Development of Superconducting Magnets for a Helicon Plasma Thruster

Abstract

The experimental results of an innovative approach to producing a uniform axial magnetic field for a helicon plasma are presented. Using a string of permanent magnets in concurrence with a high temperature type II superconductor, one can modify the structure of the magnetic field via the Meissner effect. Past studies have shown the capability of manipulating the magnetic field of a permanent magnet in this way to produce a uniform axial magnetic field. The previous configuration introduced a set of inherent challenges, which have been addressed and accounted for in the presented design. The current design consists of an annular quartz tube concentrically located within the confines of a superconducting tube. The annulus of the quartz tube houses the helicon plasma and the open axial region is reserved for a string of permanent magnets. The superconductor is cooled while the magnets are centered along the tube, causing any magnetic field lines contained within the superconducting material to lock in place while allowing those outside of the material to be manipulated. The magnets are then shifted upstream along the length of the tube, causing any magnetic field lines not locked into the superconducting material to stretch uniformly along the axis. It is shown that the resulting magnetic field geometry is suitable for helicon plasma generation.