Numerical Simulation of Cathode Spot Motion in Magnetic Fields

Abstract

The present work deals with numerical simulation of cathode spot motion in self-consistent magnetic field under the 3D problem statement. Plasma jets are simulated with cylinders of a small fixed diameter, the conductivity of the latter can depend on the magnetic field. Electrodes are simulated in their actual 3D geometry. Magnitude and direction of the velocity of cathode spot motion as dependent on magnetic field components are taken from experimental data on motion of a single spot [1]. When accounting for the dependence of cathode jet conductivity on magnetic field, the conductivity is calculated on the basis of the data on single spot voltage from the same work. In this case, use can also be made of a mechanism of division of spots at the current exceeding some threshold and of their destruction at currents, lower than another threshold. Simulation has shown that the stable configuration at expansion of spot system is a ring in all cases, excepting the one of allowing for mechanisms of threshold division and destruction of spots. Time dependences of average spot system radius (relative to the electrode center) and standard deviation of the radius from the mean were obtained. In case of allowing for the mechanism of threshold division and destruction of spots, a ring is not a stable configuration any more, spots are distributed over an expanding circle in a roughly uniform manner.