Rapid formation of electric field profiles in repetitively pulsed high-voltage high-pressure nanosecond discharges

Abstract

Rapid formation of electric field profiles has been observed directly for the first time in nanosecond narrow-gap parallel-plate discharges at near-atmospheric pressure. The plasmas examined here are of hydrogen, and the field measurement is based on coherent Raman scattering (CRS) by hydrogen molecules. Combined with the observation of spatio-temporal light emission profiles by a high speed camera, it has been found that the rapid formation of a high-voltage thin cathode sheath is accompanied by fast propagation of an ionization front from a region near the anode. Unlike well-known parallel-plate discharges at low pressure, the discharge formation process at high pressure is almost entirely driven by electron dynamics as ions and neutral species are nearly immobile during the rapid process.

Dynamics of Near-Atmospheric-Pressure Hydrogen Plasmas Driven by Pulsed High Voltages

“…It is set at 0 V between t = 0 ns and t = 5 ns, increases linearly with time from t = 5 ns, peaks at t = 10 ns, then decreases with time linearly, and vanishes at t = 15 ns. This voltage variation is similar to what has been observed experimentally [3]. The electrode-gap distance is 1.2 mm.…”

“…This propagation occurs before the applied voltage peaks at t = 10 ns and lasts for a duration of about 1 ns. The simulation results and experimental observations [3] are found to be in good agreement.The temporal evolution of the electron-energy probability function (EEPF) [7] near the cathode (averaged over the region of 0-0.3 mm away from the cathode) is shown in Fig. 2.…”

“…The electrode-gap distance is 1.2 mm. The neutral gas is assumed to be molecular hydrogen (H 2 ) at room temperature and have a pressure of 0.3 atm, following the experimental conditions in [3].A uniformly distributed plasma with a plasma density of 10 10 cm −3 at 300 K is assumed to exist at t = 0. It represents Manuscript a remnant of the previous pulsed discharge.…”

Ignition of a nanosecond-pulsed near atmospheric pressure discharge in a narrow gap

“…The main parameters determined directly are the discharge voltage, the current density, the electric field in the centre of the discharge, and the spatially and temporally resolved emission. First successful application of these diagnostics to a similar setup was reported in [1][2][3]. Here we go beyond by more detailed studies and in particular a careful analysis and interpretation of the data.…”

Kinetic simulation of a nanosecond-pulsed hydrogen microdischarge

“…[1][2][3] Despite the small size of these devices, state-ofthe-art diagnostics methods have been applied to reveal details of discharge operation. [4][5][6][7][8][9][10][11] In microdischarges excited by nanosecond pulses, transient electron dynamics takes place on a nano-or subnanosecond time scale. In combination with the small discharge dimensions, this makes numerical and experimental investigations particularly challenging.…”