Effect of Preionization on the Erosion of the Discharge Channel Wall in a Hall Thruster Using a Kinetic Simulation

The two major problems with Hall thrusters are the sputtering erosion of the discharge channel wall and the low-frequency oscillation. A new design for a Hall thruster with an innovative buffer chamber, in which part of the propellant is ionized, shows effective ability to restrain the low-frequency oscillation. However, how the preionization affects the erosion of the channel wall has not been well studied. In this paper, a 2-D axisymmetric fully kinetic particle-in-cell and Monte Carlo collision model is developed to investigate the effect of preionization on erosion of the channel wall of a Hall thruster. The geometry of this simulation model corresponds to the typical SPT-70 thruster, and the computational domain includes the whole discharge chamber of the thruster and the near-field plume region. Some scaling laws are introduced to accelerate this simulation. A preionization model and an erosion model are imported into the simulation to investigate the effect of different preionization ratios on the erosion of the channel wall. The results indicate that the effect of preionization on the change in the electric field is not obvious, in that it does not change the energy of the sputter ions significantly. When the preionization ratio increases, the ion incidence angle decreases slightly, but the number of sputter ions increases markedly. Overall, the erosion of the channel wall increases with the increasing preionization ratio. It needs further consideration for the application of the buffer chamber that preionizes the discharge plasma.