Influence of a dielectric barrier on the stochastic behaviour of Trichel-pulse corona

The influence of a solid polytetrafluorethylene (PTFE) dielectric barrier on the stochastic behaviour of negative (Trichel) pulse corona discharges in air is examined. This behavior is revealed from measurement of conditional and unconditional corona pulse-amplitude and pulse-time--separation distributions. The results indicate that the presence of a dielectric surface on the anode effectively reduces the electric field at the point electrode, but does not affect the occurrence of Trichel pulses, provided the point-to-plane gap spacing is greater than a critical value d_c which depends on the area of the dielectric and the applied voltage. As the gap spacing approaches d_c, the effect of dielectric-surface charging by the corona introduces measurable memory effects indicated by correlations between pulse amplitude and time separation from the previous pulse. For spacings less than d_c, detachable corona-pulse activity is quenched by the presence of a quasi-permanent surface charge on the dielectric