Method of Suppressing Ingestion Particles Flowing Back to a Hall Thruster using a Beam Target during Ground Testing

Neutral particles that flow back into a Hall thruster during ground tests are designated as ingestion particles. The source of the ingestion particles is apparently the chamber wall on which the ion beam is incident. As described herein, we propose a method of suppressing the ingestion particles using a beam target, designed to dump the beam, acting as a mirror to guide the reflected particles to the cryopump. Based on our earlier study involving the dependence of the pump capture coefficient of the cryopump on the angle of particle inflow and the surface reflection characteristics of metal targets for Xe ions, we present design guidelines for the distance between the Hall thruster and the beam target, the cone angle of the beam target, and the cryopump position. The ingestion particle suppression effect obtained by installing a conical beam target in an actual chamber was evaluated by applying 2D3V-DSMC calculations. For the 2-m-diameter, 3-m-long space chamber with 30-in-wide cryopumps set all around the chamber, the calculated ingestion mass flow rate to the thruster with a conical beam target is reduced to one-third of that with a flat target.