489 / 2022-03-17 09:08:31

Volume discharge driven by nanosecond pulses in a centimeter gap

gas discharge,electric field distribution,high voltage measurement,Simulation evaluation

With the development of nanosecond pulsed power technology, many efforts have been devoted to forming stable homogeneous form in high voltage discharge. With an enough high pre-ionization level, electron avalanches can overlap before the streamer formation. However, the temporal evolution of discharges during the ignition, propagation, and connection of the electrode gap with a scale of centimeters may be greatly different from the volume discharge, which is still not fully understood. The electrode system consists of a stainless-steel knife with length of 10 cm and thickness of 400 µm, and a copper plate with length of 12 cm and width of 2.5 cm, between which a gap of 1 cm is kept. An ICCD camera is used to capture discharge dynamics in the visible domain. The Electric Field Induced Second Harmonic (E-FISH) generation system is used to measure temporal evolutions of the electric field at different points within the gap. In addition, simulation is conducted by the 2D PASSKEy code.

The results show that the diffuse plasma sheet for the naked eye actually consists of multiple individual streamers by ICCD images, including the primary and secondary streamers. The primary streamers can penetrate the discharge gap and quickly extinguish after reaching the plate, while the secondary streamers only propagate about 3~4 mm away from the HV electrode. The entire discharge is in an intermediate state between corona and spark. Both current and discharge dynamics in experiment qualitatively agree with the calculated results. The appearance of two processes, namely primary and secondary streamers, is consistently verified by discharge images, electric field evolution, and fluid simulation. This further proves that the entire discharge belongs to an intermediate state between corona and spark.