bluuebunny/crossref_metadata_2025 huggingface dataset:
Doppelsonden‐Messungen in Glimmentladungen bei starken Magnetfeldern
Authors: Peter G. , Rybarsch H.
Published: July 2007

In Niederdruck‐Glimmentladungen wird der Einfluß starker Magnetfelder (B ≦ 1,2 kG) auf die Ionenströme zu unsymmetrischen (flächenungleichen) Doppelsonden untersucht. Das Magnetfeld beeinflußt den Ionenstrom bereits, wenn die Ionenzyklotronradien noch groß gegen den Sondenradius sind. Die effektive Fläche der Sonde hängt nicht nur von ihrer Orientierung zum Magnetfeld ab, sondern auch davon, wie die von der Sonde entleerten Flußröhren wieder aufgefüllt werden (‖ B oder ⟂ B). Bei bestimmten Magnetfeldern werden ferner Resonanzen des Ionenstromes (Ionenzyklotronradius‐Resonanzen) gefunden. Diese Resonanzen entstehen durch eine gegenseitige Beeinflussung der beiden Sonden über eine Entfernung von einem Zyklotrondurchmesser der Ionen. Die Ergebnisse stimmen mit Messungen von Sato[1] und mit deren Deutung durch Peter und Sato [2]überein.
Spectroscopical Observation of a Relaxing High Speed Nitrogen Plasma Jet
Authors: Neumann W. , Hayess E. , Venzke D.
Published: July 2007

A near sonic nitrogen plasma jet operating at pressures between 100 Torr and 1 atm has been investigated spectroscopically. From the absolute emission coefficient of a NI spectral line, local values for the electron temperature Te have been derived. For pressures above 200 Torr, Tg was found to coincide within the limits of experimental error with the gas temperature Tg. The latter quantity has been determined via the relative emission coefficient of selected rotational line components of the N2+ molecular band at 3914 Å. The results of these measurements together with control data for the electron density derived from the continuous emission coefficient indicate that at pressures above 200 Torr the existence of a thermal equilibrium between the degrees of freedom corresponding to particle translation, electron excitation, and ionization can be accepted, at least for the inner zone of the plasma jet.

To the contrary, the data for the absolute emission coefficient of N2+ molecular band lines show that the degree of dissociation in the plasma jet is much in excess of that corresponding to equilibrium. This phenomenon can be explained as a result of the rapid temperature decay in the plasma from initially 13000 K in the arc heating zone to T ≦ 9000 K in the plasma jet zone proceeding in a time interval of 10−5 s which is much shorter than the time necessary for adjustment of dissociation equilibrium.

In the outer cool zone of the plasma jet, an unusual high intensity of the N2+ radiation was found thus indicating the existence of a nonequilibrium excitation mechanism typical for a decaying nitrogen plasma.

From the supernormal high degree of dissociation in the high‐speed subatmospheric nitrogen plasma jet, conclusions are drawn with respect to its applicability as source of reactive particles in plasma‐chemical experiments.
Die Entstehung des elektrischen Feldes im anomalen Katodenfall einer realen Glimmentladung aus den Feldern von Raumladungen und Flächenladungen
Authors: Döpel R.
Published: July 2007

Um den Grund der großen Diskrepanz zwischen theoretischer und empirischer Bestimmung des Feldverlaufs im anomalen Katodenfall von Glimmentladungen zu klären, wird die einwandfreie Lo Surdo‐Methode in der Weise angewendet, daß sie nicht nur den steilen Abfall des Feldes in der Nähe der Katoden, sondern gleichzeitig dessen allmähliches Abflauen im weiteren Verlauf des Dunkelraumes dokumentiert. Das Resultat legt nahe, daß die bisher nur eindimensional durchführbare theoretische Feldberechnung das Feld einer realen Glimmentladung deshalb nicht vollständig wiedergeben kann, weil jene Theorie die Wirkung der im Realfall unvermeidbaren Wandladung außer acht läßt. Der experimentelle Beweis für die Richtigkeit dieser Vermutung wird erbracht durch einen künstlichen stufenweisen Aufbau eines analogen Feldes aus Raumladungen und Wandladungen außerhalb des Dunkelraumes.
Wandladungsbestimmte Impulsentladungen in Kapillaren
Authors: Arndt R. , Lange H. , Spreemann J.
Published: July 2007

Das Verhalten von impulsförmig verlaufenden HF‐Entladungen an isolierten Elektroden wird unter anwendungsbedingten Gesichtspunkten für den Fall Ne—N2‐gefüllter kapillarartiger Entladungsraumgeometrien untersucht und insbesondere der Verlauf der Zünd‐ und minimalen Erhaltungsspannung und die Lichtabstrahlung am Kapillarende in Abhängigkeit vom Fülldruck, N2‐Zusatz, Frequenz der Erhaltungsspannung und den geometrischen Parametern verfolgt. Es kann nachgewiesen werden, daß die Entladungen als die bekannten pulse und continuous modes auftreten. Sie besitzen jedoch im allgemeinen höhere Zündspannungen UZ als die an ebenen Geometrien und zeigen in ihren Abhängigkeiten von geometrischen Größen Besonderheiten. Die niedrigste UZ haben dünne zylindrische Elektroden auf Quarz, die wegen der erhöhten Elektrodenkapazität auch die stärkere Lichtabstrahlung besitzen, die höchste gekreuzte Drahtelektroden. — Bei der Konditionierung durch eingestrahltes UV können Rückwirkungen auf UZ auftreten. Die Lichtabstrahlung am Kapillarende erfolgt wegen der Linsenwirkung des beim Abziehen entstandenen Glastropfens gerichtet und hängt außer von Gasart und ‐druck von der Zahl der gezündeten Zellen, ihrem Abstand vom Kapillarende, sowie von Frequenz, Elektrodenabstand und ‐art ab.
Hydromagnetic Stability of a Self‐Gravitating Composite Plasma in the Presence of Finite Larmor Radius
Authors: Maheshwari S. L. , Bhatia P. K.
Published: July 2007

The hydromagnetic stability of a self‐gravitating composite plasma has been studied to include the effects of ion viscosity and the finiteness of the ion Larmor radius. The whole medium is embedded in a uniform horizontal magnetic field. The F. L. R. effects have been included through the stress tensor. An explicit solution for a semi‐infinite plasma of finite depth and with an exponential density variation along the vertical is obtained by means of a variational principle characterizing the problem. Numerical calculations show that the influence of the effects of ion viscosity and F. L. R. is to reduce the growth rate of unstable perturbations. On the other hand the effects of neutral gas collisions have been found to be both stabilizing as well as destabilizing.
Untersuchungen über das dynamische Verhalten des Säulenplasmas einer Neon‐Niederdruckentladung bei mittleren Ionisierungsgraden 10−6‐10−4 I. Die Impedanz des Säulenplasmas
Authors: Deutsch H. , Pfau S.
Published: July 2007

Ausgehend von den Bilanzgleichungen des Säulenplasmas einer Neon‐Niederdruckentladung bei mittleren Ionisierungsgraden η ϵ 10−6 ⃛10−4 werden die als Folge einer Stromstörung sich einstellenden Schwankungen der wichtigsten Entladungsparameter berechnet sowie die Impedanz des Säulenplasmas bestimmt. Die Berechnung erfolgt unter der Voraussetzung kleiner periodischer Störungen nicht zu hoher Frequenz (f ≦ 104 ⃛105 Hz), so daß einmal eine Linearisierung der Bilanzgleichungen für die Störgrößen möglich ist und zum anderen mit einer quasistationären Elektronenkinetik gerechnet werden kann. Die berechneten Impedanzkurven werden experimentell erhaltenen gegenübergestellt.

In dem nachfolgenden Teil II werden Fragen des elektrischen Ersatzkreises der Säulenimpedanz sowie des Einschwingverhaltens des Säulenplasmas bei impulsartigen Stromänderungen diskutiert.
On the Production of Methane by Electrical Arcs in Ultra High Vacuum
Authors: Jüttner B. , Roth L. , Wolff H.
Published: July 2007

By mass spectrometry of residual gas in UHV‐arc‐chambers a cycle of production of methane has been found for clean electrodes, consisting in release of hydrogen during the arc, its re‐adsorption on freshly formed metal surfaces, followed by surface reactions of hydrogen with carbon impurities, and finally desorption of the resulting methane at room temperature after the arc. Existing methane is decomposed in part during an arc. In the pressure region ≦ 10−4 Pa most of the residual gas is transformed to CH4 if the electrodes contain metals with high gettering activity.
The Poukey‐Rostoker‐Model of Relativistic Electron Beam Propagation: Further Comments
Authors: Hantzsche E.
Published: July 2007

Several properties of the analytic one‐dimensional model of relativistic electron beam propagation published by POUKEY and ROSTOKER [1] are discussed in the more realistic case of a time‐dependent current. The general beam behaviour is similar to that in the case of constant current; the time that is necessary to build up the space charge wall and the potential well (typically ≈ 1 ns) and the sheath thickness (typically a few cm) are evaluated in the case of constant current growth rate.
On the Momentum, Mass and Energy Transport for Transverse Wave Packets in Warm Plasmas, with Applications to Solitons
Authors: Petrž;ílka V. A. , Wallis G.
Published: July 2007

The energy‐mass equation has been formulated for transverse wave packets of an arbitrary form propagating in warm plasmas and then it has been applied to solitons. In contradistinction to a soliton mass given by Klein [7], the mass defined here cannot be chosen arbitrarily.
Zeitliche Entwicklung des Reflexionskoeffizienten einer Plasmaschicht bei starker elektromagnetischer Einstrahlung
Authors: Andrejew N. E. , Sauer K.
Published: July 2007

We have calculated numerically the temporal evolution of the nonlinear reflection coefficient R of an overdense plasma layer by solving the system of partial differential equations consisting of the wave equation for the slowly varying amplitude of the electric field and the hydrodynamic equations for the ion motion, including a ponderomotive force term. In dependence of the (normalized) amplitude of the incident wave uA two regimes exist: Below a critical amplitude uA* ≲ 1 the reflection coefficient is approximately independent on the amplitude uA and temporally constant. In the opposite case uA>uA*, on the other hand, ‖R‖2 decreases slowly with time down to a minimum value and after that it increases rapidly to the initial value. We think, that our results are important to interpret the anomalous reflectivity observed in some experiments when strong electromagnetic waves are incident on an overdense plasma.
[Russian Text Ignored]
Authors: [Russian Text Ignored] [Russian Text Ignored]
Published: July 2007

The parametric excitation of longitudinal waves in an infinite homogeneous plasma by a pump field E(t) = E0(t) sin (ω0t + φ(t)) is studied on the basis of the Vlasov equation, where the amplitude E0(t) and the phase φ(t) are slowly varying compared with ω0 periodic functions. Firstly it is assumed that ω0 is much larger than the electron plasma frequency ωLe. In the second part the parametric instabilities are considered under the resonance condition ω0 ≈ ωLe. In both parts the threshold fields for the excitation of the longitudinal waves and their growth rates are calculated. As an example these values are analysed for both a sequence of pump impulses and a phase‐moduated pump field. They are compared with the results received for a monochromatic pump field.
Propagation of Nonlinear Ion‐Acoustic Waves in a Hot Collision‐Dominated Plasma
Authors: Shukla P. K. , Tagare S. G.
Published: July 2007

It is shown that the propagation of nonlinear ion‐acoustic waves in a collisional plasma is governed by the modified Korteweg‐de Vries‐Burgers or the Burgers equation. The stationary shock like solution of the KdV‐Burgers and Burgers equations is discussed for the medium in which the electron thermal conductivity is very large.
Die Relaxation der Geschwindigkeitsverteilungsfunktion der Elektronen im homogenen elektrischen Feld mit elastischen und anregenden Stößen. II. Das Verhalten des Elektronenensembles bei aperiodischer Feldänderung zwischen zwei stationären Zuständen
Authors: Wilhelm J. , Winkler R.
Published: July 2007

Ausgehend von Untersuchungen einerseits zur Relaxation unter feldfreien Verhältnissen nach sprunghaftem Ausschalten des elektrischen Feldes, andererseits nach sprunghafter Änderung des elektrischen Feldes in einen neuen Feldstärkewert wird jetzt der Relaxationsvorgang im Elektronen‐ensemble für zeitlich monoton veränderliche Felder bei Variation der Zeitdauer für die Feldänderung analysiert. Grundlage hierfür bildet die Berechnung der zeitlichen Änderung des Isotropteils der Geschwindigkeitsverteilungsfunktion der Elektronen sowie hiermit folgender makroskopischer Größen der Elektronenkomponente aus der nichtstationären Boltzmanngleichung unter Berücksichtigung elastischer und anregender Stöße, ausgehend von stationären Zuständen.

Neben der Darstellung der numerisch gewonnenen Ergebnisse wird aufbauend auf diesen ein physikalisches Verständnis der Gesamtdauer des Relaxationsvorganges, seiner Anfangsphase sowie des momentanen Ablaufes der Relaxation mittels Einführung normierter charakteristischer Zeiten erreicht. Ferner werden Bedingungen zur Charakterisierung der Relaxation nach quasisprunghafter Änderung des elektrischen Feldes bzw. bei quasistationärer Feldänderung als Grenzfälle der allgemeineren Betrachtungen formuliert.

Anhand dieser charakteristischen Zeiten wird in jedem Einzelfalle zu vorgegebenen elektrischen Feldverläufen eine Aussage über den Grad der Realisierung einer der Grenzfälle ermöglicht. Die Untersuchungen werden am Beispiel des schwachionisierten, nichtisothermen Neon‐Plasmas vorgenommen.
Zur mikrophysikalischen Beschreibung des schwachionisierten Säulenplasmas von Glimmentladungen in Stickstoff‐Neon‐Gemischen III. Bilanzierung des Säulenplasmas und Berechnung seiner inneren Parameter
Authors: Pfau S. , Winkler R.
Published: July 2007

Ausgehend von der Analyse der elektronenkinetischen Eigenschaften des Stickstoff‐Neon‐Gemisches [1, 2] werden für stromschwache Säulenplasmen solcher Gemische die Bilanzen der das globale Säulenverhalten bestimmenden Ionenarten und angeregten Spezies formuliert. Mittels einer simultanen Lösung dieser Bilanzen zusammen mit der Boltzmann‐Gleichung der Elektronen des Gemisches, der Strombilanzgleichung und der Quasineutralitätsbeziehung wird die Entladungsstrom‐ und Druckabhängigkeit des axialen Säulengradienten, des Ionisierungsgrades und der Konzentration der angeregten Neon‐Atome und der Ionenarten für beliebige Zusammensetzung des N2‐Ne‐Gemisches berechnet. Bei der Ermittlung der Strom‐ und Druckabhängigkeit der Säuleneigenschaften werden die Bereiche 0,5 mA‐13,5 mA und 0,37 Torr‐3,7 Torr erfaßt. Ein für den axialen Säulengradienten vorgenommener Vergleich theoretisch berechneter Ergebnisse mit dem Experiment führt zu einer guten Übereinstimmung im Gebiet störungsfreier Säulenplasmen.

Große Bedeutung in der Ladungsträgererzeugung kommt in dem untersuchten Gemisch der Ionisation der Stickstoffmoleküle durch Stöße mit den metastabilen Neonatomen (Penning‐Ionisation) zu. Ausgehend von experimentell bestimmten Säulengradienten wurde die Stoßrate zp für die Penning‐Ionisation ermittelt. Es ergab sich ein gegenüber früheren Untersuchungen [9] etwas kleinerer Wert von zp = 3 · 10−11 cm3 s−1.
Modulation of Ion‐Cyclotron Turbulence by Low‐Frequency Perturbations in a Magnetized Plasma
Authors: Tagare S. G. , Zhelyazkov I.
Published: July 2007

We consider nonlinear coupling of ion‐cyclotron turbulence with low‐frequency fast magneto‐acoustic perturbations across the external magnetic field in a magnetized plasma. It is found that such coupling leads to instability. The growth rate and the threshold of this instability are calculated.
Zwei Verfahren zur Lösung der Abelschen Integralgleichung und zur Berechnung der radialen Volumenstrahldichte
Authors: Valentini H.‐B.
Published: July 2007

Two methods for the calculation of the emission coefficient distribution from the side‐on radiance distribution in an optically thin plasma were elaborated. Firstly, a method for recursive solution of the Abel integral equation was derived. The formulas given by Frie were simplified. In a second method a polynomial was fitted to the data points and then the integral equation was solved analytically. Fluctuations of the solution increase with rising number of pivot points or with rising degree of polynomial and not only with rising scattering of the data points. The first method provides good results for a relatively small number of pivot points. In many cases the second method provides useful results with an even polynomial of the sixth or eighth degree and the numerical effort is slight.
Experimentelle Bestimmung der Entladungskenngrößen Temperatur und Druck eines wandstabilisierten Xenon‐Hochdruckplasmas
Authors: Worm M.
Published: July 2007

Aus der über den Querschnitt gemessenen Verteilung der Dichte und dem radialen Emissionskoeffizientenverlauf der kontinuierlichen Strahlung einer bei 35 A betriebenen Xenon‐Hochdruckentladung vom Typ XF 3000 werden das Temperaturprofil dieses Plasmas und der Brenndruck im Entladungsrohr berechnet. Da der Druck in einem solchen Brenner bisher nicht bestimmt werden konnte, war ein direkter Vergleich mit Angaben aus anderen Arbeiten nicht möglich. Auf indirektem Wege gelang es jedoch, unsere Ergebnisse zu bestätigen.

Die Fehlerdiskussion beschäftigt sich insbesondere mit jenen Fehlern, die bei der Bestimmung der Dichte nach dem Röntgenabsorptionsverfahren entstehen können. Es ist auf der Grundlage dieser Analyse möglich, die Ursachen dafür aufzudecken, daß aus früheren Dichtemessungen zu niedrige Temperaturen berechnet wurden.
Self‐Gravitational Instability of a Stratified Viscous Hall‐Plasma of Finite Conductivity
Authors: Chhonkar R. P. S. , Bhatia P. K.
Published: July 2007

The hydromagnetic instability of a self‐gravitating, incompressible, finitely conducting, viscous plasma of varying density has been investigated. The ambient magnetic field is assumed to be uniform and vertical. It is first shown that a variational principle characterizes the problem. The proper solutions have then been obtained, by the variational methods, for a semi‐infinite plasma contained between two horizontal free boundaries. The dispersion relation has been solved numerically It is found that the growth rate of the unstable mode increases with the magnetic resistivity and with the Hall‐currents while it decreases with the increasing viscosity. The influence of the effects of magnetic resistivity as well as of Hall‐currents is, consequently, destabilizing on the dynamic instability of a self‐gravitating stratified plasma. Viscosity has, however, a stabilizing influence on the growth rate of the disturbance.
Hall Currents and the Rayleigh‐Taylor Instability of a Finitely Conducting Plasma in the Presence of Coriolis Forces
Authors: Sankhla V. D. , Bhatia P. K.
Published: July 2007

We have studied the effect of rotation on the development of Rayleigh‐Taylor instability of an incompressible, viscous, Hall, finitely conducting plasma of variable density. The solution is developed, through variational methods, for a semi‐infinite plasma in which the density varies exponentially along the vertical. It is found that the system is unstable for all wave numbers when the effects of magnetic resistivity are included. The effects of coriolis forces and viscosity on the growth rate of the unstable system are found to be stabilizing while that of Hall currents is destabilizing. Finite conductivity affects the growth rate of the unstable mode differently for the smaller and larger values of the wave numbers, destabilizing for the waves of large wave length and stabilizing for waves of small wave length.
Finite Ion Temperature Effects on Strongly Non‐Linear Ion Acoustic Solitons
Authors: Baumgärtel K.
Published: July 2007

The influence of finite ion temperature on the properties of strongly non‐linear ion acoustic solitary waves is discussed within the framework in Sakanaka's ion fluid model.
Mikrophysikalische Bestimmung elektronenkinetischer Kenngrößen im binären Molekül‐Mischplasma von Stickstoff und Wasserstoff. II. Elektronenstoßfrequenzen für die Anregung und Ionisierung langlebiger elektronischer Molekülzustände und die Energieverlustraten der Elektronenkomponente des Mischplasmas
Authors: Michel P. , Pfau S. , Winkler R.
Published: July 2007

In diesem zweiten Teil werden in Fortführung der Untersuchungen in [1] die Ergebnisse einer mikrophysikalischen Berechnung der Elektronenstoßfrequenzen für die Anregung und Ionisierung langlebiger elektronischer Molekülzustände und der Energieverlustraten der Elektronenkomponente bei den elastischen Stößen, der Schwingungsanregung, der elektronischen Anregung, der Dissoziation und der Direktionisation der Moleküle im N2–H2‐Mischplasma mitgeteilt und diskutiert. Die Untersuchungen beziehen sich auf ein schwachionisiertes homogenes und stationäres Mischplasma und wurden für den Bereich 6–100 V/(em Torr) des auf den Totaldruck bezogenen elektrischen Feldes und für beliebige Zusammensetzung des Gemisches ausgeführt.
Zur Problematik transversal eingeengter, stromstarker Lichtbögen
Authors: Rothhardt L.
Published: July 2007

The 1‐dimensional 2‐zone theory of a quiet, high current are in a narrow slit chamber, first formulated by FRIND, is extended. Central temperature resp. heat flux potential and voltage/current characteristic are evaluated in a resistor stabilized regime. The influence of finite extension of the flat are (in 2nd dimension) on conductivity and temperature distributions as well as thermal are constant is treated. The formation of a highly conducting core sheath is modelled in a flat 3‐zone description. The limitations of 1‐dimensional flat are theory are discussed in this context.
Interferometrische Bestimmung der Gastemperatur in der Stickstoffniederdruckentladung
Authors: Krysmanski K. H. , Walter W.
Published: July 2007

A Michelson‐interferometer in combination with a He‐Ne‐laser was used to determine the gas temperature in a nitrogen low pressure gas discharge. With this method the radial temperature profile could be measured to about 96% of the tube radius. Moreover rotational temperatures were measured with a 2 m‐grating spectrograph from the spectrum of N2‐ and N2+‐bands. In the range from 4 to 10 torr and 25 to 100 mA gas temperatures between 460 and 890 K were measured with the belonging rotational temperature from 620 to 1170 K. At pressures below 10 torr a difference of the rotational temperatures from the first negative and the second positive system was found. A qualitative consideration on the mechanism of the radial heat conductivity in the positive column was added.
[Russian Text Ignored]
Authors: [Russian Text Ignored]
Published: July 2007

A nonlinear theory of the interaction of an external pump field with ion‐acoustic and h.f. surface waves in a plasma layer with inhomogeneous boundary regions is presented for the case, when the pump field frequency is less than the electron plasma frequency. The evolution of the parametrically excited turbulence and its stationary state are both analytically treated and numerically demonstrated. Dependent on the pump field strength, two mechanisms are to be distinguished: (i) nonlinear generation of damped ion‐acoustic harmonics, (ii) cascade excitation of secondary eigenmodes by growing surface oscillations. At only slight overthreshold values, mechanism (i) is responsible for the occurence of the steady state, whereas, for higher pump field strength, the wave amplitudes as well as their saturated levels are mainly determined by mechanism (ii).
Effect of Flat Top Electron Distribution on the Turbulent Heating of a Plasma
Authors: Jain H. C. , Sharma S. R.
Published: July 2007

Expressions for anomalous resistivity and energy transfer collision frequency in the presence of ion‐acoustic instability have been derived. It is found that the rapid electron heating may be attributed to the flattening of the top of the electron distribution function to a high degree. Results are valid under the situation when krrc « 1 where τc is the correlation time for turbulence.
Resonanzstreuung an einer Argon‐Hochstrom‐Niederdruckentladung
Authors: Schubert M.
Published: July 2007

A resonance scattering experiment in an argon high‐current low‐pressure discharge is described. The saturation intensity has been measured for several discharge conditions and compared with a simple balance equation model for the transition 4p 2D3/2 ‐ 4s 2P3/2 of the argon ion.
An Example of Negative Wave Momentum Density in Plasma
Authors: Petržilka V. A. , Wallis G.
Published: July 2007

It is shown that a negative wave momentum density in plasma may be found for positive values of the group velocity.
On the Polishing Effect of Nanosecond Discharges in Vacuum
Authors: Jüttner B.
Published: July 2007

When a metal surface in ultra high vacuum is subjected to electric discharges with a sufficiently short duration the surface becomes perfectly smooth. This polishing is caused by the inertia of the molten metal within a cathode spot that prevents the formation of a crater by acceleration of the liquid. The present paper reports an investigation of this phenomenon in dependence on the discharge parameters. The effect was found to be determined by the pulse duration, it occurs with pulses of less than 10 nanoseconds. But also long discharges of 500 ns show a polishing if the current rise rate is below a critical value (0.5 — 1 A/ns), depending on the cathode material. Thus long discharges consist of elementary steps of about 10 ns duration, in accordance with the formation time of cathode craters. The polishing effect causes an abrupt decrease of the breakdown probability of rectangular high voltage pulses from one to zero at a critical pulse duration.
Ionenschallinstabilitäten in Edelgas‐Gleichstromentladungen bei niedrigen Drücken. I. Meßanordnung und experimentelle Ergebnisse
Authors: König A. , Leven R.
Published: July 2007

An experimental study of self‐excited ion acoustic waves with wavelengths greater than the radius of the discharge tube in a de‐low pressure column is presented. The propagation of this type of waves was observed over a pressure range of 5 · 10−4 torr ≦ p ≦ 10−1 torr and currents of 0,02 A ≦ i ≦ 0,6 A in various gases (argon, neon, helium, and hydrogen) in cylindrical glass tubes with diameters of d = 2;4 and 6 cm.

The Dispersion behaviour and the existence range were measured in dependence of the internal parameters of the discharge (characteristic velocities and collision frequencies) and the geometry of the discharge tube. It is shown, that the existence range depends not only on gas pressure and current but is influenced also by the geometry of the discharge tube. The minimum wavelengths which belong to the upper cut‐off frequencies correlate with the radius of the discharge tube at currents higher than i ∼ 0,2 A and increasing pressure.
Nichtstationäre Reflexion und Reemission von Wellen bei Herausbildung elektromagnetischer Strukturresonanzen im Plasma
Authors: Andrejew N. E. , Gradow O. M. , Sünder D.
Published: July 2007

The nonstationary resonant reflectivity of a density profile is studied which consists of two homogeneous overcritical layers, separated by a vacuum region whose width increases linearly in time. Analytical expressions are derived for the time dependence of both the reflexion coefficient and the cavity field in the case of normal incidence. If the configuration passes through a structure resonance, where the eigenfrequency of the density cavity coincides with the frequency of the external wave, the cavity field is strongly enhanced. The temporary formation and the subsequent decay of this resonant field leads to oscillations of the reflexion coefficient. In the case of a loss‐less plasma it may reach the extreme values |R| = 0 |R| ≈ 3 and the moving plasma configuration temporarily acts as an energy storage (|R|2 < 1) or an emitter (∣R∣2 > 1).
Unipolarbögen
Authors: Hantzsche E.
Published: July 2007

Unipolarbögen haben eine erhebliche Bedeutung erlangt als ergiebige Quelle von Verunreinigungen in Tokamak‐Plasmen.

Nach einer Definition von unipolaren und plasmainduzierten Entladungen werden die hauptsächlichen Eigenschaften der Raumladungsschicht zwischen Plasma und Wand sowie die Existenzbedingungen von Unipolarbögen betrachtet (notwendiger Spannungsabfall, Strombilanz). Aus einem einfachen Modell, das eine Überlagerung der beiden völlig verschiedenartigen Plasmen — des Tokamak‐Plasmas und des katodischen Bogen‐Brennfleckplasmas — berücksichtigt, ergibt sich die radiale Abhängigkeit der Stromdichten und Spannungen zwischen Plasma und Wand sowie der Plasmaparameter. Daraus folgt, daß in typischen Fällen die Anodenregion eine ringförmige Zone ist in einem Abstand r > b vom Katodenbrennfleck, mit 0,3 cm ≲ b ≲ 1 cm, und daß der Dichteabfall des Bogenplasmas n ∼ r−μ einen Exponenten im Bereich 2 ≲ μ ≲ 3 erfordert wegen der Strombilanz‐Bedingung (Bogenstrom = Rückflußstrom). Außerdem werden einige thermodynamische Aspekte (Unipolarbögen als eine Form dissipativer Strukturen), das Zündproblem, der Einfluß von Magnetfeldern, die diagnostischen Probleme und die Möglichkeiten der Simulation kurz diskutiert.
On the Interaction of an Alternating Electrical Field with a Magnetized Fully Ionized Plasma
Authors: Burdujan I. , Zoler D.
Published: July 2007

The electron distribution function for a plasma interacting with an alternating electric field is studied, without using the Fourier expansion in terms of time. For this distribution function a more complete expression was deduced. Also the expressions for the current density are computed. Recurrently, we find the general form of the solution for our problem. A dependence of the current density of the form E and EEE was obtained. This dependence being characteristic to the nonlinear interaction of the waves in a plasma with the collision frequency depending on the velocity.
The Theory of the Positive Column at Low Pressures Including Space‐Charge Effects, the Radial Variation of the Ion Temperature, and the Charge Exchange
Authors: Valentini H.‐B.
Published: July 2007

The theoretical description of the positive column at low gas pressure is improved by taking into account both the space charge sheath at the wall and the radial variation of the radial ion temperature. Assuming the ion temperature being zero on the axis only, simplified moment equations up to the third order are used. Under free‐fall conditions and by taking into account the charge exchange between ions and atoms the spatial distributions of the number densities and of the drift velocities of the ions and of the electrons, of the radial ion temperature, and of the electric potential are calculated. Moreover, the electron temperature is given. It has been found out that at low gas density the charge exchange causes a high ion temperature and not only an increase of the neutral gas temperature, where the electron collisions do not remarkably contribute to the heating of the ion gas.
Untersuchungen zum axialen Gaspumpeffekt bei Edelgas‐Niederdruckentladungen hoher Stromdichte
Authors: Ebert W.
Published: July 2007

Elektrophorese und Kataphorese sind die Ursachen für die Entstehung von Druckgradienten in Niederdruckentladungen. Ausgehend von den Ergebnissen von Leiby und Oskam wird ein Ausdruck für den axialen Druckgradienten abgeleitet. Die Parameter des Entladungsplasmas sind mit Hilfe eines halbempirischen Modells einer Hochstrom‐Niederdruckentladung in Ab‐hängigkeit von der Stromdichte, dem Rohrradius und dem Gasdruck berechnet worden.

In einem Entladungsrohr mit enger Kanalbohrung (R = 0,1 cm, l = 8 cm; Argon, Krypton) sind Druckdifferenzen gemessen worden. Die experimentellen Werte und die numerischen sind von der gleichen Größenordnung.
The Coupling of Magnetoacoustic Waves Propagating Along the Direction of Stratification of a Viscous Plasma Situated in a Variable Magnetic Field
Authors: Gazi R.
Published: July 2007

The components of the coupling matrix were evaluated, corresponding to the coupling of magnetoacoustic waves in a non‐ideal plasma for the physical situation modelling the terrestrial ionosphere.
Critical Current of the Ionization Waves and Anomaly of the Positive Column in an Axial Magnetic Field
Authors: Sato M.
Published: July 2007

Influences of an axial magnetic field on the ionization wave and the positive column in rare gas discharges are studied experimentally. The upper critical current Ic for the appearance of ionization waves in the magnetic field B is newly found. As B is gradually increased, the value of Ie slightly increases from the Pupp's value and after passing a prominent maximum, finally become very small. In addition an anomaly takes place in the axial electric field E of the positive column stable for helical instabilities. With increasing the magnetic field the value of E goes through a weak maximum before decreasing. It is concluded that this anomaly, apparently incompatible with classical diffusion theory, is closely related to the appearance of ionization waves in the positive column.
Kinetic Description of the Stationary Band‐Like Weakly Turbulent Beam Discharge Plasma in Hydrogen. I. Basic Equations — Numerical Approach — Ionization and Dissociation Budget
Authors: Winkler R. , Michel P. , Pfau S. , Starykh V. V. , Wilhelm J.
Published: July 2007

On the basis of the electron Boltzmann equation and of the balances for the charge carriers (e, H+, H2+, H3+), the H‐atoms and the metastable H(2s)‐atoms for the H/H2‐mixture the behaviour of the weakly turbulent, band‐like electron‐beam discharge plasma in hydrogen has been calculated taking into account the main collision and transport processes. In dependence of the normalized discharge length, the life time of the neutral particles in the band‐like plasma and the electron beam generated turbulence energy density the ionization and dissociation budget and in particular the most important electron‐heavy particle collision rates, which appear in the balance equation system, are investigated in the present part of our paper. In a second part the results related to the budget of the ions and the metastable atomic state will be reported and an analysis of the main processes in the balances will be made.
Plasma Beam Discharge in Carbon Dioxide
Authors: Gadeev K. K. , Zhuzhunashvili A. I. , Ivanov A. A. , Nikiforov V. A. , Serverny V. V. , Shapkin V. V. , Neumann W. , Schmidt M. , Schulz K.‐D.
Published: July 2007

The paper deals with the dissociation of carbon dioxide in nonequilibrium plasma of a stationary plasma‐beam discharge. Experimental results of spectroscopic and probe measurements of plasma parameters are given. Moreover, a mass‐spectrometric analysis of gaseous products of the chemical reactions is presented. In addition the measurement of the deposition rate of solid products by means of a quartz oscillator is described.

The results show that plasma beam discharge is an effective tool for inducing plasma‐chemical reactions.
Unipolar Arc Tracks on Stainless Steel
Authors: Datlov J. P. , Guile A. E. , Jüttner B.
Published: July 2007

Craters caused by unipolar arcs on stainless steel depend strongly on surface conditions. There are three diameter distributions: Small craters (∼ 0.3 μm) for oxidised surfaces, larger craters (∼ 2 μm) for moderately cleaned areas, and very large craters (∼ 20 μm) for clean surfaces. These values are compatible with Joule heating models of crater formation. Compared with other metals of interest, stainless steel shows the largest craters.
Kinetic Description of the Stationary Band‐Like Weakly Turbulent Beam Discharge Plasma in Hydrogen II. Budget of Ions and Metastables — Analysis of the Balance Equation System
Authors: Winkler R. , Michel P. , Pfau S. , Starykh V. V. , Wilhelm J.
Published: July 2007

In the first part [1] of our paper a kinetic model for the band‐like beam discharge plasma in hydrogen was derived, numerically obtained results on the ionization and dissociation degree were presented and a detailed explanation of the influence of the electron kinetic properties on the macroscopic plasma behaviour was given. Continuing these investigations, we now report and discuss the results on the ion‐ and metastable atom‐budget. On this basis an analysis is made of the resulting balance equation system with a view to finding the most important physical processes, and a simplified equation system is derived which allows to interpret the essential features of the macroscopic plasma properties.
Enhancement and Suppression of the Plasma Oscillation by an Externally Launched Oscillation
Authors: Amemiya H.
Published: July 2007

In a beam‐plasma system generating a rather coherent oscillation under a quiescent and stable plasma condition, interaction between the oscillation and an artificially launched oscillation is investigated. It is shown that the latter exerts both synchronization and cross‐modulation effects on the former. An oscillator equation including nonlinear terms of the van der Pol and Mathieu equations (V‐M equation) is used to describe the phenomena. It is found that the equation gives a fair account of them, though phenomenological. Conditions for enhancement of the oscillatory energy and for noise suppression in a plasma are given.
[Russian Text Ignored.]
Authors: [Russian Text Ignored.] O. M. , [Russian Text Ignored.] [Russian Text Ignored.].
Published: July 2007

The nonlinear penetration of an electromagnetic wave through an overdense plasma layer due to the excitation of parametric instabilities is studied. The quasistatic h.f. surface wave and the ionacoustic wave, both parametrically growing, generate a nonlinear current which also exist beyound the linear skin length of the incident electromagnetic wave. This current leads to an exponential amplification of the electromagnetic wave amplitude in the layer. The growth rate of this process depends on the overthreshold value of the external wave intensity and the thickness of the layer. The saturation level of the transmitted wave amplitude is estimated for the case, when the instabilities are stabilized by generation of ion‐acoustic harmonics.
Wall Charge Behaviour in External Electrode Gas Discharges
Authors: Kindel E. , Arndt R.
Published: July 2007

Measurements have been accomplished of wall charge distributions and total charges which were generated in Ne—N2‐filled discharge cells with insulated electrodes under the impact of ultraviolet irradiation and of bipolar pulse sequences. The non‐self‐maintained pulse discharge, generated by means of UV‐light, leads to a build‐up or destruction of wall charges in dependence of the efficient gap voltage. In the course of the discharge sequences wall charge transients, similar to those in ac plasma displays, are produced. Discussion of wall voltage transfer curves shows the dependency of discharge activity in the gap on the charging conditions of the insulating surfaces, placed in front of the electrodes.
Nachweis von radikalischen Zersetzungsprodukten in CCl4‐Entladungen mit der EPR‐Spektroskopie
Authors: Breitbarth F.‐W , Tiller H.‐J.
Published: July 2007

Among the dissociation products of a r.f. discharge in CCl4‐vapour the radicals CCl3 and Cl2‐ have been identified by EPR‐spectroscopy after condensation at 80 K.

The gas‐phase reaction CCl3 + O2 → CCl3OO has been used to estimate the CCl3 concentration to be approximately 5 · 1013 radicals/cm3 at p = 55 Pa. The life‐time of CCl3‐radicals is governed by the rate of desactivation of some exited species (eg. CCl4*) via magnified image.

At a pressure p = 55 Pa a half‐life of CCl3‐radicals of τ1/2 = 80 ms has been found.
Properties of the Collision Operators of the Electron Boltzmann Equation for a Weakly Ionized Plasma. I. Representation and General Properties
Authors: Bartolomäus G. , Wilhelm J.
Published: July 2007

In the kinetic theory a great variety of physical systems is investigated by means of Boltzmann‐like equations. This approach is used for neutral gases, neutron as well as radiation transport, plasmas etc. For many problems the knowledge of the properties of the collision operators is of great importance, especially if eigenvalue problems occur.

The paper presents an investigation of the properties of the collision operators of the Boltzmann equation covering elastic, exciting and deexciting processes in a weakly ionized plasma. First, a short survey of the importance of eigenfunctions and eigenvalues in the kinetic theory of various systems is given. Then, properties of the outscattering operator as dependent on the course of the differential cross section are considered. Finally, for the inscattering operator such properties as selfadjointness and rotational invariance are investigated in detail. These considerations provide the basis for the proof of compactness and for first conclusions on the spectral properties of the collision operators in the second part of this paper.
Zu einigen technischen Problemen des Plasmas bei elektrischen Isolierungen
Authors: Mosch W.
Published: July 2007

Für die elektrische Isoliertechnik sind Gasentladungen von großer Bedeutung. Die technische Aufgabe besteht darin, ein Plasma bei allen im praktischen Betrieb auftretenden Beanspruchungen (elektrisch, thermisch, mechanisch, chemisch usw.) zu vermeiden. Um konstruktive und technologische Hinweise für Entwicklung, Konstruktion, Fertigung und Betrieb von elektrischen Isolierungen geben zu Können, müssen deshalb die physikalischen Erscheinungen beim Gasdurchschlag bekannt sein.

An Hand von Forschungsergebnissen vom Durchschlag von Hochspannungsisolierungen mit Schwefelhexafluorid und vom Überschlag längs der Oberfläche von Freileitungsisolatoren wird die Arbeitsweise des Technikers demonstriert.
N2(B3IIg) Quenching by Ethanol
Authors: Musa G. , Bîrna I.
Published: July 2007

The reaction rate values for the molecular nitrogen B3IIg state quenching by ethanol for vibrational quantum numbers v′ = 4–12 have been evaluated from the change of N2 first positive system spectrum at ethanol addition to a high speed, microwave produced, plasma flow. The wall influence is avoided using a 0.9 m large reaction chamber. Computed N2(B3IIg) quenching rate values are comprised between 0.9 × 10−10 and 1.4 × 10−10 cm3 · s−1, being smaller than the corresponding gaskinetics rate.
Set Simulation of a Turbulent Arc by Monte‐Carlo Method
Authors: Zhukov M. F. , Devyatov B. N. , Nazaruk V. I.
Published: July 2007

A method of simulation of turbulent are fluctuations is suggested which is based on the probabilistic set description of conducting channel displacements over the plane not nodes with taking into account the turbulent eddies causing non‐uniformity of the field of displacements. The problem is treated in terms of the random set theory. Methods to control the displacements by varying the local displacement sets are described.

A local‐set approach in the turbulent are simulation is used for a statistical study of the are form evolution in a turbulent gas flow. The method implies the performance of numerical experiments on a computer. Various ways to solve the problem of control of the geometric form of an are column on a model are described. Under consideration are the problems of organization of physical experiments to obtain the required information for the identification of local sets. The suggested method of the application of mathematical experiments is associated with the principles of an operational game.
Temperature Field Measurements of the Electric Arc Plasma in a Longitudinal Magnetic Field
Authors: Melnikova T. S. , Pickalov V. V.
Published: July 2007

Two methods are described to determine local parameters of the unsteady asymmetric plasma. The basis of one method is the parametric approach. This method is used to determine plasma parameters in the case when an assumption can be made on the shape of the intensity isolines. The temperature field was calculated according to the intensity distributions in X direction obtained simultaneously from two lines of sight. The second method was applied for measurements in arbitrary plasma configuration. In this case the temperature fields were calculated according to measurements from lines of sight simultaneously, and the obtained data were used in the Radon transformation inversion.
Schnell rotierender Lichtbogen als spektroskopische Lichtquelle
Authors: Kranz E.
Published: July 2007

Ein magnetisch schnell bewegter Lichtbogen bildet einen geschlossenen Plasmakegel oder Plasmaring zwischen zwei konzentrisch angeordneten Elektroden. In dieses Plasma können Aerosole oder Suspensionen optimal mit geringen Trägergasdurchsätzen eingebracht und im Plasma zur Emission angeregt werden. Die bisher angewendeten und erreichten Daten sind: Bogenstromstärke 5…︁20 A, Magnetfeldstärke 104…︁4 · 105 A/m, magnetische Induktion 0,1…︁0,3 T, Rotationsfrequenz 8…︁15 kHz, Trägergas Luft oder Argon maximal 0,5 1/min, Intensitätssteigerung für CuI‐Linien bis 100fach. Weitere Anwendungen sind für Speziallampen und die Lichtbogendiagnostik möglich.
Laser‐Generated Plasmas as X‐Ray Sources in the keV‐Range
Authors: Wallis G.
Published: July 2007

This report will give an introduction to the X‐line emission processes in laser‐generated plasmas according to a plasma physical point of view. After a short discussion of the experimental results using laser pulses in the range of ≲ 10 J and irreadiances of 1 to 100 MW/cm2 and of first conclusions about the temperature scaling and the dependence of the emission concerning the atomic number of the target material some models of laser‐generated plasmas are analysed. The simple hot‐spot model neglects any hydrodynamics and only solves for the rate equations. We discuss the underlying collisional‐radiative model and evaluate the numerical results of a more complete model for the spatial and temporal plasma evolution including the hydrodynamics. The applications of such plasmas as small, strong, short sources of X‐rays in the keV range is discussed with regard to the lithographic replication of sub‐μm structures and to the EXAFS spectroscopy. Laser‐generated plasmas are compared with conventional X‐ray tubes (with rotating anode) and with synchrotrons. The question of amplified spontaneous emission in the XUV range (superradicant X‐ray sources) is only shortly touched upon. In conclusion some comments are given to the recoil momentum effects of the ablating plasma on the target are given (rocket model).
Untersuchungen zu den Existenzbereichen und Typen von ac‐Entladungen III. Der Übergang zu reinem Neon und das Bistabilitätsverhalten der einzelnen Typen
Authors: Zahn R. J. , Müller S.
Published: July 2007

The present paper investigates the discharge modes in neon. The Ne‐discharge is shown to be sensitively influenced by impurities or small admixtures. If the Ne‐filling is not pure enough, pulse mode and continuous mode occur in the same way as in a NeN2 mixture. But below a nitrogen content of 0.01% the shift of the transition frequency between the pulse mode and continuous mode disappears. If the measurements were carried out in pure neon, the non‐bistable continuous mode could not be observed, which indicated that the main ionization mechanism, the Penning ionization, had vanished. Instead, in the corresponding parameter range a bistable discharge occurred. This discharge, representing the quasiglow mode, is more intense and the discharge current persists for the whole half cycle.

Furthermore, the present paper investigates the wall voltage build up. The charge‐transfermethod was extended to the quasiglow mode and the continuous mode. The observed changes in the charge‐transfer‐curves can be explained by the different discharge mechanisms.
Cathode Heating by Vacuum Arcs: A Survey
Authors: Jüttner B.
Published: July 2007

Theoretical predictions about heat sources, power dissipation and heating time scales are compared with available experimental data. It is concluded that the heating process must have a much faster time scale than quasi‐stationary heat conduction. This can be achieved only by ion impact heating. A special model is discussed (thin layer heating) which explains the high power dissipation within the cathode as well as the short heating times.