Breakdown Phase of Pulsed N$_{2}$/He Atmospheric-pressure Micro-hollow Cathode Discharge Plasma

The breakdown phase of a pulsed N$_{2}$/He atmospheric-pressure micro-hollow cathode discharge plasma is studied by temporally resolved N$_{2}$ optical emission spectra as well as the waveforms of discharge current and voltage. The simultaneous measurements of N$_{2}$ emission and current in the pulsed plasma reveal the appearance of the current pulses which coincide with N$_{2}$ emission in the breakdown phase. N$_{2}$ emission intensity exhibits a sharp peak in the breakdown phase and becomes constant in the glow-discharge phase. Temporal variation of N$_{2}$ emission spectra indicates that N$_{2}$ rotational temperature remains below 500 K immediately after discharge ignition but rises promptly to 1000 K within 20 $\mu $s after the ignition. The average N$_{2}$ emission intensity during a current pulse in the breakdown phase is 3 orders of magnitude higher than that in the glow-discharge phase whereas the energy required for N$_{2}$ emission is lower by a factor of 60 during the current pulse than in the glow-discharge phase. Thus, in the breakdown phase, the plasma with high excitation and dissociation rates is likely to be generated efficiently even though neutral temperature remains low.