Hybrid-PIC Simulation of a Hall Thruster Plume on an Unstructured Grid with DSMC Collisions

Although several operational codes are available for the prediction of plume dynamics of Hall thrusters and their interactions with spacecraft surfaces, their coverage of the range of physical phenomena involved and their ability to model complex geometries and material combinations has tended to be fairly restricted. We have initiated the development of a more comprehensive suite of models intended to be used either on their own, or as modules in an overall architecture of the type recently initiated at the Air Force Research Laboratory (Fife, et al. [1]). As a first stage in this development, the simplified physics currently embodied in an existing plume code (D. Oh, 1997 [2]) has been implemented in a new unstructured tetrahedral grid designed to couple with the surface grids generated by the AFRL for realistic representation of a typical spacecraft. A detailed source model that includes separate distributions for single and double ions as well as different populations has been integrated. More refinements on sputtering and material deposition and a method for predicting plasma behavior in non-quasineutral regions are planned, but have not yet been incorporated. The code models Xenon ions, double ions and neutrals kinetically, whereas the electrons are modeled as a fluid continuum. Direct Simulation Monte Carlo (DSMC) techniques are used to simulate the important collisions between kinetically modeled particles. Preliminary results presented here are compared to laboratory measurements on the plume of a low-power thruster.