Two dimensional simulations of Hall thrusters

Summary form only given. A two dimensional (2D) code has been developed in order to understand the complex dynamics of Hall Thruster discharges. It is based on Fife\´s hybrid particle in cell 2D code used in modeling SPT 100 thrusters. At issue is the effect of the plasma fluctuations on the electron conductivity. Indeed, experiments show that this conductivity is much larger than can the conductivity expected from classical particle collisions. While it is believed that fluctuations are a key factor in this enhanced electron transport, the mechanisms under which this transport is produced are not known with certainty. Previous simulations have used different "Bohm coefficients" to model the electron transport depending on the particular Hall thruster. However, these coefficients were constant in that they were independent of the local fluctuations. Experimentally, such coefficients have an axial dependence as one moves from the pre-ionization into the ionization and acceleration regions. We are presently implementing an axially varying electron mobility coefficient inferred from measured experimental data. In addition, we are characterizing the low frequency quasi-coherent modes present in these devices. These modes are likely not linked to the electron transport, but are nonetheless very important since they limit thruster performance. Results from our simulations will be presented.