Radial plasma flow in a hot anode vacuum arc

The free, steady state, two-dimensional radial plasma flow initiated between a pair of disk-shaped electrodes of a hot anode vacuum arc was analyzed in the hydrodynamic approximation. Studies include the influence of the self-magnetic field on the plasma density, velocity, radial spreading of the arc current and potential distribution. The free plasma boundary was calculated by solving the equations for the normal and tangential velocity components at the free boundary. It was found that the plasma significantly expands over a radial distance of about half of the interelectrode gap counted from the electrode edge and the plasma density in the center plane decreases by factor of 2, whereas the density of the fringe current decreases by a factor of 10. The self magnetic field does not influence the plasma flow and current spreading at radial distances larger than the interelectrode gap. The potential distribution is strongly nonsymmetric with respect to the central plane due to the influence of the plasma density gradients on the current spreading.