Mechanism of ultra-fast heating in a non-equilibrium weakly ionized air discharge plasma in high electric fields

TLDR

The study analyzes shock‑wave observations in the afterglow of impulse high‑voltage nanosecond discharges to quantify electron power transferred into heat in air plasmas under high electric fields. A kinetic model was developed that incorporates known fast‑heating mechanisms at moderate reduced electric fields and additional processes relevant at high fields to describe the rapid transfer of electron energy into thermal energy. The results show that roughly half of the discharge power can be converted to heat for about 1 µs at atmospheric pressure when the reduced electric field is ~10³ Td, and the model’s predictions qualitatively match high‑voltage nanosecond discharge observations.

Abstract

Observations of a shock wave propagating through a decaying plasma in the afterglow of an impulse high-voltage nanosecond discharge and of a surface dielectric barrier discharge in the nanosecond range were analysed to determine the electron power transferred into heat in air plasmas in high electric fields. It was shown that approximately half of the discharge power can go to heat for a short (∼1 µs at atmospheric pressure) period of time when reduced electric fields are present at approximately 10 3 Td. A kinetic model was developed to describe the processes that contribute towards the fast transfer of electron energy into thermal energy under the conditions considered. This model takes into account previously suggested mechanisms to describe observations of fast heating in moderate (∼10 2 Td) reduced electric fields and also considers the processes that become important in the presence of high electric fields. Calculations based on the developed model agree qualitatively with analyses of high-voltage nanosecond discharge observations.