The bidirectional character of O2 concentration in pulsed dielectric barrier discharges in O2/N2 gas mixtures

This paper presents experimental results on the influence of O-2 on the characteristics of dielectric barrier discharges (DBDs) at one and at half atmospheric pressure. Gas mixtures of 0.1-10 vol % O-2 in N-2 were investigated, as well as in virtually pure N2. Electrical data, simultaneous streak and intensified charge-coupled device images were recorded in pulsed driven dielectric barrier discharges of 0.8 mm gap in a single filament arrangement. The O-2 concentration is shown to have a significant impact on the electrical characteristics, the temporal DBD development and its breakdown inception. Higher O-2 concentrations (above 0.1 vol %) led to an ignition delay, a shorter discharge duration, increased discharge radius, higher discharge current maxima and larger velocities of the cathode directed streamers. For O-2 concentrations below 0.01 vol %-i. e. nearly pure nitrogen-some of these effects were reversed. Moreover, the effects were more pronounced at a pressure of 0.5 bar compared to 1 bar. This result can be explained by the pressure dependent decay and recombination processes of positive nitrogen and oxygen ions.