Tales from the Synchrotron

Posted: March 6, 2012 - 09:41 , by Kim Tait

I’m currently at the Argonne National Laboratory just outside of Chicago, Illinois at the Advanced Photon Source (APS). This is a research facility funded by the U.S. Department of Energy that over 3,500 scientists from all over the world comes to use the instruments here for their research each year.

Arial photo of the Advanced Photon Source at Argonne National Laboratory.

Aerial photo of the Advanced Photon Source at Argonne National Laboratory, Argonne, Illinois, USA. Credit: Argonne National Laboratory. Photo by John Hill, Tigerhill Studio, www.tigerhillstudio.com.

The APS is one of the most technologically complex machines in the world, and is known as a synchrotron. There is a large ring– the circumference is over 1 km that supplies photons to over 35 different stations or laboratories here each specializing in a specific type of research, such as geology, physics, chemistry, materials science, pharmaceutical, engineering, biology, to name a few! To get to do an experiment here you have to write a research proposal that outlines your experiment and why you can only use these instruments for your research. I’ve been very lucky to have had the opportunity to collect data here two dozen times and counting! Being a National Laboratory before the experiment must get clearance to visit, especially being a non-US citizen and complete the necessary training.

There is a nice guest house on the lab property right beside the synchrotron that you can stay at during your experiment time. When you are granted beamtime, you are given ‘shifts’ (a shift is 8 hours) and usually a few in a row. It’s best to come with a team of people, to share the time so you can get a bit of rest. I’ve done six shifts straight by myself and never want to do that again! This visit I am accompanying two researchers from the University of Nevada, Las Vegas Dr. Oliver Tschauner and Dr. Valentin Iota-Herbei. In this case it is their beamtime and they graciously allowed me to accompany them, as Dr. Tschauner and I are collaborating on a project.

When you arrive to the synchroton this is the first part of the building you see. To the left are the administrative offices and to the right is a meeting room. The synchrotron ring is behind these buildings.

The laboratory lite up against the night sky.

Advanced Photon Source. Credit: Argonne National Laboratory

We are working at HPCAT (High Pressure Collaborative Access Team) which is sector 16. You can walk everywhere but being a large ring it does take a while to get where you are going. Each sector has a dedicated tricycle when you need to get somewhere fast. Here is the tricycle where I am.

A yellow adult-sized tricycle parked inside.

For the type of experiment I want to do, a high pressure experiment, you need a diamond anvil cell (DAC). The idea is that you put your sample (just a small amount of material, about the size of a pin-head) between two diamonds and squeeze them together. Diamonds are the hardest natural materials on Earth, so they can withstand being forced together this way. The poor mineral in the middle is slowly squeezed and squeezed, forcing the atoms to compress which will eventually cause the atomic bonds to break and sometimes reform another mineral structure. Even if this doesn’t happen, we can observe the changes that happen to the minerals by exposing them to these high energy X-rays and learn about the properties of these minerals. Minerals that form on the surface of the Earth are subjected to little to no pressure, but the deeper and deeper into the Earth you go, the pressure (and temperature) increases. We can’t directly access these minerals to study them, so we simulate these conditions in the lab.

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