Observation of a narrow thermal channel connected to the anode during dark periods in long positive sparks

Abstract

Optical and thermal characteristics of discharge channels during dark periods are observed by a high-sensitivity experimental platform. A narrow thermal channel is found to act as a bridge to connect the residual discharge channel to the anode. Compared to the residual hot channel, the narrow thermal channel exhibits marked differences in thermal evolutions, maintaining temperature of about 800 K and thermal diameter of 0.8 mm. The narrow channel is expected to correspond to the weak luminosity with ionization activity on optical images, supporting the hypothesis that the reactivation of discharge channels in restrike originates from the channel tip.

Ultra-high temporal resolution images of a homogeneous electric field short air gap negative streamer at overvoltage and atmospheric pressure

“…In recent years, intensified CCDs (ICCDs) have been widely used in the shooting of streamers in long air gaps. [12][13][14][15][16][17][18] However, limited by the inter-frame delay, it is impossible for the ICCD to capture the complete evolution process of a short air gap single streamer which is usually in the order of tens of nanoseconds. Although multiple observation experiments can be summarized by photographing the images of different evolution periods of multiple streamers, 19) the dispersion and randomness of the streamer will have a certain impact on the accuracy of the results.…”