Characterization of High-Energy Nanosecond Single-Pulse Discharges in Pin-to-Pin Configuration

The characteristics of single-pulse pin-to-pin nanosecond discharges in open air were studied for high pulse energies (> 20mJ, ~10ns). Specifically, the discharge voltage and current were determined from the back current shunt probe, the temporal evolution of the spark in ns-increments was observed by ICCD camera, and vibrational N2 temperatures within the spark channel were evaluated via Coherent Anti-Stokes Raman Spectroscopy. It was found that the most energy (30.07 mJ) was deposited when the spark gap was 5 mm in length. Visual observation of the spark channel showed simultaneous development of cathode-directed and anode-directed streamers on a sub-ns timescale that expanded with time until a connection was formed between them, which then transitioned into a much brighter spark channel. Temperatures were observed to be in the 4000-6000 K range immediately after the discharge, which showed a decay on a time scale of ~500 ns.