In atmospheric-pressure air preheated to 1000 K, nanosecond repetitively pulsed (NRP) discharges are shown to generate three plasma discharge regimes. In addition to the well-known corona and spark regimes, there exists a glow-like regime that develops through an initial cathode-directed streamer, followed by a return wave of potential redistribution. The applied electric field is then switched off before the formation of the cathode fall, resulting in an 'imminent' glow discharge. Previously, this regime had been observed only at 2000 K in air at atmospheric pressure. Measurements of the plasma dynamics, current–voltage characteristics, gas temperature and plasma chemistry of the excited species N2(B), N2(C), , NO(A) and O(3p 5P) in the pulsed glow regime are presented. Using 10 ns pulses applied repetitively at 30 kHz, we find that this glow regime generates an estimated electron number density of 1013 cm−3, while consuming only 1–10 µJ per pulse and heating the gas by less than 200 K.

https://iopscience.iop.org/article/10.1088/0963-0252/19/6/065015/pdf

Nanosecond repetitively pulsed discharges in air at atmospheric pressure—the glow regime

Power semiconductor devices, such as insulated-gate bipolar transistors, metal-oxide-semiconductor field-effect transistors, and static-induction thyristors, are used in different kinds of pulsed power generators developed for different applications. In addition, the semiconductor opening switch is found to have very effective applications in pulsed power generation by inductive energy storage. Semiconductor switches have greatly extended the scales of pulsed power parameters, especially in repetition rate and lifetime. They have also enabled new areas of pulsed power applications, such as accelerators, flue-gas treatment, and gas lasers.

Compact solid-State switched pulsed power and its applications

This paper presents the results of experimental investigations on the generation of supershort avalanche electron beams (SAEB) at nanosecond discharges initiated in gas-filled diodes. In air, at a pressure of 1 atm with a sharply non-uniform electric field, an SAEB is generated from the inter-electrode gap at a solid angle exceeding 2π sr. Reduction of gap d between the cathode and the anode leads to a decrease in the current amplitude of the beam incident on the lateral walls of the gas-filled diode and in an increase in the pulse duration of the beam current both in the axial and radial directions. Pulses of the beam current initiated on the lateral surface of a tube cathode have been recorded. It is shown that to generate electrons with an ‘anomalous’ energy, cathodes with an increased radius of curvature should be used.

Generation of supershort avalanche electron beams and formation of diffuse discharges in different gases at high pressure

The properties of an electron beam (e-beam) formed in air under atmospheric pressure are reported. The nanosecond generators RADAN-303 (two devices) and RADAN-220, producing nanosecond voltage pulses with amplitude of up to 400 kV and subnanosecond rise time were used in the experiments. It was shown for the first time that the duration of e-beam current of gas diode behind the foil does not exceed 0.1 ns. The maximum amplitude of current of a supershort avalanche electron beam (SAEB) behind the foil was ∼400 A. The data on the influence of various parameters on e-beam current amplitude measured behind the foil were obtained. An electron beam with energy less than 60 keV and powerful X-ray radiation were formed in discharge gap simultaneously with SAEB.

Supershort electron beam from air filled diode at atmospheric pressure

The paper presents the results of experimental research on nanosecond high-pressure diffuse discharges in an inhomogeneous electric field with a time resolution of ~100?ps. It is shown that decreasing the voltage pulse duration enhances the feasibility of the diffuse discharge with no additional ionization. In particular, with a narrow interelectrode gap, a diffuse discharge in atmospheric pressure air with preionization by runaway electrons, called a runaway-electron-preionized (REP) diffuse discharge (DD), was realized. It is found that most of the energy is deposited to the REP DD plasma once the voltage across the gap reaches its maximum. It is demonstrated that the REP DD holds promise for producing high-power VUV pulses. The radiation power attained with xenon at a wavelength of ~172?nm is 8?MW. The treatment of an AlBe foil with an REP DD in atmospheric pressure air provides cleaning of its surface layer from carbon and penetration of oxygen atoms into the foil to a depth of 450?nm per 300 pulses.

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Runaway-electron-preionized diffuse discharge at atmospheric pressure and its application

It is shown that a volume discharge is formed in a nonuniform electric field for the short leading edge of a voltage pulse and nanosecond pulse duration without any additional preionisation source in various gases at pressures higher than atmospheric (6 atm in helium and 3 atm in nitrogen). Lasing at atomic transitions in Xe is obtained in an Ar—Xe mixture under a pressure of 1.2 atm for an active length of 1.5 cm. A record-high specific power input (more than 0.8 GW cm-3 under a pressure 1 atm in air) is realised in the volume discharge stage. The volume discharge is formed due to preionisation of the discharge gap by fast electrons accelerated due to amplification of the electric field in the cathode region and in the gap. In a nonuniform electric field, volume discharge is realised under a quasistationary voltage from 10 to 180 kV across the gap, at a pulse repetition rate of up to 160 Hz and for various discharge gap geometries.

https://iopscience.iop.org/article/10.1070/QE2004v034n11ABEH002658/pdf

Pulsed volume discharge in a nonuniform electric field at a high pressure and the short leading edge of a voltage pulse

Forming of an Electron Beam and a Volume Discharge in Air at Atmospheric Pressure

This article reports on experimental studies of subnanosecond electron beams formed in air under atmospheric pressure. An electron beam with an amplitude of ∼170 A with a duration at FWHM of ∼0.3 ns has been obtained. Based on beam temporal characteristics and discharge spatial characteristics, the critical fields were supposed to be reached at plasma approach to anode. Simultaneously, the sharp high-energy pulse of e-beam current is generated. Of critical importance is the cathode type and occurrence on the cathode of plasma protrusions. It is shown that to get maximum amplitude of the electron beam in the gas diode, the discharge in the gas diode should be volumetric.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0263034604221152

On formation of subnanosecond electron beams in air under atmospheric pressure

We have studied the electron beam formation in a diode filled with a molecular gas at atmospheric pressure. A beam current amplitude of up to ∼20 A at an electron energy of ∼70 keV was obtained in an air-filled diode. It is suggested that the main fraction of runaway electrons at low initial values of the parameter E/p (∼0.1 kV/(cm Torr)) is formed in the space between cathode plasma and anode. As the plasma spreads from cathode to anode, the electric field strength between the plasma front and anode increases and the E/p value reaches a critical level.

Electron beams formed in a diode filled with air or nitrogen at atmospheric pressure

An atmospheric-pressure CO2 laser with an electron-beam-initiated discharge produced in a working mixture is developed. The laser output energy of 18 mJ from a ~6-cm3 active volume is achieved. The laser operation with a pulse repetition rate of up to 5 Hz is demonstrated. The specific energy deposit of ~0.1 J cm-3 is obtained in the CO2:N2:He = 1:1:4 gas mixture at the atmospheric pressure during a pulsed nonself-sustained discharge with ionisation amplification.

http://iopscience.iop.org/article/10.1070/QE2003v033n12ABEH002553/pdf

Viktor M Orlovskii

Papers

Pulsed volume discharge in a nonuniform electric field at a high pressure and the short leading edge of a voltage pulse

Forming of an Electron Beam and a Volume Discharge in Air at Atmospheric Pressure

On formation of subnanosecond electron beams in air under atmospheric pressure

Electron beams formed in a diode filled with air or nitrogen at atmospheric pressure

Atmospheric-pressure CO2 laser with an electron-beam-initiated discharge produced in a working mixture