Incident angle dependence of reflected particles in low-energy xenon-ion impacts on metal surfaces

Ion-wall reflection characteristics are of great importance in the design of ground test facilities for electric propulsion because these characteristics determine the rarefied flow conditions inside the vacuum chambers. In this study, the reflection characteristics of 300 eV xenon incident on aluminum and titanium metal targets were calculated by molecular dynamics (MD) simulations. The resultant characteristics show the angular dependence of the reflected particles. The trajectories of the reflected particles show that the dominant reflection mechanism is different depending on the incident angle. A practical model that can be used to reproduce the calculated reflection characteristics is presented. Three parameters required for the model are obtained by fitting the model to the MD calculation results of the polar probability and energy distributions of the reflected xenon particles. The three-dimensional distributions reproduced by applying the three parameters to the model show good agreement with the MD simulation results.