Development of a fusion proton diagnostic for the Wisconsin High Temperature Superconductor (HTS) Axisymmetric Mirror (WHAM)

Sloshing ions produced via neutral beam injection (NBI) are essential for achieving plasma stability and high ion temperatures in mirror devices. In the Wisconsin High Temperature Superconductor (HTS) Axisymmetric Mirror, they are generated by a 1 MW NBI injected at 45° with respect to the magnetic axis. Fusion reactivity peaks near the sloshing ion turning points due to increased density, and its axially resolved measurement constrains the spatial distribution of the fast-ion population and magnetic equilibrium. We present modeling and hardware progress toward a scintillator-based fusion proton detector. A synthetic diagnostic has been developed to predict the absolute detector response for a given detector geometry, position, and ion distribution function. This capability enables direct integration of proton detector measurements into equilibrium reconstruction, providing a strong constraint on the fast-ion distribution. The scintillator-based design is compact, electromagnetic interference resistant, and tolerant to the high heat loads encountered during Ti gettering. These features allow operation in machine environments where conventional semiconductor detectors would fail. In addition, the detector geometry can be scaled with minimal cost increase, an important advantage for devices with low fusion yields.