Comparison of molecular dynamics informed particle-in-cell carbon sputter simulations with ground facility experiments

Abstract

Accurate tracking of sputtered carbon species is crucial in assessing the lifetime of critical components in high-power electric propulsion systems. This study investigates carbon sputtering in high-power electric propulsion (EP) systems through comparison of numerical modeling and measurements obtained based on a new experimental technique that utilizes isotopic tracking. Sputter yield and differential yield models from molecular dynamics (MD) simulations were integrated into macroscopic particle-in-cell (PIC) plume simulations to predict carbon transport and deposition observed during the experiment. By coarse-graining the MD results from the atomistic length-scale to the meoscale PIC length scale, the study shows that the high-fidelity sputtering model captures the experimental trends. Comparison of experimentally measured carbon fluxes with predictions was found to be in agreement within a factor of two and with similar spatial distribution. Additional factors that might account for the difference between experiment and predictions, such as the roughness of the carbon target as well as the possible tilt relative to the ion beam axis, were considered. It was found that tilt effects lowered the discrepancy by up to 58%, depending on the probe location. Comparison of different sputter models revealed that the choice of angular and energy distributions significantly affects the results, emphasizing the need for accurate physics-based modeling. These results demonstrate the capability of the proposed numerical model to simulate carbon sputtering in EP testing facilities, providing a robust framework for future studies.