Positive and negative polarity current pulse characteristics of a helium glow discharge in a cylinder-plane electrode gap at atmospheric pressure

The positive and negative polarity discharge current pulse forms were examined between steel cylinder-Al2O3 plane electrodes in helium glow and pseudoglow discharges under atmospheric pressure at 10 kHz. The theoretically determined current pulses agreed very closely in form and magnitude with those recorded experimentally. The electronic and ionic charge carrier components comprising the negative polarity current pulse were found to be very nearly equal in magnitude, in contradistinction to the positive polarity pulse, where the electronic charge carrier component was dominant. This larger electronic charge carrier component was reflected in the magnitude of the corresponding photocurrent pulse, which substantially exceeded that of the negative polarity counterpart. The glow discharge regime current pulse forms were also compared to the pulse forms characterizing pseudoglow discharges, also obtained at 10 kHz but at a more elevated voltage, as well as with those recorded at a reduced frequency of 4 kHz but at the same value of applied voltage. Good agreement was also found to exist between the experimentally determined ultrahigh-speed image patterns of the propagating positive and negative discharges and the corresponding calculated electron density contours within the gap. (C) 2004 American Institute of Physics.