Afterglow Tails and Stability of High-Density Nanosecond Arc Channels

Afterglow tails of high-density 10-nsec arc channels in 1-atm air have been analyzed to <10−3 of peak intensity value, exceeding 500-nsec duration, by employing a gated Kerr cell which protects the photodetector from saturation. Without such protection too high intensities exceeding a factor of 4 were observed. Low-intensity afterglow channels are photographed by superimposed multishot integration. This is possible because of the exceptional stability of such a particular plasma, which is demonstrated. Photoelectric and photographic decay functions agree. Spectral differences are observed and discussed.