Numerical investigation of capillary discharge initiation by fast ionization waves.

The paper presents the results of a numerical investigation of a fast ionization wave in a non-preionized gas as the initial stage of a nanosecond capillary discharge. The wave was created in a 5 cm long narrow capillary filled with nitrogen at a pressure p = 2 Torr by applying a nanosecond voltage pulse of negative polarity, which was supplied by an electric circuit consisting of a preliminary charged capacitor, a thyratron switch and a cable. Propagation of the wavefront along the capillary and formation of a conducting plasma channel were simulated using the fluid approach to description of processes in low-temperature plasma. Including electrical circuit into consideration allowed obtaining realistic voltage pulse shapes as well as current rise-rates in the system immediately after the ionization wave has reached the grounded electrode. The latter was used as a parameter indicating the efficiency of the consequent initiation of a capillary discharge. Obtained dynamics of wave propagation and structure of the wavefront are discussed. Influence of dielectric permittivity of the capillary material on the wave properties in general and on the capillary discharge initiation is analyzed. • Numerical simulations of the initial stage of a fast capillary discharge created without preionization were carried out. • Fluid approach coupled with the equations describing the power circuit was used. • Estimates of current rise rate that takes place after the ionization wave has reached the grounded electrode were made. • A considerable dependence of simulation results on the dielectric permittivity of the capillary was observed. [ABSTRACT FROM AUTHOR]