LAUSR

We have theoretically studied the molten metal jets formation during an operation of vacuum arc discharge for a wide range of crater sizes for near-threshold electric currents. At the initial stage of crater formation, a liquid-metal rim forms on the cathode surface under the action of the cathode spot plasma pressure. This process has been numerically simulated in the framework of the 2-D axisymmetric heat and mass transfer problem in the approximation of viscous incompressible liquid. At the next stage, jets form due to the loss of axial symmetry of the rim (the problem becomes essentially 3-D). The development of the Rayleigh–Plateau (RP) and Rayleigh–Taylor instabilities of the rim are analyzed in terms of dispersion relations for surface waves. It is shown that maximum increments correspond to the capillary instability of the RP type. The calculated time of rim formation and that of its breakup into jets have been demonstrated to be comparable. The analysis of rim perturbation spectrum has allowed to estimate probable number of liquid-metal jets.