Plume Measurement and Modeling Results for a Xenon Hollow Cathode

Behavior of the xenon dispenser hollow cathode is complex, exhibiting high through-anode ion emission, unusual particle energy distributions, and high plume erosion rates. The device may find new application as an ion micro-thruster. A flight-type hollow cathode was characterized using several diagnostic methods. 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 study of ion energy dependence on charge state is the first for a xenon hollow cathode. The results provide strong evidence in support of ion acceleration by a potential hill mechanism. 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. Reasonable comparisons were generally possible, but where broad ion energy distributions were measured they were not well matched by the simulations.