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

Inductively coupled plasmas (ICPs) generated by a radio-frequency (rf) power under a magnetic field have been vigorously investigated for industrial and space applications. In terms of plasma processing technologies, the uniform density profile is highly required. Moreover, the shape of the plasma density profile in the magnetic nozzle is expected to have a significant impact on the performance of a magnetic nozzle rf plasma thruster. Therefore, the control of the plasma density profile is highly desired for the fundamental studies and thruster development.

In this study, it is demonstrated that the radial density profile in the magnetic nozzle rf plasma thruster can be controlled by adjusting the rf powers to two rf antennas wound around the source tube. In addition, the thrust component corresponding to the Lorentz force onto the magnetic nozzle is solely measured to clarify the impact of the density profile on the imparted thrust. The results show the controllability of the density profile of the ICP in the magnetic nozzle and indicates the possible impact of the density profile on the thrust.