Plume Measurement and Modeling Results for a Hollow Cathode Micro-Thruster

Behavior of the xenon dispenser hollow cathode is complex, exhibiting high ion emission and plume erosion rates, and unusual particle energy distributions. A flight-type hollow cathode was characterized with and without an external extraction electrode. Measurements involved a retarding potential analyzer, quadrupole mass spectrometer, and Langmuir probe. The far-field energy, flux, and charge state distributions of plume ions were studied as a function of cathode keeper current, flow rate, and viewing angle. The plume expansion was modeled by explicitly including both electrons and heavy particles in a combined Particle In Cell and direct simulation Monte Carlo approach. Initial comparisons between experimental and theoretical results have been made. The potential suitability of the device as an ion thruster is also discussed.