RATE OF CURRENT-SPOT EXPANSION AT A GLOW-DISCHARGE CATHODE ON SUDDEN INCREASE IN VOLTAGE

Current-spot expansion at the cathode of a normal glow discharge on su dden increase in voltage is considered An analytical theory of expansi on as discharge propagation thanks to the diffusion of charges from th e edge of the current spot to the current-free zone is constructed. An analytical formula is obtained for the velocity of the spot boundary along the cathode as a function of the overvoltage, i. e., the differe nce between the actual and normal cathode potential drop. Numerical mo deling of nonsteady two-dimensional discharge expansion along the elec trode surface in a plane electrode gap is undertaken in the case of a sharp increase in voltage. The analytical theory of the rate of spot e xpansion gives data that are in satisfactory agreement with the result s of a numerical experiment and of experimental velocity measurement.