POSITIVE-STREAMER-LIKE PHENOMENA IN POINT-PLANE CORONA GAPS - TRICHEL PULSES AND HIGH-PRESSURE CATHODE SHEATH INSTABILITIES

Current pulse shapes have been measured in negative and positive corona discharges mostly in dry air. Negative corona Trichel pulses and pulses corresponding to the primary streamer/cathode contact in a positive point-plane gap were found to exhibit remarkable similarities, indicating a positive-streamer-like mechanism for the Trichel pulse development. High-frequency instabilities of the high-pressure filamentary glow discharge, which can be responsible for the arcing from freshly polished cathodes, were observed and attributed to local positive-streamer-like breakdowns of the cathode sheath.