bluuebunny/crossref_metadata_2025 huggingface dataset:
Diffusionstheoretische Beschreibung der Dissoziation und des Ionenhaushaltes im schwachionisierten Säulenplasma der Wasserstoffentladung. II. Makroskopische Kenngrößen der Elektronen im H/H2‐Mischplasma
Authors: Michel P. , Pfau S. , Rutscher A. , Winkler R.
Published: July 2007

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 Calculations of the Concentrations, of the Radial Distributions, and of the Radial Particle Currents of Excited and of Doubly Charged Ions in Low Pressure Discharges
Authors: Valentini H.‐B.
Published: July 2007

A system of differential equations describing the radial profiles of the number densities and of the radial drift velocities of the ions and of the electrons in positive columns at low pressure containing several species of ions is derived. Excited ions and doubly charged ions, generated in two‐step processes by electron impacts, the inertia of the ions and space charge effects are taken into account. For the excited ions de‐excitation processes by electron collisions and by spontaneous emission are regarded. A set of nonlinear equations to determine the population densities and the initial values of the differential equations and corresponding boundary conditions are put up. Numerical solutions are given for discharges in argon under free‐fall conditions similiar to argon ion lasers. One notices that without stepwise processes via excited ion levels the concentration of double charged ions remains small. In some cases the radial drift of the ions considerably reduces the population of the metastable ion levels. The radial density profiles of the double charged ions and of long‐living excited ions considerably deviate from the squared radial profile of the electron density. In addition, for low degrees of ionization the theory of the free‐fall column given by Tonks and Langmuir is extended to plasmas containing two species of ions.
Reaktionskinetik der Ozonbildung in der Sauerstoffglimmentladung
Authors: Sabadil H. , Bachmann P. , Kastelewicz H.
Published: July 2007

Hg‐light absorption at λ = 2537 Ǎ by O3 has been used to measure the concentration of O3 in the positive column of an oxygen glow discharge under the nonstationary conditions of the Q‐form (tube diameter 3:4 cm). For all gas pressures investigated (p = 7 — 12 torr) the O3 density (n3) as a function of the current reaches a remarkable maximum at i ≈ 15 mA. n3 max was found to increase almost linearly with the gas pressure. At i = 80 mA, on the other hand, n3 increases according to a quadratic relation.

In order to understand the dependence of n3 on the pressure and on the current density (or equivalently on the electron density ne) a kinetic model previously developed has been used involving the following particles
equation image
.

For example, it can be shown that in the region of the maximum of n3 one main production process of ozone is the associative detachment reaction
equation image
.

The calculated maximum of the ozone density is higher than the measured one and appears at higher electron density.
Teilprozesse bei der Ozonerzeugung mittels stiller elektrischer Entladungen. I. Die elektrische Entladung im Ozonisator
Authors: Hirth M.
Published: July 2007

Die Arbeit befaßt sich mit den Eigenschaften der stillen el. Entladung in einem Siemens‐Ozonisator. Sie enthält im einzelnen Untersuchungen zur Ladungs‐ und Potentialverteilung auf dem Dielektrikum, zum zeitlichen Stromverlauf einzelner Teilentladungen. zur statistischen Ver‐ teilung der bei einer Einzelentladung geflossenen Ladungsmenge, zur räumlichen und zeitlichen Temperaturverteilung und zur Lage der Wärmequellen im Luftspalt.
Zur Mikrowellendiagnostik der Elektronendichte im Neonplasma der Freifallsäule
Authors: Gundermann S. , Bartels W. , Leven R.
Published: July 2007

Es wird über die Elektronendichtemessung in der Freifallsäule einer Neonentladung berichtet. Die experimentelle Bestimmung erfolgte mit Hilfe der Resonanzfrequenzänderung eines Mikrowellenresonators. Die auf diesem Wege ermittelten Werte der Trägerdichte werden zur Berechnung der Existenzgrenze von Ionenschallwellen verwendet.
Der freibrennende Störlichtbogen
Authors: Klengel H. , Böhme H.
Published: July 2007

Long high current arcs (I ⩽ 60 kA, f = 50 Hz, t ⩽ 200 ms, l = 1 m) appear after discharges at electric power systems. The arc must be localized in a separate volume in order to protect the equipment from the high temperature. The arc is stabilizing by the plasma‐beam starting at its bottom.

The properties of the plasma‐beam are described: general phenomena, the length as a function of current and time, the behaviour in a half‐cycle and the acoustic emission. Several conclusions for the construction of the protective armatures are presented.
Spherical and Cylindrical Solitons in a Warm and Multi‐Electron Plasma
Authors: Kalita M. K. , Bujarbarua S.
Published: July 2007

The ion acoustic soliton has been investigated in spherical and cylindrical geometry in a warm plasma having two electron components each described by a Boltzmann distribution. It has been shown that both potential hump and potential dip are possible in this case.
Perturbational Approach to Force — Free Toroidal Equilibria
Authors: Cap F. , Zagrodzirński J.
Published: July 2007

Solutions of the equation curl B = γB inside a torus‐shaped region with vanishing normal component on the torus surface are sought by the perturbation method. The perturbation parameter is proportional to the curvature of the torus, i.e zero‐order solutions are exact helical solutions for a straight tube.
Ionization Dynamics in a Pulse Disturbed Magnetically Confined Helium Plasma
Authors: Prinzler H. , Heymann P.
Published: July 2007

The equilibrium of a magnetized Helium plasma is disturbed by a pulsed Trivelpiece‐Gouldwave. The electrons obtain the energy by linear collisionless wave absorption. The relaxation phenomena of density and energy are explained in terms of two relaxation times τE, τ1 and a quantity giving the additional ionization. These quantities are derived from a small signal fluid model based upon energy and particle balance equations. In the experiment they are taken from the transient curves of Langmuir‐probe current, optical line radiation and the noise power at the electron cyclotron frequency.

The experimental conditions are: Helium‐gas, p = 1 …︁ 5 Pa, Te = 4 eV, n = 1 …︁ 5 · 1010 cm−3, B = 6,5 · 10−2 T, 27 MHz rf plasma source, low frequency fluctuation level < 1%, classical losses. The energy relaxation time …︁E = 10 …︁ 15 μs is given by inelastic collision losses. The ionization time constant τ1 is related to the instantaneous ionization frequency during the transient state. It shows a high value at the very beginning of the pulse which must be explained by a tail formation in the distribution function and enhanced radial losses becoming Bohm‐like in the transition phase.
Mass Spectrometric Determination of Partial Ionization Cross Sections
Authors: Märk T. D.
Published: July 2007

A review of the measurement of partial electron impact ionization cross sections for rare gas atoms and molecules is presented, with particular regard to the low electron energy regime (<200 eV). Recently developed experimental techniques are surveyed. Predictions of quantal and classical approximations as well as some empirical formulae are compared with the experimental data. In conclusion a set of recommended atomic ionization cross sections is given for electron energies ranging from threshold up to 14 keV. Finally, the existence and measured appearance potentials for the production of doubly ionized rare gas dimers are discussed.
Deposition and Etching of Thin Films by Means of Beam Plasma Discharge with Tube‐Like Electron Beam
Authors: Atamanov V. M. , Levadny G. B. , Ivanov A. A. , Klagge S. , Maass M. , Nasedkin Y. F. , Sereda U. V. , Serov A. A. , Timchenko N. N.
Published: July 2007

The efficiency of energy dissipation caused by the mechanism of turbulent plasma heating from a tube‐like electron beam in a electronegative gas is measured calorimetrically. Amorphous Si‐layers are deposited from a SiH4/Ar discharge both on conducting and nonconducting substrates and are analyzed by means of Auger‐spectrometry. The velocity and specific energy of etching of SiO2‐layers in a CF4‐plasma are determined.

Measured etching velocities of tungsten surfaces biased differently against the space potential provide information on the mechanism of plasma etching in a SF6‐plasma. Simultaneously performed Langmuir‐probe measurements permit predictions to be made on the properties of the etching plasma.
An Improved Two‐Dimensional Snow‐Plow Model for Plasma Acceleration in Coaxial Geometry
Authors: Grosu I.
Published: July 2007

The plasma sheath acceleration in a system of two coaxial electrodes is studied by means of a two‐dimensional snow‐plow model presented in [9]. An improved expression for the variable plasma inductance is used. The calculated values for the final axial velocity and the current intensity are in favorable agreement with experimental values. A comparison between the results of these calculations and those of some recent analytical models is presented.
The Construction of Systems of Equations Describing Gas Discharges Containing Several Species of Atoms and Ions, Including Stepwise Processes, Negative Ions, and the Spatial Variation of the Temperatures
Authors: Valentini H.‐B.
Published: July 2007

The sets of differential equations usually used for the description of the low pressure discharges are underconstrained if several species of atoms and of ions and stepwise processes are taken into consideration. Using the equations of continuity, of momentum transfer, and of energy transfer for each species it is shown that, besides known closing statements for these sets of differential equations, additional conditions are necessary. It is found that the following relatively simple condition is sufficient for positive ions. The radial pressure gradient has to be assumed to vanish at least with the third order as the distance from the axis approaches zero. Various simpler and also more accurate and cumbersome approximations describing non‐excited atoms, positive and negative ions are investigated. Under some conditions one can formulate additional boundary conditions at the wall instead of additional conditions on the axis.
Ionenschallinstabilitäten in Edelgas‐Gleichstromentladungen bei niedrigen Drücken. II. Vergleich der experimentellen Ergebnisse mit einer eindimensionalen kinetischen Dispersionstheorie
Authors: Leven R. , König A.
Published: July 2007

The experimental measurements of the propagation properties of self‐exicted ion acoustic waves in a de‐low pressure column are compared with a one dimensional dispersion theory. The corresponding dispersion relation is developed starting from the linearised Vlasov equation with a Davydov‐type collision term. It is shown, that the mean features of the propagation behaviour of the ion acoustic waves can be explained by the theory. The experimental results concerning the dependence of the upper limit frequency of the waves upon the discharge current should be analysed on the base of new results from plasma diagnostics, taking also into account nonlinear and geometrical effects.
Nonlinear Theory of the Instability of a Modulated Electron Beam of Low Density in a Plasma. I. Conservation Laws of Energy and Momentum for Electromagnetic Waves in a Nonequilibrium Dispersive and Dissipative Medium in the Case of a Slow Change of Amplitude and Phase of the Wave
Authors: Kruscha K. J. G. , Kondratenko A. N.
Published: July 2007

A formula is given for the energy and momentum conservation laws for a narrow spectrum of electromagnetic waves in an unstable dispersive and dissipative medium by any level of dissipation and on condition that the amplitude and phase change slowly in the time and space period of oscillations. It is shown that the density of energy and momentum of the motion of resonant particles, connected with the propagation of the electromagnetic wave, generally cannot be expressed by the dielectric function of the unstable system. For example it is demonstrated that the well known Landau formula for determining the density of the wave energy in a unstable monoenergetic beam‐plasma system in general is not applicable as it is often done in literature.
Experimentelle Untersuchungen axialer Druckgradienten in Niederdruck‐Hochstromentladungen
Authors: Ebert W.
Published: July 2007

Es wurden Messungen des axialen Druckes in Niederdruck‐Hochstromentladungen durchgeführt. Es konnte gezeigt werden, daß der axiale Druck im Entladungsrohr hauptsächlich durch dir Größe des Kathodenraumes oder des Anodenraumes bestimmt wird und nicht durch Entladungsstrom und Fülldruck. Für den Fall, daß das Anodengefäß wesentlich größer als das Kathodengefäß ist, stellt sich ein nahezu konstanter Druck im Entladungsrohr ein (grad p ≈ 0). Die Ergebnisse dieser Experimente sind in Übereinstimmung mit numerischen Rechnungen.
IR‐Emissionsspektrum eines Argon‐Plasmastrahls zwischen 4 und 25 μm
Authors: Winkelmann G. , Tilgner J.
Published: July 2007

Das infrarote Emissionsspektrum eines Argon‐Plasmastrahls (1 atm) wurde im Wellenlängenbereich von 4–25 μm (2500–400 cm−1) mittles eines Fourier‐Transform‐Spektrometers untersucht. Neben zahlreichen schmalen Emissionalinien des Argons (Halbwertsbreite ⩽ 1 cm−1) traten bei 4,636 μm, 7,435 μm und 12,346 μm sehr breite Intensitätsmaxima mit einer Halbwertsbreite von 7; 20 bzw. 39 cm−1 auf.
On Electron Concentration Distribution along the Radius of the Positive Column of a Glow Discharge in Electronegative Gases
Authors: Arutunyan G. G. , Galechyan G. A. , Tavakalyan L. B.
Published: July 2007

It is shown in this paper that the form of the electron concentration distribution along the radius of the positive column in an oxygen discharge depends on the relative concentration of negative ions α = n‐/ne in the plasma.

It is found that in discharges in electronegative gases everywhere along the radius of the positive column, where α > 10, the electron concentration is equal to its value on the tube axis (plane electron distribution along the radius of the positive column).

It is shown that an increase of the discharge current leads to the decrease of α and to the change of the distribution of profile ne from plane to parabolic. However, weak laminar oxygen pumping along the positive column leads to more plane an electron concentration distribution because an increase of the negative ions concentration takes place. It is induced by the decrease of oxygen atoms density on account of their carrying out by the flow.
Nonlinear Theory of the Instability of a Modulated Electron Beam of Low Density in a Plasma. III. Derivation of Nonlinear Equations for the Time‐ and Space‐Problems (Single Wave Model)
Authors: Kruscha K. J. G. , Kondratenko A. N.
Published: July 2007

In this paper it is shown that there are, in dependence on the properties of the system, several systems of nonlinear equations for the description of the nonlinear “hydrodynamical stage” of the beam‐plasma instability. It becomes evident that the well known system of equations for the resonant wave instability in beam‐plasma systems is not applicable for the case of strong dissipation of the wave energy in the plasma and for the case of the excitation of nonresonant waves. As well for the time‐problem as for the space‐problem there are derived three different systems of nonlinear equations. An energetic analysis of the nonlinear stage of the excitation of resonant waves is given. Anomalous growth of the amplitude of resonant waves by interaction with strong modulated electron beams is examined.
Bestimmung der Gastemperatur in Wasserstoffniederdruckentladungen
Authors: Krysmanski K. H.
Published: July 2007

In the positive column of hydrogen low pressure gas discharges the radial temperature profil was measured by an interferometric method. A Michelson‐interferometer in combination with an He—Ne‐laser was used. In the range from 532 to 1330 Pa and 25 to 100 mA for a water cooled tube of inner diameter of 20.5 mm axis temperatures from 340 to 500 K with a nearly parabolic profil were found. Rotational temperatures from the Fulcher‐bands were systematically lower about 15%.
Cathodic and Anodic Spot Phenomena on Rotating Electrode Disks and Plasmatron Electrodes
Authors: Kranz E.
Published: July 2007

The arc spot life time and velocity before reaching melting temperature have been calculated for different electrode materials. They vary between 10−10 to 10−14 s and 102 to 106 m/s for heat flux densities of 109 to 1012 W/m2. The experimental examination of such results was carried out by means of fast rotating electrode disks and tubular electrodes in plasmatrons. The measurements resulted in life times of more than 10−5 s with erosion rates from 10−10 to 10−2 g/As and electrode spot diameters ranging from 0,01 to 5 mm while the heat flux density varied between 107 to 1012 W/m2. Ten different types of continuous traces, single spots, and craters have been found. Some spot phenomena, the high erosion rates of rotating disks and the similarity of ignition events have been clarified for electrodes made from good conductive materials and less conductive. But the melting and boiling of the spot surfaces was inevitable in all cases.
Zur plasmachemischen Umsetzung von CO/H2‐Gemischen zu leichten Kohlenwasserstoffen in einer Glimmentladung
Authors: Mach R. , Drost H. , Dube G. , Spangenberg H.‐J.
Published: July 2007

CO/H2‐Gemische lassen sich durch nichtthermische Aktivierung in einer Glimmentladung teilweise in Kohlenwasserstoffe (KW), insbesondere Methan, umsetzen. Als höchster Umsetzungsgrad des CO → KW ergab sich 12%, als höchster Methan‐Partialdruck 3%. Die CO‐Umsetzung ist abhängig von den Entladungsparametern, der Entladungszeit bzw. dem Energieeinsatz und dem CO/H2‐Mischungsverhältnis. Die gebildeten KW sind Zwischenverbindungen, die zu höheren, darunter auch festen KW, weiterreagieren. Auf Grund massenspektrometrischer Ionenanalysen wurde für die KW‐Bildung ein Reaktionsschema entwickelt, das sowohl für ionische als auch für Neutralteilchen‐Reaktionen als gültig angesehen wird.
Surface Plasma Wave Solitons
Authors: Stenflo L. , Yu M. Y. , Zhelyazkov I.
Published: July 2007

It is shown that nonlinear electron plasma surface waves are modulationally unstable and can propagate as solitons on a cold electron plasma‐vacuum interface.
Impurity Driven Linear and Nonlinear MHD Cylindrical Waves in a Three Species Plasma
Authors: Singhal R. , Srivastava K. M. , Chhonkar R. P. S.
Published: July 2007

The propagation of axisymmetric linear and nonlinear dispersive waves in a three species plasma to include the thermoelectrostatic effects together with the dissipative effects of main ions has been discussed. The impurity driven MHD fluid modes have been examined when the electrostatic drift has been taken into account. We have discussed the linear propagation of dispersive cylindrical waves in the plasma system for different ion thermal phase number. The thermal force resulting from the collisions between main ion and impurity ion densities (i.e. αiI = 0) has been neglected. The shock waves and the soliton solutions are obtained for two different cases of the non‐collisional plasma and the non‐dissipative plasma.
Elektronenstrom zylindrischer Langmuirsonden bei Nichtmaxwellverteilungen
Authors: Johanning D.
Published: July 2007

One of the main assumptions of the conventional Langmuir probe theory is the demand for a Maxwellian distribution function.

In this paper is tried to calculate probe currents for non‐Maxwellian electron energy distributions.

The classical Langmuir formula for the orbital‐motion‐limited current of cylindrical probes is simplified. The new equation permits a very easy detailed examination of the effects of non‐Maxwellian electron energy distributions on the current‐voltage characteristics in the accelarating region for large probe voltages.

It is shown that the electron current is independent of the form of the electron energy distribution, if the mean electronenergy Ē is constant.

Variations of the mean energy change the probe current slightly.

As examples currents are computed for two non‐Maxwellian distribution functions.
Spatial Characteristics of the Beam Plasma Discharge in Crossed Electric and Magnetic Fields
Authors: Gadeev K. K. , Denkevits A. V. , Ivanov A. A. , Nikiforov V. A. , Shapkin V. V.
Published: July 2007

The paper presents the results of the experimental investigation of the beam plasma discharge spatial structure in crossed fields induced by adding a high ionization potential gas to the discharge. Direct experimental evidence of the polarization mechanism of the radial current in a device with this type of discharge has been obtained.
The Electrical Conductivity of Plasma in Wide Range of Charge Densities
Authors: Kurilenkov Yu. K. , Valuev A. A.
Published: July 2007

The possibility of the existence of plasma oscillations in nonideal plasma and their role in effective “collision” frequency are analyzed. The simple formula for the electrical conductivity of nonideal plasma is obtained on the base of model considerations. An account is taken of a new scattering mechanism, namely, the collective plasma oscillations.
Perturbed Arcs in Turbulent Axial Gas Flow. III. Numerical Simulation of Stochastically Disturbed Arc Discharges
Authors: Rothhardt L. , Schumann A.
Published: July 2007

Stochastically perturbed arcs are modelled by means of a Mayr type differential equation, the thermal constant τ being stochastically controlled by Gaussian fluctuations of given dispersion and correlation time: 1/τ = 1/τ0 (1 + ζ). The ζ‐signals are taken from an electronic noise source by an appropriately equipped intelligent CAMAC crate, which further processes the whole simulation program.

Special cases treated are 1. stationary (in the mean) arc, 2. freely decaying arc, and additionally, 3. thermal reignition of a decaying arc with stiff recovery voltage.
Electron Kinetics of Weakly Ionized HF Plasmas. II. Decoupling in the Fourier Hierarchy and Simplified Kinetics at Higher Frequencies
Authors: Winkler R. , Deutsch H. , Wilhelm J. , Wilke Ch.
Published: July 2007

In a preceding paper based upon the time dependent Boltzmann equation the electron kinetics of the weakly ionized HF plasma was investigated firstly by a time‐consuming direct treatment and secondly by the Fourier expansion for the established HF state. Continuing these investigations, the decoupling of the equation determining the period average of the isotropic distribution from the other equations of the system for the harmonics of the isotropic distribution is quantitatively studied for a neon plasma as a typical representative. In this way the applicability of a simplified approach for the electron kinetics in the HF plasma could be justified and a former estimate for a field frequency above which this kinetics can be used could be confirmed. The generalization of this simpler description to arbitrary HF fields and to HF plasmas in other gases is discussed. Employing this approach, the electron kinetics is systematically investigated for the HF plasma in Ne for wide ranges of the HF field amplitude and field frequency.
Amplification of Ion‐Acoustic Solitary Waves in a Vlasov‐Plasma. II. Existence of a Maximum Potential and Numerical Experiments
Authors: Bruhn B. , Leven R.
Published: July 2007

We demonstrate a proof for the existence of a maximal potential for the higher nonlinear evolution equation (see part I). This maximum potential depends upon the plasma parameters and therefore upon the mechanism of instability too. The problems of the stability and of the asymptotic soliton solution are discussed. Finally we present different numerical results.
Experimental Study of Ion‐Acoustic Instability in Stratified Krypton and Xenon Plasma at High Pressures
Authors: Serapinas P. , Šimkus P.
Published: July 2007

The ion‐acoustic instability in gaseous discharge plasma in krypton and xenon at the pressures 0.4 to 2.5 Torr was found and studied. The necessary conditions for the instability existence were satisfied only in the ionisation wave region where electron density was about an order larger than average one. The detected noise amplitude and frequency dependence on the glow discharge plasma parameters was also investigated.
Density of fast electrons on the Axis of a Zylindrical Hollow‐Cathode Discharge
Authors: Handle F. , Lindinger W. , Howorka F. , Pahl M.
Published: July 2007

Fast electrons leaving a hollow cathode discharge axially through the orifice of a hole probe undergo ionizing collisions with the discharge gas in and behind the orifice. Ar++ ions produced in this way are used as a monitor for the density of fast electrons, Nef, on the axis of the negative glow of a cylindrical hollow cathode discharge. Data on Nef as dependent on the pressure of the Ar discharge gas and on the discharge current are obtained and an analytical expression for these dependences is found and discussed.
Schwingungsrelaxation und Gasaufheizung bei periodischem Betrieb der Impulslaser‐Gasentladung in Stickstoff
Authors: Wojaczek K.
Published: July 2007

Für eine typische Impulslaser‐Gasentladung in ruhendem Stickstoff wird das zeitliche Verhalten der Schwingungstemperatur zwischen zwei Entladungsimpulsen rechnerisch untersucht, wobei eine verallgemeinerte Treanor‐Verteilung der Besetzung der Schwingungsniveaus zugrunde gelegt wird. Als Abbauprozesse der Schwingungsenergie werden Wandstöße, VV‐ und VT‐Prozesse berücksichtigt. Es ergeben sich Angaben über die Schwingungstemperatur zu Beginn jedes neuen Entladungsimpulses und über die Gastemperaturerhöhung gegenüber der Rohrwand in Abhängigkeit von der Folgefrequenz. Abschließend wird diskutiert, welche Einflüsse die erhöhten Schwingungs‐ und Gastemperaturen auf die Leistung des Stickstoff‐Impulslasers haben können.
Resonant Wave‐Particle Interaction in an Explosively Unstable Beam‐Plasma System. I. Derivation of a System of Nonlinear Equations and Numerical Evaluation of the Saturation Field Strength
Authors: Kruscha K. J. G. , Leven R. W.
Published: July 2007

The evolution of a resonant triplet of linearly stable electrostatic waves in a beam‐plasma system is considered. A set of nonlinear ordinary differential equations is derived, which allow an investigation of the explosive instability with minimum numerical expense. Our model is different from the well known single wave model in taking into consideration the nonlinear susceptibility of the plasma and in making use of the ponderomotive force description. Maximum values of the wave amplitudes are obtained numerically and it is shown that the saturation of the explosive instability is due to different trapping mechanisms of the beam electrons by the excited waves.
Fundamentals of a Technique for Determining Electron Distribution Functions by Multi‐Term Even‐Order Expansion in Legendre Polynomials 1. Theory
Authors: Winkler R. , Braglia G. L. , Hess A. , Wilhelm J.
Published: July 2007

On the basis of our recent investigations concerning the mathematical structure of the hierarchy which results from the Legendre polynomial expansion of the electron velocity distribution function in Boltzmann's equation a new technique for solving this equation in multi‐term even‐order approximation is presented. This method is, even if more complex, the logical generalization of the well known technique for solving Boltzmann's equation by backward integration in the conventional two‐term approximation. A weakly ionized, spatially homogeneous and stationary plasma with elastic and exciting electron‐atom collisions is considered acted upon by a dc electric field.

The technique, presented in detail, determines the distribution function in even order 2l of the expansion at the end by l‐fold backward and 2l‐fold forward integration of the hierarchy and by continuous connection of the resulting non‐singular parts of the general solutions at low and high energies at an appropriate connection point. A first application of this method is made on a model gas for the even orders from 2 to 10 and under conditions with distinct anisotropy in the velocity space due to intensive exciting collisions. The converged macroscopic quantities and the corresponding first coefficients of the distribution expansion itself are compared with very accurate Monte Carlo simulations under the same conditions where a perfect agreement between the results obtained with both techniques was found confirming the high accuracy of the new technique to be presented.
Propagation and Absorption of ECR Waves in a Low Temperature Toroidal Plasma of Small Size and Magnetic Field
Authors: Someşan M. L.
Published: July 2007

The propagation and absorption of ECR waves in a tokamak plasma with small size and low values of the electron temperature and the toroidal magnetic field is studied numerically. The cold plasma dispersion equation is solved and ray tracing calculations are performed to find the accessibility conditions and the optimal angle of wave launching for maximal ECR absorption. Absorption coefficients are computed in the high density approximation.
High‐Velocity Projectile‐Stabilized z‐Pinch
Authors: Winterberg F.
Published: July 2007

A high current z‐pinch can be stabilized by a thin long projectile accelerated to a few km/sec, if the projectile is shot through the core of the pinch. Furthermore, as a result of the thermomagnetic Nernst effect both the heat conduction and radiation losses at thermonuclear temperatures are sufficiently small. The stabilized pinch configuration can therefore be used for the controlled release of large amounts of thermonuclear energy from a dense plasma. The needed projectile velocity of a few km/sec can be already reached with chemical propulsion.
Ferroelectrics in Plasma Chemistry
Authors: Szymański A.
Published: July 2007

The qualitative considerations are presented concerning the use of plasma, generated at the surface of ferroelectric samples, for the investigation of chemical processes. The physical principles of the phenomena, its possibilities and limitations are described. Also, preliminary conclusions resulting from the investigations carried out up to the present, are drawn up.
Numerical Study of the Instability in a Maxwellian Beam‐Plasma System II. Many Wave Regime
Authors: Bodrow W. , Leven R. W. , Koch B. P.
Published: July 2007

The relaxation of the beam‐plasma system with several preliminarily excited unstable waves in its spectrum is investigated on the basis of computer simulations. The nature of the waves and particles interaction during the instability development is analysed. It is shown that the destroying of the amplitude oscillations of the single wave after saturation in the presence of additional waves is caused by the well known effect of resonance overlapping. A chaotization of the motion of the beam particles occurs even in the case when the amplitudes of the neighbouring waves are small.
Investigation of the Beam Plasma Discharge in Electronegative Gases Using the Second Derivative of Langmuir Probe Characteristics
Authors: Klagge S. , Maass M. , Serov A.
Published: July 2007

The distribution of the charge carriers is measured and the influence of the attachment processes on the electron energy distribution function is demonstrated for beam plasma discharges in SF6, CF4 and O2 with the aid of the second derivative of Langmuir probe characteristics. The structuration of the plasma into regions of predominating negative ions and regions of predominating electrons is determined by the the established radial Te‐profile. The dimension of the quasi electronfree plasma changes significantly as well at transition from the turbulent heating mechanism into the electron impact plasma generation as by occuring low‐frequency instabilities. With increasing n−/ne a deficit of low energetic electrons appears in the electron energy distribution parallel to the formation of the negative ion peak. The saturation currents at ne/n−=0 yield the mass ratios between negative and positive ions.
Deuterium and Impurity Flux Measurements in the Boundary Plasma of T‐10
Authors: Grote H. , Hildebrandt D. , Strusny H. , Kotai E. , Manuaba A. , Paszti F.
Published: July 2007

Time resolved measurements of deuterium and impurity fluxes in the boundary layer of T‐10 tokamak were carried out using carbon strips as deposition probes. Analysing these probes by RBS and ERD deuterium impact energies of 25–40 eV could be estimated from the saturation behaviour of deuterium in carbon. The high impurity concentration level and it's time behaviour give indications for local impurity producing sources playing an important role for the impurity transport in the near wall plasma.
Ionization Cross Sections of Gas Molecules for Plasma Chemistry
Authors: Deutsch H. , Schmidt M.
Published: July 2007

Using the recently tested formula of Gryzinski electron impact ionization cross sections for several molecules are calculated. The additivity rule and the statistical approach by Fitch and Sauter are discussed. With new experimental ionization cross sections it is possible to derive the regression coefficients also for P, As, B, and Si, which are presented together with the previously obtained values as a function of the atomic number. It appears to be possible to obtain coefficients for other atoms by interpolation. First attemps to determine regression coefficients also for 20 and 35 eV electron energy are discussed.
A Note on the Monte Carlo Simulations of Non‐Equilibrium Electron Energy Distributions
Authors: Braglia G. L.
Published: July 2007

The Monte Carlo method is an important approach for finding solutions of the electron Boltzmann equation in a gas in a field under conditions which are particularly difficult to be treated by analytical techniques. For this reason several expedients have been invented to reduce the computer time and make the simulations sufficiently fast and accurate. In this paper it is shown how the most significant expedients can be extended and used to simulate electron motions in non equilibrium situations.
Numerical Analysis of Symmetrical Waves Dispersion in a Nonisothermal Plasma Waveguide in a Magnetic Field
Authors: Nikolov N. A. , Dankov P. I.
Published: July 2007

Dispersion equations of a nonisothermal plasma waveguide in a constant external magnetic field are derived, when the magnetic field intensity tends to infinity. The plasma electrons' thermal velocity are taken in mind. A numerical analysis of dispersion equations for the E‐ (TH‐) and H‐ (TE‐) waves is made. In the high‐frequency range it shows the possibility of the slow E‐waves exciting with a higher frequency than the electron Langmuir frequency. In the range near to the ion Langmuir frequency it shows the existence of waves with an anomalous dispersion. These waves are named low‐frequency backward E‐waves and it is shown, that in some frequency ranges they change the group velocity sign. The dispersion is investigated also in respect to the waveguide plasma filling.
Multiphoton Excitation and Ionisation in the 9–12 eV Region of O2 by a 1.06 μm Glass Laser
Authors: Godart J.
Published: July 2007

In this letter we report results of a selective multiphoton excitation of O2 in the 9–12 eV region by a neodymium glass laser. The main feature of this experiment is the major presence of the ion specie O2+ in the interaction volume with the values 10 ± 1 for the nonlinear interaction order. This result can be interpreted as a double mechanisms namely: a one step process, the direct absorption from the ground state or a two step process via an intermediate resonant state which has been attributed as the second (B′3Σu−, v′=2) state of O2 located at 10.56 ± 0.03 eV. The probability of multiphoton formation of O2+ for a flux value of 1,5 × 1012 W/cm2 is equal to 2 × 107±1 sec−1.
Effect of Hall Current on the Magnetogravitational Instability of Anisotropic Plasma with Generalized Polytrope Law
Authors: Chhajlani R. K. , Purohit P.
Published: July 2007

The effect of Hall current on the propagation of small perturbations through self gravitating anisotropic collisionless pressure plasma with generalized polytrope law is investigated. The poly‐trope law for pressure components parallel and perpendicular to the direction of magnetic field is utilized in the analysis. The effect of Hall current and finite conductivity is introduced in the generalized Ohm's law. Using the polytrope law and Ohm's law dispersion relations are obtained from linearized perturbation equations for wave propagation along and perpendicular to the direction of magnetic field. The dispersion relations incorporating polytrope indices are able to represent the Chew, Goldberger and Low approximation with double adiabatic equation of state for the anisotropic pressure and the magnetohydrodynamic set of equations with isothermal equation of state for the isotropic pressure. The effect of Hall current, finite conductivity and polytrope indices is discussed on the well known hose and gravitational instability. It is found that Jeans' criterion depends on polytrope indices and the condition of gravitational instability is determined for different special cases of interest.
Sudden Jumps, Hysteresis, and Negative Resistance in an Argon Plasma Discharge. I. Discharges with No Magnetic Field
Authors: Bosch R. A. , Merlino R. L.
Published: July 2007

Jumps and hysteresis in discharge current are produced in a low‐pressure (10−5 – 10−4 Torr). magnetic field free, thermionic argon plasma discharge by varying discharge voltage, neutral pressure, or filament temperature. This behavior can be attributed to a region of negative differential resistance in the voltage versus current characteristic of the discharge. A model is presented in order to understand the physical processes leading to this negative resistance.
[Russian Text Ignored]
Authors: [Russian Text Ignored]  , [Russian Text Ignored]  , [Russian Text Ignored]
Published: July 2007

This work is devoted to the investigation of physical processes in a non‐equilibrium plasma of a binary mixture of inert gases. The degree of radial separation of the mixture was found to increase with increasing pressure of buffer gas and discharge current and to decrease with growing partial pressure of the admixture. The correlation of the radial and axial types of separation was shown experimentally. The kinetics of population of the metastable states He(23S) and Xe(3P22) and of charged particles was investigated using an impulse regime. The time for the establishment of the stationary state of the radial distribution of the components was found to be several times less than the time of reestablishment of the homogeneous distribution of the atomic component after switching off the discharge impulse. The phenomenon of a decreasing effective diffusion length of the discharge was found. This effect has essential influence on the time for the establishment of the stationary state of radial cataphoresis.
An Efficient Spectroscopic Control — Technique of the Parameters of Thermic Plasmas Produced under the Condition of a Variable Current
Authors: Halenka J. , Janus H.
Published: July 2007

The spectroscopic diagnostics has been carried out as an example for an argon plasma from Maecker‐Shumaker type electric arc supplied by periodic variable current. It is shown that the time‐dependent runs of intensity of the plasma light may be determined using an ordinary oscilloscope. We have stated that the electron concentration Ne in the plasma is the most sensitive quantity to the current pulsations. In the percentage, Ne variations at the arc axis are approximately the same as the current ones.
Two Dimensional Megagauss Magnetic Field Variation Along Axial and Radial Direction of Laser Axis for a Plasma Produced due to Laser Irradiation on the Surface of a Wire Target
Authors: Jha L. N. , Srivastava M. P.
Published: July 2007

The variation of megagauss magnetic field in two dimensions for a cylindrical target plasma produced by lasers irradiation on the surface of a cylindrical wire has been solved analytically making use of Hankel and Fourier transforms. The results have been compared with the experiments of RAVEN et al. (1978).
Theoretical Studies of the Laser Induced Plasma Profile Near the Critical Density Region for an Adiabatic Plasma Model
Authors: Paikaray R. , Srivastava M. P.
Published: July 2007

A theoretical study of the variation of density and flow velocity due to pondermotive force, near critical density region of a laser – produced plasma, obeying an adiabatic pressure law is reported. The ion‐continuity, momentum and wave equations are solved in a steady state. The density and flow velocity as a function of incident laser intensity are calculated and plotted for both underdense and overdense regions for adiabatic exponent γ = 4/3, 5/3, 2. The velocity decreases and density increases in the overdense region and velocity increase and density decreases in the underdense region with the increase of larger power at sonic point. It is found that the velocity is subsonic in the overdense region and supersonic in the underdense region. The nature of variation is similar to the isothermal model.
A Note on Second Harmonic Resonance of a Magneto‐Acoustic Wave in Planar Plasma‐Filled Waveguide
Authors: Gosh B. , Das K. P.
Published: July 2007

The second harmonic generated by non‐linear self interaction of a magneto‐acoustic wave in a planar plasma‐filled waveguide is a freely propagating mode. Coupled‐mode equations for resonant nonlinear interaction of this second harmonic mode with the fundamental mode are derived. Using these equations the possibility of generation of the second harmonic is analysed.
On the State of Ionization, Non‐Ideality and Electric Conductivity of the Cathode Plasma of Vacuum Arcs
Authors: Anders S.
Published: July 2007

The cathode spot plasma of a metal vapour are in vacuum has a high density (1025–1028 m3) with a relatively low temperature (1–5 eV), therefore it is strongly non‐ideal. The degree of ionization α and the electric conductivity σ of such plasmas are discussed, considering that non‐ideality. The burning voltage of the arc UB is estimated with the help of σ‐values, obtained from theories and measurements for non‐ideal copper plasmas. It is shown, that a high current density of the cathode spot of j = 1012 A/m2 is not in contradiction to a low burning voltage UB = 20–30 V, but these values give a consistent picture of the spot processes.
Long Time Behaviour of Marginally Stable Magnetomodulational Perturbation
Authors: Majumdar D. , Bhakta J. C.
Published: July 2007

The long time behaviour of magnetomodulational perturbation has been investigated by using multiple time scale perturbation method. If the perturbation field is purely potential, it is found that unlike ordinary modulational unstability the magnetomolulational instability persists in the nonlinear stage of evolution. The exact analytical solution obtained for the marginally stable mode of the linear theory exhibits explosively unstable behaviour in the slow time scale. When both potential and solenoidal components of perturbation are present the transverse exerts a stabilising influence. Different kinds of long time behaviour may occur as medicated by the results of the numerical integration of the coupled nonlinear evolution equations for the Langmuir and transverse fields.
Electron Density and Temperature Rise Time of a Weakly Ionized Oxygen Plasma Subject to an Alternating Electric Field
Authors: Baumgärtel K. , Sauer K. , Wilhelm J. , Winkler R.
Published: July 2007

Macroscopic balance equations for particle number, momentum and energy of the electrons are derived from the Boltzmann equation which describe the time evolution of a weakly ionized oxygen plasma exposed to an alternating homogeneous electric field. The equations are applied to estimate the rise time of electron temperature and density when a rf pulse is emitted from a satellite into the ionospheric plasma.
Computermodelling of Fluorescent Lamp Plasmas
Authors: Sonnenburg R. , Gündel H.
Published: July 2007

A computer model is designed in which the lamp voltage is obtained by solving the equations of the operating circuit.

The lamp resistance is determined by using hydrodynamic equations for the lamp plasma with following conditions:

— three level model of Hg vapour ground, one lumped excited and the ionization level

— direct and stepwise ionization are included as well as deexcitation and radiative decay

— the plasma is controlled by ambipolar diffusion

— no excitation and ionization of the buffer gas is assumed

— both the buffer gas and neutral Hg atoms are considered to be equal distributed over the cross‐section of the discharge tube.

The model allows to calculate the main time dependent lamp parameters and their time averaged values.

We found a good qualitative and quantitative (about 1 to 5%) agreement compared with standard fluorescent lamps.

The model shows the tendency of lamp voltage increasing to smaller tube diameters.

The model gives qualitatively the right dependence of lamp efficacy on the buffer gas pressure.

The behaviour of the angle of lag and the power factor in dependence on the tube diameter obtained by the model shows also the right tendency.

Further calculations and experimental verifications are needed to reach several improvements of the model.
Study of the Stimulated Brillouin Scattering in a Dissipative Two‐Ion Species Plasma
Authors: Guha S. , Dwivedi C. B.
Published: July 2007

Analytical study of the stimulated Brillouin scattering in a two‐ion species plasma has been done using the hydrodynamical model. When strong nonlinear effect becomes significant i.e., when the quiver velocity of the electron becomes of the order of or greater than its thermal velocity, the damping becomes intensity dependent which modifies the results over the weak nonlinearity. In this regime the plasma behaves as a collisionless medium. The inclusion of the second species of the ions modifies the instability and decreases the growth rate. Its application in fusion plasma has been discussed.
Data Smoothing Effects on the Abel Inversion Method in Plasma Spectroscopy
Authors: Sato M.
Published: July 2007

An investigation is given for the effects of smoothing on the Abel inversion method for obtaining radial intensity profiles from chordal intensity profiles. Before the radial intensities are calculated by means of the familiar inversion methods, such as by Nestor‐Olsen, Bockasten, Frie, etc., the chordal intensities with random scatterings are smoothed by easily available methods, the least‐square fitting with Taylor expansion correction and the B‐spline fitting. Through numerical simulation tests, it is shown that this procedure of smoothing is very useful for an accurate Abel inversion without relying upon more complicated inversion methods having clever smoothing processes, e.g., by Piessens, Fleurier and Chapelle, Glasser et al., etc.
Investigations on the Electron Component in an Argon‐Hexamethyldisiloxane (HMDS) Low Pressure Glow Discharge by Probe Diagnostics
Authors: Maass M. , Schmidt M.
Published: July 2007

Probe measurements were carried out in the positive column of an argon glow discharge in a flow system with different admixtures of hexamethyldisiloxane (HMDS). From this the mean electron energy ne, number density ne and gradient E were determined. Some results concerning the predominant ionization mechanism and the ion distribution in the gas phase could be obtained. By means of probes it is also possible to get some information about the deposition mechanism in polymerizing plasmas.