Correlation between electric field, current and photon emission in subsequent barrier corona microdischarges

Abstract

We investigate single microdischarges (MDs) in a sinusoidally operated barrier corona discharge in air. For the voltage amplitude being applied, two subsequent MDs appear in the anodic pin half-cycle. The developments of these subsequent MDs were studied and presented in detail in a previous contribution [Jahanbakhsh et al., Plasma Sources Sci. Technol. 27, 115011 (2018)]. In the present study, the reduced electric field strength (E/n) values of the MDs are determined. In addition, the current pulses are synchronized, with a subnanosecond time resolution, to the spatiotemporally resolved light emission and E/n development of the MDs. It is proposed that the current pulse derivative maximum corresponds to the streamer head arrival on the cathode surface. Therefore, the derivatives of the current pulses are used to synchronize the light emission and current measurements. Based on this synchronization, spatiotemporally resolved light emissions at different positions are compared to the averaged current pulses. Considering the observed correlations, it is proposed that after the arrival of the streamer head on the dielectric (cathode) surface and bulk plasma formation, the ionization processes near the dielectric surface are the dominant source of electron current production. The determination of the E/n is based on the analysis of the time-correlated single photon counting results for the molecular states of the first negative and the second positive systems of nitrogen. The E/n increases during the streamer propagation in the gap, reaching its maximum value at the impact of the streamer on the cathode. The E/n values for the second group MDs are lower only in the vicinity of the dielectric surface, which can be attributed to the positive residual surface charges from the first group MDs.