First plasma experiments in the Wisconsin HTS Axisymmetric Mirror*

The Wisconsin HTS Axisymmetric Mirror (WHAM) is a magnetic plasma confinement experiment developed by UW-Madison and Realta Fusion. The setup, with its class-record volumetric density of heating power (up to 3MW/40l) will explore the 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.

The report briefly discusses the startup configuration of the device, as well as preparation of heating and diagnostic subsystems for the first campaign. We report our first experience installing and operating 17-Tesla superconducting magnets built by CFS.

In the first EC breakdown experiments we have produced a plasma with density sufficient for neutral beam injection and observed evidence of the high-energy electron tail. We also discuss the initial experiments with the NBI where we observed the buildup of the plasma pressure with expected features of a mirror discharge dominated by the fast ions. We characterize the confinement in the device, including the charge-exchange losses and axial ion fluxes. The report discusses the next campaign where we will focus on the MHD-stability of plasma and the near-term improvements we are planning to implement based on our initial experience.