Streamer evolution in a methane-based pulsed-dc discharge

Time-resolved spectrally-filtered CH/sup */ emission images of streamer development in a pulsed-direct current (dc) discharge in a methane/nitrogen mixture were recorded as a function of delay from breakdown. Single-shot images reveal one or two streamers while images averaged over 100 shots show up to eight. The intensity distribution along the inter-gap axis reflects the rise and fall of the discharge current. The intensity distribution parallel to the electrode surfaces reflects lateral discharge growth.