Plasma flow crisis and the limiting electron temperature in a vacuum arc in axial magnetic field

The possibility of supersonic motion of cathode plasma in a low-current vacuum arc in an axial magnetic field has been studied. It is shown that an increase in the electron temperature unavoidably leads to a plasma flow crisis, whereby the plasma velocity decreases to the sound velocity. The dependence of the limiting length of a stationary flow on the magnetic field has been studied. The maximum possible electron temperature T-cr in the plasma is determined by the initial ion energy and can be estimated as T-cr approximate to 3T(m) , where T-m is the maximum electron temperature in the cathode spot region. (C) 2005 Pleiades Publishing, Inc.