An Electron Trap for Studying Cross-Field Mobility in Hall Thrusters

An electron-trapping apparatus was constructed to study electron dynamics in the defining fields of a Hall-effect thruster. An electron plasma is confined using vacuum electric and magnetic fields in the absence of neutral-plasma effects and dielectric walls, which are present in a typical Hall thruster. Crossfield electron mobility was investigated in response to changes in magnetic and electric field strengths and background neutral density, and has been found to be much larger than what classical theory predicts. Experimental mobility is on the same order as Bohm mobility; however, the agreement with Bohm mobility is suspected to be coincidental, and the elevated mobility observed is thought to be due to static electric field asymmetries or external electrostatic perturbations, which can be correlated with electrostatic disturbances found in a Hall thruster.