MONTE-CARLO RE-DEPOSITION MODEL DURING TERRESTRIAL MEASUREMENTS OF ION THRUSTERS

For satellite missions, thrusters have to be qualified in large vacuum vessels to simulate the space environment. One caveat of these experiments is the possible modification of the beam properties due to the interaction of the energetic ions with the vessel walls. Impinging ions can produce sputtered impurities or secondary electrons from the wall. These can stream back into the acceleration channel of the thruster and produce co-deposited layers. Over a long operation time of thousands of hours, these layers can modify the optimized geometry and induce changes in the ion beam properties, e.g., broadening of the angular distribution and thrust reduction. A Monte Carlo code for simulating the interaction of ion thruster beams with vessel walls was developed to study these eects. Back-fluxes of a SPT-like ion thruster for two dierent test-setups and vessel geometries are calculated.