Radial profile control of a magnetically expanding plasma and its impact on a plasma thruster

Abstract

Two RF loop antennas are wound around the source tube of an inductively coupled and magnetically expanding plasma. The magnetic field lines are convergent in the source and divergent downstream of the source tube. The RF antennas are independently powered by two RF generators, providing the change in the radial profile of the ion saturation current of a Langmuir probe. Peaks in the ion saturation currents are observed around the magnetic field lines intersecting the radial source wall at the RF antenna positions, implying the presence of the electrons created near the antennas and transported along the magnetic field lines. The results suggest that the radial profile of the magnetically expanding plasma can be controlled by superimposing the plasmas created by the two antennas. The impact of the radial profile on the thrust is preliminarily investigated by attaching only the solenoid to a pendulum thrust balance immersed in vacuum.