Engineering challenges and construction status of the Wisconsin HTS Axisymmetric Mirror (WHAM) *

The Wisconsin HTS Axisymmetric Mirror (WHAM) is in the middle stages of construction at UW-Madison. The backbone of the magnetic confinement scheme is a pair of record-setting REBCO mirror coils with anticipated 17 T field at the center of 5.5 cm warm bore.  Computer modelling optimizes these HTS coils spaced 1.96 meters apart.  With additional pulsed copper coils (from the decommissioned W7A stellarator), 0.3 to 0.9 T fields can be produced within the central cell.  At maximum field, the central cell vacuum vessel must react 35 tons of compressional force, with additional loading in off-normal events such as quenching of one superconducting coil.  This work highlights the engineering challenges involved in the machine design and construction, including additional ancillary systems such as pumping, neutral beam operation and pulsed power in a high magnetic field environment.  Design of auxiliary RF (26 MHz) and EC (110 GHz) heating systems are at final-review stage.  A large, repurposed vessel from the Los Alamos CTX device provides expansion volumes beyond the mirror throats, required for plasma stability and control systems.  Included is a report on the current status of construction, with several major components scheduled to arrive before November, 2021.