The Effects of Intense Electron Cyclotron Heating on Fast Electrons and MHD in the WHAM Device

The Wisconsin HTS Axisymmetric Mirror (WHAM) is a high-field magnetic mirror under construction at UW-Madison. This device will use Electron Cyclotron Heating (ECH) for a variety of functions including breakdown, reducing fast ion slowing down, and achieving an electron temperature greater than 750 eV. ECH power of up to 500kW will be injected into the relatively small volume WHAM plasma, giving the highest ECH power density in any fusion plasma experiment to date. This is predicted to initially produce a small density, very high energy electron population as the plasma is breaking down. Signals of this population will be detectable for multiple ms after breakdown through the hard x-rays they produce. Once sufficient density builds up ECH will primarily heat the bulk electron population, allowing WHAM to achieve its goal electron temperature. An overview of the hardware behind the ECH system in WHAM will be presented including the 1 MW, 110 GHz gyrotron system, the waveguide run, and a rotatable launcher. The current state of modeling for ECH waves using the Genray ray tracing code will also be discussed, with emphasis on how ECH can create different Te profiles and what effect this can have on MHD stability in a vortex confined mirror plasma. Lastly, experimental results from the first WHAM run campaign will be shown, including successful ECH breakdown and the measurement of a hot electron population.