Schlieren Imaging of Shock-Wave Formation Induced by Ultrafast Heating of a Nanosecond Repetitively Pulsed Discharge in Air

We present schlieren images of the hydrodynamic expansion following a nanosecond repetitively pulsed discharge in atmospheric pressure air at room temperature. The discharge is created by voltage pulses of amplitude 7.5 kV, duration 10 ns, applied at a frequency of 1 kHz between two pin electrodes. The electrical energy of each pulse is of the order of 1 mJ. We recorded phase-locked schlieren images starting from a few nanoseconds after the discharge. The time-resolved images show the expansion of the heated gas channel from 50 ns and the shock-wave propagation starting at 0.5 μs.