bluuebunny/crossref_metadata_2025_split huggingface dataset:
[Russian Text Ignored]
Authors: [Russian Text Ignored]  
Published: July 2007

AbstractThis paper is devoted to the investigation of a turbulent heated beam discharge plasma in the molecular gas hydrogen as an example. We are interested in the stationary behaviour of this plasma type under the condition of weak Langmuir turbulence and under the action of several kinds of interaction processes. This discharge plasma is of increasing importance especially from the point of plasmachemical purposes.At first we give a short development of the kinetic equation employed including the Coulombinteraction between the charged particles as well as the different kinds of binary collision processes between electrons and non‐exited molecules. The essential parameters in this description are the full energy density of the Langmuir turbulence per one electron e0Ū = W/ne and the degree of ionization ne/N. In a broad range of these two parameters Ū and ne/N, which are typical for a beam discharge plasma, we determined numerically the velocity distribution function of the electrons and with the aid of this especially the mean energy, the energy gain from the turbulent field, the frequencies for the several collision processes as well as the energy losses due to the binary collisions and the Coulomb interaction between electrons and ions.In particular we investigated the main energy channels by which the energy of the electrons is transfered into the several degrees of freedom of the molecular gas and into the ion component.
Selfconsistent Electron Energy Distribution Functions in Non Equilibrium oxygen: Effects on the Dissociation Rate
Authors: Capitelli M. , Dilonardo M. , Gorse C. 
Published: July 2007

AbstractElectron energy distribution functions (edf) in non equilibrium oxygen have been calculated by solving the Boltzmann equation coupled to a system of vibrational master equations. The results show the importance of both superelastic vibrational collisions and of the presence of oxygen atoms in affecting edf.The coupling between the Boltzmann equation and the system of vibrational master equations brings to a temporal evolution of edf, which progressively changes from a cold molecular gas situation (all molecules in the ground vibrational level) to a vibrationally excited molecular gas and finally to a gas composed by oxygen molecules and oxygen atoms.All electronic rate coefficients follow a temporal evolution. due to the corresponding evolution of edf.Finally the present results are used for discussing the dissociation rate of molecular oxygen in electrical discharges.
Nonlinear Resonant Interaction of Three Extra‐ordinary Waves in a Hot Electron Plasma
Authors: Das K. P. , Sihi S. 
Published: July 2007

AbstractThe coupled mode equations and coupling coefficients for the resonant nonlinear interaction of three extra‐ordinary waves in a hot magnetized plasma are derived by Whitham's method of averaged Lagrangian. The wave vectors of the three waves are taken as noncollinear and perpendicular to the external uniform magnetic field. Of the three waves one is of high frequency mode and the other two are of low frequency mode.
Relaxation of Plasma Electrons towards Stationary States as Related to Different Initial Energy Distributions and for a Wide Range of the Final Electric Field Strength
Authors: Wilhelm J. , Winkler R. 
Published: July 2007

AbstractStarting from former investigations concerning the collision dominated relaxation of the electron component in weakly ionized inert gas plasma we generalize the results obtained. Also in the present paper we use the same adaquate kinetic equation for the electron energy distribution function. On one side the influence of non‐stationary, analytically given initial energy distributions on the relaxation behaviour and on the resulting adjustment time of stationary states was investigated. On the other side the calculation, especially of the adjustment time, was extended to a whole variety of final stationary states ranging from those determined only by energy loss due to elastic collisions to those determined only by exciting collisions. The adjustment time obtained varies by about four orders of magnitude within this wide range of final stationary states.
Diffusionstheoretische Beschreibung der Dissoziation und des Ionenhaushaltes im schwachionisierten Säulenplasma der Wasserstoffentladung. III. Kenngrößen der positiven Säule bei verschiedenen Drücken (0,3 … 10 Torr) und Strömen (10−4 … 1 A)
Authors: Michel P. , Pfau S. , Rutscher A. , Winkler R. 
Published: July 2007

AbstractAuf 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.
Diffusionstheoretische Beschreibung der Dissoziation und des Ionenhaushaltes im schwachionisierten Säulenplasma der Wasserstoffentladung. IV. Grenzfälle der experimentell realisierbaren Druckbilanz — Variation der Gastemperatur — Ähnlichkeitsdarstellung der Plasmaparameter
Authors: Michel P. , Pfau S. , Rutscher A. , Winkler R. 
Published: July 2007

AbstractIn 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.
Influence of Electrode Material on Time Delay of Electrical Breakdown in Gases
Authors: Pejović M. M. , Bošan Dj. A. , Krmpotić Dj. M. 
Published: July 2007

AbstractA significant correlation between the work function of electrode material and the statistical time delay of electrical breakdown in nitrogen‐filled diodes has been established. The results obtained confirm that time delay of electrical breakdown increases with increasing of electrode material work function.
On the Averaged Forces in Bounded Plasma in Parallel Electric and Magnetic Fields
Authors: Nikolov N. A. , Malinov P. N. , Yanovsky A. B. 
Published: July 2007

AbstractAveraged forces of Miller's type, acting on the particles of a bounded plasma in parallel external a. c. electric and d. c. magnetic fields, are found on the basis of the equations of the two‐component MHD. It is assumed, that standing transverse waves are excited in the plasma by the external source before the a. c. electric field is switched on.
Interaction of a Low Frequency Coherent Magneto‐Acoustic Wave with a Turbulent Spectrum of Extra‐Ordinary Waves
Authors: Das K. P. , Sluijter F. W. 
Published: July 2007

AbstractStarting from nonlinear evolution equations of a three‐dimensional extra‐ordinary wavepacket in a magnetized plasma and introducing a correlation function, equations are derived that describe interaction of a coherent low‐frequency magneto‐acoustic wave with a turbulent spectrum of high frequency extra‐ordinary waves. These equations are used to derive the dispersion relation for a low frequency magnetoacoustic wave in the presence of a spectrum of turbulent high frequency extra‐ordinary waves. In the narrow spectrum case, it is found that a small but finite spread in the spectrum of turbulence has a stabilizing influence on the instability which exists for vanishing spectral width. In the wide spectrum case, the effect of a weak turbulent spectrum of extra‐ordinary waves is to produce a slight shift in frequency of the coherent low frequency magneto‐acoustic wave and to damp or excite the wave.
Kinetic Study of Electron Beam Excited Argon
Authors: Bretagne J. , Godart J. , Puech V. 
Published: July 2007

AbstractAn experimental and theoretical study of the interaction between Argon and a high‐energy short‐pulse electron beam is reported. A theoretical model describing the argon atom and molecule with ten effective levels and taking into account all the reactions that these levels may suffered is developped. A comparison, based on time resolved V.U.V. and visible fluorescences and electron density determination, between the theoretical and experimental results shows the ability of our model to describe the interaction in all the experimental range, 400 < P < 5000 Torr, studied.
The Influence of the Fluctuation Amplitude on the Probe Characteristic
Authors: Klagge S. , Maass M. 
Published: July 2007

AbstractThe time‐averaged probe current is calculated by using a sampling method for sinusoidal and sawtooth‐like oscillations of the space potential. The effect of oscillations on the measured plasma parameters obtained with the aid of the single probe method, double probe method and the method of the second derivative of the probe characteristic is discussed, with the electron saturation current being taken into account. In the ion current the values rp/λD, λ/rp and Mi characterizing the working regime are varied. The calculated results are checked by corresponding measurements in a beam generated plasma.
Nonlinear Theory of the Instability of a Modulated Electron Beam of Low Density in a Plasma. V. Excitation of Waves in Strong Dissipative Plasmas by a Monoenergetic Beam
Authors: Kruscha K. J. G. , Kondratenko A. N. 
Published: July 2007

AbstractA system of nonlinear equations derived in a previous paper which describes the evolution of the beam‐plasma instability in strong dissipative plasmas is solved numerically. It is shown that there are three characteristic solutions of the system of equations: the resonant dissipative instability, the nonresonant instability with strong dissipation and the nonresonant dissipative instability. A physical interpretation of essential features of these instabilities is given. The interaction of resonant and nonresonant waves in the system electron beam‐strong dissipative plasma is examined. Some conclusions for the transport problem of electron beams in strong dissipative plasmas are obtained in this paper.
Distribution Radiale de la Densité des Atomes Métastables dans les Plasmas Produits par un Champ Electrique Continu ou de Haute‐Fréquence
Authors: Pantel R. , Ricard A. , Moisan M. 
Published: July 2007

AbstractOn a déterminé expérimentalement la distribution radiale de la densité des atomes métastables Ar(3P2) et résonnants Ar(1P1) dans deux types de décharges électriques de forme cylindrique: le plasma de la colonne positive d'une décharge en courant continu et le plasma produit par une onde étectromagnétique de surface. En comparant les distributions radiales de densité mesurées pour Ar(3P2) avec les distributions correspondantes calculées à partir du bilan radial création‐destruction de la population de ce niveau, on a pu obtenir les valeurs, en fonction de la position radiale, des coefficients de création et de destruction de ce niveau par collisions électroniques. Ces résultats sont obtenus pour diverses valeurs de la densité électronique sur l'axe. Les valeurs déjà, publiées de ces coefficients dans la colonne positive sont fondées sur l'hypothèse qu'ils ne dépendent pas du courant de la décharge, alors que l'on montre ici que leur valeur décroît en fait lorsque la densité électronique augmente. Ce travail montre de façon plus générale les possibilités considérables qu'offre l'examen de la distribution radiale de densité des atomes excités pour déterminer la cinétique de leur création et destruction.
Average Energy Variations and Trapping of Electrons in the Resonances of Rare Gases
Authors: De'Munari G. M. , Gabba L. , Giusiano F. , Mambriani G. 
Published: July 2007

AbstractThe effect of resonant elastic collisions of electrons in He on their “exact” mean energy variation for free path in the presence of a d.c. electric field is analysed.Different values of E/N and both isotropic and anisotropic initial velocity distributions, just after collision, are considered.It is shown that for sufficiently elevated values of E/N a necessary condition for electron (resonance) trapping becomes satisfied.This result is discussed in the light of an interpretative model advanced to explain some electroluminescence phenomena in rare gases.
Fluctuation‐Dissipation Rellations for Equilibrium and Non‐Equilibrium States. Kinetic Equations for Many‐Particle Distribution Functions
Authors: Klimontovich Yu. L. 
Published: July 2007

AbstractA kinetic formulation of fluctuation‐dissipation theorems (FDT) has been given.The transition to the thermodynamic version of the FDT has been discussed.Among the examples, a non‐equilibrium FDT, a FDT for chemically reacting systems and the interrelation to known kinetic equations has been discussed.
Geschwindigkeitsverteilungsfunktionen von Atomen und Ionen in verschiedenen Anregungs‐ und Ionisationsstufen in Niederdruck‐Entladungen bei hohem Ionisationsgrad
Authors: Valentini H.‐B. 
Published: July 2007

AbstractSupposing free‐fall conditions the velocity distribution functions of atoms and ions in various levels in gas discharges at low pressures are calculated. In particular, plasmas at high degrees of ionization are considered. Solving the Boltzmann equation for the motions transverse to the wall of the discharge tube it is shown that the velocity distribution functions can considerably deviate from the Maxwellian and become non‐isotropic. Inelastic collisions with electrons and the ionization by electron impacts considerably determine the velocity distribution function of the neutral atoms. The velocity distribution function of the ions is also essentially determined by the electric field within the plasma. For the motions transverse to the wall the half widths of the velocity distribution functions do not only depend on the temperature of the wall, but on the electron density and on the electron temperature as well. At small electron densities the half widths for excited atoms and for ions can be narrower than the one for the ground state atoms. The charge exchange between atoms and ions is shortly taken into consideration.
Power Reflection, Transmission and Absorption Coefficients for a Mobile Collisional Magneto Plasma Slab
Authors: Arora B. B. , Phalswal D. R. , Varma N. L. 
Published: July 2007

AbstractCoefficients of power reflection (R), transmission (T) and absorption (A) for a homogeneous, magnetised, collisional and moving plasma slab are derived and discussed by taking p‐polarized wave as the e.m. source wave and without imposing any restriction on the slab velocity. Effects of electron‐neutral collisions (νen), ion‐neutral collisions (νin) and the external magnetic field are included through momentum transfer equations. Plasma slab velocity (β = ν/c), electron ion densities (ωpe,i/ω) and the collision frequencies (νen,in) are found to cause significant change in the values of R, T and A, a numerical study of which is illustrated in the paper.
Experimental Investigations of Discharge Characteristics and Plasma Parameters of a Cylindrical Cathode Discharge in a Magnetic Field I Discharge Characteristics
Authors: Pavelescu G. , Bâlâceanu M. , Popovici C. 
Published: July 2007

AbstractThe experimental research on the correlation between the discharge parameters (electrode geometry, gas pressure, discharge voltage and current, magnetic field) of a cylindrical cathode discharge in magnetic field is presented. V‐I, I‐p und I‐B discharge characteristics are determined under various constructive and operating conditions. Invariant groups of discharge parameters for the discharges in the absence of the magnetic field are obtained. Experimental results are accounted for by a discharge mechanism wherein an important role is played by oscillating primary electrons.
Die Berechnung von Plasmaparametern aus Langmuir‐Sondencharakteristiken auf Digitalrechnern
Authors: Johanning D. , Lehmann H.‐R. , Seifert W. 
Published: July 2007

AbstractDie vorliegende Arbeit stellt eine Übersicht der physikalischen Probleme dar, die sich bei der Computer‐Auswertung von im Magnetosphärenplasma der Erde gemessenen Langmuir‐Sondencharakteristiken ergaben. Nach einer Abschätzung der Meßbereiche für die Temperatur‐ und Dichtebestimmung wird auf die Ableitung physikalischer Größen aus der Strom‐Spannungs‐Charakteristik unter den besonderen Bedingungen eines kosmischen Experiments eingegangen.Der zweite Teil der Arbeit ist der rechentechnischen Lösung der Aufgabenstellung gewidmet.
Needle Growth Induced by Corona Discharge
Authors: Okuyama F. 
Published: July 2007

AbstractIt is shown that the growth of a dense array of chromium microneedles is induced on a field cathode tip interacting with a negative corona discharge in ambient Cr(CO)6 of 1 – 5 × 10−2 Torr. The growth begins with the initiation of a corona discharge surrounding the tip, and it proceeds as long as the discharge is sustained. The needles emit field electrons during the growth, thereby sustaining the discharge, while the discharge lengthens the needles by supplying metallic particles to their tips. The morphological structure of the needles is strongly affected by an external magnetic field, leading us to hypothesize that the needle grow axially as the electron avalanches, originating at the cathode tip, propagate outward from tip.
Perturbed Arcs in Turbulent Axial Gas Flow IV. Thermal Reignition Experiments
Authors: Rothhardt L. , Michel G. 
Published: July 2007

AbstractBy means of the short‐circuiting of electric arcs burning in turbulent axial gas coolant flow and their reaction on a (recovering) voltage ramp the reignition in circuit breakers is modelled. Strong stochasticity of thermal reignition is demonstrated even under relatively weak conditions. Channels or nozzles showing flow detachment are further deteriorated by that. Corresponding low‐current test experiments are recommended for in‐scale circuit breaker development tests.
The Influence of Particles Interaction in Low‐Temperature Plasma on its Composition and Optical Properties
Authors: Sevastyanenko V. 
Published: July 2007

AbstractA model theory of the influence of particles interaction in plasma on its composition and optical properties is developed.The interaction of charged particles in plasma reduces the ionization energy of atoms and ions. The action of internal microfields in plasma on atoms and ions reduces the statistical weight of electron levels which affects the populations of excited states. The latter effect leads to an effective cutoff of partition functions and determines the behaviour of optical properties of plasma (of absorption coefficient and emissivity) at increased number densities of charged particles.The formulas are obtained for calculation of the continuous and discrete spectrum in plasma taking into account the particles interaction. A non‐monotonic dependence of optical plasma density upon number density of charged particles is quantitatively explained. A satisfactory agreement is obtained with a large number of experimental data some of which were considered to be contradictory.The method developed can be used for calculations in the field of atomic spectroscopy and low‐temperature plasma physics including increased densities of charged particles. The use of the formulas obtained in plasma diagnostics will enable one to avoid considerable errors.
Chaos in einem dissipativen Strahl‐Plasma‐System
Authors: Leven R. W. , Puttke R. 
Published: July 2007

AbstractA system of four ordinary differential equations is derived to describe the behaviour of an unstable beam‐plasma‐system. Numerical studies show regular as well as chaotic long time behaviour of the wave amplitude. To characterize the chaotic attractors found in the region of maximum growth rates the Poincaré maps and the greatest Lyapunov Characteristic Exponents were calculated.
Zur Diagnostik der Ionenkomponente im Plasma der äußeren positiven Säule einer stromstarken, unmagnetisierten Argon‐Hohlkatodenbogenentladung
Authors: Schielke W. , Schrade F. , Melior J. P. 
Published: July 2007

AbstractThis paper reviews two measuring methods of the ions and their results in low pressure plasmas, if spectroscopical methods are not applicable to this situation. The behaviour of ions in the positive column of a high current argon hollow cathode arc was studied in dependence of various plasma parameters with the help of a gridded probe and a quadrupole mass spectrometer. The obtained results were analysed with simple theoretical models and measured electron distribution functions.
Entwicklung leistungsfähiger Stickstofflaser mit abgeschmolzenem Laserrohr
Authors: Gündel H. , Ross W. , Seliger K. , Volkmann H. , Erbs H. , Harendt A. , Irmer J. , Schöpp H. 
Published: July 2007

AbstractFor an increase of the laser pulse energy from longitudinally excited multiple electrodes tubes, experiments and model calculations have been accomplished. A variation of the electrode spacing in the laser tube has shown, that a maximum pulse energy could be achieved with about 40 mm electrode spacing. If barium titanat capacitors with a dielectric constant of 10000 in the pulse forming unit were applied, a voltage pulse transform occured enabling an increase of the laser power up to 50%. With a sealed off operated laser tube of 100 cm active length, a laser peak power of 600 kW and a pulse duration of 10 ns could be achieved. A tube with 200 cm active length generated a pulse power of 1.2 MW. The decrease of laser pulse energy with increasing pulse repetition rate can be explained by the decrease of impulse breakdown voltage. For an increase of the lifetime of laser tubes, appropriate technologies for the production of the tube have been developed.
Sudden Jumps, Hysteresis, and Negative Resistance in an Argon Plasma Discharge. II. Discharges in Magnetic Fields
Authors: Bosch R. A. , Merlino R. L. 
Published: July 2007

AbstractExperimental observations on the behavior of low‐pressure, thermionic argon discharges in magnetic cusp and mirror configurations are presented. I–B characteristics showing jump and hysteresis behavior were found. In some cases, the sudden sharp decreases in discharge current that were observed were preceded by the onset of coherent, low‐frequency plasma oscillations, suggesting the possible role of instabilities.
Turbulence Driven Tearing Modes
Authors: Murtaza G. , Yu M. Y. , Shukla P. K. , Salahuddin M. 
Published: July 2007

AbstractThe effect of a turbulent background of density, electrostatic, and magnetic fluctuations on the growth of tearing modes is considered assuming three‐wave interaction. It is found that, depending on the background conditions, the turbulence can cause anomalous electron resistivity or viscosity, leading to enhanced growth rate.
Electrode Temperature in the Arc‐Discharge Zone Attachment
Authors: Zhukov M. F. , Pustogarov A. V. , Zavidei V. I. , Kucherov Ya. R. 
Published: July 2007

AbstractThe paper presents results of electrode‐surface temperature measurements in the arc‐discharge attachment zone. The investigations were carried out on tungsten electrodes in helium atmosphere and on zirconium electrodes in nitrogen atmosphere for currents within the range of 100…200 A.The contribution of plasma radiation to pyrometer readings has been determined. The real temperature of the tungsten electrode surface was measured using the polarised radiation at the wavelength λ = 0.65μ m.The energy distribution of arc‐spot radiation has been obtained for the spectral range of 0.4…1.2 μ m. The character of the arc‐spot radiation spectrum has been analysed.