bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron Energy Distribution Function at Potential Drop between two Negative Ar Glow Discharges
Authors: Ohe K. , Imaeda K. 
Published: July 2007

AbstractThe electron energy distribution function was measured at the potential drops (double layer) formed between two negative Ar glows. The acceleration of the electrons by the electric field and the electron trapping due to the high plasma potential formed a double‐humped distribution function.
Stability of Self‐Gravitating Magnetized Hall Plasma with Electrical and Thermal Conductivity through Porous Medium
Authors: Chhajlani R. K. , Parihar A. K. 
Published: July 2007

AbstractThe problem of stability of a self‐gravitating, infinite homogeneous gas in the presence of magnetic field is investigated. The medium is assumed electrically and thermally conducting. The effect of porosity, electrical conductivity, thermal conductivity and Hall current is investigated on the self‐gravitating plasma flowing through porous medium. The relevant linearized equations of the problem are stated and dispersion relation is obtained. The effect of Hall current on the condition of the instability of the system is examined for both longitudinal and transverse mode of propagation and found that in longitudinal propagation Hall effect does not change the condition of instability but modifies the Alfvén wave mode. The stability of the system is discussed by applying Routh‐Hurwitz criterion and it is found that Jeans criterion determines the stability of the system. Thermal conductivity and porosity have a destabilizing influence on the medium. The general condition for instability of the system is also derived.
Diffusion Model of Saturation Current Collection by a Planar Langmuir Probe in a Strong Magnetic Field
Authors: Stanojević M. , Čerček M. , Gyergyek T. , Jelić N. 
Published: July 2007

AbstractPlasma presheath and saturation current collection by a planar Langmuir probe in a strong magnetic field perpendicular to the probe surface ares described with the diffusion model. The model takes into consideration the geometry of the probe, that is its size and shape, and dependence of the cross‐field charged particles' transport into the effective collection region of the probe on the parallel‐field transport to the probe. Experimental study of planar Langmiur probe I—V characteristics in D.C. discharge argon plasma in strong magnetic fields confirms the possibility of deriving the cross‐field diffusion coefficient, D, from the measured electron satuation current. Additional dependence of the electron saturation current on the parallel‐field diffusion coefficient, D, and the ion temperature, Ti, derived in the approximate Stangeby's study using the diffusion model of current collection by a planar surface (Stangeby, P. C., J. Phys. D: Appl. Phys. 15 (1982) 1007) can be eliminated with more rigorous calculation. Series of measurements on two neutral pressures and various magnetic fields gave reproducible values of D, approximately given by relation D ≈ (δn/〈n〉) kBTe/(eB).
About the Development of a Nonlinear Equivalent Circuit for a Neon Gas Discharge in the Oscillating Regime
Authors: Weltmann K.‐D. , Unger H. , Deutsch H. , Wesch J. , Wilke C. 
Published: July 2007

AbstractIn this paper a development of a nonlinear equivalent circuit of the column plasma in the oscillating regime with two inertial factors is demonstrated. The model is based on a theoretical description of the plasma by means of the balance equations of electrons and of metastable atoms. The circuit can be compared to the nonlinear equivalent circuit for a neon gas discharge in a homogeneous regime which we introduced in a previous paper. Both circuits posses only positive parameters of the reactances which can be calculated on the basis of elementary processes occurring in the discharge plasma.
Dependence of the Radial Profiles of the Plasma Particles Densities on the Afterglow Time in the Flowing Afterglow Plasma
Authors: Hrachova V. , Šicha M. , Hrach R. 
Published: July 2007

AbstractThe simultaneous radial and axial decay in the flowing afterglow plasma has been investigated for metastable atoms, atomic and molecular ions and electrons. The exact solution of this problem leads to a set of differential equations. The stability of the numerical solution of these equations is not clear. The aim of the present paper is to simplify the mathematical description of the problem and to solve it on the basis of experimental results obtained in the argon flowing afterglow initiated by a microwave discharge.
Phase Transitions and Elementary Processes in Astrophysical Dense Plasmas
Authors: Ichimaru Setsuo 
Published: July 2007

AbstractThis is a compilation of extended abstracts representing research activities undertaken under the Japan‐U.S. Cooperative Science Program: Phase Transitions in Dense Astrophysical Plasmas, supported jointly by the Japan Society for the Promotion of Science and by the U.S. National Science Foundation.
Lasers in High Pressure Shock Wave Research
Authors: Löwer Th. , Sigel R. 
Published: July 2007

AbstractIt is well known that pulsed lasers can generate higher pressures than any other laboratory method if their radiation is focussed onto solid matter. However, the coherence of laser light and the resulting problem of nonuniform energy deposition due to interference effects in the beam represented a severe obstacle for quantitative use in high pressure physics. This problem has now been overcome by converting the laser light into incoherent thermal soft x‐rays in laser‐heated cavities. Experiments with the ASTERIX laser in which uniform shock waves with pressures of 8 Megabars have been generated are described in detail. It is concluded that lasers may become a quantitative new tool in high pressure physics.
Structural and Electronic Aspects of the Phase Transitions of Alkali‐atom Fluids
Authors: Tarazona P. , Chacon E. , Hernandez J. P. 
Published: July 2007

AbstractWe present a study of the metal‐nonmetal and liquid‐vapor transitions of alkali‐atom fluids which integrates structural and electronic properties. The techniques are extensions of those used to study liquid metals and the phase transitions of pairwise interacting fluids. Structural correlations beyond mean‐field are found to be of special importance due to the large, electronically induced, cohesion of clusters.
Expanded Fluid Alkali Metals in the Partially Ionized Plasma Model
Authors: Redmer R. , Warren W. W. 
Published: July 2007

AbstractThe model of a partially ionized gas is utilized to calculate the equation of state, electrical conductivity, and electronic magnetic susceptibility of expanded metal fluids along the coexistence curve. The effects of screening, self‐energy and cluster formation are found to be essential. The implications on the mechanism of the metal‐nonmetal transition are discussed.
Density Effects on the Ionization Equilibrium and the Transport Properties of a Dense Hydrogen Plasma
Authors: Belmir M. , Bernu B. , Museux J. M. , Wallenborn J. 
Published: July 2007

AbstractIonization of dense hydrogen plasmas is studied from a chemical picture. It is based on a priori existing species: electrons, protons and hydrogen atoms. All particles are treated as classical point particles interacting through pseudo‐potentials which account for quantum diffraction effects. Thermodynamics is evaluated by Monte Carlo simulations in a semi‐grand‐canonical ensemble, a suitable method developed for charged fluids. Density effects on the ionization energy are self consistently introduced in the model. The static equilibrium correlation functions are used as input in kinetic theory for the evaluation of the electrical conductivity. On the other hand, a new collision operator is derived; it is suited to treat collisions between neutral as well as between charged particles.
A New Formula for the Electron‐Electron Correlation
Authors: Stolzmann W. , Blöcker T. 
Published: July 2007

AbstractWe present new Jacobi‐Padé formulae which describe the thermodynamic properties of the electron fluid throughout the full range of degeneracy. These expressions are based on the inclusion of the classical Debye‐Hückel term, the quantum virial series and ground state Monte Carlo results. Comparisons with other investigations are given.
Thermodynamics of Mercury Vapours
Authors: Röpke G. , Nagel S. , Redmer R. 
Published: July 2007

AbstractA quantum statistical approach is used to give a unified treatment of the metal‐nonmetal‐ and liquid‐vapour‐transitions in mercury. The limiting cases of the atomic vapour at low densities and the metallic fluid at high densities are included. A simple plasma model with only long range Coulomb forces has to be improved by considering also short range interactions. Estimates are given for the critical point of the liquid‐gas phase transition, as well as for the Mott density indicating the metal‐nonmetal transition.
Static and Dynamic Properties of Layered Electron Systems
Authors: Kalman G. , Ren Y. , Golden K. I. 
Published: July 2007

AbstractWe analyze the static and dynamic properties of strongly correlated multi‐layer structures. The two extreme configurations, the double‐layer and the infinite superlattice, are studied within a classical model. Static and dynamic instabilities are identified at high enough Γ values and at low enough layer spacings. Interlayer correlations cause the acoustic mode to develop a k = 0 energy gap.
Matter in Strong Magnetic Field: Superfluidity of a Hydrogenlike Gas
Authors: Liberman Michael 
Published: July 2007

AbstractAs is known, so far only helium has appeared to be unique quantum liquid which does not solidify and becomes superfluid at low temperature. The situation is dramatically changed in presence of a strong magnetic field such that the distance between the Landau levels exceeds the Coulomb unit of energy. Under the circumstances, the interaction between hydrogenlike atoms in the triplet ground state is strongly anisotropic and pretty weak. For such a Bose gas of hydrogenlike atoms, there is a possibility of forming a Bose condensate and a superfluid state. The importance of the problem is due to the fact that it arises in various areas of physics, especially in astrophysics and physics of semiconductors. In semiconductors, a high density exciton gas is the unique object for the laboratory studies of the extreme states of matter in a ultrastrong magnetic field, where the “atomic” scale of a magnetic field for the hydrogenlike excitons is of the order of a few Tesla, quite realizable in a laboratory.
Pressure and Compressibility of a Quantum Plasma in a Magnetic Field
Authors: Suttorp L. G. 
Published: July 2007

AbstractThe equilibrium pressure tensor that occurs in the momentum balance equation for a quantum plasma in a magnetic field is shown to be anisotropic. Its relation to the pressure that follows from thermo‐dynamics is elucidated. A general proof of the compressibility rule for a magnetized quantum plasma is presented.
X‐ray Spectroscopic Measurements of 10ns KrF Laser Produced Plasma
Authors: Matsushima Isao , Yashiro Hidehiko , Tomie Toshihisa , Okuda Isao , Matsmoto Yuji , Miura Eisuke , Owadano Yoshiro 
Published: July 2007

AbstractLaser produced plasma generated by 10ns KrF laser pulses has been investigated by means of X‐ray spectroscopic measurements. Electron density and temperature have been obtained with one‐dimensional space resolution. The electron temperature was determined from the slope of free‐bound continuum to He‐like ions. The electron density was estimated from the opacity of resonance line emissions and also from Stark broadening. The observed profiles agree with one‐dimensional hydro‐dynamic simulation result.
On Current Fluctuations in Near‐Earth Space Plasma with Lower‐Hybrid‐Drift Turbulence
Authors: Meister C.‐V. 
Published: July 2007

AbstractElectron and ion current fluctuations caused by lower‐hybrid‐drift turbulence are estimated within nonlinear theory for the plasma of the ionospheric F‐layer, as well as for the plasma mantle and the plasma sheet boundary layer of the tail of the earth's magnetosphere. They are found to be of the order of 10−14 — 10−11 A/m2 and 10−13 — 10−9 A/m2, respectively.
On Modulational Interaction of the Lower‐Hybrid Drift Oscillations
Authors: Popel S. I. , Rumanov I. E. , Tsytovich V. N. 
Published: July 2007

AbstractThe general nonlinear equation of the third order in field strength for the lower‐hybrid drift waves in inhomogeneous plasma is obtained on the basis of kinetic theory. This equation enables us to describe strong turbulence effects (modulational instability, soliton‐like solutions, etc.) as well as weak turbulence effects (decays, scattering). The investigation of the modulational instability of the lower‐hybrid drift waves is carried out. It is demonstrated that the development of the lower‐hybrid drift wave modulational instability is possible only when the wavevector of the modulational perturbations is less or of the order of the wavevector of the pump wave. The condition on the wave vectors, when the nonlinear response defining the character of the modulational instability is determined by the inhomogeneity effects, is obtained.
Modeling of Plasma‐Chemical Reactions in Gas Mixture of CO2Lasers I. Gas Decomposition in Pure CO2Glow Discharge
Authors: Cenian A. , Chernukho A. , Borodin V. , Śliwiński G. 
Published: July 2007

AbstractThe chemistry of a pure CO2glow discharge is modelled as a first step in description of CO2lasers plasma‐chemical reactions. The equilibrium conversion of CO2into CO strongly depends onE/Nratio. It grows from few percent forE/N= 2 × 10−16V cm2to more then 70% forE/N∼ 9 × 10−16V cm2. TheXevalues are only slightly influenced by the change of electron density and temperature. The role of ions and of the CO(a3II) excited electronic state in recombination of CO as well as of heterogeneous recombination is studied. The time required to reach the steady‐state concentrations of chemical species in the system varies from few seconds for highE/Nvalues up to hours in the other end of investigated region; it increases with the fall of discharge current and with the fall ofE/N. Satisfactory agreement with experimental data is achieved.
A Collisional Model of the Positive Ion Collection by a Cylindrical Langmuir Probe
Authors: Tichý M. , Šícha M. , David P. , David T. 
Published: July 2007

AbstractThis article presents a new theoretical model of ion collection by a cylindrical Langmuir probe at medium and higher pressures which we call the “modified Talbot and Chou model”. The model makes use of the following theories; (a) the kinetic theory by Chou, Talbot and Willis [6, 7] and (b) the theory by Zakrzewski and Kopiczynski [10, 11]. The basic idea is to calculate the decrease of probe ion current due to collisions with neutrals according [6, 7] and the increase of the ion current due to destruction of an orbital motion according [10, 11]. The computed results are presented in the form of graphs suitable for probe data interpretation at medium and higher pressures. The applicability of the results at particular plasma conditions is also discussed.
To the Kinetics of Nitrogen Incorporation during dc Magnetron Deposition
Authors: Sobe G. 
Published: July 2007

AbstractInvestigations of nitrogen incorporation during film deposition by dc magnetron sputtering with a CrSiAl target in Ar/N2 mixtures have been carried out in the range of the metallic mode. The rate of the nitrogen consumption is proportional to the nitrogen partial pressure during deposition and to the amperage. The corresponding rate constant decreases with the argon pressure. Furthermore, the condensation rate of the target species decreases with the nitrogen partial pressure and is determined by the rate constant of the nitrogen consumption. The experimental results are explained by a 4‐stepped reaction sequence of nitrogen incorporation consisting in (1) ionization, (2) ion bombardment of the target and formation of a coverage by plating, (3) removal of the coverage by the sputter process, (4) condensation on the substrate.
A 3‐D Fokker‐Planck Code for Studying Parallel Transport in Tokamak Geometry with Arbitrary Collisionalities and Application to Neoclassical Resistivity
Authors: Sauter O. , Harvey R. W. , Hinton F. L. 
Published: July 2007

AbstractA new 3‐D Fokker‐Planck code, CQL‖, which solves the Fokker‐Planck equations with two velocity coordinates and one spatial coordinate parallel to the magnetic field lines B/B, has been developed. This code enables us to model the parallel transport for low, intermediate and high collisional regime. The physical model, the possible relevant applications of the code as well as a first application, the computation of the neoclassical resistivity for various collisionalities and aspect ratios in tokamak geometry are presented.
Potential Formation at Plasma Edge due to Suprathermal Particle Losses
Authors: Yushmanov P. N. 
Published: July 2007

AbstractGeneration of the edge radial electric field and corresponding plasma rotation is studied for both uniform magnetic field and toroidal confinement systems with separatrix configuration of magnetic surfaces. The equations describing the edge plasma rotation due to suprathermal particle losses are derived. The solution on this equations is found for the simplest case of collisionless plasma flow to the neutralizing wall perpendicular to the magnetic field. It is shown that classical acceleration of plasma by ion orbital losses is enough to explain electric field and plasma rotation observed near walls.
Interchange Instability Turbulence Model in Edge Tokamak Plasma
Authors: Benkadda S. , Garbet X. , Verga A. 
Published: July 2007

AbstractInterchange instability is investigated as a plausible mechanism to drive turbulence in the tokamak scrape‐off‐layer. By averaging density and electrostatic potential fluid equations along field lines, a reduced two dimensional model is obtained. Similarly to Rayleigh‐Bénard convection, interchange instability shows a instability threshold and presents localised modes (with a simple geometry and boundary conditions). The nonlinear, turbulent, behaviour of the model is investigated using numerical simulations. Preliminary results show a self‐organization of the flow in coherent structures with a departure from gaussian statistics.
Departures from Sonic Flow at the Sheath on a Divertor Target or Limiter
Authors: Harbour P J , Loarte A 
Published: July 2007

AbstractSonic transitions in a scrape‐off layer (SOL) are discussed, showing the importance of particle and momentum sources, temperature gradients, area change and viscous effects. Supersonic boundary conditions are considered. Sonic transitions are modelled over a wide range of parameters using EDGE1D.
Self‐Consistent Impurity Modeling in a Limiter SOL
Authors: Zanino R. , Ferro C. 
Published: July 2007

AbstractFor a tokamak plasma with a limiter configuration the edge electron density and temperature and the Zeff are self‐consistently calculated. A semi‐analytical model is used which takes into account production of impurities by sputtering and self‐sputtering and their screening in the scrape‐off layer. The computed results show a satisfactory agreement with those measured in the Frascati Tokamak Upgrade.
Review of the Present Status of Consistent Scrape‐off Layer Modeling by Codes
Authors: Ueda N. , Suzuki Y. , Tanaka M. , Itoh K. , Itoh S.‐I. , Tsunematsu T. , Sugihara M. , Takizuka T. , Takamura S. 
Published: July 2007

AbstractA review of the present status of 2‐D fluid codes for the simulation of the boundary plasma in tokamaks has been given in this paper. The major physics issues contained are: (1) plasma and impurity transport model, (2) neutral gas transport model, and (3) atomic/molecular data base. Example results of the simulation of gaseous divertor in ITER (EDA) are also shown to make the discussions clear.
A Moving Finite Element Model of the Tokamak Scrapeoff Layer
Authors: Glasser Alan H. , Kuprat Andrew P. 
Published: July 2007

AbstractMost numerical simulations of the tokamak scrapeoff layer use a mapping to flux coordinates and a piecewise equidistributed grid in those coordinates to resolve multiple length scales and anisotropy. We have developed an alternative numerical method using simple cylindrical coordinates with a complex adaptive grid scheme, based on an unstructured grid of triangles which move adaptively, aligning themselves with the magnetic field and concentrating in regions of sharp gradients.
Regimes with Recombining Plasma in the ITER Divertor
Authors: Krasheninnikov S. I. , Sigmar D. , Soboleva T. K. , Kukushkin A. B. , Batischev O. V. , Sigov Yu. S. 
Published: July 2007

AbstractThe possibility to establish regimes with dense recombining hydrogen plasma in ITER divertor is considered. It is shown that due to the large difference between effective heat transmission coefficients of neutral gas and plasma there is a bifurcation of plasma parameters near the target. Due to this bifurcation a neutral gas layer can occur between the divertor plate and the plasma. The criterion of establishing of this gas layer is found.
Numerical Study on Population Inversion and Lasing Conditions in an Optically Thick Recombining Helium Plasma
Authors: Akatsuka H. , Suzuki M. 
Published: July 2007

AbstractLasing conditions for He I in a cold recombining helium plasma are numerically discussed including optical thicknesses. A collisional radiative model is used to calculate population densities. We discuss the effect of self absorptions by the background residual gas on the lasing conditions quantitatively. The optical thickness is essential in the calculation and affects the population inversions between level pairs of the singlet state drastically, while those of the triplet state are not affected very much. In the optically thin plasma, the laser lower levels of the singlet state depopulate mainly through radiative transitions. On the other hand, they depopulate mainly through electron collisional deexcitations in the optically thick plasma. Results of the calculations are verified by the spectroscopic observations of an arc‐heated magnetically trapped expanding plasma jet generator which we developed. The requirement for the background pressure in which the lasing is possible is discussed quantitatively.
Temperature Distributions Across the Plasma Layer of Planar Low Pressure Microwave Plasmas — A Comparative Investigation by Optical Emission Spectroscopy
Authors: Röpcke J. , Ohl A. 
Published: July 2007

AbstractNowadays low temperature non‐equilibrium plasmas received considerable attention in very different fields of plasma processing.The subject of the present paper is the comparative measurement of neutral gas temperature and optical excitation temperature to analyze the temperature distributions across the plasma layer of H2 non‐equilibrium plasmas (p = 0.2 – 1.5 kPa) with small admixtures of hydrocarbons in a novel planar microwave plasma source (2.45 GHz) used for plasmachemical deposition purposes by means of optical emission spectroscopy. Typical microwave power flux densities into the plasma lie within a range of 2 W cm−2 to 20 W cm−2. Results of neutral gas temperature measurements derived from Hα line Doppler profiles are compared with rotational temperatures of H2 and N2 molecules. The neutral gas temperature (800–1700 K) corresponds to the rotational temperature of the H2 molecules (Fulcher band, R 0–0 branch) but shows a more distinct spatial gradient. The rotational temperature of admixtured N2 molecules (2000–3000 K) is much more higher although Boltzmann distribution was ensured. The spatially resolved measured excitation temperature (1–3 eV) determined with the help of line intensity ratios of admixtured Ar well agrees with Langmuir probe measurements.The reported measurements as a whole demonstrate the feasibility of comparative investigations of different optically determined temperatures for expressive characterization of low pressure microwave plasmas.