Simulation of the Hydrogen Isotope Desorption in the Cathode Spot of a Vacuum Arc with a ZrDx Cathode

2D axisymmetric hydrodynamic model of convective diffusion of hydrogen isotopes has been developed to describe their desorption into cathode spot plasma of the vacuum arc with a ZrDx cathode. It was shown that limiting factor, which mainly determines deuterium desorption in hydrodynamic stage of functioning of cathode spot cell, is its transfer in the cathode from the volume to the surface. High gradient of hydrogen isotope concentration near the surface is maintained by pressing of almost desorbed surface layers of molten metal to crater peripheral area. Cathode volume, from which the gas is completely desorbed, is approximately equal to the volume of molten mass, pressed out upon formation of crater. Convective nature of deuterium desorption upon formation of microcrater results in the fact that the number of deuterium ions is by 4-6 times larger than the quantity of zirconium ions in CS plasma of vacuum arc with ZrD0.67 cathode.