Measurement of plasma flow and electron energy probability function in radio frequency plasma thruster with a magnetic cusp

Abstract

The use of a cusp magnetic field is studied to improve the thrust performance of small electrodeless radio frequency (RF) plasma thrusters based on a theoretical analysis of a magnetized inductively coupled plasma. In this type of thruster, electrons play a critical role in determining the thrust performance. The electron energy probability function (EEPF) and two-dimensional profiles of the plasma parameters in the cusp-type magnetic field RF thruster are investigated to characterize the plasma flow. Non-Maxwellian EEPFs were obtained, which correspond to the pressure and plasma potential profiles in the plasma plume. In addition, the axial ion velocity was measured, and the presence of ion flux in the downstream direction is revealed, indicating ideal ion acceleration.

Thirty percent conversion efficiency from radiofrequency power to thrust energy in a magnetic nozzle plasma thruster

“…During the plasma expansion in the MN, an internal azimuthal plasma current spontaneously develops due to the diamagnetic nature; the axial Lorentz force arising from the diamagnetic current and the radial magnetic field increases the thrust, as predicted and demonstrated by theories and experiments [18][19][20][21] . The conversion efficiencies from the rf power to the thrust energy were about 0.5-5% in early experiments [22][23][24][25][26] and approaches about 20% in recent years 27 , based on the scientific insights into the thrust generation processes. Some models and experiments have identified that the energy and momentum losses to the source wall yield the low thruster efficiency and the inhibition of the loss by increasing the strength of the axial magnetic fields have been discussed and demonstrated so far 28,29 .…”