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September 28, 2021

Grad student focuses her energy on plasma physics

Written By: Staff

“For my research, I’m doing what I do because I want a carbon-free energy future,” says Carolyn Schaefer. “That’s why I got into it and the world really needs it right now.”

A fifth-year PhD student in engineering physics, Schaefer chose the University of Wisconsin-Madison for her graduate education because, she says, it’s the best for hands-on experimental work on a fusion experiment. “There’s a big fusion community and a ton of plasma classes,” she says. “I knew I wanted to be here. I visited for a few hours the week before I decided to come. I wanted experimental, and I wanted to be part of a group of grad students.”

She got both: Schaefer is among approximately 20 students and scientists working on Pegasus-III, a longstanding and internationally respected fusion experiment that’s currently undergoing a major U.S. Department of Energy-funded upgrade. “Not many people get to be part of a tokamak being put together,” she says. “You may be part of the operations, but not actually be part of the construction, so that’s pretty unique.”

Carolyn Schaefer
Carolyn Schaefer

Among other aspects, the upgrade centers around the team’s ability to test techniques it pioneered for actually starting the experiment and producing a plasma, which fuses atoms to make energy. Most tokamaks use a solenoid to start the plasma via magnetic induction; Pegasus-III will be a dedicated U.S. “proving ground” for studying innovative noninductive startup techniques.

Schaefer not only is helping with the experiment’s physical renovation, but in her research, she has been modeling the unique distribution of currents in the plasma, given the team’s noninductive method for starting the plasma. One aspect of the Pegasus-III upgrade is vastly improved diagnostics, which will enable her and others to develop improved models that see beyond just a moment in time and focus on how the plasma develops over time. That’s key, she says, because one of the team’s main startup techniques creates an atypical plasma with a main current stream as well as one at the plasma’s edge. “Understanding how this system evolves in time could answer many outstanding questions. The question I’m trying to answer is whether the main plasma is still OK,” she says. “Is the confinement still good despite the streams at the edge? We want to ultimately be able to stay we can use this advantageous technique and have a plasma that looks like that produced in traditional tokamaks.”

A native of Cold Spring, New York, Schaefer attended the Massachusetts Institute of Technology as an undergraduate, majoring in nuclear science and engineering with a minor in energy studies. Like many future engineers, she excelled at physics and math in high school and says she chose to pursue an engineering degree because it could open a variety of opportunities for her future.

During her undergraduate career at MIT, she also took advantage of several opportunities to conduct research, including work in MIT Plasma Science and Fusion Center and an internship in the DIII-D National Fusion Facility at General Atomics in San Diego, California. “I got more exposure being there and got to get into the field, learn and meet people,” she says.

Serendipitously, Schaefer’s primary advisor at UW-Madison, Engineering Physics Assistant Professor Stephanie Diem, got her start in fusion in the early 2000s as a UW-Madison nuclear engineering undergraduate working on Pegasus; in the early part of her professional career, Diem also spent two years on assignment at the DIII-D facility before joining the UW-Madison faculty in 2020.

Among only a handful of women working in the plasma physics field, both Diem and Schaefer are passionate about outreach and about broadening access to and participation in their discipline. So when they learned about an American Physical Society program called Women in Physics Group Grants, they applied for, and received, funding. The grants exist to support the society’s goal of recruiting and retaining undergraduate women in physics, and Schaefer used it to found Solis, a group designed to support and create community among women and gender minorities in plasma physics fields at UW-Madison. Its two dozen members span several departments across the university and include undergraduate and grad students, postdoctoral scholars, scientists and faculty, too. “We really wanted to make sure that everyone who is a gender minority in the field can take advantage of what the group can offer,” says Schaefer. “We do have allies who are regularly attending and I think they’re really helpful.”

While many of its activities, including group meetings and social and networking events, have been virtual, Schaefer’s aim is that the group’s members will meet regularly in person as pandemic guidelines allow. She’s also hoping they can engage students in middle or high school by conducting plasma demonstrations or sharing materials for experiments they can do themselves.

Earlier in 2021, Schaefer volunteered to be a fusion ambassador at a virtual event during which she participated in several meetings with members of the Wisconsin legislature. And though it was the first time she described her field to a general audience of adults, she says she enjoyed the opportunity to advance awareness of her discipline through outreach and plans to continue that work after she graduates in a couple of years. “It’s another way to contribute and it’s a way the field is going to move forward,” she says. “The world needs fusion energy, and the fusion energy field really needs women.”