Production of large volume streamer discharges in atmospheric air using ultrashort electrical pulse

Summary form only given, as follows. High-energy electrons up to tens of eV can be produced in streamer discharges. These electrons collide with the molecules and change some of them into radical species. Ultra short and strong electric fields are capable of producing a large volume streamer discharge even in an atmospheric air. A large volume streamer discharge is produced by an ultrashort electrical pulse on the wire to plane electrodes. Time-integrated and -resolved observations of the discharge were performed using a still camera and a fast gated ICCD camera, respectively. The discharge chamber consists of a thin metal wire and two plain metal plates, which are placed at both side of the wire. The distance between the wire and plain electrodes is 8 cm each. A compact coaxial Blumlein generator (BLG), which has a length of I in and a diameter of 64 mm, provides the 10 ns square-shaped voltage into the electrodes. The BLG is charged up to 90 kV through a step-up transformer (2:5), which corresponds to the stored energy of 0.8 J. This system is operated with the repetition rate of up to 100 Hz, which is restricted by the recovery time of the pressurized gap switch of the BLG. From the time-integrated observation, the discharge volume is likely to be proportional not to the voltage but to the stored energy in the BLG. From the time-resolved observation the streamers are initiated near the wire and propagate to the radial direction. The propagation velocity of streamers is almost constant during the electrical pulse. The averaged velocity is tends to be proportional to the applied voltage between the electrodes.