Effect of permanent magnets on plasma confinement and ion beam properties in a double layer helicon plasma source

Abstract

The work described in this article was carried out to investigate how permanent magnets (PM) affect the plasma confinement and ion beam properties in an inductively coupled plasma which expands from a helicon source. The cylindrical plasma device Njord has a 13 cm long and 20 cm wide stainless steel port connecting the source chamber and the diffusion chamber. The source chamber has an axial magnetic field produced by two coils, with magnetic field lines expanding into the diffusion chamber. Simulations have shown that the field lines leaving the edge of the source hit the port wall, causing a loss of electrons in this section. In the experiments performed in this work, PMs were added around the port walls near the exit of a plasma source and the effect was investigated experimentally by means of a retarding field energy analyser probe. The plasma potential, ion density and ion beam parameters were estimated, and the results with and without the PMs were compared. The results showed that the plasma density in the centre can in some cases be doubled, and the density at the edges of the plasma increased significantly with PMs in place. Although the plasma potential was slightly affected, and the beam velocity dropped by ${\sim}$ 10 %, the ion beam flux increased by a factor of 1.5.

Computational Analysis of Weakly Magnetized Plasma's Effects on Electromagnetic Wave Propagating Perpendicular to the Magnetic Field

“…Such devices are widely used in electric propulsion (Kaganovich et al, 2021). The application of a magnetic multipole cusp field around the port of a helicon plasma source significantly increases the downstream plasma density (Varberg & Fredriksen, 2019). Depending on the orientation of the magnetic field with respect to the propagation direction, the EM wave has several passes and stop bands in a magnetized plasma (Mandal et al, 2021).…”