Speaker: Dr. Stephanie Diem, University of Wisconsin
Title: The Current Awakens: Tacking the S&T Challenges of Non-Solenoidal Current Drive for Spherical and Advanced Tokamaks
Abstract: The potential to use fusion energy as a carbon-free, fuel-abundant energy source to meet the world’s growing energy demands has motivated significant public and private investments in US research. One research path to realize fusion energy involves tokamaks that magnetically confine hot plasmas in the shape of a torus. Almost every tokamak fusion energy machine in the world relies on magnetic induction from a central solenoid to drive the current necessary to create a fusion grade plasma. Minimizing or eliminating the need for a central solenoid in a tokamak would greatly simplify the construction and reduce the cost of these devices, increasing their viability for commercial energy production. There is a critical need to develop improved physics understanding of compact, spherical shaped tokamaks as well as the enabling technology to address the fully non-inductive current-drive and high transient heat load environment for these next-step devices. To support these efforts, the solenoid-free Pegasus-III Experiment at the University of Wisconsin-Madison is equipped with a leading innovative compact plasma injector technology, local helicity injection, an internal axially symmetric electrode-based plasma initiation technology, coaxial helicity injection, and a microwave heating and current drive system. While these technologies have historically been explored for plasma initiation and sustainment, alternative uses for the plasma injection technology are being explored as a tool to control off-normal events and provide stability for tokamaks and as an ion source for materials testing.
Bio: Stephanie Diem is an Assistant Professor of Nuclear Engineering and Engineering Physics at the University of Wisconsin-Madison. Prof. Diem is the Principal Investigator of the Pegasus-III experiment, a collaborative fusion energy experiment focused on developing enabling technology to reduce the cost and complexity of future magnetic confinement fusion energy machines supported by DOE Fusion Energy Sciences. She has also formed an interdisciplinary research team, the Fusion Impacts Collaborative, funded by the Wisconsin Alumni Research Foundation, that convenes experts across campus to research direct and indirect impacts of fusion energy, risk and safety of these systems, and develop strategies that build public understanding and trust.
Prof. Diem is a U.S. Science Envoy for the Department of State, the first chosen for fusion energy, and the Vice President of the University Fusion Association, a nonprofit organization focused on the development of plasma science and technology for the long-term development of fusion energy. She was a member of the New Voices in Science, Engineering, and Medicine of the National Academies, a recipient of the 2023 Fusion Power Associates’ David Rose Award for Excellence in Fusion Engineering and is a 2025 Kavli Fellow. Prof. Diem received BS degrees in Nuclear Engineering and Physics from the University of Wisconsin-Madison and a PhD in Astrophysical Sciences from Princeton University.