Chapter 1

This chapter presents the results of experimental investigations of diffuse (volume) nanosecond elevated-pressure discharges in a non-uniform electric field at a time resolution of a recording system being equal to 100 ps. It is shown that conditions of obtaining a diffuse discharge without a source of additional ionization are extended at the voltage pulse duration reduction; specifically, a runaway electron preionized diffuse discharge (REP DD) was realized in atmospheric pressure air and other gases at a short interelectrode gap. It was found that the main energy deposition into the REP DD plasma occurred after attaining maximal voltage at a gap. At pulse repetition rate up to 1 kHz and elevated pressures the REP DD has been studied in nitrogen, air, and argon. In the conditions of generation of runaway electron beams and X-rays, a CCD camera recorded the time of the diffuse discharge formation and its duration prior to its transition to a spark one. In nitrogen, air, and argon the diffuse discharge was formed during the time not exceeding 1 ns. During the time not exceeding 1 ns the bright spots appear on cathode in argon and air resulting in the beginning of the spark channel propagation.