Temporal and spatial emission behaviour of homogeneous dielectric barrier discharge driven by unipolar sub-microsecond square pulses

A homogeneous dielectric barrier discharge is generated by sub-microsecond square pulses. Two separate discharges per voltage pulse were observed, a primary discharge at the rising edge of the voltage pulse and a secondary discharge at the falling edge. Photos taken with a high-speed ICCD camera with an exposure time of 5 ns show that the evolution process of the first discharge (primary) is quite different from that of the second (secondary) discharge. The primary discharge starts from the bulk of the gap and the whole gap reaches its maximum emission intensity within 20 ns. Before the secondary discharge starts, there are weak emission layers next to both electrodes. The secondary discharge develops from the anode and expands towards the cathode, with the marked presence of a dark space adjacent to a weakly luminous cathode layer.