Stepped form of negative corona current pulses in hydrogen

Current wave forms of initial stages of discharge formation in a short nega tive point-to-plane gap have been measured with a nanosecond time resolutio n in hydrogen at pressures (12.5-76)kPa and for various overvoltages and ca thode point radii. The measurements revealed the existence of a stepped for m of negative corona current pulses in hydrogen. To test existing models fo r negative corona pulse formation, effects of changing cathode secondary el ectron emission were studied using copper and brass cathodes coated by CuI and graphite. It is concluded that a negative corona pulse is associated wi th the ignition of a cathode-directed streamer in the vicinity of the catho de. We report what we believe are the first experimental observations of no n-Trichel oscillations of negative corona current with a frequency of (1-10 ) MHz.