Carbon Sputtering and Transport in a Ground Facility during Electric Propulsion Testing

Carbon contamination of an electric propulsion (EP) facility as a result of backsputtering is a well-known problem in EP testing. As EP systems progress towards higher power capabilities (∼100 kW), the need to decouple facility contamination effects from the on-orbit performance and wear characteristics increases. In order to realize high-fidelity tracking of sputtered carbon in a ground facility, the combination of physics-based modeling and fundamental experiments is essential. This paper reports on results from three complementary activities to better understand and predict carbon sputtering and transport: (1) predicting sputter yield of graphite under low energy xenon bombardment by molecular dynamics simulations, (2) tracking sputtered carbon through the relevant facility and thruster plume environments using the Particle-In-Cell and Direct Simulation Monte Carlo method, and (3) developing a new carbon isotope tracking diagnostic to measure carbon transport in ground-based facilities.