bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Polishing Effect of Nanosecond Discharges in Vacuum
Authors: Jüttner B. 
Published: July 2007

AbstractWhen 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

AbstractAn 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

AbstractThe 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

AbstractUnipolarbögen 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

AbstractThe 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

AbstractThe 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

AbstractElektrophorese 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.
Critical Current of the Ionization Waves and Anomaly of the Positive Column in an Axial Magnetic Field
Authors: Sato M. 
Published: July 2007

AbstractInfluences 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

AbstractOn 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

AbstractThe 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

AbstractCraters 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

AbstractIn 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

AbstractIn 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

AbstractThe 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

AbstractMeasurements 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

AbstractAmong 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

AbstractIn 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

AbstractFür 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

AbstractThe 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

AbstractA 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

AbstractTwo 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

AbstractEin 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

AbstractThis 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

AbstractThe 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

AbstractTheoretical 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.
Experiments on Arc Perturbation in Turbulent Gas Flow
Authors: Michel G. , Rothhardt L. 
Published: July 2007

AbstractElectric arcs burning in a strong, turbulent, axial nitrogen gas flow are studied. Time‐resolving (framing) picture series of the arc and its deformations are taken through the quartz tube channel wall. Individual perturbations like kinks exist under strong, turbulent flow conditions. They move with constant acceleration in the direction of the cold gas flow. The temperature of the arc core is disturbed at the position of these disturbances, too. This shows up most distinctly, if the decay of the arc after short‐circuiting is studied, as has been done additionally.