Low energy Xe+ sputter yields for alumina, Hiperco 50, and boron nitride

Mark W Crofton,Jason A Young

doi:10.1063/5.0067346

Abstract

Electric thruster materials are often subject to erosion during normal device operation. As a result of the ion sputtering process, surface properties can be affected or the underlying material may be exposed, possibly compromising performance and/or lifetime. It is therefore important to know both the energy and angle dependence of total sputter yield for relevant materials so that these effects can be predicted. In this study, we have obtained limited datasets on three materials with applications in electric propulsion development, thruster-spacecraft integration, and other technological areas—alumina, Hiperco 50, and HP boron nitride—in order to augment the material properties database. For each case, angular profiles were obtained at a single ion incidence energy, and energy dependence was explored at normal incidence. The datasets have been least squares fitted, and the results were interpreted.

Highlights

Electric propulsion devices based on ion emission for thrust generation can cause erosion and deposition that impact performance and lifetime, as well as integration issues for the spacecraft that use them
The measured alumina total sputter yield (TSY) energy dependence found by the present study is plotted in Fig. 6, together with measurement results from the literature
The largest sources of uncertainty are expected to be in the Xe+ fluence measurement and TSY variation with evolving surface condition, roughness in particular,5 and atmospheric absorption effects, which were very significant for boron nitride4,6 and relatively minor for alumina and Hiperco

Summary

Introduction

Electric propulsion devices based on ion emission for thrust generation can cause erosion and deposition that impact performance and lifetime, as well as integration issues for the spacecraft that use them. Metal and insulator atoms and ions produced via sputter erosion may find their way into the plume and deposit on spacecraft surfaces, modifying their properties. Due to the inherent divergence of the ion beam, there may be intercepted surfaces that undergo sputter erosion, modifying roughness, composition, and thickness. Erosion and deposition processes inside thrusters potentially modify the lifetime potential as well. Plume density and flux depend on the angle with respect to the thrust axis, thruster operating point, composition of components, and facility background pressure. Net mass deposition rates are a function of ion beam flux due to simultaneous removal of depositing species, and the ion beam flux varies sharply with the angle

Methods

Results

Discussion

Conclusion