Discharge modes of atmospheric pressure DC plasma jets operated with air or nitrogen

The different discharge modes that were observed for a plasma jet operated at atmospheric pressure with air or nitrogen by applying a DC high voltage to a microhollow cathode geometry were investigated. Critical parameters that determine the operation in either a self-pulsing or 'true' DC discharge mode were identified based on an electrical circuit model and investigated accordingly. Current limitation by the overall circuit resistance supports either a continuous charging and discharging of stray capacities, together with associated repetitive plasma generation, or a short circuit operation. These different modes can be controlled by gas flow rate and applied high voltage. Consecutive plasma development in the self-pulsing mode resembles characteristics of a transient spark discharge. When the associated memory effects start to last longer than intervals between subsequent electrical breakdowns, eventually a current-limited self-sustained glow-like discharge is supported.