Electrically Insulating Materials Testing in the Centrifugal Mirror Fusion Experiment (CMFX)

The centrifugal mirror confinement scheme incorporates supersonic rotation into a magnetic mirror device, which stabilizes and heats the plasma. This concept is under investigation in the Centrifugal Mirror Fusion Experiment (CMFX) at the University of Maryland. Plasma rotation is driven by an axial magnetic field and a radial electric field that lead to velocity drifts in the azimuthal direction. An electrically insulating material is required to prevent the applied voltage from shorting on the grounded chamber. Hexagonal boron nitride (hBN) is a promising candidate material for plasma-facing components in future centrifugal mirrors due to its exceptional thermal and electrical properties. However, its performance under intense particle and heat fluxes characteristic of the plasma edge in fusion devices remains largely unexplored. Computational modeling was carried out with RustBCA and predicts a relatively low sputtering rate and ion penetration depth compared to other plasma-facing materials. A load-locked sample feedthrough has been constructed and installed on CMFX to rapidly test coupons. We present a preliminary analysis of hBN samples exposed to supersonically rotating plasmas, and compare results with those of silicon carbide, another insulating plasma-facing material considered for future fusion devices. This researcher aims to enhance our understanding of electrically insulating materials in centrifugal mirror environments, informing future design choices.