[Show abstract][Hide abstract] ABSTRACT: The techniques of spatially resolved cross-correlation spectroscopy (CCS) and current pulse oscillography were used to carry out systematic investigations of the barrier discharge (BD) in the binary gas mixtures N 2 /O 2 at atmospheric pressure. At very low oxygen concentrations (<500 ppm), the BD was observed in a so-called diffuse mode (also referred to as atmospheric pressure glow discharge, glow silent discharge or homogeneous BD). In the case of the BD filamentary mode, the spatio-temporal distributions of the BD radiation intensities were recorded for the spectral bands of the 0–0 transitions of the second positive (λ = 337 nm) and first negative system of molecular nitrogen (λ = 391 nm). In the case of the diffuse mode, the spectral bands λ = 337 nm, λ = 260 nm (0–3 transition of the γ -system of NO) and λ = 557 nm (radiation of ON 2 excimer) were used for this purpose. The velocities of the cathode-directed ionizing waves as well as the effective lifetimes of the excited states N 2 (C 3 u) υ =0 and N + 2 (B 2 + u) υ =0 were evaluated from the CCS data. Special attention was devoted to the investigation of the transition between the filamentary and diffuse modes of the BD, this transition being caused by the variation of oxygen content within the range 500–1000 ppm.
Journal of Physics D Applied Physics 02/2005; 38(4):518-529. DOI:10.1088/0022-3727/38/4/003 · 2.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Barrier discharges (BDs) produce highly non-equilibrium plasmas in a controllable way at atmospheric pressure, and at moderate gas temperature. They provide the effective generation of atoms, radicals and excited species by energetic electrons. In the case of operation in noble gases (or noble gas/halogen gas mixtures), they are sources of an intensive UV and VUV excimer radiation. There are two different modes of BDs. Generally they are operated in the filamentary one. Under special conditions, a diffuse mode can be generated. Their physical properties are discussed, and the main electric parameters, necessary for the controlled BD operation, are listed. Recent results on spatially and temporally resolved spectroscopic investigations by cross-correlation technique are presented. BDs are applied for a long time in the wide field of plasma treatment and layer deposition. An overview on these applications is given. Selected representative examples are outlined in more detail. In particular, the surface treatment by filamentary and diffuse BDs, and the VUV catalyzed deposition of metallic layers are discussed. BDs have a great flexibility with respect to their geometrical shape, working gas mixture and operation parameters. Generally, the scaling-up to large dimensions is of no problem. The possibility to treat or coat surfaces at low gas temperature and pressures close to atmospheric once is an important advantage for their application.
[Show abstract][Hide abstract] ABSTRACT: Dielectric barrier discharges can be operated in a diffuse (glow-like) mode at atmospheric pressure in nitrogen, helium and neon, provided that the feeding sinusoidal voltage is within the kHz range. These homogeneous discharges have been investigated by spatio-temporally resolved emission spectroscopy. The analysis of experimental data including their comparison with the corresponding results of numerical modelling enables to clarify the mechanisms of discharge development. These mechanisms appear to be essentially different for the cases of noble gases and nitrogen. For example in nitrogen the maximum of light intensity is located at the anode, while in helium and neon a cathode directed propagation of a luminosity wave is observed.
[Show abstract][Hide abstract] ABSTRACT: The technique of spatially resolved cross-correlation spectroscopy (CCS) is used to carry out diagnostic measurements of the barrier discharge (BD) in air at atmospheric pressure. Quantitative estimates for electric field strength E(x, t) and for relative electron density n e (x, t)/n max e are derived from the experimentally determined spatio-temporal distributions of the luminosity for the spectral bands of the 0–0 transitions of the second positive system of N 2 (λ = 337.1 nm) and the first negative system of N + 2 (λ = 391.5 nm). These results are used to test the validity of some physical models of electrical breakdown in a BD. The influence of the spatio-temporal structure of the discharge on the chemical kinetics of ozone synthesis is studied by means of a semi-empirical method based on the results of spatially resolved CCS measurements.
Journal of Physics D Applied Physics 11/2001; 34(21):3164-3176. DOI:10.1088/0022-3727/34/21/309 · 2.72 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The entire range of gas phase reaction products, depending on the composition of initial binary mixtures of methane and carbon dioxide in dielectric barrier discharges, has been determined (saturated as well as unsaturated hydrocarbons and oxygenated organic compounds). The macro-kinetics of the basic chemical pathways of the system under consideration has been investigated. This system is found to display a strong feedback effect (positive or negative, depending on the initial state of the surfaces, as well as the chemical composition of the feed-gas mixture). It is demonstrated that these properties undergo significant changes during operation, due to surface modification processes (polymer film deposition, its oxidation or reduction). They are found to exert a considerable influence on the chemical efficiency of the discharge (for example, on the absolute and relative chemical yields of the reaction products), the Lissajous figures appear to be a sensitive tool to monitor the operation conditions of the discharge.
Plasmas and Polymers 11/2000; 5(3):129-150. DOI:10.1023/A:1011302017354
[Show abstract][Hide abstract] ABSTRACT: The temporal and spatial development of a single filament barrier discharge was investigated at atmospheric pressure. The used technique allows spectral and phase resolved measurements in the time scale 1 ... 200 ns at a spatial resolution of 0.1 mm. The single filament is produced with the frequency of about 6 kHz. A symmetrical electrode arrangement with both electrodes covered by the dielectrics (glass or alumina, discharge gap width of 1mm) was used. The time resolution in the sub ns scale was realized by a correlation technique in single photon counting mode /1/. The spectral investigations are focussed on the second positive system (wavelength 337 nm) and the first negative system (wavelength 391 nm) of nitrogen. The measurements allow a detailed visualization and interpretation of the streamer development. In combination with a kinetic model of the dominant excitation as well quenching processes there is the possibility to get informations on the temporal and spatial development of the reduced field strength E/n, too. /1/ K. V. Kozlov et al, Proc. XIth Conf. on Gas Discharges and their Applications (1995) II-42
[Show abstract][Hide abstract] ABSTRACT: The influence of the chemical composition of the feeding gas mixtures CH4-He on the physical properties of dielectric barrier discharge was investigated experimentally as well as theoretically. Certain
changes in the shape of charge-voltage characteristics (Lissajous figures) were observed when the content of He was varied
within the range 0–90%. An increase of the He concentration was found to cause monotonous but not linear decrease of the ignition
voltage as well as of the burning voltage of the discharge. Measurements of the burning voltage were used to estimate the
characteristic energy of electrons in the mixtures under consideration. These estimates were compared with experimentally
determined values of the energy consumption for the synthesis of C2H2, C2H4 and C2H6, respectively. It was demonstrated that the observed dependencies of the energy consumption upon He content can be explained
taking into consideration the influence of the chemical composition of feeding gas mixture upon the characteristic energy
of electrons in the dielectric barrier discharge.
[Show abstract][Hide abstract] ABSTRACT: On the basis of the electron Boltzmann equation and of the balances for the charge carriers (e, H+, H2+, H3+), the H-atoms and the metastable H(2s)-atoms for the H/H2-mixture the behaviour of the weakly turbulent, band-like electron-beam discharge plasma in hydrogen has been calculated taking into account the main collision and transport processes. In dependence of the normalized discharge length, the life time of the neutral particles in the band-like plasma and the electron beam generated turbulence energy density the ionization and dissociation budget and in particular the most important electron-heavy particle collision rates, which appear in the balance equation system, are investigated in the present part of our paper. In a second part the results related to the budget of the ions and the metastable atomic state will be reported and an analysis of the main processes in the balances will be made.
Beiträge aus der Plasmaphysik 01/1981; 21(2):87 - 108. DOI:10.1002/ctpp.19810210204 · 0.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In the first part  of our paper a kinetic model for the band-like beam discharge plasma in hydrogen was derived, numerically obtained results on the ionization and dissociation degree were presented and a detailed explanation of the influence of the electron kinetic properties on the macroscopic plasma behaviour was given. Continuing these investigations, we now report and discuss the results on the ion- and metastable atom-budget. On this basis an analysis is made of the resulting balance equation system with a view to finding the most important physical processes, and a simplified equation system is derived which allows to interpret the essential features of the macroscopic plasma properties.
Beiträge aus der Plasmaphysik 01/1981; 21(3):143-162. DOI:10.1002/ctpp.19810210302 · 0.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Auf der Grundlage der Lösung der Boltzmann-Gleichung für das Elektronengas werden die Teilchenbilanzen verschiedener Ionen (H+, H2+, H3+, H3+, H5+) und der neutralen Komponenten im H/H2-Säulenplasma unter Berücksichtigung zahlreicher Elementprozesse (Volumen- und Wand-prozesse) diskutiert. Dies liefert ein detailliertes Verständnis der elektrischen Charakteristik des Plasmas in Verbindung mit der chemischen Zusammensetzung des Gases. Im Bereich kleiner Drücke und höherer Ströme treten große Dissoziationsgrade auf. Experimentelle Untersuchungen bestätigen diese theoretischen Ergebnisse. Auf noch bestehende Unterschiede zwischen der gemessenen und berechneten elektrischen Charakteristik wird hingewiesen.
Based on the solution of the electron Boltzmann equation the particle balances of different ions (H+, H2+, H3+, H5+) and of the neutral components are discussed in the H/H2, column plasma taking into account a large number of elementary processes (volume and wall processes). This results in a detailed understanding of the electric characteristic in relation to the chemical composition of the gas. In the region of low pressures and larger currents considerable high degrees of dissociation occur. Experimental investigations confirm these theoretical results. Remaining differences between the measured and calculated electric characteristic are mentioned.
Beiträge aus der Plasmaphysik 01/1980; 20(4):265-281. DOI:10.1002/ctpp.19800200404 · 0.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Nach der Darlegung der für die diffusionstheoretische Beschreibung des Säulenplasmas der Wasserstoffentladung wesentlichen Reaktionsmechanismen der Ionisation, der Dissoziation, der dissoziativen Rekombination, der Ionen-Molekülumwandlungen und der Neutralteilchenumwandlungen wird ein System von Bilanzgleichungen für die H4+-, H2+-, H3+- und H5+-Ionen, die Wasserstoffatome, das Neutralgasgemisch, die Ladungsneutralität und den Entladungsstrom hergeleitet und die Lösungsmethode dieses Systems erläutert. In den nachfolgenden Teilen werden konkrete Ergebnisse der numerischen Berechnung teilweise im Vergleich zu experimentellen Resultaten vorgestellt.
After the discussion of the main reaction mechanisms as ionization, dissociation, dissociative recombination, ion-molecule-reactions and chemical reactions between neutral particles a system of balance equations for the ions H+, H2+, H3+, and H5+, for the atoms, for the mixture of neutral particles, for charge neutrality and the discharge current is given in the framework of the diffusion theory. The numerical method for the solution of this system is explained. In the following parts of this paper detailed results of the numerical calculation will be dicussed in comparison with some experimental investigations.
Beiträge aus der Plasmaphysik 01/1980; 20(1):25-37. DOI:10.1002/ctpp.19800200103 · 0.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Für das stationäre und homogene H/H2-Mischplasma werden die Ergebnisse der Berechnung des Isotropteils der Geschwindigkeitsverteilungsfunktion f(U), der Transportgrößen Ū, be, De. der Stoßfrequenzen für Dissoziation und Direktionisation sowie aller wesentlichen Energieverluste durch elastische und unelastische Stöße an die Komponenten des Mischplasmas mitgeteilt. Diese Berechnungen erfolgten mittels der Boltzmanngleichung der Elektronen in Abhängigkeit von der normierten elektrischen Feldstärke E/p0 und der Gemischzusammensetzung xD und wurden für E/p0-Werte von 7,5–100 V/cm Torr und für beliebige Gemischzusammensetzung durchgeführt.
The results of the calculation of the energy distribution function f(U), of the transport coefficients Ū, be, De, of the collision frequencies for dissociation and direct ionization and of the main energy loss rates due to elastic and inelastic collisions of the electrons with the components of the mixture are presented for a stationary and homogeneous hydrogen plasma. These calculations, based upon the Boltzmann equation for the electrons, are performed in dependence of the normalized electric field strength E/p0 and the mixture ratio xD in the range of 7.5 to 100 V/cm Torr for E/p0 and for any mixture ratio.
Beiträge aus der Plasmaphysik 01/1980; 20(2):97-109. DOI:10.1002/ctpp.19800200204 · 0.84 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In den vorausgegangenen Teilen dieser Arbeit wurde ein Bilanzgleichungssystem zur mikro-physikalischen Beschreibung des Wasserstoffplasmas hergeleitet, die Elektronenkinetik im H/H2-Mischplasma analysiert und Ergebnisse über die Berechnung der inneren Säulenparameter für verschiedene Entladungsbedingungen vorgestellt. In Fortsetzung dieser Arbeiten werden in diesem Teil der Einfluß zweier Grenzfälle der Druckbilanz und der Änderung der Neutralgastemperatur auf die inneren Säulenparameter untersucht sowie die Frage der Ähnlichkeitsdarstellung der makroskopischen Säuleneigenschaften behandelt.In the former parts of this paper a balance equation system was derived for the microphysical description of the hydrogen plasma, the electron kinetics was studied in the H/H2-mixture plasma and results concerning the computation of the inner column parameters were presented for different discharge conditions. In continuation of these former investigations in this paper the influence of two different limits of the pressure balance and of the alteration of the neutral gas temperature on the inner column parameters is analysed and the aspect of a similarity representation of the macroscopic column properties is discussed.
Beiträge aus der Plasmaphysik 01/1980; 20(6):403-415. DOI:10.1002/ctpp.19800200603 · 0.84 Impact Factor