Physics considerations in design of the Wisconsin HTS Axisymmetric Mirror

A new magnetic mirror (WHAM) is under construction at UW-Madison with the primary mission of achieving MHD- and kinetically- stable plasmas in a low-collisionality regime, where the particle confinement increases rapidly with average ion energy. Several factors of the design benefit from expertise, experience and experimental data through collaboration with the GDT team at Budker Institute. The vessel diameter and pumping scheme (in both central and expander regions) are chosen to allow low-neutral pressure operation and minimize charge exchange losses of fast ions. Axisymmetric MHD stability is achieved via biasing end rings with respect to a central limiter (the vortex confinement scheme) and will allow modest plasmas in initial experiments, and electron temperature approaching 1 keV following the boost of the central magnetic field in the second experimental phase. Electrical and geometrical design of the electrodes follow development of similar systems in the GDT device. Scenarios have been developed for fast ion deposition via neutral beam injection and electron cyclotron resonant startup in the strong field device.