Development of a Radioisotope Heated Hollow Cathode

Abstract

A new type of hollow cathode using a radioisotope heat source instead of a conventional sheathed heater was introduced and it achieved thermionic emission performances similar to the ones of conventional hollow cathodes. Strontium-90, Plutonium-238 and Curium-244 were chosen as radioisotope heat sources and a thermal reductive layer was also used to obtain precise thermionic emissions. A new system design methodology called the Self-Sufficiency Principle was introduced and was applied by powering the keeper electrode with the radioisotope decay heat using a radioisotope thermoelectric generator (RTG). The heater supply of the hollow cathode power configuration was replaced with a RTG supply and the mode of operation of the device was modified because radioisotope heat sources cannot be switched off. This hollow cathode was then benchmarked against two ion thruster configurations and a maximal overall power saving of 3% was achieved. Its advantages are its power saving capability and scalability but it can however be voluminous, heavy and potentially hazardous. Further research in this field ought to explore the range of applications of this new power-free electron emission technology.