Status and overview of the Wisconsin HTS Axisymmetric Mirror experiment*

The Wisconsin HTS Axisymmetric Mirror (WHAM) is a magnetic plasma confinement experiment developed by UW-Madison. The setup, with its 17-Tesla superconducting magnets and class-record volumetric density of heating power (3MW/40l) will explore the performance limits of simple axisymmetric mirrors by capitalizing on better understanding of MHD-stable operation of such systems and on the significant technological advances of recent years. The goals of the experiment include achieving the so-called classical mirror ion confinement regime that could be upscaled to Q ~ 1 fusion power gain factor in the upcoming next-generation device. A major part of the experimental program is devoted to plasma micro-stability, that was previously seen as a major obstacle to unlocking the full potential of simple mirrors. As a critical piece a larger fusion program, the experiment will also provide valuable data for advanced mirror concepts such as the axisymmetric tandem mirror reactor.

The report focuses on the design features and predicted performance of WHAM, including its magnet system, 1MW/25keV neutral beam and 0.9MW/110Ghz electron-cyclotron heating systems, as well as its sophisticated electrode structure that controls the shearing rate of plasma to minimize the MHD-related losses. The first plasma will be achieved in short pulses (10 – 20 ms), but the critical systems are essentially designed for long-pulse operation that can be attained after a few upgrades to the facility are made.