First implementation of absolute extreme ultraviolet (AXUV) diode-array-based analysis and macro-instability diagnostics on Wisconsin high-temperature superconducting axisymmetric mirror (WHAM).

Absolute extreme ultraviolet (AXUV) diode arrays are widely used in fusion experiments for time-resolved measurements of plasma radiation. We report the first implementation of an AXUV-based analysis framework on the Wisconsin high-temperature superconducting axisymmetric mirror. A single, precisely calibrated 20-channel AXUV assembly measures line-integrated plasma emission with ∼1cm of spatial accuracy across the mid-plane. The data were processed to obtain the plasma's statistical moments, yielding time-resolved measurements of the centroid displacement Φ(t) and effective radius R(t). From the joint covariance of these quantities, we define a macroscopic instability parameter χ(t) that quantifies large-scale plasma evolution directly from AXUV observables. The parameter χ serves as a compact indicator of macroscopic plasma activity, decreasing with increasing end-plate bias and exhibiting strong anti-correlation with diamagnetic flux during confinement transitions. These results demonstrate that a single AXUV array can provide real-time assessment of macroscopic plasma dynamics, constituting the first demonstration of such capability in a magnetic mirror plasma. Future extensions to multiple arrays will further enhance spatial coverage and enable full-mode tracking in axisymmetric mirror configurations and related fusion devices.