DIAGNOSTIC-TECHNIQUES FOR ATMOSPHERIC STREAMER DISCHARGES

Fast electrical and optical diagnostics are required for the analysis of atmospheric streamer discharges. This is illustrated for the case o f positive streamer corona produced along wire electrodes by high volt age pulses with rise times of tens of nanoseconds. Electrical measurem ents with a high time resolution reveal the energy input in two discha rge phases (primary and secondary streamer). The discharge structure i s visualised using a gated image intensifier. The number of streamers per unit length of anode wire and the streamer diameter are determined . The streamer velocity is measured with a time-of-flight method using two optical fibres. Time-resolved spectroscopic measurements of the i ntensity ratio of N2+ and N2 emission lines reveal that the average el ectron energy in the primary streamer phase is significantly higher th an in the subsequent secondary streamer. The neutral gas temperature i n the discharge is determined from the rotational structure of an N2 e mission line and is only slightly above the background gas temperature . Schlieren photographs visualise the heat dissipated in residual stre amer channels.