bluuebunny/crossref_metadata_2025_split huggingface dataset:
Van Kampen and Case Formalism Applied to Linear and Weakly Nonlinear Initial Value Problems in Unmagnetized Plasma
Authors: Lambert A. J. D. , Best R. W. B. , Sluijter F. W. 
Published: July 2007

AbstractA unified account is given of the normal mode theory of homogeneous unmagnetized plasma. Electron (Langmuir), ion sound and electromagnetic waves are treated in stable and (Penrose) unstable plasma with the Van Kampen‐Case formalism, using generalized functions. Simplified formulae are derived for second‐order Langmuir waves, taking full account of free‐streaming effects.
Investigations of Impurity Atom Deposition in the Limiter Shadow of the T‐10 Tokamak by Means of Auger Electron Spectroscopy
Authors: Chicherov V. M. , Hildebrand D. , Laux M. , Lingertat J. , Lukianov S. U. , Pech P. , Reiner H.‐D. , Stepanchikov V. A. , Wolff H. 
Published: July 2007

AbstractThe impurity flux in the limiter shadow region of the T‐10 tokamak has been studied by exposing a solid probe to the plasma and subsequent investigation of deposits by surface analysis techniques.The main constitutents of the inner construction materials of T‐10 could be detected by AES and SIMS. The deposited amount of impurities has been shown to rise with a decrease of the distance between probe and plasma. Long term observations of the metal impurity composition in the limiter shadow region by means of the deposition probe have shown a gradual decrease of the relative Ni concentration, which is explained as a successive deposition of stainless steel limiter material on the Inconel liner. The observed spatial asymmetry of the impurity flux and the deposition profiles for different elements on the probe are discussed.
Thomson Scattering Applied to a Noisy Radiative Plasma
Authors: van Der Sijde B. , Adema S. , De Haas J. , Denissen C. J. M. , van De Sande M. J. F. 
Published: July 2007

AbstractThomson scattering with a 1.5 ms long pulse mode 20 J ruby laser has been applied to a radiative argon plasma with electron densities ne from 2.5 1019 m−3 to 1.5 1020 m−3 and an electron temperature Te of about 3 eV. Photon counting techniques have been used. The accuracy of ne and Te to be reached is about 5% after 10 shots. The signal to noise ratio S/N has been optimized by the use of optical filters and a special purpose grating. The effects of these elements on S/N have been calculated. The entrance angle, transmission and quantum efficiency have also been optimized. A comparison between 5 possible laser systems, including a normal mode and a Q‐switched mode ruby laser, has been carried out.
Untersuchungen zu den Existenzbereichen und Typen von ac‐Entladungen. II. Das Verhalten der Entladungstypen in Ne/Ar‐Gemischen und der Vergleich mit Ne/N2‐Gemischen
Authors: Müller S. , Zahn R. J. 
Published: July 2007

AbstractThe investigations on the transition between the discharge modes in NeN2 mixtures are described in [1]. In the present paper we investigate NeAr mixtures with a view to comparing the behaviour of these different mixtures. The measurements confirm the transition mechanism between the bistable pulse mode and the non‐bistable continous mode in Ne‐Penning mixtures. The life time of metastable atoms is important for the existence of the continuous mode. If the life time is changed by varying the cross sections for the Penning ionization Qp (e.g. in other mixtures), the transition frequency of both these discharge modes shows a corresponding shift, which, for both mixtures, is in good agreement with literature values of Qp. The second part presents a study of the quasiglow mode. The transition between the pulse mode and the quasiglow mode correlates to the ion transit time. The three discharge modes are represented in the existence diagram.
Spektroskopische Untersuchung unelastischer Stöße zwischen Ionen oder metastabilen Atomen der Edelgase und Alkalimetallatomen bei thermischen Stoßenergien
Authors: Vogel D. , Tolmachev Yu. A. 
Published: July 2007

AbstractThe present work deals with the spectroscopic investigation of Penning ionization and nonresonant charge exchange due to thermal‐energy collisions of metastable atoms or ions of the inert gases He, Ne with atoms of alkali metals K, Rb, Cs in a low temperature plasma of the corresponding binary mixtures. The rate constants of these reactions and partial rate constants of exciting several alkali metal ion levels were determined by the kinetics of the decay of ionized and excited particles in the afterglow of a pulsed discharge. Measured Penning and charge exchange constants are in order of 1010‐9 cm3 sec−1. Partial Penning constants in the HeCs system exhibit a small dependence of the energy defect of reaction, whereby an important part of collisions results in excited Cs+‐states. On the contrary, energy transfer by charge exchange in HeRb, Cs systems distinguishes by a significant energy defect dependence. Charge exchange from He+ to Rb0 leads above all to He(23S1)‐atoms and normal Rb+‐ions. It follows from the metal ion spectrums, that Penning ionization and charge exchange of the investigated systems under utilized conditions represent as processes of selective excitation of alkali metal ions in afterglow and stationary discharge.
Magnetoplasma Lamination due to Microwave Gyroresonant Heating
Authors: Shvartsburg A. B. 
Published: July 2007

AbstractThe hysteresis transitions between two temperature states of a collisional magnetoplasa due to Joule heating near by the electron gyroresonance are analysed. The propagation of intense extra‐ordinary gyroresonant microwave across the magnetic field in a plasma is responsible for such jump‐like thermic effects, the wave amplitudes being less than the “characteristic plasma field”. The transversal heat conductivity may lead to formation of spatially periodical temperature profiles in the hysteresis region of wave's intensity; the spatial periods of such profiles are much less than the Joule dissipation length of heating wave. The thermodiffusion, stimulated by temperature lamination, may form the spatial oscillations of magneto‐plasma density across the magnetic field.
Formation of ac Discharges Between Glass Insulated Electrodes in Ne + 1% N2 Mixtures. I. Experiments and Analysis
Authors: Stern W. , Lange H. 
Published: July 2007

AbstractAc plasma displays make use of medium pressure ac discharges in Penning mixtures between insulated electrodes. Discharges in Ne + 1% N2 with glazed electrodes are a suitable experimental model showing the characteristic pulse and continous discharge modes. The axial optical space time structure of sinus wave sustained model discharges are measured with a scanning device, obtaining characteristic phases of discharge formation. Application of luminous flux method for stationary and dynamic Townsend discharges yields the first Townsend ionization coefficient α, and the comparison of the optical structure of ac discharges with that of dc discharges allows to explain the axial structure and to estimate the space charge effects.
Stability of a Self‐Gravitating Partially Ionized Plasma
Authors: Sankhla V. D. , Bansal J. L. 
Published: July 2007

AbstractThe dynamic stability of a stratified layer of a partially ionized, self‐gravitating plasma is studied to investigate the effects of finite electrical conductivity. The whole system is immersed in a uniform vertical magnetic field. It is first shown that the solution is characterized by a variational principle. An explicit solution has been then obtained for a semi‐infinite composite plasma in which the density has a one‐dimensional gradient along the vertical.Numerical calculations show that the influence of neutral gas friction and self‐gravitation is stabilizing whereas character of finite electric conductivity is destabilizing.
Nonlinear Theory of the Instability of a Modulated Electron Beam of Low Density in a Plasma IV. Excitation of Nonresonant Waves
Authors: Kruscha K. J. G. , Kondratenko A. N. 
Published: July 2007

AbstractA system of nonlinear equations derived in a previous paper which describes the evolution of nonresonant waves in beam‐plasma systems is solved numerically. It is given a physical interpretation of essential features of the nonresonant beam‐plasma instability. The significant influence of higher harmonics on the evolution of an electron beam in the plasma which is modulated on a nonresonant unstable frequency, is investigated. The interaction of unstable nonresonant and resonant waves in beam‐plasma systems is examined. It is shown that the evolution of resonant waves can be essentially influenced by an initial modulation of the beam on an unstable non‐resonant frequency. The role of an initial velocity modulation of the beam for the influence of the wave spectrum is demonstrated.
On the Relevance of Plasma Parameters in Nonideal Plasmas
Authors: Hess H. 
Published: July 2007

AbstractThe use of different plasma models for composition calculations of nonideal plasmas can result in very different electron concentrations for the same experimental situation characterized e.g. by the measured temperature and pressure. This gives rise to misunderstandings at comparison of theoretical and experimental results. For extreme conditions i.e. in the region of the supposed plasma phase transition results of solid state physics give us the possibility to rule out some plasma models.
Collisional‐Radiative Recombination in Argon Plasmas
Authors: Vľek J. , Ferdinand J. 
Published: July 2007

AbstractOn the basis of the realistic argon atom model consisting of 65 discrete effective levels numerical results for the collisional‐radiative volume recombination, ionization and decay coefficients are obtained. The computations are carried out without any approximations of integral functions. The presented comparison of theoretical and experimental results for the decay coefficient shows that the values calculated by us are in much better agreement with experimental values than those obtained by Desai and Corcoran on the assumption that the argon atom is hydrogen‐like.
Lokale Diagnostik einer Argon‐Niederdruckentladung mit Hilfe der resonanten Laserstreuung
Authors: Bergmann J. , Schubert M. 
Published: July 2007

AbstractWe report on the experimental investigations on a laser‐like low pressure argon gas discharge. The discharge parameters varied in the range from 0,05 to 1 Torr for the gas pressure and from 10 to 30 A for the discharge current.Local electron densities and temperatures have been measured with an adjustable spherical probe.Spatially resolved measurements of the temperatures and drift velocities of the Ar+‐ions in the radial and axial direction of the positive column have been carried out by the resonant laser light scattering (fluorescence technique).The radial density profiles of the excited Ar+‐ions have been determined in two different ways and have been compared with the calculations based on a simple collisional radiative model.
Amplification of Ion‐Acoustic Solitary Waves in a Vlasov‐Plasma. I. A Higher Order Nonlinear Evolution Equation of KdV‐Type
Authors: Bruhn B. , Leven R. 
Published: July 2007

AbstractWith the help of an iterative method we derive a higher nonlinear evolution equation of the KdV‐type starting from the Vlasov‐Poisson system. This equation describes the amplification of ion‐acoustic solitary waves. A perturbative‐theoretical approach is given for small deviations from the 1‐soliton solution. The amplification shows an exponentiel time behaviour in this limit.
On the Plasma Beam Instability of the Space Limited Electron Beam in a Magnetic Field
Authors: Ivanov A. A. , Popkov N. G. , Wilhelm J. , Winkler R. 
Published: July 2007

AbstractThe present paper considers the plasma‐beam instability of a space limited electron beam in a strong magnetic field (ωH ≫ ωo). The form of the beam was taken to be both cylindrical and plane. The threshold of the non‐linear regime turned out to be weakly dependent on the beam form and independent of the magnetic field intensity. It is defined by the current and the directed velocity of the beam particles.
The Effect of Finite Larmor Radius on Gravitational Instability of a Finitely Conducting Magnetised Hall Medium in Presence of Suspended Particles
Authors: Chhajlani R. K. , Purohit P. 
Published: July 2007

AbstractThe problem of stability of a self‐gravitating, infinite homogeneous gas in the presence of suspended particles is investigated. The medium is assumed conducting and effect of external magnetic field, Hall current and finite Larmor radius corrections are also considered. The equations of the problem are linearized and from linearized equations a general dispersion relation for a dusty gas‐particle medium is obtained. The dispersion relation is reduced for two special cases of wave propagations: Parallel and perpendicular to the direction of uniform magnetic field. The effect of suspended particles on the medium is investigated in both the cases. It is found that in the presence of finite Larmor radius corrections and suspended particles the condition of instability is determined by Jeans's criterion for a self gravitating finitely conducting magnetised Hall medium.
On the Symmetrical Modes in a Cylindrical Nonisothermal Plasma Waveguide in a Finite External Magnetic Field
Authors: Nikolov N. A. , Yanovsky A. B. 
Published: July 2007

AbstractA MHD, symmetrical, nonpotential waves in nonuniform, cylindrical nonisothermal plasma waveguide placed in a finite external magnetic field H0 directed along the axis of the waveguide are considered. The thermal velocity of the electrons νTe = (kTe/me)1/2 (k — Boltzman's constant, Te — temperature, me — mass of the electron) is not neglected. As a consequence we obtain one more solution in the plasma region and respectively an equation of third power on χ2 — the transverse wave number. As far as we know only equations of second power on χ2 describing non‐potential waves are investigated. The dispersion equations are written solving the boundary‐value problem. Our results coincide with well known ones when the electron thermal velocity tends to zero.
Electron Kinetics of Weakly Ionized HF Plasmas I. Direct Treatment and Fourier Expansion
Authors: Winkler R. , Deutsch H. , Wilhelm J. , Wilke Ch. 
Published: July 2007

AbstractIn this paper an analysis of the kinetic quantities of the electrons in the steady‐state HF neon plasma is performed by a time consuming direct solution of the time dependent electron Boltzmann equation up to the establishment of the periodic state. In particular, the reduction of the modulation degree and the phase shift with respect to the HF field of the isotropic distribution function and of some macroscopic electron quantities are systematically determined with increasing field frequency. Furthermore, using the Fourier expansion technique, an equation system for the Fourier coefficients of the isotropic distribution function was derived from the time dependent Boltzmann equation which immediately gives a description of the electron kinetics in the steadystate HF plasma. On the basis of this system the coupling of the harmonics of the isotropic distribution with its dc part was studied for different HF fields. In addition, appropriate conditions could be found which determine a field frequency limit above which the coupling impact of the harmonics on the determination of the dc part of the isotropic distribution may be neglected, making a simplified treatment of the electron kinetics possible. The exact determination of its validity limits and the systematic investigations on the basis of this simplified kinetics will be reported in a second paper.
Collisional Radiative Models in Plasmas
Authors: Van Sijde B. Der , van der Mullen J. J. A. M. , Schram D. C. 
Published: July 2007

AbstractA review on collisional‐radiative models in plasmas is given. Work of Fujimoto, Biberman et al, Drawin and Seaton has been an important guide to compose this review. Ionizing, recombining and equilibrium plasmas are dealt with. Attention has been paid to the classification of CR models in phases, such as Corona phase, excitation saturation phase (ESP), Capture radiative cascade (CRC) phase and partical local thermal equilibrium (PLTE). A numerical model applied to the argon neutral system and an analytical model applied to the ESP and PLTE for ionizing plasmas are treated in more detail.
On the Quantitative Determination of Cross Sections of Ionization of Molecules by Electronic Collisions
Authors: Deutsch H. , Schmidt M. 
Published: July 2007

AbstractIt is tested the applicability of formulae for atomic ionization to molecules. The best fit between theoretical and experimental values is given by the formula of Gryzinski. The calculations require the knowledge of the orbital structure.If no detailed information on electronic molecular structure is available, then approximation is attained using the Lotz formula with three fitting parameters.Results are given especially for organic molecules and Cl and F contaning etching gases.
Three Coupled Nonlinear Schrödinger Equations for Two Transverse and One Langmuir Waves and the Stability of Their Solitary Wave Solutions
Authors: Bhakta J. C. , Majumder D. 
Published: July 2007

AbstractThree Coupled nonlinear Schrödinger equations for two transverse and one longitudinal waves has been derived. These equations have been derived using two space time scale techniques. It is shown that even without the effect of relativistic mass variation and ion contribution, all three waves may propagate in the form of localized solitary envelope with a common velocity for small values of the transverse wave numbers and the longitudinal wave number far exceeding kD√me/mi. Stability analysis of the localized solitary wave form reveals that these wave forms are stable.
On the Kinetics of the Active Zone of the Stationary SF6 Beam Discharge Plasma
Authors: Winkler R. , Wilhelm J. , Ivanov A. A. , Popkov N. G. 
Published: July 2007

AbstractThe paper deals with the impact of intensive electron attachment on the kinetics of the electrons in the active zone of the stationary band‐like beam discharge plasma in SF6 which is an alternative useful plasma medium for “dry etching”. The energy distribution of the electrons in this plasma was obtained by numerically solving the Boltzmann equation which includes apart from elastic collisions, different exciting collision processes, attachment in electron collisions, direct ionization, the ambipolar loss of electrons, Coulomb interaction between electrons and of electrons with ions and the power input to the electrons by the turbulent electric field. In particular, due to the needed fulfilment of the consistent electron particle balance, for an extended region of the turbulence energy density in this plasma a large impact on the electron kinetics of the intensive electron attachment, which is the prevailing electron loss process, was found enforcing independent of the turbulence energy density always a large power input to the electrons, smooth and only slowly decreasing energy distributions even in the energy region of direct ionization.
The Model of Macroscopic Kinetics in Non‐Equilibrium Plasma Chemical Reactions I. General Considerations and Basic Relations
Authors: Rutscher A. , Wagner H. E. 
Published: July 2007

AbstractThe reaction of a chemical active non‐equilibrium plasma system is studied within simple kinetic models in principle.Of special interest are steady states of the system with the meaning of a reversible chemical equilibrium.Starting from a schematized description of the non‐isothermal plasma chemical reactor the basic relations of the so‐called macroscopic kinetics are developed and in the case of a comprehensive example (synthesis and decomposition of ozone) compared with the corresponding microscopic kinetics.
Collision Frequencies for Electrical and Heat Conductivity in Dense Cold Plasmas
Authors: Suchy K. 
Published: July 2007

AbstractFormulas for electrical and heat conductivity are derived from the Boltzmann equation with Grad's method of orthogonalized moments, retaining the coupling between diffusion and heat fluxes. The results are expressed by transport collision frequencies. These are calculated for Coulomb interaction potentials screened with the Debye‐Hückel length. Quantum corrections to the classical results are included.
Inversion of the Abel Integral Equation by Use of Simple Interpolation Formulas
Authors: Sato M. 
Published: July 2007

AbstractThe Abel integral equation in plasma spectroscopy is numerically solved by applying the Bessel four‐point interpolation formula of degree two. The method is mathematically tractable, simplifying the Bockasten method. Tests through numerical simulations show that the method is as accurate as more elaborate methods, such as Bockasten, Minerbo‐Levy, Piessens, etc.
Long Time Behaviour of the Modulational Instability of Zakharov Equations
Authors: Majumdar D. , Bhakta J. C. 
Published: July 2007

AbstractThe long time behaviour of the modulational instability of a monochromatic Langmuir wave solution E0 exp i (k0x − ω0t) of the Zakharov equations has been investigated. It is shown that near the threshold of linear instability the evolution of the modulational perturbation is governed by the nonlinear Schrödinger equation and thus the possibility of the development of the modulation into a train of soliton is established. In case of a purely growing modulational perturbation the long time behaviour of the perturbation is suggestive of a Fermi‐Pasta‐Ulam recurrence tendency.
Experimental Study of Ionization Waves in the contracted Discharge in Neon
Authors: Golubovskij Ju. B. , Nekuchajev V. O. 
Published: July 2007

AbstractIt is proved experimentally that there exist constriction ionization waves propogating in the form of current pinch neckings. Dynamics of abrupt contraction and strate arising is investigated by current modulation near the critical value. Dispersion laws are determined depending on discharge conditions.
The Gravitational Instability of a Finitely Conducting Rotating Plasma Through a Porous Medium
Authors: Chhajlani R. K. , Sanghvi R. K. 
Published: July 2007

AbstractThe magneto‐gravitational instability of an infinite homogeneous, finitely conducting, viscous rotating plasma through porous medium is investigated in view of its relevance to certain stellar atmospheres. The dispersion relation has been obtained from the relevant linearized perturbation equations of the problem and it has been discussed in the case of rotation parallel and perpendicular to the direction of magnetic field separately. The longitudinal and transverse modes of wave propagation are discussed in each case of rotation. It is found that the combined effect of viscosity, finite conductivity, rotation and the medium porosity does not essentially change the Jeans' criterion of gravitational instability. It is also shown that for the propagation transverse to the direction of magnetic field. the finite conductivity destabilizes the wave number band which is stable in the limit of infinite conductivity when the medium is considered inviscid.
Study of the Balmer Spectrum of Hydrogen from a High‐Pressure Arc Discharge. I. Spectroscopic Measurements and Plasma Analysis
Authors: Radtke R. , Günther K. 
Published: July 2007

AbstractThe Balmer spectrum of hydrogen emitted from a wall‐stabilized pulse discharge has been measured covering a pressure range between 0.1 and 1.2 MPa. The temperature achieved in the discharge varied between 13000 and 22000 K corresponding to a variation in the electron concentration between 1023 and 1024 m−3.Special consideration is given to the problems in both diagnostics and spectroscopic data acquisition.