Characterization of a Gas-Stabilized Arc Plasma in an ExB Magnetic Field Configuration

Abstract

A magnetic field of about 200 gauss oriented normal to the electric field in a 9 amp gas-stabilized dc arc is used to control the position of the plasma current channel. The presence of the magnetic field results in a drift motion of plasma electrons in the direction normal to the plane containing the electric and magnetic field vectors. The current channel can be displaced vertically upward or downward depending on the direction of the external magnetic field. With the field strengths used, displacements of several millimeters are observed. Spatially resolved radiation measurements show that radiation from the Ar plasma gas responds differently to the magnetic field than does radiation from the tungsten electrode material. When the magnetic field is generated by a 60-Hz ac current in the electromagnet, the plasma current channel undergoes periodic displacements at the magnetic field oscillation frequency. A phase shift between the field strength and the current channel displacement is observed.