Hybrid Monte Carlo -Particle-in-Cell Simulation of an Ion Thruster Plume

A numerical code is described that simulates the plumes of ion thrusters and Hall current thrusters. In the present study, computed e owe eld results are compared with existing experimental measurements for the UK-10 ion thruster. The experimental measurements consist of ion e ux, ion density, and e oating potential data. The numerical code combines the direct simulation Monte Carlo method for modeling collisions with the particle-incell method for modeling plasma dynamics. Xenon neutrals and ions are modeled directly. Electrons are described by the Boltzmann relation. The effect of a e nite back pressure experienced in laboratory experiments is included. Agreement between simulation and experiment issatisfactory. The simulation results are found to bevery sensitive to input conditions assumed at the thruster exit plane. In particular, there is uncertainty in specifying the effects of the curvature of the dished grids of the UK-10 thruster on the ion exit velocity proe le. The sensitivity of the simulations to certain model parameters is also examined. These include the cross section for charge-exchange reactions, the mechanics of charge-exchange reactions, and the electron temperature. The beam ions are found to be only moderately dependent on these variations, whereas the charge-exchange ions are sensitive to them.

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