LaB6 Hollow Cathodes for Ion and Hall Thrusters

Deep space missions and satellite station-keeping applications continue to demand higher power ion thrusters and Hall thrusters capable of providing high thrust and longer life. Depending on the thruster size, the hollow cathodes may be required to produce discharge currents in the 10-100 A range with lifetimes in excess of 10 years. A lanthanum hexaboride (La B6) hollow cathode has been developed for space applications to increase the current capability from the cathode and ease the handling and gas purity requirements. This cathode uses a LaB6 insert in an all-graphite hollow cathode structure with an integral graphite keeper. Three different sizes of the LaB6 cathode have been successfully operated at discharge currents of up to 100 A to date. Although the LaB6 cathode insert operates at a higher temperature than the conventional BaO dispenser cathode, LaB6 offers the capability of long life and orders of magnitude less sensitivity to propellant impurities and air exposure than conventional dispenser cathodes.