Investigation of an ECR plasma thruster and plasma beam interactions with a magnetic nozzle

The results of an experimental study of an electrodeless electric propulsion device using electron cyclotron resonance (ECR) heating for plasma production are presented. The effects of pressure, propellant flow rate, and microwave input power on the plasma properties were examined. In addition, the effect of a magnetic nozzle on a plasma beam were examined experimentally and computationally.; A laboratory ECR thruster was operated with argon propellant in a vacuum tank at pressures in the 10{dollar}sp{lcub}-5{rcub}{dollar} torr range using a 2.115 GHz microwave beam at power levels up to several kilowatts. Several movable plasma diagnostics were used to measure the spatial variation of various plasma properties in the plume of the thruster.; At low pressures, ion flux profiles exhibited depressed ion flux along the thruster axis. The ion kinetic energy was shown to be invariant with input microwave power. However, increased pressure causes the plasma energy to drop due to friction with background neutrals. Propulsion parameters were calculated from the ion flux and energy data. The results were affected by background gas entrainment. The plasma potential and electron temperature both decreased with increasing pressure in the tank but were invariant with changes in microwave power. Measurements of microwave power reflected from and transmitted through the ECR region indicate that inefficient absorption may contribute significantly to energy losses.; Plasma detachment from the magnetic nozzle was identified as a critical issue for ECR and other applied-field thrusters. A collisionless model was used to calculate the trajectories of plasma rings in a magnetic nozzle, and it was shown that the nozzle configuration can be manipulated to reduce beam divergence and increase the useful radius of the thruster.; An attempt was made to experimentally examine detachment using an ion thruster with masked grids in an applied magnetic nozzle. The trajectories of the plasma rings could then be measured to determine the effect of the magnetic field at various strengths. A radial electric field, possibly due to inhibited beam neutralization, developed in presence of the magnet nozzle that caused the annulus to spread and decrease in radius making detachment unobservable.