Pulsed discharge plasma and its application is one of the promising directions in civilian areas of pulsed power technology. In order to promote the research and development of the theory and application technology for pulsed discharge plasma, in this paper, recent progress on the mechanism of nanosecond-pulse gas discharge and the characteristics and applications of typical pulsed plasma at the Institute of Electrical Engineering, Chinese Academy of Sciences is reviewed. Firstly, progress on mechanism of nanosecond-pulse discharge based on runaway electrons and measurement technology of runaway electrons is introduced. Then, the characteristics of three typical discharges, including direct-driven pulsed discharge, pulsed dielectric barrier discharge and pulsed plasma jet, are reviewed. Furthermore, typical plasma applications of pulsed plasma on surface modification and methane conversion are presented.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/hve.2016.0014

Atmospheric-pressure pulsed discharges and plasmas: mechanism, characteristics and applications

Efficient Light Coupler for Threshold Čerenkov Counters

The concepts of local and nonlocal models of the breakdown of dense gases are introduced. The basis for a nonlocal model with runaway electrons is discussed. Experimental results on electric discharges in dense gases which develop in a regime of intense electron runaway, in contrast with the classical forms of gas discharges, are reviewed. It is shown that electron runaway plays a fundamental role in the breakdown dynamics of dense gases over a wide range of conditions. Space-time and energy characteristics of the pulses of runaway electrons and of the accompanying x radiation are reported. The involvement of runaway electrons in the breakdown mechanism can be seen in a shift of the minimum on the U(Pd) curves toward higher values of Pd as the overvoltage increases. When the overvoltage reaches a large factor, a polarization selfacceleration, as discussed by Askar'yan, occurs, and runaway electrons with energies e > eUmax are generated. The breakdown of a dense gas in a strong field differs from that at a moderate overvoltage in that it ceases to be a purely volume process.

https://iopscience.iop.org/article/10.1070/PU1990v033n07ABEH002606/pdf

High-voltage nanosecond discharge in a dense gas at a high overvoltage with runaway electrons

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

We investigate structure and evolution of long positive spark breakdown; and we study at which stage pulses of hard x-rays are emitted. Positive high-voltage pulses of standardized lightning impulse wave form of about 1MV were applied to about 1m of ambient air. The discharge evolution was imaged with a resolution of tens of nanoseconds with an intensified CCD camera. LaBr3(Ce + ) scintillation detectors recorded the x-rays emitted during the process. The voltage and the currents on both electrodes were measured synchronously. All measurements indicate that first a large and dense corona of positive streamers emerges from the high-voltage electrode. When they approach the grounded electrode, negative counter-streamers emerge there, and the emission of hard x-rays coincides with the connection of the positive streamers with the negative counter-streamers. Leaders are seen to form only at later stages. (Some figures may appear in colour only in the online journal)

/pdf/experimental-study-of-hard-x-rays-emitted-from-metre-scale-w8en32yini.pdf

Experimental study of hard x-rays emitted from metre-scale positive discharges in air

Observation of X-rays from spark discharges in a spark chamber

We have analyzed 25 000 ${K}_{e3}$ decays, reconstructed to the center of mass by measurement of the ${{K}_{L}}^{0}$ momentum from time of flight and measurement of the $\ensuremath{\pi}$ and $e$ momenta with a spark-chamber-magnet spectrometer. Using the linear parametrization of the vector form factor ${f}_{+}({q}^{2})=1+{\ensuremath{\lambda}}_{+}(\frac{{q}^{2}}{{{m}_{\ensuremath{\pi}}}^{2}})$ we find ${\ensuremath{\lambda}}_{+}=0.0270\ifmmode\pm\else\textpm\fi{}0.0028$. Upper limits for the scalar (${f}_{s}$) and tensor (${f}_{t}$) form factors at the 68% confidence level are $\frac{{f}_{s}}{{f}_{+}}l0.04$, $\frac{{f}_{t}}{{f}_{+}}l0.23$, corresponding to intensity ratios $\frac{{I}_{s}}{{I}_{v}}=0.3%$ and $\frac{{I}_{t}}{{I}_{v}}l0.4%$.

Experimental Measurement of the Form Factors of the Decay K L 0 → π ± e ∓ ν

TIME DEPENDENCE OF K/sub e3/$sup 0$ DECAYS.

A large pressurized gas Cerenkov counter is described. The counter is designed to assist triggering on electrons in high energy counter‐spark chamber experiments. The requirement of large solid angle resulted in a counter of large dimensions and heavy construction. The results of tests made on the counter are presented. The tests indicate that the counter rejects pions very well and is roughly 50% efficient to electrons in the Λ° beta‐decay spectrum (0–200 MeV).

Large gas filled cerenkov counter

The total cross sections for ${\ensuremath{\Lambda}}^{0}$ production by $925\ensuremath{-}\mathrm{M}\mathrm{e}\mathrm{V}$ ${\ensuremath{\pi}}^{\ensuremath{-}}$ mesons in Be, C, Al, Cu, and W have been measured. The data suggest a simple production model with cross sections for medium-to-heavy nuclei varying as $(\frac{Z}{A}){A}^{\frac{1}{3}}$. For Be, the energy dependence of the ${\ensuremath{\Lambda}}^{0}$ yield has been obtained in the region 750-1100 MeV.

O. Van Dyck

Papers

Observation of X-rays from spark discharges in a spark chamber

Experimental Measurement of the Form Factors of the Decay K L 0 → π ± e ∓ ν

TIME DEPENDENCE OF K/sub e3/$sup 0$ DECAYS.

Large gas filled cerenkov counter

Cross Sections for Λ 0 Production by π - Interactions in Nuclei