazilian Synchrotron Light Laboratory has started the construction of Sirius, a 3 GeV and 0.28 nm rad emittance storage ring. In this talk I will present some of the main aspects of this new storage ring and its first and second phase beamlines, as well as the current status of the project.
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Aug 1
Friday

In situ x-ray diffraction applied to the study of metal oxide and carbide catalysts

Speaker: Wenqian Xu
XSD Seminar
Advanced Photon Source, Argonne, IL
401/A1100 @ 11:00 AM
View Description
In situ x-ray diffraction (XRD) is nowadays widely applied in physical science to study material structures under desired conditions. In the field of catalysis, it is of key interest to know how a catalyst functions and how its structure related to its catalytic property. Probing the catalyst with x-ray at its working state is helpful in providing such information. In this talk, two studies are presented. In the first one, a Ni/CeO2 catalyst for ethanol steam reforming (ESR) is investigated with both in situ XRD and in situ infrared spectroscopy. Ethoxyl, acetate, carbonate and hydroxyl species are identified as surface intermediates that appear during the reaction process. The synergy between metallic Ni and the CeO2 support is revealed. The second study is on carburization of molybdenum oxide by temperature-programmed reduction in hydrocarbons. Formation of either the cubic or the hexagonal carbide phase is found to be affected by both concentration and speciation of the hydrocarbons as well as the heating procedures. Close examination of the XRD and the pair distribution function (PDF) profile of the cubic carbide phase shows the presence of stacking faults in its structure.
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Aug 1
Friday

Nanofabrication of Diffractive X-ray Optics for Applications at Synchrotrons and XFELs

Speaker: Christian David, Paul Scherrer Institut, Villigen, Switzerland
XSD Seminar
438/C010 @ 10:00 AM
View Description
I present recent developments in nanolithography to produce diffractive x-ray optics, and experimental results obtained with these devices. For the use at synchrotrons we at PSI have developed a new generation of Fresnel zone plates produced by a line doubling approach. Used in a scanning microscope, these lenses can resolve features down to 9 nm in the soft x-ray range and down to 15 nm in the multi keV range. To improve the efficiency for hard x-rays, a fabrication strategy was developed to produce two stacked zone plate structures on both sides of the support membrane. A diffraction of close to 10% was obtained at 9 keV photon energy for a zone plate with 30 nm zone width. A similar technique can be applied to produce blazed zone plates with diffraction efficiencies of 50% providing 100 nm spot size.

For use at x-ray free-electron laser (XFEL) sources, diffractive optics must be capable of withstanding extreme radiation loads. We show how diffractive optics made of diamond can be used for various applications including nanofocusing, beam-splitting, spectral monitoring and ultrafast time resolved studies
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Jul 16
Wednesday

Reconstructing Diet in Fossil Humans: How Synchrotrons Can Help

Speaker: Callum Ross, University of Chicago
XSD Presentation
431/C010 @ 11:00 AM
View Description
Changes in human diet have had a profound influence on the design (form-function relationships) of the human feeding system. Dental design is not only important because it is sensitive to both changes in the material properties of food and feeding behavior, but also because teeth are well represented in the fossil record. I will review recent work on the evolution of feeding system design in primates, with special emphasis on fossil humans, and discuss the roles of synchrotron-based measurement of enamel micro-structure and finite element modeling of dental form for understanding the evolution of human feeding systems.
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Jul 11
Friday

New Techniques for Probing and Controlling Nonadiabatic Molecular Dynamics

Speaker: Vladimir S. Petrovic, Stanford University, PULSE Institute for Ultrafast Energy Science
XSD Presentation
401/A1100 @ 2:00 PM
View Description
On the molecular level the conversion of energy from one form to another occurs via nonadiabatic interactions that govern the exchange of energy between different degrees of freedom. Often this exchange occurs on fast timescales, which makes time-resolved pump-probe techniques suitable for studying it. In the first part of the talk I will report on using time-resolved dissociative ionization to probe structural changes that result from nonadiabatic interactions. This technique relies on the characterization of the dissociation-formed fragments, their correlations, or their coincidences. I will discuss complementary methods of initiating dissociative ionization via weak-field x-ray absorption or strong-field IR absorption for investigation of nonadiabatic processes that lead to unimolecular isomerizations in small hydrocarbons. In particular, dynamics at conical intersections can be studied and controlled using short-pulse x-ray and intense IR radiation. In addition, I will discuss more recent experiments performed at Linac Coherent Light Source that investigate ultrafast x-ray initiated molecular dynamics. In the second part of the talk I will talk about plans to extend the application of these techniques to more complex multi-electron and aqueous systems. These experiments seek to generate insight relevant for optimizing conditions for diffraction-before-destruction techniques in biologically relevant systems.
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Jul 10
Thursday

Colossal Magneto-resistant Materials: The key role of phase separation

Speaker: M. Baldini, HPSynC Carnegie Institution of Washington
XSD Presentation
401/A1100 @ 11:00 AM
Jul 3
Thursday

New Tools and New Insights Into Bioinorganic Chemistry

Speaker: Simon James, Australia Synchrotron
XSD Presentation
438/C010 @ 2:00 PM
View Description
Transition metals imbibe biology with impressive catalytic flexibility and serve as stabilizing structural foundations for the macromolecules of the cell. Coordination chemistry defines the biological utility of transition metals but remains under studied due to a lack of suitable probes. To be useful, such probes must meet a number of demanding challenges, including minimal preparation requirements, extremely high sensitivity, high spatial resolution, and minimal disturbance to both elemental distribution and chemical speciation. When used alongside protocols which limit preparation artefacts, these requirements are satisfied by the combination of scanning X-ray fluorescence microscopy (sensitivity and spatial resolution) and X-ray Absorption Near Edge Structure (XANES; to determine speciation). In the past such an approach was prohibitively time consuming but recent developments in energy-dispersive detector technology have enabled a step change in efficiency of previously limiting parameters such as sensitivity and speed. These gains have been exploited to develop 2- and 3-dimensional scanning X-ray fluorescence XANES and used to map the native metalloarchitecture throughout intact multi-cellular organisms. The development of these techniques for visualizing the 3-dimensional distribution of coordination sites within intact whole animals promises to provide key insights into cell function and bioinorganic chemistry driving health and disease.
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Jun 17
Tuesday

Resonant Soft X-ray Scattering for Soft Materials

Speaker: Dr. Cheng Wang, Advanced Light Source, Lawrence Berkeley National Laboratory
XSD Presentation
401/E1100 @ 10:00 AM
View Description
To meet the challenge of investigating new and complex materials that are relevant to mesoscale energy science, it is essential to connect microscopic dynamical processes to activated kinetic processes and macroscopic function in diverse soft and hard materials. We need sharper tools in order to discover, understand, and control mesoscale phenomena and architectures. Over the past a few years, we have developed Resonant Soft X-ray Scattering (RSoXS) and constructed the first dedicated resonant soft x-ray scattering beamline at the Advanced Light Source, LBNL. RSoXS combines soft x-ray spectroscopy with x-ray scattering thus offers statistical information for 3D chemical morphology over a large length scale range from nanometers to micrometers. Using RSoXS to characterize multi-length scale soft materials with heterogeous chemical structures, we have demonstrated that soft x-ray scattering is a unique complementary technique to conventional hard x-ray and neutron scattering. Its unique chemical sensitivity, large accessible size scale, molecular bond orientation sensitivity with polarized x-rays and high coherence have shown great potential for chemical/morphological structure characterization for many classes of materials. Some recent development of in situ soft x-ray scattering with in-vacuum sample environment will be discussed. In order to study sciences in naturally occurring conditions, we need to overcome the sample limitations set by the low penetration depth of soft x-rays and requirement of high vacuum. Adapting to the evolving environmental cell designs utilized increasingly in the Electron Microscopy community, customized designed liquid/gas environmental cells will enable soft x-ray scattering experiments on biological, electro-chemical, self-assembly, and hierarchical functional systems in both static and dynamic fashion. Initial RSoXS results of solar fuel membrane assembly/fuel-cell membrane structure in wet cell will be presented.
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May 22
Thursday

The Power and Flexibility of X-Ray Scattering as a Probe of Magnetic Systems: KCuF3 and Fe/Gd Thin Films

Speaker: James C. T. Lee, Advanced Light Source, LBNL
XSD Presentation
431/C010 @ 10:00 AM
View Description
X-ray scattering is an excellent tool for studying both the crystal structure and, via resonant scattering, the electronic structure of the magnetic state. To illustrate the power and flexibility of x-rays as a probe, I will discuss magnetism in orbitally ordered KCuF3 single crystals and Fe/Gd thin films exhibiting perpendicular anisotropy.

Due to its simplicity, KCuF3 is the ideal system of orbital physics, which plays an integral part in many exotic phenomena like colossal magnetoresistance. The basis for nearly all theories of orbital physics Kugel–Khomskii model, being the first to explain the symmetry of orbital and magnetic order in KCuF3. However, no refinement of the Kugel-Khomskii model heretofore could account for other prominent features of KCuF3, such as the disparity of its orbital and spin ordering energy scales. Based on x-ray scattering (done in part at Sector 4ID-D, APS) and Raman scattering experiments, we have found that the missing piece of the puzzle is a direct orbital exchange interaction. This mechanism may play a crucial role in other orbitally active materials. Unlike KCuF3, the magnetic order in Fe/Gd thin films exists over mesoscopic scales. These systems display complex domain structures and phase diagrams. Judiciously made films with large perpendicular anisotropy may show novel domain structures and spin textures. Resonant soft x-ray scattering (RSXS) at the Fe L3 and Gd M5 edges was performed at Beamline 12.0.2.2, ALS, to probe the domain structure with evolving applied magnetic field and sample temperature. Ordered arrays of stripe domains appear well below saturation. As the applied magnetic field increases, a metamagnetic transition occurs and the stripe array smoothly transforms into a hexagonal bubble lattice. The bubble domains may display a skyrmionic spin texture.

Not just limited to single crystals and thin films, RSXS is also an ideal tool for studying lithographically made systems engineered to display exotic magnetism (e.g. nanodot arrays displaying spin ice behavior). The power of RSXS can also be deepened by using x-ray photon correlation spectroscopy to characterize the dynamics of magnetic materials. Such demonstrations of the flexibility and power of x-ray scattering will be made at the new RSXS end station at Sector 29.
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May 21
Wednesday

Electronic Transitions, Coherence, and Hybridization: A Spectroscopic Study of Unusual Electronic Properties in Strongly Correlated Materials

Speaker: Fanny Rodolakis Simoes, University of Illinois-Chicago
XSD Presentation
431/C010 @ 11:00 AM
View Description
Understanding phase transition induced by strong electronic correlations represents one of the major challenges in condensed matter physics. Phenomena presenting great interest both from point of view of basic science and of their potential technological applications, like metal-insulator transitions and high temperature superconductivity, are typical examples of effects determined by collective electronic excitations. On the theoretical side, development of Dynamical Mean Field Theory provided a powerful conceptual approach to interpret these phenomena. On the experimental side, one of the main challenges for the study of strongly correlated materials is the development of techniques giving access to the electronic structure of these systems while tuning external parameters (temperature, pressure, electric field, etc.) across their often complicated thermodynamic phase diagrams.

In this talk I will present an investigation of some of the most remarkable manifestations of strong correlations in materials by using different spectroscopic techniques such as high-resolution X-ray absorption (PFY-XAS) and angular resolved photoemission spectroscopy (ARPES): the metal-insulator transition in the transition metal oxide (V1-xCrx)2O3, the Kondo effect in the heavy fermion compound Ce2RhIn8, and high Tc superconductivity in copper oxide Bi2Sr2CaCu2O8+δ. By shedding the light on their electronic structures, those measurements combined with LDA+DMFT calculation reveal an even more intricate behavior like the inequivalence of temperature, doping and pressure in the vanadium sesquioxide phase diagram, or multiple energy scales in Ce2RhIn8.
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May 20
Tuesday

Correlating Interfacial and Bulk Nanostructure with Performance of Organic Electronic Devices: The Usefulness of Soft X rays

Speaker: Hongping Yan, High-Pressure Collaborative Access Team (HP-CAT), Geophysical Laboratory, Carnegie Institution of Washington
XSD Presentation
431/C010 @ 10:00 AM
View Description
Soft matter systems often consist of multiple components and are naturally or synthetically nanostructured for optimal properties and performance. Near an absorption edge (e.g. carbon 1s), the high energy-dependence of absorption coefficient and index of refraction provides tunable contrast between functional moieties of polymer thin films for improved soft x-ray scattering and reflectivity characterization capability.

In this presentation, the usefulness of resonant soft x-ray reflectivity (R-SoXR) and scattering (R-SoXS) in revealing interfacial width and bulk nanomorphology of organic electronics, including organic solar cells and organic field effect transistors, are demonstrated with corresponding study cases. The morphology characterizations are correlated to device performance for better understanding the impact of processing method on nanomorphology and hence the performance of these organic electronic devices. A practical and accurate method to obtain the complex index of refraction, especially the decrement δ, accross the carbon 1s absorption edge is demonstrated, which is expected to greatly improve the simulation and interpretation of R-SoXR and R-SoXS data.
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Apr 16
Wednesday

Sensors and Systems for Digital Radiography

Speaker: Vivek V. Nagarkar, RMD Inc.
XSD Presentation
401/A1100 @ 1:30 PM
View Description
At RMD we have developed modular digital imaging detectors for applications ranging from hypervelocity projectile tracking and ballistic impact analysis to medical X-ray CT and time-resolved diffraction studies. These systems benefit from recently discovered binary and ternary phase inorganic scintillators and novel ceramic scintillators that demonstrate unprecedented emission efficiencies (70,000 to 100,000 ph/MeV), high densities (5 to 9 g/cc), high effective atomic numbers (Z~50 to 70), and radiate in 450 to 650 nm range with fast decay. These recently discovered scintillators are being fabricated at RMD for use in digital radiography by novel processes like physical vapor deposition (PVD) or laser processing. Our advanced PVD techniques results in the formation of structured scintillators in microcolumnar and/or macrocolumnar format, while our laser processing techniques using solid state laser are capable of forming structured scintillators of arbitrary shapes.

Here we will present novel scintillators fabricated in microcolumnar or pixelated form that minimize the traditional tradeoff between spatial resolution and detector efficiency and are suitable for imaging low (8 keV) to high (450 kVp) energy X-rays and/or thermal neutrons. Performance characteristics of radiographic imaging detectors and systems will also be discussed.
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Mar 27
Thursday

Optimum Performance of the Novel Accelerator for Iterative Phase Retrieval in the Fresnel Region Applied to X-ray Phase Contrast Imaging

Speaker: Nghia Vo, Diamond Light Source
XSD Presentation
431/C010 @ 3:00 PM
View Description
Iterative phase retrieval in the Fresnel region based on Gerchberg-Saxton algorithm suffers from slow convergence and stagnation. Recently, a novel accelerator, named random signed feedback (RSF), was proposed (http://dx.doi.org/10.1063/1.4769046) which shows a superior performance compared with other traditional techniques: hybrid input output (HIO) and conjugate gradient search (CGS). Its feasibility is confirmed by applying on X-ray phase contrast tomographic data, collected at beamline I12 Diamond Light Source, which shows promising results. In this talk, I will present how I investigated the RSF accelerator under various conditions to obtain its optimum performance.
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Mar 27
Thursday

X-ray Diffraction from Perfect Crystals - the 100th Anniversary of the First Calculations by C.G. Darwin

Speaker: Denny Mills, Advanced Photon Source
XSD Presentation
401/A1100 @ 11:00 AM
View Description
In 1914, C. G. Darwin published two papers* that established some of the basic features of x-ray diffraction in perfect crystals. One of those features was near-unity reflectivity over a narrow angular range at the Bragg condition, a phenomenon that is still known as the “Darwin width” of the reflection. The talk will briefly describe his calculational approach to scattering in perfect crystals, impact of those calculations, and other aspects of Darwin’s life and work.

*"The Theory of X-ray Reflexion", by C. G. Darwin, Philosophical Magazine, 27, (1914), p313-333 and “The Theory of X-ray Reflexion Part II”, by C. G. Darwin, Philosophical Magazine, 27, (1914), p675-690.
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Mar 21
Friday

Hybrid Pixel Array Detectors Enabling New Science

Speaker: Clemens Schulze-Briese, Dectris Ltd.
XSD Presentation
401/A1100 @ 2:00 PM
View Description
PILATUS single photon counting Hybrid Pixel Device (HPD) detectors have transformed synchrotron research by enabling new data acquisition modes and even novel experiments. At the same time data quality has improved due to noise-free operation and direct conversion of the X-rays. Millisecond readout times and high-frame rates allow for hitherto unknown speed and efficiency of data acquisition.

At cryogenic temperatures, PILATUS allows to acquire data of optimal quality by collecting high multiplicity data at low dose rate, referred to as dose slicing. Monitoring data quality indicators as a function of frame number reveals the optimal data quality for a given crystal. This overcomes the problem of traditional data collection, where radiation damage may affect data accuracy before a complete data set is collected. In contrast, dose-sliced data collection always enables the exploration of the full diffraction potential of the crystal. The noise-free counting of PILATUS detectors allows the dose per frame to be reduced without loss of data accuracy due to read-out noise. Furthermore, high frame rates enable acquisition of optimally fine f-sliced, high multiplicity data in short time.

In room temperature data collection, the high frame rates featured by PILATUS3 detectors allow for outrunning of radiation damage. Recent experiments demonstrate a systematic increase in the dose tolerance of protein and virus crystals as a function of dose rate. PILATUS3 detectors allow even higher frame rates and further push the boundaries of this successful experimental strategy. Latest results obtained with PILATUS3 reveal a departure from a linear or exponential intensity decay in the diffracting power of protein crystals as a function of absorbed dose. A lag phase observed in these experiments raises the possibility of collecting substantially more data from crystals held at room temperature before a critical intensity decay is reached.

The new EIGER detector series presents a leap in HPD detector technology. Featuring 75 µm pixel size and frame rates up to 3000 Hz in combination with continuous read-out, EIGER detectors will open up new opportunities for advanced dose optimized data acquisition techniques.

HPD detectors with CdTe sensors extend the range of high quantum efficiency to 80 keV. This will allow to fully exploit the potential of new high energy and brightness undulator beamlines at unprecedented signal-to-noise ratios and data acquisition speeds.

An overview of the salient detector properties will be given and illustrated by experimental results in various applications.
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Mar 11
Tuesday

Physics and Chemistry of Vacancy Defects in Graphene Layers: Scanning Tunneling Microscopy and Density Functional Theory Study

Speaker: Maxim Ziatdinov , Tokyo Institute of Technology
XSD Presentation
431/C010 @ 11:00 AM
Mar 6
Thursday

Synthesis of ITO Nanoparticles with Shape Control and their Assembly for Solution-Processed Transparent Electrodes

Speaker: Jonghun Lee, Brown University
XSD Presentation
432/C010 @ 2:30 PM
Feb 10
Monday

Elucidating the Structure-Performance Relationship in Organic Photovoltaics (OPVs) by Grazing Incidence X-Ray Scattering

Speaker: Joseph Strzalka, X-ray Science Division/Time Resolved Research
XSD Presentation
401/A1100 @ 2:00 PM
View Description
Since the introduction of the Bulk Heterojunction (BHJ) architecture in the mid- 90s, organic photovoltaic devices have made steady progress toward improved power conversion efficiency, and are now poised to move from niche products to large scale commercial applications. In the BHJ, the photoactive layer consists of electron donor and acceptor materials in a bicontinuous phase blended on the nanoscale. Grazing incidence x-ray scattering, capable of characterizing thin film nanomorphology of surfaces and interfaces, has emerged as a key technique for investigating OPV materials. The hierarchical variety of lengthscales present in OPV materials requires both grazing incidence small- and wide-angle x-ray scattering, the latter recently enabled by improvements to the GISAXS instrument at 8-ID-E. I will describe grazing-incidence studies at 8-ID-E that have contributed toward unraveling the complex relationship between OPV materials, processing and performance.
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Feb 4
Tuesday

Solving the Phase Diagram of the Model Quantum Magnet SrCu2(BO3)2

Speaker: Sara Haravifard, Argonne National Laboratory & The University of Chicago
XSD Presentation
432/C010 @ 2:00 PM
View Description
Low dimensional quantum magnets provide a framework for exotic phase behavior in new materials, with high temperature superconductivity being the most appreciated example. SrCu2(BO3)2 (SCBO), is a rare example of a quasi two-dimensional quantum magnet for which an exact theoretical solution exists. It serves as an experimental realization of the Shastry-Sutherland model for interacting S=1/2 dimers. The ratio of the intra and inter-dimer exchange interactions in this compound is close to a quantum critical point, where the ground state is predicted to transform from a gapped, non-magnetic singlet state to a gapless long-range ordered antiferromagnetic state as a function of the ratio of the strength of the magnetic interactions. We conducted high resolution neutron scattering measurements on SCBO in its singlet ground state which identified the most prominent features of the spin excitation spectrum, including the presence of one and two triplet excitations and weak dispersion characteristic of sub-leading terms in the spin Hamiltonian. Additionally, we investigated the pressure-driven quantum phase transition in SCBO using synchrotron X-ray diffraction and neutron scattering. In these studies we were able to investigate the evolution of both the magnetic and structural properties of SCBO up to pressures of 6 Gpa, following the development and evolution of long-range magnetic order. Moreover, the resemblance between the spin gap behavior in the Mott insulator SCBO and that associated with high temperature superconductors motivated us to explore the significance of doping on the phase diagram.
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Jan 28
Tuesday

Novel Industrial Ultrafast Lasers and their Applications in Free Electron Lasers and Synchrotrons

Speaker: Yoann A. Zaouter, Amplitude Systemes
XSD Presentation
433/C010 @ 10:00 AM
View Description
he aim of this presentation is to introduce the novel industrial ultrafast laser technologies that are developed at Amplitude Systemes. These lasers benefit from several technological breakthroughs such as direct diode pumping and novel laser architectures, and gain media that allow the laser to operate simultaneously at high energies, average powers and therefore repetition rates. We will also specifically show where they are used in FEL and synchrotron and how they advantageously can replace ageing laser technologies and improve the reliability of photoinjectors, minimize the down times, improve signal to noise ratio of measurements, etc.
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Jan 13
Monday

Probing the Metal-Insulator Transition in Engineered NdNiO3

Speaker: Mary H. Upton, Inelastic X-ray & Nuclear Resonant Scattering (IXN)
XSD Presentation
401/A1100 @ 2:00 PM
View Description
NdNiO3, along with other rare earth nickelates, has been the focus of intense research in the last decade due to its metal-insulator transition (MIT), occurring at ~210 K in NdNiO3. The transition temperature can be tuned (or suppressed) with strain giving rise to the possibility of engineered heterostructures. There are many competing models of the MIT, of which the true nature is not known. It has been suggested that the MIT results from the emergence of a low temperature charge ordered state involving the d electrons. Alternately, it may result from the opening of a charge transfer gap between the Ni d and O p electrons. We report on the effect of epitaxial strain and temperature on d-electrons in NdNiO3 as measured by bulk-sensitive resonant inelastic x-ray scattering.
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Jan 13
Monday

Engineering the Elasticity of Soft Colloidal Materials Through Surface Modification and Shape Anisotropy

Speaker: Lillian C. Hsiao, University of Michigan, Ann Arbor
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Designing complex fluids has always involved the arduous manipulation of system-specific parameters. Recently, we developed a general correlation to predict the flow behavior of a range of soft matter based on their microstructure. By applying the framework of structural rigidity at the macroscale (bridges, buildings, domes) to the microscale, we are able to explain the nonlinear elasticity of colloids flowing at high rates that are typical of industrial processing. In particular, we explore the idea that colloidal gels can be designed with better mechanical properties and stability without resorting to a greater quantity of materials, simply by incorporating particles with different shapes, sizes, and roughness. Biphasic particles with metallic facets have also been proposed to provide extraordinary structural strength due to their interaction anisotropy. We test these ideas by synthesizing monophasic and biphasic colloids of controlled roughness in various ellipsoidal shapes, dispersing the particles in refractive-index matched solvents, and inducing self-assembly and gelation with a measurable and tunable depletion attraction. To quantify their flow properties, rheological measurements are carried out in conjunction with microscopy experiments and direct force measurements using optical tweezers. Our understanding of gel physics and rheology shows that the trial-and-error engineering of viscoelasticity can be mitigated by applying the principle of structural rigidity to material design; for example, engineers can incorporate smaller ellipsoidal particles to increase yield stress without a significant increase in the production cost.
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Jan 10
Friday

Light-X-ray Scattering and Rheology of Soft Matter

Speaker: Yu-Ho Wen, Cornell University
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Soft matter is an important class of molecular materials, typically composed of polymers, colloids, and other mesoscopic constituents. They are indispensible in contemporary technological applications—for example, solid electrolytes in rechargeable lithium batteries and solution-cast thin film in polymer light-emitting diodes (PLEDs). Herein we report on the dynamics and structure of the two advanced materials—nanoparticle salts and conjugated polymers. The nanoparticle salts are created by cofunctionalization of metal oxide nanoparticles with tethered salts and neutral organic ligands, and are shown to exhibit equilibrium, Newtonian flow behaviors. We find that ionic cross-links between the salts can be created/weakened by variations of counterion size and dielectric medium. Scrutiny into the SAXS structure factors and plateau moduli further disclosed that nanoscale interparticle spacing imposed on tethered molecules produces topological constraints analogous to those in entangled polymers, uncovering the molecular origin of a similar plateau modulus shared with polymer-tethered nanoparticles and entangled polymer melts. Time-composition superposition of linear viscoelastic data further indicates stricking dynamical similarities between the two systems. In the second part, we propose a self-consistent formulation for analyzing the dynamic structure factor of aggregate species in conjugated polymer solutions, where a wide size distribution and unknown aggregate morphology, as well as pronounced interferences between translational and interior segmental motions of aggregate clusters have posed stringent challenges for conventional light-scattering analyses. Additionally, in situ rheological and turbidity measurements reveal that an externally imposed flow can result in instant and/or persistent changes in the bulk aggregation state of the precursor solutions.
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Jan 9
Thursday

Hierarchical Semiconductor, Metal and Hybrid Nanostructures and the Study of their Light-Matter Interactions

Speaker: Anna Lee, University of Toronto
XSD Presentation
401/A1100 @ 2:00 PM
View Description
The interdisciplinary work during my Ph.D. and post-doctoral studies (Dept. of Chemistry and Dept. of Electrical Engineering, University of Toronto) explore the optical properties of hierarchical structures composed of nanoscale building blocks ranging from metals to semiconductors and composites, organized through bottom-up design methods.

This talk is comprised of three main research projects for which the common thread is the rational design of nanoscale assembled structures and their interactions with light.

Recent advances in spectrally tunable solution-processed metal nanoparticles have provided unprecedented control over light at the nanoscale. The plasmonic properties of metal nanoparticles have been explored as optical signal enhancers for applications ranging from sensing to nanoelectronics. Specifically, (1) by following the dynamic generation of hot spots in self-assembled chains of gold nanorods (NRs), we have established a direct correlation between ensemble-averaged surface- enhanced Raman scattering (SERS) and extinction properties of these nanoscale chains in a solution state. Experimental results were supported by comprehensive finite-difference time-domain simulations. Building from this, (2) we studied an alternate geometry, namely side-by-side assembled NRs. There is a general misconception that aggregates of metal nanoparticles are more efficient SERS probes than individual nanoparticles, due to the enhancement of the electric field in the interparicle gaps. However, we have shown through theoretical and experimental analyses that this is not the case for side-by-side assembled gold NRs. (3) Progress in colloidal quantum dot photovoltaics offers the potential for low-cost, large-area solar power; however, these devices suffer from poor quantum efficiency in the more weakly-absorbed near infrared portion of the sun’s spectrum. Here, I will talk about a plasmonic-excitonic solar cell that combines two jointly-tuned solution processed infrared materials. We show through experiment and theory that a plasmonic- excitonic design using gold nanoshells with optimized single-particle scattering-to- absorption cross section ratios leads to a strong enhancement in near-field absorption and resultant photocurrent in the performance-limiting near infrared spectral region. The present work offers guidance towards the establishment of “design rules” for the development of colloidal nanoparticle assembled systems for plasmonic sensing applications.
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2013

Nov 21
Thursday

Model-based Fusion Opportunities for Integrated Circuit Imaging

Speaker: Eugene Lavely, BES Systems
XSD Presentation
401/A1100 @ 2:00 PM
View Description
Materials characterization of integrated circuits (IC) and semiconductors is becoming increasingly important for process improvement, manufacturing yield, fault detection, and reliability prediction. However, technology node scaling of CMOS and the corresponding increasingly smaller critical dimensions (CD) strongly challenge non-destructive estimation techniques for chemical and spatial characterization of ICs. Technique sensitivity may decrease with smaller CD due to signal to noise ratio of diagnostic measurements, the intrinsic spatial resolution of the imaging mode and associated optics, and weak interaction cross-sections. Sample positioning and uncertainty is also a major challenge in deep sub-micron imaging. IC characteristics such as layout, chemical composition of interconnects and vias, thickness and composition of diffusion barriers and thin films, doping concentration in transistor wells and substrate, and strain values in dielectrics are of interest for IC validation, provenance assessment, and aging/reliability analysis.

Accurate prediction of reliability as a function of aging is a critical issue for security, defense and commercial use of IC. Various IC degradation mechanisms have been identified such as hot-carrier injection, negative bias temperature instability, and oxide breakdown, all of which degrade transistor performance and eventually leading to catastrophic failure. Further, the embedded metal interconnect stack-up of the IC can be degraded by electromigration. Each of the processes alters the physical properties of the IC differently, and the various imaging modalities will be differentially sensitive to these changes depends on the physics of interaction with the probing field. In principle, physics-based fusion of the imaging techniques offers the possibility of improved detection and resolution of IC structure and alterations. The total collection time and radiation dose to the sample can be reduced if data from the multiple imaging modes are acquired simultaneously as their joint use in model-based estimation effectively increases the experiment aperture, helps mitigate SNR problems, and provides enhanced and non-redundant sample constraints. Data from multi-modes can even be used to improve metadata and sample registration.

In this talk we present X-ray fluorescence (XRF) data collected at APS beamline 2-ID-E, and we show 3D statistical reconstruction results as well. That data shows sensitivity to Copper, Aluminum and Tungsten structures in the IC stack. We discuss challenges such as data registration for consistent tomographic processing of the projection series. We demonstrate XRF sensitivity to thin films in IC, and as an aid to IC process identification. We also present transmission X-ray microscopy (TXM) results for of a portion of an IC die with data collected from beamline X8C (Brookhaven NSLS). Opportunities for model-based fusion (joint inversion) of XRF and TXM data are suggested, and we discuss why statistical reconstruction techniques are needed for estimation. We speculate on the advantages and possibilities of imaging IC in operando, particularly for reliability analysis.
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Nov 20
Wednesday

A New X-Ray Imaging System Based on Chromatic Photon Counting Technology

Speaker: Ronaldo Bellazzini, INFN
XSD Presentation
438/C010 @ 1:00 PM
Nov 18
Monday

Tutorial on Coherence for APS-MBA Lattice

Speaker: Chris Jacobsen, X-ray Science Division
XSD Presentation
402/Gal @ 2:00 PM
Nov 5
Tuesday

The Development of Multilayer-Laue-Lens Based Scanning Microscope for Hard X-ray Nanoprobe at NSLS-II

Speaker: Dr. Hanfei Yan, Brookhaven National Laboratory
XSD Presentation
431/C010 @ 1:30 PM
Oct 17
Thursday

Ion Beam Figuring for Optics

Speaker: Chris Griffith, Kaufman and Robinson Ion Sources
XSD Presentation
431/C010 @ 10:30 AM
Oct 14
Monday

MX Data Acquisition at GM/CA with JBluIce

Speaker: Mark C. Hilgart, X-Ray Science Division, GM/CA
XSD Presentation
401/A1100 @ 2:00 PM
View Description
GM/CA has developed the all-in-one JBluIce-EPICS control system for macromolecular crystallography experiments since 2008. Users interact with a single integrated desktop application to perform data acquisition, locally or remotely, with the aid of semi-automated analysis tools. Unique features have been designed and implemented including vector data collection, diffraction-based crystal centering (rastering), optical centering, high levels of screening and beamline optimization, strategy and analysis tools, and just recently adaptations for high-speed detectors.
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Sep 24
Tuesday

Nanostructured Semiconductor Devices: From Chemical Synthesis to Biomedical Applications

Speaker: Bozhi Tian, The University of Chicago
XSD Presentation
401/A1100 @ 10:00 AM
View Description
Nanowire field-effect transistors (NWFETs) represent diverse and powerful nanostructures for achieving nanoscale bioelectronic interfaces with cells and tissue. NWFETs exhibit exquisite sensitivity in chemical and biological detection and can form strongly coupled electrical interfaces with cellular components. My talk will focus on several biomimetic design considerations towards breaking down the boundary between nonliving and living systems across multiple length scales. I will describe how we experimentally apply these designs in the nanoelectronic systems for building electrically active, minimally invasive interfaces with single cells and synthetic tissue. Specifically, I will discuss a new synthetic approach and novel fabrication method to realize the first semiconductor transistor bioprobe for intracellular measurements from a truly three-dimensional nanoscale device. In addition, recent progress on nanoelectronically addressable synthetic tissue will also be discussed. Finally, I will describe the prospects in future fundamental studies and applications in the life sciences.
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Sep 18
Wednesday

Magnetic X-ray Scattering: Some Deliberate and Some Accidental Observations of X-ray Birefringence

Speaker: Steve Collins
XSD Presentation
401/A1100 @ 11:00 AM
View Description
I will outline some recent experiments in x-ray birefringence, including dynamic imaging of molecular polarization. Birefringence allows very strong coupling to circular polarization. I will show that this is a strong enough effect to exploit as a circular polarimeter. Moreover, birefringence must be taken into account when analysing resonant scattering data in order to avoid misinterpreting circular dichroism in resonant magnetic scattering, for example. In the second part of the talk I will describe some recent experiments to determine the sign of the Dzyaloshinskii-Moriya vector in globally centro-symmetric crystals by exploiting magnetic/resonant quadrupole interference to determine the phase of the magnetic scattering amplitude. I will also take the opportunity to highlight the capabilities of Diamond Beamline I16: Materials & Magnetism.
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Sep 12
Thursday

Advances in Extreme Precision Optics

Speaker: Manas Lakshmipathy, Zygo Corporation
XSD Presentation
401/A1100 @ 2:00 PM
View Description
Zygo's Extreme Precision Optics group has been involved in the development of high end optical components for more than 40 years. Zygo is one of the few companies in the world capable of routinely manufacturing sub-nanometer quality optics over the entire power spectral density for a wide range of materials and geometries. Of particular relevance to the X-ray optics community have been activities associated with program such as the Advanced Ligo project or the prestigious next-generation Micro-Exposure Tool (MET-5) for the CSNE/Sematech consortium in Albany, New York, for next-generation EUV lithography that will be detailed in this presentation.
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Sep 5
Thursday

Effect of Hydrogen-charging on the Structure of Bulk Amorphous Alloy

Speaker: Andrew Chuang, University of Tennessee Knoxville
XSD Presentation
431/C010 @ 11:00 AM
View Description
"Hydrogen in metals" has been a popular topic for material scientists and engineers for many decades. One of the main reasons is the infamous ability of hydrogen to degrade the mechanical properties of most metallic materials. Another reason is the potential of using metal hydrides for hydrogen storage materials. Bulk metallic glasses (BMGs) are emerging engineering materials which exhibit many unique material properties due to its glassy structure. Recently, some of the BMGs have drawn considerable attention for their potential as hydrogen purification and separation membranes. Since properties are strongly affected by the microstructure of the alloys, we used synchrotron xray PDF analyses and Inelastic Neutron Scattering (INS) to investigate the effect of hydrogen on the structure of a hydrogenated BMG. PDF is, by far, the most effective way to systematically describe the structure of an amorphous material, and neutron scattering is among a few techniques that can directly probe hydrogen atoms inside bulk alloys. Combining PDF and INS techniques, the local atomic environment of hydrogen and the corresponding structure changes of BMG are examined comprehensively.
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Sep 5
Thursday

Olympus Laser Scanning Confocal and Opto-Digital Microscope Systems for Industrial and Materials Research Applications

Speaker: Christopher VanderTuuk, Olympus America, Inc.
XSD Presentation
401/A1100 @ 10:00 AM
View Description
Modern industrial QA/QC, FA and R&D labs tend to prefer turn-key laboratory equipment that can provide accurate and repeatable results, often over multiple shifts and with multiple users, and can be certified against a known standard. As industry and manufacturing continues to trend towards the micro and nano levels, the need for high-magnification and high-resolution imaging and measurement is as important as ever. Optical microscope systems fill that need by providing a non-destructive, non-contact way to image and measure very fine detail for a wide variety of materials and applications. Traditional optical microscope and digital imaging systems are still very popular and meet the majority of the needs of the modern lab. However, visual and digital measurements through an optical microscope system are not certified for accuracy and repeatability, and it is often difficult to duplicate observation conditions from one user to the next making it a challenge to obtain consistent images and data. The latest Laser Scanning Confocal and Opto-Digital Microscopes have been designed to address the limitations of traditional optical microscope systems by providing a turn-key digital imaging and measurement solution that is certified for accuracy and repeatability. This talk will discuss new Laser Scanning Confocal and Opto-Digital Microscopes from Olympus, which are designed specifically for industrial and materials research at the micro and nano levels.
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Sep 4
Wednesday

Numerical Design, Fabrication and Theoretical Understanding of Supermirrors for Hard X-ray Telescopes

Speaker: Youwei Yao, Ph.D Student, Nagoya University, Japanv
XSD Presentation
431/C010 @ 10:30 AM
View Description
Hard X-ray telescopes (10-80keV) can achieve high sensitivity in broad energy band with the supermirror coating on the surfaces of mirror shells. Supermirror is a layered structure which consists of up to 100 of layer pairs of two materials, and can reflect hard X-rays by means of the Bragg reflection. When the thickness of each layer changes gradually from the top to the bottom, the Bragg reflection can be satisfied in a broad energy band. Therefore, the thickness distribution of a supermirror determines the response of the hard X-ray telescopes (effective area and its energy/grazing angle dependence). This presentation demonstrates the numerical design methods, fabrication and theoretical understanding of supermirrors for hard X-ray telescopes.

The first part of the presentation is the numerical design and fabrication of supermirrors for specific purposes. In previous works, all the design methods were based on empirical rules to maximize integrate reflectivity within target energy bandwidth. However, the oscillation of reflectivity profile (ripple) was relatively large (~50%). Although the ripples were considered to be smoothed out by accumulating the reflection of many mirror shells with different grazing angles, the residual complex structures still could be found in the telescope response. Such ripples in the response reduce the detection limit of spectral structure, such as cyclotron absorption features from pulsars. In order to solve this problem, we consider making reflectivity profile of each mirror shell as smooth as possible. Based on the understanding of supermirrors, a numerical design method has been developed. Starting from optimized layered structure by previous design method, the thickness of each layer is tuned to get a target response profile. A merit function is established to evaluate the difference between the target and the designed response.

After enough iteration, the optimization algorithm can reduce the ripples less than 0.2% or so. By adding random errors to individual layer thicknesses, it is possible to derive necessary thickness accuracy (~ 0.02nm) of the multilayer fabrication system. In order to prove the feasibility of numerical design, two Pt/C supermirrors are designed for broad and flat angular (1.0-1.5deg, at 8.05keV) and energy (10-50keV, at 0.28deg) response. They are fabricated on float glass substrates by our DC sputtering system. X-ray reflectivity profiles of these samples are measured against grazing angles and X-ray energies. Obtained energy response demonstrates the ripple is as small as designed, which also confirms the fabrication accuracy of our system is high enough to achieve the target profile. Moreover a possible thickness distribution of the fabricated supermirror is reconstructed by tuning designed structure with the obtained response as the target profile.

The second part of the presentation is a theoretical study. The wave equation of X-ray propagation in the layered structure has been solved based on the understanding of the E-M wave theory. By examining the emerging amplitude from the top boundary, the X-ray reflectivity is successfully given for the block structure supermirror. It is also confirmed in these equations that the reflectivity profile against X-ray energy is optimized if the empirical design rules for InFOCμS and HXT of ASTRO-H are satisfied. Moreover, the theoretical work has been further developed to design a multilayer structure with response profile of suppressed side lobes.

Present work provides new approach to design and fabricate designated supermirrors not only for X-ray telescopes but also ground-based experiments.
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Aug 29
Thursday

Argonne Advances in Detectors

Speaker: Marcel Demarteau, Argonne National Laboratory
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Instrumentation is the enabler of science. Today, more than ever, there are tremendous opportunities for development of new detectors that could be transformational for science. A perspective from the field of particle physics will be presented.
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Aug 27
Tuesday

Hybrid CMOS Sensor with Multi-Frame Storage for Ultra - Fast X-Ray Imaging

Speaker: John Porter, Sandia National Laboratories
XSD Presentation
401/A1100 @ 11:00 AM
View Description
We have developed a large-aperture sensor to record multiple x-ray images with integration times as short as 1 nanosecond and interframe times as short as 2 nanoseconds. This camera was designed to record transient x-ray images of high-energy-density science experiments on the Z Machine at Sandia National Laboratories. In these experiments, typically lasting for only a few billionths of a second, a 26-millon-ampere 80-trillion-watt electrical pulse is used to quickly heat and compress materials to high temperatures and pressures. The sensor consists of a silicon photo-detector array directly bonded to a CMOS readout integrated circuit (ROIC). Both the silicon photo-detector array and the CMOS ROIC are fabricated at Sandia’s Mesa Fabrication 0.35um technology node. The 1024x448 pixel photo-detector array has a 25 micron pitch with nearly 100% fill factor, an active area of 25.6mm x 11.2mm, is sensitive to x-rays up to approximately 10 keV in energy with high efficiency, and has subnanosecond temporal response. The corresponding 1024x448 pixel ROIC incorporates a global shutter with adjustable integration and interframe timing and 2-frame in-pixel analog storage with a maximum of nearly 3 million electrons per frame. We are well along in designing next-generation cameras with 4-frames per pixel, increased integration and interframe timing flexibility that will enable interlaced image capture, and that use a variety of photo-detector arrays that have optimized sensitivity to higher energy x-rays, soft x-rays, visible light, or low energy electrons.
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Aug 22
Thursday

Time-Delayed Beam Splitting with Energy Separation of X-ray Channels

Speaker: Yuriy Stetsko
XSD Presentation
401/B3100 @ 2:00 PM
View Description
Efficiency is a key point of any x-ray optics. Especially, it’s important in the x-ray split-delay optics for the x-ray photon correlation spectroscopy where the complex nanoscale dynamics in condensed matter with low intense scattering properties is studied. Traditional x-ray split-delay optics deals with an equal intensity separation of the x-ray free electron laser or synchrotron radiation beam/pulse of some specific energy between the reference and delayed beams/pulses. This equal intensity separation demands use of a single crystal splitter and mixer of an ultra small thickness, of about 10 micrometers. Alternatively, we introduce a time-delayed beam splitting method based on the energy separation of x-ray beams. The realization of the reference and delayed beam channels with different individual energies considerably increases efficiency of x-ray split-delay optics, for about four times. It also allows to deal with much thicker, about several tens – one hundred micrometers, splitter and mixer crystals, making easier the crystal manufacturing.

This method is implemented and theoretically substantiated on an example of an x-ray optical scheme similar to that of the classical Michelson interferometer. The splitter uses Bragg-case diffraction from a diamond crystal. Another two diamond crystals are used as back-reflectors. After back reflection of the beams, the splitter works as a mixer. For energy separation of the beams the back-reflectors are set at slightly different temperatures. The small angular deviations from the exact backscattering, for about 10 microradians, provide a high simultaneous beam reflection and transmission on the splitter and mixer for each of beam channels. Due to a minimal number (three) of the optical elements, the split-delay line is simple to operate. Specifically, the time delay in this scheme is realized by translation of only one back reflecting crystal. It makes the scheme unique in terms of the intensity, angular and spatial stability of the delayed beam channel in contrast to the existing x-ray split-delay schemes, where the synchronization of the translations of two crystals is a key technical issue. In addition, due to the high transparency of diamond crystals, the split-delay line can be used in a beam sharing mode at x-ray free-electron laser facilities.
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Aug 22
Thursday

High Energy X-ray Diffraction Microscopy: Direct Observations of 3D Materials Response

Speaker: Jon Lind, Carnegie Mellon University
XSD Presentation
431/C010 @ 11:00 AM
View Description
The ability to predict a material's performance while being subject to complex thermo-mechanical processing is of great importance for material design and implementation in the real world. A material's behavior and performance has been shown to depend on its underlying microstructure. Recent advances in x-ray-based characterization of bulk microstructures while in service has lead to validation and constraints of models used for predictive responses. Specifically the use of Near-Field High Energy X-ray Diffraction Microscopy (nf-HEDM) with Forward Modeling Method (FMM) to obtain spatially-resolved microstructures and microtextures has been a break-through in fully characterizing bulk metals in-situ. New advanced data processing methods have been applied to nf-HEDM diffraction images to assist in fidelity of microstructure reconstructions returned via the FMM. Here we present the development and results of one study of pure zirconium as it is subjected to several states of uni-axial loading. The local feature tracking, including tensile twin nucleation and void formation, as well as global evolution is discussed.
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Aug 21
Wednesday

Harnessing the Power of High Resolution Synchrotron Powder Diffraction for Materials Discovery in Solid State Chemistry

Speaker: Matthew Suchomel, XSD-Structural Science Group
XSD Presentation
401/A1100 @ 2:00 PM
View Description
Structural characterization is a critical driver of new materials innovation, providing important insights into properties and performance, which in turn accelerates the next breakthrough discovery. Powder diffraction is one of the key tools for structural characterization, used early and often in materials science, solid-state chemistry and condensed matter physics; not only as guide of synthetic exploration, but also to obtain an understanding of structure - property connections under both ambient and a wide range of in-situ operating conditions. This presentation will describe recent research exploiting the high-resolution synchrotron powder diffraction beamline 11-BM at the APS. This state of the art probe enables diffraction experiments under ambient and in-situ conditions with exceptional resolution and fidelity. Particular focus will be given to recent non-ambient methods and advances illustrating multi-probe characterization methods combining synchrotron powder diffraction and other cutting edge techniques (e.g. neutron scattering, NMR). Examples will be presented to spotlight the evolving suite of APS in-situ sample environments developed that provide the structural details required for an understanding of the novel magnetic, transport, optical, and electrochemical properties in inorganic materials of interest to today's solid-state community. A short overview of the unique and highly successful remote access program will also be presented.
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Aug 20
Tuesday

Porous Monolithic Electrode: Synthesis and Applications

Speaker: Joji Hasegawa, Dept. of Energy & Hydrocarbon Chemistry, Kyoto University
XSD Presentation
433/C010 @ 11:00 AM
View Description
Electrode materials have been extensively studied due to growing demands for energy storage. Recently, it is revealed that the conventional composite electrodes, which are prepared from the mixture (slurry) of active materials, conductive agent, and binders, cause major issues, such as degradation of performance due to the decomposition of polymer binders.

This presentation demonstrates “monolithic electrodes” which are characterized as binder-free bulk materials. For practical use, porous structures in monolithic electrodes play a crucial role in increasing the reactive surface area and shortening the ionic and electric diffusion pathways. The synthesis of various porous monolithic electrodes via the sol–gel method and their applications will be presented.
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Aug 19
Monday

Fast Fourier Transform-based Micromechanical Modeling of Polycrystals with Direct Input from 3-D Microstructural Images

Speaker: Dr. Ricardo Lebensohn, Los Alamos National Laboratory
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Emerging characterization methods in experimental mechanics pose a challenge to modelers to devise efficient formulations that permit interpretation and exploitation of the massive amount of data generated by these novel methods. In this talk we report recent advances in Fast Fourier Transform-based methods, which can efficiently use the voxelized microstructural images of heterogeneous materials as input to predict their micromechanical and effective response. The focus of this presentation is on plastically deforming polycrystalline materials. New formulations and applications for different deformation regimes (visco-plasticity, elasto-plasticity, dilatational plasticity, non-local plasticity), some of them with direct input and validation from 3-D characterization methods, will be discussed.
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Aug 15
Thursday

DFT Simulations of Phase Change Materials: Insights to Ultra-fast Amorphous-to-Crystalline Transition

Speaker: Jaakko Akola, Tampere University of Technology
XSD Presentation
431/C010 @ 3:00 PM
View Description
Phase change materials (PCM) are chalcogenide alloys and they function in commercial rewriteable optical disks (DVDs, Blu-ray Disc) and nonvolatile computer memory (PC-RAM) because the amorphous-crystalline transition is rapid, reversible, and accompanied by changes in the optical and electrical properties. The amorphous structures of PCMs are difficult to determine, and the nature of the ultra-fast crystallization mechanism remains the subject of much study and speculation [1]. We have performed several DFT investigations of amorphous and crystalline forms of these materials, and most recently, we have performed two large scale density functional simulations (several hundred atoms over hundreds of picoseconds) of the crystallization process itself in the prototype "nucleation dominated" phase change material Ge2Sb2Te5 (GST-225) and can provide details of the changes in order as crystallization proceeds. This work has lead us to new fields of disordered, glassy materials, and I shall briefly mention our latest achievements for novel CaO-Al2O3 glasses where experiments (x-ray and neutron diffraction, EXAFS) and DFT simulations support each other.
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Aug 13
Tuesday

Tracking and Controlling the Dissociative and Excited Bound Motion in Diatomic Molecules with Ultrashort Laser and XUV Pulses

Speaker: Uwe Thumm, Kansas State University
XSD Presentation
401/A1100 @ 3:00 PM
View Description
Rapid ionization of diatomic molecules in short intense pulses of electromagnetic radiation generates molecular ions that either dissociate immediately or remain in bound excited states. These excited states can be represented in terms of adiabatic molecular potential surfaces that support the ro-vibrational nuclear motion in the molecular ion. Both, dissociative and bound nuclear motion can be destructively imaged (with a time resolution of a few femtoseconds) with a second, delayed pulse, by recording nuclear kinetic-energy-release (KER) spectra as a function of the time delay between the two pulses. In this talk I will discuss various aspects of such pump-probe studies, starting with the dissociative ionization of the simplest molecule, H2, and illustrate how the ro-vibrational dynamics in H2+ can be controlled [1] and revealed in measurable delay-dependent KER spectra. In particular, I will discuss how quantum-beat spectroscopy, i.e., the harmonic time-series analysis o! f delay-dependent KER spectra, allows the reconstruction of (external-field-dressed!) molecular potential curves and holds promise for the full reconstruction of vibrational nuclear wave packets (up to an overall phase) [2,3]. In the second part of this talk I will move on to heavier diatomic molecules, where ionization by an ultra-short pump pulse tends to populate several intermediate excited electronic states of the molecular ion. By comparing characteristic features of simulated KER spectra (vibrational periods, wave packet revivals, quantum beats, etc.) that result from the nuclear motion on individual adiabatic potential curves of the molecular ion with measured KER spectra, we developed a scheme for identifying intermediate ionic states that are relevant for the dissociation process. I will review numerical examples for this simulation-aided interpretation of measured KER spectra for N2, O2, and CO molecules for pump-probe experiments with both IR laser [4,5] and Fr! ee-Electron-Laser XUV pulses [6]. I plan to conclude with a brief discussion of the dissociation dynamics of noble gas dimers in two-color infrared intense laser fields for which our calculations predict a striking “delay gap” in the KER spectra. This gap originates in a frustrated dissociation mechanism and was recently measured for Ar2 [7]. Comparing pump-probe-pulse-delay dependent KER spectra for noble gas dimers of increasing mass, reveals increasingly prominent i) fine-structure effects in and ii) classical aspects of the nuclear vibrational motion [8].

[1] T. Niederhausen, U. Thumm, and F. Martin, in, J. Phys. B: At. Mol. Opt. Phys. 45, 105602 (2012).
[2] B. Feuerstein, T. Ergler, A. Rudenko, K. Zrost, C.D. Schröder, R. Moshammer, J. Ullrich, T. Niederhausen, and U. Thumm, Phys. Rev. Lett. 99, 153002 (2007).
[3] U. Thumm, T. Niederhausen, and B. Feuerstein, Phys. Rev. A 77, 063401 (2008).
[4] S. De, M. Magrakvelidze, I. Bocharova, D. Ray, W. Cao, I. Znakovskaya, H. Li, Z. Wang, G. Laurent, U. Thumm, M. F. Kling, I. V. Litvinyuk, I. Ben-Itzhak, and C. L. Cocke, Phys. Rev. A 84, 043410 (2011).
[5] M. Magrakvelidze, C.M. Aikens, and U. Thumm, Phys. Rev. A 86, 023402 (2012).
[6] Magrakvelidze, O. Herrwerth, Y.H. Jiang, A. Rudenko, M. Kurka, L. Foucar, K.U. Kühnel, M. Kübel, Nora G. Johnson, C.D. Schröter, S. Düsterer, R. Treusch, M. Lezius, C.L. Cocke, I. Ben-Itzhak, R. Moshammer, J. Ullrich, M. F. Kling, and U. Thumm, Phys. Rev. A 86, 013415 (2012).
[7] J. Wu, M. Magrakvelidze, A. Vredenborg, L. Ph. H. Schmidt, T. Jahn! ke, A. Czasch, R. Dörner, and U. Thumm, Phys. Rev. Lett. 110, 033004 (2013).
[8] M. Magrakvelidze and U. Thumm, Phys. Rev. A 88, 013413 (2013).
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Aug 13
Tuesday

Thales SESO New Products and Innovations

Speaker: Nicolas Douradou, Thales Group
XSD Presentation
431/C010 @ 2:00 PM
View Description
2:00 - 3:00 p.m. Talk / 3:00 - 4:00 p.m. Q&A

During the previous years, Thales SESO invested a lot in R&D and new equipment to come up with even better performances, some innovations and a brand new patented product.

The presentation will be focused on the following points:
  • Overview of Thales SESO
  • The X-Ray activity at Thales SESO
  • Recent innovations on benders
  • Recent computer controlled polishing machine acquisitions
  • New extra-large interferometric bench
  • New coating capabilities
  • New generation of our patented bimorph mirror

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Aug 13
Tuesday

High Speed X-Ray Imaging and Spectroscopy from 50 eV to 30 keV for Synchrotron Experiments

Speaker: Lothar Strüder and Heike Soltau, PNSensor GmbH, München, Germany and University of Siegen, Siegen, Germany
XSD Presentation
401/A1100 @ 1:00 PM
View Description
Originating from spaceborne applications as focal plane imagers in X-ray astronomy missions, pnCCDs have been used in many light source experiments in basic and applied science. They have been installed at FLASH, at LCLS, and at SACLA as array detectors, as well as for spectroscopic measurements. They are routinely used at the synchrotrons at ESRF, BESSY, and ANKA. The concept and the properties of pnCCDs will be shown in detail, as well as the ongoing developments to improve dynamic range, spatial resolution, and readout speed beyond 200 frames per second for a 1024 x 1024 pixel device. The low energy performance from 30 eV to 2 keV will be highlighted, as well as the high energy performance from 15 keV up to 30 keV. Special emphasis will be given on the quantum efficiency at the two extreme ends of the energy spectrum. Examples from various scientific fields including atomic physics, solid state physics, biology, and crystallography from experiments at FELs and synchrotrons will be presented. High spatial resolution in the µm range will be demonstrated, as well as high energy resolution, high count rate capabilities, and high dynamic range. Finally the physical limitations of the measurement precision will be discussed. The presentation will also include experimental results from Silicon drift detectors as large area spectrometers and recent results with DePFET active pixel sensors as a new generation of spectroscopic imagers.
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Aug 13
Tuesday

Developing Detectors for FELs

Speaker: Dr. Gabriella Carini, SLAC National Accelerator Laboratory
XSD Presentation
401/A1100 @ 11:00 AM
View Description
The talk will focus on detectors for FELs with particular emphasis on Pixel Array Detectors. The genesis of in-house developed detectors typically starts with identifying an application in need of a camera not already available. The implementation of new ideas produces a prototype detector, which is then tested and characterized to verify its performance. After this concept validation, full cameras have to be designed, manufactured and tested. The development is completed by characterization and optimization in actual experimental conditions. Concepts, development and validation with x-rays will be presented from the perspective of my experience at LCLS.
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Aug 12
Monday

Transparent Dense Polycrystalline Ceramics for Photonics Applications Synthesized by Direct Crystallization from a Glassy Precursor

Speaker: Mathieu Allix, CEMHTI, CNRS Orléans, France
XSD Presentation
433/C010 @ 2:00 PM
View Description
Transparent polycrystalline ceramics are an emerging class of photonic quality materials competing with single crystal technology for a diverse range of applications including high-energy lasers, scintillating devices, optical lenses, and transparent armor. Polycrystalline ceramics offer several advantages, particularly in the fabrication of complex shapes and large-scale industrial production, and enable greater and more homogenous doping of optically active ions than is possible in single crystals. A limited number of either cubic or nanocrystalline transparent polycrystalline ceramics are known, but require complex and time-consuming synthetic approaches. Our recent work demonstrates the possibility to obtain for the first time fully dense transparent polycrystalline ceramics by simple direct and complete crystallization from glass. This is demonstrated for the previously unreported composition, BaAl4O7, which exhibits two orthorhombic polymorphs with micrometer grain size, both optically transparent in the visible range. The crystallographic structures of these materials have been determined ab initio from powder diffraction. From these structural models, the refractive index components (nx, ny and nz) have been calculated, giving access to the birefringence. The transparency of these materials will be discussed from these results and the microstructures observed. Lastly, the same innovative synthetic route has been applied to new strontium aluminosilicate compositions, evidencing new and cost-effective solid solutions elaborated as highly transparent polycrystalline ceramics.
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Aug 2
Friday

From the Discovery to the Control of THz Spin Currents: Towards Ultrafast Spintronics

Speaker: M. Battiato, Uppsala University
XSD Presentation
401/B4100 @ 2:00 PM
View Description
The origin of the ultrafast demagnetization has been a mystery for a long time. Recently we have proposed an approach based on spin dependent electron diffusion [1-2]. It was predicted [1-2] that spin bunches with velocities higher than the Fermi velocity can be launched from a ferromagnetic material and can be used to strongly manipulate the magnetization of distant layers. Several independent experimental results have confirmed the presence of strong THz spin currents. Our newest experimental findings have shown that: 1) spin unpolarized electrons superdiffusing into a ferromagnetic layer can trigger ultrafast demagnetization [3], 2) spin transport can be used to create an ultrafast increase of magnetization [4], and 3) superdiffusive spin currents can be tailored by appropriate choice of materials and used to produce broadband THz emission via the inverse spin Hall effect [5]. The impact of these new discoveries goes beyond the field of ultrafast magnetization dynamics. It shows how spin information can be, not only manipulated, but also most importantly transported at unprecedented speeds. This new discovery lays the basis for THz spintronics.

[1] M. Battiato, K. Carva, P.M. Oppeneer, Phys Rev. Lett. 105, 027203 (2010).
[2] M. Battiato, K. Carva, P.M. Oppeneer, Phys Rev. B 86, 024404 (2012).
[3] A. Eschenlohr, et al., Nature Mater. 12, 332 (2013).
[4] D. Rudolf, et al., Nature Comm. 3, 1037 (2012).
[5] T. Kampfrath, et al., Nature Nanotechnol. 8, 256 (2013).
[ Hide ]
Jul 30
Tuesday

Live-cell X-ray Phase-contrast Microtomography of Gastrulation/neurulation in Xenopus Laevis

Speaker: Dr. Julian Moosmann, Karlsruhe Institute of Technology (KIT), Laboratory for Applications of Synchrotron Radiation (LAS)
XSD Presentation
401/B3100 @ 4:00 PM
View Description
We report on recent results in applying XPCµT to time-lapse series of Xenopus gastrulation. We discuss dose in terms of heat load and radiolysis of water. Based on single-distance phase retrieval, 3D reconstruction, segmentation, and (differential) optical flow, analyses of major gastrulation movements, differential tissue motion and mechanisms of tissue propulsion (convergent extension, active crawl on a substrate tissue), differential cell motion (shear, push, pull), fluid redistribution in the developing embryo, and the emergence of an as of yet unknown morphological structure are presented. We also discuss intricacies of data pre-processing and the biological part of the sample preparation.
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Jul 30
Tuesday

High-resolution Phase Retrieval in X-ray Microtomography and Developmental Biology

Speaker: Dr. Ralf Hofmann, Karlsruhe Institute of Technology (KIT), Laboratory for Applications of Synchrotron Radiation (LAS)
XSD Presentation
401/B3100 @ 3:00 PM
View Description
For single-distance free-space propagation after object transmission, we discuss an approximate scaling symmetry of Fresnel theory which becomes exact in the limit of vanishing exit phase variation. It is shown by numerical simulation that scaling symmetry, albeit explicitly broken, is not dynamically broken for a large range of upscaling. Thanks to this property a highly efficient nonperturbative quasiparticle approach to the high-resolution retrieval of sizable phase variations is facilitated. Under a phase-attenuation duality assumption a generalization of this quasiparticle description is possible, and we show how the critical behavior under phase upscaling smoothens as compared to the pure-phase case. We present examples from X-ray investigations of the African Clawed Frog (Xenopus Laevis).
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Jul 29
Monday

Collective Excitations of Sr2IrO4 with Strong Relativistic Spin-orbit Coupling Revealed by Resonant Inelastic X-ray Scattering

Speaker: Jung Ho Kim, IXN
XSD Presentation
401/A1100 @ 2:00 PM
Jul 25
Thursday

Magnetic Smart Materials (MS) Applied to X-ray Optics

Speaker: Melville Ulmer, Northwestern University
XSD Presentation
438/C010 @ 11:00 AM
View Description
MSMs can be used to generate strong stresses when a magnetic field is imposed. The stresses can, in principle, be used to actively deform an optic. The current research is supported by NASA with the goal of developing technology capable of replacing classical grinding and polishing to produce [affordable] X-ray telescopes with point spread functions on the order of 1-10 micro-radians. I will describe potential advantages over piezeo which include simplicity, as rapid as you need (MHz) response times, and the potential to remove mid-frequency ripple from glass substrates.
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Jul 24
Wednesday

Ray-Tracing Simulations for Synchrotron Beamline Optics

Speaker: Manuel Sanchez del Rio, ESRF
XSD Seminar
401/A1100 @ 11:00 AM
View Description
The challenging in-place ESRF Upgrade Program foresees the reconstruction of about one third of the beamlines. The new beamlines will be very long (more than 100 m) allowing the routine use of micro- and nano-beams. This requires a very high demagnification of the ESRF source, which makes beamline optics design a fundamental step in the future availability of bright and small beam. In the design of these beamlines an intense use of computer tools for x-ray optics is necessary. Ray-tracing has demonstrated to be a very reliable tool for designing and optimizing synchrotron beamlines. A substantial effort has been invested in modernizing the SHADOW package and facilitating its use. Some examples of recent simulations for the upgrade beamlines will be presented. New developments include simulations for refractive optics (CRL and transfocators), bent crystals, and the complementary use of ray-tracing with wave-optics propagation for studying partial coherence. In parallel, an ambitious project for the upgrade and integration of existing software and development of a new toolbox has started.
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Jul 8
Monday

Controlling Magnetic Interactions: Antiferromagnetic to Ferromagnetic Order

Speaker: Jong-Woo Kim, X-Ray Science Division
XSD Presentation
401/A1100 @ 2:00 PM
View Description
Switching a material from antiferromagnetic (AFM) to ferromagnetic (FM) order is the maximum change of macroscopic magnetism that one can generate. Several systems display intrinsic competition between these types of order, thus enabling control of the state via external conditions such as electric field, pressure, strain, temperature, etc. This talk will focus on two systems that exhibit an AFM to FM transition, and will discuss the underlying physics driving the competitive nature of the coupling. The magnetoelectric EuTiO3 (ETO) changes its magnetic order from AFM to FM through phonon softening induced by biaxial strain. With an appropriate strain state, the energy difference between the two interactions gets small so that the magnetic state can be altered by an external electric field. By compressively straining the ETO film, the antiferromagnetic order becomes frustrated with the application of an electric field above 1.8 kV/cm. Inter-metallic FeRh films have attracted growing interest in the last decade because its potential application in heat-assisted magnetic recording. This material exhibits a temperature- or field-induced first-order magnetic transition from AFM order to FM order above the room temperature with structural and electronic transitions. I present the magnetic behavior of Rh 4d states through the transition using x-ray resonant magnetic scattering at the Rh L2 edge concurrently with the structural evolution by x-ray diffraction. The structural transition measures a lower temperature than the Rh ferromagnetic transition. This confirms that the structural transition is driven by a magnetically frustrated state due to the onset of Rh 4d magnetic moments.
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Jul 1
Monday

Nuclear and Electronic Dynamics Triggered by Photoionization

Speaker: Dr. Robin Santra, DESY and University of Hamburg
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Extreme ultraviolet light can ionize the valence shell of molecular systems and produce molecular cations in their ground or excited electronic states, which usually undergo ultrafast electronic and nuclear dynamics. The time-resolved exploration of the dynamics of valence-ionized molecules and clusters has been gaining momentum with the advent of ultrafast XUV light sources based on free-electron lasers, such as FLASH in Hamburg. In this talk, I will first provide an introduction to some of the basic theoretical concepts (adiabatic and diabatic representations) and useful computational approaches (wave-packet and trajectory methods). I will then discuss specific applications:

1) An investigation of the nonadiabatic dynamics of the acetylene cation [1,2], where the first excited state drives the molecule from the linear acetylene structure to a trans-bent structure. Through a conical intersection, the acetylene cation can relax back to the ground state of either acetylene or vinylidene.
2) The coupled nuclear-electronic dynamics of protonated water clusters H+(H2O)n upon photoioization [3,4]. In these systems, the hydrogen bond network reacts, on an ultrafast time scale, to the hole created by photoionization. Generally, the dynamics of the excess proton and the hole are strongly correlated and are connected by strong nonadiabatic effects.

[1] M. Madjet, O. Vendrell, and R. Santra, Phys. Rev. Lett. 107, 263002 (2011).
[2] M. E. Madjet, Z. Li, and O. Vendrell, J. Chem. Phys. 138, 094311 (2013).
[3] Z. Li, M. E. Madjet, O. Vendrell, and R. Santra, Phys. Rev. Lett. 110, 038302 (2013).
[4] Z. Li, M. E. Madjet, and O. Vendrell, J. Chem. Phys. 138, 094313 (2013).
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Jun 27
Thursday

PDF Data Analysis Including Demonstration of New Version of My Program RAD and PDF Data Guided Modeling in Particular Reverse Monte Carlo Simulations

Speaker: Professor Valeri Petkov, Central Michigan University
XSD Presentation
433/C010 @ 10:00 AM
View Description
Analysis of XRD data into atomic PDFs will be demonstrated using RAD software. Using PDF data for crystalline lattices constrained modeling (PDFgui software) and crystallography not constrained modeling (DISCUS and reverse Monte Carlo) will also be demonstrated.
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Jun 26
Wednesday

Imaging Electronic Quantum Motion with Light

Speaker: Dr. Robin Santra, DESY and University of Hamburg
XSD Presentation
401/A1100 @ 11:00 AM
View Description
After a brief description of the Center for Free-Electron Science, I will discuss the problem of using ultrafast x rays for imaging the time evolution of nonstationary electronic systems. The practical importance of electronically elastic x-ray scattering from materials derives from the fact that for an electronically stationary sample, the x-ray scattering pattern is related to the electron density distribution in the sample. With the advent of ultrafast x-ray sources, it is natural to envision viewing the motion of electrons using time-resolved x-ray scattering. It is tempting to assume that the x-ray scattering pattern that would be observed can be understood through the x-ray scattering theory for electronically stationary targets. This approach would suggest that time-resolved x-ray scattering with a sufficiently short x-ray pulse probes the instantaneous electron density in the sample. In this talk, I will show that, in general, this expectation is not only quantitatively, but also qualitatively incorrect [1,2]. I will close by proposing a possible way to image the instantaneous electron density of electronic wave packets via ultrafast x-ray phase contrast imaging [3]. I will show that inelastic scattering processes, which plague ultrafast scattering in the far-field regime, do not contribute in ultrafast x-ray phase contrast imaging as a consequence of an interference effect.

[1] G. Dixit, O. Vendrell, and R. Santra, Imaging electronic quantum motion with light, Proceedings of the National Academy of Sciences of the United States of America 109, 11636 (2012).
[2] G. Dixit and R. Santra, Role of electron-electron interference in ultrafast time-resolved imaging of electronic wavepackets, Journal of Chemical Physics 138, 134311 (2013).
[3] G. Dixit, J. M. Slowik, and R. Santra, Proposed imaging of the ultrafast electronic motion
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Jun 25
Tuesday

Fundamentals and New Developments of PDF Technique using Resonant High-energy XRD and Its Application in Catalytic Nanoparticle Studies

Speaker: Professor Valeri Petkov, Central Michigan University
XSD Presentation
401/A1100 @ 2:00 PM
View Description
The very basics of the atomic PDF technique will be discussed from a practical point of view. Also, resonant high-energy XRD coupled to atomic PDFs analysis will be introduced and illustrated with two examples of nanocatalysts studies.
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Jun 21
Friday

Big Data at the SNS

Speaker: Thomas Proffen, Spallation Neutron Source
XSD Presentation
433/C010 @ 11:00 AM
Jun 17
Monday

Synthesis and Structural Characterization of Porous Metal Phosphonates

Speaker: Tiffany L. Kinnibrugh, Texas A&M University
XSD Presentation
433/C010 @ 11:00 AM
View Description
This presentation will focus on the challenge of developing porous metal arylphosphonates with both high crystallinity and functional porosity. Metal phosphonates are an extensive class of materials based upon extended inorganic-organic architectures such as chains, layers and three-dimensional networks. Metal phosphonates generally favor extended inorganic architectures leading to pillared materials with no porosity. We found that the use of template molecules, type of ligand and choice of metal ions could be used to deviate from the pillared structure. Two types of materials and their structure-property relationships will be presented.

For a zinc phosphonate, a layered structure was converted into a three-dimensional framework by using small template molecules in the solvothermal reaction. The compound exhibited reversible dehydration behavior. The change in the framework structure and guest positions was monitored during this process by in situ X-ray diffraction and solid state NMR.

Porous aluminum phosphonates were synthesized; however, the polycrystalline nature of the products can hinder the investigation of their structure-property relationships. These materials exhibited reversible dehydration behavior, which had a dramatic influence on permanent porosity of the material. The stability of the dehydrated phase was found to be the result of the geometry of the aluminum atom, which in some cases has coordinatively unsaturated metal sites.
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Jun 11
Tuesday

MicroXAM Product by KLA-Tencor

Speaker: Jeff Reichert, KLA-Tencor Corporation
XSD Presentation
438/C010 @ 1:30 PM
View Description
Jeff Reichert, applications manager from KLA-Tencor, will discuss the latest developments in stylus & optical profilers. Discussion will include overview of differences between stylus & optical profilers, typical applications for both technologies, and a preview of new profiler technology from KLA-Tencor.
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Jun 5
Wednesday

Competing Soft Phonon Modes in TbTe3

Speaker: Michael Maschek, Karlsruhe Institute of Technology
XSD Forum
431/C010 @ 12:00 PM
View Description
We report high energy resolution inelastic x-ray measurements of competing soft phonon modes in the vicinity of the charge-density-wave (CDW) phase transition in TbTe3. We investigated two phonon modes having each a transverse polarization within the basal plane of the nearly tetragonal unit cell (a=4.308, b=25.57, c=4.314) but are dispersing along the reciprocal (100) and the (001) directions. Only the latter one is expected to go soft at qCDW = (0, 0, 0.296) and TCDW = 332 K. We found that both phonon modes go soft approaching TCDW from high temperatures. The softenings are identical down to T = 350 K, and only for T < 350 K we see a significantly stronger softening of the mode at qCDW. Our results are corroborated by lattice dynamical calculations demonstrating the degeneracy between the two crystallographic axes with respect to the formation of CDW order.
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May 31
Friday

X-Ray Detected Spin Injection in Ferromagnetic Transition Metals and Optically Excited Semiconductors

Speaker: Sioan Zohar, Magnetic Materials-XSD
XSD Presentation
401/A1100 @ 1:30 PM
View Description
The ability to control the spin degree of freedom in electronic materials plays an increasingly vital role in emerging technologies. While the basic physics governing their static properties is rapidly converging toward a coherent picture, the behavior of rf and optically excited spin states is not fully understood. X-Ray Magnetic Circular Dichroism (XMCD), a powerful technique capable of probing the spin-dependent unoccupied density of states with elemental specificity, has provided invaluable insights into both static and dynamic properties of magnetic materials. In this talk, I will present our recent work at beamline 4-ID-C advancing time resolved XMCD instrumentation, implementing novel magnetic contrast imaging (MCI) techniques, and studying optically injected spin-polarized carriers in semiconductors. The time resolved instrumentation advances have improved the data acquisition times for measuring sub nanosecond magnetic precession from 4 minutes to < 5 seconds. Bulk sensitive MCI on thick non x-ray transparent substrates was also demonstrated, permitting imaging of buried structures in the presence of a magnetic field. In our investigations of optically injected spins in III-V semiconductors, we observe an XMCD of 0.02% indicating a spin asymmetry in the band structure and Fermi level. Our results detecting optically injected spins using XMCD are the first of their kind, and pave the way for future XMCD studies of spin injected populations and spintronic systems.
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May 29
Wednesday

Utilizing Powder X-ray Diffraction to Understand Unknown Structural Motifs and Phase Transitions

Speaker: Dr. Saul Lapidus, Material Science Division, Argonne National Laboratory
XSD Presentation
401/A5000 @ 9:30 AM
View Description
Powder diffraction is a useful tool for examining a number of compounds that do not form single crystals for a variety of reasons. Unlike with single crystals, structure determination with powders is not a routine task, especially when external knowledge about the composition and structural makeup of the material are limited. I will present two interesting families of cyanide-based compounds, which highlight interesting and unique structural features and properties.

Cs2MnII[MnII(CN)6] has the archetypal Prussian blue structure with cations in the cubic voids. Substitution with smaller alkali ions lead to structural distortions and a marked increase in ordering temperatures with increasing distortions. On the other hand, substitution of larger cations, NMe4+ and NEt4+ drive a rearrangement of the Mn-CN-Mn network and produce several previously unobserved Mn(II) coordination geometries and very different structural motifs.

Zn(CN)2 forms an interpenetrated diamondoid structure and undergoes a number of transitions upon the elevation of pressure. The structures of the four new crystalline phases have been resolved through ab-initio structural determination by synchrotron powder diffraction. The specific transition depends on the hydrostatic fluid used, and surprisingly three of these new phases involve a close to 2-fold expansion of volume. This counter-intuitive expansion is due to minimization of the solid and fluid volume, rather than just the solid volume.
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May 28
Tuesday

Spectroscopic Characterization of Ru-based Catalysts for Artificial Photosynthesis

Speaker: Dooshaye Moonshiram, Purdue University
XSD Presentation
401/A1100 @ 2:00 PM
View Description
Photosynthetic water oxidation is a fundamental process in the biosphere that results in the sunlight-driven formation of O2 from water. Biological photosynthesis encompasses a series of complicated processes involving several transition states and intermediates that scientists continue to investigate. Mimicking this reaction in a man-made device will allow for sunlight-to-chemical energy conversion, with water providing electrons and protons for the formation of oxygen and reduced chemicals(1-2). Such processes are best suited for sustainable and clean generation of H2. The first synthetic catalyst designed to mimic the portion of biological photosynthesis involved in water oxidation, i.e. the catalyzed evolution of O2 from H2O, was the ruthenium-based compound commonly referred to as blue dimer. Although the water-oxidizing capabilities of blue dimer were first reported around three decades ago, several aspects of this catalytic process remained hidden. A variety of spectroscopic techniques namely stopped-flow UV-Vis Spectroscopy, Electron Paramagnetic Resonance, X-Ray Absorption Spectroscopy and Resonance Raman are used to probe the catalytic process of blue dimer as well as single site monomeric ruthenium complexes with higher turnover rate.

EPR, Raman and XAS characterization of the electronic structure and molecular geometry of peroxo intermediates in blue dimer as well as single-site water-oxidizing complexes are reported. Formation of metal bound peroxides as the result of O-O coupling has been implicated in the mechanism of catalytic water oxidation by Photosystem II oxygen evolving complex (OEC) and in Ru-based catalysts(3). However, such intermediates were never isolated and their structural and electronic characterization has not been reported. The intermediates described here are direct products of the O-O bond formation step in the studied catalysts. The combination of all these techniques enabled identification of the critical requirements for catalytic water oxidation for the design of new economical and efficient catalysts.

1. Esper B, Badura A, & Rogner M (2006) Photosynthesis as a power supply for (bio) hydrogen production. Trends in Plant Science 11.
2. Moonshiram D, et al. (2012) Structure and Electronic Configurations of the Intermediates of Water Oxidation in Blue Ruthenium Dimer Catalysis. J.Am.Chem.Soc. 134(10):4625-4636.
3. Concepcion JJ, Jurss JW, Templeton JL, & Meyer TJ (2008) One Site is Enough. Catalytic Water Oxidation by [Ru(tpy)(bpm)(OH2)]2+ and [Ru(tpy)(bpz)(OH2)]2+. J Am Chem Soc 130(49):16462-16463.
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May 21
Tuesday

Lensless X-ray Imaging of Atomic Surface Structures in the Reflection Geometry using Ptychography

Speaker: Dr. Chenhiu Zhu, Materials Science Division, Argonne National Laboratory
XSD Presentation
401/A5000 @ 11:00 AM
View Description
Coherent x-ray diffraction imaging in the reflection geometry is desirable since it offers many advantages, including (1) lensless technique without need of object lenses, (2) few restrictions on sample size, chambers or environments, (3) suitable for studies of thin films grown on any substrates, (4) no need of pin holes near samples as in holography-based techniques, and (5) easily expandable to resonant coherent x-ray imaging.

We demonstrate by numerical simulation that atomic structures on single crystal surface can be reconstructed using the ptychography coherent x-ray diffraction imaging in the reflection geometry. Our approach is based on the concept of crystal truncation rod. We can obtain the highest surface sensitivity at anti-Bragg condition, and achieve a phase contrast up to from a single atomic step. Ptychograhy scanning scheme allows us to overcome the stringent requirement for isolated samples in typical CDI experiments. We will show experimental results from real platinum (001) surfaces and their ptychography reconstructions. This technique can be readily applied to buried interfaces under catalytic and electrochemical conditions and to nanoscience applications, such as nanowire with stacking faults.
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May 17
Friday

In Situ Crystallographic Studies of Adsorption Processes in Porous Materials

Speaker: Phoebe K. Allan, University of Cambridge
XSD Presentation
433/C010 @ 2:00 PM
May 3
Friday

Transient Absorption of Attosecond Radiation by Laser Dressed Systems

Speaker: Ken Schafer, Louisiana State University
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Attosecond transient absorption (ATA) studies provide a way to push our understanding of the energy transfer between electromagnetic fields and matter to the sub femtosecond time scale. ATA is an all-optical attosecond metrology that complements methods based on the measurement of charged particles, such as attosecond streaking and electron interferometry. In this talk I will review the basics of ATA and summarize recent results in this fast growing field. I will discuss calculations from our attosecond theory group on ATA in laser-dressed atoms that highlight the extent to which attosecond dynamics can be extracted from these measurements.
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May 3
Friday

Development and Applications of X-ray Photon Correlation Spectroscopy in the Ultra-small Angle Scattering Regime

Speaker: Dr. Fan Zhang, NIST
XSD Presentation
401/B4100 @ 10:00 AM
View Description
Partially coherent radiations generated by high-brilliance third generation synchrotron sources have allowed measurements of slow dynamics in various soft and hard material systems. We have recently developed an X-ray photon correlation spectroscopy (XPCS) technique in the ultra-small angle scattering regime, which fills an existing gap between the accessible Q ranges of dynamic light scattering and pinhole-based XPCS and enables studies of low-frequency equilibrium and nonequilibrium dynamics in optically opaque materials. This technique, based on the Bonse-Hart ultra-small angle X-ray scattering instrument at the Advanced Photon Source, requires modifications to the beamline configuration and instrument operations for dynamic measurements. We will review the basic features of this technique, and will discuss in details the optimizations that we made to meet the needs of signal-to-noise limited XPCS studies. We will present the data analysis approaches that we established to quantify the dynamic time scales of measured equilibrium or nonequilibrium processes. Finally, we will use a few examples to illustrate the applications of this technique in understanding of equilibrium dynamics of soft materials and nonequilibrium behavior of both soft and hard materials.
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May 2
Thursday

A Synchrotron X-ray Diffraction from Perovskite Thin Flms: Probing the Effects of Microscopic Structure on Macroscopic Properties

Speaker: Dr. Rebecca Sichel-Tissot, Department of Materials Science and Engineering, Drexel University
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Perovskite oxides are a fascinating class of materials - they exhibit a huge range of properties such as magnetic ordering, ferroelectricity, metal to insulator transitions, piezoelectricity, just to name a few. These properties are extremely sensitive to the position, bonding, and electronic state of the central atom. As a result, small strains or structural changes can have large effects on the functional properties. The perovskites present an exciting opportunity to gain insight into these phenomena by pairing structural characterization with measurements of the macroscopic properties.

In this talk, I will discuss how synchrotron x-ray diffraction can be used to study ferroelectricity, piezoelectricity, and charge disproportionation in perovskite thin films. Ferroelectric domains in (Pb,Zr)TiO3 thin films were written using PFM. X-ray nanodiffraction was used to simultaneously image the domains and probe the structure. By comparing our results with PFM imaging, we find that the strain induced by the writing process is responsible for certain polarizations being less stable than others. In piezoelectric thin films, the film is macroscopically attached (clamped) to its substrate and the average piezoelectric distortion along the film-substrate interface must be zero. We observe very different results at the microscopic level. Using time-resolved x-ray microdiffraction, we find that the piezoelectric response of individual domains in BiFeO3 thin films is not zero and varies on a domain-by-domain basis. Finally, we combine electronic transport measurements with x-ray diffraction from charge disproportionation in La1/3Sr2/3FeO3 thin films. The temperature dependence of the resistivity and intensity and correlation lengths of the charge disproportionation reflections give insight into the nature of this phase transition.
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May 1
Wednesday

Double Photoionization of Aromatic Molecules

Speaker: Dr. Ralf Wehlitz, Synchrotron Radiation Center, University of Wisconsin - Madison
XSD Presentation
401/A1100 @ 2:00 PM
View Description
Electron correlations can be found in various fields of physics whenever we have to go beyond the independent particle model. A convenient method to study electron correlations in atoms and molecules is to measure the probability to remove TWO electrons simultaneously with a single photon (called double photoionization) from the sample. Because a single photon can interact with only one electron, the removal of two electrons is due to electron correlations. I will present our recent results on double photoionization over a broad range of photon energies for several aromatic molecules. Our goal is to find systematic trends as the molecular structure of our different samples changes. Questions that will be addressed in the talk are: How does the structure of a molecule affect the double-photoionization process? Which mechanisms contribute to double photoionization?
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Apr 26
Friday

Atomic Structural Evolution in Cu-Zr and Ni-Nb Liquids and Glasses: A measure of liquid fragility?

Speaker: Dr. Nicholas Mauro, Washington University
XSD Presentation
401/A1100 @ 11:00 AM
View Description
The glass forming ability (GFA) of metallic alloys is widely varied. Bulk metallic glasses (BMGs) have been identified in a number of alloy systems but far more compositions can be formed only when their liquids are rapidly quenched. Understanding the differences between these systems remains one of the most important problems in condensed matter physics. Understanding the structural evolution of metallic liquids as they are supercooled and quenched into glasses is critically important, not only for providing insight into the nature of the glass transition, but also for understanding technical aspects of glass formation and the thermal stability of the glassy solid. In this talk, we discuss the results of high energy X-ray diffraction studies on Cu-Zr and Ni-Nb liquids and glasses. The temperature dependence of the X-ray structure factors has been measured in the glass from room temperature to above the glass transition temperature by means of stationary diffraction in a ! capillary while data in the equilibrium and supercooled liquid state were acquired using the Beamline Electrostatic Levitation technique. As will be shown, both the structure factors as well as the calculated total pair correlation functions display an anomalous evolution indicating a rapid acceleration of short-range order above the glass transition temperature. This behavior contrasts sharply with that observed in high glass forming ability metallic alloys suggesting a structural fragility metric distinguishing good glass formers from poor ones. We discuss the implications for this observation on our fundamental understanding of glass formation.
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Apr 25
Thursday

Towards a Sustainable Future: Hard X-ray Methodologies for Energy and Environmental Applications

Speaker: Olaf Borkiewicz, Miami University
XSD Presentation
401/A5000 @ 10:00 AM
View Description
The anticipated doubling of the worlds energy consumption within the next 50 drives the need for efficient and clean energy. Advanced electrical energy storage systems and nuclear energy are technologies that are crucial to achieving this goal. However, key materials challenges must be overcome before these technologies become viable:
  • For electrical energy storage systems to become practical for transportation and electrical grid application, higher capacity/power and faster recharge times are needed. Gaps in our understanding of the atomic- and molecular-scale processes that control performance and failure of these systems must be addressed by fundamental research.

  • For safe nuclear energy industry, the challenges lay in the effective disposal of the radioactive waste generated by the nuclear fuel cycle. Many solutions involve "multiple-barrier" geological depositories which use a wide range of sequestration agents. Understanding of the structural and chemical properties of these agents, and their interaction with radioactive elements, is key to the fidelity of these facilities.


In both electrical energy storage and nuclear energy, the complexity of the systems and the often metastable and/or disordered nature of the materials pose a significant characterization challenge. This challenge can be addressed through judicious selection and, where necessary, development of incisive characterization tools. We have recently designed an operando electrochemical cell, optimized for a variety of hard X-ray methodologies, and used it to probe next-generation battery materials with an unprecedented level of precision. First-of-the-kind operando pair distribution function measurements have provided a detailed understanding of high-performance electrode materials. In situ time-resolved powder X-ray diffraction data, analyzed through Rietveld refinement, combined with X-ray absorption spectroscopy, scanning electron microscopy and other analyses, have been used to evaluate the use of hydroxylapatite as radionuclide sequestration agent and solid nuclear waste form.
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Apr 24
Wednesday

Resonant Inelastic X-ray Scattering in a Mott Insulator

Speaker: Nandan Pakhira, Department of Physics, Georgetown University
XSD Presentation
401/B4100 @ 3:00 PM
View Description
I will be talking on the recently published calculation of RIXS response in the Falicov-Kimball model. The Falicov-Kimball model is exactly solvable under single site dynamical mean field theory approximation and the RIXS response in this model can also be accurately calculated up to a local background correction. We find that on resonance the RIXS response is greatly enhanced. The response systematically evolves from a single peak structure, arising due to relaxation processes within the lower Hubbard band, to a two peak structure, arising due to relaxation processes within the upper Hubbard band as well as across the Mott gap into the lower Hubbard band, as we vary the incident photon frequency to allow excitations from the lower Hubbard band to the upper Hubbard band. The charge transfer excitations are found to disperse monotonically as we go from the center of the Brillouin zone towards the zone corner. These correlation induced features are found to be robust and survive even for large Auger lifetime broadening effects which can mask the many-body effects by smearing out spectral features. As a comparison, we also calculate the dynamic structure factor for this model, which is proportional to the nonresonant part of the response, and does not show these specific signatures.
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Apr 23
Tuesday

Status of SRX, the NSLS-II Spectromicroscopy Beamline

Speaker: Vincent De Andrade, Brookhaven National Laboratory
XSD Presentation
438/C010 @ 3:00 PM
View Description
The Sub-micron Resolution X-ray spectroscopy beamline (SRX), whose commissioning phase will start in July 2014, is one of the seven project beamlines of NSLS-II at Brookhaven National Laboratory. Operating at energies ranging from 4.65 to 23 keV, SRX will address a wide variety of scientific applications probing heterogeneous complex systems from the meso to the nanoscale. Combined with state of the art optics, the ultralow emittance and stability of the NSLS-II source is particularly suitable for micro- and nanoprobes like SRX. The SRX main optical components consist of a horizontally focusing mirror creating a secondary source whose size is adjustable with slits, an ultra-stable horizontally deflecting monochromator and two sets of Kirkpatrick-Baez mirrors in two inline stations as focusing optics for operations requiring either high flux (microprobe) or high resolution (nanoprobe). The presentation will focus first on the beamline layout that has been optimized with FEA, ray-tracing and wave front propagation simulations using respectively Shadow and SRW. Results demonstrate that the SRX micro- and nanoprobes will provide 1013 and 1012 ph/s respectively in a sub-micron and a 50 nanometer spot, with an excellent energy resolution (close to the Darwin width of the selected crystals). In a second time, the end-station design will be described with highlights on interferometry tests performed on sample stage assemblies as well as considerations to handle high throughput fluorescence signal. One will conclude on possible early science experiments that are expected by the end of the year 2014.
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Apr 23
Tuesday

Microsecond Time-resolved XAS Measurement with the Energy Dispersive EXAFS Setup and Ultrafast (ps) X-ray Scattering on Chemical Reactions

Speaker: Qingyu Kong, Société civile Synchrotron SOLEIL
XSD Presentation
433/C010 @ 1:30 PM
View Description
The energy dispersive EXAFS (EDE) setup at ODE beamline Soleil Synchrotron as well as the recent development of microsecond (µs) time-resolved XAFS data collection and its application to film continuously the electronic and geometric structural kinetics in a thermolysis reaction will be presented. The proposal of a laser pump and XAS probe development using EDE setup will be introduced briefly. In the second part of the talk, the optical pump and X-ray probe setup and ultrafast solution scattering on small molecules studied in ID09B ESRF will be presented, the photofragmentation reaction of triruthenium dodecacarbonyl Ru3(CO)12 in cyclohexane will be used as an example to show the data analysis process and the complementary nature of ultrafast X-ray scattering and ultrafast spectroscopy in the determination of transient molecular structures and chemical reaction mechanisms.
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Apr 23
Tuesday

Fabrication of High-aspect-ratio Nano-structures for X-ray Microscopy Applications

Speaker: Ming Lu, Brookhaven National Laboratory
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Recent efforts of x-ray microscopy research and development are pushing the resolution of state-of-the-art x-ray microscopes toward single digit of nanometer region. Among all the x-ray focusing optics, Fresnel zone plates are superior considering their nature of two-dimensional focusing and a resolution close to diffraction limit. However, high-resolution zone plates operated at x-ray wavelengths, especially in hard x-ray region, require a high-aspect-ratio geometry for their concentric metal zones to efficiently diffract lightwave, a challenge to nanofabrication researchers. In this talk, I will discuss three different approaches for fabricating high-aspect-ratio metallic nanostructures, including methods utilizing stressless electroforming molds, double-patterning, and zone-doubling techniques. Using these techniques we demonstrated hard-x-ray zone plates with 19:1 aspect-ratio and 30 nm outermost zone width, as well as a platinum resolution test pattern featuring 17-nm-wide, 255-nm-tall gratings.
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Apr 22
Monday

Nanoscale Soft X-ray Microscopy at HZB: Current Status of the TXM and Optics Development

Speaker: Stephan Werner, Institute for Soft Matter and Functional Materials, Berlin, Germany
XSD Presentation
401/A1100 @ 11:00 AM
View Description
The Helmholtz-Zentrum Berlin (HZB) operates a full-field transmission X-ray microscope (TXM) in the soft X-ray photon energy range at the undulator beamline U41-FSGM at the BESSY II electron storage ring. Due to the optical setup the HZB-TXM permits cryo X-ray tomographic as well as spectromicroscopic applications in material and life sciences. Some examples of these applications will be shown. The spatial resolution of the full-field microscope is limited by the numerical aperture of the zone plate objective and the wavelength used for imaging. The resolving power can be improved by decreasing the outermost zone width or imaging in higher orders of diffraction. At HZB, we work in our nanotechnology lab on both approaches. Recent results on the nanofabrication of high resolution zone plate objectives will be presented. In addition, the achievable resolution of the HZB-TXM will be discussed.
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Apr 18
Thursday

Pushing the Limits of Powder Diffraction: Determination of the Crystal and Local Structures of Highly Complex Perovskite Materials

Speaker: Graham King, Lujan Neutron Scattering Center, Los Alamos National Laboratory
XSD Presentation
401/B5100 @ 10:00 AM
Apr 17
Wednesday

X-ray Absorption and Phase Retrieval using Energy-resolved Measurements

Speaker: Doga Gursoy, University of Houston
XSD Presentation
431/C010 @ 3:00 PM
View Description
X-ray phase imaging has been of interest in the last couple of decades for potential applications in medical imaging and material characterization. A key aspect in phase imaging is the well known “phase problem” which involves detangling the absorption and phase effects from intensity measurements. In this talk, I will make a topical review of the phase retrieval methods and present a novel single-step method to simultaneously retrieve x-ray absorption and phase images which is valid for a broad range of imaging energies and material properties. The method relies on the availability of spectrally resolved intensity measurements, which is now possible using semiconductor x-ray photon counting detectors. I will discuss the potential and utility of the method and address the engineering challenges in x-ray detection with the currently available spectral detectors.
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Apr 17
Wednesday

Structural and Interfacial H2O/OH Species: Two Case Studies on their Roles in Host Structural Stability

Speaker: Hsiu-Wen Wang, Indiana University
XSD Presentation
401/A1100 @ 10:00 AM
Apr 16
Tuesday

Zone Plates for High Photon Energy Focusing - Lessons from the Past, Reinterpreted

Speaker: Nicolaie Moldovan, Advanced Diamond Technologies
XSD Presentation
401/A1100 @ 11:00 AM
View Description
The presentation reviews the main achievements in zone plates fabrication for X-ray focusing, with accents on how the existent knowledge can be extended to reach the goal of 20 nm resolution at 25 keV photon energy. Several approaches will be discussed, revealing that traditional nanofabrication ways will not work, while new, combined approaches will do the job. Among the discussed methods: sequential height increases by soft x-ray exposure and electroforming, layered depositions and nanolaminates, zone doubling and resolution increase by adding higher order zones, stacking and composing zone plates by MEMS-enabled alignment, diamond Fresnel lenses, and others. Combining the positives of these approaches leads to a heavily-engineered concept of zone plates fabrication, but with good chances of success, and even a perspective for higher photon energies.
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Apr 15
Monday

Characterization of the Fluctuating Charge States in Transition Metal Oxides using Local Structure as a Probe

Speaker: A. M. Milinda Abeykoon, Brookhaven National Laboratory
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Abstract: It is becoming apparent that nanoscale fluctuations in the charge state are important to the physics of transition metal oxides. The temperature evolution of structural modulation associated with charge (co) and spin order (so) in La1.67Sr0.33NiO4 has been investigated using neutron powder diffraction [1]. For the first time, we report an anomalous shrinking of the “a” lattice parameter that correlates with Tco, at the temperature where long-range stacking order of charge stripes disappears. We show that this response may be explained as resulting from the energy contributed by the interlayer electrostatic interaction leading to shrinkage of c/a. In addition, we report anomalies in the temperature evolution of the refined atomic displacement parameters (ADP) and local structural parameters in the atomic pair distribution function (PDF), which show quite different temperature dependence consistent with the persistence of localized charges, presumably in the form of short range ordered stripe domains, over a broad temperature range above Tco.
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Apr 10
Wednesday

Surface Octahedral Distortions and Atomic Design of Perovskite Interfaces

Speaker: Bruce A. Davidson, CNR-IOM TASC National Laboratory
XSD Presentation
431/C010 @ 10:00 AM
View Description
Progress in understanding and exploiting the properties of complex oxide heterostructures requires advances in state-of-the-art growth and characterization techniques for these materials, as atomic control of their synthesis is demonstrably inferior to that of their semiconductor counterparts. Here we report significant improvements in the atomic design of perovskite interfaces made possible by advances in in situ control of the surface by reflection high-energy electron diffraction (RHEED) during growth that reveal the surface termination and characteristic octahedral distortions in the surface layer as it is being deposited. This RHEED approach applies generally to growth of polar and nonpolar perovskite unit cells when a desorption-controlled growth regime is not utilized. As an example, we demonstrate its use in the optimization of atomically-designed manganite/titante interfaces that eliminates cation intermixing and anomalous unit cell dilations that have previously been observed. Careful analysis of the crystal structure shows an unusual evolution of the octahedral distortions that include both J-T type and rotations near the interface that are not seen in bulk. These new results should be included in electronic structure calculations modeling the properties of real heterointerfaces.
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Apr 8
Monday

Coherent X-ray Diffraction Imaging of Strain on the Nanoscale

Speaker: Ross Harder, XSD-Microscopy
XSD Presentation
401/A1100 @ 2:00 PM
View Description
Materials often contain fundamental properties that are determined by structures on nanometer length scales. An example of this is the nanometer size pores in synthetic zeolites crystals. The shapes of the pores can define molecular sieves and the composition of the walls can be tailored to catalytic applications. Occlusions in the pores will significantly restrict the function of the material and if occurring below the surface may be difficult to detect. The x-ray diffraction Bragg peaks of crystals contain a wealth of information regarding the structure of the sample. If the x-ray beam used to study a sample is spatially and temporally coherent, the scattered x-rays in the vicinity of the Bragg peak contains local structural information on potentially nanometer length scales. Images are formed by computational inversion from reciprocal space to direct space using phase retrieval algorithms. These images contain both morphological and strain information on tens of nanometer length scales in three dimensions.

This talk will describe the technique of coherent x-ray diffraction (CXD) imaging in the Bragg geometry and show recent results from 34-ID-C, including a study of zeolites being tailored for catalysis of pollutant gases, the response of a nanocrystal to multi gigapascal pressure, and time resolved phonon modes in nanocrystals.
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Apr 4
Thursday

Diamond X-ray Beam Position Monitors

Speaker: Dr. John Smedley, Brookhaven National Laboratory
XSD Presentation
438/C010 @ 2:00 PM
View Description
Ever wonder where your x-rays are? How many photons you have? Where they‘re going? A diamond based x-ray beam position monitor may be for YOU! Advances in CVD diamond growth have made this material an attractive option for x-ray diagnostics. Diamond is radiation hard, solar blind, and has very small leakage current (sub pA). The low Z of diamond makes it attractive for transmission diagnostics, while the high thermal conductivity makes it attractive for high flux applications. This talk will focus on recently demonstrated monitors for both white and monochromatic beams, along with a discussion of goals for future development.
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Apr 3
Wednesday

Wave Propagation in Inhomogeneous Media, and Possible X-ray Applications

Speaker: Professor Nicole Moore, Elmhurst College
XSD Presentation
431/C0101 @ 3:00 PM
Mar 19
Tuesday

Zone Plate Optics for Sub-15 Soft X-ray Microscopy

Speaker: Julia Reinspach, Stanford University
XSD Presentation
401/A1100 @ 11:00 AM
View Description
The development of zone plate lenses is crucial for the progress of high-resolution x-ray microscopy. Since the resolution achievable in imaging is proportional to the outermost zone width of the lens, narrow zones have to be nanofabricated. In addition, high aspect ratios are required to achieve high diffraction efficiencies, thus rendering zone plate nanofabrication challenging. At the Biomedical and X-Physics group at KTH (Stockholm, Sweden) the development and improvement of nanofabrication processes for high-resolution high-diffraction-efficiency soft x-ray optics is a key aspect. Different approaches, such as cold development, cryogenic RIE, or the concept of nickel-germanium zone plates have been investigated and applied, resulting in soft x-ray zone plates with zone widths down to 12 nm and diffraction efficiencies up to 9.6% (at λ=2.48 nm).
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Mar 13
Wednesday

A Route to High Neel Temperatures in 4D and 5D Transition Metal Oxides

Speaker: Priya Mahadevan, S.N. Bose National Centre for Basic Sciences
XSD Presentation
431/C010 @ 11:00 AM
Mar 11
Monday

Roaming Radical Reactions

Speaker: Arthur G. Suits, Department of Chemistry, Wayne State University
XSD Presentation
401/A1100 @ 2:00 PM
View Description
An unusual decomposition mechanism of highly vibrationally excited molecules, dubbed the “roaming mechanism,” has recently been discovered and is now a very active area of investigation. In these reactions, a molecule undergoes partial dissociation to radical fragments by simple bond fission. When the fragments separate to 3-4 Å, “roaming” reorientation becomes feasible as the kinetic energy is low and the angular forces may be comparable to the radial forces. If this leads the system to access a distinct reactive domain, intramolecular abstraction may take place giving unexpected products often with with large vibrational excitation. This pathway may deviate substantially from the nominal minimum energy path, and in some cases appears to avoid the normal transition state geometry entirely. Many of the details have come to light through high-resolution ion imaging studies of formaldehyde, in concert with quasi-classical trajectory calculations from Bowman and coworkers. Many other examples of roaming dynamics have now been reported, both in experiment and theory. I will emphasize recent results documenting “roaming-mediated isomerization” which appears to be a general feature of the decomposition of nitro compounds. In addition, I will introduce new universal probes of reaction dynamics affording isomer and even conformer selectivity.
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Mar 4
Monday

Stimulated Electronic X-ray Raman Scattering with XFEL Sources

Speaker: Dr. Nina Rohringer, Center for Free-Electron Laser Science, Hamburg, Germany
XSD Presentation
401/A1100 @ 11:00 AM
View Description
The invention of x-ray free-electron lasers (XFELs) opens the pathway to transfer powerful spectroscopic techniques from the optical to the x-ray region, to ultimately study the interplay of coherent electronic and vibrational dynamics on the timescale of chemical reactions. Resonant Inelastic X-ray Scattering (RIXS) is a viable spectroscopic tool to study the valence-electronic environment of a target atom, which can be selectively addressed by the resonantly tuned x-ray beam. The cross section for this process is, however, small, so that even with powerful XFEL pulses the recording of single-shot RIXS spectra of dilute samples or molecules in the gas phase are challenging. This hampers the application of RIXS in optical pump x-ray probe experiments, which would, for example, be one method of choice to study light-induced chemical reactions. Here we demonstrate, how this bottleneck can be overcome by stimulating the RIXS process. We present results of a recent experiment o! n stimulated RIXS at the Linac Coherent Light Source XFEL in a gas sample of atomic neon, thereby amplifying the RIXS signal by 6-7 orders of magnitude. Using broadband XFEL pulses, which are characterized by a stochastic, spiky substructure of their spectrum, both “pump” and “dump” photons can be provided in a single pulse, thereby stimulating the scattering process and driving an exponential amplification of the signal. Despite the overall broad bandwidth, high-resolution RIXS spectra can be achieved by statistical analysis of a series of stochastic single-shot spectra. The energy resolution is determined by the spectral coherence of the XFEL source, and in principle allows for vibrational resolution. These findings open up a new class of experiments at XFEL sources, with a colossal increase of the RIXS signal. Results of our recent experiment will be presented, along with a perspective and theoretical feasibility study of stimulated RIXS measurements in small molecules.
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Feb 19
Tuesday

Probing and Reconstructing Transient One-Dimensional Crystalline Strains Using Time-Resolved X-ray Diffraction

Speaker: Yuan Gao, University of Delaware
XSD Presentation
432/C010 @ 12:00 PM
View Description
Since the late 1990s, ultrafast x-ray pulses have been used to probe impulsive strains propagating in the bulk of optically opaque materials. Time-resolved x-ray diffraction has been proven to be a very powerful tool for visualizing transient one-dimensional crystalline strains, ranging from crystal growth to shockwave production.

In this presentation, I will describe a series of time-resolved x-ray diffraction experiments that visualize transient strain formation from nanometer-scaled laser-excited metallic films. Utilizing a table top picosecond x-ray source in conjunction with a high-power optical laser system, the resulting optical pump/x-ray probe spectra reveal that the spatiotemporal structure of the transient acoustic pulse is bipolar with acoustic wave-vectors up to inverse of the film thickness. In addition, I will also discuss the real-world constraints that place limits on the validity of the reconstructed transient acoustic pulse.
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Feb 19
Tuesday

Methods, Machinery, and Money: The LERIX-2 Conceptual Design

Speaker: Jerry Seidler, University of Washington
XSD Presentation
401/A1100 @ 10:00 AM
View Description
I will discuss the scientific motivation for, and technical details of, the recently completed conceptual design for the LERIX-2 spectrometer as part of the APS-U. In the conceptual design, we expand to 144 analyzers while taking the most successful mechanical and operational features of the LERIX-1 and LERIX-1B instruments. Among the issues that need to be resolved for the final design are the selection of detectors and the selection and reliable mass-fabrication of spherically-bent crystal analyzers (SBCA's). If in-house, rather than commercial, fabrication of the needed highly efficient SBCA's is possible, it will result in a factor of two cost savings for this instrument.
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Feb 11
Monday

Fundamental Dynamics in Molecules, Clusters, and Interfacial Systems Studied with Novel XUV and X-ray Light Sources

Speaker: Oliver Gessner, Lawrence Berkeley National Laboratory
XSD Presentation
401/A1100 @ 2:00 PM
View Description
Ultrafast XUV and X-ray light sources offer new opportunities to unravel fundamental electronic and nuclear dynamics in matter. The Chemical Dynamics program at the Ultrafast X-ray Science Laboratory is focused on the application of emerging laboratory- and accelerator-based X-ray techniques to monitor the flow of charge, mass, and energy in molecules, clusters, and interfacial systems. A brief overview of the program will be followed by the discussion of two particular showcase examples of ongoing research: The study of photoinduced charge-transfer dynamics in dye-sensitized nanocrystals by time-resolved X-ray photoelectron spectroscopy and the investigation of quantized fluid dynamics in nano- to micron-scale superfluid helium droplets by single-shot coherent diffractive imaging.

Interfacial charge transfer studies are performed at the Linac Coherent Light Source (LCLS, SLAC National Accelerator Laboratory) and the Advanced Light Source (ALS, Berkeley). Recent LCLS results demonstrate the potential of time-resolved X-ray photoelectron spectroscopy (TRXPS) to monitor charge migration in complex interfacial systems with femtosecond time resolution, chemical sensitivity and element specificity. The visible light induced transient oxidation state of N3 dye molecules adsorbed to nanocrystalline ZnO is characterized in a concerted effort of TRXPS experiments and ab-initio calculations of the interfacial electronic structure.

The superfluid nature of helium droplets presents a rare opportunity to study the onset of macroscopic quantum phenomena in sub-micron scale systems. Pure and doped helium droplets are studied by coherent diffractive imaging (CDI) using femtosecond X-ray pulses from the LCLS. Single-shot CDI data provide the most direct access yet to droplet size- and shape-distributions as well as fundamental dynamics inside the clusters. The results will be discussed in the context of the onset of quantum vorticity in finite three-dimensional quantum systems.
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Feb 5
Tuesday

1913-2013: The Centennial Anniversary of the Birth of X-Ray Crystallography

Speaker: Denny Mills, Advanced Photon Source, Argonne National Laboratory
XSD Presentation
401/A1100 @ 1:00 PM
View Description
The year 2013 marks the 100th anniversary of the publication of Bragg’s Law by W. L. Bragg and the publication of the first crystal structure determination by x-rays, by W.H. Bragg and W.L. Bragg. This presentation will include a brief introductory discussion regarding the knowledge of the generation and scattering of x-rays in this time period, some personal background regarding the Braggs, and how Laue’s famous photograph set the stage for this father and son team to not only win the Nobel Prize for Physics in 1915 "For their services in the analysis of crystal structure by means of X-rays," but to change the world of science for many years to come through their development of x-ray crystallography.
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Jan 25
Friday

Beyond Li-ion Batteries

Speaker: George Crabtree, Director, JCESR
XSD Presentation
401/A1100 @ 1:30 PM
View Description
The Joint Center for Energy Storage Research (JCESR) develops concepts and technologies for portable electricity storage for transportation and stationary electric storage for the electricity grid. Electrified transportation replaces foreign oil with a host of domestic electricity sources such as gas, nuclear, wind and solar, and utility scale electric storage enables the grid to bridge the peaks and valleys of variable wind and solar generation and consumer demand. JCESR looks beyond Li-ion technology to new materials and phenomena to achieve the factor of five increases in performance needed to realize these transformational societal outcomes. JCESR will leave three legacies: a library of fundamental scientific knowledge of materials and phenomena needed for next-generation batteries, demonstration of battery prototypes suitable for scale up to manufacturing for transportation and the grid, and a new end-to-end integrated operational paradigm for battery research and development spanning discovery research, design, and demonstration.
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Jan 24
Thursday

Introduction of JML Optical Industries, LLC

Speaker: Scott Casella, JML Optical Industries, LLC
XSD Presentation
401/B4300 @ 1:30 PM
Jan 22
Tuesday

Tracking Electron Transfer Dynamics in Coordination Chemistry with X-ray Spectroscopy

Speaker: Wenkai Zhang, PULSE Institute, SLAC National Accelerator Laboratory
XSD Presentation
401/A1100 @ 11:00 AM
View Description
The ability of coordination compounds to catalyze chemical reactions and absorb visible radiation makes them appealing targets for the development of photocatalysts. One of the attributes that makes transition metals excellent catalysts – a high density of frontier orbitals – can also lead to ultrafast quenching of electronic excited states. Understanding the properties of coordination complexes that dictate the electronic relaxation dynamics has practical, as well as fundamental importance. Most successful photosensitizers and photocatalysts have utilized 4d and 5d metal centers. The significant cost and low abundance of many 4d and 5d metals has inspired attempts to substitute high cost atoms with isoelectronic 3d metal complexes. But the exchange iron for ruthenium increases the charge transfer relaxation rate by roughly a factor of one million. The huge distinction in lifetimes has generally been attributed to differences in the ligand field excite state energies. But we currently still lack a detailed understanding of how ligand field excited states and charge transfer excited states interact and how this depends upon nuclear and electronic structure. We investigated the role of ligand field excited states in the relaxation dynamics of photogenerated charge transfer states in a series of iron(II) coordination compounds with hard x-ray emission spectroscopy (XES). The tremendous sensitivity of XES to the charge and spin state of the transition metal centers make these techniques ideally suited to investigating the electron dynamics in coordination chemistry. By studying mixed cyanide and bipyridine ligands with advanced x-ray spectroscopy, we discovered that the excited state decay pathway can be controlled and adjusted by systematically tuning the ligand field splitting. We demonstrated that changing the iron ligands lend to a 100-fold increase in the charge transfer excited state lifetime, a critical metric for earth abundant photosensitizers.
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Jan 17
Thursday

Programmable Assembly of Colloidal Crystals with DNA

Speaker: Andrew Senesi, Northwestern University
XSD Presentation
433/C010 @ 3:30 PM
View Description
Nano-structured materials and their assemblies have generated considerable scientific and industrial interest as a result of new chemical and physical interactions as their size is reduced and they are positioned into well-defined spatial arrangements. Indeed, a grand challenge in nanotechnology is to construct materials comprised of positionally encoded elements (i.e. nanoparticles) with fine control over spacing, symmetry, and composition, with single- or sub-nanometer precision and registry. The ability to exercise such control over multiple length scales and in three dimensions for a single system would, in principle, provide researchers with a route to fabrication “materials by design”, in which one could design and build a functional system with programmed chemical and physical properties, useful in material synthesis, optics, biomedicine, energy, and catalysis. In this talk, I will discuss recent progress towards this goal, by using DNA as a programmable ligand to direct the assembly of nanoparticles into crystalline arrays. DNA is ideally suited for this purpose, as synthetically tunable variations in nucleotide sequence allow for precise engineering of the nanoparticle’s hydrodynamic radius and binding properties. These factors, in turn, dictate the crystallographic symmetry and lattice parameters of the assembly. By further employing a DNA-functionalized substrate, thin-film nanoparticle superlattices can be grown in a layer-by-layer fashion with fine control over the number of particle layers in the assembly (i.e. film thickness). Importantly, the judicious choice of DNA substrate-particle interconnects allows one to tune the interfacial energy between various crystal planes and the substrate, and thereby control crystal orientation. A theoretical framework to understand these results is presented. These nanoparticle superlattices can further be patterned in arbitrary locations on a substrate using molecular printing techniques such as dip-pen nanolithography (DPN) and polymer pen lithography (PPL). The principles developed in this work represent a major advance in the bottom-up synthesis of nanomaterials and a major step towards the integration of nanoscale materials into functional device architectures. Lastly, ultrafast pump-probe studies of third-generation materials for future photovoltaics will be presented. One such novel photovoltaic material uses heavy O doping of ZnTe to generate the formation of an intermediate band within the forbidden gap, in order to improve the matching of semiconductor absorption and solar spectra. This approach is believed to become useful for realization of single junction solar cells with very high efficiencies. However, the implementation of such devices requires advanced characterization techniques. Multiphoton optical pulse excitations are demonstrated to induce multiband charge transfer dynamics in ZnTe:O films as revealed when monitoring the time-resolved photoluminescence signals.
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Jan 17
Thursday

Giant Thermoelectric Effect (GTE) in Graded porous micro-nanostructured Thermoelectric Materials

Speaker: D. G. Niarchos, Nuclear Center Demokritos, NCSR Athens, Greece
XSD Presentation
401/A1100 @ 3:00 PM
Jan 17
Thursday

Theoretical Study of the Transparency-like Phenomena in the XUV Induced by Coherent Coupling of the Doubly Excited States in Helium

Speaker: Michal Tarana, Department of Physics, Purdue University
XSD Presentation
401/A1100 @ 2:00 PM
View Description
Presently there is great interest in the application of light in the X-ray regime, produced by high-order harmonics, to investigate novel coherent X-ray optical phenomena. Loh et al. [1] report the observation of EIT-like behavior in the extreme ultraviolet (XUV) by coherent coupling of 2s2p and 2p2 doubly excited states in He, probing with laser-produced high-order harmonics. The EIT-like phenomenon observed in their work is characterized solely by an increase in transmission over the entire unperturbed lineshape. It is the aim of our work [2] to extend the phenomenological theoretical treatment of this effect included in [1]. We present calculations based on the solution of the time-dependent Schrodinger equation in the LS-coupling configuration interaction basis set. The absorbing boundary is represented by the complex absorbing potential and we present here the analysis of the ionization yield obtained. This approach allows for more accurate treatment of the ionization continuum than presented in [1].

[1] Z.H. Loh, C.H. Greene and S.R. Leone, Chem. Phys. 350, 7 (2008).
[2] M. Tarana, C.H. Greene, Phys. Rev. A 85, 013411 (2012).
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Jan 15
Tuesday

Some Software for Beamlines

Speaker: Guy Jennings
XSD Presentation
401/A1100 @ 12:00 PM
View Description
A variety of locally written software is in use on Sectors 11 and 12 at the APS. I will describe the available software and some of the organizing principles behind its design in the hope that it may be more widely useful at other beamlines.

If time/audience interest permits I will also present an overview of a number of relevant features of the Qt framework as related to the software I have written.

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Part of the January 2013 Seminar Series Software for Beamlines. These talks present tools for beamline scientists using spec or python to control data collection or automate alignment or similar beamline tasks.
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Jan 14
Monday

Pushing the Limits of Full Field and Scanning X-ray Microscopy

Speaker: Dr. Hendrik Ohldag, Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory
XSD Presentation
401/A1100 @ 2:00 PM
View Description
X-ray microscopy has become a commonly available and often used tool for element specific investigations on a nanometer scale. However, with a constantly growing user community, the demand for a more flexible sample environment grows as well. In my talk, I will describe several approaches that were realized at the SSRL and the ALS to push the limits of x-ray microscopy, e.g. how to improve the resolution of PEEM microscopy without any changes to the microscope, how to measure in large magnetic fields with sub 10ps time resolution, or how to follow chemical reactions in situ.
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Jan 14
Monday

Ultrafast Spin, Phonon and Charge Dynamics: From Femtoseconds to Nanoseconds at Nanoscale

Speaker: Vladimir A. Stoica, University of Michigan, Ann Arbor
XSD Presentation
401/A1100 @ 1:00 PM
View Description
The ultrashort-pulse photoexcitation and measurement techniques are of tremendous interest due to their capability to uncover the ultrafast transient response of materials. Among light-based pump-probe techniques, an original approach employing low-power fs-fiber-lasers was developed to acquire, manipulate and modify a wideband spectrum of photoexcitations in thin films and nanostructures.

In epitaxial ferromagnetic films, coherent spin waves are generated with femtosecond laser pulses via thermal excitation mediated by magnon-electron and magneto-elastic coupling. The propagation speeds and attenuation lengths of exchange spin wave modes are determined during the propagation and reflection at the film boundaries, consistent with their dispersion relation. Moreover, photo-thermal excitation could be used to achieve coherent control of the magnetization vector. An optically-induced spin reorientation transition of first-order is revealed and provides a new route to coherent magnetization switching.

Another experimental effort has been focused on phonon dynamics and thermoelectric transport studies. The coherent optical phonon spectroscopy was employed during the fs laser-induced nanostructuring in binary semiconductors such as Sb2Te3 and InSb. Nanostructure fabrication process optimization resulted in highly ordered periodic nanostructures without the adverse effects of residual phase separation. In another case, pump-probe measurements are used to understand the behavior of acoustically mismatched thin films to further assist the design of high-Q acoustic resonators at GHz frequencies.

Lastly, ultrafast pump-probe studies of third-generation materials for future photovoltaics will be presented. One such novel photovoltaic material uses heavy O doping of ZnTe to generate the formation of an intermediate band within the forbidden gap, in order to improve the matching of semiconductor absorption and solar spectra. This approach is believed to become useful for realization of single junction solar cells with very high efficiencies. However, the implementation of such devices requires advanced characterization techniques. Multiphoton optical pulse excitations are demonstrated to induce multiband charge transfer dynamics in ZnTe:O films as revealed when monitoring the time-resolved photoluminescence signals.
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Jan 11
Friday

Strong-field Physics with Mid-infrared Lasers

Speaker: Anthony DiChiara, The Ohio State University
XSD Presentation
401/B4100 @ 11:00 AM
View Description
Abstract: The strong-field picture of ionization describes the physics of how an isolated atom interacts with an intense ultra-fast laser field. The basic strong-field picture is described as tunnel ionization, which is characterized by the rapid burst of an electron wave packet into the continuum, followed by the classical motion of a quasi-free electron in a strong laser field and recollision with the parent ion. Recollision physics is at the very heart of what makes strong-field science an exciting tool for probing matter on ultrafast time scales. It offers a mechanism to create Attosecond (1 as = 10-18 s) laser pulses through High-Harmonic Generation and it offers a method for controlling electron-ion collisions on sub-femtosecond (1 fs = 10-15 s) time scales.

In my talk I will discuss how wavelength scaling has offered a more robust description of the strong-field picture. In particular, long wavelength lasers provide deep access to tunnel ionization and high energy electrons (several hundred eV) for studying electron recollision. I will discuss two separate aspects of my contributions that have helped to extend the strong-field picture. First, I will discuss inelastic laser driven scattering, or non-sequential ionization, in the long-wavelength limit of a 3.6 μm laser field. Here, large recollision energies (up to 400 eV) driven at modest field strengths result in the impact ionization of charge states up to Xe6+. The multiple ionization pathways are well described by a white electron wave packet and field-free inelastic cross sections, averaged over the intensity-dependent energy distributions for (e,ne) electron impact ionization. Then, I will discuss how wavelength scaling has made possible extending the strong-field picture of ionization to condensed phase systems. Here, we have observed evidence of a dramatic new mechanism for High Harmonic Generation that is unique to crystals yet closely parallels the semi-classical analysis of the strong-field atomic picture.
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Jan 10
Thursday

specpy: Simplifying Python-based beamline scripting

Speaker: Brian Toby
XSD Seminar
401/A1100 @ 12:00 PM
View Description
Part of the January 2013 Seminar Series Software for Beamlines. These talks present tools for beamline scientists using spec or python to control data collection or automate alignment or similar beamline tasks.
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Jan 9
Wednesday

Bent Crystal Optics for Synchrotron Radiation Beamlines

Speaker: Xianbo Shi, European Synchrotron Radiation Facility
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Bent crystals have been widely used as optical elements (e.g., monochromators, focusing optics and spectrometers) of high energy synchrotron radiation beamlines. The effects of bending on the reflectivity of the crystal are discussed within the dynamical theory with a full treatment of the crystal anisotropy and biaxial bending. Such knowledge and its combination with ray tracing and wave propagation are essential in the beamline design process. Two particular examples are presented to illustrate the usage of bent crystals for modern synchrotron radiation beamlines: the design of the X-ray Powder Diffraction (XPD) beamline at NSLS-II and the optimization of high luminosity spectrometers at ESRF and XFEL.

The XPD beamline uses a sagittally bent double-Laue crystal monochromator to provide horizontally focused x-ray beam over a large energy range (30-70 keV). A multi-lamellar model is introduced and implemented in the ray tracing of the monochromator. The instrumental resolution function of the beamline is also described.

Bent crystals are also utilized for high luminosity X-ray emission detection. This presentation will compare various concepts of dispersive/non-dispersive spectrometers with different crystal geometries by means of ray tracing.
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Jan 8
Tuesday

Controlling EPICS from Python: PyEpics

Speaker: Matt Newville
XSD Seminar
401/A1100 @ 12:00 PM
View Description
Part of the January 2013 Seminar Series Software for Beamlines. These talks present tools for beamline scientists using spec or python to control data collection or automate alignment or similar beamline tasks.
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2012

Nov 20
Tuesday

Sample Mounting & Sample Injection Workshop

XSD Workshop
PSI Paul Scherrer Institut SLS building
Nov 16
Friday

Fabrication of OSAKA MIRROR for Synchrotron Application

Speaker: Dr. Akihiko Ueda, JTEC Corporation
XSD Presentation
401/A1100 @ 3:00 PM
View Description
At JTEC Corporation we have been fabricating OSAKA MIRROR using EEM, nanofabrication, and RADSI and MSI, nano-measurement, of Osaka University. We explain our production technology, our potentiality and the mirrors we have delivered.

For your introduction of OSAKA MIRROR, we show our procedure from design process to fabrication and necessary points. In addition, we report on the development of our production technology.
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Nov 16
Friday

Recent Progress on Mirror-based Optical System for the 3rd and 4th Generation Synchrotron Radiation Sources

Speaker: Professor K. Yamauchi. Osaka University
XSD Presentation
401/A1100 @ 2:00 PM
View Description
We developed precision figuring and figure testing methods to realize nano-focusing mirror devices for synchrotron radiation hard X-rays [1]-[5]. The fabricated mirrors were tested at the 1km-long beamline (BL29-XUL) of SPring-8, and confirmed to realize nearly diffraction-limited focusing with the spot size less than 30nm at 15keV X-ray [6].

In recent research, we constructed an extremely precise optical system for hard-x-ray single-nanometer focusing also at BL29-XUL of SPring-8. Precision multilayer mirrors were fabricated, tested, and installed into an optical system for the single-nanometer focusing with a novel phase compensator. In the phase compensator, an at-wavelength wavefront error sensing method based on x-ray interferometry and in situ phase-compensator mirror, which adaptively deforms with nanometer precision, were developed to satisfy the Rayleigh’s quarter wavelength criterion to achieve diffraction-limited focusing in a single-nanometer range. The optical system developed was tested and confirmed to realize a spot size of approximately 7 x 8 nm2 [7] - [12]. I will talk about the ultimate focusing of the third generation synchrotron radiation x-rays at the size of single nanometer, together with a recent achievement of a microfocusing of Japanese X-ray free electron laser (SACLA)[13], a mirror-based optical system satisfying Abbe’s sine condition for nano-imaging[14][15], and an adaptive optical system for a versatile x-ray microscopy[16].

These researches were partially supported by Grants-in-Aid for the Specially Promoted Research, for the scientific research (S), for promotion of XFEL research, for CREST project, and for the Global COE Program “Center of Excellence for Atomically Controlled Fabrication Technology” from the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT).

References:
[1] K. Yamauchi et al., J. Synchrotron rad., 9 (2002), 313-316.
[2] Y. Mori et al., Rev. Sci. Instr., 71 (2000), 4627-4632.
[3] K. Yamauchi et al., Rev. Sci. Instr., 73 (2002), 4028-4033.
[4] K. Yamauchi et al., Rev. Sci. Instr., 74 (2003), 2894-2898.
[5] H. Mimura et al., Rev. Sci. Instr., 76 (2005) 045102.
[6] H. Mimura et al., Appl. Phys. Lett., 90 (2007), 051903.
[7] K. Yumoto et al., Rev. Sci. Instr., 77 (2006), 093107.
[8] H. Mimura et al., Phys. Rev. A, 77 (2008), 015812.
[9] T. Kimura et al., Jpn. J. Appl. Phys., 48 (2009) 072503.
[10] S. Handa et al., Jpn. J. Appl. Phys., 48 (2009) 096507.
[11] H. Mimura et al., Nature phys., 6 (2010) 122-125.
[12] K. Yamauchi et al., J. Phys. Condens. Matter., 23 (2011) 394206.
[13] K. Yumoto et al., submitted
[14] S. Matsuyama et al., Opt. Lett. 35 (2011) 3583-3585.
[15] S. Matsuyama et al., Opt. Exp., 20 (2012), 10310-10319.
[16] T. Kimura et al., to be submitted
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Nov 16
Friday

Escape Trajectories from Traditional Condensed Matter (With and Without the LCLS)

Speaker: Jerry Seidler, University of Washington
XSD Presentation
438/C010 @ 1:00 PM
View Description
We are entering a golden age of facility capability and user access for the preparation of extreme states of matter. While the campaign for inertial confinement fusion at the National Ignition Facility is both a major driver and a central highlight of this era, the entire achievable phase space of temperature, pressure, and magnetic field is rich with scientific opportunity in correlated electron physics, laboratory astrophysics, and fusion energy science. Here, I focus on the transition regimes from ‘traditional’ condensed matter to dense correlated plasma and ‘warm dense matter’ states. First, I will survey the physical phenomena already observed, already predicted, or that can be reasonably expected at temperatures up to 100 eV (1 million K) and pressures up to tens of megabars where surprising commonalities exist between contemporary issues in correlated plasma physics and those in condensed matter physics. Second, I will address the large uncertainties, ofte! n uncontrolled and under-appreciated, in basic material properties under such extreme conditions. These uncertainties propagate into the hydrodynamic simulations needed for planning and analysis of laser-shock compression experiments, and as such may pose a distinct technical barrier to achieving inertial confinement fusion. In this context, I will outline my group’s ongoing work at the APS aimed at providing a firm theoretical and practical foundation for sensing of temperature and pressure in warm dense matter and along the entire trajectory to fusion conditions.
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Nov 16
Friday

Superconducting Transition-Edge Sensors for X-ray Science

Speaker: Joel Ullom, NIST Boulder, Co
XSD Presentation
402/E1100 @ 10:00 AM
View Description
The maturity of superconducting transition-edge sensors (TESs) has increased dramatically in recent years. These devices can now provide x-ray resolving powers, E/ΔE, of 3x103 or higher. While the small size and low count rates of individual TESs have traditionally limited their applicability, arrays of TESs can overcome these constraints. Arrays of up to 104 elements are now in use for bolometric applications, arrays of up to 256 elements are in use for x-ray spectroscopy, and the recent introduction of microwave readout techniques has provided a technological path to arrays of 105-106 elements. Here, we review the status of TES technology, emphasizing developments at NIST. We describe potential applications in x-ray science including emission spectroscopy, Compton scattering, and time-resolved absorption spectroscopy. Finally, we show early results from a TES spectrometer recently deployed at the National Synchrotron Light Source.
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Nov 16
Friday

Pump Laser Workshop

XSD Workshop
PSI Paul Scherrer Institut Radiation protection building
Nov 13
Tuesday

Stress Accumulation and Damage Behavior of EB-PVD Thermal Barrier Coating Systems under Thermal Mechanical Fatigue Loading

Speaker: Marion Bartsch, Institute of Materials Research, German Aerospace Center, Germany
XSD Presentation
431/C010 @ 2:00 PM
View Description
Thermal barrier coatings (TBC) are applied on cooled gas turbine components. Between the heated and cooled surfaces a thermal gradient develops, resulting for constraint components in high multiaxial stresses, which may exceed stresses due to mechanical loading. In order to investigate the damage behaviour of TBC systems under close to reality conditions, thermal mechanical fatigue tests with controlled thermal gradients (TGMF-tests) were performed on coated tubular specimens. The specimen substrate was made from directionally solidified nickel base superalloy IN100 DS, and the coating system comprised a NiCoCrAlY bond coat and a ceramic top coat from partially stabilized zirconia. In TGMF testing specific damages occurred underneath the adherent ceramic top coat, evolving into fatigue cracks, which propagated primarily in the metallic bond coat parallel to the surface. To explain the initiation and evolution of these fatigue cracks, the thermo-mechanical response of the bond coat and the thermally grown oxide (TGO) between bond coat and ceramic top coat is examined and quantified through finite element analyses. The models include non-linear and time-dependent behaviour such as creep, TGO growth stress, and thermo-mechanical cyclic loading. The simulations suggest that stress redistribution due to creep can lead to tensile stresses in the TGO during TGMF testing that are large enough to initiate the cracks investigated.

It is planned to verify the models by means of in-situ synchrotron X-ray strain measurements at Argonne National Laboratory on coated TGMF-specimens with the same geometry and the same coating system as used in the initial tests performed at DLR but with a newly built TGMF- test facility.
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Nov 12
Monday

Inelastic X-ray Scattering with meV Energy Resolution

Speaker: Ayman Said, XSD/Inelastic X-ray & Nuclear Resonant Scattering Group
XSD Presentation
401/A1100 @ 2:00 PM
View Description
High-resolution inelastic scattering is a powerful tool to study atomic vibration of condensed matter on the atomic length scale. An overview of meV spectroscopy and the HERIX spectrometer in Sector 30 at the APS will be presented. This includes instrument capabilities and limitations, scientific applications as well as analyzer development for inelastic spectroscopy.
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Nov 6
Tuesday

Excited Charge Carriers in Nano Structures

Speaker: Dr. Detlef Diesing, Institute fur Physikalische Chemie, Universitat Duisburg Essen
XSD Presentation
431/C010 @ 11:00 AM
Nov 5
Monday

High Aspect Ratio Hard X-ray Zone Plates Fabricated with Ultrananocrystalline Diamond Molds and Electroplating

Speaker: Michael Wojcik, Illinois Institute of Technology
XSD Presentation
431/C010 @ 11:00 AM
View Description
X-ray zone plates are diffractive optics, similar to diffraction gratings but with changing pitch, where x-rays are diffracted to a common point with the focal spot size determined by the smallest zone width. Focusing efficiency is determined by the zone height and X-ray energy, while the maximum theoretical efficiency is limited by the various diffraction orders other than the focusing order. Also, focusing efficiency decreases with higher X-ray energy for a given zone plate but can be improved through fabricating thicker zones. A zone plate with high efficiency and resolution requires very high aspect ratio zones that pose many problems to fabrication. The challenge is to develop a fabrication method capable of overcoming the problems of high aspect ratio structures.

High aspect ratio zone plates can be fabricated by electroplating Au into a high aspect ratio dielectric mold. The mold material used for zone plate fabrication was ultrananocrystalline diamond (UNCD), which is a CVD diamond composed of 2-5 nm diamond grains bonded together. High aspect ratio structures were fabricated in UNCD by first patterning a mask and then etching the UNCD with reactive ion etching. The resulting mold was then filled with Au by electroplating. Zone plates with zone width of 60 nm and 1500 nm thick have been fabricated and other zone plates were successfully pushed past 2 microns while maintaining sub-100-nm zone width. Details of the fabrication method will be presented as well as characterization data of the zone plates. The data from the zone plates was then compared with simulations using models designed to be similar to fabricated zone plates.
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Nov 1
Thursday

Current Computed Tomography and Terahertz Efforts at NASA Glenn Research Center

Speaker: Dr. Don J. Roth, Optical Instrumentation and NDE Branch, NASA Glenn Research Center
XSD Presentation
401/A1100 @ 2:30 PM
View Description
This talk covers recent technical efforts in the X-ray micro-computed tomography (uCT) and terahertz areas at NASA Glenn Research Center. The first part of the talk will discuss the uCT work being done for the Advanced Stirling Radioisotope Generator program in which NASA is partnering with DOE, Lockheed-Martin, and Sunpower Corp. The focus of this program is to develop an ultra high efficiency, lower mass Stirling convertor for use with a radioisotope, reactor, or solar concentrator heat source for power on beyond-earth-orbit space missions. A high resolution micro-CT system has been assembled and is being used to provide optimal characterization for ultra-thin wall space components in this program. This talk will discuss many aspects of the development of the CT scanning for this type of component, including CT system overview; inspection requirements; process development, software utilized and developed to visualize, process, and analyze results; calibration sample development; results on actual samples; correlation with optical/SEM characterization; CT modeling; and development of automatic flaw recognition software. In the second part of the talk, the assembly of a terahertz system and its use in computed tomography and reflection modes for NASA thermal and environmental protection system materials will be briefly described. The THz tomography system can inspect samples as large as 0.0283 m3 (1 ft3) with no safety concerns as for x-ray computed tomography. The reflection mode THz capability is being investigated for use in simultaneously characterizing thickness and microstructural quality in coatings with the same set of measurements.
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Oct 10
Wednesday

Instrumentation Upgrades for the Macromolecular Crystallography Beamlines of the Swiss Light Source

Speaker: Martin Fuchs, MX Group, Swiss Light Source, Paul Scherrer Institute
XSD Presentation
436/C010 @ 10:00 AM
View Description
he varied demands from both challenging academic research projects as well as high throughput industrial applications on today’s macromolecular crystallography beamlines drive developments to both endstations and beamline optics. Recent instrumentation upgrades to the macromolecular crystallography (MX) beamlines of the Swiss Light Source therefore aimed to enhance both their performance as well as their reliability. A new unified diffractometer - the D3 - has been developed for the three MX beamlines. The first of the instruments is in general user operation at beamline X10SA since April 2012. Building upon and critically extending the developments realized for the high-resolution endstations of the two undulator beamlines X06SA and X10SA, as well as the super-bend dipole beamline X06DA, the new diffractometer was designed to the following core design goals: Redesign of the goniometer to a sub-micrometer peak-to-peak sphere of confusion for the horizontal single axis, for crystal sizes down to 5 microns. In addition it can accommodate the new multi-axis goniometer PRIGo (Parallel Robotics Inspired Goniometer). On-axis micro-spectrophotometer MS3 for microscopic sample imaging with one micron image resolution. The multi-mode optical spectroscopy module is always online and supports in-situ UV/Vis absorption, fluorescence and Raman spectroscopy. It is complemented by a complete off-line facility, the SLS SpectroLab, adjacent to the beamline. Further features are a rapid-change beam-shaping element system, a mineral cast support construction, the support for in-situ crystallization plate screening, close containment of the cryo-stream, and a minimum achievable detector distance of 120 mm for the Pilatus 6M detector. Concurrent to the upgrade of the experimental endstation, the doublecrystal monochromators (DCM) of the two undulator beamlines are being upgraded, with the aim to significantly speed up energy changes and reduce thermal drifts. By exchanging the motors of the Bragg angle axes for nanometer-resolution linear motors, the time for an energy sweep over the complete range from 6 to 20 keV was reduced to below 45s.
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Oct 8
Monday

X-ray Fluorescence Imaging and Metalloproteomics: Tying Images of Metals in Cells to the Proteins that Bind Them

Speaker: Lydia Finney, Microscopy Group, X-ray Science Division
XSD Presentation
401/A1100 @ 2:00 PM
View Description
Metals like copper, zinc and iron are important nutrients to all life. Their special properties which make them so useful to us in things like batteries and catalysts also make them useful to living organisms. Using hard x-ray fluorescence microprobes at the Advanced Photon Source, we have been able to see, often for the first time, where the metals themselves are inside cells and tissues. Yet, many of the images we acquire lead us to new questions. Are these metals required for the activity of proteins? Which proteins are binding which metals inside the cell? With over a third of all proteins thought to bind metals, knowing which metals are bound and how that binding changes in response to the environment could have big implications. For instance, the mismanagement of metals is involved in many diseases, including Lou Gehrig’s disease, Wilson and Menkes disease, and possibly even Alzheimer’s disease. Metals are also an environmental toxin, such as hexavalent chromium, and they are used in drugs, like the platinum in cisplatin that treats prostate cancer. In another vein, hexavalent uranium is an environmental contaminant of concern at several U.S. Department of Energy sites. The metal-binding proteins in microbes, such as those in the genus Shewanella, which can reduce uranium mobility in groundwater, play a major role in the beneficial activity of these organisms – and knowing which metal is in which protein at a given point in time could lead to new insights into how they do their work. We have developed a new tool to investigate this, combining native two-dimensional gel electrophoresis and x-ray fluorescence imaging, to quantitatively measure the amount of sulfur, iron, zinc, and other metals at every point of the 2-D separation of proteins. By coupling this with mass-spectrometry, we have identified a novel protein (PA5217) as a zinc-binding protein in P. aeruginosa. Our finding highlights how this method not only determines changes in metal occupancy, but also identifies the associated protein.
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Oct 8
Monday

Timepix Hybrid Pixel Detectors

Speaker: Josef Uher, Amsterdam Scientific Instruments
XSD Presentation
431/C010 @ 11:00 AM
View Description
Amsterdam Scientific Instruments (ASI) is as spin-off company of Nikhef (The Dutch National Institute for Subatomic Physics). ASI focuses on development and applications of novel hybrid pixel detectors Timepix. Timepix detectors belong to the family of Medipix imaging detectors that were developed in an international collaboration "Medipix" lead by CERN. Timepix detectors consist of a pixelated sensor (typically 300µm thick Si) and readout ASIC chip. The pixel size is 55x55µm2 and the detector currently exists in two versions with 256x256 or 512x512 pixels. Pixels can be operated either in counting mode (up to 105 counts/s), in Time-Over-Threshold mode allowing measurement of energy deposited in each pixel or in Time-Of-Arrival mode for Time-Of-Flight applications. The talk will focus on description of the device and its applications. The capability of Timepix to discriminate or measure energy of incoming radiation in each pixel opens new possibilities such as material resolved X-ray imaging and tomography. The device could be also modified for neutron imaging. Other applications range from alpha particle detection, through proton tracking up to dosimetry in space.
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Oct 1
Monday

Relationship between Morphology and Property of Laser Synthesized Nanostructured Materials

Speaker: Nozomi Shirato, University of Tennessee
XSD Presentation
431/C010 @ 11:00 AM
View Description
Synthesis of well-defined nanostructures by pulsed laser melting is an interesting subject from both a fundamental and technological point of view. The resulting structures have potential applications related to their magnetic, optical, plasmonic, and magneto-optical properties. Focus of this talk will be on synthesis and functional properties of 1D periodic SnO2 nanostructured arrays which have applications in hydrogen gas sensing. Results from experimental observations, theoretical modeling and hydrogen sensor evaluation will be discussed. Ferromagnetic Co nanowire and nanomagnets are important in understanding magnetism in the nanoscale. I will focus on synthesis and characterization of these magnetic nanostructures using the pulsed laser process. The magnetic anisotropy was studied by using a home-built SMOKE (Surface magneto-optical Kerr Effect) system complemented with magnetic force microscopy (MFM) analysis.
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Oct 1
Monday

Nanoscale Heterogeneity in Local Structure and Dynamics of Materials using Neutrons, X-rays and AMD

Speaker: Bachir Aoun, Institut Laue Langevin
XSD Presentation
433/C010 @ 11:00 AM
Sep 27
Thursday

Understanding the State of Polycrystalline Engineering Alloys and Components using High Energy Synchrotron X-ray

Speaker: Jun-Sang Park, Cornell University
XSD Presentation
401/A1100 @ 11:00 AM
View Description
As the demand for efficient, high‐performance machines increases, quantifying the state of materials and understanding their micro‐mechanical behavior are ever more important for designing and building these machines. High energy synchrotron radiation is an attractive tool for investigating the state and the micromechanical behavior of polycrystalline structural alloys. In this talk, two techniques will be presented. In the first part of the talk, a framework for understanding the micromechanical behavior of individual crystals embedded in a polycrystalline aggregate is described. This framework combines the synchrotron x‐ray experiments and polycrystal finite element simulation to understand the micromechanical behavior. A method for simulating diffraction spots from individual virtual crystals using the information obtained from a polycrystal finite element simulation is described. To demonstrate the method, a set of high energy diffraction data were collected while applying a uniaxial tension on a high strength copper specimen. The diffraction data were analyzed to determine the orientations and the stresses of the crystals in the diffraction volume. The crystal orientations were used to instantiate a virtual polycrystal and a slip‐based polycrystal finite element simulations were performed. Using the information obtained from the finite element simulations, a set of virtual diffraction spots is generated. These virtual diffraction spots are compared to the experimental diffraction spots. In the second part of the talk, a method for quantifying the residual stress field in a polycrystalline material is presented. An experimental setup that combines monochromatic high energy x‐ray diffraction and a set of conical slits is described. The set of conical slits allows the non‐destructive measurement of lattice strains for diffraction volumes located inside the material and is used to measure the strain pole figures (SPFs) for diffraction volumes located inside a polycrystalline component. Full three‐dimensional residual stress field is determined by a bi‐scale optimization scheme. In this scheme, the residual stress field satisfies the SPF measurements at the crystal length scale. At the macroscopic length scale, the residual stress field satisfies equilibrium and imposed boundary conditions of the component. To demonstrate the new method, a polycrystalline shrink‐fit sample with a three‐dimensional stress gradient was manufactured from a low solvus high refractory (LSHR) Ni‐based superalloy. The residual stress field determined using the new method compares favorably with an analytic approximation of the stresses within the shrink‐fit sample.
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Sep 19
Wednesday

Processing Tevatron Data Around the World: Lessons Learned

Speaker: Adam Lyon, Scientific Computing Division, Fermilab
XSD Presentation
431/C010 @ 10:00 AM
View Description
The Tevatron experiments have been processing enormous amounts of data worldwide for over 12 years. This talk will center on the challenges, and some solutions, to data management through collection and analysis by distributed teams. The difficulties are easy to underestimate, and surprises have continued to emerge throughout the ongoing effort.
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Sep 10
Monday

Pressure-tuned Quantum Phase Transitions in Correlated Electron Systems

Speaker: Yejun Feng, Magnetic Materials Group
XSD Presentation
401/A1100 @ 2:00 PM
View Description
Correlated electron systems are the impetus of modern materials science and technology. Functionally important materials such as rare-earth magnets, high-temperature superconductors, giant/colossal magnetoresistance materials, heavy fermions, transition metal sulfides and oxides, and ferroelectrics, are all derived through intertwined charge, spin, orbital, and phonon degrees of freedom. From about two decades ago, the language of quantum phase transition and its associated quantum critical phenomena was formally developed to provide a platform for studying emergent states and exotic phases of materials when a system is fine-tuned away from its ambient condition state. Experimental tuning methods are typically athermal and include techniques such as chemical doping, magnetic and electrical fields, and pressure. Among those, pressure is considered a clean technique as it does not break the time reversal symmetry, and also in principle limits the increasing disorder and change of local chemical environment. Here I discuss quantum critical phenomena in several examples of pressure-tuned incommensurate density wave systems. Using x-ray single crystal diffraction, we were able to directly probe order parameter fluctuations near a buried quantum critical point.
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Sep 6
Thursday

Photolysis Study of CO-Nitrogenase by FT-IR and Nuclear Resonant Vibrational Spectroscopy and Nuclear Resonant Microscopy Development

Speaker: Lifen Yan, X-ray Science Division
XSD Presentation
431/C010 @ 11:00 AM
View Description
Nitrogenase is the enzyme which catalyzes the “nitrogen fixation” process that turns N2 into NH3. It is a critical key in the global nitrogen cycle. Carbon monoxide (CO) is an inhibitor to most of the substrates of Nitrogenase. By employing its photolability, we have studied the structure and dynamics of CO bound to nitrogenase. FT-IR spectroscopy has been used to study the photochemistry of CO-inhibited Azotobacter vinelandii MoFe nitrogenase, using UV-Vis light to photolyze the CO at cryogenic temperatures. With the wild-type and variant enzymes, three distinct photolabile Hi-CO species were observed, and turned into three distinct Lo-CO species separately upon photolysis. Each Hi-CO ↔ Lo-CO pair has a different photolytic behavior, and different temperature dependent recombination dynamics. Different structures were assigned with the assistance of normal-mode calculations. Nuclear resonant vibrational spectroscopy (NRVS) has the unique advantage of probing nuclear isotopes (e.g. 57Fe) in complicated enzymes. It provides local information of dynamics at the Fe site and gives 57Fe partial vibrational density of states. We have combined UV-Vis photolysis with NRVS to study CO-nitrogenase with promising results.

Recent developments of synchrotron nuclear resonant microscopy at sector 3 at APS will also be discussed. Proof-of-principle experiments were performed with prepared 57Fe phantoms and 5 μm spatial resolution. At a certain spot, the hyperfine interactions could be revealed from the decayed time spectrum in the forward scattering, and the phonon density of states could be obtained with the NRVS signal in the 4π scattering. Selected meteorite samples were successfully imaged. The potential application to biological samples is under development.
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Sep 5
Wednesday

Probing Electronic Phase Transitions with Phonons via Inelastic X-ray & Neutron Scattering

Speaker: Frank Weber, Karlsruhe Institute of Technology
XSD Forum
438/C010 @ 12:00 PM
View Description
Phonon measurements via inelastic scattering in solid state materials exhibiting electronic phase transitions using hard x-rays as well as thermal neutrons will be the subject of this talk. After a short discussion of the general behavior of phonons in solids the focus will be on the analysis of experimental data using (not performing) modern ab-initio calculations for the electronic structure and the lattice dynamical properties based on density-functional-perturbation-theory (DFPT). The discussion will include properties of the electronic contribution to the phonon line width and its relation to the electronic structure and the so-called electron-phonon coupling matrix element. The concepts of phonon renormalization at electronic phase transitions will be demonstrated by examples of recent work done in our group at the Karlsruhe Institute of Technology.
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Sep 5
Wednesday

Coherent X-Ray Diffraction Imaging in the Surface Reflection Geometry

Speaker: Chenhui Zhu, Materials Science Division, Argonne National Laboratory
XSD Presentation
401/A1100 @ 11:00 AM
View Description
In this talk, I will cover two separate topics. First, I will introduce several novel ferrroelectric liquid crystal phases, including (a) ferroelectric orthogonal smectic phase of the highest symmetry yet discovered [1], which exhibits sub-microsecond fast switching under electric field; (b) polarization modulated phase, discovered the first time in nontilted smectics [2], exhibits hysteresis switching due to polarization stripe boundaries rather than the typical surface stabilized mechanism; (c) chiral nano-filament phase formed out of achiral molecules. Such nanofilaments are found to form porous network [3], when mixed with organic molecules such as 8CB, P3HT and PCBM. It may serve as a matrix for promoting nano-phase segregation of guest organic molecules, which is important in organic photovoltaics. (d) de Vries smectics, which exhibits no layer thickness shrinkage when going through the SmA-SmC transition, and thus eliminate the defect problem in ferroelectric LCD. Two popular models will be discussed. In the second part of the talk, I’ll describe our recent effort in applying coherent xray diffraction imaging (CDI) in surface reflection geometry to achieve higher resolution. Typical CDI has two limitations: (a) the requirement for an isolated object (beam size > object), and (b) the spatial resolution achieved so far is still far from x-ray wavelength. In order to investigate extended surface, we apply ptychography technique [4] to Bragg CDI [5]. One interesting sample is the platinum single crystal surface with atomic steps [6]. The step height variation in reflection geometry is essentially a phase object, and the contrast is maximized at the anti-Bragg condition. Our simulation has shown that height variation comparable to the x-ray wavelength can be reconstructed. Preliminary experimental data on platinum surface and attempt for ptychography reconstructions will be discussed.
[1] R. Reddy, C. Zhu, R. Shao, E. Korblova, T. Gong, Y. Shen, E. Garcia, M. Glaser, J. Maclennan, D. Walba, N. Clark, Science 332, 72 (2011).
[2] C. Zhu, R. Shao, R. Reddy, D. Chen, Y. Shen, T. Gong, M. Glaser, E. Korblova, P. Rudquist, J. Maclennan, D. Walba, N. Clark, J. Am. Chem. Soc. 134, 9681 (2012).
[3] C. Zhu, D. Chen, Y. Shen, C. Jones, M. Glaser, J. Maclennan, N.Clark, Phys. Rev. E 81, 011704 (2010); D. Chen, C. Zhu, R. Shoemaker, E. Korblova, D. Walba, M. Glaser, J. Maclenna, N. Clark, Langmuir 26, 15541 (2010).
[4] M. A. Pfeifer, G. J. Williams, I. A. Vartanyants, R. Harder, I. K. Robinson, Nature, 442, 7098 (2006).
[5] P. Thibault, M. Dierolf, A. Menzel, O. Bunk, C. David, F. Pfeiffer, Science, 321, 379 (2008).
[6] H. You, M. Pierce, V. Komanicky, A. Barbour, C. Zhu, Electrochimica Acta, In press
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Aug 30
Thursday

Exploring Molecular-Scale Surface Phenomena Utilizing Spin-averaged & Spin-polarized SYM-analysis Techniques

Speaker: Marvin Cummings, Getty Conservation Institute
XSD Presentation
431/C010 @ 11:00 AM
View Description
Molecules adsorbed at noble and transition metal surfaces induce a rich set of modified electronic, chemical, magnetic, and dynamic properties at the surface. These modified surface properties make molecule-metal substrate systems viable in spin-dependent molecular-switching applications, as possible molecular machinery, and in gas-sensing technologies. What governs functionality in these systems is two-fold: i) the interactions and behavior of the molecule at the molecule-metal substrate interface and ii) the ability to scale and control molecular-arrangements at the metallic surface. In this talk, the interactions of C60-molecules deposited on the Co/Ru(0001) thin film surface will be discussed, showing the impact of the Co/Ru(0001) thin film electronic and atomic structure on C60-behavior at the surface, and inversely the influence of C60 on Co thin film epitaxial growth. Finally, the role magnetism might play in affecting molecule-substrate and molecule-molecule interactions at the metal surface will be explored.
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Aug 29
Wednesday

Templated Growth of Biominerals: Charge, Epitaxy, and Sterochemistry

Speaker: Benjamin Stripe, Northwestern University
XSD Presentation
431/C010 @ 10:00 AM
View Description
Living creatures have the ability to control the orientation and morphology of a wide range of biominerals. Research on the growth of biominerals using biomimetic templates has demonstrated the ability of different templates to grow crystals with varying orientations and morphologies. The simplest templates are made of ordered hydrocarbon chains with functional terminal groups such as acids, alcohols, and sulfates. There are currently three main theories for how biomimetic templates control the orientation of nucleating crystals: charge balancing, epitaxial growth and stereochemical matching. Using grazing incidence x-ray diffraction from Langmuir monolayers, on supersaturated solutions of CaCO3, we have been able to monitor both the template and nucleating calcite crystals in situ. These studies have made it possible to probe current theories of biomimetic templated growth, and have demonstrated that the average template lattice is the primary controlling factor in the growth of uniform oriented calcite crystals.
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Aug 27
Monday

Applications of In Situ Diffraction Techniques in Piezoelectric Materials

Speaker: Goknur Tutuncu, University of Florida
XSD Presentation
431/C010 @ 11:00 AM
View Description
X‐ray and neutron scattering are among the most versatile techniques for in situ measurements of dynamic atomic structures. This versatility results in part from the ease with which environmental and loading devices can accommodate diffraction geometry, coupled with its rapid and sensitive data acquisition. When high‐energy diffraction methods are utilized, in particular, improved penetration depths allow for intimate material responses to external stimuli to be monitored with excellent precision. Here, two case studies employing such advanced diffraction techniques designed to answer fundamental questions in materials science are presented, and the ability of these techniques to yield new insights into material behavior is discussed. In the first example, a high‐energy X‐ray diffraction technique was developed to directly observe template‐matrix interactions during templated grain growth (TGG) of a promising piezoelectric ceramic, (K,Na)NbO3 (KNN). A detailed understanding of the contribution of template particles to the phase and texture evolution of the bulk KNN was obtained, and this information was used to understand microstructure control during the sintering process. In the second case study, the origin of enhanced property coefficients and electromechanical coupling in piezoelectric ceramics at compositions near morphotropic phase boundaries (MPBs) is investigated using time‐resolved X‐ray and neutron scattering methods. Time‐resolved diffraction data was collected at various subcoercive electric field amplitudes and frequencies in order to determine the contribution of extrinsic and intrinsic mechanisms topiezoelectric coefficients at these technologically interesting MPB compositions.
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Aug 23
Thursday

Disordered Material Structure using Advanced Pair Distribution Function Methods

Speaker: Lawrie Skinner, Stony Brook University
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Pair distribution function (PDF) measurements are becoming increasingly routine for structural studies of disordered, complex, and nano-crystalline materials. However I am primarily interested in extending these methods to enable us to gain more structural insight into amorphous and complex crystalline materials. In this talk I will introduce some of the key science motivations for studying the structure of amorphous materials, and will discuss a few directions in which I have been pushing these PDF methods, with examples of the new science that was enabled.
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Aug 22
Wednesday

Waveguide-based Holographic X-ray Imaging at the Coherence Beamline P10 of PETRA III/DESY

Speaker: Sebastian Kalbfleisch, Georg-August-Universitat, Gottingen Institut fur Rontgenphysik
XSD Presentation
401/A1100 @ 10:00 AM
View Description
The presented concept of inline holographic imaging is based on the highly coherent and divergent beam emitted by an X-ray waveguide. The combination of holographic reconstruction methods with iterative algorithms is capable of suppressing the twin image occurring in inline holography. I will present the dedicated holographic imaging endstation installed at the Coherence Beamline P10 of PETRA III. Recent results of test structures and biological samples obtained this endstation will be shown.
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Aug 17
Friday

Materials Structural Analysis Using X-ray Surface Scattering and Imaging Techniques

Speaker: Tao Sun, X-ray Science Division
XSD Presentation
431/C010 @ 1:00 PM
View Description
The demand for miniaturization of electronic, magnetic, and photonic functional units has stimulated intense research activities in fabrication and structural characterization of substrate-supported nanostructures. X-ray surface scattering and imaging are among the very limited techniques that provide quantitative structural information of such samples, particularly on their dynamic structural evolution upon external conditions. The first part of my presentation will cover topics on some critical issues associated with structural characterization of oxide nanostructures confined to one dimension (i.e. nanolines) and two dimensions (i.e. thin films). The structural attributes in such systems include nature of nucleation/growth given the thermal and kinetic constraints, porosity evolution given the shrinkage and its accommodation in nanoscale systems, substrate/strain owing to their influence on sign and magnitude in the context of spatial and dimensional constraints. Specifically, in situ grazing-incidence small-angle x-ray scattering and scanning x-ray nanodiffraction techniques were extensively used for quantitatively characterizing the microstructures of sol-gel derived oxide thin films and surface patterns. The second part of my presentation will be focused on the development of a novel x-ray surface imaging technique, termed coherent surface scattering imaging (CSSI). CSSI synergistically combines coherent diffractive imaging and the grazing-incidence scattering geometry near sample total external reflection. I will show in this talk that CSSI is capable of providing not only planar images of sample surface structures, but also three-dimensional structural information with nanometer resolution in the surface normal direction. My research work underscores the need for quantitative understanding of structural underpinning in the mechanisms and behavior of surface nanostructures, and highlights the role of advanced synchrotron x-ray scattering/imaging approaches.
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Aug 9
Thursday

Using Resonant and Anomalous X-ray Diffraction to Probe Electrons at

Speaker: Ken Finkelstein, CHESS & Cornell Laboratory for Accelerator-Based Sciences and Education
XSD Seminar
432/C010 @ 9:15 AM
View Description
We report results of several experiments, conducted at APS 7ID, where 50-femtosecond, 800-nm (1.55 eV) laser pulses are synchronized to overlap at the sample, in space & time, with x-ray pulses. We studied diffraction at three types of reflections in germanium, tuning x-ray energy very close to the K-edge at 1.104 KeV. The reflections studied were: allowed by the rules of the space group, forbidden, or VERY forbidden. Forbidden means scattering from spherically symmetric atoms, occupying certain “special positions,” will cancel out. VERY forbidden means that general symmetry properties (glide planes or screw axes) lead to cancellation of reflection even when atomic charge density is not spherical. The allowed reflections studied are ALMOST cancelled by tuning x-ray energy just below the K edge. Under this condition, the signal appears to be very sensitive to scattering from valence electrons, and it is profoundly perturbed by the laser. We discuss the physics of this effect and compare to diffraction measured at both types of forbidden reflections. Diffraction at the “forbidden” reflections is well known to be sensitive to valence electrons and is fairly insensitive to x-ray energy. Signal at “VERY forbidden” reflections is measureable only at resonance; i.e. in a very narrow energy band associated with the K-absorption edge. We describe the connection between scatterings in these three cases, discuss effect of the laser, and speculate on why all this may be important.
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Jul 9
Monday

Discussion of Software Needs in XSD

Speaker: Brian Toby and Chris Jacobsen
XSD Presentation
401/A1100 @ 2:00 PM
View Description
Data that are not sufficiently examined during collection may be discovered as incomplete or faulty, but too late for this to be addressed. Improvements in APS capabilities are leading to a data deluge; where is the corresponding deluge in software for cataloging, reducing and analyzing these data? We will discuss paths forward, including current mechanisms for completion of scientific programming tasks, how to interact with Mathematics and Computer Science and their computing facilities at Argonne, and how to move forward from white papers to a proposal for the Director's Grand Challenge in Data-Driven Science.
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Jul 5
Thursday

Generation and Propagation of Coherent X-rays: High Order Harmonic Generation and Amplified Spontaneous Emission

Speaker: Ji-Cai Liu, North China Electric Power University
XSD Presentation
401/A1100 @ 11:00 AM
View Description
There have been continuous efforts aimed at developing x-ray lasers at shorter and shorter wavelengths in the history of lasers. We consider the possibility of hard x-ray emission employing below-threshold harmonic generation in the non-tunneling regime of high-order harmonic generation. The interaction of a tightly bound valence electron in a highly charged ion with an intense extreme ultraviolet laser radiation is investigated in the weakly relativistic regime by solving numerically the two-dimensional Schrödinger equation based on the single active electron approximation. Harmonics below the ionization energy of the tightly bound system are emitted with much higher efficiency than harmonics of a loosely bound system in the tunneling ionization regime for the same photon energy. Below threshold harmonics thus offer a new way towards coherent hard x rays.

Another strategy to produce strong-field coherent x-ray lasing is to use an x-ray free-electron-laser to create a population inversion in a medium that then lases in the x-ray regime. We predict x-ray lasing upon pumping molecules into dissociative core-excited states by an XFEL pulse. Lasing occurs in the core-excited neutral dissociation product that is in a state of population inversion. Calculations performed for the HCl molecule pumped at the 2p1/2 → 6σ resonance demonstrate that the suggested scheme can be used to create ultrashort coherent x-ray pulses with transform limited spectral width.
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Jun 26
Tuesday

Structure-Property Relationship in Metal-Organic Frameworks for Enhanced Energy Related Applications

Speaker: Dorina F. Sava, Sandia National Laboratory
XSD Seminar
433/C010 @ 10:30 AM
View Description
The research is focused on gaining a fundamental understanding of the chemical environment of host-guest interactions in crystalline porous materials (zeolites and metal-organic frameworks). We utilize an integrative approach involving solvothermal synthesis, molecular simulations (GCMC and MD), materials characterization, and local and long-range structural probes (differential pair distribution function (d-PDF) and X-ray diffraction). Two examples in which structure-property relationship studies of MOFs are used in energy related applications will be discussed: (1) the selective capture and storage of volatile gases in MOFs; (2) novel MOFs with distinct photoluminescence (PL) properties.
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Jun 25
Monday

Watching Chemistry in Action: Probing Ultrafast Chemical Dynamics by Time-Resolved Photoelectron Imaging

Speaker: Daniel Rolles, Max Planck Advanced Study Group, Center for Free-Electron Laser Science (CFEL)
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Taking a movie of a chemical reaction with atomic resolution? Watching the making and breaking of chemical bonds in real time? The successes of the world’s first VUV and X-Ray Free-Electron Lasers (FELs) FLASH at DESY in Hamburg and LCLS at SLAC in Stanford together with the continuing technical advances in the creation of (su femtosecond VUV pulses by high harmonic generation (HHG) have turned the once lofty vision of “recording a molecular movie” with femtosecond temporal and atomic scale structural resolution into a realistic scenario.

By means of femtosecond pump-probe experiments with intense and short-pulse VUV and X-ray FEL radiation, our goal is to establish and further develop the experimental techniques capable of imaging photochemical reactions in gas-phase molecules in order to study exemplary reactions of chemical relevance with the aim to clarifying their pathways.

I will present results from exemplary photoelectron diffraction and Coulomb explosion-imaging studies on adiabatically laser-aligned [1] and mixed-field oriented carbonyl sulfide, dibromobenzene, and p-fluorophenylacetylene molecules recorded after inner-shell photoionization. The experiments were performed with a double-sided velocity map imaging (VMI) spectrometer installed in the CFEL-ASG MultiPurpose (CAMP) chamber [2], which allowed recording electron and ion distributions at the same time. Through comparison with multiple scattering calculations [3], the measured photoelectron diffraction images can be related to the geometric structure of the molecules. In a second step, time-resolved photoelectron diffraction patterns of laser-aligned molecules were recorded by dissociating the molecules with a femtosecond infrared (IR) laser pulse prior to the FEL ionization and varying the delay between IR pump and FEL probe pulse. Time-dependent changes are observed in both electron and ion distributions.
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Jun 18
Monday

2012 Annual NUFO Meeting

XSD Conference
Los Alamos National Laboratory (LANL), in Los Alamos, New Mexico
Jun 15
Friday

X-ray Resonance Fluorescence and Rabi Flopping for Ultrafast and Intense Pulses

Speaker: Stefano Cavaletto, Max Planck Institute for Nuclear Physics
XSD Seminar
401/A1100 @ 2:00 PM
View Description
Resonance fluorescence is scattering of photons off atoms and molecules driven by a near-resonant external electric field. For intense x-rays from existing and upcoming X-ray Free-Electron Lasers (XFELs), such as the Linac Coherent Light Source (LCLS), the cyclic excitation and induced decay of a core electron (Rabi flopping) can compete with spontaneous core-hole decay. We develop a two-level description of x-ray resonance fluorescence and exemplify it for neon cations strongly driven by LCLS light tuned to the 1s 2p -1 → 1s -1 2p transition at 848 eV. We first consider chaotic pulses generated at present-day LCLS and, second, regular pulses which will become available soon with self-seeding techniques.

We further extend our x-ray-only model by adding a third level coupled by an optical laser. We consider the particular cases of a Ξ- or a Λ-model and study the influence of a time-dependent optical laser over the x-ray resonance fluorescence spectrum emitted by a three-level system.
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Jun 11
Monday

Toward Microscopy with Direct Electronic and Chemical Contrast at the Atomic Level

Speaker: Volker Rose, XSD / MIC
XSD Presentation
401/A1100 @ 2:00 PM
View Description
In this talk we will discuss the development of a novel high-resolution microscopy technique for imaging of nanoscale materials with chemical, electronic, and magnetic contrast. It will combine the sub-nanometer spatial resolution of scanning tunneling microscopy (STM) with the chemical, electronic, and magnetic sensitivity of synchrotron radiation. [1] Drawing upon experience from a prototype that has been developed to demonstrate general feasibility, current work has the goal to drastically increase the spatial resolution of existing state-of-the-art x-ray microscopy from only tens of nanometers down to atomic resolution. The technique will enable fundamentally new methods of characterization, which will be applied to the study of energy materials and nanoscale magnetic systems. A better understanding of these phenomena at the nanoscale has great potential to improve the conversion efficiency of quantum energy devices and lead to advances in future data storage applications. The combination of the high spatial resolution of STM with the energy selectivity afforded by x-ray absorption spectroscopy provides a powerful analytical tool.

[1] V. Rose, J.W. Freeland, S.K. Streiffer, "New Capabilities at the Interface of X-rays and Scanning Tunneling Microscopy," in Scanning Probe Microscopy of Functional Materials: Nanoscale Imaging and Spectroscopy, S.V. Kalinin, A. Gruverman, (Eds.), Springer, New York (2011), pg 405-432.
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May 22
Tuesday

Using Electronic Coherence to Probe a Deeply Embedded Quantum Well in Bimetallic Pb/Ag Films on Si(111)

Speaker: Dr. Matthew Brinkley
XSD Presentation
438/C010 @ 11:00 AM
View Description
Angle-resolved photoemission studies of Pb films prepared on atomically uniformAg(111) films reveal a striking Fabry-Pérot-like behavior typical of a high-finessePb/Ag/Si(111) electron interferometer. Remarkably, the quantized electronic structure of the underlying Ag films persists despite Pb overlayers much thicker than the photoemission escape depth and an incommensurate Pb/Ag interface. Comprehensive simulations clearly illustrate the manifest coherence of the electronic structures, permitting the characterization of the deeply embedded Ag quantum well. This demonstrated exploitation of electronic coherence will prove useful to applications requiring non-invasive access to buried structures.
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May 18
Friday

Quantum Size Effect in Novel Two-dimensional Electron Systems

Speaker: Dr. Yang Liu
XSD Presentation
438/C010 @ 11:00 AM
View Description
Two-dimensional ultrathin films often exhibit properties dramatically different from their three-dimensional bulk counterparts, due to quantum confinement effect in reduced dimension. In this talk, I will first present our recent study of electronic properties of epitaxial graphene layers, using angle-resolved photoemission spectroscopy (ARPES) with variable light polarizations. Our results demonstrate that the "chiral" electronic states in this two-dimensional system can be unambiguously revealed by this technique. Next I will report our current research progress in quantum confinement effects in ultrathin films of topological insulators (TIs), using ARPES and surface X-ray scattering (SXS). Due to a largely enhanced surface-to-bulk ratio, TI ultrathin films are considered to be a very promising system for practical applications of TIs. It is therefore crucial to understand how the electronic and structural properties in TI thin films converge to their bulk limits. For ultrathin Bi2Te3 films grown on Si(111), we found that the topological surface state converges to its bulk form already at 4 quintuple layer, in remarkable agreement with theoretical prediction for a freestanding film. Our surface X-ray study confirms that the quasi-freestanding Bi2Te3 films are achieved through a buffer layer between the film and substrate, which effectively saturate the dangling bonds of the Si(111) substrate. Finally, if time permits, I would also like to present our recent results on the novel tri-layer growth of ultrathin indium films, using ARPES and SXS.
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May 14
Monday

Nanoscale Motion and Bulk Rheology in Complex Fluids

Speaker: Suresh Narayanan, XSD/TRR
XSD Presentation
401/A1100 @ 2:00 PM
View Description
Complex fluids which encompasses colloidal and nanoparticle suspensions, polymers, nanocomposites, gels, emulsions, etc. exhibit rich viscoelastic behavior over hierarchical structural length scales and a wide range of dynamical time scales. Typically the bulk rheology in such systems are of importance for potential applications. X-ray photon correlation spectroscopy has been successfully used to probe nanoscale dynamics in such systems. In this talk, I will present a few science cases that aim at connecting the motion at nanoscale with bulk rheological properties.
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May 14
Monday

GE Digital Detectors for X-Ray Diffraction

Speaker: Susanne M. Lee, GE Global Research, Photonics Laboratory
XSD Seminar
401/A5000 @ 10:00 AM
View Description
The development of next generation medical and industrial x-ray analysis techniques have been hindered by a paucity of photon flux emitted by laboratory-based x-ray sources. To address this, GE has developed a class of vacuum-compatible multilayer x-ray photonic devices that, in theory, can concentrate up to 2π steradians of high-energy photons (>60keV) from a laboratory source and redirect them into pre-specified spatial and spectral beam shapes. In this presentation, the theoretical design of these photonic devices, which require x-ray reflectivities (XRR) better than 99.9% from the multilayer components, will be discussed. High-energy experimental XRR data on these unusually high-reflectivity multilayers will be shown. During the development of these x-ray photonic devices, x-ray reflectivity and diffraction were performed with GE’s sensitive, high-dynamic range, digital x-ray detectors. These non-medical applications presented different imaging requirements than the medical applications for which the detectors were originally designed and manufactured. This presentation will also contain a discussion on the detector design and how to take advantage of it to obtain optimal detector performance at low (~8keV) and high (~60keV) x-ray energies for x-ray diffraction and other x-ray imaging
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May 5
Saturday

X-rays in the Fourth Dimension

XSD Conference
Park Hyatt Chicago, Chicago
View Description
Relative to space, the dimension of time has been underexploited in x-ray science. Interesting phenomena span a hierarchy of time scales, and the advent of new x-ray facilities bring a broad range of capabilities. The goal of this workshop is to assess the worldwide portfolio of x-ray sources and identify classes of experiments best done at complementary facilities (synchrotrons and FELs) so that researchers can be informed about present and planned capabilities. Attendees will "brainstorm" about potential time-resolved experiments in materials; chemistry; condensed matter physics; atomic, molecular, and optical physics; and more. A summary report will be prepared.
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Apr 26
Thursday

Pixel Detectors: New Developments

Speaker: Christian Bronnimann
XSD Presentation
401/A1100 @ 11:00 AM
Apr 23
Monday

Studies of Molecular Bonding by Inelastic X-ray Scattering

Speaker: Professor Keijo Hamalainen, University of Helsinki, Finland
XSD Forum
401/A1100 @ 11:30 AM
View Description
Pizza will be served
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Apr 19
Thursday

Layered Ruthenates and Iridates: A Novel Playground for Correlated Electrons

Speaker: Shalinee Chikara, University of Kentucky
XSD Presentation
431/C010 @ 11:00 AM
View Description
The 4d and 5d transition metal oxides exhibit many exciting phenomena like ferroelectricity, ferromagnetism, antiferromagnetism, meta-magnetism, metal-insulator transition and superconductivity. The ruthenium and iridium oxides are expected to be more metallic and less magnetic than the 3d and 4f oxides because of the extended nature of the 4d and 5d orbitals. In marked contrast, many ruthenates and iridates are magnetic insulators that exhibit a large array of phenomena not usually seen in other materials. In this talk, I focus on the anomalous physical properties and novel phenomena exhibited by these materials. These include novel borderline magnetism and spinvalve effect in ruthenates, and a novel Jeeff= 1=2 insulating state inthe iridates.
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Apr 17
Tuesday

1K Frame Transfer Fast CCD collaboration with LBNL

Speaker: John Weizeorick
XSD Forum
431/C010 @ 9:30 AM
Apr 9
Monday

Pulse Duration Measurements at LCLS

Speaker: Gilles Doumy, XSD/AMO
XSD Presentation
401/A1100 @ 2:00 PM
View Description
The Linac Coherent Light Source (LCLS) at SLAC has been the first x-ray Free Electron Laser (XFEL) in operation. By providing x-ray pulses with incomparable peak brightness, it opened a new era in x-ray physics. Typical characteristics, available from the soft x-ray to the hard x-ray region (500eV-10000eV), amount to approximately 1012 photons per pulse, in a time believed to be as short as a few tens of femtoseconds (10-15 s). Measuring the exact pulse duration of the x-ray pulses has been a challenge from the start, due to a lack of existing techniques capable of accessing that information. The situation is rendered even more complex by the fact that LCLS lasing is based on SASE (Self Amplified Stimulated Emission), which essentially means that every pulse starts from random noise, producing in the end a purely chaotic source. Ideally, a pulse duration characterization requires a single shot measurement capability. While a lot can be learned from measurements done on the electron beam, as well as from a statistical analysis of the pulse energy and high-resolution spectrum of x-ray pulses, ultimately it is necessary to measure each x-ray pulse itself. I will present attempts to realize that by using the technique known as laser streaking, where photoelectrons released during ionization of a gas target see their final energy modified by a simultaneously present short infrared or terahertz pulse.
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Mar 29
Thursday

Shanghai Synchrotron Radiation Facility (SSRF) User Operation Status and Its Phase-II Project

Speaker: Dr. Tiqiao Xiao
XSD Presentation
401/A1100 @ 10:00 AM
Mar 26
Monday

Development and Characterization of Diffractive X-ray Optics

Speaker: Joan Vila-Comamala, XSD/IMG
XSD Presentation
401/A1100 @ 2:00 PM
View Description
We present the developments on diffractive X-ray optics achieved during the last year at the APS and CNM. Among other results, we demonstrate hard X-ray full-field transmission microscopy with sub-25 nm spatial resolution and tomographic capabilities. We discuss future developments and improvements.
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Mar 23
Friday

X-ray Brightness and Interfacial Studies: Development of a Field

Speaker: Sean Brennan, Fairview Associates
XSD Presentation
402/E1100 @ 11:00 AM
View Description
Abstract:

The field of X-ray surface scattering has blossomed over the past thirty years in large part because of the incredible advances in source brightness provided by facilities such as the Advanced Photon Source. Similarly, x-ray microscopy has been driven by improvements in x-ray sources and optics. In this talk, I will use examples from my own research to highlight improvements in both these areas. Finally, I will discuss the new possibilities for interface studies enabled by the beam line and capabilities that will be built at the upgraded APS. The upgraded APS will enable researchers the opportunity to study surfaces and interfaces in both real and reciprocal spaces, and will bring new insights to this important area of science.
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Mar 15
Thursday

The High Speed Imaging Program at 32-ID

Speaker: Kamel Fezzaa
XSD Presentation
402/E1100 @ 1:30 PM
Mar 15
Thursday

Investigating Energy Storage and Conversion Materials using Hard X-ray Tools

Speaker: Karena Chapman
XSD Presentation
402/E1100 @ 1:00 PM
Mar 15
Thursday

APS Strategy for Optics Development: Alternatives

Speaker: Lahsen Assoufid
XSD Presentation
402/E1100 @ 12:30 PM
Mar 15
Thursday

APS Strategy for Detector Development: Alternatives

Speaker: Chris Jacobsen
XSD Presentation
402/E1100 @ 12:00 PM
Mar 14
Wednesday

The Surface Diffraction Beamline at the ESRF and Recent Advancements in the Comprehension of Heterogeneous Catalysis

Speaker: Roberto Felici, European Synchrotron Radiation Facility
XSD Presentation
401/A1100 @ 11:00 AM
View Description
The aim of this talk is to describe the recently rebuilt surface diffraction beamline of the European Synchrotron Radiation Facility in Grenoble, France, and to provide some examples of the activities carried out. Particular attention will be dedicated to the most recent studies of operando heterogeneous catalysis. A new flow reactor [1], which we have conceived, gives the possibility of performing in-situ studies of the structure and morphology of the catalyzer surface at atmospheric pressure and at high temperatures. Results concerning the CO oxidation on Pd will be shown in details [2,3] together with examples of other reactions.

[1] R. van Rijn, et al., Rev. Sci. Instrum. 81 (2010) 014101
[2] R. van Rijn, et al. Physical Chemistry - Chemical Physics 13 (2011) 13167
[3] B.L.M. Hendriksen, et al., Nature Chemistry 2 (2010) 730
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Mar 9
Friday

Optical Design: From IR to X-Rays

Speaker: Ruben Reininger, Brookhaven National Laboratory
XSD Presentation
401/E1100 @ 11:00 AM
View Description
We will describe the optical design of four beamlines: IRENI, CSX, ISR and FXI. IRENI is an infrared beamline collecting 300 mrad of a bending magnet at SRC and dedicated to FTIR micro-spectroscopy. CSX is the only soft x-ray beamline in the NSLS-II project. It consists of two independent branches covering the energy range 170-2000 eV, one for experiments requiring high coherent flux and the other for fast polarization experiments. The source for CSX are two undulators working either phased or canted. ISR and FXI are two of the second phase beamlines for NSLS-II. The former is based on an undulator and is designed for In-Situ and Resonant Hard X-ray Studies in the energy range 2.1-2.3 keV. The source for FXI is one of the NSLS-II damping wigglers. FXI will be dedicated to Full field X-ray Imaging using an existing x-ray microscope at NSLS.
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Mar 6
Tuesday

Investigating Extreme States of Matter by X-ray Absorption Spectroscopy

Speaker: Sakura Pascarelli, European Synchrotron Radiation Facility, Grenoble, France
XSD Presentation
401/A1100 @ 11:00 AM
View Description
The European Synchrotron Radiation Facility is presently undergoing an important upgrade program. Within this upgrade, eight new beamlines will be constructed and will become operational between 2012 and 2016. One of the first upgrade beamlines (UPBL) is UPBL11, designed to provide state-of-the-art conditions to perform time resolved and extreme conditions x-ray absorption spectroscopy.

UPBL11 hosts two energy dispersive x-ray absorption spectrometers coupled to two experimental stations, and will become fully operational in 2012. This instrument will provide the user community new opportunities for investigating matter at extreme conditions of pressure, temperature and magnetic field. Target experiments for the future include kinetic studies of chemical reactions at high pressure and temperature, and investigation of extreme states of matter that can be maintained only over very short periods of time.

In this presentation, I will make an overview of recent results obtained on the former energy dispersive XAS beamline ID24 in the area of extreme conditions. Examples cover studies of chemical reactions that occur in the interior of planets, the investigation of pressure induced collapse of ferromagnetism in 3d metals, and first attempts to probe the electronic and local structure in melts at high pressures. Future perspectives for the investigation of laser-shocked matter are also discussed.
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Feb 28
Tuesday

Phase Contrast Microtomography using Polychromatic Synchrotron Radiation and Single-distance Phase-retrieval Techniques

Speaker: Alexander Rack, X-ray Imaging Group, European Synchrotron Radiation Facility, Grenoble, France
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Inline X-ray phase contrast is an attractive contrast mode for X-ray imaging techniques due to its increased sensitivity: by leaving an appropriate drift space between the sample and the imaging detector, interfaces within the probed specimen can be visualized. While this information is often useful for visual inspection, any further quantitative is not easily possible: the gray levels within the different materials regions are not necessarily different; they are just varying at the interfaces. But if the transmission radiographs are sent through a phase-retrieval process, the tomograms will exhibit ‘area contrast’ rather than edge-enhancing contrast.

In this presentation, the implementation and application the single-distance phase retrieval approach will be introduced [1, 2]. Advantages of this method are that it can be applied to any inline phase contrast tomographic data set; it allows phase-sensitive imaging without modification of existing experimental installations; it is extremely robust and user friendly; it can handle data from arbitrarily absorbing (multi-constituent) samples as well as tolerates polychromatic illumination. The latter is of crucial importance to progress towards higher data acquisition rates: when operating without monochromators, i.e. so-called pink beam or white beam configurations, the required exposure times can be reduced drastically. Microtomography in combination with pink-beam illumination and Paganin phase-retrieval has become the most demanded configuration at the ESRF beamline ID19: it covers now 30% of the ID19 data processing and about 80% for palaeontological studies.

[1] D. Paganin, et al., "Simultaneous phase and amplitude extraction from a single defocused image of a homogeneous object," J.Microsc. 206 (1), 33 (2002).
[2] T. Weitkamp, A. Rack, et al., "ANKAphase: software for single-distance phase-retrieval from inline X-ray phase contrast radiographs," J. Synchrotron Radiat. 18 (4), 617 (2011).
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Feb 13
Monday

The Scientist' Guide to Optimization

Speaker: Sven Leyffer, Mathematics & Computer Science Division, Argonne National Laboratory
XSD Presentation
401/A1100 @ 1:30 PM
View Description
The Scientist' s Guide to Optimization has a few things to say on the subject of optimization. Optimization, it says, is about the most massively useful tool a scientist can have. Many design, data analysis, and operational problems can be formulated as optimization problems. We present a survey of current research trends in optimization motivated by applications of relevance to the APS. We will touch on applications such as accelerator design, image analysis, and optimal control. In all cases we will highlight the relevant software projects within Argonne' s Mathematics and Computer Science Division.
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Feb 3
Friday

Investigating Heterogeneous Catalysts Synthesis, Reactivity and Deactivation with Combining X-ray and Other Techniques

Speaker: Dr. Haiyan Zhao, X-ray Science Division, Argonne National Laboratory
XSD Presentation
401/A1100 @ 10:00 AM
View Description
Various scales of spatial and temporal dimensions are involved in catalyst synthesis, reactivity and deactivation. Full understanding the catalytic processes and ultimately controlling the catalytic reactions require probes of broad time and length scales. We have combined multiple X-ray techniques and other spectroscopic techniques to study catalyst synthesis, reactivity and deactivation. Two examples will be presented to demonstrate the power of X-ray and combination of scattering and spectroscopy techniques.

First example is using the time resolved pair distribution function (PDF) methods to probe the kinetics, mechanism, and energetics for Ag nanoparticle synthesis in a porous zeolite. Understanding the formation of nanoparticles and how they are influenced by a support, is critically important for optimizing their activity. The PDF method can provide the nanoscale structure detail and fast time resolution which allows a multi-step mechanism delineated, and rate constants and activation energies to be estimated for reduction and surface diffusion steps. Complimentary diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and in situ X-ray absorption near edge spectroscopy (XANES) were used to illustrate the surface functional group and oxidation state changes in the particle formation and growth process.

Second example is about probing the active sites in Ni2P and NiFeP for catalytic hydrodesulfurization (HDS) reaction of a model compound 4,6-dimethyldibenzothiophene (4,6-DMDBT). HDS of 4, 6-DMDBT is dominated by two pathways, hydrogenation (HYD) and direct desulfurization (DDS). EXAFS analysis reveals that HYD is due to the square pyramidal Ni(2) and DDS is due to the tetrahedral sites Ni(1) for Ni2P. Combination of EXAFS and IR suggests the substitution of Fe atom in the active phase and a ligand effect on Ni sites.
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Jan 27
Friday

High Repetition Rate Methods for Efficient Laser/X-ray Pump-Probe Measurements of Molecular Dynamics

Speaker: Anne Marie March, Argonne National Laboratory
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Ultrafast, time-resolved, laser-pump, x-ray-probe experiments are powerful tools for understanding and controlling the behavior of matter at the molecular level. Transient structural changes, both geometric and electronic, of single molecules after excitation by a laser pulse can be probed with high resolution and within complex or disordered environments, such as gases and liquids, taking advantage of the superior spatial resolution, elemental specificity and penetration power of x-rays.

Third generation synchrotron sources, particularly the APS, provide x-rays with a unique combination of properties that are well suited for precision time-resolved measurements which include a high flux (1013 photons/second/0.01% bandwidth) that is distributed in short pulses (~100 ps) with moderate intensity (~106 photons/pulse) at a high repetition rate (MHz). Over the last decade laser-pump, x-ray-probe studies have been carried out at synchrotrons but a major challenge has been the low repetition rate (kHz) of standard amplified lasers resulting in underutilization of the synchrotron’s high flux. In response to this we have implemented a high repetition rate (54 kHz – 6.52 MHz), high power (10 W), laser system at 7ID-D at the APS.

In this talk I will highlight our initial experiments using this laser and the x-ray microprobe at 7ID-D. These include x-ray absorption spectroscopy (XAS) of the metalloporphyrin molecule Ni(II)-tetramesitylporphyrin (NiTMP) in solution at 135 times the rate of previous experiments, combined XAS, x-ray emission spectroscopy (XES), and liquid scattering measurements on the spin-crossover molecule Iron(II)-tris(2,2’)-bipyridine ([Fe(bpy)3]2+) in solution using the full flux available at the APS, and XAS of the photodetachment and recombination of the haloalkane CH2BrI in solution. Our results demonstrate how the use of high repetition rate, short pulse lasers as pump sources can dramatically enhance the duty cycle and efficiency in data acquisition and hence capabilities at synchrotron sources. These techniques will play an important role in the utilization of the SPX, the ~1 ps x-ray pulse source planned in the APS upgrade.
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Jan 20
Friday

Precipitation and Fracture of Notch Tip Hydrides in Zirconium Alloys

Speaker: Matthew Kerr, Office of Nuclear Regulatory Research (RES), US Nuclear Regulatory Commission,
XSD Presentation
401/B4100 @ 10:00 AM
View Description
Abstract Zirconium alloys are of importance to the nuclear industry, with primary application as a structural material for the in-reactor environment. The formation of brittle hydrides within zirconium alloys results in a degradation of the mechanical properties of the component in which they form. Therefore, the characteristics of hydride formation and the subsequent impact of these hydrides are critical factors in the determination of zirconium component service life. This talk summarizes a series of three experimental efforts characterizing the mechanical behavior of hydrides in zirconium alloys with high energy synchrotron X-ray diffraction. Part I focuses on the mechanical response of zirconium hydride within a bulk Zircaloy-2 matrix. Part II studies the near crack tip behavior of unhydrided Zircaloy-2. Part III characterizes the behavior of notch tip hydrides. The aim of this work is to quantify the influence of hydrides on the local notch tip strain field and characterize the internal strains in the hydrides themselves.

* Work conducted while Matthew Kerr was a graduate student at Queen’s University and does not reflect a position of the US NRC.
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Jan 16
Monday

Combined High-Energy Diffraction Microscopy (HEDM) and High-Energy X-Ray Tomography at the APS 1-ID Beamline

Speaker: Peter Kenesei, X-Ray Science Division, Argonne National Laboratory
XSD Presentation
401/A1100 @ 11:00 AM
View Description
The High Energy Diffraction Microscopy (HEDM) program attracts a growing community to the Advanced Photon Source 1-ID beamline. High-energy x-ray diffraction (above 50 keV) has been demonstrated to be a powerful tool for the structural characterization of polycrystalline bulk materials measuring the crystallographic orientation and stress states on the grain and sub-grain scales. High energy tomography provides fast three-dimensional maps using absorption or phase contrast, with spatial resolution at the micrometer scale. Both of these techniques have garnered increased interest towards engineering and industrial applications due to their combination of bulk penetration and high sensitivity.In the presentation I will introduce my HEDM evaluation program DIGIgrain that has been adopted for several user measurements at 1-ID and has proven to provide unique quality, compared to other existing programs, for peak segmentation and data reduction. Case studies of far-field diffraction measurements on metallic and non-metallic materials which have utilized DIGIgrain will also be presented.

The combination of these two complementary contrast mechanisms is highly beneficial for the characterization of inhomogeneities such as cracks or voids. Several case studies will be presented to demonstrate their capability to reveal structural details that cannot be detected by a single technique alone. This is especially true for the near field diffraction technique, which can advance directly by combining tomographic reconstruction and crystallographic orientation mapping from the same data set. This approach enables in situ investigations and avoids the registration problem of independent data sets.
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Jan 12
Thursday

In Situ and Operando Spectroscopies for the Characterization of Catalytic Materials

Speaker: Dr. Camille La Fontaine, Laboratoire de Réactivité de Surface, CNRS-Université Pierre et Marie Curie, Paris
XSD Presentation
401/A1100 @ 10:00 AM
View Description
Although heterogeneous catalysts are widely used among industrial processes, the detailed understanding of catalytic mechanisms still needs deeper investigations. The nature of the active sites, their geometry and local environment are determining parameters for the catalytic performances. A fine characterization is thus required to understand this structure-activity relationship and generally involves spectroscopic techniques, particularly through in situ and operando approaches. To this end, relevant developments regarding the use of time-resolved spectroscopies have been recently achieved. In this context, the formation of active phases and their further evolution under real catalytic conditions will be discussed on the basis of recent studies performed at the French Synchrotron SOLEIL using X-ray absorption spectroscopy and complementary techniques such as Raman spectroscopy. Examples will be detailed to illustrate the characterization of various materials, including supported oxides or metals, which are of wide interest in the area of energy, e.g. for biomass valorization or fuels synthesis.
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Jan 9
Monday

Electronics and Structural Dynamics Studies of Solar Energy Materials using Time-resolved X-ray Spectroscopy

Speaker: Xiaoyi Zhang, XSD/SRS
XSD Presentation
401/A1100 @ 1:30 PM
View Description
Ruthenium and Osmium polypyridyl complexes and their derivatives have attracted increasing interest and have been used as photosensitizers in solar-cells, molecular electronics and light emitting devices. Photoexcitation of those photosensitizers leads to long lived metal-to-ligand charge transfer (MLCT) states. If bonded to proper semiconductor nanocrystals, the photoexcited Ru and Os complexes inject electrons to semiconductors, resulting in interfacial-charge transfer state. We have applied time-resolved X-ray spectroscopy to study the electronic and molecular structures of photosentizers in both MLCT excited state and charge-separated state. A series of Ruthenium and Osmium polypyridyl complexes have been studies. Experimental results were compared with simulations/theoretical calculations, quantitative information on the molecular structure, electronic configuration and molecular orbital energies of ground and excited states have been revealed. The chances in the Ru-ligand distances have been directly characterized and rationalized by the interplay between two important factors governing the metal to ligand bonding, steric hindrance and π-backbonding. These works have demonstrated the great potential of time-resolved X-ray spectroscopy to study fundamental structural-functional correlations in solar electricity and fuel generation for both homogenous systems and heterogeneous interfacial systems.
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Jan 6
Friday

Optics Fabrication Activities at NSLS-II

Speaker: Ray Conley, NSLS-II, Brookhaven National Laboratory
XSD Presentation
401/A1100 @ 2:00 PM
View Description
Diverse optics fabrication activities are currently underway within the Optics Fabrication Group at NSLS-II, including work on crystal optics, multilayer Laue lens (MLL) growth and sectioning, and reflective multilayer optics. Crystal optics production capabilities currently include orientation, slicing, dicing, lapping, etching, and CMP polishing of silicon for high-resolution IXS, channel-cut monochromators, and other applications. The current status of MLL fabrication will be presented, including partial-nitrogen reactive sputtering for stress and interfacial roughness reduction which has recently led to a 70 micron thick single-growth MLL. Significant effort has been focused on the achievement of highly-stable nitrogen gas mixing for multilayer growth and the problems faced along with implemented solutions will be discussed in detail. Recent MLL sectioning results obtained by manual polishing, reactive ion etching, and focused ion-beam milling are promising. Multilayers composed of WSi2/Si, Vxsix/Si, Cr/Sc, V/B4C, and W/B4C benefit when grown with a small percentage of nitrogen. Reflective multilayer optics for a wide variety of applications, from ~200eV high energy-density experiments, to 80KeV synchrotron experiments will be presented. Two ion-beam sources (one RF and one DC) incorporating multiple gas mixing are being installed in the MLL deposition system over the next couple months which will expand our capabilities.
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2011

Nov 17
Thursday

Research in Hard X-ray Zone Plate Fabrication using Anodized Aluminum, and Zone Doubling

Speaker: Joan Vila Comamala and Steve Wang, Argonne National Lab
XSD Presentation
401/B4100 @ 11:45 AM
Nov 17
Thursday

X-ray Zone Plate Fabrication at the Center for X-ray Optics

Speaker: Patrick Naulleau and Erik Anderson, Lawrence Berkeley National Lab
XSD Presentation
401/B4100 @ 11:00 AM
Nov 16
Wednesday

Microsecond Time-Resolved SAXS at the BioCAT Beamline 18ID

Speaker: Dr. Raul Barrea, BioCAT / Illinois Institute of Technology
XSD Presentation
401/A1100 @ 9:30 AM
View Description
Small-angle x-ray scattering (SAXS) is a powerful method for obtaining quantitative structural information on the size and shape of proteins, and it is increasingly used in kinetic studies of folding and association reactions. The quality of data available at 3rd generation synchrotrons has allowed unprecedented signal-to-noise ratios which have, in turn, motivated efforts at ab initio modeling of low resolution macromolecular structures. The high brilliance x-ray sources and new detectors have also made possible microsecond time-resolved SAXS experiments reported here. At the Biophysics Collaborative Access Team Beamline (BioCAT) 18ID at the Advanced Photon Source, Argonne National Laboratory we have developed a high duty cycle scanning, microsecond time-resolution SAXS capability built around our KB mirror based microbeam system. This paper reports on the commissioning of the new microbeam small angle scattering instrument, the optic components, the mixing devices and visualization system, as well as the control software. The high duty cycle system allows a significant reduction in sample consumption and simultaneous SAXS/WAXS detection, yielding increases in resolution for structural modeling. Some pertinent results of time-resolved SAXS on biological samples are presented here.
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Nov 14
Monday

Reversal of Magnetic Interactions by Electric Field

Speaker: Philip Ryan, XSD Magnetic Materials Group
XSD Presentation
401/A1100 @ 1:30 PM
View Description
Direct magneto-electric coupling describes the interaction between magnetic and electric polarization through an intrinsic microscopic phenomenon in a single phase material. Systems which exhibit such coupling are potential candidates for use in a multistate logic memory storage device whereupon magnetic control with electric fields or ferroelectric control with magnetic fields could be used to alter memory bits. I present x-ray resonant magnetic scattering results providing direct evidence of a magneto-electric cross field effect mediated through strong spin-lattice coupling in a single phase rare earth titinate film. Compressively strained EuTiO3 is, as in bulk, an antiferromagnetic-paraelectric material, however through strain the balance of the magnetic interactions, both antiferromagnetic and ferromagnetic, shifts whereby the two approach energetic degeneracy. By applying an electric field in-situ one can tip the delicate equilibrium and suppress the long range antiferromagnetic order. This is accompanied by the emergence of short range ferromagnetic order. In addition we have qualitatively replicated the microscopic shift from antiferromagnetic to ferromagnetic order with electric field using first principle density functional calculations.
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Nov 8
Tuesday

Deformation in Cu, from Large Deformations to Dislocations

Speaker: Dr. Jonathan Tischler, Oak Ridge National Laboratory
XSD Presentation
401/A5000 @ 11:00 AM
View Description
The development of 3D x-ray microscopy using micro-beams at sector 34ID-E, has enabled us to analyze the deformation process in crystalline materials on multiple length scales. It has provided especially useful information on the mesoscale. The mesoscale is that awkward intermediate region that is too big for atomic modeling, and yet still too small for continuum models; however it is often the length scale that makes real materials real. I will describe the deformation in Cu at length scales from a few 10’s of microns to ~300nm, highlighting examples of: continuum deformation, patterning (with strain), and dislocation formation with a comparison to discrete dislocation dynamics simulations.

Research supported by DOE-BES Materials Science & Engineering Division.
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Nov 2
Wednesday

X-ray Studies of Soft Materials

Speaker: Dr. Jyotsana Lal, Materials Science Division, Argonne National Laboratory
XSD Seminar
401/A1100 @ 11:00 AM
View Description
Due to the presence of thermally excited capillary waves, the free surfaces of fluids, complex fluids, and other generically soft materials are fluctuating structures. Examining the surface dynamics of such soft materials provides a window into their rheology. In this talk I will present results for more complex polymer bilayer films. X-ray photon correlation spectroscopy was employed in a surface standing wave geometry in order to resolve the thermally driven in-plane equilibrium dynamics at both the surface/vacuum (top) and polymer/polymer (bottom) interfaces of a thin polystyrene (PS) film on top of poly(4-bromo styrene) (PBrS) and supported on a Si substrate. The top interface shows two relaxation modes, a fast and a slow one, while the buried polymer-polymer interface shows a single slow mode. The slow mode of the top interface is similar in magnitude and wave vector dependence to the single mode of the buried interface. The dynamics are consistent with a low-viscosity mixed layer between the PS and PBrS and coupling of the capillary wave fluctuations between this layer and the top PS layer. The non-equilibrium behavior of the top surface of a bilayer was also investigated. The two-time correlation function provides the in-plane dewetting velocity of large single holes as a function of time. The dewetting velocity decreases continuously with time according to a power law with exponent ½. This reduction of the dewetting velocity with time is related mainly to interface friction of the viscoelastic film. Decreasing the thickness of the top film and increasing the viscosity of the bottom surface leads to spinodal-like dewetting. The capillary instability of thin film breakup by thermal fluctuations is analogous to spinodal decomposition in fluid mixtures, where height fluctuations correspond to composition fluctuations in the fluid mixture. Further, I will outline our adaptation of coherent diffraction imaging for visualizing cellulose crystals in situ. This method is capable of producing images of individual crystalline domains even when the cellulose is embedded within opaque plant material. The 3D images suggest that the large‐scale organization of the crystalline fibrils depends on the position in the plant (primary vs secondary plant cell walls), the hydration of the material and the maturity of the plant.
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Oct 31
Monday

X-ray Absorption Spectroscopy Study of Prototype Chemical Systems

Speaker: Craig P. Schwartz, University of California
XSD Presentation
432/C010 @ 11:00 AM
Oct 10
Monday

Development of Grating-Based Talbot Interferometry at APS for Quantitative High-Energy X-ray Imaging & for Optics & Beam Wavefront Characterization

Speaker: Lahsen Assoufid, XSD/OPT
XSD Presentation
401/A1100 @ 1:30 PM
View Description
X-ray grating-based Talbot interferometry has seen a very rapid development since its first application for synchrotron radiation about a decade ago. It is relatively easy to implement and can be used for a wide range of applications including imaging and tomography, as well as for optics and beam wavefront characterization. In particular, the technique yields high-sensitivity differential phase-contrast and dark-field images as well as absorption contrast data, all in one single set of measurements, and can work even with low brilliance sources. In this presentation, I will review the basic principle of grating interferometry. I will discuss ongoing efforts and progress to develop this technique, and implement it at the Advanced Photon Source as a metrology tool for optics development and beam wavefront characterization, and as a standard tool for quantitative static and fast tomography in biological and other systems. *Work supported by U.S. Department of Energy Office of Science under the strategic LDRD project number 2011-170-R1.
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Sep 22
Thursday

X-Ray Studies of Biomatter in Microfluidic Sample Environments

Speaker: Professor Sarah Koester, Georg-August-Universitat Goettingen, Institute for X-Ray Physics/CRC Nano-Spectroscopy and X-Ray Imaging
XSD Presentation
431/C010 @ 11:00 AM
View Description
Biological systems such as for example cells and cellular components are governed by processes, which take place on the nanometer to micrometer length scales. X-ray scattering and diffraction techniques are extremely well suited to study these processes as the spatial resolution extends well into the relevant length scales. At the same time, the investigation of such systems, in particular in the field of the biophysical research requires well-defined and controllable sample environments. One way to establish such environments is by employing microfluidic devices tailored for the particular experiment. I will present experiments which take advantage of different flow regimes, ranging from the assembly pathways and kinetics of biopolymers, to network formation and structural analysis of whole cells.
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Sep 21
Wednesday

Spin-Orbit Interaction Rediscovered in Heavy Transition Metal Oxides

Speaker: Gang Cao, University of Kentucky
XSD Presentation
431/C010 @ 11:00 AM
Sep 19
Monday

Hard and Soft X-ray Tomography at the Advanced Light Source

Speaker: Dula Parkinson, Advanced Light Source, Lawrence Berkeley National Laboratory
XSD Presentation
431/C010 @ 11:00 AM
View Description
Soft x-ray tomography allows quantitative, high resolution imaging of cellular organization and sub-cellular morphology. Whole cells can be imaged intact, unstained and fully hydrated. The National Center for X-ray Tomography (NCXT) is based at the full field soft x-ray microscope XM-2 at Beamline 2.1.2 of the Advanced Light Source. This talk will describe recent results, including methods used for robust, fully automatic, high throughput image analysis. The hard x-ray microtomography facility at the Advanced Light Source, Beamline 8.3.2, is used for a wide range of samples, including rock, bone, ceramic, metal, and soft tissue. Dr. Parkinson will present results from some of these applications to demonstrate some of the common image processing challenges faced by users of our facility and describe the progress in providing users with a data processing pipeline.
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Sep 16
Friday

From its Spatial Profile to its Strong Coupling with Molecules

Speaker: Antonio Picón Álvarez, University of Colorado
XSD Presentation
401/B4100 @ 1:00 PM
View Description
The current laser technology allows us to play with a wide range of wavelengths, intensities, time lengths, spatial profiles, etc. In particular, by exploiting the spatial profile of light we can find promising applications to quantum information. In almost all cases, so far, photons were assumed to carry one unit of angular momentum, related to the polarization of the photon (spin angular momentum, SAM). However it is now clear that photons can possess extra angular momentum (orbital angular momentum, OAM) related to their spatial profile. On the other hand, long wavelengths (infrared) and high intensities (1013-1014 W/cm2) open a new regime of strong couplings in molecules, allowing novel molecular coherent control schemes and two-level high-harmonic generation.
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Sep 8
Thursday

Application of Three-dimensional Imaging in Clinical Orthodontics: A 3D Cephalometric Endeavor

Speaker: Budi Kusnoto, UIC
XSD Presentation
438/C010 @ 10:00 AM
View Description
Various 3D imaging technology has been utilized in the clinical application in orthodontics. Surface scanning, CBCT images and stereophotogrammetry are among the commonly listed technology. Despite the rapid development and clinical use of 3D CBCT to map hard tissue and soft tissue of human craniofacial complex, there are lack of 3D normative data available to establish control as part of cephalometric analysis in clinical orthodontics. Unfortunately, to date only stereophotogrammetry can be used in order to reconstruct 3D cephalometric wireframe from 2D available cephalometric data of control groups taken previously. 3DCeph™ computer software was written for analysis of radiographics landmark data under the Windows operating system. Several computer algorithms and combinations of projections were integrated into the system to give the most accurate three-dimensional model. The accuracy of the system was tested by comparison to direct and 3D CT-scan measurements. Tests using a dry human skull found average errors of 1.5 mm for linear and 2.5o for angular measurements. Subsequent tests using a living subject found accuracy similar to the skull test. Efficacy of different algorithms and combinations of projections was assessed. Two-way ANOVA found that the vector intercept algorithm using the lateral-frontal combination of projections produced the most accurate measurements. In this system, the influence of landmark identification error was greater than the influence of head positioning error. However, landmark identification error can be minimized by using a computer-driven vector intercept algorithm, whereas the special facebow can reduce head positioning error to a minimum. The computer-generated model enables the clinician to simulate orthodontic treatment three-dimensionally and is especially useful for cases involving surgical planning or growth.
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Aug 30
Tuesday

Ferroelectric Domains in Thin Films - Formation, Imaging and Dynamics

Speaker: Professor Sushanta Dattagupta, Indian Institute of Science Education & Research
XSD Presentation
431/C010 @ 2:00 PM
View Description
We use simple Landau-Ginzburg free energy to describe the formation of ferroelectric domains in thin films. A further extension in the form of time-dependent Ginzburg-Landau equations enables us to analyze nucleation and dynamics of domain patterns. Central to our computational scheme is an application of finite element methods. A useful technique to study domain dynamics involves Atomic Force Microscopy (AFM), which becomes handy as many ferroelectric systems are piezoelectric as well. We incorporate the consequent piezo coupling between strain and polarization order parameter in all our calculations. The results are expected to have important applications to memory devices.
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Aug 25
Thursday

Calculating Coherence

Speaker: Markus Osterhoff, European Synchrotron Radiation Facility
XSD Presentation
401/B4100 @ 10:00 AM
View Description
Wave-optical simulations of x-ray focusing devices allow for optimized design of experiments and improved analysis of recorded data. Accompanied by analytical estimates to reduce parameter space, they provide key information to predict photon fields even for complicated geometries including real structure.

Most wave-optical simulations carried out so far in the x-ray regime assumed idealized point-sources. Using a Monte Carlo approach to model stationary stochastic fields, we show how to simulate coherence filtering by x-ray optical elements commonly used at synchrotron beamlines. Within this scheme, established codes to propagate point-sources can be re-used and generalized towards partially coherent sources. Experimental data are interpreted using this scheme.
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Aug 16
Tuesday

Elements at High Pressures - Structure, Metal to Semiconductor Transition and Superconductivity

Speaker: Takahiro Matsuoka, Osaka University
XSD Presentation
431/C010 @ 2:00 PM
View Description
Pressure drastically and categorically alters phonon, electronic, magnetic, structural, and chemical properties by changing inter-atomic distances. High-pressure has been playing an important role in studies on superconductors, expanding the number of known superconductors and pushing up their superconducting transition temperatures Tc to record values. In this presentation I provide a review of recent high-pressure studies of electronic transformations, including superconductivity, in the elements. Specifically, I discuss advances in the simultaneous measurement technique of electrical resistivity and X-ray diffraction which allow the observation of superconductivity and changes in crystal structure of Li, Ca, and I2.
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Aug 11
Thursday

Structure-Property Correlations in Biological & Biomimetic Materials

Speaker: Professor Ulrike Wegst, Dept. of Materials Science & Engineering, Drexel University
XSD Presentation
438/C010 @ 11:00 AM
Aug 9
Tuesday

High Aspect Ratio X-ray Optical Components Fabricated by X-ray Lithography

Speaker: Juergen Mohr, Karlsruhe Institute of Technology
XSD Presentation
438/C010 @ 10:00 AM
View Description
At the Karlsruhe Institute of Technology deep X-ray lithography, the first step of the LIGA process is used to fabricate high aspect ratio micro structures out of polymer. By a subsequent electroforming process metallic micro structures are realized. The structures are characterized by dimensions in the micrometer range, aspect ratios of up to 100, steep and smooth sidewalls with roughness (Ra) in the range of 10 nm. These features give rise to use the LIGA process for fabricating X-ray optical structures like compound refractive lenses (CRLs) or gratings for Talbot interferometry Using epoxy based resist material CRLs with parabolic shaped elements have been fabricated for different energies up to 50 keV, focal lengths down to a few millimetre and focal spot sizes of less than 100 nm These parabolic lenses are efficient up to apertures of a few hundred micrometers. To increase the aperture the absorbing material was further decreased by transforming the continuous parabolic into a truncated parabolic lens design with a size of the refractive element of approx. 10 µm. By stabilizing more than ten thousands of these structures with a height of several millimetres by a lattice fence like arrangement lenses with an aperture of 1.5 mm x 1.5 mm could be achieved leading to spot sizes in the micron range. Building a Talbot-interferometer system for X-ray phase imaging at higher energies requires the fabrication of gratings with a period in the micron range out of gold with a height of at least 100 μm. In this case the lithographically fabricated SU8 structure is used as a template for the electroforming process. Optimizing the resist material, the design and the process conditions lead to the fabrication of grating structures with an aspect ratio of more than 100 in a field of view of 50 mm2. With such gratings visibilities of 65% for 30 keV and 25% for 52 keV could be measured at ID19 at ESRF. In the talk we will describe the processes to fabricate CRLs and grating structures and show the results of the characterization experiments. In view of application focus will be on synchrotron experiments but also on experiments done with conventional X-ray sources.

Jürgen Mohr received his diploma in physics in 1983 and his Ph.D. in mechanical engineering in 1987 from the University of Karlsruhe with an emphasis in micro system technologies. He has been with Forschungszentrum, Karlsruhe since 1987 as a research associate working in the field of X-ray lithography for micro fabrication (LIGA process). Since 1992 he is leading the X-ray lithography and micro optics group at the Institute of Micro Structure Technology (IMT) of the Karlsruhe Institute of Technology (KIT). He is also deputy head of IMT. His interests are in the field of micro-fabrication by Deep X-ray lithography (LIGA process) and in micro optical components and systems for sensor and telecommunication applications as well as in X-ray optical components. He has published more than 100 papers on various topics in micro technology and applications. He is co-author of two text books on micro technology.
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Aug 5
Friday

Evaluation Software for Nuclear Resonant Scattering

Speaker: Dr. Wolfgang Sturhahn, Jet Propulsion Laboratory, California Institute of Technology
XSD Presentation
431/C010 @ 2:00 PM
View Description
The efficient operation of nuclear resonant scattering beam lines at third generation synchrotron sources is leading to large amounts of collected data and precipitates the urgent need for quick and reliable data analysis. For this purpose, two major software packages were developed, PHOENIX for inelastic spectra and CONUSS for time spectra. Each package has been developed and improved incrementally over the last decade and is designed to flexibly address the needs of different clientele. Scientists from various areas, such as geophysics and planetary sciences, biophysics and biochemistry, nano and material science, have applied the CONUSS and PHOENIX routines to their data and produced numerous publications with the results.

In this presentation, the focus lies with an overview of features of existing software and future development paths. With beam line operations being mature, optimization of software performance and interface has the potential to increase efficacy of data processing and to maximize scientific beam line output.
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Jul 29
Friday

Coupling X-ray Spectroscopy and Scanning Probe Microscopy for Simultaneous Sample Topography and Chemical Mapping

Speaker: Professor Didier Tonneau, Centre Interdisciplinaire de Nanosciences de Marseille, Universite de la Mediterranee, France
XSD Presentation
431/C010 @ 11:00 AM
View Description
Scanning Probe Microscopies (Scanning Tunnelling Microscopes (STM), Atomic Force Microscopes (AFM), Shear Force Microscopes (SFM)…) are powerful tools for surface topography analysis at high lateral resolution. However, these equipments cannot provide a priori chemical mapping of the analysed surface. X-Ray Spectroscopy is a fine surface analysis technique allowing to define chemical and structural properties of a material. The lateral resolution for chemical mapping is limited by the X-ray primary beam focusing optics in the range of 20-50 nm for soft X-rays (<4 keV) and 100-1000 nm for hard X-rays (>4 keV). However, in these experiments it is not possible to simultaneously acquire the sample topography and thus it is not possible to perform a spectroscopy on a given micro- or nano-object somewhere on the surface. We have designed and fabricated a Shear Force Microscope head allowing to obtain simultaneously with the same apparatus and in ambient conditions, the sample topography and chemical mapping by XRF or XAFS-XEOL [1, 2]. In the former case, a sharp optical fibre is used as shear force probe for sample topography and for simultaneous collection of the visible luminescence under focused X-ray excitation (resolution 50 to 100 nm for both topography and chemical analysis). In the latter configuration, an X-ray capillary replaces the optical fibre to collect the X-ray sample fluorescence (resolution of 100 nm expected).
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Jul 29
Friday

Ultra-fast Streak Camera Development and Its Application at the Advanced Light Source

Speaker: Jun Feng, Lawrence Berkeley Lab
XSD Presentation
432/C010 @ 10:00 AM
View Description
An x-ray streak camera has the unique feature that it allows the simultaneous recording of ultrafast temporal information as well as spectral information using a two dimensional charge-coupled device detector. The use of streak cameras is complementary to third-generation synchrotrons, as a means to obtain sub-ps temporal resolution. At the ALS, we have developed x-ray streak camera with both transmission geometry and grazing incidence geometry for ultrafast magnetic dynamics study and warm dense matter dynamics study. Our streak cameras can have high temporal resolution (233fs for 266nm light, transmission geometry) and high quantum efficiency (can measure signal shot using 100um cathode slit, reflection geometry). Also the streak camera has a feature of compact and can be installed to any x-ray beamline in principle.
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Jul 25
Monday

X-ray Detector Development at Teledyne-Dalsa and University of Waterloo

Speaker: Nixon O (Teledyne-Dalsa) and Karim Karim (University of Waterloo)
XSD Seminar
401/A1100 @ 10:30 AM
View Description
Teledyne-Dalsa and University of Waterloo are collaborating on a small pixel (25 micron pitch) direct-detection (selenium) x-ray detector with an energy range from 20-80keV. We will discuss various selenium detector architectures (e.g., unipolar charge sensing and selenium avalanche technologies). The specifications for a prototype detector using crystalline CMOS technology and selenium will be presented. We will also present Teledyne-Dalsa′s capabilities for custom x-ray detector fabrication. The seminar will be followed by an open discussion of detectors needs at the APS.

http://www.teledynedalsa.com/ls/
https://ece.uwaterloo.ca/~kkarim/

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Jul 15
Friday

High Repetition Rate Ultrafast Time-Resolved X-Ray Absorption Spectroscopy

Speaker: Christopher Milne, Swiss Light Source
XSD Presentation
432/C010 @ 11:00 AM
View Description
Using x-ray absorption spectroscopy (XAS) to probe laser-excited samples we can obtain excited-state structural and electronic dynamical information not available through other techniques. [1,2] One of the restrictions of most synchrotron-based implementations of this technique is the three-orders of magnitude mismatch between x-ray and laser repetition rates (MHz Vs. kHz). By using a laser capable of generating significant pulse energies at MHz repetition rates we can eliminate this discrepancy, thus greatly reducing measurement times and enhancing achievable signal-to-noise ratios. [3] Several examples that demonstrate the strength of this technique will be presented, including spin-state investigations of an iron (II) molecular system using transient XAS on pre-edge transitions, probing the metal-to-ligand-charge-transfer ground-state character of a Rhenium-halide molecular complex, resolving the ligand rebinding dynamics of the protein myoglobin under physiological conditions, and observing the solvent dependence of the photo-generated-solvated-electron recombination rate with iron(II) hexacyanide.

[1] C. Bressler and M. Chergui, "Molecular structural dynamics probed by ultrafast x-ray absorption spectroscopy", Ann. Rev. Phys. Chem. 61 (2010) 263-282.
[2] L.X. Chen, X. Zhang, J.V. Lockard, A.B. Stickrath, K. Attenkofer, G. Jennings, and D.-J. Liu, "Excited-state molecular structures captured by X-ray transient absorption spectroscopy: a decade and beyond", Acta. Cryst. A 66 (2010) 240-251.
[3] F. Lima, C.J. Milne et al. "A high-repetition rate scheme for synchrotron-based picosecond laser pump/x-ray probe experiments on chemical and biological systems in solution", Rev. Sci. Instr. (2011) available online.
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Jul 14
Thursday

Materials Synthesis and Characterization at CHESS

Speaker: Darren S. Dale, Cornell High Energy Synchrotron Source, Cornell University
XSD Presentation
432/C010 @ 10:00 AM
View Description
This presentation will cover two recent projects at CHESS. The first is in-situ x-ray scattering during Pulsed Laser Deposition (PLD) growth of complex oxide thin films. Time-resolved studies of the location, intensity and shape of surface diffuse scattering peaks during layer-by-layer growth provide information concerning the evolution of the distribution of islands, yielding the effective diffusivities associated with inter- and intra-layer transport. Repeating the measurements at various temperatures reveals Arrhenius behavior, which can then be extrapolated to obtain the maximum effective diffusivities D_0, which are orders of magnitude smaller than the vibrational attempt frequency [1]. These measurements constrain the influence of proposed smoothening mechanisms for PLD and demonstrate the key roles played by nucleation and coarsening. Our results significantly impact prior estimates of the thermal diffusivity involved in PLD of SrTiO3.

The second topic is high-throughput x-ray characterization of composition-spread thin films. We have been using a technique for the analysis of continuous composition-spread thin films using simultaneous acquisition of diffraction images and fluorescence spectra using a 60 keV x-ray source at the CHESS A2 beamline [1]. It is common to find highly textured regions in composition-spread films, and this diffraction technique is accordingly designed to provide detection of diffraction from each family of Bragg reflections, affording direct comparison of the measured profiles with powder patterns of known phases. These techniques are important for high-throughput combinatorial studies as they provide structure and composition maps which may be correlated with performance trends within an inorganic library. We have been developing software for subsequent data processing, which provides a graphical user interface and a suite of algorithms implementing background subtraction,peak identification using wavelet transforms, and produces maps of the diffraction profiles, thin film fiber texture, and composition.
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Jun 13
Monday

In Situ Measurement of Melting of Laser Irradiated Gold Nano Rods using Small-Angle X-ray Scattering

Speaker: Yuelin Li, XSD/TRR
XSD Presentation
401/A1100 @ 1:30 PM
View Description
Interaction between laser pulses and nano particles is rich of physics such as plasmonic resonance, melting of the crystal order and particle shape change, and the re-crystallization of the nano particles. These are of fundamental importance for applications of such nanoparticles in medical therapy, high density data storage, and catalysts for energy harvest. We present preliminary measurement of laser-nanorod interaction including the modification of the nano particle shape and modal distribution in a water suspension. We will show the effect of the particle anisotropy and the way to control the laser/nanorod interaction. A plan for future experiments is also outlined.
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Jun 2
Thursday

Long Trace Profilometer for Metrology of X-ray Optics

Speaker: Dr. Ajay K. Saxena, Indian Institute of Astrophysics
XSD Presentation
432/C010 @ 11:00 AM
View Description
The XUV Synchrotron Radiation Source (SRS) Indus-I and Indus-II at Raja Ramanna Centre for Advance Technology, Indore, India, require grazing incidence optics in the beam lines. A metrology facility in IIA was set up to facilitate the fabrication and evaluation of X-Ray optics from time to time at different stages of service. The present LTP (version II) has been built with very demanding specifications. In this presentation I am going to describe the novel concept used in this development of LTP and achievable performance.
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May 25
Wednesday

Design and Synthesis of Large-Area, Super-Repellent, Multifunctional Polymer Composite Coatings

Speaker: Professor Constantine Megaridis, University of Illinois at Chicago
XSD Presentation
438/C010 @ 11:00 AM
View Description
Scientific activity in multifunctional coatings and films; much of the relevant research in this area targets the interaction of such surfaces with fluids. We describe a mild, large-area, solution Recent advances in polymer science and nanomaterials have fueled a frenzy of -based coating method designed to impart desirable surface functionalities (such as super-repellency, i.e. contact angles above 150o) to different substrates ranging from glass and metals to nonwoven materials and filters. The wet-based approach relies on combining a polymer matrix in solvents with other materials to enhance adhesion and allow long lasting micro/nanoparticle filler dispersion. The advantage of the technique lies in its inherent ability to impart multiple functionalities by adding the proper ingredients to the solution, thus forming durable dispersions that are applied on the target surface by spray or other standard techniques. The approach combines tunable surface energy with micro-to-nano scale hierarchical roughness, a necessary condition for super-repellent behavior. In some coatings, super-repellency is combined with self-cleaning ability, as demonstrated by low droplet roll-off angles (i.e. low contact angle hysteresis). Several examples (including elastomeric, electrically conducting and icephobic coatings) are presented to demonstrate the advantages of this method for select technological applications.
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Apr 27
Wednesday

Diffractive X-ray Optics for X-ray Focusing and Imaging

Speaker: Joan Vila-Comamala, XSD-IMG
XSD Seminar
401/A1100 @ 11:00 AM
View Description
urrent synchrotron radiation based scientific programs are placing demand for high resolution X-ray probes towards ten nanometers. Over the years, diffractive X-ray optics has been proven as an effective tool for X-ray focusing and imaging. Here, we report on the manufacture and characterization of high quality X-ray optics for soft and hard X-rays. Several fabrication approaches are discussed in detail and broad examples of the characterization of the fabricated devices by means microscopy and coherent diffractive imaging are provided. Finally, future directions for further improvements of diffractive X-ray optics are explored with particular focus on optics for the high-energy range of APS.
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Apr 19
Tuesday

Oxides on Nanoscale Platinum Surfaces

Speaker: Daniel Hennessy, Materials Science Division, Argonne National Laboratory
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Present x-ray crystal truncation rods (CTR), resonant surface x-ray scattering (RSXS), and electrochemical data from nanofacets of Pt (100) and (111) and single-crystal surfaces. Data analysis shows that an epitaxial air-stable bilayer oxide forms on Pt (100) nanofacets when a high-index platinum surface reconstructs to the nanofacets at ~1340 K in an oxygen environment. The Pt atom positions are determined by CTR fits and their oxidation states in each oxide layer are determined by RSXS. Pt (111) nanofacets also support an oxide based on CTR fits, though the oxidation states are not clearly resolved due to weak signals. The well-ordered, ideally terminated oxide-free nanofacets are restored by electrochemical cycling in CO-saturated solution. Extended surfaces of Pt(111) and Pt(100) prepared similarly do not form bilayer oxides. Instead, they support only a single layer of adsorbed oxygen. The details of the bilayer models and the differences between the nanofacets and extended surfaces are discussed using theoretical predictions.
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Apr 19
Tuesday

Composites of Phodium-Substituted Polyoxometalates and Nanoparticles for Electrocatalytic Sensors

Speaker: Kamila Wiaderek, Miami University
XSD Presentation
433/C010 @ 10:00 AM
View Description
Polyoxometalates (POMs) such as phosphomolybdate, PMo12O403- (PMo12), and the tungsten analogue (PW12) catalyze electrochemical reductions and adsorb to electrode materials. Because they adsorb to gold and are weak bases, they are well-suited to act as surface layers that stabilize gold nanoparticles (AuNPs) as negatively charged moieties in aqueous solution over a wide pH range. In the present study, PMo12 and PW12 are reacted with dirhodium(II) acetate to form transition-metal substituted POMs such as (PO4)W11O35{Rh2(OAc)25-, Rh2PW11 [1,2]. These species retain the ability to catalyze reductions but also can mediate oxidations via the Rh(II,III) couple. A procedure for synthesizing aqueous-phase Rh2PW11 stabilized AuNPs was developed. Strong adsorption of POMs on electrodes suggested direct attachment of Rh2PW11-AuNP and Rh2PMo11-AuNP, but electrodes modified in this manner were not stable. Hence, GC was modified with a monolayer of protonated 3-aminopropyl trimethoxysilan! e (APTES). Electrostatic assembly of the Rh2PMo11-AuNP yielded a modified electrode that was stable in quiescent solution. Cyclic voltammetry of GC | APTES | Rh2PMo11-AuNP in 0.05 M H2SO4 at 50 mV•s-1 in quiescent solution showed the expected set of reversible peak-pairs for PMo11 in the range, -0.2 - 0.6 V vs Ag|AgCl and the reversible Rh(II,III) couple at 1.0 V. The reduction of bromate was catalyzed at 0.0 V. The sensitivity of the determination of bromate by cyclic voltammetry was greater with the AuNP-containing film than with GC | APTES | Rh2PMo11, probably because of the greater effective surface area. Extension to detection in flow-injection amperometry failed because the electrode was not stable. To prevent loss of the catalyst under flow conditions, we are modifying the GC by electrochemically assisted deposition of a nm-scale sol-gel film that contains templated nanopores [4,5]. After removal of the templating agent with an oxygen plasma and capping the silic a with a silane, layer-by layer assembly within the pores is used to immobilize Rh2PMo11-AuNP. This electrode has day-to-day stability and permits determination of bromate (by reduction) and cysteine (by oxidation) at the nM-level.
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Apr 18
Monday

Preparation and Characterization of Oxidic Heterostructures

Speaker: Daniel Schumacher , Jülich Research Center
XSD Presentation
431/C010 @ 3:00 PM
View Description
Two different thin film systems have been prepared and characterized:

1) La0.7Sr0.3MnO3/SrTiO3 (LSMO/STO) samples have been grown by Pulsed Laser Deposition and High Oxygen Pressure Sputtering. The systems exhibits an exchange bias effect even though no nominally antiferromagnetic material is present. Sample characteroztaion indicates that the size of the effect - i.e. the shift of the hysteresis curve - is linked to oxygen stoichiometry of the LSMO layer. Polarized neutron reflectometry and XMCD in reflection geometry have been performed to analyze the magnetic depth profile of the LSMo layers.

2) La0.5Sr0.5MnO3/BaTiO3 (LSMO/BTO) samples have been grown by Oxide Molecular Beam Epitaxy at CNM. Theoretical calculations predict a dependence of the magnetic depth profile of the LSMO layer on the direction of the electric polarization in the BTO layer, since the 50% doping level in the LSMO phase diagram is the border between antiferromagnetic and ferromagnetic order. Very recently, XMCD in reflection geometry measurements have been done to analyse the magnetic depth profile in the LSMO layer.
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Apr 14
Thursday

Compact Neutron and Photon Sources at Tsinghua University: Overview, Opportunities and Outlook

Speaker: Chun Loong and Xuewu Wang, Tsinghua University
XSD Presentation
433/C010 @ 2:00 PM
View Description
The neutron and x-ray facilities at Tsinghua University that are based on accelerator-driven 9Be(p, n)-reaction and Thomson-scattering radiation, respectively, differ from large central facilities in three aspects: 1) Located on the university campus, the sources are designed, constructed and operated by faculty and staff with strong student participation, ideally suitable for education and experimental training, 2) Configured compactly and flexibly, the n/x beamlines provide basic materials characterization capabilities that complement scientific research of in-house and external users, and 3) Working closely with the accelerator and neutron communities in China and abroad, the CPHS and TTX facilities* have the potential for instrumentation and technological development, expanding to lateral innovation such as neutron/proton therapy, accelerator-driven systems for waste treatment and energy amplification. TTX is currently under commissioning and CPHS is scheduled to finish the first-phase construction in 2012.

In this talk we present an overview of the n/x-source projects, allude to the need of young talents and the associated professional opportunities, and advocate the importance of international cooperation.
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Apr 14
Thursday

High Frequency Magnetization Dynamics of Ferromagnetic Nano-Structures

Speaker: Sean Zohar, Applied Science Innovations
XSD Presentation
431/C010 @ 1:30 PM
Apr 11
Monday

Structure and Magnetism in Complex Oxide Films

Speaker: Philip Ryan, XSD/MM
XSD Presentation
401/A1100 @ 1:30 PM
View Description
My goal is to provide a fundamental understanding of magnetic related device oriented phenomena. Ultimately we want to control or manipulate magnetic behavior which can lead to increased density and energy efficient information storage capabilities. Structure often plays a critical role in applicable macro phenomenon, including magnetic order and magnetic transition temperatures. In this talk I will present our recent findings on complex ordered oxide films, in particular antiferromagnetic LaMnO3 – SrMnO3 superlattice structures in addition to the multiferroic EuTiO3 system. Regarding the latter I will go into some depth to describe this extraordinary and exciting material. High quality strained EuTiO3 films are now providing us with opportunities to utilize scattering measurement techniques to understand the intricacies between structure and magnetic order.
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Apr 8
Friday

Binary Alloy Solidification at 35 Tesla

Speaker: Jason Cooley, Los Alamos National Laboratory
XSD Presentation
431/C010 @ 11:00 AM
View Description
Chandrasekar showed in 1957 that the viscosity of a metallic liquid increases quadratically perpendicular to an applied magnetic field. At tens of tesla, this increase in viscosity can be by orders of magnitude, resulting in very anisotropic diffusion constants. Also, the field can orient paramagnetic crystallites in the liquid. Our work is focused on identifying alloys in which an applied field has an effect on the solidification microstructure, determining its magnitude, and understanding why it occurs. Because the field is an external parameter independent of temperature, composition, and pressure, its ability to effect solidification microstructures has profound implications for the development of engineered microstructures. We report on the solidification microstructures of binary alloys at and near eutectic compositions in 0 and 35 Tesla fields. In Al-Ni and Mg-Sb alloys the microstructures are layered perpendicular to the applied field, while those in the Al-Cu and Ag-Ge systems are parallel.
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Mar 28
Monday

In Situ Experiments in X-ray Imaging -- Application to Materials Science

Speaker: Eric Maire, Mateis Lab, Institu National des Sciences Appliquees (INSA)
XSD Presentation
431/C010 @ 3:00 PM
View Description
X ray imaging is useful in materials science because it allows information to be retrieved non destructively from the interior of opaque samples. X ray radiography has then been used for many years and more recently, X ray computed micro tomography has emerged as a complementary and more powerful technique of visualization. Imaging is used in materials science because in order to optimize the properties of materials, a thorough understanding of the mechanisms responsible for these properties is crucial. Although post mortem observation can be a simple solution, it is more desirable to observe in situ the mechanisms at play. In this talk, we will recall some basic principles of X ray imaging and then we will focus on different examples where in situ experiments have been carried out in X ray radio or tomography. These examples include tensile and compression tests on ductile metals or foams, freezing of colloidal supensions or solidification of aluminium alloys.

Bio:
Eric Maire graduated as a materials science engineer and then obtained a PhD in the Mateis Laboratory in the INSA school in Lyon France. He then did a 1.5 years post doc at McMaster University Ontario Canada and was appointed research associated by the french CNRS in his previous laboratory Mateis. Since his appointment in 1997, Maire is carrying research in two main fields: ductile fracture of metals and deformation of cellular materials. He has a world renown experience in the use of non destructive X-ray imaging methods coupled with in situ thermal or mechanical solicitation to observe the mechanisms.
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Mar 25
Friday

On the Performance of Multilayers Used as Monochromators for Coherent X-ray Imaging with Hard Synchrotron Radiation

Speaker: Alexander Rack, European Synchrotron Radiation Facility
XSD Presentation
401/A1100 @ 1:30 PM
View Description
We present a systematic study in which multilayers of different composition (W/Si, Mo/Si, Pd/B4C, Ru/B4C, W/B4C), periodicity (from 2.5 to 5.5 nm), and numbers of layers have been characterized. Particularly, we investigated the intrinsic quality (roughness and reflectivity) as well as the performance (flatness and coherence of the outgoing beam) as a monochromator for synchrotron radiation hard X-ray micro-imaging. The results indicate that the material composition is the dominating factor for the performance. Current experiments at 32-ID of APS are foreseen combined with a round-robin of different multilayer laboratories to verify and understand the influence of the material composition. This is of high importance for synchrotron-based hard X-ray imaging which has become a widely applied tool for probing the microstructure of bulk samples. The high spatial resolution and different contrast modalities available here strongly depend on using coherent beams from highly brilliant sources. In order to satisfy the demand for a high flux of quasi-monochromatic photons, multilayer-coated mirrors are commonly used as monochromators. This comes at the cost of reduced energy resolution and stronger non-uniformities in the incoming beam profile. By helping scientists and engineers specify the design parameters of multilayer monochromators, our results can contribute to a better exploitation of the advantages of multilayer monochromators over crystal-based devices for X-ray imaging.
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Mar 25
Friday

Studies of Iron-Carbon-Oxygen Phases at Extreme Conditions: Single Crystal and Multigrain Analysis, Spin Transition, Synthesis of High Pressure Phases

Speaker: Barbara Lavina, HiPSEC and Department of Physics and Astronomy University of Nevada, Las Vegas
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Phases of iron, carbon and oxygen are abundant planetary constituents, they include the most important magnetic materials, have strong interactions with the biosphere, and are extensively used in industry and technology. Results of robust structural analysis at high pressure, including the characterization of electronic phase transitions, and high pressure-temperature phases will be presented. The power and robustness of the synchrotron high pressure single-crystal diffraction technique will be illustrated in two case studies: the pressure induced spin pairing transition in siderite, FeCO3, and the bond compressibility in magnetite. The spin pairing transition in FeCO3 is associated with exceptional phenomena, such as the formation of spin-like domains differing by 10 % in volume. This is the first report of such an effect at high pressure and is interpreted as the effect of a large elastic cooperative component of adjacent clusters on the spin pairing. We could also assess the gain of intense coloration and the reduction of thermal vibrations in the low spin state. Magnetite is one of the first and most investigated phases at high pressure, a survey of the literature illustrates the challenge to model the behavior and properties of strongly correlated systems at extreme conditions. It is apparent that a correct and robust structural analysis is a precious basis for the interpretation of spectroscopic data and physical properties.

High pressure and temperature phases were synthesized in the diamond anvil cell, often as relatively large grains. The characterization of these phases with spatially resolved single crystal and multi-grain approaches allows robust indexing and solution of fairly complex structures, it also provides information on the homogeneity of the synthesis products. Our preliminary results suggest a pressure effect on the iron-carbon redox equilibrium. Carbon, one of the most important elements for the Earth’s dynamic and differentiation, might be reduced at depth through redox exchanges.

Technical difficulties and solutions related to the measurement of structure factors at high pressure with highly focused synchrotron radiation will be briefly discussed.
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Mar 24
Thursday

A Winning Pair to Study Solid Pharmaceuticals: The 11-BM Synchrotron Beamline at the APS & The EXPO 2009 Software

Speaker: Robert J. Papoular, IRAMIS / Leon Brillouin Laboratory, CEA / CEN-Saclay, France
XSD Presentation
401/A1100 @ 2:00 PM
View Description
The on-going development of sophisticated high-resolution synchrotron X-ray powder diffraction beamlines, in combination with advancement in analysis software, makes it possible to solve structures for more and more complex pharmaceutical crystalline materials ab-initio. Increased complexity may arise from greater number of degrees of freedom of the molecular moieties or from the reduced symmetry of the crystal. The 11-BM synchrotron powder diffraction beamline at the Argonne Advanced Photon Source, put into operation in 2007, provides the high throughput and the high resolution required to investigate weakly scattering drugs, while minimizing the overlap of Bragg peaks in the measured powder patterns in order to allow for the indexing of low-symmetry unit cells. The subsequent data analysis using the single software package EXPO 2009: (i) indexes the patterns, (ii) ranks suitable crystal symmetries [i.e., space groups] and (iii) solves the structure using simulated annealing for flexible molecular models of linked rigid groups.

The power of 11-BM and EXPO2009 in combination is readily demonstrated on examples pertaining to two important powdered pharmaceuticals: (1) the chemotherapy agent Tegafur C8H9FN2O3 [β-form] and (2) the local anesthetic Tetracaine Hydrochloride (TCHC C15H25O2N2+,Cl-). Monoclinic β-Tegafur was initially solved from single-crystal data by Nakai et al. and reported in 1986 in the Chem. Pharm. Bull. The structure of triclinic TCHC was first published in 2002 by Nowell et al. in the New J. Chem. The synchrotron powder dataset was then indexed with DICVOL (Boultif & Loüer, 1991) and subsequently solved with DASH (David & Shankland, 2001).

A third and final example relates to the propensity for polymorphism of pharmaceutical drugs. A key feature of the 11-BM beamline is its low/high-temperature in-situ capability. In a recent study on the modifications of TCHC, two distinct patterns were obtained at room temperature from the same initial powdered sample. Polymorphism or blunder ? This issue was eventually resolved by slowly varying temperature at 11-BM and watching one pattern gradually transform into the other. Both were indeed successfully indexed by the N-TREOR09 option of the EXPO2009 package.

This work is done in collaboration with Dr. Brian H Toby [ APS / ANL / USA ] and Prof. Viatcheslav N Agafonov [ Faculté de Pharmacie, Université de Tours, France ].

Reference :
A. Altomare, M. Camalli, C. Cuocci, C. Giacovazzo, A. Moliterni and R. Rizzi "EXPO2009: structure solution by powder data in direct and reciprocal space" J. Appl. Cryst. (2009) 42, 1197-1202.
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Mar 24
Thursday

Solving the Atomic Structure of Complex Interfaces and Thin Film Systems: Current Challenges and Advances in Surface X-ray Diffraction

Speaker: Christian M. Schleputz, Physics Department, University of Michigan
XSD Presentation
401/A1100 @ 10:00 AM
View Description
The recent advent of highly reliable area detectors has afforded significant advances for Surface X‐ray Diffraction (SXRD) experiments, especially in terms of speed and reliability. It is now possible to record thousands of structure factors within a few hours, making it feasible to collect complete data sets of complex heterostructures and thin film systems containing dozens of atoms per surface unit cell. Within typical beamtime durations, one can therefore measure an entire series of samples to systematically investigate structural changes as a function of various physical parameters, such as, for example, film thickness, composition, or substrate-induced strain.

With the availability of such large data series arises the need for fast and reliable data analysis tools. Due to the complexity of the investigated systems, traditional least squares model fitting approaches are bound to fail. I will present various examples where we have successfully employed direct methods for SXRD and/or genetic algorithms to overcome this limitation and solve the structure of large surface unit cells with excellent reliability. These include the surface structure of ZnO wafers with and without metal contact layers, the initial growth mode of (LaSr)MnO3 films as a function of film thickness, the interface between LaAlO3 and SrTiO3 and the reconstruction of the 3-dimensional electron density and atomic structure of a 45 Å thick YBa2Cu3O7 film. All experiments were performed either at the APS (Sectors 13 ID-C, BM-C and 33 ID-D) or the Swiss Light Source (Materials Science Beamline X04SA), using a PILATUS 100K pixel detector. Based on these examples, I will try to highlight the recent advances and point out the current challenges and open questions that need to be addressed in order to push these methods further.
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Mar 17
Thursday

Ultrafast XAS/XES with Current and Future Light Sources

Speaker: Wojciech Gawelda, The European XFEL
XSD Meeting
432/C010 @ 12:00 PM
Mar 14
Monday

Origin of Giant Saturation Magnetization in Fe16N2: Beyond Slater-Pauling Curve and a 40-Year Mystery in Magnetic Materials and Magnetism

Speaker: Prof. Jian-Ping Wang, University of Minnesota
XSD Presentation
440/A105 @ 3:00 PM
View Description
The search for material with higher saturation magnetization becomes more crucial for high magnetic-energy-product permanent magnet and extremely high areal density magnetic recording. However, this effort has been fundamentally shadowed for decades by the famous Salter-Pauling curve, which is based on the classical itinerant magnetism theory. Recently we reported the successful fabrication and fundamental understanding of the origin of the giant saturation magnetization of Fe16N2 films to tackle the traditional wisdom on this topic. So far, the highest Ms value that can be predicted by first principles calculation is 2.45 T for Fe65Co35 alloy. About 40 years ago, Kim and Takahashi firstly reported a material, Fe16N2, with a giant saturation magnetization that surpasses the Fe65Co35 alloy by 20%. About 30 years ago, Sugita et al. published a study and claimed that the single phase Fe16N2 compound does exhibit giant saturation magnetization. That publication was immediately followed by many others. Unfortunately, many of them were not able to reproduce the giant saturation magnetization results or even claimed there is no giant saturation magnetization in this material. At the annual conference on Magnetism and Magnetic Materials in 1996, a specific symposium was organized on the topic of Fe16N2. Both theoreticians and experimentalists in the world presented their work. The papers were published in J. Appl. Phys. 79 (1996). No decisive conclusion was drawn on whether it has giant saturation magnetization. The critical point was that there is no available theory to rationalize the existence of the giant saturation magnetization in Fe16N2 at that time. Since then, this research topic has been dropped by most of magnetic researchers. Fe16N2 remains a mystery among magnetic researchers before our work. In this talk, I will present our systematic effort on the Fe16N2 by collectively and successfully addressing the four missing pieces on this topic through our seven years’ effort. The highlight of this work will be our recent discovery of the origin of the giant saturation magnetization of Fe16N2. Several findings that we considered as key building blocks to this research topic are reported in details: 1) repeatable fabrication of partially ordered Fe16N2 samples with giant saturation magnetization by using a unique low-energy and plasma-free sputtering process; 2) discovery of the local 3d electron states in Fe16N2; 3) finding of the role of Fe6-N octahedral clusters; 4) finding of the N ordering effect on the magnetic behavior; 5) first principles calculation and rational of the formation of the giant saturation magnetization in Fe16N2; 6) physical reasons about the inconsistency of the reported experimental results by different groups. Progress of several other Nanomagnetics and Spintronics research programs in my group will be briefly introduced by end of the seminar for any potential collaboration: 1) first demonstration of detection of cancer biomarkers in unprocessed human serum and urine samples by a novel GMR- and high-moment-nanoparticle sensing scheme; 2) first demonstration of the integration of magnetic tunnel junction (MTJ) with magnetic quantum cellular automata (MQCA) for non-volatile logic.

About the speaker:
Jian-Ping Wang is a full professor at Electrical and Computer Engineering Department, and a leader on experimental applied magnetic and spintronics research being the associate director of the Center for Micromagnetics and Information Technologies (MINT) at University of Minnesota. He is also a graduate faculty member of Physics Dept and Chemical Engineering and Materials Science Dept at University of Minnesota. His current research programs focus on searching, fabricating and fundamentally understanding new nanomagnetic and spintronic materials and devices. He has built and run the Magnetic Media and Materials program in Data Storage Institute, Singapore, as the founding program manager, from 1998 to 2002. He received the INSIC technical award in 2006 for his pioneer work in exchange coupled composite magnetic media. Information Storage Industry Consortium (INSIC) is the largest industry magnetic research organization in the world with members of Seagate, Hitachi, WDC, IBM, etc. He has authored and co-authored more than 200 publications in peer-reviewed top journals and conferences and hold 13 patents.
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Mar 14
Monday

As if life is not complicated enough already . . . Prospects of Combining Synchrotron Radiation with Scanning Probe Microscopy

Speaker: Volker Rose, XSD/MIC
XSD Presentation
440/A105 @ 1:30 PM
Mar 3
Thursday

Frustrated Spin Dynamics and Aging on a Triangular Lattice - Magnetic Behaviour of Li(NiCoMn)O2

Speaker: Magnus Wikberg, The Anstrom Laboratory, Uppsala, Sweden
XSD Presentation
432/C010 @ 11:00 AM
View Description
Layered transition metal oxides of α-NaFeO2-type structure have been of historical interest from both theoretical and experimental point-of-views. For instance, LiNiO2 was initially predicted as being the first realization of a resonant valence bond (RVB). Even though a RVB state has not been realized in LiNiO2, the magnetic ground state (in this and other equistructural materials) has been controversial and is currently under considerable investigation. Interests in Li layered compounds have also prompted a tremendous research effort due to their application in Li-ion batteries. Previously, the cathode consisted of LiCoO2, but presently, one seeks to partially or fully replace Co with other transition metal ions while maintaining the structural stability and increasing the capacity. The replacement is primarily motivated by cost and environmental concerns regarding Co. The magnetic properties in several compounds of Li(NixCoyMnz)O2 have been investigated. The materials show a ferrimagnetic re-entrant cluster glass behaviour with spin frustration in both 2 and 3 dimensions. The peculiar magnetic behaviour is believed to originate from the degree of cationic mixing (Ni2+ in the Li-layer), the interplay with the Li-deficiency, as well as the cluster size in the material. Additionally, a possible link between low temperature magnetic order and frustration and cathode performance at room temperature will be presented.

[1] J. M. Wikberg et al. J. Appl. Phys., 180 083909 (2010)

[2] J. M. Wikberg et al. Phys. Rev. B, 81 224411 (2010)

[3] I. Saadoune et al. Solid State Ionics 178, 1668 (2008)
[ Hide ]
Feb 25
Friday

Morphology and Internal Structure of Nanofibers

Speaker: Zhenxin Zhong, Dept. of Polymer Science, University of Akron
XSD Presentation
432/C010 @ 11:00 AM
View Description
In the past decade, polymer nanofibers have received significant attention because of their potential use in a variety of filtration, medical, electronic, and composite applications. The macroscopic properties of a fiber containing system depend mainly on the properties of the individual fibers. In this study, the effect of the electrospinning process on the diameter, morphology, and crystallization behaviors of individual electrospun polymer nanofibers was investigated. Control of electrospinning process produced fibers with various morphological forms. Fibers that were wrinkled, coiled, branched or split were obtained when different forms of instability dominated in the electrospinning process. The high ratio of stretching (as much as 105) during the electrospinning process, which is similar to uniaxial mechanical stretching, aligns the polymer molecules along the fiber axis. The rapid evaporation of solvent during electrospinning process creates small and imperfect crysta! llites in the electrospun fiber, which can be perfected by an annealing process. Fibers annealed at elevated temperature forms plate-like lamellar crystal tightly linked by interlamellar tie molecules. Ultra-fine nanofibers with cross-sections containing only a few polymer molecules were obtained and imaged by high-resolution transmission electron microscope. Electrospun nanofibers suspended on a holey carbon film showed features of individual polymer molecules. Electrospinning provides an easy and simple way to produce ultrafine nanofiber specimens for studying polymer properties at nanometer or molecular scale.

A promising and innovative process, called nanofiber by gas jet (NGJ) process, uses hot gas to make carbon nanofiber from mesophase pitch. Carbonized or graphitized nanofibers produced at different process parameters were characterized by SEM, TEM, electron diffraction, and XRD techniques. By varying the operating parameters of the NJG process, carbon thin fibers with mean diameters ranging from 50 to 1000 nanometers were produced. The microstructure of NGJ carbon nanofiber annealed at different temperatures was investigated. The NGJ process offers the production of carbon fibers with valuable structural, thermal, and electrical properties at cost levels as much as an order of magnitude less than the current processes.
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Feb 24
Thursday

Picosecond Pump-Probe X-ray Liquidography (Solution Scattering) to Probe Solution-Phase Structural Dynamics

Speaker: Hyotcherl "Harry" Ihee, Center for Time-Resolved Diffraction
XSD Presentation
401/A1100 @ 10:00 AM
View Description
Synchrotron-based picosecond time-resolved X-ray liquidography (solution scattering) has been established as a unique tool to study spatiotemporal reaction dynamics of small molecules and proteins in solution. Using ultrashort optical pulses to trigger a reaction in solution and detecting time-resolved X-ray diffraction signals to interrogate the molecular structural changes, time-resolved X-ray liquidography (TRXL) can provide direct structural information generally difficult to extract from ultrafast optical spectroscopy such as the temporal progression of bond lengths and angles of all molecular species including short-lived intermediates over a wide range of times, from picoseconds to milliseconds. Application examples on spatiotemporal kinetics and structural dynamics of a halomethane, a triatomic molecule, haloethanes, and an organometallic catalyst are presented. In addition, we demonstrate tracking of protein’s structural changes in solution using TRXL. TRXL permitted us to investigate the tertiary/quaternary conformational change of various heme proteins. Structural analysis to extract detailed structural information from the time-resolved solution scattering data has been developed. We can extract a vivid view of the helices movements by applying we performed structure refinement aided by Monte Carlo simulations. Due to lack of the long-range orders and random orientation of molecules in solution, a solution scattering pattern generally exhibits isotropic, smooth oscillation profile, containing much less information content compared with diffraction patterns from crystalline samples. Enhancing information content would allow extracting more accurate structures and dynamics. As one of the first steps toward this goal, here we investigate the possibility of increasing the information content by generating anisotropic X-ray scattering from photo-selectively aligned molecules by manipulating the polarization orientation of the pump laser pulse relative to the X-ray propagation direction. By providing insights into the structural dynamics of proteins functioning in their natural environment, TRXL complements and extends results obtained with time-resolved spectroscopy and X-ray crystallography.
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Feb 24
Thursday

Deciphering Subtlety at Interface: Insights from Surface/Interface X-ray Scattering

Speaker: Hua Zhou, Chemical Science and Engineering Division, Argonne National Laboratory
XSD Presentation
401/B4100 @ 10:00 AM
View Description
Ubiquitous in a wide range of nature processes and technologies, a subtle modification (e.g. structure, element, charge…) near an interface can have a decisive effect on emerging phenomena of the collective as well as each individual. In this talk, I will demonstrate how to decipher such subtlety by utilizing synchrotron surface/interface x-ray scattering techniques boosted with phase retrieval direct methods. This is essential to our ability to provide a quantitative and realistic description of the interfacial boundaries that encounter in both fundamentally and technologically important systems. Two examples on addressing compelling interface phenomena in the frontier of explorations of advanced materials will be presented. In the first case, I will describe an atomic scale understanding of how water meets graphene, a model fluid-solid interface system, by integrating high resolution x-ray reflectivity and various computational approaches with different level of theories. This combination allows us to illuminate why the strained graphene layer interact! s more strongly with water than intrinsic ones and what factor mediates the macroscopic wetting behavior as observed. In the second case, I will describe the work on accurate determining structural modifications in near-interface layers of complex oxide thin films by introducing an improved phase-retrieval method with unprecedented speed of convergence and precision. Differentiating at the atomic layer level the complicated structural and elemental profile of buried interfaces in oxide heterostructures will be also briefly discussed with the most recent experiments, taking advantage of resonant anomalous scattering.
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Feb 23
Wednesday

Mapping Phonon Dispersion Relations and Anomalies with X-ray Scattering

Speaker: Tai C. Chiang, University of Illinois at Urbana-Champaign
XSD Forum
433/C010 @ 12:00 PM
View Description
X-ray scattering has proven to be a powerful approach for studying phonon dispersion relations and phonon anomalies related to phase transitions. There are two closely related and complementary techniques: TDS (thermal diffuse scattering) and IXS (inelastic x-ray scattering). IXS measures the phonon energy directly, but the signal intensity is very low. In contrast, TDS does not rely on energy resolution and the signal intensity is much higher; the phonon energy is extracted through measured intensity distributions in k space and/or intensity variations as a function of temperature. This talk will review recent studies of various prototypical systems including Cu (a simple metal), SrTiO3 (a prototypical complex oxide), Pu (a 5f metal with a complex electronic response), and MgCNi3 (a superconductor), etc.
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Feb 22
Tuesday

Interlattice Interactions of a Molecule-based Magnet with Interpenetrating Sublattices

Speaker: William Shum, Cornell University
XSD Presentation
431/C010 @ 1:00 PM
Feb 17
Thursday

X-ray Focusing Lenses for Medical and Materials Applications

Speaker: Dip Mahato, Intel Corporation
XSD Presentation
401/A1100 @ 10:00 AM
View Description
Polycapillary focusing lenses are used to collect the divergent x-rays emitted from conventional x-ray tubes and redirect them by multiple total reflections in the individual capillaries to form an intense focused beam. These lenses are routinely used in microbeam x-ray fluorescence (MXRF) analysis. We have investigated their potential application to powder diffraction, and focused beam orthovoltage cancer therapy. X-ray therapy is conventionally performed with very high energy beams, in the 1 MeV range, partly in order to reduce the skin dose. For any normally divergent beam, the dose is necessarily highest at the entry point, and decays exponentially into the tissue. To reduce the skin dose, high energy beams, which have long absorption lengths, are employed, and rotated about the patient to enter from different angles. This necessitates large expensive specialized equipment. With a focused beam, it would be possible to concentrate the dose within the patient. Since this is inherently skin dose sparing, lower energy photons could be employed. A primary concern in applying focused beams to therapy is the question of whether the focus would be maintained despite Compton scattering within the tissue. To study this effect, we have characterized the transmission, focal lengths and focal spot sizes of two polycapillary focusing lenses as a function of photon energy. The effects of tissue-equivalent Lucite (C5H8O2) phantom thickness on the focal spot size will be presented. Focused beam transmission, scatter fraction and percentage dose vs depth will be discussed. For powder diffraction, the polycapillary optics provide clean Gaussian peaks, which result in effective angular resolution that is much smaller than the peak width due to the convergent beam. The trade off between collection time and resolution will be briefly discussed.
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Feb 16
Wednesday

Structure and Dynamics of Lipid Membranes - An X-ray and Neutron Study

Speaker: Gang Chen, University of California, San Diego
XSD Presentation
431/C010 @ 11:00 AM
View Description
The model phospholipid membranes are of considerable scientific and practical interest because they provide a window into understanding the thermodynamics for phase separation of membrane components in a living cell. Within this framework, intense debate currently surrounds the understanding of the fundamental basis for the formation and dynamics of the so called raft micro-domains, which have been broadly implicated in many membrane functions. Here we report an unusual consequence of a physical property of the membrane-substrate interface in influencing phase separation in supported bilayers. The planarity of the interface constrains the head-groups of the lower leaflet to organize in a single topologically-defined plane. As a consequence, we find that the topology of the outer leaflet becomes strongly corrugated in multicomponent bilayers. Influences of such imposed physical topology on phase separation are also discussed. The effect of the membrane-substrate interaction is further demonstrated in a multi-stack bilayer system. Off-specular diffuse scattering shows a kink which corresponds to the cutoff wave vector of surface capillary waves. In order to circumvent the substrate proximity effect and fully lift the dynamics of lipid membranes, we studied lipid membrane multilayers in humidity. Both x-ray and neutron scattering techniques are applied to study their phase transition. Below the phase transition temperature, a new phase which is related to the raft formation appears with distinct bilayer spacing and pops off from the lipid mixture. We also observed for the first time the dynamics of lipid membrane multilayers in humidity with X-ray Photon Correlation Spectroscopy (XPCS).
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Feb 14
Monday

Efficient Materials Innovation: First-Principles Design of Multifunctional Oxides

Speaker: James M. Rondinelli, Argonne Scholar, XSD/MM
XSD Presentation
401/A1100 @ 1:30 PM
View Description
There are two main routes to spur materials discoveries for low-power electronics and sustainable energy technologies: synthesis of new compounds with enhanced functionalities or direct design of artificial materials with emergent phenomena. In this talk, I will discuss our recent work on the rational design of multifunctional oxides and how we deterministically engineer new materials with targeted functionalities by elucidating atomic structure - electronic property relationships using first-principles density functional calculations. I will describe how we combine group theoretical tools and crystal chemistry with state-of-the-art computational tools to disentangle complex and often competing interactions. As an application of this structure-driven view of electronic properties, I will discuss our advances in two multifunctional oxide systems: (i) an electric field-tunable magnetoelectric multiferroic (a material with switchable and coupled ferromagnetic and ferroelectric properties), and (ii) a strain-induced phonon instability which leads to a metal insulator transition in an oxide heterostructure. I conclude by arguing that when these electronic structure-driven design approaches are leveraged with new synthesis methods, substantial progress can be achieved toward next generation electronics and fuel sources.
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Feb 14
Monday

Functional Carbons for Energy Storage

Speaker: Meixian Wang, Purdue School of Engineering
XSD Presentation
432/C010 @ 11:00 AM
View Description
Graphitic carbons with three-dimension hexagonal crystalline long-range order are widely used in our society. The liquid phase carbonization is an important method to produce the graphitic carbons. This talk will start with a brief introduction of the methods for producing carbons, and then focus on different carbons produced from the liquid carbonization process including mesocarbon microbeads (MCMB) and mesophase pitch along with their applications in the fuel cells, lithium batteries and supercapactitors. Graphene, with a theoretic surface area 2560 m2/g, is the building block of graphitic carbons. However, like the dispersions of other nanomaterials with high aspect ratios, the grapheme sheets usually aggregate and form irreversibly precipitated agglomerate with a surface area as low as 70 m2/g (due to the van der Waals interactions between the neighboring graphene sheets) after solvents being removed from the dispersion. I will present the new method we developed in our Lab for producing graphene sheets in dry form with a surface area as high as 1860 m2/g, which is much higher than that currently, reported, and the application of such graphene sheets in supercapacitors will also be discussed.
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Feb 10
Thursday

Compression Mechanism Determination using Single Crystal Diffraction

Speaker: Lauren A. Borkowski, Stony Brook University
XSD Presentation
402/E1100 @ 11:00 AM
Feb 10
Thursday

Development of Multi-layer Optics for EUV Astronomical Observation and Soft X-ray K-B Microscopy in Tongji University

Speaker: Jingtao Zhu
XSD Presentation
401/A1100 @ 10:00 AM
View Description
Recent development of multi-layer optics and its applications in extreme ultraviolet (EUV), soft X-ray ranges in China will be introduced in this talk. Firstly, multi-layer mirrors were developed for solar observation and earth’s magnetosphere observation at EUV wavelength region. Three kinds of optics have been developed: The first one is Mo/Si multi-layer mirror, designed for solar Fe-XII emission line at wavelength of 19.5nm. For solar He-II radiation at 30.4 nm, high reflective mirror was designed using Mg-based multi-layer. Furthermore, aperiodic multi-layer mirror was developed for wide angular range of 12-21˚. The third multi-layer mirror was a bi-functional mirror with high reflectivity for He-II emission line (30.4nm) but suppressing He-I emission line (58.4nm) in astronomy observation, which will replace the traditional combination of periodic multi-layer and the fragile thin-film filter. This will be more safety in satellite launching. Part II will introduce some multi-layer optics for Kirkpatrick-Baez (K-B) microscopy. Mono-layer, multi-layer, and aperiodic multi-layer were deposited onto K-B mirrors, respectively. In order to overcome the difficulty in alignment K-B microscopy in soft X-ray, Bil-periodic multi-layer mirror was designed as working at both at Ti Kα line (4.75 keV, soft X-ray) and Cu Kα line (8.05 keV, hard X ray). Using this mirror, the soft X-ray K-B system can be aligned conveniently in air using hard X-ray instead of in vacuum. All these multi-layer mirrors were all prepared by magnetron sputtering systems in Institute of Precision Optical Engineering (IPOE), Tongji University and measured at National Synchrotron Radiation Laboratory (NSRL), China. Keywords: Multi-layer mirror; EUV astronomy; soft X-ray K-B microscopy
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Feb 9
Wednesday

Magnetism and Superconductivity under Extreme Pressure in RareEarth Elements

Speaker: Wenli Bi, Washington University
XSD Presentation
431/C010 @ 11:00 AM
View Description
In the rare earth elements, only La superconducts at ambient pressure. All but two of the elemental rare earth metals have well defined localized magnetic moments originating in the 4f shell which prevent superconductivity. Under successively higher pressures the magnetic state may change markedly as one 4f-electron after another is transferred out of the local orbital into the conduction band; at sufficiently high pressures, a magnetic 4f-band may form which broadens until the magnetism is destroyed. When the strong local magnetic moment is destroyed,superconductivity may appear. The pressure-induced changes in magnetic and superconducting state can be studied from measurements of magnetic susceptibility, electrical resistivity, and synchrotron x-ray techniques. High pressure studies focused on Eu’s structure, valence and magnetism under Mbar pressure will be discussed.
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Feb 8
Tuesday

Measurement System for the High Pressure Characterization of Materials

Speaker: Matthew Jacobsen, University of Nevada Las Vegas
XSD Presentation
432/C010 @ 11:00 AM
View Description
Thermoelectric materials have long been investigated for possible use as renewable energy sources. Despite the usefulness of these materials, research involving the use of pressure to study their properties has only recently become an area of interest. The work presented will discuss a setup designed to measure the properties important to the efficiency of thermoelectric materials (electrical resistivity, thermal conductivity, and Seebeck coefficient) with pressure. Results will be presented on calibrant samples (zinc, nickel, and almandine garnet), to demonstrate the capabilities of the system, and on some selected thermoelectric materials of interest. This data will be compared with the results of structural measurements to investigate the high pressure phases for thermoelectric efficiency.
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Feb 7
Monday

Novel Chemistry of Known Elements: Pressure Induced Phenomena Enlightened with the Synchrotron Light

Speaker: Olga Shebanova, Carnegie Institution of Washington, Geophysical Lab, HPCAT, Argonne National Laboratory
XSD Presentation
401/B4100 @ 11:00 AM
View Description
Application of extreme conditions to the matter not only helps to understand intrinsic properties of materials but allows uncovering the potential of the matter in response to high pressures and temperatures. That knowledge is used for an explanation of phenomena occurring at naturally high P and T (e.g. planets interior) as well as for production of advanced materials possessing unique and often also tunable properties. High pressure is not only an additional parameter for tuning properties in existing materials but also a powerful tool for creating novel compounds. This presentation will highlight pressure induced phenomena, which lead to the new “high-pressure” chemistry of alkali metals and transition metal series, and report the development of the new technique of combined synchrotron x-ray diffraction and absorption for high-pressure studies of electronic and structural transitions in materials in situ.
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Feb 7
Monday

Modeling and Monte Carlo Simulation of Electron Interaction with Solid Surfaces

Speaker: Mihaly Novak, Universite Libre de Bruxelles
XSD Presentation
433/C010 @ 10:00 AM
View Description
Electrons with low and medium energy strongly interact with electros in a solid. Due to these interactions the probing electron can lose energy very quickly resulting in the high surface sensitivity of the electron spectroscopy based surface analytical techniques like REELS (Reflection Electron Energy Loss Spectroscopy), XPS (X-ray Photoelectron Spectroscopy) or XAES (X-ray Auger Electron Spectroscopy). The most probable electron-solid interaction leading to an energy loss of the probing electron is the collective excitation of free or nearly fee electrons in solids i.e. the plasmon excitation. The nature of these charge density oscillations in the near surface region of solid is different from those taking place deep inside a solid, as a consequence of the difference between the electronic structure of these regions of the sample due to the presence of the vacuum-surface boundary. The existence of surface plasmons was predicted by Ritchie in 1957 [1] and proven experimentally by Powell in 1959 [2,3]. In spite of the fact that these results were published more than 50 years ago, an accurate model for the near surface electron transport, including surface plasmon excitations has not been developed and is still not available at the moment although this process plays an important role in quantitative analytical use of electron spectroscopic techniques due to their high surface sensitivity. The problems of electron-surface inelastic interactions will be introduced and discussed in the first part of the presentation as well as the available simulation models for near surface electron transport including some important points of their implementations [4-12]. Then the capacity and efficiency of the most accurate recently developed simulation model will be presented through examples and results. Results derived from Monte Carlo simulation based quantitative analysis of REELS and XPS experimental data will be presented in the last part of the presentation in order to show that accurate simulation of electron transport processes can also help us in a more exact interpretation of XPS experimental data.
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Feb 4
Friday

In-situ X-ray Scattering and Spectroscopy Studies of Model Nanocatalysts

Speaker: Sungsik Lee, X-ray Science Division
XSD Presentation
401/A1100 @ 11:00 AM
View Description
To develop tailored catalysts, it is essential to combine sophisticated fabrication and characterization tools to understand the behavior of the catalyst under realistic reaction condition. Thus, the evolution of catalyst’s size/shape and its chemical state to be monitored during the course of the reaction using in situ characterization tools. The high surface sensitivity of grazing incidence techniques, including GISAXS (Grazing incidence small angle X-ray scattering) and GIXAS (Grazing incidence X-ray absorption spectroscopy) enables to study the chemical state and morphology of metal nanoparticles deposited on flat substrate with less than one tenth of monolayer coverage. Recently published series of reports1-5 show successful employment of various combinations of the GISAXS, GIXAS and TPR (temperature programmed reaction) based on a unique experimental setup.

In this study, origin of morphology transformation and chemical state changes during the propylene epoxidation on silver catalyst and cyclohexene dehydrogenation on cobalt catalyst were investigated in terms of metal-support interaction and size effect by in-situ GISAXS/GIXAS/TPR. The catalytic activity of oxide-supported metal nanoclusters strongly depends on their size and support. The evolution of the oxidation state of the metal cluster during the reaction reveals that metal-support interaction plays a key role in the performance of the small metal clusters.
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Feb 3
Thursday

Magnetization Dynamics in Nano-contact Spin Torque Oscillators; Solitonic Bullets and Propagating Spin Waves

Speaker: Stefano Bonetti, Royal Institute of Technology, Sweden
XSD Presentation
431/C010 @ 11:00 AM
View Description
Spin torque oscillators (STOs) are a novel class of microwave devices receiving intense interest, both from a fundamental point of view (spin wave dynamics in reduced dimensions and in highly nonlinear regimes), and from an applied perspective (current controllable broad-band microwave generation in nanosize devices). In this talk, I will focus on the spin wave dynamics in nanocontact STOs from an experimental and theoretical point of view.

A custom-made high frequency (up to 46 GHz) in large magnetic fields (up to 2.2 T) setup has been built for the microwave characterization of the devices. A unique feature of this setup is the capability of applying magnetic fields at any direction qe out of the sample plane, and with high precision.

This is particularly important, because the (average) out-of-plane angle of the STO free magnetic layer has fundamental impact on spin wave generation and STO operation. By observing the spin wave spectral emission as a function of qe, we find that at angles qe below a certain critical angle qcr, two distinct spin wave modes can be excited: a propagating mode, and a localized mode of solitonic character (so called spin wave bullet). The experimental frequency, current threshold and frequency tuneability with current of the two modes can be described qualitatively by analytical models and quantitatively by numerical simulations. We are also able to understand the importance, so far underestimated, of the Oersted field in the dynamics of nanocontact STOs. In particular, we show that the Oersted field strongly affects the current tuneability of the propagating mode at subcritical angles, and it is also the fundamental cause of the mode hopping between the two modes observed in the time-domain. This mode hopping has been observed both experimentally using a state-of-the art real-time oscilloscope and corroborated by micromagnetic simulations. Micromagnetic simulations also reveal details of the spatial distribution of the spin wave excitations.

By investigating the emitted power as a function of qe, we observed two characteristic behaviors for the two spin wave modes: a monotonic increase of the power for increasing out-of-plane angles in the case of the propagating mode; an increase towards a maximum power followed by a drop of it at the critical angle for the localized mode. Both behaviors are reproduced by micromagnetic simulations. The agreement with the simulations offers also a way to better understand the precession dynamics, since the emitted power is strongly connected to the angular variation of the giant magnetoresistance signal. We also find that the injection locking of spin wave modes with a microwave source has a strong dependence on qe, and reaches a maximum locking strength at perpendicular angles. We are able to describe these results in the theoretical framework of non-linear spin wave dynamics.
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Jan 28
Friday

Supramolecular Structure of Inclusion Complexes of β-cyclodextrin with PEO-b-PPO-b-PEO Triblock Copolymers

Speaker: Chi-Chun Tsai, Dept. of Polymer Science, University of Akron, Ohio
XSD Presentation
432/C010 @ 11:00 AM
Jan 25
Tuesday

Structure and Property Relationship of Oriented Polymers by Solid-State Cross-Rolling

Speaker: Yankai Yang, Case Western Reserve University
XSD Presentation
432/C010 @ 11:00 AM
View Description
This study investigates the effect of orientation by solid state cross-rolling on the morphology of an amorphous polyamide and three crystalline polymers polypropylene (PP), high density polyethylene (HDPE) and Nylon 6/6 with polarized optical microscopy, atomic force microscopy, wide-angle X-ray scattering, small-angle X-ray scattering and dynamic mechanical analysis techniques. The effect of microstructure change on the macromechanical properties was then studied in uniaxial tension, indentation and puncture test conditions at both ambient temperature and a low temperature of -40°C and the improved mechanical properties and failure mechanism change was then explained with the morphology transformation with orientation for different polymers.
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Jan 24
Monday

Crystallization and Phase Transformation of Uric Acids

Speaker: Amanuel Zelellow, Georgetown University
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Uric acid, a major organic component in human kidney stones, crystallizes in an anhydrous (UA), a metastable dihydrate (UAD), a rare monohydrate, and an ionized monosodium urate forms in vivo. In the body, these crystals exhibit a variety of morphologies and colors which differ from laboratory grown uric acids. This motivated us to study the effect of several molecular dyes on the crystallization of UA and UAD. All cationic and neutral dopants investigated were included in UA and UAD crystals, while anionic dyes were excluded. At low concentrations, the dyes preferentially included in the {001} and {201} growth sectors of UA. In UAD, variable inclusion behaviors were encountered. Inclusions occurred on the {011} growth sector/ hillock, on the {102} growth sector, and non-specific inclusions were also observed. Most of the dyes induced morphological changes on UA and UAD crystals at higher concentrations. The amount of dyes included and absorption spectra of the dyes in the crystals of both UA and UAD were determined.

To better understand the microscopic effects of the dye impurities, the (100) face of UA crystals was studied in the presence of dye solutions by atomic force microscopy. From topographical imaging, effective growth inhibition along the c-direction was observed in the presence of the dyes. Incremental dye concentrations also pinned advancing steps and reduced the velocity of b-steps due to high impurity incorporation. These results complement what was observed in bulk UA crystal growth.
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Jan 21
Friday

Breakdown of Switchgrass Multiscale Structure during Dilute Acid Pretreatment

Speaker: Sai Venkatesh Pingali, Oak Ridge National Laboratory
XSD Presentation
401/A1100 @ 11:00 AM
View Description
Lignocellulosic biomass is abundant in nature as well as has the potential to play a major role in generation of renewable biofuels through its conversion to bio-ethanol. Unfortunately, lignocellulosic biomass is a complex biological composite material that shows significant recalcitrance towards the structural breakdown into sugars that is necessary for fermentation to bio-ethanol, making it a cost-ineffective feedstock. Small-angle neutron scattering (SANS) was used to obtain a better understanding of the morphology of the cellulose/lignin composite across atomic to sub-micron length scales during the industrially-relevant dilute acid pretreatment method on switchgrass and poplar. Results from dilute acid pretreatment demonstrate: (1) increase in the cross-sectional radius of the crystalline cellulose domains until it encompasses the entire elementary cellulose fibril; (2) decrease in the interconnectivity of the fibrils and formation domain boundaries observed that undergo no change during dilute acid pretreatment. Preliminary results from an in-situ dilute acid pretreatment study will also be presented. This ex-situ study clearly demonstrates that the dilute acid pretreatment increases cellulose crystallinity while opening the fibril network to allow easier enzyme penetration and causes lignin to precipitate as aggregates within the material.
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Jan 20
Thursday

The Light that Resonant Inelastic X-ray Scattering Sheds on High Tc Cuprates

Speaker: Jeroen van den Brink, Institute for Theoretical Solid State Physics
XSD Forum
433/C010 @ 12:00 PM
View Description
Resonant Inelastic X-ray Scattering (RIXS) provides direct access to elementary charge, spin and orbital excitations in complex oxides. As a technique it has made tremendous progress with the advent high-brilliance synchrotron X-ray sources. From the theoretical perspective the fundamental question is to which precisely which low-energy correlation functions RIXS is sensitive. I will show that depending on the experimental RIXS setup, the measured charge dynamics can include charge-transfer, phonon, d-d and orbital excitations [1,2]. RIXS also allows probing spin dynamics, in particular magnons and bi-magnons dispersions [3,4]. Based on these observations, I will discuss the novelties that RIXS reveals on the spin dynamics of High Tc cuprates [5].

[1] Ament et al. Rev. Mod Phys, in press; arXiv:1009.3630
[2] Forte et al., PRL 101, 106406 (2008).
[3] Braicovich et al., PRL 102, 167401 (2009).
[4] Ament et al., PRL 103, 117003 (2009).
[5] Braicovich et al., PRL 104, 077002 (2010).
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Jan 20
Thursday

Neutron Reflectometry for Magnetic Films and Bio-membranes

Speaker: Mikhail N. Zhernenkov, Los Alamos National Laboratory
XSD Presentation
431/C010 @ 11:00 AM
View Description
Two topics studied by neutron reflectometry will be presented. First, two experiments on electric field induced modification of magnetism will be reported. The change of the saturation magnetization of 18 nm-thick CoPd film immersed in an electrolyte will be discussed. We found a linear increase of film magnetization as a function of applied field. The change of the magnetization occurs within top 7.2 nm of the CoPd film. Then, first results on inducing ferromagnetism in a Pd thin film by applied electric field will be presented. Finally, we present the study of thermally excited in- and out-of-plane fluctuations (governed by capillary waves and bending modes) in a polymer supported single lipid bilayer in a liquid environment by means of neutron reflectivity and off-specular scattering. We found that as temperature is decreased from 37 to 25 °C the amplitude of the out-of-plane membrane fluctuation increases and the correlation length of the in-plane fluctuations decreases.
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Jan 19
Wednesday

High-Pressure Synchrotron X-ray: New Light for the Discovery at Extreme Conditions

Speaker: Yang Ding, Geophysical Laboratory, Carnegie Institution of Washington
XSD Presentation
401/A1100 @ 11:00 AM
View Description
High-pressure synchrotron science has led to significant advances across diverse scientific fields in recent decades. Its growth now is being more accelerated by the developments in diamond anvil cell methods coupled with more new cutting-edge synchrotron techniques. In this presentation, two selected highlights on the latest high-pressure synchrotron study of 3d and 4/5f compounds, as well as the developments of nano high-pressure synchrotron techniques are presented to illustrate both state-of-the-art as well as technical and scientific challenges. The results could have implication for a variety of problems in physics, materials science, and geoscience.
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Jan 17
Monday

Quasi In Situ Mossbauer Spectroscopic and XAFS Studies on FeB Nanoalloy for Heterogeneous Catalytic Dehydrogenation of Ammonia Borane

Speaker: Junhu Wang, Mossbauer Effect Data Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences
XSD Presentation
431/C010 @ 11:00 AM
View Description
Ammonia borane (AB in short, NH3BH3) with a hydrogen content of 19.6 wt % has attracted increasing attention as a promising hydrogen storage material. One of the challenges in its practical usage is how to improve its dehydrogenation ability. Among various approaches, the direct catalytic modification of solid phase AB reported by Chen’s group very recently has been proved to be a very exciting promising method.

In case of Fe-modified AB, the rate of hydrogen evolution from the Fe-modified AB is 5.8 times as that of pristine AB at a temperature as low as 60 °C with significant depression of induction period, sample foaming and toxic byproducts (borazine, NH3, etc.).

In this presentation, quasi in situ 57Fe Mössbauer and X-ray adsorption fine structure (XAFS) techniques are employed to identify the changes of Fe states during dehydrogenation process. The experimental results show that FeB nanoalloy is formed upon mixing AB with FeCl3 which probably functions as catalytic species in the dehydrogenation process.

References
[1] C.W. Hamilton, R.T. Baker, A. Staubitz and I. Manners, Chem. Soc. Rev. 38 (2009) 279.
[2] T. He, Z. Xiong, G. Wu, H. Chu, C. Wu, T. Zhang and P. Chen, Chem. Mater. 21 (2009) 2315.
[3] T. He, J. Wang, G. Wu, H. Kim, T. Proffen, A. Wu, W. Li, T. Liu, Z. Xiong, C. Wu H. Chu, J. Guo, T. Autrey, T. Zhang, P. Chen, Chem. Eur. J. 16 (2010) 12814.
[4] T. He, J. Wang, T. Liu, G. Wu, Z. Xiong, J. Yin, H. Chu, T. Zhang, P. Chen, Catal. Taday, submitted.
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Jan 12
Wednesday

Growth of Multiferroic Oxides by Molecular-beam Epitaxy

Speaker: June Hyuk Lee, Pennsylvania State University
XSD Presentation
440/A105 @ 11:00 AM
View Description
Multiferroic materials, which simultaneously exhibit ferroelectricity and ferromagnetism in a single phase, have recently attracted a great deal of attention due to their physical origin and potential applications. The key challenge in creating new multiferroics is finding materials that show both strong ferroelectricity and strong ferromagnetism, and also display a coupling between them so that the magnetoelectric response can be used to increase its functionality. This talk explores the growth and characterization of multiferroic oxides thin films by molecular-beam epitaxy (MBE) in order to understand the nature of multiferroism.

In the first part, I will discuss the adsorption-controlled growth of multiferroic BiMnO3 thin films by MBE. The pressure-temperature region for the adsorption-controlled growth region was calculated and experimentally established by reflection high energy electron diffraction and x‑ray diffraction. Under this growth region, I have grown phase-pure and epitaxial BiMnO3 films with w rocking curve full width at half maximum values as narrow as 11 arc sec (0.003°). The structural and magnetic properties of stoichiometric BiMnO3 films will be discussed.

In the second part, I will present the strain-induced multiferroism in EuTiO3 thin films via spin-phonon coupling. Controlling epitaxial strain in perovskite oxide thin films has been proposed by first-principles calculations as a new route to create multiferroics. Guided by these first-principles calculations, we confirmed that strained EuTiO3 films exhibit both ferroelectricity and ferromagnetism. Using epitaxy and the misfit strain imposed by an underlying substrate, I have strained EuTiO3 films to percent levels—far beyond where they would crack in bulk. EuTiO3 films were grown by MBE on a variety of substrates to alter the imposed strain. In particular, EuTiO3 films strained commensurately to (110) DyScO3 substrates are simultaneously ferroelectric and ferromagnetic, and in good agreement with theoretical predictions. Our result demonstrates that a single experiment parameter, strain, simultaneously controls multiple order parameters and is an alternative tuning parameter to composition for creating new multiferroics.
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Jan 10
Monday

Emergent Phenomena at Complex Oxide Interface: Electric Field Control Magnetism

Speaker: Pu Yu, University of CA, Berkeley
XSD Presentation
440/A105 @ 11:00 AM
View Description
Electric field control of magnetism has many potential applications in storage, sensors andspintronics. In this talk, I will present a unique method for realizing such control and reveal the mechanism behind in an all-oxide model system, in which ferromagnetism (FM) and ferroelectricity (FE) are coupled through an intermediate antiferromagnetic (AFM) order parameter. I will first discuss the magnetic coupling at the interface between FMLa0.7Sr0.3MnO3 and multiferroic (FE and AFM) BiFeO3, manifested as an enhanced coercive field and an exchange bias. Using x-ray magnetic circular dichroism, we have shown that the origin of the significant exchange bias is attributed to a novel ferromagnetic state as a consequence of the electronic orbital reconstruction at the interface. Our magneto-transport measurements have also demonstrated for the first time the reversible switch/control between two distinct exchange bias states by isothermally switching the FE polarization of BFO. This is an important step towards controlling magnetization with electric fields, which may enable a new class of electrically controllable spintronic devices and provide a new basis for producing electrically controllable spin polarized currents.
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Jan 7
Friday

Superconductive Nanowire Single Photon Detectors and Superconducting Nanorefrigerators

Speaker: Orlando Quaranta, National Enterprise for nanoScience and nanoTechnology (NEST)
XSD Presentation
431/C010 @ 11:00 AM
Jan 5
Wednesday

Incompressibility of the Quantum Mechanical Wavefunction

Speaker: Stephen Minter, University of California, Merced
XSD Presentation
431/C010 @ 11:00 AM