bluuebunny/crossref_metadata_2025 huggingface dataset:
Electron Kinetic Investigations of the Glow Discharge Plasma in ArHg Mixtures
Authors: Winkler R. B. , Wilhelm J. , Winkler R.
Published: July 2007

In the theoretical description of mixture plasmas used in fluorescent lamps a Maxwellian energy distribution and a two‐electron‐group model has been applied to determine the transport quantities and the main collision rates of the electrons. For various parameters, especially for a wide range of the ionization degree we calculated the electron energy distribution function for the ArHg plasma from the Boltzmann equation taking into account all important elementary processes and the Coulomb interaction. Further, we made a self‐consistent determination of the ionization degree additionally applying the current balance. In this way the energy distribution function and resulting transport coefficients, collision and energy transfer rates of the electrons were calculated and a comparison with the above models was performed. An interesting finding was that they satisfactorily describe the low energy part of the energy distribution, whilst in the tail of the distribution there is a gradually underpopulation as compared to the models. Furthermore, calculated and experimental results are compared.
Device for Producing and Investigating an Electron Beam Plasma Discharge
Authors: Schmidt M. , Föste T. , Michel P. , Šapkin V. V.
Published: July 2007

A survey on the properties and applications of the beam plasma discharge is given. A device for the experimental investigation of this discharge is described in which a magnetically guided (H = 0.05−0.1 T), ribbonlike electron beam (eU = 0.5–5 KeV, I = 10−3−1 A) passes through a working chamber (p = 0.1–10 Pa; l = 10 cm, ø = 22 cm). The beam plasma discharge is sustained by collective beam plasma interaction. First results concerning the wall current and the ignition of the discharge as dependent on beam parameters are presented.
Energetische Eigenschaften eines 100‐kW‐Kaskaden‐Plasmatrons
Authors: Scheibe H.‐J. , Musikowski H. D.
Published: July 2007

Energetical properties of two different cascaded 100 kW‐H2‐plasma jets are treated. The losses of the heat are tested in dependence of the current. The influence of the geometrical place on the losses of heat in the plasma jet is shown. Questions of the adaption of the plasma jet to the power supply are discussed.
Electromotive Force and Dissipation in the Plasma‐Induced Arc
Authors: Ecker G. , Riemann K.‐U. , Wieckert Ch.
Published: July 2007

A joint treatment of cathode spot, main plasma and anode sheath of the plasma induced are is given which shows an additional electromotive force in the plasma and accounts for the upper limit of the electron temperature. The plasma‐emf may be substantially larger than that of the sheath. The reduction effect of the dissipation is comparatively small. As a result existence limitations for the electron temperature and the neutral density are given which are quite different from those derived simply from the floating potential.
Surface Wave Generation in a Solid State Plasma by Relativistic Electron Beams
Authors: Grishin V. K. , Kanevskii M. F.
Published: July 2007

The linear and nonlinear theory of the surface wave generation in solid‐state plasma by a relativistic electron beam propagating in a gaseous plasma is treated. The proposed scheme is in better agreement with the conditions of real experiment. Besides, the neutralization of beam charge is possible and the oscillation frequency and its stability increase, etc. A nonlinear analysis permits to obtain the estimation of efficiency of the beam interaction with the surface wave and a number of other characteristics of the system.
Plasma‐Beam Discharge with a Pipe‐like Electron Beam as the Generator of Large Flows of Active Radicals
Authors: Atamanov V. M. , Levadny G. B. , Ivanov A. A. , Nasedkin Y. F. , Sereda Y. V. , Serov A. A. , Timchenko N. N.
Published: July 2007

Investigations on the device with a tube‐like electron beam have been carried out. The behaviour of the plasma‐beam discharge in active molecular gases at low pressures and at the pressure P = 1 Torr has been studied. The etching of crystalline silicon by active fluorine radicals has been carried out.
Non‐Maxwellian Electron Velocity Distribution Resulting from Electron‐SF6 Attachment Collisions
Authors: Schmidt R. , Stiller W.
Published: July 2007

A model reaction system is considered consisting of a heat bath of argon atoms (c) and small concentrations of SF6‐molecules (m) and electrons (e) (number densities: ne ≪ nm ≪ nc). Within the model the time behaviour of the electron velocity distribution function is studied under the influence of elastic electron‐argon collisions and electron SF6 attachment collisions. On the basis of the distribution function time‐dependent macroscopic quantities (kinetic electron temperature. nonequilibrium rate constant of the attachment reaction) are calculated.
The Stability of the Relativistic Alfvén Waves
Authors: Ciubotariu C. D. , Zoler D. I. , Thirer N. S.
Published: July 2007

Within the framework of the special relativity, the system of reference comoving with Alfvén wave is defined and the form of the perturbations with respect to this system are deduced. The system of equations corresponding to the interaction of the waves, in the case when the relativistic Alfvén wave can generate new Alfvén waves and magnetosonic waves, is obtained in the most general form.

In the one‐dimensional case the time dependent perturbation method is used for obtain the dispersion equation for the relativistic coupled waves (decay processes). Finally, by solving numerically the dimensionless dispersion equation, the instability domains of the Alfvén waves are obtained. It is shown that there are possible decay processes and modulational instabilities.
Untersuchungen des turbulenten Strömungsfeldes eines schnellen eingeschlossenen Plasmastrahls
Authors: Hayess E.
Published: July 2007

Es werden radiale Temperatur‐ und Geschwindigkeitsverteilungen an einen eingeschlossenen turbulenten Plasmastrahl mit Thermoelement‐ und Drucksonden gemessen. Durch iterative Korrekturberechnungen werden neben den Temperatur‐ und Geschwindigkeitsfeldern auch die Felder verschiedener thermodynamischer Funktionen bestimmt. Das Verhalten des Plasmastrahls unterscheidet sich grundsätzlich nicht von den der Gasstrahlen und Flammen.

Infolge der Masseneintragung aus der Umgebung divergiert der Strahl und klingt sehr schnell ab.

Die aus Gründen der Massenerhaltung an der Behälterwand entlang verlaufende Rückströmung wird abgeschätzt. Sie ist so klein, daß sie mit den benutzten Meßmitteln nicht mehr nachgewiesen werden kann.
Zut Kinetik der plasmachemischen Methan‐Umsetzung in einer stillen elektrischen Entladung
Authors: Rutkowsky J. , Drost H. , Mach R.
Published: July 2007

In einer durch eine 50 Hz, 10 bzw. 20 kV‐Wechselspannung betriebenen stillen elektrischen Entladung vom Barrieren‐Typ wurde bei Drücken von 3,32–9,96 × 104 Pa Methan plasmachemisch in einfache Kohlenwasserstoffe umgesetzt. Als gasförmige Hauptprodukte wurden Äthan und Propan identifiziert, wogegen Buten, Azetylen, Äthylen und Propylen in deutlich niedrigeren Konzentrationen auftraten. Der Methan‐Zerfall in Abhängigkeit von der Entladungszeit entspricht bis zu 1000 s streng einer Exponentialfunktion. Die Bildung der Alkane, insbesondere des Äthans, verläuft nach dem Schema einer Folgereaktion; sie läßt sich kinetisch gut durch eine Geschwindigkeitsgleichung 1. Ordnung beschreiben.
On the Question of Increasing Maxwellization of the Electron Energy Distribution Function due to Electron — Electron Interaction with Growing Ionization Degree in the Beam Discharge Plasma
Authors: Winkler R. , Wilhelm J.
Published: July 2007

The question of the establishment of an almost complete Maxwellian energy distribution of the electrons in a given discharge plasma is of importance, especially under the aspect of a more convenient determination of transport and rate coefficients.

In [5] an energy space averaged criterion for the establishment of such a structure of the electron energy distribution function in the stationary beam discharge plasma of molecular gases was formulated from a heuristic point of view.

This paper investigates this question in detail starting from the adequate Boltzmann equation of such plasmas. Energy resolved conditions for the establishment of an almost complete Maxwellian distribution are derived from the kinetic equation. Using one of these conditions, the formal derivation of the mentioned averaged condition is performed and its limitations are shown. The fulfilment of the energy resolved and of the averaged conditions are illustrated and discussed using solutions of the kinetic equation in purely molecular hydrogen for two parameter sets yielding larger and smaller deviations of the real distribution function from the Maxwellian form.
Nonlinear Theory of the Instability of a Modulated Electron Beam of Low Density in a Plasma. II. Energetic Analysis of Certain Types of Monoenergetic Beam‐Plasma Interactions Based on the Čerenkov Resonance Condition
Authors: Kruscha K. J. G. , Kondratenko A. N.
Published: July 2007

The energy and momentum balance equations for a potential wave in a monoenergetic electron beam‐plasma system are considered in the linear approximation, when the wave is in Čerenkov resonance with the beam particles. An energetic analysis of certain types of beam‐plasma instabilities is given. It is shown that the energy and momentum balance equations are consistent with the dispersion relation for all unstable waves. From this fact follows that the energy and momentum densities of all linear unstable waves in reactive beam‐plasma systems are equal to zero. An interpretation and a possible classification of beam‐plasma instabilities are given.
Temperature Effects on the Beat Heating of a Collisional Magnetoplasma
Authors: Arora B. B. , Phalswal D. R. , Varma N. L.
Published: July 2007

The beat heating of a magneto‐plasma by two antiparallel electromagnetic waves at different temperatures is examined. The effects of plasma temperature, plasma electron collisions, plasma ion collisions and magnitude and direction of the magnetic field on the excitation of plasma electron waves and plasma ion waves are studied. A formula for the power absorption density of the plasma by using Maxwell's equations in conjuction with continuity and momentum equation. including collisions and pressure tensor terms, is derived. The contribution of the plasma temperature to the power absorption density, both at low and high beat frequencies, of the collisional and the non‐collisional magnetised plasmas is found very significant and is illustrated numerically. The inclusion of pressure tensor term in the momentum equation is also found to cause characteristic changes in the power absorption density of the plasma with the orientation of magnetic field.
Formation of Discharges between Glass Insulated Electrodes in Ne + 1% N2 Mixtures. II. Frequency Dependence and Discharge Modes
Authors: Lange H. , Stern W.
Published: July 2007

Discharges between glazed electrodes for p = 2.67 kPa Ne + 1% N2 and pd = 1.3 kPa cm (p = gas pressure, d = electrode distance) are investigated. They are sustained by a sine wave voltage of variable frequency f. Measurements of the space time structure of the radiation emission provide information of the build up and quenching of discharges and of the structure of the fully developed ac‐discharge.

It is shown that the discharge types for the different values of frequency and amplitude of the sine wave sustaining voltage are dynamically developed Townsend and glow discharges. For f ≦ 4 kHz the optical structure and its temporal behaviour largely depends on the increment of the sustaining voltage. For f ≧ 20 kHz the axial structure of radiation emission is modified by the influence of consecutive discharges due to residual ions (f ≌ 20 kHz) and metastable Ne(3P2)‐atoms (f > 20 kHz) existing for several periods of sine wave. The Penning effect of metastable Ne‐atoms with N2 molecules then produces start electrons for each discharge in a sequence which improve the initial conditions for the breakdown. Relations between space time structure and breakdown voltage as a function of frequency f are discussed.
On the Anomaly of the Electrical Field Strength in the Magnetized Positive Column of Glow Discharges at Small Currents
Authors: Deutsch H. , Klagge S.
Published: July 2007

The axial electrical field strength in the positive column of glow discharges at small currents in noble gases passes through a maximum with the increase of an axially directed magnetic field. This maximum is explained of the contrary processes of extension of the radial profiles of the electron energy and the concentration of the metastable atoms on the one hand and the decrease of the ambipolar diffusion losses on the other hand. Using the results of measurements of metastable atom concentrations, the electrical field strength is calculated as a function of magnetical induction with the aid of a set of balance equations. The radial and axial distribution of the electrons is checked by probe measurements. The methods for measuring the concentration of the excited atoms and the electrons are described.
Coronal and Collisional — Radiative Model of the Plasma for the Case of Hydrogen Glow Discharge
Authors: Ferdinand J. , Vlček J. , Čejková E.
Published: July 2007

In this paper the comparison of coronal and collisional‐radiative models of the plasma of the positive column of hydrogen glow discharge is made. From the good agreement between theoretical and experimental results it follows that both models are suitable for description of the two spectral lines intensities ratio dependence on electron temperature.
General Form for the Electron Distribution Function for an Inhomogeneous Fully Ionized and Magnetized Plasma Interacting with an Alternating Electric Field
Authors: Burdujan I. , Zoler D.
Published: July 2007

It is the purpose of this paper to give a general form for the isotropic and vectorial part of the distribution function for electrons, in a fully ionized and magnetized plasma, interacting with an alternating electric field.

By making the assumption, that the ions have an equilibrium distribution, we obtain the needed solutions as series with respect to time and complex exponentials. Also have indicated a new manner in which the solution may be obtained with any precission we want. A general form for density current is obtained. It should be denoted that these results are obtained, without being done any previous assumption on the temporal dependence of the distribution function.
The Knudsen Ion Layer Problem in the Theory of the Collisionless Sheath
Authors: Chekmarev I. B. , Sklyaroba E. M. , Kolesnikova E. N.
Published: July 2007

The interaction of a partially ionized continuum gas with a negatively charged electrode is investigated theoretically. It is supposed that ld ≪ 1, where ld is the Debye length, l is the mean‐free‐path. The self‐consistent solution is given for two cases: lI ≫ l and lI ∼ l, lI is the effective ionisation length. The matched asymptotic expansions method is used. The Bohm sheath criterion is shown to be satisfied automatically in the considered cases.
Application of the Inverse Matrix Pearce Method to Plasma Spectroscopy
Authors: Sato M.
Published: July 2007

The inverse matrix method is a variation of the Pearce method for numerically solving the Abel integral equation in plasma spectroscopy. Differed from the original method, the matrix method allows a direct determination of radial intensity profiles without iterative calculation from the zone of the plasma edge. From the tests through numerical simulations, it is found that this method has the higher accuracy than the original method by reducing the errors caused by iterative calculations. Since no smoothing procedure is included, the matrix method is vulnerable to receive the effects of random scattering. However, when appropriate smoothing is made, this method becomes as useful as the other methods. The Nestor‐Olsen and Barr methods are also tested for comparison.
Electrodynamic Model of Initiation and Extinction of Emitting Sites Interacting Together in Cold Cathode Spots (Type A) in Air
Authors: Liegmann K.
Published: July 2007

From an electrodynamic and simple quantum‐mechanical point of view a model is proposed which explains the phenomena of minimum arc current as well as the formation and extinction of tiny emitting sites interacting together in cold cathode spots (called type A) on the base of a specific coupling between the tunnelling “average” electrons and the metal bulk phonon field. The model seems to be especially applicable to such experimental conditions where typical trumpetlike microcraters with pronounced rims with diameters in the range 0.5—1 μm are left by microspot ensembles on the cathode surface.

The model yields emitting‐site lifetimes, currents, current densities and radii in the order of τps ⋍ \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt {3M/m} $\end{document} τ0 ⋍ 10−11 sec, Imin = 4π ℏ \documentclass{article}\pagestyle{empty}\begin{document}$ \sqrt {n/\mu _0 m} $\end{document}⋍ 0.4 A, j = nevs ⋍ 4 · 1013 A/m2 and ra ⋍ 2c/ωPl ⋍ 30 nm (τps…lifetime of short wave phonons, M … atom mass, m … electron mass, τ0 … mean free collision time of Fermi electrons at room temperature, n … conduction electron density in the metal bulk, vs … metal bulk sound velocity, c … light velocity, ωPl … metal bulk plasma frequency (values for copper). The lifetime and the interaction diameter of an emitting site (event) ensemble are derived to τpl ⋍(M/m) τp ⋍ 3 nsec and Λpl = νsτpl ⋍ 10 μ (τpΛpl … lifetime and mean free path of long wave phonons).
Generalized Boundary Conditions in an Existence and Uniqueness Proof for the Solution of the Non‐Stationary Electron Boltzmann Equation by Means of Operator‐Semigroups
Authors: Bartolomäus G. , Wilhelm J.
Published: July 2007

Recently, based on the semigroup approach a new proof was presented of the existence of a unique solution of the non‐stationary Boltzmann equation for the electron component of a collision dominated plasma. The proof underlies some restrictions which should be overcome to extend the validity range to other problems of physical interest. One of the restrictions is the boundary condition applied. The choice of the boundary condition is essential for the proof because it determines the range of definition of the infinitesimal generator and thus the operator semigroup itself. The paper proves the existence of a unique solution for generalized boundary conditions, this solution takes non‐negative values, which is necessary for a distribution function from the physical point of view.
Excitation of Plasma Waves by Means of a Weakly Ionized Monoenergetic Particle Beam
Authors: Kondratenko A. N. , Kruscha J. , Kuklin V. M. , Tkachenko V. I. , Vorobjov V. M.
Published: July 2007

The instability of a weakly ionized monoenergetic particle beam in a plasma is investigated by means of the weak cold beam description. Such an instability is characterized not only by a collective interaction of the beam electrons with the plasma electrons via the unstable waves but also by collisions of the beam electrons with the neutral beam particles.

The considered instability is characterized by a strong velocity focusing and intensive bunching of the beam electrons. An essential enlargement of the maximum wave amplitude relative to the resonant reactive instability [1] was observed.
The Measurement of Current Column Plasma Parameters in the Glow Discharge at Increased Pressure
Authors: Akishev Yu. S. , Napartovich A. P. , Pashkin S. V. , Trushkin N. I.
Published: July 2007

Results of the probe and thermocouple measurements of the constricted stationary glow dis charge in nitrogen and air at pressures up to 60 Torr are given. It was shown that the main energy processes in the column are the heating of the gas and its vibrational excitation. The balance of charged particles is determined by the electron‐ion recombination and the stepwise ionization through metastable levels of nitrogen molecules. The results obtained can be used in the numerical simulation of a moving filament during the current constriction in the glow discharge.
Das Abklingen des Plasmas der Impulslaser‐Gasentladung in Stickstoff
Authors: Wojaczek K.
Published: July 2007

For a typical laser gas discharge, the concentration and temperature of the most important plasma components at the end of the current pulse are calculated on the basis of given data for the tube radius, gas pressure, and energy input. Relating to a postdischarge time up to 1 s, the deionization, the association of the nitrogen atoms, the deexcitation of metastable molecules and the relaxation of the vibration temperature are investigated by means of simple balance equations. Finally the influence of plasma relicts on the following discharge pulse is discussed.
On the Theory of Ion‐Cyclotron Instabilities in Collisional Rotating Plasma
Authors: Kurko O. V. , Mikhailovskii A. B.
Published: July 2007

The role of collisions in the ion‐cyclotron instabilities in the rotating plasma has been investigated. Collisional varieties of such instabilities at moderate collisions have been shown possible. At frequent enough collisions the total stabilization of such instabilities takes place. A survey of the contemporary state of the problem of the ion‐cyclotron instabilities in rotating plasma has been given.
Der zeitliche Verlauf einer Elektronenstrahl‐gesteuerten Hochdruckentladung in CO2‐Lasergasgemischen
Authors: Albrecht H. , Gündel H. , Seliger K.
Published: July 2007

The energy which may be introduced into the plasma of an e‐beam sustained laser discharge depends on the electron loss processes as recombination and attachment. Measuring the time behaviour of the discharge current both the recombination and the attachment rate coefficients can be determined.

The results of such investigations reported here suggest that some widely used assumptions have to be proofed carefully once more. It could be shown that in the case of pure nitrogen the recombination coefficient decreases very rapidly immediately after the discharge ignition even if the reduced electric field strength remains unchanged. In CO2‐discharges such a behaviour could not be observed. Moreover, it has been found that CO2‐discharges are stable only as long as they are recombination determined.

These results are supported by additional investigations in N2—CO2‐mixtures. Some conclusions according to the operation of tunable high pressure lasers are given.
Complex Calculations of High‐Pressure Discharge Irradiation Characteristics
Authors: Sinyarev G. B. , Gradov V. M.
Published: July 2007

A wide range of problems related to the determination of the high‐pressure irradiation parameters in inert gases and vapors of metals is considered. A new method for calculating equilibrium states of the computed thermodynamic systems is described and its applications to the determination of the plasma composition are disclosed.

The method for computing basic discharge characteristics including the determination of material functions of the plasma producing media along with the optical absorption factors' a temperature field in a discharge stabilized by a quartz shell with regard to irradiation energy transfer carried out by bright‐line and continous spectra, spectral distributions for the radiant fluxes and discharge irradiation efficiency is presented.

Results of multiple calculations to obtain said characteristics in krypton, xenon, vapors of sodium, potassium, rubidium and their mixtures with inert gases are given. Calculated data is a satisfactory agreement with the results of experiments published by various authors.
Plasma Oscillations and Their Influence on Certain Properties of Nonideal Plasma
Authors: Kurilenkov Yu. K. , Valuev A. A.
Published: July 2007

The hypothesis is proposed that Langmuir plasma oscillations can exist in nonideal plasma inspite of great collisional frequency. This possibility is confirmed by numerical estimations and the results of several experiments. The influence of plasma oscillations on electron states density and conductivity of nonideal plasma is considered. The simple formula obtained for conductivity agrees well with available experimental data.
On the Nonlinear Theory of Surface Wave Excitation in a Collisional Solid State Plasma
Authors: Grishin V. K. , Kanevskii M. F. , Ivanov S. T.
Published: July 2007

The nonlinear equations governing relativistic electron beam‐surface wave dynamics in dissipative P‐S‐plasma are derived. The influence of P‐plasma on time saturation, amplitude of the wave at saturation and damping factor is analyzed. The obtained results are discussed from the physical point of view.
Propagation and Diagnostic of Ion Acoustic Waves in a Low Pressure Argon Discharge
Authors: Sato M. , Wagatsuma Y. , Sato T.
Published: July 2007

In a dc argon discharge column of pressure 5 × 10−4 torr, ion acoustic waves are studied experimentally. Plasma parameters obtained from the phase velocity of waves are compared with the Langmuir probe measurements. The wave diagnostic method yields the electron temperature lower than the probe method by a factor of 3…︁5, if the atomic argon ion is assumed as a dominant ion species. The axial profiles of ion drift velocity show the presence of ions flowing toward the anode along the potential drop in flont of it. Also it is found that the surface condition of the cathode sensitively affects the propagation of ion acoustic waves through the changes in discharge parameters.
Studies on the Decomposition of Carbon Dioxide in a Low‐Temperature Plasma
Authors: Szymański A. , Huczko A.
Published: July 2007

The decomposition of carbon dioxide was studied in an argon plasma jet, generated by a direct‐current arc discharge. The decomposition degree of carbon dioxide was up to 0,4 at an effective energy consumption lower than 1 MJ/mole CO. The efficiency of high‐temperature decomposition of carbon dioxide to carbon monoxide and oxygen is essentially dependent both on the quenching intensity of the products, which prevents from the reverse oxidation reaction in the system, as well as on the proper conditions of plasma‐substrate mixing.
Zur plasmachemischen Umsetzung von GaAs mit CCl4 und CF2Cl2 in Gegenwart von Sauerstoff
Authors: Prösch U. , Buttke K.
Published: July 2007

Es wurde der plasmachemische Abtrag von GaAs durch CCl4 und CF2Cl2 bei unterschiedlichen Leistungen eines 27,3 MHz Generators und unter Zusatz von Sauerstoff gemessen. Zur Interpretation der erhaltenen Ergebnisse wird ein einfaches kinetisches Modell vorgeschlagen.
Inclusion of the Full Electromagnetic Interaction in Correlations and Physical Quantities
Authors: Lambert A. J. D. , Schram P. P. J. M.
Published: July 2007

Density‐density correlations in a homogeneous, isotropic, classical plasma are calculated with inclusion of the full electromagnetic interaction. This leads to isotropic homogeneous field limits, contrary to the electrostatic approximation, that is consequently not valid for small wavenumbers. Application of the theory of generalized functions, combined with Kramer Kronig relations makes it possible to deal with the integrals that occur in the transverse part, provided a nonrelativistic approximation has been applied. As a side result Kubo's formula, applied to the electric conductivity, and generally derived under restriction to the electrostatic approximation, reappears for the case that the full electromagnetic interaction is included.
Resonant Wave‐Particle Interaction in an Explosively Unstable Beam‐Plasma System II. Investigation of the Relaxation Behaviour of the Electron Beam
Authors: Kruscha K. J. G. , Leven R. W.
Published: July 2007

Three typical saturation mechanisms of the explosive instability (EI) in a beam‐plasma system are investigated. It is shown that the maximum values of the electric field strengths of the explosively unstable plasma waves can be of the same order as the maximum wave amplitude of the linearly unstable waves. Some conclusions with regard to the role played by the EI in the evolution of a real beam‐plasma system are presented. The relaxation of a strongly modulated electron beam by the explosive wave coupling mechanism is examined in an appendix. A qualitative interpretation of the diversity of the EI saturation mechanisms found in this investigation is given.
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Published: July 2007

Using the drift kinetic equation the influence of the ballooning component of the perturbed transit ion pressure on the low‐frequency Alfvéen waves in a toroidal plasma is considered. It is shown that this contribution to the plasma pressure leads in a relatively cold plasma (plasma edge) to a stabilization of the Alfvéen modes. Taking into account drift effects the modified Alfvéen wave becomes unstable if the temperature gradient is large enough. All the perturbations are strongly localized around the corresponding rational magnetic surface.
Nonlinear Interaction of S‐Polarized Incident Radiation and Surface Waves in Magnetoactive Plasma
Authors: El‐Seragy N. M. , Khalil Sh. M. , Sayed Y. A. , El‐Sherif R. N.
Published: July 2007

The effect of an external magnetic field on the nonlinear interaction of S‐polarized electromagnetic radiation incident on a S‐polarized surface wave in a plasma layer was studied analytically. We have calculated the amplitudes of generated waves at combination frequencies. The generated waves are of P‐polarization and can be either electromagnetic or surface waves, depending on the signal of the value=\documentclass{article}\pagestyle{empty}\begin{document}$ ^{\chi '^2 = \frac{{k'^2 }}{{\varepsilon '}} - \frac{{\omega '^2 }}{{c^2 }} + k'\frac{\partial }{{\partial x}}\frac{{\varepsilon '_2 }}{{\varepsilon '\varepsilon '_1 }}} $\end{document}.
Electronic Heat Conductivity of a Partially Ionized Hydrogen Plasma
Authors: Schlanges M. , Kremp D. , Kraeft W. D.
Published: July 2007

The electronic contribution of the translational heat conductivity of a partially ionized hydrogen plasma is determined, starting from a quantum kinetic equation, which takes into account the two particle scattering between the free charge carriers as well as electron‐atom collisions. Plasma effects are included by statically screened potentials. In connection with a mass action law, the influence of the different collision terms on the electron heat conductivity is shown. An estimation is given for the contribution of the atoms. The pressure ionization (Mott effect) is described by a minimum behaviour of the heat conductivity.
Distribution of Excited Atoms and Ions in a Plasma Generated at the Surface of Ferroelectric Ceramic
Authors: Janus H. , Kusz J. , Musielok J.
Published: July 2007

The distribution of excited atoms and ions in a plasma generated at the surface of ferroelectric ceramic has been studied. For all studied spectral lines of He I, Ar I, Ar II and hydrogen a decrease of the total line intensity with the increasing distance from the ceramic surface has been found. The shapes of these distributions are characteristic of the specific spectral lines. The distributions for He I lines depend strong on the concentration of argon in the helium — argon mixture. The effect of overpopulation of some excited Ar II ion levels in an argon discharge observed already in a previous work has been found also in the case of a helium — argon plasma.
The Theory of Ionization Waves in the Contracted Discharge of Noble Gases
Authors: Golubovski Ju. B. , Nekuchajev V. O.
Published: July 2007

Positive column plasma in noble gases at middle pressures is analysed for stability in the frames of the linear hydrodynamic theory. At critical values of pressure and current the discharge becomes unstable to radial contraction (contraction) and to wave disturbances of the type of current pinch constrictions (contraction ionization waves). Ionization waves in the contracted discharge are three‐dimensional formations with electron concentration oscillations on the axis in the opposite phase with current pinch cross section. The discharge diffuse‐recombination theory was used for analysing the problem of instability arising.
Selection of the Time Parameters of Oscillating Impulse Voltages for On‐Site Testing of Gas Insulated Switchgears (GIS)
Authors: Hauschild W. , Schader W. , Mosch W. , Petzold K.
Published: July 2007

GIS for operation voltages ≧ 245 kV can be tested with oscillating impulse voltages on site advantageously, because this H. V. test can be performed with easily mountable impulse generators. The IEC recommendation for on‐site testing of GIS which is now under discussion doesn't fix the time parameters of the oscillating impulse voltages, but these influence the breakdown behaviour of slightly non‐uniform fields with disturbances (sharpe edges, fixed or free‐moving particles) in SF2.

For the mentioned GIS (≧ 245 kV) fixed disturbances are more dangerous than free‐moving particles. Therefore the breakdown voltages of model insulations with a disturbance at the H.V. electrode (needle with length l=0…5 mm) in SF6 (p20=0.1…0.4 MPa) were investigated at oscillating lightning (OLI) and oscillating switching (OSI) impulse voltages with different times to crest.

From the results, which were compared with those at aperiodic lightning (LI) or switching (SI) impulse voltages, permissible time parameters for OLI and OSI can be derived. On the basis of these parameters an impulse generator was designed which enables on‐site testing for a wide range of the capacity of the tested GIS.
An Introduction to Quark—Gluon Plasmas
Authors: Wallis G.
Published: July 2007

It is tried to present the main features of quark‐gluon plasma physics to a possible reader not so familiar with quantum chromodynamics and its extension to high temperatures, merely by looking for some analogies to usual electrodynamic plasma phenomena: The electrons correspond to the quarks, the photons to the gluons, the electromagnetic coupling to the strong coupling. However, in contrast to the ionization processes or, more general, generation processes of electrically charged particles or holes, the change from the usual hadronized state of nuclear matter to the collective quark‐gluon plasma state is a first‐order phase transition. The possible existence of such quark matter in the cores of massive neutron stars, at ultrarelativistic heavy‐ion collisions and in the early state of the Universe are discussed in a verbal approximation.
The Formation of Dissipative Structures and Chaotic Beam Relaxation in the Strongly Dissipative Beam‐Plasma Instability
Authors: Kruscha K. J. G. , Leven R. W.
Published: July 2007

Numerical solutions of a nonlinear system of equations describing the evolution of the strongly dissipative beam‐plasma instability are presented (time or space dependence of the unstable waves, the evolution of the beam distribution function and the corresponding phase space representations are given). Such an instability establishes if the linear growth rate of the unstable waves is small in comparison to the effective collision frequency of the electrons of the dissipative plasma. It is shown that after saturation of the instability there is an efficient energy transfer from the directed motion of the beam electrons to the thermal motion of the plasma electrons. Arguments are given that the strongly dissipative beam‐plasma instability is possibly the basic plasma heating mechanism which operates in the quasi‐stationary state of the beam plasma discharge. Self‐consistent initial conditions are used for the numerical calculations. Formation and evolution of dissipative structures (vortex structure, chaotic structure) were observed. A profound investigation of the chaotic or turbulent beam relaxation mechanism is presented. Such a relaxation mechanism develops in the case of the nonresonant dissipative instability (e.g. in resistive wall‐electron beam amplifiers). The method of investigation of dissipative structures presented in this paper (application of Shannon's information theory and results of the theory of dynamical systems with chaotic behaviour) can be extended to studies of other beam‐plasma systems within the framework of partial kinetic description.
High‐Frequency Electrical Conductivity and Dielectric Function of Strongly Coupled Plasmas
Authors: Meyer T. , Tkachenko I. M.
Published: July 2007

Using the frequency‐moments analysis of the electrical conductivity with quantum mechanical assumptions and with the help of sum rules a generalization of the Drude‐Lorentz theory of the electrical conductivity is given. For Coulomb‐systems (e.g. plasmas), a connection is formulated in this framework between the known static electrical conductivity and the high‐frequency conductivity. In this way, we are able to give an expression of the high‐frequency dielectric function.
Negative Ions in a Glow Discharge of Tetrafluoromethane
Authors: Meichsner J. , Poll H. U. , Wickleder K. H.
Published: July 2007

The Langmuir — probe measurements in a CF4— glow discharge reveal a large number of negative ions (1010cm−3) in the plasma between the planar C‐electrodes. Under special conditions the density of them exceeds the electron density at several orders of magnitude and sustains a quasi — electron free plasma. The ratio depends on the residence time of the molecular gas in the discharge reactor. It is due to dissociative electron attachment to highly molecular gas components arising from the plasmachemical conversion of CF4. F−and CF3−are the most important negative ions.
The Mathematical Modelling of the Switching Arc
Authors: Bergmann V. , Grams B. , Rother W.
Published: July 2007

For developing and optimizing of high‐voltage SF6‐puffer breaker a mathematical model of the switching arc is an important tool for the manufacturer. A physico‐mathematical model was build up to simulate the behaviour of the switching arc near current zero. To proof the model the influence of steepness of current and voltage, of the gas pressure and the position of the upstream electrode on the breaking capacity have been calculated. First work has been done to use the model to simulate the dielectric behaviour too. To minimize computer time and to get more informations on the integral model the characteristic functions have been calculated with the pm‐model. The result shows the influence of the steepness of the current before current zero.
Model of Non‐Laminar Low‐Temperature Plasma Flow with Intensive Self‐Mixing
Authors: Burnat M. , Kurowski S. , Penczek M. , Wierzbicki J.
Published: July 2007

A new model of turbulence is presented. It consists in treating the turbulence as an essentially self‐mixing process. The mass, momentum and energy transport is assumed to proceed along interlacing curvilinear cones. A relevant mixing field is introduced. It consists in relating to each point of space an infinite set of instantaneous velocities momentums and energies.

Into each transport equation a self‐mixing term of the proper form is introduced. The closure procedures for modyfied transport equations are also discussed.
Suspended Particles and the Gravitational Instability of Rotating Magnetised Medium
Authors: Chhajlani R. K. , Sanghvi R. K.
Published: July 2007

The effect of uniform rotation on the self gravitational instability of an infinite homogeneous magnetised gas particle medium in the presence of suspended particles is investigated. The equations of the problem are linearized and the general dispersion relation for such system is obtained. The rotation is assumed along two different directions and separate dispersion relation for each case is obtained. The dispersion relation for propagation parallel and perpendicular to the uniform magnetic field along with rotation is derived. The effect of suspended particles on the different modes of propagation is investigated. It is found that in presence of suspended particles, magnetic field, rotation and viscosity, Jeans' criterion determines the condition of gravitational instability of gas‐particle medium.
Elastic Scattering of Electrons by a Cut‐Off Coulomb Potential at Low Energies
Authors: Mihajlov A. A. , Djordjević D. , Vučić S. , Kraeft W. D. , Luft M.
Published: July 2007

Elastic scattering of electrons by cut‐off Coulomb potential Uc(r) is investigated, where Uc(r) = 0, for r > rc and Uc(r) = −1/r + 1/rc for r ≦ rc. This is first considered in terms of classical, and later quantum mechanical (partial wave) methods in the low energy range 0 ≦ ϵ ≲ 1/rc, where ϵ is the energy of the free electron. Scattering in this energy region displays a number of particular characteristics, such as back scattering, at certain energies. It can be concluded that some agreement does exist between the classical and quantum mechanical results.
Instationary Electric Fields, Ion Transport and Strong Density Fluctuations in Tokamaks with Dominant Anomalous Electron Transport
Authors: Wolschke S.
Published: July 2007

A common explanation is given for ion transport and strong broadband density fluctuations in tokamaks as a result of large anomalous electron transport near dominant magnetic surfaces (resp. in small magnetic islands). The main mechanism is local density flattening connected with an anomalous electron transport induced instationary radial electric field, which forces the ions via polarization drift to follow the electrons. For the density flattening process an exact solution of the time‐dependent diffusion equation for a linear initial profile over the island width is used. From this we also derive an expression for a temporal growing radial electric field. This positive field reaches its maximum at the density plateau. Strong viscous diffusion or instability‐induced transport between high and low electric field regions may now reverse the density flattening. Therefore relaxation oscillations result which may also explain the observed strong density and potential fluctuations in tokamaks. Several details of recent measurements of impurity ion behaviour and density fluctuations in tokamaks may be better explained with the theory given here.
A Pair of Zakharov Equations with Collisional Damping and the Motion of Langmuir Soliton
Authors: Bhakta J. C.
Published: July 2007

The effects of collisional damping on high frequency Langmuir wave and low frequency ion‐acoustic wave have been investigated. It is found that the governing equations for the waves are a pair of Zakharov equations with a damping term in each equation. By using the treatment which consists of approximate solutions of the balance equations, a set of first order ordinary differential equations have been derived for the solution parameters in order to study the motion of Zakharov solitons in presence of damping. It has been shown that the width of the soliton remains constant throughout the motion.
Plasma Maser Theory of Whistler Waves in the Presence of Ion Cyclotron Turbulence
Authors: Khound R. N. , Sarma S. N. , Bujarbarua S.
Published: July 2007

In this paper we consider the plasma maser theory of whistler waves in the presence of ion cyclotron waves in a magnetized plasma. In a plasma with low frequency ion cyclotron turbulence and a high frequency test whistler wave, growth of the whistler wave takes place because of the turbulent bremsstrahlung interaction between the resonant electrons and the modulated electric fields. The growth rate of the whistler wave is calculated and the results discussed.
Gravitational Instability of a Rotating Viscous Finitely Conducting Plasma
Authors: Bhatia P. K. , Maheshwari S. L.
Published: July 2007

The gravitational instability of infinite homogeneous plasma has been studied to include simultaneously the effects of rotations, Hall currents, viscosity, finite electrical conductivity and the finite Larmor radius (FLR). Both the longitudinal, and transverse modes of wave propagation have been studied. It is found that the gravitational instability is determined by Jeans' criterion even in the presence of effects of rotation, Hall currents, FLR, viscosity and finite conductivity whether included separately or jointly.
Effect of Conductivity on Magneto‐Gravitational Instability of a Medium with Finite Larmor Radius and Suspended Particles
Authors: Chhajlani R. K. , Bariwal R. L.
Published: July 2007

The self‐gravitational instability of an infinite homogeneous magnetised and finitely conducting gas‐particle medium is considered to include the finite Larmor radius effect in the presence of suspended particles. The equations of the problem are linearized and from linearized equations a general dispersion relation for dusty‐gas is obtained. The dispersion relations are also obtained for propagation, parallel and perpendicular to the direction of uniform magnetic field. The Jeans, criterion is discussed for these two different directions of wave propagation. It is found that in the presence of finite Larmor radius corrections and suspended particles the condition of instability is determined by Jeans' criterion for a self gravitating, finitely conducting, magnetized gas‐particle medium.
On the Interaction of an Alternating Electrical Field with an Inhomogeneous Magnetized Plasma
Authors: Zoler D. , Burdujan I.
Published: July 2007

It is found out the form of the vectorial and isotropic cartesian component for the distribution function for electrons in an inhomogeneous plasma interacting with an alternative electric field, without being done any previous supposition on the temporal dependence of these quantities. For this purpose it is applied a method of succesive approximations for solving an integro‐differential equation for the isotropic component of the distribution function. The scalar and vector components of the plasma spherical harmonic expansion are calculated including transient and secular terms.

Some particular quantities as time‐independent part of vectorial component of distribution function and of nonlinear conductivity were also obtained. Also corrected expressions for the transport coefficients in a electrical field, are obtained.
Effect of the State of the Cathode Surface on its Photoemission Properties
Authors: Fomin N. A. , Samtsov P. P. , Soloukhin R. I.
Published: July 2007

The results of experimental investigation of the effect of the state of the cathode surface on its photoemission properties are presented. It is found that the low‐pressure glow discharge treatment of the copper cathode surface in the air results both in a substantial shift of the photoeffect threshold to the long‐wave region of a spectrum and in a change of the quantum photoemission yield.
Electrical and Spectral Characteristics of a Heated Cathode Discharge in Metal Vapors
Authors: Musa G. , Baltog A. , Popescu A. , Betiu N. , Mustata I.
Published: July 2007

A new type of discharge in pure metal vapors like copper or titanium is described. A stable discharge is produced between a heated cathode and the anode which has a melted spot on its surface due to the electron bombardment. The spectral characteristics prove that the discharge take place in the vapors of the anode material continuously evaporated from the melted spot on the anode. The discharge has a similar behaviour as the low voltage arc.
Experimental Study of Non‐Equilibrium Ionization in a Supersonic CO Flow
Authors: Blaha J. , Labuda S. A. , Maštovský J. , Rothhardt L.
Published: July 2007

Experimental results are presented on ionization processes in the vibrationally non‐equilibrium flow of CO preliminarily heated by a shock wave and adiabatically cooled in the supersonic nozzle with a flow Mach number of M = 3.9.

It is shown that for a wide range of flow stagnation temperatures, the value of the recorded semi‐self‐maintained current considerably exceeds the one due to thermal gas ionization in the plenum chamber.