Mechanics & Machinery

This rare earth insert for ion and Hall thrusters has longer life and resistance to poisoning.

A compact, high-current, hollow cathode utilizing a lanthanum hexaboride (LaB₆) thermionic electron emitter has been developed for use with high-power Hall thrusters and ion thrusters. LaB₆cathodes are being investigated due to their long life, high current capabilities, and less stringent xenon purity and handling requirements compared to conventional barium oxide (BaO) dispenser cathodes. The new cathode features a much smaller diameter than previously developed versions that permit it to be mounted on axis of a Hall thruster (“internally mounted”), as opposed to the conventional side-mount position external to the outer magnetic circuit (“externally mounted”). The cathode has also been reconfigured to be capable of surviving vibrational loads during launch and is designed to solve the significant heater and materials compatibility problems associated with the use of this emitter material. This has been accomplished in a compact design with the capability of high-emission current (10 to 60 A). The compact, high-current design has a keeper diameter that allows the cathode to be mounted on the centerline of a 6-kW Hall thruster, inside the iron core of the inner electromagnetic coil.