Electron Trajectory Simulation in Experimental Hall Thruster Fields

The correct approach to electron transport modeling in Hall thrusters is an open question in the field and is compounded by a lack of comparative studies on the relative influence of various proposed electron transport mechanisms in the thruster plume. Lacking an analytical model for transport, empirical coefficients are used in most models to reproduce major discharge parameters like the total discharge current and thrust, and these models are then used to gain insight into less observable quantities, especially lifetime-limiting discharge channel erosion. As part of an ongoing comparative investigation of electron transport mechanisms in the H6 6-kW Hall thruster, we examine drift and collisional electron transport in the near field between the centrally mounted cathode and the discharge channel exit plane using Monte Carlo-type electron trajectory simulations and focusing on binary plume collisions and thruster surface interactions. Experimental measurements of the time-averaged electric field and neutral density are used as model inputs. Approximately 104 electrons are seeded from a Maxwellian energy distribution and their trajectories are numerically integrated. Drift and collisional transport mechanisms in the static fields are found insufficient to explain any transport from the centrally mounted cathode to the discharge channel exit plane, as expected. This null result is presented to discuss the modeling technique of direct electron trajectory integration and to motivate its extension to timeresolved fields in the near future, taking into account turbulent transport mechanisms.