Study and optimization of 15-cm Kaufman thruster discharges

Abstract

Parametric and diagnostic studies of the Kaufman thruster discharge have shown that the transmission of the ion extraction optics and the magnetic field shape are the parameters that most significantly affect thruster performance. A high transmission ion optical system produces unexpected beneficial changes in the discharge plasma; over-all plasma density and electron temperature are lowered and the plasma potential distribution inhibits much of the ion loss to discharge chamber electrodes. A magnetic field configuration that distributes energetic electrons across the entire extraction screen produces a uniform plasma density distribution and thereby significantly improves thruster performance. Several different magnetic configurations have been found to provide such uniformity. In all cases the discharge losses are similar, typically 190 ev/ion at 85% propellant utilization in mercury discharges with hollow cathodes and with ion optics of about 70% transmission.