Turbulence Measurements of Steady State and Pulsed Power Plasmas on PHASMA

In this study, we investigate the wavenumber Power Spectral Density (PSD) of fluctuations in steady state helicon plasmas and during pulsed flux rope mergers in the Phase Space Mapping (PHASMA) experiment at West Virginia University. Optical measurements are obtained using a Photron Nova-S9 fast camera, while turbulence is characterized via floating potential measurements from a custom-built probe designed to suppress common-mode noise. Experiments are conducted in both argon and helium. Lateral imaging of plasma light emission reveals high-frequency (sub-300 kHz), temporally localized oscillations correlated with reconnection events, along with lower-frequency modes that may correspond to whistler waves. Previous measurements identified steep wavenumber spectra-up to k^-5.3 in both helicon plasmas (near ion cyclotron and electron skin depth scales) and flux rope mergers (near ion sound scales). To corroborate the non-perturbative optical measurements, a multi tip probe is used to extract radial, azimuthal, and lateral PSDs by correlating floating potential signals.