A review of spacecraft material sputtering by Hall thruster plumes

Abstract

Sputtering of spacecraft surfaces by energetic xenon ions in the plumes of Hall thrusters is a primary integration concern. The available literature is surveyed to identify useful sources of information for estimating these effects. In particular, the search considers relevant experimental measurements, analytical theory, and computer modeling. Sputter yields have been measured at normal incidence caused by xenon ions incident on many single-element materials. However, for more complex materials used on spacecraft such as silicon dioxide and Kapton, no direct yield measurements with xenon have been made. There are many theoretical models available for the estimation of xenon sputter yields of singleand multi-element surfaces, but these are generally only reliable after direct calibration against experimental measurements. There are a number of well-established, public-domain computer codes for simulating ion sputtering processes that are based on a Binary Collision Approximation (BCA) or a Molecular Dynamics (MD) approach. The BCA codes are more numerically efficient but less physically accurate than the MD methods. These computational methods appear to offer the potential to generate data-bases of sputter yields for complex materials as a function of impact energy and angle.