A Calcium Aluminate Electride Hollow Cathode

This paper discusses the development and testing of a C12A7 electride hollow cathode. C12A7:e^- is a crystalline ceramic in which electrons clathrated in subnanometer sized cages act as a conductive medium. C12A7:e^- has a predicted work function of 0.6 eV and hence is of interest in electron emission devices. A 6-mm diameter hollow cathode was fabricated with a C12A7:e^- insert and operated for over 50 h on xenon with no signs of degradation. It was successfully started at room temperature without a heater and steady state operating temperatures below 650°C were observed during some tests. In addition, the C12A7:e^- cathode was operated on iodine for over 20 h at discharge currents up to 15 A.