Ignitor and keeper power supplies have been developed specifically for a Hall-effect thruster with a cold cathode. Prior to the development of these power supplies, difficulties had been observed in the operation of cold-cathode Hall thrusters; in particular, they did not start reliably upon turn-on of power. Many specialists in Hall thrusters had attributed the difficulties to the characteristics of cold cathodes as distinguished from those of hot cathodes.

The development of the present ignitor and keeper power supplies was guided by the observation that the key to reliable operation of cold-cathode Hall thrusters is to use correct power-supply waveforms and that the unreliability of startup observed previously was caused by the use of incorrect waveforms. The present power supplies comprise (1) an ignitor supply that produces a clean 1,000-V pulse with no undershoot and (2) a current-limited keeper supply. The combination of these power supplies produces a waveform that can be relied upon to start operation of a cold cathode on a stationary plasma thruster. The waveform produced by these power supplies can also be used to clean a cathode that has been contaminated by exposure to the environment.

This work was done by See-pok Wong, E. "Ned" J. Britt, and Raymond Lin of Space Power, Inc., for Glenn Research Center.

Inquiries concerning rights for the commercial use of this invention should be addressed to

NASA Glenn Research Center
Commercial Technology Office
Attn: Steve Fedor
Mail Stop 4—8
21000 Brookpark Road
Cleveland
Ohio 44135.

Refer to LEW-16490.