Design and thermal analysis of the insert region heater of a lanthanum hexaboride hollow cathode

Several space electric propulsion devices, such as ion engines and Hall effect thrusters, use hollow cathodes as the electron sources for providing the necessary electrons for the ionization of the propellant and to neutralize the ion beam leaving the thruster. Most of the hollow cathodes used in space applications have used Barium-oxide impregnated Tungsten (BaO-W) inserts as the thermionic emission material due to its low work function. However, recent studies have shown the advantages of using Lanthanum-hexaboride (LaB₆) insert material as the thermionic emission source. However, due to its higher work function, the LaB₆ inserts have to be heated to a much higher temperature compared to the BaO-W inserts. In this paper, design and thermal analysis of the heater of a prototype hollow cathode with an LaB₆ insert as the thermionic emission material is presented. The built hollow cathode will be used as a neutralizer electron source for BURFIT-80, an 80 mm diameter laboratory RF ion thruster running on Xenon propellant.