Visualization of Streamer Channels and Shock Waves Generated by Positive Pulsed Corona Discharge Using Laser Schlieren Method

Streamer channels generated by a positive pulsed corona discharge are visualized using the laser schlieren method. The discharge occurs between a point-to-plane gap at atmospheric pressure with a pulse duration of less than 1 µs. In order to enhance the intensity of the schlieren image, water vapor is added to ambient gas. The schlieren visualizes heated gas in a streamer filament of 0.4 mm diameter. A temporal variation of the schlieren image after the discharge pulse shows that the heated gas moves outward from the streamer channel due to the diffusion. The diameter of the heated filament, in which the heated gas exists, increases from 0.4 mm to 1.1 mm within 1 ms following the discharge pulse. The schlieren image also shows shock waves generated by the discharge: a spherical shock wave generated at the tip of the point electrode and a plane shock wave generated at the surface of the plane electrode.