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Electrical breakdown in a pulsed asymmetric dielectric barrier discharge between a glass-covered mesh electrode and a grounded metal electrode in the air at atmospheric pressure is investigated. Volume discharge forms between the metal tip and the dielectric surface and spreads over the dielectric surface. Breakdown and discharge behaviors depend on the polarity of the charged electrode covered with glass compared to the metal rod electrode. In the case of the dielectric cathode (covered mesh), volume discharge features a stronger and longer-lasting emission. Volume discharge is weaker with outstretched surface discharge developing on the opposite glass electrode sustained by the embedded mesh when the metal rod functions as a cathode. The development and spatial distribution of the surface discharge depend on the relative polarity of the dielectrics caused by the charge deposition of the preceding discharge and is independent of the polarity of the applied high voltage. The discharge emission is brighter for the metal cathode and dielectric anode than for the metal anode, with a branching discharge developing and spreading in a star-like structure along the embedded grid, while a ring-like structure was observed for the metal anode and dielectric cathode. The duty cycle influences the discharge development and properties through the effects of the gas phase and surface pre-ionization.

The Ar( 3 P 2) metastable density in the effluent of the cold atmospheric pressure plasma jet kINPen was investigated as a function of the feed gas humidity, the gas curtain composition, and the distance from the nozzle by means of laser atomic absorption spectroscopy. The filamentary character of the plasma jet was considered as the absorption signals are from single individual events. From the effective lifetime, the quenching coefficient for Ar( 3 P 2) by water was determined. A maximum Ar( 3 P 2) density of ( 6.0 ± 0.7 ) × 10 13 cm − 3 was obtained close to the nozzle for a feed gas humidity of 20 ppm. The densities near the nozzle decreased inversely proportional to the water content in the feed gas leveling off at approximately 1 × 10 13 cm − 3, independently from the gas curtain composition. With the addition of water to the feed gas, the excitation dynamics changed, and the production and lifetime of Ar( 3 P 2) was reduced. The impact of Ar( 3 P 2) on the reactive species composition in the effluent was found to be smaller than within the plasma zone inside the plasma jet device.

A dielectric barrier discharge over distilled water was investigated by means of synchronized, fast electrical and optical diagnostics. For this purpose, a single, alumina-covered electrode was placed above a water surface and a grounded tungsten electrode underwater, while the gas gap was constantly flushed with synthetic air at atmospheric pressure. Discharge events occur at rising and falling slopes or at the plateaus of the applied high-voltage pulse. Due to the synchronized diagnostics, a direct comparison of electrical characteristics and optical features of individual discharge events was performed. In most cases, a single discharge channel develops between the tips of the dielectric and the Taylor cone. Surface discharge channels can also occur in the upper part of the electrodes, which can be explained by a water layer being formed on the dielectric and acting as a virtual electrode. The discharge morphology and dynamics were found to be independent of the voltage polarity, which contradicts to known experiments with bare metal pin electrodes instead of dielectric-covered ones.

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.