Radial plasma flow in a hot anode vacuum arc

The free, steady state, two-dimensional radial plasma flow initiated betwee n a pair of disk-shaped electrodes of a hot anode vacuum arc was analyzed i n the hydrodynamic approximation. Studies include the influence of the self -magnetic field on the plasma density, velocity, radial spreading of the ar c current and potential distribution. The free plasma boundary was calculat ed by solving the equations for the normal and tangential velocity componen ts at the free boundary. It was found that the plasma significantly expands over a radial distance of about half of the interelectrode gap counted fro m the electrode edge and the plasma density in the center plane decreases b y factor of 2, whereas the density of the fringe current decreases by a fac tor of 10. The self magnetic field does not influence the plasma flow and c urrent spreading at radial distances larger than the interelectrode gap. Th e potential distribution is strongly nonsymmetric with respect to the centr al plane due to the influence of the plasma density gradients on the curren t spreading. (C) 1999 American Institute of Physics. [S0021-8979(99)01613-8 ].