Impact of Propellant Species on Hall Effect Thruster Electrical Facility Effects

Abstract

The impact of propellant species on the role of the conductive vacuum chamber wall in the discharge circuit of the 200 W T-40 Hall effect thruster is experimentally investigated using xenon and krypton propellants at operating pressures of . Aluminum plates are placed adjacent to, but electrically isolated from, the facility walls downstream along thruster centerline and radially outward, centered on the exit plane. Data are acquired for four plate electrical configurations: 1) biased relative to ground with measurements of collected current, 2) grounded with measurements of currents to ground, 3) floating with measurements of floating voltages, and 4) connected with measurements of the current conducted between the plates. The 42% decrease in ion beam current associated with krypton operation resulted in a 58 and 19% decrease in the collected current to ground and floating voltage, respectively, of the axial plate; the 10% increase in divergence half-angle with krypton propellant yielded a change in sign for the collected current to ground and floating voltage of the radial plate. These findings suggest that changes to the ion current density profile cause concomitant changes to electrical coupling between the Hall effect thruster and test facility.