Performance of a 15-centimeter diameter, hollow-cathode Kaufman thrustor

Abstract

A mercury bombardment 15-centimeter diameter, permanent magnet Kaufman thrustor is planned for the SEaT I1 mission.The original thrustor design used a thermionic, oxide magazine cathode, but the advantages of a hollow cathode prompted its substitution.The changes in the thrustor were a redesign of the magnetic field shaping pole pieces and the propellant feed system.Additions to the thrustor were a baffle and a keeper electrode.Baffles of several designs were located on the thrustor axis downstream from the cathode.These baffles were found to significantly effect the propellant utilization efficiency and discharge chamber losses.The keeper electrode aided in starting and maintaining a stable cathode discharge.The effect of the magnitude of the neutral propellant flow through the hollow cathode was also investigated.The final thrustor configuration has been endurance tested for over 2000 hours at discharge losses of 250 ev/ion and a propellant utilization efficiency of 85 percent.The beam current was 0.25 ampere at a net accelerating voltage of +3000 volts.