High-voltage NS discharges interaction with blast waves*

Streamer propagation can be blocked both in the cases of low and high gas densities in the layer if its thickness is large enough. In the case of a thin high-density layer, streamers overlap the gap both for positive and negative polarities on the high-voltage electrode. For a relatively small layer thickness, the gap exhibits selective "conductivity": a negative discharge can develop up to a low-voltage electrode, while a positive discharge stops in a low density layer. Depending on the delay time between a laser pulse and a streamer, the streamer will demonstrate different behavior. At small delay times both positive and negative polarities will not be able to propagate through the conductive plasma layer. Both negative and positive streamers will be able to propagate through the hot nonconductive gas layer immediately after plasma recombination but before gasdynamic expansion. Finally, when the low-density layer will be formed, a streamer of positive polarity will not overcome this rarified gas layer, while a streamer of negative polarity will propagate further and finally will close the discharge gap.