Recent Advances in Low-Current Hollow Cathodes at SITAEL

This paper presents the progress in the development of two hollow cathodes designed at SITAEL to be coupled with low-power Hall effect thrusters. The two cathodes are named HC1 and HC3, where the number indicates the nominal discharge current they were conceived for. HC1 features a barium-oxide tungsten impregnated emitter, capable of producing a current in the range 0.3-1 A. The most recent activities were focused on the development of a heater made in-house, which demonstrated the capability to sustain more than 5000 thermal cycles. HC1 showed a successful operation on xenon with HT100 (100 W Hall thruster), with floating keeper, proving the effectiveness of the design in sustaining low levels of current. HC3 features a lanthanum hexaboride emitter, capable of producing a current in the range 1-3 A. Following the progress made on HC1, a reliable heater was manufactured, which proved its capability to raise the emitter temperature to ignition values at low keeper voltages (<300 V). After the heater characterization, a thermal test was performed to obtain the thermal map of the cathode. The cathode was then ignited and characterized in stand-alone configuration on xenon; next, it was coupled with MSHT400, namely the magnetically shielded version of SITAEL’s 400 W Hall effect thruster, showing a successful operation on xenon. Future activities involving HC1 include the completion of qualification tests for the 100 W-power thruster unit, whereas HC3 will be tested with a barium-oxide tungsten impregnated emitter. In addition, a revisited version of HC3 will be developed, implementing modifications aimed at exploiting advanced manufacturing techniques, with the goal of reducing the cost still guaranteeing the reliability and mechanical robustness of the cathode design.