Development and Iodine Testing of a Novel C12A7 Electride Planar Hollow Cathode

Iodine exhibits promising characteristics as a propellant for electric propulsion (EP) systems. Its performance is comparable to xenon, yet it offers significant cost advantages. Moreover, it can be stored in a compact solid state and easily fed into the system through sublimation. Thruster operation has already been successfully demonstrated for the iodine fed Advanced Cusp Field Thruster, Hall Effect Thrusters and Radiofrequency Ion Thrusters (RIT), with the first in-space demonstration for an iodine RIT in early 2021. However, an iodine-fed plasma-bridged hot neutraliser is required to unlock the full systemic potential of an iodine EP subsystem at higher current levels. There exists no high-current iodine-fed neutraliser so far, as the corrosive nature of iodine and the potential for emitter material poisoning pose challenges. In the framework of the “IcoN” activity, a planar hollow cathode based on a C12A7 electride emitter has been developed and tested. The emitter has been manufactured by Fraunhofer IKTS, the neutraliser was manufactured and tested at Airbus Friedrichshafen. The initial testing was done with krypton and changed to iodine, as soon as a reliable cathode performance was achieved. After the first iodine tests were completed, the feed system was updated with a proportional valve to allow better control of the flow rate. In the final test series, two different emitter types and two planar cathode configurations have been tested with iodine. The longest achieved stable discharge was 26 minutes. While it was possible to develop a fully functional iodine feed system and a novel heaterless planar cathode based on C12A7 electride for krypton, no long-time stable iodine discharge was achievable in the frame of the project.