Single AXUV Reconstruction and Stability Gauging for the First WHAM Plasma

Absolute Extreme Ultraviolet (AXUV) diodes are widely used in plasma experiments, particularly in fusion research. Here we present the first AXUV-based reconstruction results for the Wisconsin High-Temperature Superconducting Axisymmetric Mirror (WHAM) [1]. Using a well-calibrated single AXUV assembly, we are able to track WHAM plasma dynamics such as plasma position and size with a temporal resolution on the order of MHz and with a spatial accuracy of approximately 1 cm. By solving the non-linear tomographic relation on a polar coordinate grid [2], we reconstructed two-dimensional plasma images with a resolution up to the m=1 mode. In addition, we developed reliable plasma stability parameters derived from the zeroth and first moments of the AXUV measurements. These parameters provide a systematic gauge of plasma stability, denoted by χ, enabling us to track the stability of each individual shot and compare stability between different shots. The stability results derived from χ were compared with the flux loop data, showing good agreement. Furthermore, poloidal diagnostic resolution and phase tracking accuracy can be improved by adding additional AXUV assemblies to the machine, forming a poloidal diagnostic array.