Radiation from a diffuse corona discharge in atmospheric-pressure air

Optical and X-radiation from a corona discharge in atmospheric-pressure air is investigated. Spectra of the optical radiation in the range 200–850 nm are obtained under various parameters of the voltage pulse. It was shown that an increase in the voltage pulse changes the corona discharge mode so that the discharge becomes a source of UV radiation, not only from nitrogen 2+ bands, but also from the cathode material. It was also shown that the formation of diffuse corona discharges in a non-uniform electric field under high pressure is conditioned by fast electrons and X-ray generation. It was determined that fast electrons originating from discharges in air under atmospheric pressure generate 525-eV photons from the K-shell of oxygen. Calculations have shown that the photons can effectively initiate new electrons near areas of strong fields. This process explains the formation of types of diffuse discharge for a positive-polarity electrode with a small radius of curvature at atmospheric pressure, and of a fast-moving cathode streamer.