Triggering of DC positive corona by pulsed UV irradiation

Abstract

With a positive-point-plane gap having an anode radius of curvature of 0.5 mm at atmospheric pressure, when the voltage across the gap is gradually raised, a streamer corona is triggered by pulsed uv irradiation. In these conditions, two types of triggering are clearly found to exist. For non-electronegative gases, the streamer corona is triggered directly by photo-electrons released from the cathode and has a short delay time (type 1). Whereas for the electronegative gases such as O2 and SF6, it is triggered by electrons detached from negative ions arriving at the anode and has a long delay time (type 2). For air, the triggering of the streamer is type 1 for the gap-length range d < 10 mm and type 2 for d > 11 mm. The critical gap length at which the transition occurs from type 1 to type 2 depends on the anode radius.

Streamer breakdown: cathode spot formation, Trichel pulses and cathode-sheath instabilities

“…According to Gosho and Saeki [132], the discharge in electronegative gases is triggered by electrons detached from negative ions arriving to the high-field region near the anode. Subsequently, following a pre-corona sequence of avalanches [82], a positive streamer is initiated close to the anode.…”

The after-effect of streamers of positive corona under combined voltage

“…In air, the after-effect of a discharge on the rise and development of the next discharge is usually attributed to residual ions [4,5], chemical products (ozone, nitrous oxides, etc) [6,7] and neutral excited species [5]. Detachment of electrons from negative ions under the influence of the applied electric field is the dominant creation process of free electrons for triggering a corona discharge [4,5,[8][9][10][11][12][13]. The changes in rise probability of a discharge are caused mainly by the residual negative ions.…”