Imaging Group (X-ray Science Division)
The X-ray Imaging Group provides full-field x-ray imaging techniques for studies of dynamical phenomena, with spatial resolution ranging from a few micrometers to tens of nanometers, and temporal resolution ranging from a millisecond to hundreds of picoseconds. The group currently operates two beamlines, 2-BM and 32-ID, at the APS. Beamline 2-BM is optimized for fast micro-tomography and radiography with both phase and absorption contrast. Beamline 32-ID provides various full field imaging techniques using both absorption and phase contrast, including High-Speed Imaging, Real Time Radiography, Transmission X-ray Microscopy and nano-CT, and X-ray Micro-tomography. The Imaging group is also responsible for the design and construction of two new beamlines part of the APS-Upgrade project: the High Energy tomography beamline and the Multiscale Full-Field Imaging beamline. The major research areas within the group are detailed below.
Nature 497, 374-377 (2013)
3D reconstruction of Cretocar luzzii holotype (coleopteran from New Jersey amber, approx. 80 million years old).9
2-BM X-ray Micro-tomography
There are several micro-tomography systems at 2-BM, each of them optimized to a specific performance, e.g., spatial resolution, temporal resolution, loading capacity etc. The beamline has different beam modes that correspond to different optimized operational conditions. The available energy range of 2-BM is 12-35 keV in monochromatic beam mode, 12-45 keV in pink beam mode, and more than 100 keV in white beam mode. The versatile configuration options make this beamline suitable for 3D characterizations in material science/engineering, geosciences, battery, biology, and physics, to name a few, in both statistic and dynamic manners.
Xianghui Xiao is the leading scientist of the fast tomography program pushing for application in diverse science fields, from material science/engineering, to biology, to physics etc. Xianghui Xiao is also one of leading scientists developing phase contrast imaging techniques at APS.
Carmen Soriano’s research focuses in the study of paleontological samples, including amber insects (below), other fossil invertebrates and vertebrates.
Left: Micro-CT reconstructions with 46 projections using direct Fourier method (Gridrec). Right: reconstructions obtained using Maximum Likelihood Expectation Maximization (MLEM) method.
Data Analysis and Image Processing Software
Analysis of tomographic datasets is becoming progressively more challenging due to the increasing data acquisition rates that new technologies in X-ray sources and detectors enable. At the Imaging Group we developed a collaborative framework, tomoPy for the analysis of synchrotron tomographic data. TomoPy is a Python/C++ based framework, open-source, platform and data format independent, has multiprocessing capability and it is used routinely to process data from the 2-BM microCT and the 32-ID nanoCT systems. TomoPy includes direct Fourier and nonlinear reconstruction methods for incomplete tomographic dataset. These methods are used when is required to reduce dose and/or increase scanning speeds.
Doga Gürsŏy is the lead scientist developing and integrating new scientific software tools in tomoPy.
Zone plates with 80 nm zone width
Zone plate with 20 nm zone width
Zone Plate Fabrication
The zone plate program aims to produce optics, which benefits current APS operation as well as the proposed APS-Upgrade project. The goal of the zone plate development program is to fabricate optics with higher focusing power and efficiency at hard X-ray energies. Zone plates are fabricated at the Center for Nanoscale Materials (CNM), while atomic layer deposition (ALD) is done in collaboration with Energy Systems Division. Zone plate stacking is being developed in parallel with fabrication development for higher efficiency zone plate systems. Zone plates have been fabricated with outer zone width ranging between 40 to 100 nm with aspect ratio (zone height over zone width) of at least 10. Zone plate stacking tests resulted in a stack of 5 zone plates with 19% focusing efficiency at 25 keV X-ray energy, and 3 stacked zone plates for 23.6% efficiency at 11.8 keV. The zone plate development activity is led by Michael Wojcik.
Nature Physics 4, 305 - 309 (2008)
32-ID-B High-Speed Imaging
The High-Speed Imaging (HSI) technique takes advantage of the time structure of the filling pattern in the storage ring achieving exposure times set by the natural width of the x-ray pulses (down to 150 ps) and frame rates set by bunch repetition frequency (up to 6.5 MHz). These make this instrument a unique research tool for studying transient phenomena in hard and soft condensed matter, in systems far from equilibrium, including materials under extreme conditions (stress, heat, etc), failure of materials on impact, and the self-propagating exothermic reactions in metallic multilayers.
Kamel Fezzaa has been leading the HSI program, developing the capability and establishing and collaborating with a broad user community.
Caption: Diffraction pattern from a NiTi sample in austenite phase, generated with six x-ray pulses
32-ID-B Ultrafast Diffraction
Ultrafast white-beam diffraction capability has been developed, serving as a complementary tool to the high-speed imaging technique. By integrating an intensifier with a multi-frame high-speed camera, high quality diffraction data can be recorded with MHz frame rates. The ultrafast diffraction instrument aims to provide users the unique capability to study the non-repeatable material behaviors by measuring the strain evolution and phase transformation occurring in a single dynamic event. It is particularly suitable for probing those ultrafast dynamics that cannot be captured by the conventional pump-probe techniques. An in-house developed software is distributed to users to aid the simulation and analysis of the white-beam diffraction patterns.
Tao Sun has been leading the ultrafast diffraction program, implementing the diffraction detection system and developing the analysis software.
Proc. Nat. Acad. Sci. 104, 13198-13203 (2007)
32-ID-C Real Time Radiography and Phase Contrast Imaging
The Imaging group provides micrometer-range spatial resolution imaging in absorption or phase contrast modes over an energy range of 10-35 keV with data acquisition rates from 1 Hz to 3 kHz with a monochromatic beam. The scientific community of this instrument covers a broad range of disciplines: biologists looking at small animal physiology, material scientists looking at real time crack development, anthropologists looking at tooth development.
Kamel Fezzaa and Tao Sun are responsible for operating and upgrading 32-ID-C, and supporting user experiments on mono-beam imaging and tomography while Xianghui Xiao is focusing on fast tomography applications requiring the highest speed provided by 32-ID.
JES, 157, B783-B792 (2010)
32-ID-C Transmission X-ray Microscopy
The Transmission X-ray Microscope (TXM) installed at 32-ID provides full field imaging with up to 25 nm spatial resolution in the 8-15 keV energy range. This instrument currently leads the world’s hard X-ray imaging facilities in resolution, throughput, and in situ imaging capabilities. Both absorption and Zernike phase contrast modes are implemented. The research programs led by Vincent De Andrade include instrumentation development to push the spatial resolution down to 15 nm. Implementation of multi-scale and multi-modality 3D imaging techniques like XRF tomography is also being implemented to enable a more comprehensive and practical characterization of samples in a same run. These developments benefit to the on-going TXM programs in earth and environment sciences, energy production and storage systems or still material sciences.