Electrode Configuration In Air Research Articles

The influencing factors of nanosecond pulse homogeneous dielectric barrier discharge in air

In this paper, a bipolar nanosecond high pulse voltage with 20ns rising time was employed to generate homogeneous dielectric barrier discharges using the plate–plate electrode configuration in air at atmospheric pressure. The effects of pulse peak voltage, gas discharge gap, and dielectric plates made by different materials or thicknesses on the discharge homogeneity, voltage–current waveform, and optical emission spectra were investigated. Results show that aforementioned parameters have a strongly impact on the discharge homogeneity and the optical emission spectra, but it is hard to identify definitely their influences on the discharge voltage–current waveform. Homogeneous discharges were easily observed when using low permittivity dielectric plate and the emission intensity of N2 (C3Πu→B3Πg, 0–0, 337.1nm) increases with the rising of pulse peak voltage and the permittivity of dielectric material but decreases with the increasing of gas discharge gap and the dielectric plate thickness. The rotational and vibrational temperatures (Trot and Tvib) were determined at Trot=350±5K and Tvib=3045K via fitting the simulative spectra of N2 (C3Πu→B3Πg, 0–2) with the measured one.

The effect of dielectric thickness on diffuse nanosecond dielectric barrier discharges using a needle array-plate electrode configuration in air at atmospheric pressure

A stable diffuse large-area air plasma with low gas temperature is developed under different dielectric thicknesses by using a needle array-plate electrode configuration in air at atmospheric pressure, which is excited by a bipolar nanosecond pulse power with about 20 ns rising time. The images of the diffuse discharge, electric characteristics, and the optical emission spectra emitted from the diffuse discharge are obtained under different dielectric thicknesses. The discharge area, the average power, the power density, and the emission intensities of N2 (C3Πu → B3Πg, 0-0) and N2+ (B2Σu+ → X2Σg+, 0-0) of the nanosecond dielectric barrier discharges are investigated under different dielectric thicknesses based on the waveforms of discharge voltage and discharge current and the optical emission spectra. The gas temperature of plasma is determined to be approximately 385±5 K by measuring the optical emission spectra of the N2+ (B2Σu+ → X2Σg+, 0-0), and decreases gradually with increasing dielectric thickness. Consistently, an area of approximately 2000 mm2 plasma region under 7 needle electrodes can be formed at 1 mm thick dielectric layer.

Effect of dielectric material on bipolar nanosecond pulse diffuse dielectric barrier discharge in air at atmospheric pressure

In this paper, dielectric plates made by ceramic, quartz and polytetrafluoroethylene (PTFE) respectively are employed to generate low gas temperature, diffuse dielectric barrier discharge plasma by using a needle-plate electrode configuration in air at atmospheric pressure. Both discharge images and the optical emission spectra are obtained while ceramic, quartz and PTFE are used as dielectric material. Plasma gas temperature is also calculated by comparing the experimental emission spectra with the best fitted spectra of N2 (C3Πu→B3Πg 1–3) and N2 (C3Πu→B3Πg 0–2). The effects of different pulse peak voltages and gas gap distances on the emission intensity of N2 (C3Πu→B3Πg, 0–0, 337.1nm) and the plasma area on dielectric surface are investigated while ceramic, quartz and PTFE are used as dielectric material. It is found that the permittivity of dielectric material plays an important role in the discharge homogeneity, plasma gas temperature, emission spectra intensity of the discharge, etc. Dielectric with higher permittivity i.e., ceramic means brighter discharge luminosity and stronger emission spectra intensity of N2 (C3Πu→B3Πg, 0–0, 337.1nm) among the three dielectric materials. However, more homogeneous, larger plasma area on dielectric surface and lower plasma gas temperature can be obtained under dielectric with lower permittivity i.e., PTFE. The emission spectra intensity and plasma gas temperature of the discharge while the dielectric plate is made by quartz are smaller than that while ceramic is used as dielectric material and bigger than that when PTFE is used as dielectric material.

Comparative studies of dc corona and back discharges in different gases

Direct-current corona discharge and back-discharge generated in needle-plate electrode configuration in air, Ar, N2, or CO2, flowing smoothly through a discharge chamber were investigated. The back discharge is dielectric barrier discharge generated in the presence of normal corona discharge, when the plate electrode is covered with a dielectric layer of high resistivity. In the experiments with back discharge a mica plate was used as the dielectric barrier. A small pinhole was made in the plate center to initiate an electrical breakdown through the dielectric layer. Comparative studies of corona and back-corona discharges at normal temperature and pressure were carried out in the aspects of discharge morphology and the current-voltage characteristics.

Space-charge generation and neutralisation in a coaxial cylindrical configuration in air under a negative voltage impulse

The present study deals with space-charge generation and neutralisation. Charge is generated around the central conductor in a coaxial cylindrical electrode configuration in air through the application of a negative impulse voltage. The central conductor potential is suddenly brought to zero at various times after corona onset, leading to positive streamers and different amounts of space-charge neutralisation. Full neutralisation is achieved for earthing times close to the peak amplitude of the impulse voltage while partial neutralisation occurs for longer times. When impulse voltages with fast fronts and long decay times are applied, most of the space charge is neutralised for earthing times up to 100μm.

Investigation of Electron Avalanches in Air using a Cloud Chamber†

ABSTRACT The growth of electron avalanches has been studied in a homogenous field electrode configuration in air using an expansion cloud chamber. The effect of such parameters as the expansion ratio, type of vapour and irradiation of the cathode on the avalanche growth has been studied. The velocity of the avalanche growth was measured in air at pressures of 400, 580 and 680 mm of Hg for values of X/p from 30 to 40 volts/cm/mm. The measurements of Raethor at X/p of 41 volts/cm/mm (pressure 270 mm of Hg) tend to agree with the present experimental values extrapolated. Both the results of Nielsen and Bradbury and Townsend and Tizard appear to be higher by about 12%. Estimates have been made of the thermal energy of the electrons from both the avalanche width and velocity and large discrepancies have been found.