Iodine-Compatible C12A7 Electride Hollow Cathode

Iodine is highly attractive as an alternate electric propulsion propellant to xenon. It is easily stored in a compact volume on a spacecraft as a solid (greater than twice the storage density than pressurized xenon), which negates the need for a large pressurized tank. This, combined with its low cost and lower ionization energy, makes iodine an ideal propellant for a smallsat Hall thruster system. Currently, the heaterless C12A7 electride hollow cathode is the only low power electron source available to operate with an iodine electric propulsion thruster. C12A7 electride is a conductive ceramic with a measured work function of 0.76 eV. Busek proposes to mature the heaterless C12A7 electride hollow cathode technology to be conducive to low power applications and compatible with an iodine propellant. The proposed Phase I effort will focus on the design and fabrication of a durable C12A7 electride insert that will be compatible with future efforts to produce a qualification model cathode. Potential insert designs will be evaluated based on their operation within a laboratory model cathode body. The designed insert will be incorporated into an iodine-resistant cathode barrel and keeper and the full cathode will be characterized and delivered to NASA.