Uniform and filamentary nature of continuous-wave and pulsed dielectric barrier discharge plasma (original) (raw)
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Atmospheric pressure plasma of dielectric barrier discharges
Pure and Applied Chemistry, 2000
The dielectric barrier discharge (DBD) has a number of industrial applications and has been a subject of research for many years. Many studies have been carried out to understand the underlying DBD physics. Despite the fact that much progress has been made, some important issues are still far from being clear. In this work, we summarize the basics of DBD physics and introduce innovative concepts of discharge behavior that were discovered recently.
Plasma Processes and Polymers, 2010
The reported dielectric barrier discharge (DBD) source comprises of a ceramic-covered copper electrode, and plasma can be ignited in ambient air with grounded 'opposite' electrodes or with objects of high capacitance (e.g., human body), when breakdown conditions are satisfied. Filamentary plasma mode is observed when the same source is operated using grounded opposite electrodes like aluminium plate and phosphate buffered saline solution, and a homogeneous plasma mode when operated on glass. When the source is applied on human body, both homogeneous and filamentary discharges occur simultaneously which cannot be resolved into two separate discharges. Here, we report the characterization of filamentary and homogeneous modes of DBD plasma source using the above mentioned grounded electrodes, by applying optical emission spectroscopy, microphotography and numerical simulation. Averaged plasma parameters like electron velocity distribution function and electron density are determined. Fluxes of nitric oxide, ozone and photons reaching the treated surface are simulated. These fluxes obtained in different discharge modes namely, single-filamentary discharge (discharge ignited in same position), stochastical filamentary discharge and homogeneous discharge are compared to identify their applications in human skin treatment. It is concluded that the fluxes of photons and chemicallyactive particles in the single filamentary mode are the highest but the treated surface area is very small. For treating larger area, the homogeneous DBD is more effective than stochastical filamentary discharge. -7.5 -5.0 -2.5 0.0 2.5 5.0 7.5 1E16 1E18 1E20 1E22 Flux of ozone / m -2 s -1 radius of electrode / mm 1 ppm single-filamentary DBD homogeneous DBD stochastic-filamentary DBD Plasma Process. Polym. 2010, 7, 665-675 ß
Power consideration in the pulsed dielectric barrier discharge at atmospheric pressure
Journal of Applied Physics, 2004
Nonequilibrium, atmospheric pressure discharges are rapidly becoming an important technological component in material processing applications. Amongst their attractive features is the ability to achieve enhanced gas phase chemistry without the need for elevated gas temperatures. To further enhance the plasma chemistry, pulsed operation with pulse widths in the nanoseconds range has been suggested. We report on a specially designed, dielectric barrier discharge based diffuse pulsed discharge and its electrical characteristics. Two current pulses corresponding to two consecutive discharges are generated per voltage pulse. The second discharge, which occurs at the falling edge of the voltage pulse, is induced by the charges stored on the electrode dielectric during the initial discharge. Therefore, the power supplied to ignite the first discharge is partly stored to later ignite a second discharge when the applied voltage decays. This process ultimately leads to a much improved power transfer to the plasma.
Journal of Advanced Oxidation Technologies, 2003
Investigations were carried out on point-to-plane dielectric barrier discharges with two different gas gap lengths (d = 0 and 2 mm), energized with two different high voltage power supplies providing one an ac signal at 15 kHz and the other a pulsed signal with a same repetition rate. Correlations between the electrical properties and the behavior of the plasma in these different situations were established through ozone generation, and by the way O radicals net production, checking for this purpose that in our operating conditions gasheating influence remained minor. Using the representation ozone concentration vs. charge amount transferred through current pulses, the specific electrical and thus physical properties of pulsed surface discharges are put in light; in these discharges, compared to ac and pulsed volume discharges, current pulses exhibit, for a given charge per pulse, the highest amplitudes and the shortest durations.
The Transition Between Different Discharge Regimes in Atmospheric Pressure Air Barrier Discharge
Contributions to Plasma Physics, 2007
Key words APG in air, diffuse barrier discharge, OAUGDP. PACS 52.80. Hc, 52.50.Dg In our previous work [1], we have demonstrated the possibility of observing the transition from a filamentary dielectric barrier discharge operation regime into the diffuse barrier discharge regime in air at atmospheric pressure. This work presents our attempt to reproduce the transition conditions in newly constructed transparent discharge reactor. The role of appropriate power supply and dielectric barrier to stabilize the discharge in a Townsend-to-glow discharge region is investigated and discussed. Unlike operating in nitrogen, a streamer mechanism is involved in the formation of the uniform air plasma. Nevertheless the electrical current waveform of a diffuse streamer pulse differs from the filamentary streamer pulse, as the diffuse mode pulse exhibits an extended tail part.
Diagnostics of dielectric barrier discharge plasma and comparison of the results with PIC code
2012 Abstracts IEEE International Conference on Plasma Science, 2012
This paper reports the spectroscopic analysis in volume discharge arrangement of a dielectric barrier discharge source in parallel plate geometry of a width of 2 mm. Helium is used as a working gas. The investigations are carried out using sinusoidal supply for the generation of discharges where two current pulses have been observed with different polarities in one period. The electron plasma density and temperature during the discharge have been estimated using the line-ratio technique from the observed visible neutral helium lines. To validate the results, a commercial particle-in-cell simulation code, OOPIC-Pro, has been used, which confirms filamentary as well as diffused discharges observed in the experiment. This code analysis also validates the estimated electron plasma density and temperature measurements at two different working pressures and at a fixed operating frequency.
Dependence of dielectric barrier discharge jet length on gas flow rate and applied voltage
The effect of gas flow rate of helium and argon on the length of dielectric barrier discharge (DBD) jet generated under atmospheric pressure using an AC source is investigated. It is found that as the flow rate increases, the jet length increases up to a maximum length. Upon further increase in flow rate, it will cause the jet length to decrease. Visual inspection shows the jet to be of laminar flow when its length was increasing, and gets turbulent when the jet length decreases with increased flow rate. There is an obvious increment in jet length of argon DBD system when the applied voltage is increased from 8.8 kV to 11.0 kV, but not in helium. Spectral analysis reveals the DBD jet to comprise of emission lines of its constituent flow gas. In addition to that, emission lines of component gases (N 2 and O) in ambient air and water vapour were also present. Upstream jet was obtained only in helium DBD jet at low flow rate but high applied voltage.
Diagnostic of plasma discharge parameters in helium filled dielectric barrier discharge
Journal of Theoretical and Applied Physics, 2012
This paper reports the plasma discharge analysis of a dielectric barrier discharge (DBD) source. Helium is used as a working gas. The analysis is performed at fixed working pressure and operating frequency. The investigations are carried out using sinusoidal supply for the generation of discharges where two current pulses have been observed with different polarities in one period. A homogeneous type of discharge has been observed for different operating conditions in this DBD source. Since in situ diagnostics are not possible due to the small geometries in the used DBD source, the electrical measurements and spectroscopic analysis of the discharge have been performed to analyse the plasma discharge. The electrical analysis has been carried out using equivalent electrical circuit model. The plasma density and temperature within the discharge have been estimated using line ratio technique of the observed visible neutral helium lines. The estimated electron plasma density is found to be in close proximity with the plasma simulation code 'OOPIC Pro'.