bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pseudopotential Approach to the Thermodynamic Functions of a Dense Hydrogen‐Like Plasma
Authors: Gombert M.‐M. , Minoo H. 
Published: July 2007

AbstractPseudopotential approach allows to include the quantum mechanical effects and eliminates the short range classical divergence. At high temperature, when the De Broglie wavelength for a pair of particles, , is larger than the Landau length, Lij, we have to introduce quantum mechanics. For two point‐charge particles without screening, we study the pseudopotential, uij(r), numerically. We give expansions of the pair radial distribution function, gij(r) ( = exp(—βuij(r))) in increasing powers of . For a pair of electrons, exchange effects are taken into account. With these pseudopotentials, we study a dense multicomponent plasma using classical methods and we evaluate thermodynamic functions.
Electrical Conductivity of Partially Ionized Na‐Cs Plasma Mixtures
Authors: Bialas F. , Schmidt K. , Schlanges M. , Redmer R. 
Published: July 2007

AbstractThe electrical conductivity of partially ionized sodium‐cesium plasmas is calculated starting from the electron kinetic equation taking into account the electron‐electron, electron‐ion and the elastic electron‐atom scattering. The transport cross sections follow from the scattering phase shifts solving the corresponding Schrödinger's equation with effective interaction potentials. In order to calculate the plasma composition a coupled law of mass action is used. The electrical conductivity of the plasma mixture is then discussed for densities 1016…1021cm−3and for temperatures 3000 K… 10000 K.
On the Influence of the Pauli Exclusion Principle on the Transport Properties of Dense Coulomb Systems
Authors: Schmidt M. , Janke Th. , Redmer R. 
Published: July 2007

AbstractWithin a model calculation the influence of the Pauli exclusion principle on the electrical conductivity of a fully ionized and degenerate hydrogen plasma is investigated. Basing on a quantum kinetic equation solved with the relaxation time ansatz, the electron — ion contribution to the resistivity is calculated. The thermodynamical T‐matrix for electron — ion scattering processes is evaluated under special account for the Pauli blocking of the intermediate scattering states. The corresponding Bethe — Salpeter equation is solved analytically using a separable approximation of the statically screened potential.The Pauli exclusion principle has been found to give rise for a considerable enhancement of the transport cross section near the Fermi energy. Thus, degeneracy effects tend to diminish the electrical conductivity in the density — temperature region considered here.
Nonideality and Nonlinearity in Reaction‐Diffusion Plasmas
Authors: Kremp D. , Schlanges M. , Bornath Th. , Bonitz M. 
Published: July 2007

AbstractReaction and diffusion processes in dense plasmas are investigated on the basis of quantum statistical theory.Many particle effects lead to nonlinear expressions for reaction and diffusion coefficients.In the case of ambipolar diffusion and isobarity the plasma is described by only one reaction‐diffusion equation. Travelling front solutions and droplet formation are investigated in the approximation of constant diffusion. The influence of nonlinearity of the diffusion on these solutions as well as the possibility of phase separation via spinodal decompoisition and the formation of stable droplets are discussed.
Reaction‐Diffusion Equations for Dense Plasmas
Authors: Schlanges M. , Bornath Th. 
Published: July 2007

AbstractA derivation of reaction‐diffusion equations for dense plasmas is given on the basis of quantum kinetic theory. Explicite expressions for the diffusion and reaction rate coefficients with a non‐linear density dependence can be obtained which are valid for nonideal plasmas.
Gravitational Instability of a Rotating Viscous Thermally Conducting Plasma
Authors: Mehta Vijay , Bhatia P. K. 
Published: July 2007

AbstractThis paper deals with the gravitational instability of an infinite homogeneous viscous rotating plasma of finite electrical conductivity in the combined presence of effects of Hall currents, finite Larmor radius (FLR) and thermal conductivity. The ambient magnetic field is assumed to be uniform and acting along the vertical direction. Both longitudinal and transverse modes of wave propagation have been studied. It is shown that Jean's criterion determines the gravitational instability even in the presence of the effects of thermal conductivity, viscosity, finite electrical conductivity, FLR, rotation and Hall currents. Further it is found that while FLR, viscosity and rotation have a stabilizing influence, both the thermal and the electrical conductivities have a destabilizing influence on the gravitational instability of a plasma.
Inreased Power Concentration and its Effect on the Discharge Parameters on the Low Pressure Hg‐Rare Gas Positive Column III. Effects of an Axial Rod
Authors: Kreher J. , Stern W. 
Published: July 2007

AbstractAfter the investigation of the influence of current and tube radius on the power concentration of the Hg‐rare gas discharge in the two previous parts, part III deals with the corresponding effects of additional recombination surfaces. The plasma parameters (radiant flux of the resonance lines, field strength, electron density, electron energy distribution function) are measured in a discharge tube with an axial glass rod. With increasing rod diameter and increasing distance from the tube axis radial radiation intensity distribution becomes asymmetric. The field strength increases with the radius of the rod. The dependence of the field strength and that of the radiant flux on the parameters of the discharge do not basically change. The measured UV‐radiation efficiency of the positive column is higher than that of discharges without axial rod for equal tube radius. This is attributed primarily to the changed radial electron density distribution and its effect on the collision processes.
The Harmonic Distortion Factor of the Current of Radio‐Frequency Low‐Pressure Discharges
Authors: Schade K. , Albert M. , Suchaneck G. 
Published: July 2007

AbstractIn order to characterize an r.f. low‐pressure discharge in diode systems which are capacitively coupled to the r.f. generator the content of harmonics in current and voltage is experimentally investigated. The discharge‐conditioned content of harmonics in the voltage is practically negligible. The spectrum of the discharge current is qualitatively and quantitatively dependent on the whole reactor/generator arrangement producing the discharge. For an asymmetrical diode with a self‐excited generator it is shown that the content of harmonics in the discharge current is highly dependent on the radio‐frequency voltage, the d.c. self‐bias of the r.f. electrode, the effective power and the pressure. Conclusions are discussed concerning a connection between the content of harmonics, on the one hand, and carrier‐density modulation and power dissipation at the substrate electrode, on the other hand.
Presheath and Space Charge Sheath Characteristics in Front of a Floating Wall
Authors: Teplanova K. 
Published: July 2007

AbstractThe sheath thicknesses and numbers of collisions from an infinite fluid model of the space between an atomic cold gas plasma and a planar wall are reported in dependence on the normalized ionisation, ion elastic and charge exchange collision frequences. The Bohm criterion validity, ion heating in double layer electric field, volume radiative recombination and related questions are discussed.
COmparison of Some Basic Plasma Parameters and Discharge Characteristics of Planar Magnetron Sputtering Discharges in Argon and Neon
Authors: Petrov I. , Ivanov I. , Orlinov V. , Kourtev J. 
Published: July 2007

AbstractA comparative investigation is carried out of the discharge characteristics (current‐voltage characteristic and dependence of the running voltage on the gas pressure at constant discharge current), as well as of some plasma parameters (electron temperature, floating potential and plasma potential) and densities of the ion current extracted to the substrate, for discharges in neon and argon in a planar magnetron system for sputtering with a graphite target.
Influence of Finite Larmor Radius with Finite Electrical and Thermal Conductivities on the Gravitational Instability of a Magnetized Rotating Plasma Through a Porous Medium
Authors: Vyas M. K. , Chhajlani R. K. 
Published: July 2007

AbstractAn infinitely extending homogeneous, self‐gravitating rotating magnetized plasma flowing through a porous medium has been considered under the influence of Finite Larmor Radius (FLR) and other transport phenomena. A general dispersion relation has been derived through the linearized perturbation equations. Longitudinal and transverse modes of propagation have been discussed for the rotation with axis parallel and perpendicular to the magnetic field. The joint influence, of the aforesaid parameters, does not essentially change the Jeans' criterion of instability but modifies the same. The adiabatic sonic speed has been replaced by the isothermal one due to the thermal conductivity. It is further observed that the FLR corrections have stabilizing effect for an inviscid, non‐rotating plasma, in case of transverse propagation. Rotation decreases the Larmor radius, whereas the porosity reduces the effects of rotation, FLR, and the magnetic field. Viscosity removes the effects of both, the roation, and the FLR corrections.
Nonlinear Interaction of Plasma Waves in External Magnetic Field and the Possibility of Up‐Conversion
Authors: Krivitsky V. S. , Tsytovich V. N. 
Published: July 2007

AbstractNonlinear interaction of low‐frequency resonant and high‐frequency nonresonant plasma oscillations in the presence of an external magnetic field is studied. In the case of Iongitudinal waves it is shown that the up‐conversion of plasma oscillations' energy is possible in such a system.
Stopping Power of Charged Particles II
Authors: Luft M. , Meyer T. , Kraeft W. D. , Brouwer H. H. , Schram P. P. J. M. , Strege B. 
Published: July 2007

AbstractThe stopping power and the stopping number, respectively, of charged particles are determined in the frame of the dielectric formalism in random phase approximation. The high and low velocity limits are disscussed. Numerical evalution is given for arbitrary masses of the projectile particle using a dielectric function ϵ(κ, ω) valid for all values of degeneracy. The connection with transport (e.g. electrical resistivity) is considered.
Saha Equation, Single and Two Particle States
Authors: Kraeft W. D. , Strege B. , Girardeau M. D. 
Published: July 2007

AbstractSingle and two particle properties in a dense plasma are discussed in connection with their role in the mass action law for a partially ionized plasma. The two particle bound states are nearly density independent, while the continuum is essentially shifted. The single particle states are damped, and their energy has a negative shift and a parabolic behaviour for small momenta.
Experimental Study of Nonlinear Behaviour of a Neon Glow Discharge
Authors: Wilke C. , Deutsch H. , Leven R. W. 
Published: July 2007

AbstractWe report on experimental investigations of a periodically perturbed Neon glow discharge in a parameter range where the unperturbed system is characterized by the existence of p‐ and r‐ waves. Though the experimental plasma system has many potential degrees of freedom, its phase space behaviour is low dimensional. The discharge current exhibits sequences of periodic, quasi‐periodic and chaotic states which in many aspects correspond to a dissipative circle map. Moreover experiments show that the system displays a route to chaos via formation of entrainment islands and subsequent folding and break up of the tori, which cannot be described by a one‐dimensional theory, and which has not been reported in the literature until now.
Unimolecular Decay of Metastable Cluster Anions: (O2)N−* → (O2) + O2
Authors: Scheier P. , Märk T. D. 
Published: July 2007

AbstractUnimolecular dissociation of metastable excited states of (O2)n−* into (O2) cluster anions has been detected and studied quantitatively for n in the range of 13 to 22. The apparent metastable (decay rates determined increase with cluster size in from ∼ 5000 s−1 (for n = 13) up to ∼ 8500 s−1 for n = 22).
Electron‐Acoustic Solitary Waves in a Two‐Electron Temperature Plasma
Authors: Guha S. , Asthana M. , Dwivedi C. B. 
Published: July 2007

AbstractUsing fluid model the propagation of the solitary wave has been analytically investigated in a plasma of two‐temperature electrons and ions. It is found that under suitable conditions ion‐acoustic solitons of compressive nature and electron‐acoustic solitons of rare‐factive nature can exist.
Spherical Solitons in Ion‐Beam Plasma
Authors: Das G. C. , Singh K. H. Ibohanbi 
Published: July 2007

AbstractBy using the reductive perturbation technique, the soliton solution of an ion‐acoustic wave radially ingoing in a spherically bounded plasma consisting of ions and ion‐beams with multiple electron temperatures is obtained. In sequel to the earlier investigations, the solitary waves are studied as usual through the derivation of a modified Korteweg‐de Vries (K‐dV) equation in different plasma models arising due to the variation of the isothermality of the plasmas. The characteristics of the solitons are finally compared with those of the planar and the cylindrical solitons.
Analysis of the Evolution of a Supersonically Expanding Plasma
Authors: Kroesen G. M. W. , Schram D. C. , Wilbers A. T. M. , Meeusen G. J. 
Published: July 2007

AbstractA supersonically expanding arc plasma in argon is analyzed both experimentally and theoretically. The plasma is created in a cascaded arc and extracted through a hole in the anode. It emanates in a large vacuum system, where it expands supersonically. This expansion is limited by a shock wave. After the shock wave a subsonic plasma beam is created. A quasi one‐dimensional model, based on the conservation of mass, momentum and energy is presented. The shock wave is treated as a discontinuity. The electron density, the gas velocity and the gas temperature are measured as a function of the position in the expansion by means of Stark broadening and Doppler spectroscopy. The model calculations agree well with the measurements, especially in the first part of the supersonic flow.
Spectral and Electrical Properties of a Medium Pressure, Low‐Power, RF‐Generated Postdischarge Nitrogen Plasma Jet
Authors: Dinescu G. H. , Maris O. , Musa G. 
Published: July 2007

AbstractA method for obtaining a medium pressure (p ∼ 1 torr), low power (< 100 W), RF‐generated plasma jet, suitable for chemical kinetics studies and technological applications is described. Though various supply gases can be used to create the plasma jet, only results on the properties of a nitrogen jet are given in this paper with an emphasis on some spectral and electrical characteristics. The emission spectra of the nitrogen jet are discussed and spatial distributions of the relative concentration of nitrogen or radical impurities emitting species such as N2(C3Πu, v' = 0), NH(A3Πg, v'=0) in the bulk of the postdischarge plasma are calculated from the intensity of their vibrational bands. Electrical space resolved double probe measurements and the spatial distributions of the electron density and temperature in the plasma jet are also presented. Possible applications are shortly discussed.
K‐dV Solitons and corresponding Double Layer Phenomena in a Plasma with Multiple Electron‐Temperatures
Authors: Das G. C. , Sen K. M. 
Published: July 2007

AbstractIn this paper, the various conditions under which the K‐dV solitons and double layers may be formed in a plasma that includes two electron‐temperatures are examined by deriving a “Further modified K‐dV” (FmK‐dV) equation in three dimensional space in which there is assumed to be an ambient magnetic field. Structural forms of the various ion‐acoustic waves are discussed by obtaining both soliton‐specific and double layer‐specific solitons of the FmK‐dV equation. Particular results are deduced as special cases of the more general cases.
Two‐dimensional Numerical Simulation of the Beam‐Plasma‐Discharge
Authors: Kruscha K. J. G. , Popkov N. G. 
Published: July 2007

AbstractA two‐dimensional self consistent model of the Beam‐Plasma‐Discharge (BPD) has been developed to calculate the discharge ignition of a bandlike electron beam in a discharge chamber. The discharge was considered in Argon with an initial concentration of 1014 cm−3. The model allows calculation of the time evolution of perpendicular profiles of electron density, temperature and the potential.
Scattering of a Bounded Electron Beam by Plasma Waves which are Self‐Consistently Excited by the Beam
Authors: Kruscha K. J. G. , Kachalov K. O. , Popkov N. G. 
Published: July 2007

AbstractThe nonlinear stage of the beam plasma instability of a bandlike electron beam in unbounded plasma is examined. It is shown that such an interaction is responsible for the extreme beam electron scattering that can be observed in experiments in the absence of an external magnetic field.
On the Stark Broadening Regularities Along a Homologous Sequence of the IV B Subgroup in the Periodic System
Authors: Djeniže S. , Labat J. , Konjević R. 
Published: July 2007

AbstractOn the basis of the exiting experimental results of the Stark widths we have demonstrated the existence of a Stark‐width dependence on the upper‐level ionization potential for the homologous sequence of the fourth B group of the elements in the periodic system for three types of transitions in the case of singly‐ionized atoms. On the basis of these regularities we have predicted Stark widths of some Ge II and Pb II spectral lines. Stark widths predicted for Ge II, Sn II i Pb II spectral lines were compared with our calculated values on the basis of the semiempirical and modified semiempirical formula.
Control of the Edge Transport with the Ergodic Divertor
Authors: Ghendrih Ph. , Capes H. , Nguyen F. , Samain A. 
Published: July 2007

AbstractThe diffusion and the exponential divergence of neighbouring trajectories which characterize the stochastic magnetic field are reviewed. The effect of these properties on heat and current transport leads to an increase of the radial heat diffusivity and a reduction of the toroidal electric conductivity. The finite connection length to the wall in the perturbed layer determines the regular heat and particle deposition pattern.
The Relative Importance of Wall and Target Impurity Sources in Divertor Tokamaks
Authors: Stangeby P. C. , Elder J. D. 
Published: July 2007

AbstractExperiments in JET operated with X‐point discharges have shown that wall‐produced impurity influxes can be significantly more effective at contaminating the core plasma than plate‐produced influxes. The DIVIMP (Divertor Impurity) Monte Carlo impurity production/transport code is used to study core contamination efficiency assuming a wide variety of models/assumptions for the plasma edge behaviour, including forced fuel recirculation (pumped divertor mode) and spontaneous flow reversal. It is found that for an open (X‐point) divertor geometry and for plasma conditions typical of low e operation that a wall source is ∼3‐5x more effective at contaminating the core than a target source of equal strength. For high n̄e conditions the wall source is >10x more effective than the target source.
Minimum Entropy Production Principle Applied to Decontaminating Regime in a Stochastic Layer in Presence of a Radial Electric Field
Authors: Nguyen F. , Samain A. , Ghendrih Ph. 
Published: July 2007

AbstractThe Ergodic Divertor of TORE SUPRA induces a stochastic layer at the plasma edge by creating a resonant magnetic perturbation which destroys the magnetic surfaces. A radial electric field directed outwards is then established to confine the electrons along the open magnetic field lines. This electric field tends to deconfine ions. One may then expect that it strongly influences the neoclassical ion transport. We use a variational principle of minimum entropy production to study the transport of impurity ions in the stochastic layer. In low collisionality regime, a decontaminating outwards flux of impurity ions is found, contrasting with the neoclassical inwards flux which produces the deleterious accumulation of impurity ions in the nH profile.
Properties of a Biased Divertor Scrape‐off Layer Plasma
Authors: Parbhakar K. , Lewandowski J. 
Published: July 2007

AbstractThe effect of biasing the divertor neutralization plates on the characteristic properties of the scrape‐off layer (SOL) plasma is investigated using a 1‐D fluid code along the magnetic field lines. The biasing effect is assumed to influence the e‐folding density scale length λe which is then considered as a free parameter. The model includes radiative cooling in the divertor chamber, neutral reflux from the target plate and removal of neutral particles by ionization and pumping. Since pumping can only be done from the plenum region, we compute the escape probabilities to the plenum as a function of λe and then assume that a fixed fraction of the plenum neutrals is always pumped. We find that the average escape probability decreases with λe. The plasma density and velocity distribution near the plate are considerably modified, however the influence on the temperature is modest. The flux multiplication factor can increase by as much as 50% for the range of λe considered. An increase in neutral pressure is possible for negative biasing.
Experimental Data on the Plasma Edge of TEXTOR
Authors: Hintz E. 
Published: July 2007

AbstractThe optical methods used for plasma edge diagnostics in the tokamak TEXTOR are briefly described. Results obtained in discharges without auxiliary heating are presented. Two topics will be dealt with: The composition of the flux of neutral particles emitted from the limiter and the velocity distribution of these fluxes and ‐ the influence of the low z‐impurities, characteristic for TEXTOR, on the plasma edge properties.The significance of the experimental data will be discussed and an outlook on the future work will be given.
Influence of Excited Atoms on the Plasma Refractivity
Authors: Helbig V. , Nick K.‐P. 
Published: July 2007

AbstractThe influence of excited atoms on the plasma refractivity is studied for hydrogen and argon plasmas. Using tabulated f‐values [1] in the case of hydrogen and calculated f‐values [2], [3] for argon, the index of refraction is obtained for typical are conditions. The results indicate that the accuracy of electron density determination in plasmas from laser interferometry is not severely influenced by the excited species. This is clearly a contradiction to the interpretation of the results of a similar study of hydrogen given by GLASSER et al. [4].
Numerical Modeling of the Non‐Isothermal Positive Column of an Ar+‐Laser
Authors: Zech I. , Ertl T. , Herold H. , Ruder H. , Köhler W. E. , Tiemann W. 
Published: July 2007

AbstractA hydrodynamic description of the positive column is used to study the radial variation of particle densities, drift velocities, temperatures and heat fluxes of electrons, singly‐charged ions and neutral atoms and the radial electric field. Elastic collisions between the plasma particles and neutrals as well as Coulomb collisions between ions and electrons are taken into account. The relevant equations to solve are the balance equations of particle densities, momentum, energy and the equations for the heat fluxes for each of the three studied particle types; the Poisson equation has to be added for closure. They form a system of 13 nonlinear differential equations with critical points. One singularity occurs when the ions reach the ion sound velocity which is the case inside the positive column. Therefore, a numerical method for multipoint boundary value problems was used which can also successfully handle removable singular points. The applied relaxation method is an iterative method which demands some preliminary knowledge of the solution looked for. The necessary knowledge can be retrieved from the quasineutral model and from a simplified two‐fluid model.