Discharge development from positive point electrodes in air as influenced by a nearby dielectric surface

The interaction between discharges taking place in the stressed air volume of a point-to-point gap and the charge accumulating on a nearby dielectric surface due to these discharges is studied. In order to confine the discharge to one point electrode of the gap, the tip radius of that electrode was much smaller than that of the other electrode. Experiments were carried out with 250/2500 μs switching impulse or DC voltage applied to the point electrode in the presence of a dielectric plate from Plexiglas (PMMA). The breakdown probability was measured for different crest voltages of the applied impulse. The spatial distribution of the accumulated charge on the dielectric plate was measured. The repetition rate and charge content of onset-streamer pulses were measured in the presence of the dielectric plate with the point stressed by a positive DC voltage. All the measurements are discussed with respect to gas-discharge physics