Examining the contribution of electron-neutral collisions to turbulence in LAPD plasmas*

We examine the effects of neutral density and parallel flows on plasma turbulence using four-tip probe data measurements of plasmas at the Large Plasma Device (LAPD). Our focus is on the role of electron-neutral collisions in turbulent behavior. Turbulence in tokamak plasmas, primarily by drift-wave turbulence (DWT), allows for excessive heat transport from the plasma’s core to its edge (Goldston and Rutherford 1995). DWT, driven by density and temperature gradients, is prevalent in magnetically confined plasmas like those at LAPD and is often responsible for this cross-field energy transport, significantly impacting plasma performance (Carter et al. 2006, Tynan et al. 2009). By extrapolating electron density, temperature, and parallel flow data from the probe measurements, we aim to correlate DWT with other plasma parameters, such as electron-neutral collisionality. Previous work, involving measurements at only the center of LAPD plasmas, found that variations in neutral density can shift parallel flows, affecting DWT (Perks et al. 2022). Building on this work with measurements spanning the length of LAPD, we additionally seek to determine the causal relationship between DWT, neutral density fluctuations, and parallel flows. Improved understanding of these driving elements of turbulence is crucial to advancements in plasma confinement.