2025/12/17 by Shih, K., Endrizzi, D., Sutherland, D. A. +13
Physics and Astronomy · #Magnetic confinement fusion research #Solar and Space Plasma Dynamics #Laser-Plasma Interactions and Diagnostics
paper · doi:10.48550/arxiv.2512.15360
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 (HTS) Axisymmetric Mirror (WHAM). A single, precisely calibrated 20-channel AXUV assembly measures line-integrated plasma emission with 100~kHz temporal resolution and ∼1~cm spatial accuracy across the mid-plane. The data were processed to obtain plasma's statistical moments, yielding time-resolved measurement 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 motion and profile evolution directly from AXUV observables. The parameter χ serves as a compact indicator of global macroscopic instability, 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 quantitative, real-time assessment of macroscopic plasma instabilities, 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.