Electron density and temperature in a diffuse nanosecond pulse discharge in air at atmospheric pressure

Abstract

This work presents the first experimental results on the electron properties of a nanosecond diffuse fast ionization wave generated in synthetic dry air at atmospheric pressure under very strong overvoltage. Both density and mean temperature of electrons are investigated by Incoherent Thomson Scattering. The electron density is also derived from the Stark broadening of oxygen lines resolved by Optical Emission Spectroscopy. The extreme voltages applied question some common hypothesis of the diagnostics implemented. The solutions adopted and the remaining limitations are discussed in the paper. Each diagnostic covers a specific region of interest within the discharge and they show good agreement in conditions where they overlap. It is shown that most of the volume of the pin-to-plane discharge is quite representative of a quasi-steady state glow discharge dominated by the emission of the first and second positive systems of nitrogen. Once its propagation completed within the first two nanoseconds and until the end of the 10 ns pulse, it is characterized by rather homogen ous properties close to the axis. The electron density ise of the order of 1015 cm-3 and the mean temperature is about 3 eV within the whole air gap. About 6 ns after the start of the discharge from the pin, asub-millimetric region of strong ionization develops at the pin, which is consistent with the observation of a continuum of emission spreading from the UV to the near-IR spectral range. Within this part of the discharge, the electron density reaches values greater than 1017 cm-3 with an ionization degree higher than 1%. The radiative recombination of nitrogen ions N2 + and the three-body recombination of N+ with a large number of electrons could help to explain the continuum.

Investigation of the decomposition performances of Cu-EDTA using pulsed streamer discharge

“…A similar spectrum with a peak at 239 nm for an untreated Cu-EDTA solution was reported in Ref. 19 After 60 min of discharge, the intensity of the wide spectrum of Cu-EDTA between 250 and 340 nm decreased, and a new peak appeared between 200 and 230 nm. The reactive species emitted during discharge react with the surrounding air to produce RONS in the gas phase, which subsequently dissolves in the liquid.…”

“…The average electron density in a nanosecond pulse discharge in air is reported as approximately 10 15 cm −3 with a mean electron temperature of 4-5 eV at the point of discharge. 19) The electron density in the discharge streamers possesses an influence on the gas-phase reaction kinetics followed by the plasma-liquid interactions; however, the electron-ion densities are not estimated in this manuscript. The voltage waveform had a pulse width of 50 ns and a rise time of 20 ns.…”