Production of large volume nonthermal plasma in atmospheric air using ultra-short high voltage pulses

A large volume corona discharge was produced by 10 ns high voltage pulses applied to a wire to plane electrode. The discharge electrode consists of a thin stainless steel wire and two planar copper plates, which are placed 80 mm above and below the wire. A compact coaxial Blumlein generator (BLG) delivers the 10 ns square-shaped voltage into the electrodes. The BLG is charged up to 100 kV through a step-up transformer (1:5), which corresponds to the stored energy of 1.0 J. Appearance of the discharge associated with the wire electrode diameter, the applied voltage and its polarity was studied by means of time integrated observation. Experimental results indicate the discharge diameter is proportional to the voltage. Therefore, the discharge volume is proportional to the energy into the discharge, and the averaged velocity of the streamer is proportional to the voltage. The discharge diameter depends on the wire electrode diameter. For the wire diameter of more than 1 mm, larger volume of discharge emerged from thinner wire. For the wire diameter of less than 1 mm, however, discharge volume was nearly constant. The inhomogeneous microstructure on the electrode surface plays an important role to initiate the discharges.