bluuebunny/crossref_metadata_2025 huggingface dataset:
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

A 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

An 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 The adiabatic sonic speed has been replaced by the isothermal one due to the thermal conductivity.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

Nonlinear 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

The 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.
Free Energy and Ionization in Dense Plasmas of the Light Elements
Authors: Ebeling W.
Published: July 2007

Padé approximations for the free energy of plasmas are given which take into account multiple ionization effects. The free energy landscape over the degrees of ionization is discussed. On the example of helium plasmas the possibility of two minima, i. e. two stable ionization states is shown.
Saha Equation, Single and Two Particle States
Authors: Kraeft W. D. , Strege B. , Girardeau M. D.
Published: July 2007

Single 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

We 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

Unimolecular 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

Using 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

By 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

A 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

A 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

In 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.
New Mathematical Model of Physico‐Chemical Dynamics
Authors: Gontar V. G. , Ilin A. V.
Published: July 2007

The work advances a discrete mathematical model of physico‐chemical reactions. Possibilities of the described model application for calculation of physico‐chemical systems with complicated behaviour are analyzed.
Two‐dimensional Numerical Simulation of the Beam‐Plasma‐Discharge
Authors: Kruscha K. J. G. , Popkov N. G.
Published: July 2007

A 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

The 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

On 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

The 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

Experiments 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

The 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

The 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

The 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

The 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].
The Numerical Differentiation of Probe Characteristic
Authors: Trunec D.
Published: July 2007

In the paper new methods of the computation of second‐order derivative of probe characteristic are proposed. All methods are tested on testing data as well as on experimental measured probe characteristic.
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

A 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.
Electron Energy Distribution Function at Potential Drop between two Negative Ar Glow Discharges
Authors: Ohe K. , Imaeda K.
Published: July 2007

The 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

The 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

Plasma 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

In 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

The 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

This 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

It 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

We 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

The 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

Ionization 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

We 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.
Equation of state for weakly nonideal plasmas
Authors: Schlanges M. , Kraeft W. D. , Dewitt H.
Published: July 2007

Using a Green's function approach a low density equation of state is derived for quantum plasmas up to the order (e2n)5/2.
Thermodynamics of Mercury Vapours
Authors: Röpke G. , Nagel S. , Redmer R.
Published: July 2007

A 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

We 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

As 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.
Collective Modes of Magnetized Quantum Plasmas
Authors: John P.
Published: July 2007

We establish expressions for the collective modes in an one‐component plasma in a magnetic field. Using the results of the modes we determine the long‐time behaviour of the time correlation functions for the charge density, current density and the energy density.
Pressure and Compressibility of a Quantum Plasma in a Magnetic Field
Authors: Suttorp L. G.
Published: July 2007

The 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

Laser 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

Electron 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

The 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

The 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

This 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

Investigations 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

A 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

Generation 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

Interchange 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

Sonic 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

For 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

A 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.
Models and Numerics in the Multi‐Fluid 2‐D Edge Plasma Code EDGE2D/U
Authors: Simonini R , Corrigan G , Radford G , Spence J , Taroni A
Published: July 2007

The JET edge plasma code EDGE2D/U is designed to simulate divertor configurations. We describe here the physical model and the numerical techniques used.
A Moving Finite Element Model of the Tokamak Scrapeoff Layer
Authors: Glasser Alan H. , Kuprat Andrew P.
Published: July 2007

Most 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

The 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

Lasing 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

Nowadays 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.
CO2Laser Discharge Influenced by a Rotating Magnetic Field
Authors: Ose E. , Triebel W. , Schumann A.
Published: July 2007

This paper deals with experimental investigations of the effect of a rotating magnetic field on a diffusion cooled CO2laser discharge. Some properties relevant to laser activity are discussed, e.g. neutral gas temperature, magnetically driven gas rotation, pumping rate, and distribution of small signal gain within the discharge tube. By means of an intracavity method the radial distribution and the time behavior of the laser output power were measured.
On the Relaxation of the Energy Distribution Function of Light Particles in Heavy Gases
Authors: Braglia M. , Minari P.
Published: July 2007

A stochastic approach to the thermalization problem of light particles in heavy gases is discussed which presents a number of advantages with respect to more conventional techniques. The procedure is used to study the relaxation of the distribution function in cold gases in two situations in which: i) only first order terms are retained and ii) second order terms are also included, with respect to the ratio m/M between light‐particle mass m and atomic mass M.
Modon Saturation in Collisional Driftwave Turbulence
Authors: Naulin V. , Spatschek K. H.
Published: July 2007

The nonlinear evolution of a collisional driftwave instability is considered. Based on the two‐fluid description with ion viscosity and electric resistivity effects, first two coupled equations are derived. Iterating the latter for nearly adiabatic behaviour and a two‐dimensional geometry, a one‐field description is found which properly takes into account the damping of structures. As demonstrated by numerical simulations, this solves an old problem of collisional driftwave turbulence, since in contrast to previous considerations the unlimited growth of self‐organized structures is stopped.
Ion Acoustic Solitons in Impurity‐Containing Plasmas
Authors: Popel S. I. , Yu M. Y.
Published: July 2007

Localized nonlinear ion acoustic waves are investigated for plasmas containing impurity ions or negatively charged dust particles. It is found that dark as well as the usual bright ion acoustic solitions can exist.
Study of the Nitrogen Arc under Reduced Pressure
Authors: Kaminska A.
Published: July 2007

The paper presents a model of arc in a d.c. vortex plasma torch which allows to determine distributions of temperature and plasma electron density in conditions of reduced pressure. The model makes it possible to elucidate voltage‐current characteristics of the arc at different pressures and its dynamic behaviour connected with the phenomenon of the electric arc root displacement. The experimental research also determined voltage‐current characteristics for different flow rates and pressures. The fluctuations of the arc current and the arc voltage were measured. The corresponding wave shapes were analysed by Fast Fourier Transform. The frequency variations with flow rate, arc current and pressure were studied and discussed.
Alfvén Pulses in the Ionospheric Waveguide
Authors: Shvartsburg A. B. , Stenflo L.
Published: July 2007

Exact explicit solutions, describing the propagation of wideband non‐sinusoidal waveforms in the ionospheric Alfvén waveguide by means of non‐separable electromagnetic fields, are presented. The dispersive modulation of these fields is shown to result in the formation of quasimonochromatic oscillations at the wings of the Alfvén pulses. The frequencies of these oscillations are close to the cut off frequencies of the waveguide.
Radiative Thermal Instability and Bifurcation
Authors: Bachmann P. , Sünder D.
Published: July 2007

A radial hydrodynamic model is used to investigate the radiative thermal instability in the scrape‐off layer by applying a linear stability analysis of existing equilibrium states. Phase space trajectories are analyzed to derive conditions of their existence and bifurcation. Equilibrium profiles are calculated for the cases of homogeneous plasma temperature, plasma density and self‐consistency. Unstable perturbations, localized in the scrape‐off layer, may lead to a strongly radiating detached plasma belt.
Plasma‐Maser Instability of Bernstein Mode in Presence of Magnetohydrodynamic Turbulence
Authors: Saikia B. J. , Deka P. N. , Bujarbarua S.
Published: July 2007

A theoretical study is made on the amplification mechanism of electrostatic Bernstein mode wave in presence of kinetic Alfven wave turbulence in a magnetized plasma on the basis of plasma‐maser interaction. It is shown that a test high frequency electrostativ Bernstein mode wave is unstable in the presence of low frequency kinetic Alfven wave turbulence. The growth rate of the Bernstein wave vanishes only in an unmagnetized plasma. Because of the universal existence of the kinetic Alfven waves in large scale plasmas, the results have potential importance in space and astrophysical radiation processes.
Modeling of Plasma‐Chemical Reactions in Gas Mixture of CO2 lasers. II. Theoretical Model and its Verification
Authors: Cenian A. , Chernukho A. , Borodin V.
Published: July 2007

In the paper we have modelled plasma‐chemical reactions in the CO2 low pressure, DC excited lasers. A good agreement of theoretical and experimental results has been achieved. It has been proved that neglect of reactions with electronic excited species or heterogeneous recombination leads to almost 50% overestimation of CO2 equilibrium conversion. The relation of CO2 equilibrium conversion to the reduced field E/N, pressure and current density depends on discharge conditions and mainly on the role played in discharge by ambipolar diffusion. This role decreases with an increase of the discharge diameter and of the mixture convection velocity. The CO2 equilibrium conversion increases with growth of E/N and j and with decrease of pressure for discharges in small, sealed‐off laser systems. The CO2 equilibrium conversion is not always a monotone function of p in large, convection cooled lasers. It does not depend so much on E/N as the electron temperature alone if conversions in different mixtures are compared.