Mechanisms Controlling the Electric Field in the Channel of a Long Streamer

Numerical modeling of nanosecond pulsed discharges has been conducted in air containing different amount of water vapor. Gas pressure was 750, 375 and 225 Torr, plane-to-plane discharge gap was 90, 120 and 120 mm long, correspondingly. The water concentration varies from 0% (dry air) to 3%. The modeling was performed in 2D axisymmetric geometry using a drift-diffusion local field approximation [1] - [2] . The mechanisms [3] and role of plasma decay on the streamer’s properties were discussed. The analysis of the sensitivity of the parameters of the streamer channel to the main mechanisms controlling the development of the streamer discharge has been carried out. It is shown that the decay of the plasma in the channel significantly changes both the field in the channel and the length of the streamer path. Electron mobility has a greater influence on the field in the channel than plasma recombination. The greatest influence on the propagation distance is exerted by the gas ionization rate (through the streamer velocity). Photoionization has the weakest influence on the streamer channel parameters of all kinetic processes. It was found that the humidity increase from 0 to 3% increases the critical breakdown voltage by 20%.