The pre-phase before the breakdown of pulsed dielectric barrier discharges (DBDs) is investigated. For this purpose fast optical and electrical measurements were performed on symmetrical DBDs with 1 mm gap in a gas mixture of 0.1 vol% O2 in N2 at atmospheric pressure.
A temporally limited diffuse emission previous to the breakdown of the subsequent discharge was observed near the anode. This isolated emission is correlated with a space charge which leads to a shift of the inception point of the cathode directed ionization front (positive streamer). The appearance of this emission in the pre-phase has significant consequences on the discharge properties such as the spatio-temporal structure of the discharge emission and on the duration and amplitude of the electrical discharge current.
The experimental results are compared with one-dimensional fluid simulations and indicate that the pre-ionisation and generation of electrons in the volume can be the main reasons.