Gasdynamic diode formation with blast waves generated by fs-laser plasma

Streamer development is controlled by electric fields in which electrons are heated to ensure efficient electron impact ionization of neutral particles. In weakly-ionized gases and plasmas, electron impact ionization rate and other electron characteristics are determined by the reduced electric field E/N. Because of this, gas non-uniformities can influence streamer characteristics during discharge development under heterogeneous conditions. We demonstrated the use of a low energy, high peak intensity femtosecond laser pulse for guiding and control of a sub-microsecond high voltage discharges. Study of the early streamer formation and measurements of the field required for breakdown in air and nitrogen are presented. The streamer propagating along the Z-axis, depending on the delay time between the laser pulse and the high-voltage pulse will meet either a highly-ionized region of plasma; high-temperature, high-density neutral gas layer (immediately after plasma recombination but before gasdynamic expansion); or a combination of a high- and low-density gas layers. Depending on the delay time between a laser pulse and a streamer and a streamer’s polarity, the streamer demonstrates different behavior. It was shown that the blast wave – streamer interaction forms a “gasdynamic diode” with an asymmetric conductivity of the initially symmetrical air gap.