bluuebunny/crossref_metadata_2025 huggingface dataset:
Bestimmung von Elektronen‐ und Ionendichten sowie von Temperaturen im Xenon‐Hochdruckplasma aus den Elektronen‐und Ionenstoßverbreiterungen von starkeffekt‐empfindlichen Xenon‐Linien
Authors: Pranoto Soemarmo , Schulz Paul
Published: July 2007

Elektronendichte und Temperatur werden im Plasma der Säule einer Xenon‐Hochdruckentladung aus den Elektronen‐ und Ionenstoßbreiten der Xenon‐Linien 4624 Å und 4671 Å bestimmt und verglichen mit Werten, die aus den Trägerstoßbreiten der Quecksilberlinie 5770 Å im gleichen Plasma erhalten werden, wenn ein geringer Zusatz von Quecksilber zum Xenon‐Grundgas gegeben wird. Gemessen wurde bei einem Druck von 22 atm bei Stromstärken von 15 A bis 30 A. Die Elektronenkonzentrationen ergaben sich zu rund 3,7 · 1016 cm−3 bei 15 A bis 7,0· 1016 cm−3 bei 30 A, die Temperaturen von 7340°K bis 7800°K.
Zum Mechanismus der positiven Niederdrucksäule im Grenzfall kleiner Elektronendichten. I. Allgemeine Übersicht
Authors: Rutscher Alfred
Published: July 2007

Es wird die positive Niederdrucksäule unter Diffusionsbedingungen für den Fall untersucht, daß der Einfluß der Coulomb‐Wechselwirkung auf die Energieverteilungsfunktion der Elektronen zu vernachlässigen ist. Der vorliegende Teil I illustriert die Verhältnisse in stationären, ungeschichteten Edelgasentladungen anhand eines einfachen Modellbeispieles.
Quantenstatistik des Hochtemperatur‐Plasmas im thermodynamischen Gleichgewicht
Authors: Ebeling W. , Hoffmann H. J. , Kelbg G.
Published: July 2007

High temperature plasmas are investigated on the basis of quantum theory. A new method for the calculation of the thermodynamic properties is developed. According to the method of Morita effective potentials are introduced. They permit the evaluation of the partition function with the well‐known formalism of classical statistical mechanics. The first corrections added to Debye's limiting law of the free energy are expressed by the two particle Slater sum S2(r). A Bloch equation for S2(r) is derived and is solved in the Fourier representation by a development according to the interaction parameter ζ = e2/kTλ, λ being the thermal wavelength. The effects of symmetry are taken into account. The free energy is calculated explicitely up to the order of ζ2.

In the case of small concentrations our results agrees with that derived by Trubnikow and Elesin. Effects of symmetry neglected, up to the order of ζ2 the formula of DeWitt is obtained.
Quantenstatistik des Hochtemperatur‐Plasmas im thermodynamischen Gleichgewicht. II. Die freie Energie im Temperaturbereich 106 bis 108 °K
Authors: Hoffmann H. J. , Ebeling W.
Published: July 2007

In this paper the theory, given in part I, is continued. In the region of temperatures and density, where the fundamental lengths of the plasma are ordered as \documentclass{article}\pagestyle{empty}\begin{document}$ \lambda _{ii} < {\textstyle{{e^2} \over {kT}}} < \lambda _{ee} $\end{document} and where neλ ≪ 1, quantum corrections to the classical Debye‐Hückel free energy of an electron‐ion‐plasma are calculated explicitely. Here ne is the electron density; λee and λii are the thermal wavelengths of the electrons and ions, respectively. The above assumptions are valid for temperatures between 106 and 108 °K and electron densities ne < 1025 cm−3. The effects of symmetry are taken into account. The relation between our results and those derived by DeWitt, Trubnikow and Elesin is discussed.
Ionisationsbedingte Säulenkontraktion. II. Die Mitteldrucksäule mit inhomogener Elektronentemperatur
Authors: Wojaczek Karl
Published: July 2007

An Hand von Modellrechnungen, die sich am Beispiel der Argon‐Entladung orientieren, wird gezeigt, daß die radiale Inhomogenität der Elektronentemperatur in der Mitteldruckentladung zwar bei höheren Drücken und Stromstärken eine merkliche Rolle im Entladungs‐mechanismus spielen kann, daß sie jedoch für die relativ stark kontrahierte Entladungssäule keine wesentliche Bedeutung besitzt.
Zur nichtlinearen Theorie der Strahl‐Plasma‐Wechselwirkung. II. Das asymptotische Verhalten des Systems
Authors: Leven Ronald
Published: July 2007

The asymptotic behavior of an amplifying beam‐plasma‐system for great distances x from the point where the beam enters the plasma is investigated on the basis of an expansion in powers of the electric field amplitudeA1. It is shown, that a necessary condition for approaching a steady state with a constant wave amplitude is that the first 2N−1 derivations of the distribution functionf0(u) at the pointuφvanish if the approximation is toN‐th order inA1. Further it is demonstrated, that an approximation including the third power ofA1involves the important physical effects as mode coupling and wave amplitude saturation, and that fifth order correction terms are unimportant, if the beam parameters are chosen so that the difference between beam and phase velocities is not to small. To illustrate this point some numerical examples are considered.
[Russian Text Ignored]
Authors: [Russian Text Ignored]  , [Russian Text Ignored]
Published: July 2007

Some aspects of the theory of fluctuating microfield in a system of charged particles are considered. The question concerning regions of validity for Holtsmark‐like and Gauss‐like microfield distributions in a rarefied and a dense plasma is discussed. The influence of finite dimensions of particles (test particles as well as field particles) on the microfield distribution is investigated. Expressions for a “dynamic” (two‐time) generalization of the Holtsmark distribution are obtained for limiting cases. By methods of microfield theory certain formulas for the fluctuations of the electric charges within a finite volume of an electrolyte are derived too.
Die kontinuierliche Emission von Argon bei hohen Drücken
Authors: Gall D. , Riemann M.
Published: July 2007

Mit einem Hochdruckkaskadenbogen wird der spektrale Emissionskoeffizient von Argon in Abhängigkeit von dem Druck (1, 4, 7 und 12 at) und der Temperatur experimentell ermittelt und mit dem theoretisch bestimmten Emissionskoeffizienten verglichen. Für das Rekombinationskontinuum ergibt sieh eine unbefriedigende Übereinstimmung von Theorie und Experiment. Aus dem Verhältnis der Kontinuums‐ zur Linienintensität werden Aussagen über den Verlauf der effektiven Ionisierungsspannungserniedrigung für das Kontinuum gemacht. Die Korrekturfaktoren § für das Rekombinationskontinuum, die die Abweichung des klassisch‐korrespondenzmäßig vom quantenmechanisch berechneten Emissionskoeffizienten angeben, werden für drei Wellenlängen experimentell bestimmt.
Über ein weiteres Variationsprinzip im Zusammenhang mit kraftfreien Magnetfeldern
Authors: Schäfer D.
Published: July 2007

Im Anschluß an ein von Woltjer [1] diskutiertes Variationsproblem wird gezeigt: Die Euler‐Lagrange‐Gleichungen des Variationsproblems

equation image

mit der Nebenbedingung

equation image

wo H = rot A gesetzt ist, sind die Differentialgleichungen

equation image

der kraftfreien Magnetfelder mit variablem α. Die Nebenbedingung läßt sich für alle Felder H erfüllen, die keinen singulären Punkt mit H = 0 in dem betrachteten Volumen V haben.

In persuance of a variational principle discussed by Woltjer [1] it is shown that the Euler‐Lagrange‐equations of the variational problem

equation image

with the secondary condition

equation image

where H = rot A are the differential equations

equation image

of the force‐free magnetic fields with a variable scalar α. The secondary condition can be accomplished for all magnetic fields which do not contain singular points with H = 0 in the volume V under consideration.
Higher‐Order Temporal and Spatial Plasma Wave Echoes
Authors: Sauer K. , Bachmann P. , Wallis G.
Published: July 2007

The collisionsless Boltzmann equation is solved in two ways by the method of characteristics. The solution is used for an exact treatment of higher‐order temporal and spatial plasma wave echoes in the absence of steady external fields. The second‐order spatial echo is treated separately and analyzed numerically.
Quantum Statistical Second Virial Coefficient for Real Gases and Plasmas
Authors: Ebeling W. , Kraeft W. D. , Kremp D.
Published: July 2007

Using the resolvent representation of the binary Boltzmann operator the second virial coefficient is expressed by a contour integral over the Jost function of the two‐particle scattering problem. This new formula is useful for many general investigations and also for practical calculations if the Jost functions for the scattering problem are known. As special examples real gases with hard core potentials and fully ionized plasmas with Coulomb interactions are treated. For the plasma case the second virial coefficient is derived without approximations with respect to the interaction parameter. The contribution of the bound states to the free energy is discussed and compared with the effect of ionic association to the classical free energy and the conductivity.
Berechnung der Entladungsparameter einer Argon‐Säule bei mittleren Gasdrucken
Authors: Golubowsky Ju. B. , Kagan Ju. M. , Ljagustschenko R. I.
Published: July 2007

In der Arbeit wird eine Theorie der positiven Säule der Argonentladung bei mittleren Gasdrücken unter Berücksichtigung einer Abweichung der Verteilungsfunktion der Elektronen von der Maxwell‐Verteilung entwickelt. Aus den Bilanzgleichungen der Ladungsträger, der Elektronenenergie und des Entladungsstromes werden die inneren Entladungsparameter der positiven Säule E/p, n0 · R und Te berechnet.

Es wurde der radiale Verlauf der Elektronenkonzentration und der Intensität der Spektral‐linien erhalten.
Zum Stromtransport in Glühkatodenentladungen
Authors: Lunk A. , von Specht H.
Published: July 2007

In der vorliegenden Arbeit werden Sondenmessungen im Vergleich mit der Strom‐Spannungscharakteristik der Anodenglimmentladung sowie Abschätzungen über die raumladungsbegrenzte Dunkelentladung mitgeteilt.
Experimentelle Untersuchungen an wandernden Niederfelddomänen (T‐Schichten) in der positiven Säule von Gleichstrom‐ und HF‐Entladungen in Sauerstoff und Sauerstoff‐Stickstoff‐Gemischen
Authors: Sabadil Heinz
Published: July 2007

Die erzielten Ergebnisse bei experimentellen Untersuchungen an den wandernden Niederfelddomänen in der positiven Säule von Entladungen in O2 und O2—N2‐Gemischen untermauern die bereits in [1] gezeigte Analogie zu den Instabilitäten, die in Halb‐ und Photoleitern zu beobachten und durch eine fallende j(E)‐Charakteristik bedingt sind. Die Niederfelddomänen treten auf, wenn der reduzierte Druck größer als p · R ≈ 0,70 Torr · cm wird und die Entladungsstromstärke einen kritischen Wert unterschreitet. Jene Einsatzstromstärke steigt mit abnehmenden Entladungswiderstand. Dieses Resultat deutet darauf hin, daß für die Ausbildung der natürlichen Niederfelddomänen folgendes Instabilitätskriterium erfüllt sein muß: Der laufzeitabhängige negative Wirkwiderstand im kHz‐Frequenzbereich muß größer sein als der äußere Entladungsvorwiderstand. Durch Stromimpulse lassen sich bei großen Entladungsvorwiderständen oberhalb der Einsatzstromstärke künstlich schwach ausgebildete Niederfelddomänen anregen. Die bekannte Vergrößerung der O‐Konzentration durch eine N2‐Zumischung auf Grund der Herabsetzung der Rekombinationswahrscheinlichkeit für die O‐Atome auf der Rohrwand führt zu einer Herabsetzung des Konzentrationsverhältnisses der negativen Ionen zu den Elektronen, was einen Anstieg der mittleren Driftgeschwindigkeit der negativen Ladungsträger und damit — wie die Messungen zeigen — ein Anwachsen der Domänengeschwindigkeit zur Folge hat. Die mit der N2‐Zumischung verbundene Verschiebung der Grenzkurve für die Niederfelddomänen im p‐I‐Diagramm in Richtung höherer Drücke läßt sich verstehen, wenn man eine durch die Erhöhung der metastabilen Molekülkonzentration bedingte Herabsetzung der effektiven Schwellenenergie für die dissoziative Anlagerung annimmt. Abschließend wird über die Beobachtung von wandernden Niederfelddomänen in einer HF‐Entladung bei 1 MHz berichtet.
Die Zurückführung der Gleichungen eines rotationssymetrischen, statischen, inkompressiblen Plasmas von unendlicher Leitfähigkeit auf ein Randwertproblem
Authors: Schäfer D.
Published: July 2007

Die Gleichungen eines rotationssymmetrischen, statischen, inkompressiblen Plasmas mit unendlicher Leitfähigkeit sind äquivalent einer elliptischen Differentialgleichung für die Größe

equation image

wo p der Druck, ϱ die Dichte und Φ das Potential der äußeren Kräfte bedeuten. Diese Differentialgleichung enthält außerdem noch zwei willkürliche Funktionen von ξ.

Wennξϱ2+ξϱ2 < 0 ist, können die beiden willkürlichen Funktionen aus der Randverteilung von Hφ und H ⊥ (zum Rand senkrechte Komponente von H) gewonnen werden.
Quantum Statistical Fugacity Expansions for Partially Ionized Plasmas in Equilibrium
Authors: Bartsch G. P. , Ebeling W.
Published: July 2007

A derivation of screened fugacity expansions for nondegenerate Coulomb systems is given. Debye screening is taken into account by an iteration procedure. The fugacity expansion is applied to hydrogen plasmas. It is shown that the fugacity expansion of the pressure implicitely describes the ionization equilibrium.
Die Elektronenkinetik des schwachionisierten LORENTZ‐Plasmas im beliebig zueinander orientierten äußeren elektrischen und magnetischen Feld
Authors: Winkler R.
Published: July 2007

Die aus der Boltzmann‐Gleichung mit Zweierstoßintegralen zur Beschreibung elastischer und anregender Stöße der Elektronen mit den Neutralgasatomen folgende Differenzen‐Differentialgleichung für den Isotropteil der Geschwindigkeitsverteilungsfunktion der Elektronen wird mittels numerischer Methoden für ein anisothermes Neon‐Plasma unter homogenen stationären Bedingungen in einem großen Wertebereich der auf den Neutralgasdruck bezogenen elektrischen und magnetischen Feldstärke sowie für verschiedene Winkel zwischen elektrischem und magnetischem Feld gelöst. Mit den ermittelten Verteilungsfunktionen erfolgt gleichzeitig die Berechnung der Komponenten der tensoriellen Beweglichkeit und des tensoriellen Diffusionskoeffizienten, der mittleren kinetischen Elektronenenergie, der Stoßfrequenz für die Anregung der Neutralgasatome und der Energieverlustraten der Elektronen. Anhand der Ergebnisse der Berechnung wird der Einfluß der durch das Magnetfeld bedingten Lorentz‐Kraft auf die Verteilungsfunktion und die Transporteigenschaften der Elektronen sowie auf die durch die Elektronen bewirkten Energietransformationsmechanismen vom elektrischen Feld zum Neutralgas ausführlich diskutiert.
Über die Intensität optisch dicker Linien in zylindersymmetrischen inhomogenen Plasmen
Authors: Funk W. , Kloss H.‐G.
Published: July 2007

In der vorliegenden Arbeit wird gezeigt, daß die Intensität optisch dicker Linienstrahlung in anderer Weise von den Plasmaparametern abhängt, als im Falle optisch dünner Linienstrahlung. Durch Anwendung der von BARTELS entwickelten Theorie der Emission aus optisch dicker Schicht kann die Intensitätsabhängigkeit optisch dicker Linien vom Druck der verschiedenen Plasmakomponenten und von der Plasmatemperatur separiert werden und dadurch insbesondere das experimentell beobachtete Anwachsen der Thalliumstrahlung bei Erhöhung des Quecksilberdruckes in einer Quecksilberhochdruckentladung mit Thalliumzusatz geklärt werden.
Rückstreuungsmessungen photoelektrisch ausgelöster Elektronen in Edelgasen im homogenen Feld
Authors: Felsch D. , Pech P.
Published: July 2007

An der Katode ausgelöste Elektronen werden durch Stöße mit Gasmolekülen wieder zu ihr zurückgestreut. Es werden Rückstreuungsmessungen von photoelektrisch ausgelösten Elektronen in den Edelgasen Ne, Ar, Kr und Xe beschrieben. Die Rückstreuung wurde in Abhängigkeit von X/p0 und der Anfangsenergie der ausgelösten Elektronen bestimmt. Die Ergebnisse der Messungen werden mit den Theorien von Hantzsche, Pech und Thomson‐Loeb verglichen. Es wird eine empirisch ermittelte Formel zur Beschreibung der Rückstreuung angegeben.
Über eine spektroskopische Meßmethode des Rekombinationskoeffizienten im Neonnachleuchtplasma. Teil II. Die Temperaturabhängigkeit des Rekombinationskoeffizienten in der Neon‐Mitteldrucksäule
Authors: Golubowsky Ju. B. , Michel P.
Published: July 2007

Durch Lösung der Energiebilanzgleichung für das Elektronengas wurde der zeitliche Abfall der Elektronentemperatur ermittelt. Experimentelle Untersuchungen des zeitlichen Verlaufs der Intensität des Bremskontinuum bestätigten den berechneten Verlauf. Die Auswertung der Abklingkurven der Spektrallinien mit diesem Elektronentemperaturverlauf führt zu einer Temperaturabhängigkeit des Rekombinationskoeffizienten α = α0 · Ue−1/2 im Elektronentemperaturintervall 4000°K ≥ Te ≥ 400°K.
Zur Radialstruktur der diffusionsbestimmten positiven Säule der Sauerstoff‐Entladung bei niederen Gasdrucken
Authors: Sabadil Heinz
Published: July 2007

The radial distribution of the electrons, negative and positive ions in the cylindrical positive column of the direct current discharge in 02 has been calculated. The negative ions are formed by dissociative attachment (02 + e →− + 0), the destruction of negative ions is effected by the reverse process (0− + 0 02 + e). The pressure is assumed to be low enough that the radial variation of 0‐concentration can be neglected. By use of the condition of the quasineutrality and the ambipolarity for the radial current from the balance equations of the electrons and the negative ions two differential equations of second order are derived, which has been solved numerically for different values of the ratio zj/za and β[0]. Numerical results show that the radial distributions of the charge carriers are not‐proportional. If zj ≈︁ za the radial distribution of the electron density is enlarged, compared to a Bessel distribution.

The radial distribution of the negative ions is also enlarged in the centre of the column, but near the wall of the tube a lack in the density exists. The effective diffusion coefficient of the negative ions is negative, i.e., they are moving from the wall of the tube to the centre of the discharge. The enlargement of the radial distributions of the charge carriers, which results in an improvement of the economy of the balance of electrons, increases if zj/za and β/[0] are decreased.
Model Calculations on the Positive Column of a Medium Pressure Neon Gas‐discharge
Authors: Smits R. M. M. , Lammers P. H. M. , Baghuis L. C. J. , Hagedoorn H. L. , Heide J. A. V. D.
Published: July 2007

Model calculations on the positive column of a neon gas‐discharge for gas pressures between 50 and 350 torr and currents between 5 and 100 mA are presented. In these calculations a Druyvesteyn distribution for the electron energy has been used. Volume recombination and radially dependent electron and gas temperatures have been taken into account. Numerical results are compared with available experimental data. In particular, the axial field strength, electron density, electron temperature and ambipolar field strength are considered. In general, the agreement between experimental and numerical data is good.
Zur Mikrowellendiagnostik der Elektronenkonzentration im molekularen Stickstoffplasma der Schwachstromsäule
Authors: Gundermann S. , Winkler R.
Published: July 2007

Es wird über die Berechnung der bei Anwendung der Mikrowellenresonatormethode zur Elektronenkonzentrationsbestimmung im stationären homogenen N2‐Säulenplasma erforderlichen komplexen HF‐Leitfähigkeit berichtet. Neben der aufwendigen exakten Berechnung mittels Lösung der BOLTZMANN‐Gleichung werden zwei weitere Näherungsberechnungen – wie sie für die HF‐Leitfähigkeit in einigen Edelgasplasmen gebräuchlich sind – vorgenommen und die Verwendbarkeit solcher Näherungsberechnungen für das Molekülgasplasma kritisch bewertet. Ferner werden die mit den verschiedenen Berechnungsvarianten erhaltenen Werte für die HF‐Leitfähigkeit zur experimentellen Bestimmung der Elektronenkonzentration nach der Mikrowellenresonatormethode im N2‐Plasma niedrigen Ionisierungsgrades verwendet und die erhaltenen Werte der Elektronenkonzentration den aus einer Strombilanz des Säulenplasmas bestimmten Konzentrationswerten gegenübergestellt.
Comparative Study of Existing Theories for Volume Ion‐Electron Recombination in Plasmas
Authors: Drawin H. W. , Emard F.
Published: July 2007

Different methods have been proposed in the past for calculating the atomic ion‐electron recombination coefficient of plasmas, for example collisional‐radiative models of D'ANGELO (1961) and of BATES et al. (1962); the “bottleneck” models of HINNOV and HIRSCHBERG (1962) and BYRON et al. (1962) modified by CHEN (1969) and WANLESS (1971); the variational theory of MAKIN and KECK (1963), modified by CURRY (1970); the J. J. THOMSON method modified by D'ANGELO (1965). Using the appropriate atomic parameters the recombination coefficients were calculated for a wide range of electron temperatures and electron densities for optically thin and optically thick hydrogen and helium plasmas. The characteristic discrepancies between the different theories are discussed. To be mentioned is the relative good agreement of the “bottleneck” models and the complete collisional‐radiative theory for optically thin and thick hydrogen plasmas at nearly all temperatures, but the agreement is less good for helium plasmas especially in the optically thick case at elevated temperatures. It is the first time that such a comparative study based on a consistent set of atomic parameters has been undertaken.
Investigations of the Arc Burning in the Water Vapour Atmosphere
Authors: Todorović M. , Rekalić M. , Ikonomov N. , Pavlović B. , Vukanović V.
Published: July 2007

The functions of thermal conductivity α(T) and electrical conductivity σ(T) for water vapour, within the temperature intervals 7700–8000 K and 2000–3500 K, were calculated. These calculations were performed by using the UHLENBUSCH'S method and the empirical one. Calculations were based on experimentally determined electric field strength as a function of the arc current and radial temperature distribution in the central zone and in the surrounding of the arc burning in water vapour atmosphere.
The Decomposition of Methane, Ethane, Ethylene and n‐Butane in Electrical Discharges of Moderate Pressures
Authors: Capezzuto P. , Cramarossa F. , D'agostino R. , Molinari E.
Published: July 2007

The decomposition of CH4, C2H6, C2H4, and n‐C4H10 has been investigated in radiofrequency plasmas operated at power levels of 1–8 cal cm−3 sec−1, 10–40 torr and flow rates of the hydrocarbons between 2 and 20 1 (STP) min−1.

It is shown that values of the rate constants are very close for all the hydrocarbons investigated and several orders of magnitude greater than those observed in their pyrolisis at comparable gas temperatures. Energy yields up to 30% can be observed for all hydrocarbons.

It is suggested that the rate determining step for the decomposition process of all hydrocarbons investigated involves the rupture of a C‐H bond in vibrotationally excited molecules.
Untersuchung der Prozesse in der aktiven Zone der Hohlkatodenbogenentladung I. Die Energieverteilungsfunktion der Elektronen, die Anregungs‐ und Ionisationsgeschwindigkeit
Authors: Rešenov S. P. , Lunk A.
Published: July 2007

In der vorliegenden Arbeit werden die Ionisations‐ und Anregungsprozesse im Innern der Katode einer Hohlkatodenbogenentladung untersucht. Ausgangspunkt ist die Berechnung der Elektronenenergieverteilungsfunktion aus der kinetischen Gleichung, die unter Berücksichtigung sowohl der Coulombwechselwirkung der schnellen Elektronen mit den Plasmaelektronen als auch der elastischen und unelastischen Wechselwirkung der Elektronen mit den Gasatomen gelöst wird. Die Kenntnis der Energieverteilungsfunktion gestattet die Berechnung der Anregungs‐ und Ionisationsgeschwindigkeiten in der aktiven Zone der Hohlkatodenbogenentladung.
Erosion Phenomena on Contaminated Cathodes Caused by Electrical Discharges in Ultra High Vacuum
Authors: Jüttner B.
Published: July 2007

Self‐limiting discharges occur on contaminated cathodes in UHV without any contribution of the anode. They propagate over the cathode surface with velocities ≥ 5.104 m/s, preferentially along grain boundaries. From these observations an analogy is suggested between micro‐discharges in high voltage gaps and are spots with weak erosion.
On the Heat Sources of the Arc Cathode Spot
Authors: Hantzsche E.
Published: July 2007

The main heat sources of the are cathode root are ion impact and neutralization heating at the surface and Joule (resistance) heating in the volume of the cathode. The ratio IIji between these two components of cathode power supply is investigated, it depends only on J/a (spot current divided by spot radius). In the case of Cu cathodes both components are equal if J/a = 9.17A/μm, and their contributions to the increase of the spot temperature are equal if J/a = 10.25 A/μm. This holds approximately even if the electron emission cooling is taken into account (by inclusion in the surface power supply). In the real (non‐stationary) arc spot the influence of resistive heating is rather low (between 0.1 and 1 percent of the total power supply in the case of clean surfaces), with the exception of the explosive emission processes, where the Joule heat generation is comparable with or even superior to the surface heating processes by impact or possibly electron emission (Nottingham effect). The time average of the Joule component relative to the impact power input depends on the role of such essentially non‐stationary processes in the arc spot regime. An estimate of this ratio IIj,ie basing on theoretical investigations and experimental experiences results in 0.01 ≲ IIj,ie ≲ 1.
Theoretical Description of the Radial Distributions of the Ions and of the Electrons in the Subnormal Positive Column
Authors: Valentini H.‐B.
Published: July 2007

A relatively simple set of differential equations describing the radial profiles of the number densities and of the radial drift velocities of the ions and the electrons and of the radial electric field intensity in the subnormal positive column is derived. The inertia of the ions is taken into consideration, but the ion temperature is supposed to be zero. Corresponding boundary conditions are used. For discharges in argon under diffusion and under free‐fall conditions numerical solutions are given.
Kinetics of the Electron Component in the Turbulent Electron‐Beam Discharge Plasma in Diatomic Gases and Comparison of some Macroscopic Properties between the Plasmas of the Beam and the Glow Discharge
Authors: Starykh V. V. , Wilhelm J. , Winkler R.
Published: July 2007

The present paper is devoted to the investigation of the kinetics of the electron component in the stationary beam discharge plasma in molecular nitrogen. Using the Boltzmann equation with the inclusion of the elastic and the main inelastic binary collisions and also the Coulomb interaction between the charged particles we have calculated the energy distribution function and some macroscopic quantities of the electrons within a large range of parameters. Using our earlier results for the beam discharge plasma in hydrogen, also the dependence of the macroscopic quantities on the kind of molecular gas is discussed. Finally, the comparison of some macroscopic properties of the beam and the glow discharge plasma was performed under the condition of equal power input per volume unit in both types of plasmas in nitrogen.
Das diffusionsbestimmte Plasma der positiven Säule von Niederduckentladungen in Neon bei mittleren Ionisierungsgraden von 10−8—10−3
Authors: Pfau S. , Winkler R.
Published: July 2007

Ausgehend von den in den letzten Jahren entwickelten Näherungsmethoden zur mikrophysikalischen Beschreibung des axial homogenen Plasmas der diffusionsbestimmten positiven Säule sowohl im Bereich hinreichend schwacher (Schwachstromsäule) als auch starker Ströme (Starkstromsäule) wird in der vorgelegten Arbeit eine quantitative Behandlung des Säulenplasmas in Neon für den gesamten Strombereich von ≈ 1 mA bis ≈ 10 A vorgenommen. Diese Untersuchungen basieren auf der simultanen Lösung der Konzentrationsbilanzen der Elektronen und der in den 18‐und 2p‐Niveaus angeregten Neon‐Atome, der Strombilanz des Säulenplasmas und der Elektronen‐Boltzmann‐Gleichung unter zusätzlicher Berücksichtigung von Stufenprozessen und der Coulomb‐Wechselwirkung zwischen den Elektronen. Dabei wird die radiale Variation insbesondere der Stoßraten für Elektronenstöße über die Berechnung der quasihomogenen Änderung der Geschwindigkeitsverteilung der Elektronen infolge der radial variierenden Intensität der Stufenprozesse und der Coulomb‐Wechselwirkung beschrieben. Die numerisch erhaltenen Ergebnisse über die Stromabhängigkeit der axialen Feldstärke, der Elektronen‐ und Angeregtenkonzentration, der verschiedenen Erzeugungsprozesse von Ladungsträgern und der Geschwindigkeitsverteilung der Elektronen werden diskutiert und teilweise experimentell gewonnenen Resultaten gegenübergestellt.
The Rotation of Ions and Neutrals in a Cylindrical Magnetized Hollow Cathode Argon Arc
Authors: Timmermans C. J. , Lunk A. , Schram D. C.
Published: July 2007

In a magnetized hollow cathode arc rotational velocities of ions and neutrals and their temperatures were measured in axial and radial dependence. In comparison with theory experimental results give a detailed analysis of radial transport phenomena.
Cathode Erosion in Vacuum Arcs and Unipolar Arcs
Authors: Nürnberg A. W. , Bauder U. H. , Mooser C. , Behrisch R.
Published: July 2007

The cathode spots from vacuum arcs on 316 stainless steel are compared with the tracks found on the same material after exposure to the plasma of the tokamak TFR 600. Further the erosion yields of vacuum arc cathodes of 316 stainless steel and titanium are determined from experiments and the measured values are compared with theoretical estimates. The velocity of the arc is investigated as a function of the applied magnetic cross‐field. The scatter of both, the velocity data and the erosion yields is substantial. Improved experiments are planned.
Reaktionskinetische Vorgänge an der Grenzfläche zwischen nichtisothermem Plasma und Feststoff
Authors: Friedrich J.
Published: July 2007

An der Grenzfläche nichtisothermes reaktives Molekülgasplasma – Feststoff bilden sich ätzgasspezifische funktionelle Gruppen durch Anlagerung von Plasmaspezies als Vorstufe für Abbauvorgänge (chemische Abbaureaktionen und Sputterprozesse) oder für die Bildung von (Polymer‐) Schichten. Die z. B. bei verschiedenen Polymeren beobachteten langsam fortschreitenden Veränderungen der Struktur in oberflächennahen Schichten, bis etwa max. 100 μm, werden durch die energiereiche Plasma‐Vakuum‐UV‐Strahlung hervorgerufen. Die Bildung funktioneller Gruppen an der Feststoffoberfläche vollzieht sich sehr rasch. Daran schließt sich eine Periode der langsamen Penetration von Plasmaspezies in die obersten Feststoffschichten an (nm‐Bereich). Der Abbau der Feststoffe verläuft nur dann nicht zeitlich linear, wenn der Festkörper eine schichtartige Struktur besitzt.
On the Quantitative Treatment of the Growth Rate of Thin Polymer Films Produced in Glow Discharges
Authors: Deutsch H. , Schmidt M.
Published: July 2007

An extensive system of equations is derived to determine the growth rate of thin polymer films induced by an anisothermic plasma taking into account activation reactions as well as transport processes in the plasma volume and surface reactions. A survey of the literature on the quantitative treatment of plasma polymerization is given.
Investigations on Afterglows of Neon Gas Discharges
Authors: Steenhuijsen L. W. G.
Published: July 2007

We report on the experimental and numerical investigations on afterglows of neon gas discharges, which are performed at the Eindhoven University of Technology.

The studied gas pressure range extends from 1 to 100 torr, the discharge current from 1 to 100 mA. The densities of the 1s‐levels are measured with the help of the selective excitation spectroscopy (fluorescence technique). In this way a great number of decay curves of the 1s‐densities have been measured in the afterglow of neon gas discharges. From these curves the diffusion coefficient of the metastable 1s‐atoms, the coefficients of atomic collisional transfer between the 1s5‐ and 1s4‐level, as well as the three body collision coefficient between metastable 1s5‐atoms and neon ground state atoms have been determined.

Besides these experiments a numerical model of the neon afterglows has been developed. With this model the afterglow phenomena can be simulated and the influence of the particular processes on the whole afterglow can be studied conveniently. Comparison is made between the experimentally and numerically obtained decay curves.

For the application of the numerical model a number of starting conditions, such as radial density profiles, gas temperature, (relative) densities of the 1s‐levels, have been measured. Results of these measurements are presented.

Also with the help of the selective excitation spectroscopy the coefficients of atomic collisional transfer between the 2p‐levels have been measured in the afterglow. From these results, together with the measured (relative) intensities of the neon spectral lines in the afterglow the partial recombination coefficients for the 2p‐levels were calculated.
Physikalisch‐chemische Vorgänge beim Plasmaätzen mit fluorhaltigen Ätzgasen
Authors: Poll H. U. , Schlemm H.
Published: July 2007

Examples are given for three main processes determining the reactions in plasma etching:

The interaction between plasma particles and the surfaces of solids;

The conversion of the gas composition in the plasma;

The transport phenomena of reaction products in the reactor and the vacuum system.

In the glow discharge the behaviour of saturated and unsaturated perfluorocarbon gases is very similar. Both classes of compounds are converted in a few seconds in the homologous series of perfluoroalcanes up to products of high molecular weight. The main products are CF4, C2F6, C3F8. Unsaturated compounds lead to the deposition of thin polymer films on the walls and the electrodes, whereas saturated ones are only capable of producing films on the surface of the reaction vessel. The deposition results from the recombination of free radicals arising from the plasma interactions in the gas and at the surfaces. Vice versa sputtering of polymer fragments acts on the gas composition in the plasma. Conversion processes are controled by current density and gas pressure. The cathode fall region of the discharge is found to be the zone of the highest reaction activity.
Calculation of Recombination and Ionization Coefficients in Argon
Authors: Gleizes A.
Published: July 2007

Various methods for calculating electron‐ion recombination and ionization coefficients for argon (α and S) have been developed in the past. For given values of electron temperature and electron density, a large dispersion exists between the different results due to a great number of parameters. We have developed the method based on the collisional‐radiative model to calculate α and S for limited conditions (atmospheric pressure; strong resonance radiation absorption) in order to obtain realistic values applicable in real cases such as arc plasmas. Influences of resonance radiation absorption and atom‐atom collisions have been studied. The collisional‐radiative recombination coefficient has been compared with results obtained by other calculation methods: the best agreement occurs with the “bottleneck” model for high values of electron density and temperature. Finally the comparison with available experimental results shows a good agreement between our computed values and experimental values when experimental and theoretical conditions are analogous.
The Thermo‐Field Emission of Electrons in Arc Discharges
Authors: Hantzsche E.
Published: July 2007

Starting from the conventional theory of thermo‐field emission of electrons from metal surfaces, the range of validity and the errors of several approximate emission formulae are examined that are additive or harmonic combinations of the limiting thermionic (Richardson) and field emission (Fowler—Nordheim) equations. An optimization of such kinds of equations results in the simple dependence (for example)

(iTF electron current density, T temperature, F field strength, k, A, B etc. are constants), or

(dependent on only one variable Y = T + β′F β′ = const.).

If the emission equations are applied to arc cathodes, both T and F must be expressed as functions of the ion current (Ii) and the ion current density (ji); a simple interpolating formula of the electron current density je adapted to numerical results in the case of Cu cathodes becomes

(Ā, B̄, C̄: constants).
On the Conductance Theory of Plasmas
Authors: Kraeft W. D. , Blümlein J. , Meyer T.
Published: July 2007

In the framework of the linear response theory a quantumstatistical expression for the conductivity of nonideal plasmas is derived. In a simple approximation the influence of electron‐ion scattering and that of masses of equal magnitude on the conductivity is discussed; the latter is expressed in terms of transport collision frequencies.
Analysis of the Kinetic Properties and the Energy Budget of the Electrons in the ArHg Glow Discharge Plasma at Varying Partial Pressures and Discharge Currents
Authors: Winkler R. B. , Wilhelm J. , Winkler R.
Published: July 2007

By simultaneously solving the Boltzmann equation and the current balance for the electrons the energy distribution function, the electron concentration and resulting macroscopic electron quantities were calculated for the ArHg mixture plasma under conditions typical of fluorescent lamps. Besides the usual external parameters of such diffusion determined discharge plasmas measured values of the electric field strength were employed. The investigations were performed for independent variation of the partial pressures of Ar and Hg as well as of the discharge current in wide ranges of practical interest. The results obtained are discussed and compared with various energy distributions employed up to now and measured values of the electron concentration and temperature as well as with experimental results on the energy budget of this mixture plasma available in the literature.
Half‐Integer Harmonics Generation in Laser‐Produced Plasma
Authors: Bychenkov V. Tu. , Zozulja A. A. , Silin V. P. , Tikhonchuk V. T.
Published: July 2007

Half integer (3/2ω0, 1/2ω0) harmonics generation under oblique incidence of the pump‐wave on the spatially inhomogeneous plasma is theoretically investigated. Harmonics generation is connected with the two‐plasmon convective instability excitation near the quarter‐critical density. Harmonics spectra and intensities depend essentially on the pump wave polarization. In particular, significant harmonics spectra broadening arises under the p‐polarized pump wave.
On the Solution of the Electron Boltzmann Equation in Higher Order Legendre Polynomial Expansion
Authors: Winkler R. , Wilhelm J. , Hess A.
Published: July 2007

The paper deals with the mathematical structure of the general solution and the selection of the physical relevant solution of the hierarchy resulting from the electron Boltzmann equation by the Legendre polynomial expansion for a weakly ionized plasma with elastic and exciting collisions and under the action of an electric field. At first the properties of the general solution for the two and four term approximation of the distribution function are analyzed and then the study is extended to arbitrarily even order of the hierarchy using the theory of weakly and strongly singular differential equation systems for the investigation of the solution behaviour of the truncated hierarchy at small and at large energies, respectively. In this way, especially the free parameters of the non‐singular part of each general solution, which is obtained for small and large energies and is of interest for the construction of the desired solution, could be found, and the procedure for their final determination is explained. A first illustrative example is given of the application of these studies for the determination of the velocity distribution function of the electrons in four term approximation for a model plasma.
Initiation and Sustainment of Unipolar Arc Discharges by a Microsecond Pulse Plasma
Authors: Ivanov V. A. , Jüttner B. , Pursch H. , Siemroth P.
Published: July 2007

Unipolar arcs have been produced by contacting metal surfaces with microsecond pulse plasmas. Plasma temperature Te, density ne and potential (with respect to ground) were controlled in the limits 7–12 eV, 1018–1019 m−3, 20–40 V, respectively, and the influence of these parameters on arc current amplitude (50–500 A) and ignition probability has been investigated. It was found that the ignition is the most limiting process requiring surface contaminations as well as the transport of net currents to the surface. The amplitude of the current was proportional to neTe1/2.
The Ratio of Lateral Diffusion Coefficient to Mobility for Electrons in CO2 Laser Mixtures
Authors: Braglia G. L. , Romanò L. , Roznerski W.
Published: July 2007

A Townsend‐Huxley apparatus has been used to measure the lateral diffusion coefficient to mobility ratio D/μ in two gas mixtures of special interest when modeling h.p. CO2 lasers. The results are compared with the corresponding theoretical values obtained with the conventional two‐term theory in order to assess the limits of the theoretical predictions and have indications on the accuracy of the available cross sections.
Stability of a Rotating Compressible Stratified Plasma in the Presence of Hall Currents and Magnetic Resistivity
Authors: Adeniyan A. , Bhatian P. K.
Published: July 2007

The dynamic instability in a horizontal layer of a rotaing compressible plasma of variable density has been investigated to examine the influence of the simultaneous presence of the effects of Hall currents and finite magnetic resistivity. The linearized stability analysis has been carried out through the normal mode technique. By making use of the existence of a variational principle which is shown to characterize the problem, proper solutions have been obtained for a semiinfinite plasma in which there is an exponential density gradient along the vertical. The dispersion relation obtained has been solved numerically and it is found that both the resistivity and the Hall currents have a destabilizing influence as the growth rate of the unstable disturbances increases with increasing values of the parameters characterizing these effects. On the other hand, the Coriolis forces are found to have a stabilizing influence for in this case the growth rate decreases with increasing rotation.
Nonlinear Resonant Interaction of Two Longitudinal Waves and a Transverse Wave in a Hot Magnetized Plasma
Authors: Das K. P.
Published: July 2007

By Whitham's method of averaged Lagrangian and using Low's form of Lagrangian, coupled mode equations and coupling coefficients are derived for resonant nonlinear interaction of two longitudinal and one transverse wave in a magnetized plasma, in which the later wave propagates along the external uniform magnetic field. The limiting form of these coupling coefficients are obtained when the external magnetic field vanishes.
Abscheidung von Glimmpolymerschichten in einem weiten Metallrezipienten und Untersuchungen zur Struktur
Authors: Möller W. , Schmidt M. , Seefeldt R. , Wilberg R.
Published: July 2007

Investigations are reported of growth rate, chemical structure (IR‐spectroscopy, mass‐spectrometry), thermal stability, surface structure (scanning electron microscopy) of thin polymeric films grown in a gas (Ar‐hexamethyldisiloxane‐mixture) discharge with a heated cathode, which is situated in the centre of a cylindrical metallic vessel (l = 50 cm, 2r = 30 cm).

The discharge conditions are the following: I = 0,25 – 4 A, U = 30 – 100 V, p = 6 – 40 Pa, argon flow rate = 3,8 · 10−5 mol/min, Ar/HMDS = 1 : 0,7 – 1 : 2,4.

The growth rate changes from 2 to 18 nm/min, depending on the discharge conditions. The reproducibility of the growth rate shows deviations smaller than 10%. The films consist of a highly cross linked polymeric material and are stable up to 260°C, the solubility in n‐hexane being smaller than 2%. The surface of the thin film (d ∼ 102 nm) is smooth. Corrosion resistance to soda lye (0,2% NaOH) has been proved.
Three‐Wave Coupling Coefficients for Non‐Uniform MHD Plasmas
Authors: Lindgren T.
Published: July 2007

Resonant three‐wave interaction in a spatially non‐uniform MHD plasma is considered, and the coupling coefficients are derived.
Investigation About Stepwise Excitation Cross Sections in Rare Gases
Authors: Behnke J. F. , Deutsch H. , Scheibner H.
Published: July 2007

Stepwise excitation cross sections of the rare gases helium, neon and argon were obtained by an indirect method resting on the combination of experimentally determined excited species number densities of the rare gas atoms in the positive column of a low pressure glow discharge with the results of the theory of the positive column and electron kinetics. Furthermore a semiempirical expression of the excitation functions basing on the analysis of the Born‐approximation and modifications as well as a formula of Vainstein is offered.
Formation of ac Discharges Between Glass Insulated Electrodes in Ne+1% N2 Mixtures. III. Discharge Development and Space Charge
Authors: Lange H. , Stern W.
Published: July 2007

The investigation of the optical space‐time‐structure of the discharge development was made for various values of pD (1,3 kPacm, 33,4 kPacm) by means of the variation of the electrode distance for two gas pressures. The broadening of the bistable region with growing electrode distance can be explained by the effect of the positive space charge as a virtual anode. Thus the space charge memory is dependent on the value of pD. If the space charge breakdown takes place, a light front moves from the anode to the cathode, its velocity, varying from 3 · 104 cm/s to 8 · 105 cm/s. In the volume an optical structure develops which is analogous to that of a medium pressure glow discharge. If the time between successive discharge pulses is too short, then the decay of the positive space charge is incomplete and there is no Townsend phase. The process depends, via the ion drift velocity, on the electrode distance.
Lichtenberg Figures on Dielectrics in Gases and in Vacuum
Authors: Anders A.
Published: July 2007

A review is given first on Lichtenberg figures on dielectrics in gases. The problem of Lichtenberg figures at low gas pressures (p<1 Pa) is raised. Experiments are reported about the latter. The results are discussed by the help of models of vacuum flashover on dielectrics.
Fundamentals of a Technique for Determining Electron Distribution Functions by Multi‐Term Even‐Order Expansion in Legendre Polynomials. 2. Comprehensive Investigation of a Model Plasma
Authors: Winkler R. , Braglia G. L. , Hess A. , Wilhelm J.
Published: July 2007

Applying the new technique for finding the converged solution of the Boltzmann equation in a weakly ionized plasma, which was developed in the first part of this paper, a comprehensive study of the electron velocity distribution function for a model plasma with elastic and exciting collisions is performed by solving the Boltzmann equation with increasing order of approximation. The purpose of this investigation is that of calculating the isotropic distribution f0, the first contribution f1 to the anisotropy of the velocity distribution, the important macroscopic quantities and, more generally, that of studying the total anisotropy as well as the changes of all these quantities when the approximation degree is enlarged beyond the 2 terms of the conventional Lorentz approximation. By varying some parameters of the model plasma, that is the electric field strength, the magnitude of the excitation cross section and the excitation threshold, the main features of plasmas in inert as well as molecular gases are modelled and the impact of these parameters on the mentioned quantities is analysed. Some of the converged results are compared with results of corresponding Monte Carlo simulations.

The approximation degree required to find the converged values of isotropic distribution, main macroscopic quantities and electron distribution in the velocity space (and thus its real anisotropy) is estimated by solving the Boltzmann equation over wide parameter ranges.