Characterization of streamers in water in a coaxial reactor

Streamer discharges in water are an environmentally friendly and effective method for the biological and chemical decontamination of water. We have studied the generation of streamers in distilled and in tap water with a coaxial reactor of 50 mm diameter and 100 mm length. Voltage pulses of up to 100 kV amplitude and 500 ns duration have been applied. Electrical and optical diagnostics were used to investigate the spatial and temporal development of the streamers. With a straight wire of 75 m in diameter as the center electrode, an average of 2-3 streamers per cm wire length was observed. By enclosing the wire in a perforated insulating tube, highly luminous plasma was generated in the chamber. The primary streamers spread along the outer surface of the tube, and served as a source of a multitude of secondary streamers. The high streamer density indicates a potential increase in bacterial and chemical decontamination efficiency over simple coaxial reactors. By introducing dielectric pellets into the discharge volume the plasma appears to spread relatively more homogeneously throughout the chamber. The spreading of the plasma, along with the adsorption and catalytic properties of the pellets has the potential to make the system more effective and efficient for water treatment application.