Effect of density gradient and neutral density on drift-wave turbulence in LAPD

Magnetized plasmas with cross-field pressure gradients experience drift-wave turbulence. In magnetic confinement devices like the Large Plasma Device (LAPD), drift-wave turbulence is driven by electron density and temperature gradients, which directly affect cross-field particle and heat transport (Tynan et al. 2009, Carter et al. 2006). In previous experiments on LAPD, drift-wave density fluctuations increased with increasing density gradient, while introducing a small temperature gradient damped density fluctuations and reversed the cross-phase between density and potential fluctuations, altering the direction of particle flux. While changes in neutral pressure shifted parallel flow profiles and potential fluctuations (Perks et al. 2022). Experiments on LAPD were performed with a new LaB₆ cathode to access higher electron densities and temperatures. The cathode current and gas puff were altered to study higher density gradients and the impact of gas puffing versus pre-filling on turbulence and parallel flows. The electron temperature was measured using Langmuir probes, electron density and fluctuations using 4-tip probes, and parallel flow using Mach probes. Data analysis is ongoing, but from interferometer data, electron density increased non-linearly with cathode current.