Electrodynamic Mechanism of Expansion of Two-Component Plasma in a Spherically Symmetric Vacuum Gap

The results of theoretical modeling of spherically symmetric expansion of collisionless carbon plasma from a compact explosive emission center of a vacuum discharge are presented. The modeling is based on the joint solution of the Vlasov kinetic equations for electrons and ions and the Poisson equation for the electric field, written in the spherical coordinate system and averaged over angular variables. It is shown that the calculated cathode plasma expansion velocities are significantly lower in the spherically symmetric geometry than the expansion velocities of plasma with the same parameters obtained by solving the plane problem. The observed expansion velocities of the cathode plume plasma at the level of 3.5 × 10⁶ cm/s can be explained within the framework of the collisionless mechanism when the criterion imposed on the ratio of the electric emission current to the limiting electric current in the vacuum gap is fulfilled.