Interaction mechanisms between Atomic Oxygen and materials: investigation on reflected beam

Abstract

Abstract Atomic Oxygen (AO) is the main component of the residual atmosphere present at low earth orbit. Multiple reflections can locally enhance or lower erosion rate in case of complex geometry. The need for precise estimate of hyperthermal AO flux is thus crucial at critical target embedded into realistic assembly. Industrial modeling tools (example Atomox module in ESABASE2 and SYSTEMA toolboxes) may account for multiple reflections with simplistic approach (ray-tracing) and a set of semi-empirical parameters. In this context, an original geometrical setup was designed in order to expose target surfaces with normal and tilted incidences and after one reflection on a set of materials of interest (black conductive thermal coatings, coverglass, surface treatment…). Candidate materials have been selected in view to compare numerical results and experimental ones. Results of two test campaigns highlight the effect of incidence angle on erosion rate (higher erosion with tilted beam) and provide an estimate of residual fluence after one reflection (in the 4-10 % range depending on material type). First computations with engineering codes have been successfully conducted, the erosion patterns being rather well described with some basic hypotheses on material parameters (absorption, specular/diffuse reflection) and taken into account the reflection on adjacent metallic surfaces.