Dynamics of a high-density plasma in a magnetic field

The paper considers the dynamics of the plasma generated by the explosive-emission cells of the cathode spot of a vacuum arc in a magnetic field. It is shown that the expansion of the (high-density) plasma in a transverse magnetic field may cause asymmetry in the plasma density distribution at the cathode spot boundary. The asymmetry, in turn, increases the probability of the ignition of new explosive-emission cells in the region of a stronger magnetic field in the direction of B × I. The disturbed plasma density distribution estimated in the magnetohydrodynamic approximation is presented. In addition, the velocity of the 'retrograde' spot motion (ignition of new explosive-emission cells) in the stronger field region is estimated as a function of the external magnetic field strength. The velocity estimates (a few to tens of m s⁻¹ T⁻¹) are shown to agree with experimental data. (note)