FURTHER INVESTIGATIONS OF AN OPEN DRIFT HALL THRUSTER WITH BORON NITRIDE AND DIAMOND WALL

The operating characteristics of a linear-geometry (open electron drift) Hall thruster are revisited under cryogenically pumped vacuum conditions. A comparison is made between cases in which the thruster is operated with channel walls fabricated from plate diamond, and from boron nitride. These studies reveal a new operating regime/mode that exists at high magnetic field conditions that has never been reported for Hall thrusters, seen only when operating with diamond as the channel wall material. Operating regimes comparable to those seen in co-axial discharges are investigated using streak photography. The reason for this pulsed, low mean current regime is not yet understood but we conjecture that it is due to the difference between the secondary electron emission characteristics of boron nitride and diamond.