Recent studies on nanosecond-timescale pressurized gas discharges

Abstract

The results of recent experimental and numerical studies of nanosecond high-voltage discharges in pressurized gases are reviewed. The discharges were ignited in a diode filled by different gases within a wide range of pressures by an applied pulsed voltage or by a laser pulse in the gas-filled charged resonant microwave cavity. Fast-framing imaging of light emission, optical emission spectroscopy, x-ray foil spectrometry and coherent anti-Stokes Raman scattering were used to study temporal and spatial evolution of the discharge plasma density and temperature, energy distribution function of runaway electrons and dynamics of the electric field in the plasma channel. The results obtained allow a deeper understanding of discharge dynamical properties in the nanosecond timescale, which is important for various applications of these types of discharges in pressurized gases.

Discharge Regimes Transition and Characteristics Evolution of Nanosecond Pulsed Dielectric Barrier Discharge

“…For this, the dynamic investigation of NPD was studied numerically and experimentally in the last two decades [15,16,17], and one of the most concerned issues is the discharge mechanism in rapid electric field. Several breakdown mechanisms were investigated in NPD, for instance, streamer, Townsend, and runaway electron modes [17,18,19,20,21,22,23,24,25,26]. Townsend breakdown often involves in a diffuse manner of the electrode gap [25].…”

Variable density formation by intense microwave beams near the critical density

“…In other words, for smaller values of negative 2 , the concentration of electrons is more. Moreover, for times much larger than , where = 1 ns [39] is the MW pulse duration, the modification of electron density is destroyed by recombination, collision, dissipation, etc. The physical interpretation of this behaviour is as follows: As mentioned above, by increasing the MW intensity, the relativistic ponderomotive force exerted on the electrons becomes stronger, which leads to a decrease in the width of the peaks.…”

“…Considering P < 1 MW, [37] MW intensity I = 5 × 10 6 W/cm 2 , and the MW frequency = 10 GHz, [38] one can neglect the relativistic self-focusing and modulation instability in the weakly relativistic regime and the model would be valid. Moreover, for times much larger than , where = 1 ns [39] is the MW pulse duration, the modification of electron density is destroyed by recombination, collision, dissipation, etc.…”

Emission Features and Structure of an Electron Beam versus Gas Pressure and Magnetic Field in a Cold-Cathode Coaxial Diode

“…In particular, at the limit of high gas pressure up to atmospheric pressure [35][36][37][38][39][40][41][42], the picture of electrons' origin changes dramatically. In this case, the gas itself becomes a supplier of fast runaway electrons (RAE) in the form of jets, which are tied to the centers of the field emission (FE) at the cathode [43] and have picosecond duration [44][45][46]. In the case of RAEs' emission, the energy lost by particles during impact ionization is much less than that acquired by them during acceleration in an electric field between inelastic collisions with molecules [35,36,38,47].…”