Cathode spot motion in an oblique magnetic field

Abstract

Improper control of cathode spot (CS) motion can lead to uneven cathode erosion and shorter life, so magnetic fields are often used to direct CS motion. Here, we incorporate an axial magnetic field component into a model for CS retrograde motion based on the difference between the plasma kinetic and self-magnetic pressures. We consider the motion of the positive space charge associated with retrograde motion to generate a current perpendicular to the axial magnetic field, introducing an additional component to CS motion. The predicted angle of CS motion agrees well with the experimental data and a prior model based on electron backflow to the cathode surface.