Atmospheric DC Glow Microplasmas Using Miniature Gas Flow and Electrolyte Cathode

We developed a new scheme to generate atmospheric dc glow discharges with a combination of an electrolyte cathode and a miniature gas flow. Stable glow discharges were obtained for a gap separation of 100-700 mu m with a cathode of a sodium sulfate solution. The gap voltage increased with increasing a current up to 15 mA, above which the voltage became constant as the low-pressure glow discharges. Local boiling by the discharge at the surface of the sodium sulfate solution began at 15 mA. At the same time, the emission of an intense sodium atomic line appeared in the negative glow region. The pH of the solution decreased when the discharge was generated in ambient air. The reduction of pH was attributed to the existence of nitrogen oxide, which dissolved in the solution. (C) 2009 The Japan Society of Applied Physics