Influence of parallel flows on drift wave turbulence in LAPD

In experiments at UCLA's Large Plasma Device (LAPD), we find a linear correlation between the amplitude of density fluctuations and the local density gradient, with no correlation observed between potential fluctuations and the local density gradient. In these experiments, the gas prefill and the cathode current were varied, allowing modification of the local density gradient at similar collisionalities and temperatures. Farther out, the introduction of an electron temperature gradient dampens the density fluctuations, destroying the correlation with the local density gradient, as predicted for a small ratio of electron temperature gradient to density gradient. Interestingly, a correlation between the potential fluctuations and the local density gradient is found, which was absent when no temperature gradient was present. We also observe a bifurcation in the potential fluctuations because of a difference in the parallel flow, which we plan to explore further in this poster. The parallel flow is linked to the parallel current, which is a critical component in driving resistive drift waves and we find that, with the differences in prefill and cathode current, this flow can change direction.