Iodine Hollow Cathode

Plasma Controls, LLC will develop an iodine-compatible hollow cathode for use in Hall-effect thrusters. Materials in current state-of-the-art electron emitters, and many of the materials used in mounting hardware, are not compatible in a high-temperature iodine environment. This includes cathodes that use inserts made from porous tungsten impregnated with ceramics containing barium oxide, which can be susceptible to rapid decomposition of the ceramic by iodine, and lanthanum hexaboride-based inserts, which are subject to rapid surface decomposition by iodine. The work function of both types of inserts increases in the presence of iodine, and the temperature of the cathode increases, which further exacerbates the decomposition processes. We will use a materials science based approach to evaluate the chemical interactions between iodine and a range of potential materials at elevated temperature. We will construct and experimentally test candidate cathodes in relevant iodine environments to identify robust, safe-to-handle, chemically-stable material systems. In Phase II work, we will (1) perform long duration wear tests to demonstrate adequately long lifetime capability and (2) integrate the cathodes into iodine storage, feed, and thruster systems through industry and government partnerships.