Transient spark: a dc-driven repetitively pulsed discharge and its control by electric circuit parameters

The paper presents an analysis of electrical characteristics of streamer-to-spark transition discharge in air at atmospheric pressure named transient spark (TS). The TS is applicable for flue gas cleaning or bio-decontamination and has potential in plasma shielding, combustion and flow control applications. Despite the dc applied voltage, TS has a pulsed character with short (∼10-100 ns) high current (>1 A) pulses, with repetitive frequencies 1-20 kHz. Estimation of the temporal evolution of electron density shows that ne ∼ 1016 cm-3 at maximum and ∼1011 cm-3 on average are reached using relatively low power delivered to the plasma (0.2-3 W). Thanks to the high repetition frequency, ne between two current pulses does not fall below a critical value and therefore plasma exists during the whole time. A detailed analysis of the TS control by electrical circuit parameters is presented. With appropriate circuit components, the current pulse tail (>1 mA) can be extended and the electron density can be held above ∼1013 cm-3 for several tens of μs.