Hall thruster simulations in WarpX

Abstract

Two-dimensional (axial-azimuthal) simulations of a Hall thruster are performed using the open-source particle-in-cell code WarpX. The simulation conditions are chosen to match those of the LANDMARK axial-azimuthal benchmark reported by Charoy et. al. in 2019. Additionally, a range of numerical and solver parameters are investigated in order to find those which yield the best performance. By extending the code via its python interface, it is found that WarpX can simulate the benchmark case in 3.8 days on an Nvidia V100 hailing from the same era as the original benchmark, and just in 1.8 days on a more recent Nvidia H100 GPU. Of the numerical parameters investigated, it is determined that the field-solve tolerance and particle resampling thresholds have the largest effect on the simulation wall time, but that particle resampling may artificially widen electron velocity distribution functions, leading to unphysical heating. Using the results of the parameter investigation, an optimized simulation is then performed which completes the benchmark in just 36 hours on a single GPU. The results of this work are discussed in the context of advancements in GPU hardware and the suitability of kinetic Hall thruster simulations for engineering applications.