Impact of the electron density and temperature gradient on drift-wave turbulence in the Large Plasma Device

In this paper we present an experimental study of edge turbulence in the Large Plasma Device at UCLA. We utilize a scan discharge power and prefill pressure (neutral density) to show experimentally that turbulent density fluctuations decrease with decreasing gradient, as predicted for resistive drift-wave (RDWT). As expected RDWT, observe cross-phase between potential is close 0. Moreover, addition electron temperature gradient leads reduction amplitude fluctuations, RDWT. However, counter theoretical expectations, find do not follow same trends changes either gradients or gradient. The disconnect connected parallel flows result differences pressure, i.e. neutral density. Further analysis fluctuation spectra reduces low frequency up $10 \,{\rm kHz}$ introduction unexpected ${\sim }{\rm \pi}$ shift density–potential }10\,{\rm , while maintaining typical lower frequencies. These experiments partly confirm existing knowledge on turbulence, but also introduce new observations indicate need dedicated nonlinear three-dimensional simulations include neutrals.