NUMERICAL-SIMULATION OF STREAMER-CATHODE INTERACTION

A self-consistent fluid model has been used to analyze streamer arriva l at the cathode and its transformation to the stationary cathode fall in a positive point-to-plane corona discharge in Nz at 26.7 kPa. The model is based on a description of the electron and the ion kinetics b y one-dimensional continuity equations coupled with Poisson's equation . The ions and electrons are assumed to be Limited to a cylindrical ch annel with fixed radius and the field is computed using the method of disks. The computed current induced by the streamer-cathode interactio n with a small cathode probe is compared with that measured experiment ally, The cathode probe signal consists of an initial sharp current sp ike due to the displacement current followed, some 20 ns later, by a l ower current hump due to the ion arrival at the cathode. The current s ignal is relatively insensitive to changes in the secondary electron e mission coefficients. The results obtained indicate that the intense i onization and associated light flash experimentally observed near the cathode at the streamer arrival are not, as generally accepted, due to an intense electron emission but due to a sudden increase in the mult iplication factor and a release of electrostatic energy accumulated in the streamer channel-cathode system. (C) 1995 American Institute of P hysics.