Temporal evolution of nanosecond-pulse dielectric barrier discharges in open air

Pulsed dielectric barrier discharge is a promising method for producing low-temperature plasma. In our letter, we describe atmospheric-pressure plasma driven by repetitive nanosecond pulses. The temporal emission behaviour of the discharge is investigated by fast images with 2 ns exposure time. Each image is taken during one single pulse and is not overlapped with other images taken in subsequent pulses. The discharge at a 1 mm air gap is diffuse and homogeneous, but some constricted filaments are observed in the diffuse discharge at a 4 mm air gap. Discharge starts from the center and spreads outward from the discharge electrode with mean radial velocity of about 10 ⁴-10 ⁶ m/s.