bluuebunny/crossref_metadata_2025 huggingface dataset:
Absolute Cross Sections for the Electron‐Impact Dissociation of CF4 and CHF3 into the CFx (x = 1−3) Neutral Radicals
Authors: Sugai H. , Toyoda H. , Nakano T. , Goto M.
Published: July 2007

The electron‐impact energy dependence of the dissociation cross sections of CF4 and CHF3 into the CFx (x = 1 − 3) free radicals was previously reported, in which the absolute values of the cross sections were tentatively estimated based on certain assumptions for the unknown ionization cross sections of the CF2 and CF radicals. These assumptions are no longer needed, since a complete set of absolute parent and dissociative ionization cross sections of CFx radicals has been reported recently by Becker and co‐workers. Based on these data, the absolute cross sections for the electron‐impact neutral dissociation of CF4 and CHF3 into CF3, CF2 and CF from the threshold up to 200–300 eV have now been accurately calibrated. Adjustments to the previously reported absolute cross sections of up to a factor of 16 were necessary.
Calculated Cross Sections for Double and Triple Ionization of Atoms by Electron Impact
Authors: Deutsch H. , Becker K. , Märk T. D.
Published: July 2007

The semi‐empirical Deutsch‐Märk (DM) formalism for the calculation of absolute cross sections for the single ionization of atoms has been extended to the calculation of cross sections for the double and triple ionization of ground state atoms. Detailed comparisons are made with available experimental data from threshold to 200 eV. In general, we find good agreement between the present calculations and the available experimental data. On that basis, we feel confident that the present formalism can be applied to predict double and triple ionization cross sections for those atoms, for which no experimental data are currently available, with an accuracy in the 30–50% range for impact energies where direct ionization processes dominate and where contributions from tightly bound inner shells can be neglected. This level of precision should be sufficient for modelling purposes and many other practical applications.
Enhanced Negative Ion Formation in ArF‐Laser‐Irradiated Methane: Possible Implications for Plasma Processing Discharges
Authors: Pinnaduwage L. A. , Martin M. Z. , Christophorou L. G.
Published: July 2007

Oberservation of enhanced electron attachment to ArF‐excimer‐laser irradiated methane is reported. Preliminary evidence is presented that laser‐excited superexcited states of CH4 (or other excited states to which these convert) are responsible for the observed enhanced electron attachment, and, that predominantly H− ions are produced via this process. The possible significance of this process for plasma processing discharges using CH4 and its mixtures is indicated.
The Effect of a Magnetic Field on the Hβ Line Emission from a T‐Tube Plasma
Authors: Mijatović Z. , Djurović S. , Pavlov M. , Kobilarov R. , Vujičić B. T.
Published: July 2007

The influence of a magnetic field on the emission of the Hβ line in a T‐tube plasma was investigated. Applied magnetic fields were 0.5 T and 2.1 T. The Hβ line profiles recorded under the same conditions in the presence and in the absence of the magnetic field were compared. We observed a small red‐shift of the lines emitted along the magnetic field lines. A qualitative explanation of this effect is given.
Nonlinear Interactions of the Surface Waves Propagating at the Plasma‐like Medium‐Metal Interface
Authors: Ostrikov K.
Published: July 2007

The nonlinear three‐wave interactions of the surface waves (SW) which exist at the plasma‐like medium‐metal interface are considered. The studied SW are caused by collective phenomena in the plasma‐like medium and propagate across an external magnetic field which is parallel to the interface. The wave coupling coefficients are obtained in the most general form and are expressed through the second order nonlinear susceptibilities. The simple case when the plasma‐like medium allows a hydrodynamical description is considered as well. The conditions providing the most effective interaction between the waves are discussed and the analytical expressions describing the amplitude evolution of the SW under such interaction are given. The possibility of realization of a parametric generator based on the SW nonlinear interaction is discussed. The characteristic length of the nonlinear medium providing the effective interaction is estimated for several important cases.
Langmuir Probe Determination of Charged Particle Number Density in a Flowing Afterglow Plasma
Authors: Chudáček O. , Kudrna P. , Glosík J. , Šícha M. , Tichý M.
Published: July 2007

Experimental study of the electron and ion density determined by Langmuir probe is presented. The probe data have been obtained on FALP apparatus for electron (and ion) number densities ranging from 1012 m−3 to 1016 m−3, at electron temperatures equal to room temperature and also roughly ten times higher and at neutral pressures from 60 Pa to 150 Pa.

The number densities of electrons for all measured probe data have been deduced from the electron current to the probe at the space potential and also by means of OML method from the electron current measured for positive probe with respect to the space potential. In the paper it is shown that in the flowing afterglow plasma the values of the electron density determined according both methods are in a good agreement and it is possible to take them as the reference number density for comparison with apparent ion densities obtained from the ion current.

The number densities obtained from the ion currents in the ion accelerating region (negative probe with respect to the space potential) according to different applicable probe theories have been compared with reference value. It is found that the best agreement between the number densities evaluated from the electron current and from the ion current gives the theory of ion collection by Tichý et al. [16], which takes into account the collisions of ions with neutrals in the space charge sheath around the probe provided that the conditions correspond to the OML regime.
The Conversion of NOx in a Corona Discharge with an Electrode Material Variation
Authors: Hensel K. , Morvová M.
Published: July 2007

The spatial and surface chemical products and effectiveness of NOx removal (abbreviated deNOx) under the corona discharge action at atmospheric pressure were investigated. The influence of high‐voltage electrode material on a discharge character and the heterogeneous influence of the electrode surface are also reported in the article. The qualitative analysis was performed using infrared absorption spectrometry. Special attention was paid to NO and NO2 calibration measurements.
Progress in Integrated 2‐D Models for Analysis of Scrape‐Off Layer Transport Physics
Authors: Rognlien T. D. , Braams B. J. , Knoll D. A.
Published: July 2007

We present the status of comprehensive two‐dimensional (2‐D) transport modeling for the tokamak scrape‐off layer (SOL) using the UEDGE and B2.5 codes. These codes are now able to integrate a variety of physics, including coupling of plasma and neutral transport leading to detachment, complicated divertor‐plate geometries, multispecies impurities, and currents and E × B drifts. These new models are outlined and the capabilities are illustrated by a number of examples that emphasize the importance of including the 2‐D geometry.
Phenomenology of Flute‐Like Perturbations in the Divertor Region
Authors: Cohen R. H. , Ryutov D. D.
Published: July 2007

A very strong squeezing of the flux‐tube passing near the divertor X‐point should make impossible existence of flute‐like perturbations connecting the divertor plate and the median part of the SOL. On the other hand, some of the current experimental observations imply that such perturbations do exist. In the present paper we consider possible resolutions of this apparent paradox for some specific experimental situations: short divertor legs; presence of a cold plasma in the divertor legs; and excitation of the modes with small toroidal wave numbers.
SOL Studies for Finite‐β Helias Equilibria
Authors: Strumberger E.
Published: July 2007

The suitability of the island divertor concept developed for Wendelstein 7‐X is investigated for various finite‐β Helias magnetic fields with average β‐values up to 〈β〉 = 0.04. For this purpose, the magnetic field structures of these finite‐β fields, which have been computed with the NEMEC+MFBE code, are studied in detail in the edge region.
Kinetic Theory Analysis of Sheaths and Shocks
Authors: Ryutov D. D.
Published: July 2007

The properties of sheaths formed on the divertor plates have a strong influence on plasma behavior in the scrape‐off‐layer. What makes these properties quite different from those of „standard”︁ Debye sheaths is that the magnetic field in the SOL intersects divertor plates at a shallow angle. The survey covers the following issues of the sheath physics in an oblique magnetic field: sheath structure and particle trajectories; effect of diamagnetic and electric drifts on the current‐voltage characteristics of the sheath; effect of the surface „roughness”︁ and „waviness”︁ on sheath properties and plasma transport; possible role of the anomalous transport, etc. The second class of objects briefly discussed in the present survey are shock waves which can appear in the divertor region if the incoming plasma flow is supersonic. The outline of the kinetic theory of impurity retention by the shocks is presented.
Kinetic models of ELMs burst
Authors: Sigmar D. J. , Batishcheva A. A. , Batishchev O. V. , Krasheninnikov S. I. , Catto P. J.
Published: July 2007

Fluid descriptions can fail for fast processes such as Edge Localized Mode (ELM) [1] bursts because plasma transport properties may be affected by incomplete Maxwellization of plasma particles. In this case only kinetic plasma descriptions of ELMs can give qualitatively correct results. In the present work we propose three different models of ELM propagation in the scrape‐off‐layer (SOL). We also present the first results of the kinetic modeling of the propagation of ELM bursts along the magnetic field, towards the target in a SOL plasma. These simulations are performed with a 1D2V finite element Fokker‐Planck code ALLA [2] and with a 2D PIC code W2 [3].
Toroidal Wall Heat Flux and Conductivity Profiles due to Neutral 3D Turbulence in the Gas Blanket Regime for Divertors
Authors: Vahala G. , Vahala L. , Morrison J. H. , Krasheninnikov S. , Sigmar D. J.
Published: July 2007

3D neutral fluid turbulence is considered within the gas blanket regime in front of the divertor plate. For 2D mean flows over toroidal cavities, it is shown that the turbulence leads to enhanced conductivity profiles as well as strongly increased heat flux to the toroidal walls. For ITER‐like divertors, these effects significantly lengthen the gas blanket regime to protect the target ‐ which under laminar conditions would not occur.
Plasma Recombination and Divertor Detachment
Authors: Krasheninnikov S. I. , Pigarov A. Yu. , Sigmar D. J.
Published: July 2007

We consider the influence on plasma recombination of the formation of negative and molecular ions in divertor plasma. We take into account different atomic processes (vibrational excitation of molecular hydrogen, electron dissociative attachment, ion conversion, charge exchange and dissociative recombinations, dissociation and ionization, etc.) and find the expression for the effective plasma recombination rate constant from a suitably reduced set of coupled rate equations. We estimate the influence of the recombination process on divertor plasma behavior and find that for AlcatorC‐MOD like parameters plasma recombination due to negative and molecular ions becomes significant in the temperature range below a few eV. We conclude that plasma recombination is a strongly contributing mechanism for the explanation of divertor plasma detachment in low temperature plasmas.
Simulation of an ITER‐Like Dissipative Divertor Plasma with a Combined Edge Plasma Navier‐Stokes Neutral Model
Authors: Knoll D. A. , McHugh P. R. , Krasheninnikov S. I. , Sigmar D. J.
Published: July 2007

A combined edge plasma / Navier‐Stokes neutral transport model is used to simulate dissipative divertor plasmas in the collisional limit for neutrals on a simplified two‐dimensional slab geometry with ITER‐like plasma conditions and scale lengths. The neutral model contains three momentum equations which are coupled to the plasma through ionization, recombination, and ion‐neutral elastic collisions. The neutral transport coefficients are evaluated including both ion‐neutral and neutral‐neutral collisions.
Neutral Gas Transport Calculations for ITER
Authors: Grossman A. , Schmitz L. , Merriman B. , Najmabadi F.
Published: July 2007

In modeling the neutral transport in the edge plasma for tokamak divertor design, geometry can play as important a role as the plasma density and temperature profiles. We have developed a novel interface between the neutral transport code, DEGAS, and CAD images of the tokamak and magnetic field geometry, which provides an accurate representation of the wall geometry for neutral transport modelling. In addition to superior spatial resolution of the vessel geometry, the interface allows subset regions of special interest to be selected out for modeling and permits the wall geometry to be readily modified by point and click techniques. Neutral transport results for the two divertor geometries under consideration for ITER, the gas bag design and the v‐shaped target design, are presented.
Effects of Neutral Gas Collisions and an Expanding Magnetic Field on Plasma Flow in a Divertor Chamber
Authors: Sato K. , Kameda S. , Katayama H. , Miyawaki F.
Published: July 2007

A divertor plasma is treated using a kinetic model to evaluate impurity control effects of an expanding magnetic field and effects of plasma‐neutral collisions on power transmission in a divertor chamber. Cold ions of fuel and ionized impurities are effectively trapped in the divertor chamber by the electrostatic potential caused by magnetic expansion if the ionization rate is smaller than an upper limit. Plasma‐neutral collisions remarkably reduce the impact energy of ions reaching the divertor plates through removal of energetic ions and through reduction of the potential drop in the divertor chamber.
Modelling of Scrape‐Off Layer Biasing Experiments
Authors: van Schoor M. , Baelmans M. , Weynants R. R.
Published: July 2007

Based on the extended B2‐code a method has been developed to simulate electrode as well as divertor biasing experiments. To improve the convergence speed of the code a new implicit discretisation scheme for the potential equation based on the Braginski equations was implemented, incorporating viscosity and pressure gradient effects in the expression for the radial current.

The organisation of the article is as follows: In a first paragraph a short introduction about the B2‐code and the additional equations that determine the electric field and the currents is given. Paragraph 2 deals with electrode and divertor biasing. Some results are shown. Next, a new discretisation scheme to improve the previous one is discussed.
Review of the experimental verification on the enhancement of edge turbulence by biasing
Authors: Nedospasov A. V.
Published: July 2007

Well‐known the theoretical studies deal with two mechanisms of turbulence suppression by the shear of the poloidal rotation velocity and due to the plasma shift to inner board over a time shorter than the inverse increment. In paper1 the possibility of increasing the level of edge turbulence by a limiter current was pointed out. The enhancement of the turbulence is possible due to the variation of the sheath potential at the plasma‐ surface boundary provided that the positive current flows to the surface. In this brief review a new experimental results which were obtained by biasing in different tokamaks are discussed. The earlier observations of turbulence changing with biasing were considered in1. For instance, an increase of the flow potential fluctuations in the SOL up to e/Tc > 3 was observed in TEXTOR.
Transverse Conductivity and Theory of a Probe in a Magnetized Plasma
Authors: Rozhansky V. , Ushakov A. , Voskoboynikov S.
Published: July 2007

The I‐V characteristics in a fully ionized plasma are calculated for the probes larger than the ion gyroradius. The shape of the characteristics is crucially effected by the transverse conductivity caused by the perpendicular ion viscosity.
Two‐Dimensional Divertor Modeling and Scaling Laws
Authors: Catto Peter J. , Krasheninnikov S. I. , Connor J. W. , Knoll D. A.
Published: July 2007

Two‐dimensional numerical models of divertors contain large numbers of dimensionless parameters that must be varied to investigate all operating regimes of interest. To simplify the task and gain insight into divertor operation, we employ similarity techniques to investigate whether model systems of equations plus boundary conditions in the steady state admit scaling transformations that lead to useful divertor similarity scaling laws. A short mean free path neutral‐plasma model of the divertor region below the x‐point is adopted in which all perpendicular transport is due to the neutrals. We illustrate how the results can be used to benchmark large computer simulations by employing a modified version of UEDGE which contains a neutral fluid model.
Massively Parallel Fokker‐Planck Code ALLAp
Authors: Batishcheva A. A. , Batishchev O. V. , Krasheninnikov S. I. , Sigmar D. J. , Koniges A. E. , Craddock G. G. , Djordjevic V.
Published: July 2007

The recently developed for workstations Fokker‐Planck code ALLA simulates the temporal evolution of 1V, 2V and 1D2V collisional edge plasmas [1]. In this work we present the results of code parallelization on the CRI T3D massively parallel platform (ALLAp version). Simultaneously we benchmark the 1D2V parallel vesion against an analytic self‐similar solution of the collisional kinetic equation[2]. This test is not trivial as it demands a very strong spatial temperature and density variation within the simulation domain.
Shear Viscosity and Temperature Inequalities for Multi‐Species Plasmas
Authors: Suchy K.
Published: July 2007

The first coefficients in the orthogonal expansions of the velocity distribution functions with respect to Grad's tensorial (three‐dimensional) Hermite polynomials are shown to be proportional to ther‐modynamic fluxes, if the weight functions are local Maxwellians centered at the mean mass velocity and widened with a mean temperature. Balance equations for the stress tensors are established and reduced to linear algebraic systems under certain restrictions. Explicit solutions for the traces and the tracefree parts of the stress tensors are given.
Response of the Electron Kinetics on Spatial Disturbances of the Electric Field in Nonisothermal Plasmas
Authors: Sigeneger F. , Winkler R.
Published: July 2007

An efficient method for solving the inhomogeneous electron Boltzmann equation for a weakly ionized collision dominated plasma is represented. As a first application this method is used to investigate in a helium plasma the response of the electron velocity distribution function and of the relevant macroscopic quantities to the impact of spatially limited disturbances in the electric field. In addition to the field action elastic and (conservative) inelastic collisions of electrons with gas atoms are taken into account in the kinetic treatment. In this way the spatial relaxation behaviour of the electrons and their establishment into homogeneous plasma states could be studied on a strict kinetic basis. Unexpectedly large relaxation lengths in electron acceleration direction have been found at medium electric fields.
Density Distribution of Plasma Species in a Hollow Cathode Arc Discharge for Coating Application
Authors: Mönke D. , Scheibner H. , Mechold L. , Becker W. , Schrade F.
Published: July 2007

The plasma of a hollow cathode arc discharge (argon/titanium) was studied by emission spectro‐scopy and probe measurements. The behavior of the relative particle concentrations of the different heavy plasma components as well as the concentration and temperature of the electrons was determined as function of the vertical distance from the anode crucible.

Abel‐inverted radial distributions of the relative level populations for TiI (neutral titanium), TiII (singly ionized titanium), Ar I and ArII are presented. Further measurements characterize the influence of the discharge current on the relative level population.
Electron Surface Cyclotron Waves in the Metallic Waveguide Structures with Two‐Component Filling
Authors: Girka V. O. , Girka I. O. , Kondratenko A. M. , Pavlenko I. V.
Published: July 2007

The dispersion properties of the slow electromagnetic surface waves propagating across external magnetic field in planar metallic waveguides with plasma and dielectric filling on the harmonics of the electron cyclotron frequency are studied in this paper. The external steady magnetic field is supposed to be directed perpendicularly to the waveguide wall. Dielectric layer separates semibounded plasma from the metallic wall. The analytical research is carried out using the kinetic description for plasma particles, the mirror reflection model for the interaction between particles and plasma boundary. Skin depth of the surface cyclotron waves (SCW) is much greater than electron Larmor radius. Effect of the following parameters of the waveguide structures: dielectric constant and thickness of the dielectric layer, plasma density value and number of the cyclotron harmonics, on the SCW dispersion is examined both analytically and numerically.
On Various Kinds of Dielectric Barrier Discharges
Authors: Müller S. , Zahn R.‐J.
Published: July 2007

Dielectric barrier discharges in Xe and Ne/Xe, He/Xe mixtures are investigated with regard to the ranges of existence of various discharge types over a wide range of parameters (total gas pressure p, electrode distance d, frequency f and mixture ratio X). The discharges were explained in more detail because of the bistable behaviour and the transfered charges, partly of the peak current and the maximum of the visible radiation pulse. The time behaviour of the discharge was observed, too. In this paper a distinction of various discharge types could be achieved by the similarity parameters f/p and pd. The charge carriers remaining in the volume and long‐living plasma species could be identified as essential mechanisms for the development of various types of discharges. The influence of space charges on the bistable behaviour could be shown indirectly.
Shock Waves due to Grain‐Charge Variation in Dusty Plasmas
Authors: Popel S. I. , Yu M. Y. , Tsytovich V. N.
Published: July 2007

Nonlinear electrostatic wave structures in plasmas containing variable‐charge dust grains, Boltz‐mann electrons, and inertial ions are investigated. The charge variation is assumed to be caused by electron and ion currents at the grains. It is found that intense shock waves can exist. The dissipation in such shock waves originate from the process of dust charging.
Analytical Results for the Boltzmann Equation
Authors: Toepffer C. , Cercignani C.
Published: July 2007

The manifold of solutions of the Boltzmann equation in the relaxation time approximation for particles in a constant field is obtained in closed form. The Green's function for the infinite domain and the moments of the probability distribution are calculated explicitly. A generalized drift‐diffusion equation with local temperatures is obtained by matching moments. The Green's function for the finite domain is derived for vanishing equilibrium temperature β → ∞ in a ballistic regime of large momentum gain between collisions.
Strict Kinetic Treatment of the Electron Response to Spatial Field Disturbances in Nonequilibrium Plasmas
Authors: Petrov G. , Winkler R.
Published: July 2007

In generalization of former approaches for the simplified solution of the inhomogeneous electron Boltzmann equation a higher order solution technique has been developed. This technique is based on a multi‐term expansion of the electron velocity distribution function and allows a strict study of the electron kinetics in plasmas acted upon by space‐dependent electric fields. This solution technique is used to investigate the response of the plasma electrons to spatially limited disturbances of the electric field in weakly ionized plasmas of helium and mercury. By solving the kinetic equation with increasing order of the multi‐term expansion the convergent solution of the kinetic problem and thus the strict spatial behaviour of the velocity distribution and of significant macroscopic properties of the electrons has been determined and analysed. Furthermore, the impact of higher order terms of the expansion has been revealed and the falsification of the velocity distribution and of related macroscopic properties has been evaluated when instead of the multi‐term solution the simpler two‐term solution of the kinetic equation is used.
Cross‐Field Diffusion by Charge Changing Processes
Authors: Fussmann G.
Published: July 2007

The particle transport induced by ionization, recombination and charge exchange processes in magnetically confined plasmas is analyzed. For ions with charge numbers Z ≧ 2 a random walk is caused by the fluttering of the gyro‐radius as a result of successive recombination and ionization events. The corresponding diffusion coefficient, however, is very small and may be neglected even in the case of high‐energy alpha particles being produced in fusion plasmas. Single and neutral particles are subjected to joint transport across the magnetic field due to their unimpeded motion during the short atomic phases. It is found that this mechanism is more important than classical transport over a wide temperature and density range. The corresponding diffusion coefficient D1 = f(Te)Ti/mine is independent of the magnetic field strength and shows an electron temperature dependence which can be expressed in terms of the rate coefficients for ionization, recombination and charge exchange. The latter effect leads to a strong reduction of the diffusion process in hydrogen plasmas. Diffusion coefficients comparable with anomalous values of about 1m2/s are therefore reached only for cool (divertor) plasmas with T < 5eV.
Effective Radiative Lifetimes
Authors: Lange H. , Leipold F.
Published: July 2007

Measurements of trapped decay rates for the xenon 146.9 nm resonance transition in the positive column of low current xenon discharges are reported. These rates, also called “effective lifetime of resonance photons”, were measured in contrast to other authors in an active discharge by means of a laser produced disturbance in the density of the 6s[3/2]1‐xenon resonance atoms at the discharge axis. The 146.9 nm radiation resulting from this temporary overpopulation was measured and then analysed for the determination of the trapped decay rates. The dependence of the measured quantities of tube diameter is discussed. A comparision with decay rates obtained by other experimental methodes and simulations of resonance radiation trapping shows good agreement.
The Scaling of the Edge Temperature in Tokamaks Based on the Alfven Drift ‐ Wave Turbulence
Authors: Kerner W. , Igitkhanov Yu. , Janeschitz G. , Pogutse O.
Published: July 2007

The stability analysis of Alfven drift type modes leads to a threshold condition for the L‐H transition. This condition yields the scaling for the edge temperature, which is in agreement with the experimental results.
Poloidal Pressure Gradients, Divertor Detachment and Marfes
Authors: Schaffer M. J.
Published: July 2007

Because the radiation power density from a marfe scales approximately as the square of its plasma pressure, and since increased radiation would aid divertor detachment for high power tokamaks, this paper identifies regions that might permit locally increased plasma pressure in steady state. The magnetic and dynamic (flow) constraints of magneto‐hydrodynamics (MHD) are examined for self‐consistent locally increased pressure equilibria, in both the magnetically open tokamak scrape‐off layer (SOL) and the closed surfaces just inside the last closed flux surface. In most tokamak geometries it is difficult to recycle particles at a sufficient rate to sustain high pressure marfes, but they might be possible near a divertor X‐point.
Time‐dependent modelling of impurity transport in the jet core and divertor plasma
Authors: Taroni L. Lauro , Corrigan G. , Simonini R. , Spence J. , Springmann E. , Taroni A. , Andrew P. , Giannella R. , Harbour P. J. , Horton L. D. , Ingesson L. C. , Lawson K. , Maggi C. F. , Monk R. D. , O'mullane M. , von Hellermann M.
Published: July 2007

The analysis of the contamination of the plasma by a puffed recycling impurity, such as neon, is intrinsically time‐dependent and requires simultaneous time‐dependent modelling of both the core region and the SOL and divertor region. To this end, a new code, combining core and edge codes, has been developed: its main features will be described and its application to the analysis of an L‐mode discharge in which neon was puffed will be shown.
Modeling of neutral plasma in a divertor in the fluid‐kinetic transition
Authors: Karney C. F. F. , Stotler D. P. , Braams B. J.
Published: July 2007

The neutrals in a tokamak divertor in the so‐called “detached” mode of operation may be in a kinetic regime (long mean free path) in some regions and in a fluid regime (short mean free path) elsewhere. For example, a kinetic description is necessary in the thin ionization front, while the cold neutrals in front of the divertor plate are adequately described by fluid equations. The paper describes a way to model this by coupling existing Monte Carlo neutral transport and plasma fluid codes. This is explored with a simple analytical model.
Lattice Boltzmann Representations of Neutral Gas Hydrodynamics
Authors: Krasheninnikov S. I. , Catto Peter J.
Published: July 2007

Lattice Boltzmann prescriptions attempt to replace continuous Navier‐Stokes equations with kinetic equations on a discrete lattice on which particles are only allowed to move to other lattice sites during each time step. We employ a Grad procedure to find the constraints which must be satisfied to model a monatomic gas in a long scale length limit. A non‐invariant form of the equilibrium function allows us to reduce the number of sub‐lattices which are needed to compensate for non‐physical lattice effects and recover the exact Navier‐Stokes equations.
Hydrogen Equation of State and Plasma Phase Transition
Authors: Beule D. , Ebeling W. , Förster A. , Juranek H. , Redmer R. , Röpke G.
Published: July 2007

We combine equations of state valid for the dense, neutral fluid and the dense, fully ionized plasma to obtain a new equation of state for the intermediate region where partial dissociation and ionization occur. A region of thermodynamic instability is found which is known as plasma phase transition. Hugoniots curves are calculated and compared with experiments and other theories.
Electrical Conductivity in Dense Hydrogen Fluid and Metal Plasmas
Authors: Redmer R. , Röpke G. , Beule D. , Ebeling W.
Published: July 2007

Recent shock‐wave experiments on fluid hydrogen have shown that a transition from nonconducting to metallic‐like conductivity occurs at Mbar pressures. On the other hand, a transition from metallic to non‐metallic conductivities has been observed in aluminum and copper plasmas at about 0.1 solid state density using the rapid wire evaporation technique. The equation of state and composition of both shock‐compressed hydrogen and expanded metals are calculated within a partially ionized plasma model. The conductivity is determined in linear response theory taking into account all relevant scattering processes of free electrons on T matrix level. Reasonable agreement with the experiments is found.
Bloch Equations in Dense Plasmas
Authors: Schepe R. , Tamme D. , Henneberger K.
Published: July 2007

In this paper we discuss pulsed laser excitation, which is nearly resonant with an atomic transition in a partially ionized plasma. The dynamics of particles and the external laser field is microscopically described by a Green's function approach on the one‐ and two‐particle level. Particularly for the (1s → 2p) transition of hydrogen the influence of the particle density, laser intensity and detuning on the polarization dynamics is discussed. Treating the collision integral with the Lipavsky ansatz allows to determine the relaxation times T1 and T2 for the inversion and the polarization. These relaxation times vary from the ps scale (in the low‐density case) to the fs region (at high densities). Considering the pulse duration in comparison with the relaxation times, the Markovian limit is valid for moderate and high densities, whereas the low‐density case requires a non‐Markovian computation.
Nonequilibrium Two‐Particle Dyson Equation
Authors: Bornath Th. , Schlanges M. , Kremp D.
Published: July 2007

The two‐particle problem within a nonequilibrium many‐particle system is investigated in the framework of real‐time Green's functions. A nonequilibrium Dyson equation is given for the two‐time two‐particle Green's function. The two‐particle self‐energy in this equation consists of two qualitatively different parts: one part is local in time, whereas the other part is a two‐time quantity having thus a dynamical character. The latter part of the self‐energy can be expressed in terms of multi‐particle Green's functions.
Dielectric Properties of Dense Femtosecond Laser Produced Plasmas
Authors: Kingham R. , Theobald W. , Hässner R. , Sauerbrey R. , Fehr R. , Gericke D. O. , Schlanges M. , Kraeft W.‐D. , Ishikawa K.
Published: July 2007

The XUV optical properties of dense plasmas are investigated experimentally and theoretically. We calculate the dielectric function of a dense carbon plasma including effects of higher density. These dielectric functions are then used together with transmission measurements of high‐order harmonics through dense foil plasmas to obtain the initial electron density and temperature.
Electron Dynamics and Anderson Localization in Wigner Formulation of Quantum Statistical Mechanics
Authors: Filinov V. S. , Lozovik Yu. E. , Filinov A. V. , Zacharov I. E.
Published: July 2007

The new numerical approach for consideration of quantum dynamics and calculations of the average values of quantum operators and time correlation functions in the Wigner representation of quantum statistical mechanics has been developed. The time correlation functions have been presented in the form of the integral of the Weyl's symbol of considered operators and the Fourier transform of the product of matrix elements of the dynamic propagators. For electrons in disordered systems of scatterers the numerical results have been obtained for series of the average values of the quantum operators including position and momentum dispersions, average energy, energy distribution function as well as for the frequency dependencies of tensor of electron conductivity and permittivity according to quantum Kubo formula. Zero or very small value of static conductivity have been considered as the manifestation of Anderson localization of electrons in 1D case.
Scattering Rates and Stopping Power for Strongly Coupled Plasmas
Authors: Schlanges M. , Kosse S. , Gericke D. O.
Published: July 2007

On‐ and off‐shell scattering rates for strongly coupled plasmas are calculated in T‐matrix approximation to study the relevance of strong correlations between the plasma particles. Thermodynamic equilibrium as well as nonequilibrium plasmas are considered. On the basis of the calculated scattering rates, the stopping power is determined for ion beams in dense plasmas. These results are compared with molecular dynamic simulations. For the full T‐matrix approach, a good agreement is found for low beam velocities.
Using the Dielectric Function for Diagnostics of Laser‐Induced Plasmas
Authors: Wierling A. , Sorge S. , Röpke G.
Published: July 2007

We present an approach to the dielectric function of dense plasma based on a generalized linear response theory. The relation of this approach to the Drude model as well as to the random phase approximation is discussed. It is shown, that the dielectric function presented here obeys certain exact known properties such as sum rules. Using the dielectric function, the absorption coefficient for electro‐magnetic wave interacting with dense targets is calculated. Regions for the applicability for simplified models are given. Implications for the diagnostics of laser‐induced plasmas are pointed out.
Electron Distribution Function in a Nonideal Plasma in Strong Electric and Laser Fields
Authors: Starostin A. N. , Aleksandrov N. L. , Konchakov A. M. , Okhrimovskyy A. M. , Shchipka M. V.
Published: July 2007

Using a two‐term approximation to the kinetic equation, the generalized electron energy and momentum distribution which governs the electron transport and rate properties in nonideal plasma is analyzed. A class of general solutions of the equation is found in the model case which is widely used in semiconductor plasma. An equation that generalizes the well‐known Zeldovich‐Raizer quantum kinetic equation in the case of nonideal plasma is deduced. Explicit nonequilibrium solutions of this equation for the electron energy and momentum distribution function in a strong laser field are constructed.
Screening Enhancement of Thermonuclear Reactions in High Density Stars
Authors: Dewitt H. , Slattery W.
Published: July 2007

The screening function for zero separation for two reacting nuclei in a strongly coupled OCP plasma is obtained using new very accurate Monte Carlo OCP fluid simulation data by two methods. The first method obtains H(0), the screening function at x = 0, from the difference of free energies before and after the reaction. The second method is direct fitting of the Widom expansion in powers of x2 to the MC data for the pair distribution function, g(x). The two methods agree to 0.2%.
Modelling of Sunspot Equilibrium Considering Stratification and Temperature Gradients
Authors: Meister C.‐V.
Published: July 2007

Basing on the Schlüter‐Temesváry similarity condition for the magnetic flux in sunspot regions, on experimental horizontal profiles for the absolute value of the magnetic induction, and, for the first time, also on horizontal and vertical hydrodynamic momentum balances, analytical expressions for horizontal and altitudinal dependencies of the magnetic induction and the kinetic pressure of the sunspot plasma are derived.
Kinetics of the Charging Process in Dusty Plasmas
Authors: Trigger S. A. , Schram P. P. J. M.
Published: July 2007

On basis of the kinetic equations for dusty plasmas we consider the charging equation for grains. We suggest the local charge approximation, in which the distribution function of the charge variable is a delta‐function, so that the charge becomes a function of position and time. We also simplify the kinetic equations and analyze the influence of the charging process on the dielectric function and wave spectra.
Theory of Colloidal and Dusty Plasmas
Authors: Schram P. P. J. M.
Published: July 2007

Some highlights of the theory of colloidal and dusty plasmas are reconsidered. A minimal charge of the crystallization is established on basis of the Lindeman criterion and the theory of Brownian motion. The theory of crystal waves is compared with experimental results.
Computer Simulation of High Power Ion Beams Interaction with Matter
Authors: Fortov V. E. , Skvortsov V. A.
Published: July 2007

We are interested in a fairly wide range of high‐power ion beams (HPIB, with intensities from 1 GW/cm2to 10 TW/cm2). In modeling the action of ion beams of moderate intensity (I< 10 GW/cm2) on metal targets, elastoplastic properties are taken into account, and in describing the action of ion beams with intensitiesI> 10 GW/cm2heat transfer, including radiation processes, is considered. Computer simulations based on a system of hydrodynamic equations are supplemented with wide‐range equations of state, corresponding correlations for the calculation of the beam energy loss in the matter, parameters of energy transfer (coefficients of electronic, ionic, and radiative thermal conductivity, coefficients of optical radiation absorption), kinetics of generation and development of microcracks in solids when pulse loads are large. A possibility of simulating hypervelocity impact with the help of HPIB has been shown and the necessary conditions have been determined.
Insulator‐Metal Transition in Plasma‐like Systems
Authors: Likalter A. A.
Published: July 2007

The insulator‐metal transition in metal‐ammonia solutions near the consolute critical point has been considered using a general idea of a virtual atomic structure characteristic of plasmas with strong electron‐ion coupling.
A Comparative Study for the Equation of State of Dense Fluid Hydrogen
Authors: Juranek H. , Redmer R. , Röpke G. , Fortov V. E. , Pyalling A. A.
Published: July 2007

Recent developments in shock‐wave experimental techniques have allowed the 100 GPa range to be probed. Driven by a two‐stage gas gun (Livermore, USA) or chemical explosives (Chernogolovka, Russia), the multiple shock‐wave technique has been applied to determine the equation of state and the electrical conductivity of dense hydrogen and deuterium fluids. In single shock wave experiments driven by the NOVA laser, the principle Hugoniot curve of deuterium was determined. Interesting effects such as dissociation and the transition to metallic‐like conductivities occur under these conditions. The equations of state applied so far to analyze the experimental data are compared and a new semi‐empirical equation of state is given.
Semiclassical Dynamics and Time Correlations in Two‐Component Plasmas
Authors: Ortner J. , Valuev I. , Ebeling W.
Published: July 2007

The semiclassical dynamics of a charged particle moving in a two‐component plasma is considered using a corrected Kelbg pseudopotential. We employ the classical Nevanlinna‐type theory of frequency moments to determine the velocity and force autocorrelation functions. The constructed expressions preserve the exact short and long‐time behavior of the autocor‐relators. The short‐time behavior is characterized by two parameters which are expressable through the plasma static correlation functions. The long‐time behavior is determined by the self‐diffusion coefficient. The theoretical predictions are compared with the results of semiclassical molecular dynamics simulation.
Quantum Kinetic Theory for Laser Plasmas. Dynamical Screening in Strong Fields
Authors: Bonit M. , Bornath Th. , Kremp D. , Schlanges M. , Kraeft W. D.
Published: July 2007

A quantum kinetic theory for correlated charged‐particle systems in strong time‐dependent electromagnetic fields is developed. Our approach is based on a systematic gauge‐invariant nonequilibrium Green's functions formulation. Extending our previous analysis [1] we concentrate on the selfconsistent treatment of dynamical screening and electromagnetic fields which is applicable to arbitrary nonequilibrium situations. The resulting kinetic equation generalizes previous results to quantum plasmas with full dynamical screening and includes many‐body effects. It is, in particular, applicable to the interaction of dense plasmas with strong electromagnetic fields, including laser fields and x‐rays. Furthermore, results for the modification of the plasma screening and the longitudinal field fluctuations due to the electromagnetic field are presented.
Equilibrium Properties of H‐Plasma
Authors: Arkhipov Yu. V. , Baimbetov F. B. , Davletov A. E. , Ramazanov T. S.
Published: July 2007

The equilibrium properties of the dense semiclassical hydrogen plasma are investigated by chain of Bogolyubov equations. The pseudopotential model, taking into account both short‐range quantum‐mechanical effects and long‐range many‐particle screening ones, is proposed. The equation of state of hydrogen plasma is investigated.
A restaining method to restore faded fluorescence in tissue specimens for quantitative confocal microscopy
Authors: Huisman André , Ploeger Lennert S. , Dullens Hub F. J. , Beekhuis Jan T. C. , Diest Paul J. van
Published: July 2007

The aim of this study was to develop a procedure to remove the TO‐PRO‐3 fluorescent dye from tissue sections and restain with TO‐PRO‐3, still allowing calculation of DNA content and distribution by confocal laser scanning microscopy (CLSM). This would allow repeated measurements on the same tissue sections and prevents loss of tissue material from valuable clinical samples. Thick sections (14 μm) were cut from a paraffin block of adrenal tissue and stained using TO‐PRO‐3. Image stacks were acquired by CLSM. Thereafter, three destaining approaches were tested based on incubation, at different temperatures and durations, in the medium that is normally used to dissolve TO‐PRO‐3. The same areas were imaged again to measure residual fluorescence and were subsequently restained and imaged again. The intensity of the images acquired after initial staining and restaining were compared. A number of 3‐D (texture) features computed after segmentation of nuclei were compared as well. The best destaining result was obtained by incubation of sections at 37°C in preheated medium twice for 20 min. On average, the 3‐D feature values were comparable with those after initial staining. With the described protocol it is possible to remove TO‐PRO‐3 fluorescence from tissue sections that can successfully be restained with minimal influence on fluorescence intensity and nuclear chromatin distribution. © 2007 International Society for Analytical Cytology
France telecom's introduction of switched broadband business services
Authors: Richard C. , Riviere P. , Guiomar J. , Poirier A. , Le Bihan E. , Veyres C.
Published: July 2007

In order to cope with the growth of video transmissions in France, France Telecom will commercially introduce switched broadband business services by June 1990. A broadband network based on a meshed network of optical fibres will provide one‐way point‐to‐multipoint (including point‐to‐point) connections, available on reservation. This network will link non‐blocking 32 × 32 or 64 × 64 space switches that can cross‐connect different signals, including analog SPFM (square pulse frequency modulation) video, HDB3 34 Mb/s and CMI 140 Mb/s digital signals.
The use of ATM techniques in an evolutionary access scenario
Authors: Carter W. T. , Johnson S. A.
Published: July 2007

The paper describes an approach to providing an integrated access environment from customers to the network, as an example of the new access techniques whose performance and control must be considered. The ability of ATM‐based systems to satisfy the needs of such networks is discussed, and the distinctive control and performance requirements of ATM are considered.
A connection acceptance algorithm for ATM networks based on mean and peak bit rates
Authors: Wallmeier Eugen
Published: July 2007

A connection acceptance algorithm for pipes in ATM networks is presented, which allows statistical multiplexing of heterogeneous ATM traffic. The decision to accept an incoming connection is based on the mean and the peak bit rates of the incoming and existing connections. Conditions are presented, under which the algorithm guarantees that the cell loss probability of every virtual connection does not exceed a predefined permissible probability. Examples are presented which show the gain which can be reached by statistical multiplexing.