CURRENT DISTRIBUTION AND THE MAGNETIC PRESSURE PROFILE IN A VACUUM ARC SUBJECT TO AN AXIAL MAGNETIC FIELD.

The steady-state electric current distribution and the magnetic pressure in a uniform conducting medium, flowing in a cylindrical configuration between two circular electrodes, was determined by solving the magnetic field transport equation with a superimposed axial magnetic field. This medium models the interelectrode plasma of the diffuse-mode metal vapor vacuum arc. The results show that: (a) the electric current and the flux of the poloidal magnetic field are constricted at the anode. Most of the constriction take place within a boundary layer, with characteristic length of the inverse of the magnetic Reynolds number of electron flow, near the anode; (b) the electric current constriction inversely depends on K theta , the dimensionless surface current density; (c) the magnetic pressure profile shows a radial pinch force in most of the interelectrode region, but in the anode boundary layer it is axially directed retarding the plasma flow; and (d) the peak of the magnetic pressure is at the anode and its amplitude directly depends on K theta . As K theta increases, the peak location moves toward the anode center.