Spatio-temporal filament behaviour in a dielectric barrier discharge plasma actuator

The behaviour of filaments in a dielectric barrier discharge plasma actuator in atmospheric air has been visualized through high-speed framing photography. A filament is recognized by its radiation emission in the positive, ascending phase of an applied ac voltage (1–5 kV, 1–5 kHz). A current pulse appears with a random time-interval typically of the order of 10 µs. A filament appears at a different location almost randomly in the span on the dielectric sheet, while the radiation distribution that is averaged over a couple of ac oscillation periods is quite uniform. With shortening of the framing interval, the lifetime of a single filament is found to be of the order of 10 ns.