Efficacy of Electron Mobility Models in Hybrid-PIC Hall Thruster Simulations

Abstract

The cross-field electron mobility in Hall thrusters is known to be enhanced by wall collisionality and turbulent plasma fluctuations. Although progress has been made in understanding the plasma-wall interaction and instabilities responsible for the anomalous transport, a predictive model based on the underlying physics of these processes has yet to emerge. Hybrid-PIC simulations of the Hall thruster have typically depended on semi-empirical models of the mobility to provide sufficient electron current to match experimental results. These models are capable of qualitatively predicting the plasma response over a wide range of operating conditions, but have limited quantitative capabilities unless they are calibrated with experimental data. The efficacy of several electron mobility models in reproducing the plasma response of a 6 kW laboratory Hall thruster are assessed. With respect to a two-region mobility model that is frequently reported in the literature, a three-region model for the mobility is shown to significantly improve the agreement with experimentally measured profiles of the plasma potential and electron temperature.