Characteristic study of a transient spark driven by a nanosecond pulse power in atmospheric nitrogen using a water cathode

Abstract

In this paper, a transient spark discharge is presented driven by a nanosecond pulse power with a needle-water electrode configuration in atmospheric nitrogen. The transient spark discharge concludes three phases, described as the streamer phase, the streamer-to-spark transition phase, and the spark phase. The amplitude of pulse voltage has a significant influence on the characteristics of the transient spark discharge. The streamer-to-spark transition time shortens with the increase of pulse voltage, and the spark current value increases with the increase of pulse voltage. Though the streamer-to-spark transition is not completely prevented, the gas temperature is still in a lower value (∼400 K), due to the short duration of spark current (200–400 ns). The electron density in the transient spark, calculated by the Stark broadening of the Hα line at 656 nm, is about 1.3 × 1017 cm−3, which is 2–3 orders of magnitude higher than that in other forms of gas-liquid discharge. The results indicate that the transient spark discharge plasma is in a highly non-equilibrium state and the results also present its other unique features of high electron density and abundant excited species.