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.

Observation of arc modes in a magnetically rotating arc plasma generator

“…In comparison to the distorted arc, the diffuse arc has a larger and more stable plasma zone. The temperature, current density, and arc shape differ significantly among the three modes, which may be used to decrease electrode erosion and provide aerosol analysis, both of which have industrial applications.…”

“…A mechanism for the diffuse arc was proposed by Xia et al, in which arc was thought to be spatially dispersed by the convection produced by Lorentz force. According to others, the diffuse arc is governed by the diffuse cathode arc roots. The diffuse mechanism is similar to that of the magnet expanding arc at lower pressures .…”

“…The arc column that rotates around the electrode in a rigid shape is classified as the rigid mode, while the arc column that rotates around the electrode in a constantly changing shape is identified as the distorted mode . When the arc column evolves from a constricted column to a diffuse plasma cloud that occupies the chamber's entire cross section, the arc column is deemed to be operated in the diffuse mode …”

“…Their studies also indicate that the rigid arc has high‐speed rotation and low cathode erosion rates. Slinkman et al and Xia et al considered that the distorted arc may evolve into a diffuse mode with the increase in magnetic field and arc currents. In comparison to the distorted arc, the diffuse arc has a larger and more stable plasma zone.…”

Emission Intensity Enhancement of DC Arc Plasma Induced by External Oscillating Magnetic Field

“…They mostly describe the effect of magnetic field on free burning arc plasma. Analytically useful arc plasma with continuous aerosol supply subjected to the influence of the magnetic field has been described in few recent papers [1], [2], [3], [4].…”