High-Current Lanthanum Hexaboride Hollow Cathode for High-Power Hall Thrusters

Abstract

NASA is continuing to develop high-power Hall thrusters in the range of 20 to 100 kW for future cargo and manned missions. The cathodes for these thrusters will be required to produce discharge currents in the 50 to 300 A range with lifetimes in excess of 10 kh. A prototype high-current hollow cathode with a 2-cm-diam lanthanum hexaboride () insert was previously developed for these applications. The original design featured a graphite cathode tube to interface with the insert and an insulated sheath heater capable of heating the higher temperature emitter to ignition temperatures. A new version of this cathode has been designed and built that uses a refractory metal cathode tube and features a robust design similar to the small cathode used for the H6 Hall thruster. The new cathode has been successfully tested at steady-state discharge currents from 25 to 300 A. This cathode is intended to be used in an 80 kW nested Hall thruster being built at the University of Michigan at discharge currents of over 250 A.