Pulsed Discharge Induced by Nanosecond Pulsed Power in Atmospheric Air

Nonthermal plasmas have been widely used for various applications. Observation of a discharge plasma is an essential aspect for understanding the plasma physics of this growing field. In this paper, the propagation of a general pulsed discharge having a 100-ns pulse duration is observed by taking framing and streak images and spectroscopic measurement. The results showed that two discharge phases exist in the general pulsed discharge, namely, a streamer discharge and the following glowlike discharge. Between these two phases, the electrode gap impedance changed dramatically which could cause impedance mismatching between the power generator and the electrode. In addition, the gas temperature increased about 150 K during the glowlike discharge, which causes further energy loss in plasma-enhanced chemical reactions. Consequently, it was decided to remove the glowlike discharge phase and to only have the streamer discharge. A nanosecond pulsed power generator having a pulse duration of 5 ns was developed, and the observed discharge propagation ended before it shifts to the glowlike discharge. The streamer propagation velocity with the nanosecond pulsed discharge was 6.0-8.0 mm/ns, which is much faster than that of a general pulsed discharge, and showed little difference between positive and negative voltage polarities.