In-FEEP Ion Beam Neutralization with Thermionic and Field Emission Cathodes

Charge neutralization of an In-FEEP thruster was demonstrated with three different electron sources by zeroing the floating potential of the thruster and neutralizer system. The three cathodes used in the investigation include a mixed metal thermionic cathode, a carbon nanotube field emission cathode, and a Spindt-type Mo field emission array cathode. The field emission cathodes significantly improved the power to thrust ratio of the thruster and neutralizer system. At 10 µN, the power-to-thrust ratio of the ion and electron source FEEP system decreased by 50% when the Spindt-type cathode was used. Measured plasma potential were consistent with theoretical results obtained previously.