Laser, Vacuum, and Gas Reaction Chamber for Operando Measurements at NSLS-II's 28-ID-2

Materials scientists often need to watch how a substance changes while it is being heated, mixed with gases, or subjected to pressure. This is difficult because traditional methods usually require stopping the process to take a measurement, or they can only see the very surface of a sample while the changes happen deep inside. To understand how materials behave in the real world, researchers need to observe them in action, a concept known as operando measurement. This approach allows scientists to track the speed of chemical reactions and the movement of atoms as they transform from one state to another, providing a dynamic picture rather than a static snapshot. Without this capability, it is hard to know exactly how fast a reaction happens or what intermediate steps occur before a material reaches its final form.

At the National Synchrotron Light Source II, a massive facility that generates intense beams of X-rays, a team of researchers has built a new tool to solve these problems. They designed a specialized reaction chamber that fits into a beamline called 28-ID-2, which is capable of firing high-energy X-rays through thick samples. This new device combines a powerful laser for heating with a controlled environment that can hold different gases or even a vacuum. The goal was to create a setup where a sample could be heated rapidly by a laser while being bathed in specific gases, all while high-speed X-rays took pictures of the atomic structure every single second. By doing this, the team could watch chemical reactions unfold in real time, capturing details that were previously invisible.

The chamber itself is a robust metal box designed to keep sensitive electronics and motors outside the hot, potentially corrosive environment inside. It features special windows that let the X-ray beam enter and exit, as well as a separate window for a laser beam to strike the sample from above. The researchers placed the sample on a mount that could be moved precisely, ensuring the laser and the X-ray beam hit the exact same spot. To measure the temperature without touching the sample, which could alter the results or melt a sensor, they used an optical pyrometer. This device acts like a thermometer that reads heat from a distance by detecting the infrared light the sample emits. The entire system allows the researchers to switch between different gas atmospheres, such as hydrogen or argon, or to pull a vacuum, all while heating the sample to temperatures as high as 1,500 degrees Celsius.

To test if this setup worked, the team first looked at iron oxide, a common material found in rust and used in various industrial processes. They pressed the iron oxide powder into small, solid pellets and placed them inside the chamber. They then introduced a mixture of hydrogen and argon gas and turned on the laser to heat the sample. As the laser heated the iron oxide, the X-ray beam passed through it, and the detector captured images of the atomic arrangement every second. The data showed that the iron oxide did not simply turn into iron in one smooth step. Instead, the researchers observed a complex sequence where the material changed through several different intermediate forms. Because they could measure the changes every second, they could see exactly how long each step took and how the different phases of the material coexisted during the reaction. This level of detail revealed that the process was far more complicated than previous studies, which often relied on slower heating methods, had suggested.

In a second experiment, the researchers turned their attention to a single crystal of a material called tungsten ditelluride. Unlike the iron oxide pellets, which were made of many tiny grains, this sample was a single, continuous piece of crystal. They placed it in a vacuum and used the laser to heat it up. The goal was to watch a specific change in the crystal's structure, where the atoms rearrange themselves from one pattern to another as the temperature rises. Because the X-ray beam was so powerful, it could pass through the thick crystal, allowing the researchers to see the atomic shifts happening deep inside the material. As the temperature increased, the diffraction pattern—the unique fingerprint of the crystal's structure—changed, confirming that the material was undergoing a phase transition. This experiment demonstrated that the new chamber could handle delicate single crystals and observe their internal changes without damaging them, something that is difficult with other heating methods.

The success of these experiments proves that the new reaction chamber is a versatile tool for studying materials under extreme conditions. By combining rapid laser heating with high-speed X-ray imaging, the researchers can now resolve chemical reactions that happen over the course of minutes with a time resolution of just one second. This capability opens the door to studying a wide range of processes, from how catalysts work in chemical factories to how minerals behave during high-temperature processing. The ability to see these changes as they happen, rather than just before and after, gives scientists a much clearer understanding of the rules that govern how materials transform. As the technology continues to improve, with plans to make the measurements even faster, this setup promises to reveal new insights into the dynamic behavior of matter in our world.