As the Advanced Photon Source Upgrade nears completion, scientists anticipate the experimental possibilities

 BY CHRISTINA NUNEZ | OCTOBER 1, 2024

After a yearlong installation, light has returned to the world-leading Advanced Photon Source. Users across a gamut of disciplines, from materials to planetary science, are getting their research proposals ready.

In June, X-rays began to shine again at the U.S. Department of Energy’s (DOE) Advanced Photon Source (APS), a facility where intense, directed X-ray light beams are used to inspect everything from materials for better solar cellsand batteries to antibodies for fighting viruses. The return of light after a yearlong shutdown is one more momentous step in an upgrade that will create unparalleled research opportunities.

The process isn’t quite finished yet. The APS, a DOE Office of Science user facility at DOE’s Argonne National Laboratory, needs to continue building up to full power. It generates light through an electron storage ring, where charged particles — electrons — travel at high speed, releasing light beams where the track bends. Light from the ring will be funneled to 71 different experiment stations, or beamlines, some of which are now being brought online. When the $815 million upgrade is complete, the APS will be able to generate X-ray beams that are up to 500 times brighter than before, enabling scientists to inspect objects closely and in more detail.

Researchers are eager for that moment to arrive. More than 5,500 scientists in a typical year use the APS’s intense X-ray beams. In the leadup to the upgrade, Argonne staff have held workshops and conversations with APS users about what features they need for their scientific goals. Now researchers are submitting proposals to be among the first to use the new, world-leading facility.

“Everything that was happening before will continue on a new level. We will be able to do experiments much faster and probe materials properties at much higher pressures and temperatures.”— Vitali Prakapenka, GSECARS beamline scientist

Going the distance

Along with enhancements to existing beamlines, the upgrade involves seven new beamlinesoptimized to take full advantage of the brighter X-ray beams, plus essential infrastructure for the future completion of two more.

More than 70 research proposals have been submitted for these new stations. Two of the new beamlines, the High-Energy X-ray Microscope (HEXM) and the In-Situ Nanoprobe (ISN), will live in the new Long Beamline Building. ISN will allow one to more precisely observe materials at previously unattainable scales, for example materials for batteries, to see how they behave as conditions around them change.

At HEXM, users will use highly penetrating high-energy X-ray beams to study materials that need to withstand harsh conditions and long service times in uses like nuclear energy and aviation. The length of the beamline — 180 meters, rather than a more typical 80 meters — allows for both larger and smaller spot sizes than previously possible.

“Sample cross-sections were one millimeter before. Now they can be up to several millimeters, as the beam expands more over the long distance. This allows users to use bigger samples that are more representative of real-life conditions,” said Jonathan Almer, Argonne physicist. The beamline’s length also allows the beam to be focused below one micrometer — a thousandth of a millimeter — so researchers can zoom in with higher resolution to different areas of interest within a sample.

For Ashley Bucsek, who studies the mechanical behavior of metals, HEXM will offer the ability to combine established techniques with relatively new ones like dark-field X-ray microscopy, which can illuminate the very small-scale structure deep within a material. The technique collects repeated exposures of X-rays scattered off a sample with a lens between the sample and detector, combining the exposures into a high-resolution image of the sample.

“HEXM will be the only beamline worldwide to offer dark-field X-ray microscopy at high energies,” said Bucsek, who is an assistant professor of mechanical engineering at the University of Michigan. ​“This means we can use the technique to study larger samples and heavier elements than we can anywhere else.”

Metals and other hard materials are polycrystalline, which Bucsek likens to a handful of sand squeezed so hard that the grains fuse together. She observes the boundaries between those crystals to see how and when cracks form. X-ray studies can reveal information about tens of thousands of individual crystals. She wants to know about both the common and rare instances where faults in a material emerge.

“The worst-case scenarios may only happen in a couple of places, but they end up controlling how that material responds or fails,” she said. ​“HEXM is going to allow us to zoom into those really interesting regions, where we see these rare but potentially catastrophic events.”

Adjacent to HEXM, the new Activated Materials Laboratory will make it possible to safely handle nuclear materials and fuels. The lab, which is funded by DOE’s Office of Nuclear Energy, will make it easier and more efficient to conduct experiments with these types of materials.

At HEXM and at other upgraded beamlines, the goal for the first approved experiments will be ​“to bring in users who can really test the new capabilities and kick the tires pretty hard,” Almer said. ​“Then we’re going to open it up to general users.”

Newly possible measurements

Another new station at the upgraded APS, X-ray Photon Correlation Spectroscopy (XPCS), is optimized to explore samples of liquids, gels, glasses and quantum materials. The work done on this beamline will be important to developing battery chemistries, drug delivery systems and energy-efficient products, among other innovations.

By knowing a material’s atomic structure, one can often predict its properties. But that’s only a snapshot: Scientists want the full-length movie of what happens as the surroundings change.

“It’s very difficult to use structure alone to predict the viscosity or elasticity of a material if it’s not in a well-defined equilibrium state,” said Jeffrey Richards, assistant professor of chemical and biological engineering at Northwestern University. ​“The key to being able to do that prediction quantitatively is to be able to probe the dynamics. You need to know about how the particles can move in these nonequilibrium states.”

His everyday example of dynamics: ketchup that runs smoothly when squeezed out of a bottle but stops flowing when it hits your hamburger. Or, in the case of Richards’ research, the flow of suspensions used to manufacture thin films for battery electrodes. Understanding structure and dynamics enables engineering processes to improve these manufacturing steps.

XPCS will allow researchers to probe both structure and dynamics with the help of a rheometer, a device that can measure how fluid moves in response to different forces. This was possible to some extent before, but the upgraded APS X-ray beam will have increased brightness and coherence. Coherence is a measure of the light waves’ uniformity — think of the difference between the light coming from a flashlight (not coherent) versus a laser pointer (coherent).

The increased coherence means every photon in the beam is now useful for scientific observation, which means results will come faster and samples will be less likely to be damaged by lengthy exposure to X-ray beams. An experiment that would normally take days will reduce in some cases to a few hours with XPCS, Richards said, ​“It’s a game changer, not only in terms of the physical throughput for samples that were already suitable for these measurements, but also by making it possible to measure samples that could never have been measured before the upgrade.”

Simulating the Earth’s interior at GSECARS

While the new feature beamlines are exciting, for existing APS research areas, the upgrade will be no less transformative. The University of Chicago’s Center for Advanced Radiation Sources (CARS) manages seven beamlines, including four within GeoSoilEnviroCARS (GSECARS), which is designed for Earth and environmental science research.

Studies at GSECARS focus on understanding the planet’s deep interior by observing elements and compounds at extreme conditions, including temperatures up to 10,000 degrees Kelvin (17,540 degrees Fahrenheit). Scientists are exploring how dynamics deep below Earth’s surface contributed to the planet’s evolution and phenomena such as earthquakes and volcanoes. Seeing how different materials behave at extreme conditions has even broader relevance, including clues about the makeup of other planets and technologies such as room temperature superconductors.

“Everything that was happening before will continue on a new level,” said Vitali Prakapenka, GSECARS beamline scientist. ​“We will be able to do experiments much faster and probe materials properties at much higher pressures and temperatures.”

Prakapenka specializes in the use of diamond anvil cells to apply intense pressures to samples while they are in the beam. ​“The smaller the contact area, the higher the pressure we can reach,” he explained. The brighter light from the upgrade will make it possible to focus down to smaller sizes.”

Physicist Jungho Kim works on part of the 27-ID beamline at the APS. (Image by Argonne National Laboratory/Jason Creps.)

He compared the change to looking through binoculars at a bird. ​“Imagine you increase the magnification on the binoculars 100 times and have supersensitive eyes. Now you can see not only the form of the bird, but all the feathers and its structure, even while it is flying in the sky,” he said. ​“That’s a bit like what we are expecting after the APS Upgrade. Increasing the brightness and tightness of the X-ray beam will allow us to increase the resolution and sensitivity when we are looking at materials response to ultra-high pressures and temperatures.”

Almost ready for beam time

Installation of the new APS electron storage ring began last spring after more than a decade of planning. Considering the process involved 1,321 electromagnets, miles of cable, thousands of power supply units and hundreds of people, a year is practically no time at all. 

“It was so much coordination and collaboration, and the only way to pull it off is if you have people who are all on board with the same goal,” said Elmie Peoples-Evans, project manager for the upgrade. ​“The ultimate goal is to get the facility back up and running again and get our users back to doing science.”

Collaboration with users has been key to the process. ​“We really rely on the instrument scientists to drive some of this innovation,” Richards said. ​“The scientific community always wants better and faster experiments. I appreciate the APS team listening to the users and delivering on these new capabilities.”