Structure and Dynamics of a Magnetron DC Arc Plasma

Abstract

A direct-current arc plasma generator is described which uses a concentric electrode configuration and a magnetic field parallel to the electrode axis to obtain rotation of the arc current channel at a frequency in the 1–3 kHz range. The anode is a hollow graphite cylinder, and the cathode is a thoriated tungsten wire. A magnetic field of several hundred gauss is obtained from one or more ring-shaped permanent ceramic magnets. For a 5-mm anode diameter, the plasma is diffuse, and the current channel has the form of a thin radial sheet which undergoes relatively small periodic perturbations at the rotational frequency. Design features, performance data, and plasma structure are considered.