Institute of Physics Publishing Journal of Physics D: Applied Physics (original) (raw)
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The European Physical Journal D, 2010
The spatio-temporal development of single microdischarges in an asymmetric surface barrier discharge arrangement was investigated. The arrangement consisted of two needle electrodes laid on a dielectric plate. The discharge was operated in dry air at atmospheric pressure with a sinusoidal applied voltage. The discharge was investigated by current-voltage measurements as well as two optical techniques, the intensified CCD imaging (equipped with a far-field microscope) and the cross-correlation spectroscopy. While the combined methods of iCCD imaging and far-field microscope recorded two-dimensional pictures with a high spatial resolution, the CCS recorded the spatio-temporal development of the luminosity of the 0-0 transitions of the second positive system (λ = 337.1 nm) and first negative system (λ = 391.5 nm) of molecular nitrogen. The intensities of these two bands were measured with a fine spatial and temporal resolution. It was found that both half periods have significant differences in the mechanism. While the positive half period behaves similar as volume or coplanar barrier discharges, during the negative half period no positive streamer was detected.
Microdischarge propagation and expansion in a surface dielectric barrier discharge
Applied Physics Letters, 2008
We have recorded light emission from a surface dielectric barrier discharge with one exposed and one insulated electrode using an intensified digital camera. The discharge was operated in atmospheric pressure air. When the voltage to the exposed electrode is increasing, streamers form and propagate away from the exposed electrode in 10's of nanoseconds. When the voltage is decreasing, more diffuse microdischarges form in a few nanoseconds. The qualitative behaviors of the plasma agree well with 2-dimensional fluid simulations. Expansion in the average length of microdischarges as the applied voltage changes in both half cycles of the waveform is also observed.
Analysis of two-dimensional microdischarge distribution in dielectric-barrier discharges
Plasma Sources Science and Technology, 2004
The two-dimensional spatial distribution of microdischarges in atmospheric pressure dielectric-barrier discharges (DBDs) in air was studied. Experimental images of DBDs (Lichtenberg figures) were obtained using photostimulable phosphors. The storage phosphor imaging method takes advantage of the linear response of the phosphor for characterization of microdischarge intensity and position. A microdischarge interaction model in DBDs is proposed and a Monte Carlo simulation of microdischarge interactions in the discharge is presented. Comparison of modelled and experimental images indicates interactions and short-range structuring of microdischarge channels.
A Study of Two-Dimensional Microdischarge Pattern Formation in Dielectric Barrier Discharges
Plasma Chemistry and Plasma Processing, 2006
Although microdischarges in dielectric-barrier discharges (DBDs) have been studied for the past century, their mutual interaction was explained only recently. This interaction is responsible for the formation of microdischarge patterns reminiscent of two-dimensional crystals. Depending on the application, microdischarge patterns may have a significant influence on DBD performance, particularly when spatial uniformity is desired. This paper presents the results of study of regular microdischarge pattern formation in DBD in air at atmospheric pressure. Experimental images of DBD (Lichtenberg figures) were obtained using photostimulable phosphors. A new method for analysis of microdischarge patterns that allow measuring the degree of pattern regularity was developed. Simulated and experimental patterns were compared using the newly developed method and comparison indicates the presence of interaction between microdischarges. Analysis of microdischarge patterns shows that regularity of the patterns increases with the number of excitation cycles used to produce the pattern.
Striated microdischarges in an asymmetric barrier discharge in argon at atmospheric pressure
Physical Review E, 2011
The investigation of striated microdischarges in barrier discharges in argon at atmospheric pressure is reported. Microdischarges were investigated by means of electrical measurements correlated with intensified CCD camera imaging. The scaling law theory known from low-pressure glow discharge diagnostics was applied in order to describe and explain this phenomenon. The investigated microdischarge is characterized as a transient atmospheric-pressure glow discharge with a stratified column. It can be described by similarity parameters i/r ≈ 0.13 A/cm, pr ≈ 5 Torr cm, and 3 < λ/r < 5 with the current i, pressure p, interval of subsequent striations λ, and radius of the plasma channel r. An attempt to describe the mechanism of creation of a striated structure is given, based on an established model of the spatial electron relaxation.
2007
In contrast to electric field lines in gas discharge systems with bare electrodes, electric field lines in dielectric barrier discharge systems, where the cathode is covered with the dielectric layer, may cross the dielectric surface at an oblique angle. The secondary electrons emitted from this surface either return to the cathode due to collisions with background gas atoms or eventually escape from the region near the cathode. Using the diffusion P1-approximation to the kinetic equation for electrons, we have found analytically the electron escape factor k for different limiting cases. Monte-Carlo simulations of backscattering of electrons have been performed for noble gases and the dependence of the escape factor on the angle between the electric filed lines and the dielectric surface have been found. The analytical theory has been used to explain unexpected peculiarities in results of Monte-Carlo simulations.
Journal of Physics: Conference Series, 2010
Dielectric-barrier discharges (DBDs) are characterized by the presence of at least one insulating layer in contact with the discharge between two planar or cylindrical electrodes connected to an AC/pulse power supply. The dielectric layers covering the electrodes act as current limiters and prevent the transition to an arc discharge. DBDs exist usually in filamentary mode, based on the streamer nature of the discharges. The main advantage of this type of electrical discharges is that nonequilibrium and non-thermal plasma conditions can be established at atmospheric pressure. VUV/UV sources based on DBDs are considered as promising alternatives of conventional mercury-based discharge plasmas, producing highly efficient VUV/UV radiation. The experiments have been performed using two coaxial quartz double barrier DBD tubes, which are filled with Xe/Ar at different pressures. A sinusoidal voltage up to 2.4 kV peak with frequencies from 20 to 100 kHz has been applied to the discharge electrodes for the generation of microdischarges. A stable and uniform discharge is produced in the gas gap between the dielectric barrier electrodes. By comparisons of visual images and electrical waveforms, the filamentary discharges for Ar tube while homogeneous discharge for Xe tube at the same conditions have been confirmed. The electrical modeling has been carried out to understand DBD phenomenon in variation of applied voltage waveforms. The simulated discharge characteristics have been validated by the experimental results.
Kinetic simulation of a nanosecond-pulsed hydrogen microdischarge
Applied Physics Letters, 2011
The electron dynamics in a nanosecond-pulsed microdischarge in high pressure hydrogen gas is investigated space and time resolved by particle-in-cell simulations. The discharge is driven by a 10 ns voltage pulse with a peak of 1.3 kV followed by an approximately constant voltage of 300 V during 150 ns. The time resolved current, electric field, electron density, and spatio-temporal excitation rates are compared to experimental and modeling results under identical discharge conditions. Via this synergistic approach, the development of the discharge and the different phases of distinct electron dynamics are identified and understood.
Dielectric-Barrier Discharges. Principle and Applications
Le Journal de Physique IV, 1997
Dielectric-barrier discharges (silent discharges) are non-equilibrium discharges that can be conveniently operated over a wide temperature and pressure range. At about atmospheric pressure electrical breakdown occurs in many independent thin current filaments. These short-lived microdischarges have properties of transient high pressure glow discharges with electron energies ideally suited for exciting or dissociating background gas atoms and molecules. The traditional application for large-scale ozone generation is discussed together with novel applications in excimer UV lamps, high power CO, lasers and plasma display panels. Additional applications for surface treatment and pollution control are rapidly emerging technologies. Recent results on greenhouse gas recycling and utilisation in dielectric-barrier discharges are also discussed.