Indium FEEP Thruster Beam Diagnostics, Analysis and Simulation

Space Propulsion Austrian Research Centers Seibersdorf, A-2444 Seibersdorf, Austria Indium FEEP thrusters based on space proven needle type liquid metal ion emitters are presently considered for a variety of missions which need ultraprecise drag-free capabilities such as LISA, SMART-2, GOCE or DIVA. One of the requirements of these missions is to investigate possible thrust vector variations, therefore the ion beam profile needs to be measured. A dedicated beam diagnostic assembly consisting of a wire and a Langmuir probe was installed in the laboratory to investigate single and multi-emitter configurations in the full thrust level of 1 – 100 µN per emitter. The derived thrust coefficient, thrust vector angle and beam divergence were within the expected limits. Multi-emitter configurations did not show any significant ion beam interaction. This analysis was supported by numerical simulations that could obtain similar results for emission in a pure vacuum environment without ambient electrons that can provide neutralization.