bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic Study of the Emission of the First Negative System in an Argon‐Nitrogen Plasma at Atmospheric Pressure
Authors: Callède G. , Deschamps J. , Godart J. L. 
Published: July 2007

AbstractQuantitative optical spectroscopy measurements of the emission spectra of the N(B2∑u,)ν′→X2∑gν″ transition (first negative system) in an Ar‐N2microwave discharge at atmospheric pressure have allowed determination of the rate coefficient of the production of Nmolecules in theB2∑u, state with vibrational level ν′ = 0.The N(B2∑u, ν′) molecules are produced by the reactionmagnified imagein a surface‐wave‐induced microwave discharge (2450 MHz) sustained in an open‐ended dielectric tube. The rate coefficientK(T) has been obtained for ν′ν″ = 0 for different gas temperatures by varying the incident microwave power. TheK00(T) values are between 7.10−10and 4.10−10cm3s−1for the temperature range 2500 to 3450K.
Effect of Electron Velocity Distribution on the Heating of Core by Corona in a Spherical Pellet
Authors: Singh D. P. , Bredice F. , Giammanco F. , Vaselli M. 
Published: July 2007

AbstractWhen a spherical plasma pellet is irradiated symmetrically from all sides by high power laser beams, hot electrons are produced at the plasma resonance layer. They move in the inward radial direction causing a counter‐streaming cold electron current flowing outwardly to maintain the charge neutrality. In general, the interaction between the hot electrons and the counter‐streaming cold background electrons leads to broadening of the velocity distribution of the latter. For a given heat flux, the electron velocity distribution constrained by the requirements for not supporting beam plasma instabilities, predicts a minimum electron velocity in the plasma ablation zone. These considerations affect the efficiency of heat transfer from the hot corona to the cold core. The purpose of this paper is to study the dependence of core‐corona coupling on the electron velocity distribution, laser wavelength and other plasma parameters in detail.
Numerical Modelling of Impurity Retention in the ITER Tokamak Scrape‐off Layer Plasma
Authors: Zagórski R. 
Published: July 2007

AbstractThe hydrogen plasma and carbon ions flows generated at the target plates in the ITER tokamak scrape‐off layer are numerically investigated. A 2D model of hydrogen plasma and impurity ions is presented. The model is based on the electron‐ion Braginski fluid equations [1] for hydrogen plasma and rate equations for impurities. Arbitrary level of impurity ions concentration is assumed. Recycling of hydrogen, sputtering and self sputtering of carbon atoms at the target plates are taken into account. Equations of the model are solved in the slab geometry using 2D‐multifluid numerical code EPIT [2]. Problems of impurity ions retention and radiation in the divertor volume are analyzed. Results of calculations for ITER tokamak boundary plasma are presented, showing that poor retention is likely at high impurity concentration in the divertor volume. The radiation power can be a significant part of ingoing energy.
Investigation of an Enhanced Glow Structure in a Low‐Pressure rf Discharge in Helium
Authors: Flohr R. , Schirmer H. , Piel A. 
Published: July 2007

AbstractSpatially resolved plasma induced emission spectroscopy (PIE) is applied to a symmetric parallel plate discharge in helium under rf excitation at 13.56 MHz. The optical emission features are studied in the pressure range of 10–360 Pa and power densities from 6 mW/cm3 to 90 mW/cm3. At pressures above 60 Pa and power densities exceeding 50 mW/cm3 the transition from the α‐ to the γ‐mode is observed, which, in helium, is accompanied by the formation of a disk‐shaped brightly luminous glow. A marked difference between the emission from levels of the triplet and singlet system of the helium atom occurs above this threshold of applied power. The spatial emission distribution of equivalent lines of the helium atom is rather different under pressure variation. Therefore the spatial distribution of the metastable levels is concluded to be substantially different between singlets and triplets. This effect is attributed to a rapid decrease of electron temperature and increase of electron density which is a characteristic of the transition between the two heating modes. Low temperature and high density of the electrons favour an overproportional growth of the associated 2 1S destruction rate, i.e., singlet to triplet conversion. A similar effect has been reported for a dc discharge by Lawler et al. [1].
A New Method for the Development of a Nonlinear Equivalent Circuit for a Gas Discharge
Authors: Unger H. , Weltmann K.‐D. , Deutsch H. , Wesch J. , Wilke C. 
Published: July 2007

AbstractThe behaviour of gas discharges can be modelled by equivalent circuits built on the basis of a theoretical description of the plasma. This paper introduces a method to develop a nonlinear equivalent circuit directly by means of the balance equations of the column plasma and by the help of the knowledge obtained from the design of the linear equivalent circuit. The linear network theory was used for the derivation. The circuit found in this way is similar to a derived linear equivalent circuit of the column plasma with two inertial factors (delayed effects) for a neon gas discharge described in previous papers.
Theory of Jovian Kilometric Radiation
Authors: Goswami K. S. , Saikia B. K. , Bujarbarua S. , Nambu M. 
Published: July 2007

AbstractThis report presents a theoretical model of extraordinary mode radiation in presence of low frequency whistler mode. We show that the generation mechanism of extraordinary mode emission in the presence of whistler mode is based on the plasma maser theory. Application of theoretical results to Jovian Kilometric radiation is examined.
The Use of Corona Discharge for Rubber Crush Drier Exhaust Control
Authors: Morvová M. , Morva I. , Kurdel M. 
Published: July 2007

AbstractThe rubber crush drier exhaust contains mainly styrene, ethylbenzene, cumene, diizopropylbenzene, alkylphenols, monocyclic terpenes and technological additives as stearic acid, oils an colophony. For possible application of d.c. corona discharge to control styrene in exhaust, the reaction of styrene with additives and air in various d.c. corona discharge tubes was studied. The change of styrene content in the gas phase was measured by IR absorption spectrometry. The decrease of styrene concentration was minimum 83% and reached the 98,9% efficiency. No aromatic compounds remain after corona discharge action in gas phase. The structure of solid products was specified with reflection IR absorption spectrometry and compared with a calibration polystyrene foil (300 μm). The main product has been of malein anhydride‐styrene copolymer character for a negative corona discharge and of phenol or quinone‐styrene copolymer character for a positive corona discharge.
On the Structure of Atoms in Strong Magnetic Fields
Authors: Lief E. P. , Weisheit J. C. 
Published: July 2007

AbstractThe problem of a multi‐electron atom in a strong magnetic field is treated within the framework of a new statistical model. Here, the charge density n is required to have axial symmmetry. The partial factorization ansatz, n(ϱ, z) = nϱ(ϱ) · nz(ϱ;z), when introduced into Kadomtsev's equation, leads to a second‐order, non‐linear partial differential equation for nz that is valid over an important range of field strengths. Analytical solutions for two limiting approximations are consistent with earlier qualitative studies. Some illustrative, numerical solutions for a less restrictive approximation reveal atomic structures analogous to accurate hydrogenic results, already in the literature.
Model for Ion Collision Rate and Kinetic Equation
Authors: Dufty James W. 
Published: July 2007

AbstractA model for the collision rate of an impurity ion in a plasma is formulated by extending a corresponding model for velocity and electric field correlation functions. All dynamical effects of the plasma are represented by its electric field at the impurity, which is then given a simple stochastic description. The simplest example allows complete determination of the collision rate and solution to the associated kinetic equation.
Dynamic screening effects on the shift and the shape of spectral lines
Authors: Günter Sibylle 
Published: July 2007

AbstractA many particle theory has been applied to investigate collective effects on the shift and the shape of spectral lines. It is shown that the line shift becomes nonlinear with respect to the electron density if the energy distance of the radiators levels is in the order of magnitude of the electron plasma frequency. For weakly non thermal plasmas dips on the line profile occur near the electron plasma frequency.
Influence of the Plasma Kinetics on the Si/C Ratio of a‐SixC1‐x: H Thin Films Deposited by Reactive Magnetron Sputtering of a Si Target in Ar + CH4 Gas Mixtures
Authors: Statev Sv. , Ivanov I. , Petrov I. , Carlsson J. , Orlinov V. 
Published: July 2007

AbstractPossible sources of silicon and carbon atoms built‐in amorphous hydrogenated silicon carbide thin films grown by reactive magnetron sputtering (RMS) in argon/methane gas mixtures are evaluated. It is found out that the plasma decomposition of methane molecules plays an essential role in providing of growing film surface by active hydrocarbon fragments, thus influencing significantly the film stoichiometry even though the methane partial pressure in the sputtering gas mixture is only 1.5–4.7%.
An Assessment of the Role of Atomic Processes for Dispersing the Power in a Divertor
Authors: Post D. , Hulse R. , Stotler D. 
Published: July 2007

AbstractThe present concepts for power and particle control in the next generation of tokamak experiments rely upon atomic processes to transfer the power and momentum from the divertor plasma to the divertor chamber walls. These concepts are being evaluated with sophisticated one‐ and two‐dimensional divertor models. We present a survey of some of the candidate atomic processes of impurity radiation, hydrogen radiation and atomic physics and molecular effects to aid the development of the models.
The Effect of Flow Reversal on Impurity Behaviour in Tokamaks
Authors: Stangeby P. C. , Elder J. D. , Reiter D. , Maddison G. P. 
Published: July 2007

AbstractResults are reported for a study of impurity edge transport and core contamination in the presence of flow reversal of the DT plasma, using 2‐D plasma solutions for the ITER CDA configuration produced by the B2 fluid code, coupled to the EIRENE Monte Carlo neutral hydrogenic code and the DIVIMP Monte Carlo impurity neutral/ion code. The effect of different types of impurity source is considered, including (a) target sputtering, (b) wall sputtering, artificial injection (for radiative cooling), and core helium production.
2‐D Fluid Transport Simulations of Gaseous/Radiative Divertors
Authors: Rognlien T. D. , Brown P. N. , Campbell R. B. , Kaiser T. B. , Knoll D. A. , McHugh P. R. , Porter G. D. , Rensink M. E. , Smith G. R. 
Published: July 2007

AbstractThe features of the fully implicit 2‐D fluid code UEDGE are described. The utility of the code is demonstrated by showing bifurcations or multiple solutions of the tokamak edge plasma for both deuterium and impurity injection in the divertor.
Neutral Gas Transport Modeling with DEGAS 2
Authors: Stotler Daren , Karney Charles 
Published: July 2007

AbstractWe are currently rewriting the neutral gas transport code, DEGAS [1, 2], with a view to not only making it faster, but also easing the process of including new physics. The goal is to make adding new species and reactions relatively simple so that the code can be rapidly adapted to new divertor physics regimes. DEGAS 2 will also be optimized for coupling to fluid plasma codes, incorporating many of the techniques utilized in B2‐EIRENE[3–5]. Finally, it is our intention that DEGAS 2, like DEGAS, be well‐documented and easy to use. We will present model calculations including ionization and charge exchange which will illustrate the way reactions are included into DEGAS 2 and will demonstrate operation of the code.
Power Exhaust in ITER
Authors:   ITER Joint Central Team
Published: July 2007

AbstractThe main features and engineering parameters of the ITER EDA design are described and the operating parameter space is surveyed. A key element in the design is the divertor which must exhaust the bulk of the power generated by α‐particles. At the fusion power levels envisioned, Pf⩾1500 MW, conventional divertors of the type developed in the CDA are unable to accommodate the resultant heat levels. The novel design being developed to address the power exhaust for ITER is described, as are the underlying physics concepts. Model calculations performed in support of the concept and the results of experiments aimed at establishing an empirical basis for its operation are reviewed.
Influence of Kinetic Effects on Particle and Energy Flows in the ITER Divertor
Authors: Batischev O. V. , Krasheninnikov S. I. , Sigmar D. J. , Sigov Yu. S. , Soboleva T. K. 
Published: July 2007

AbstractA kinetic modelling of 1d collisional and 2d Vlasov magnetic SOL's using the W1 and W2 particle codes is presented. Deviation of the distribution function from the equilibrium one is shown, as well as the possibility of kinetic instability in diverted plasmas.
Numerical Simulation of Carbon Impurities In JT‐60U Experiment
Authors: Tanaka M. , Ueda N. , Suzuki Y. , Tsuji S. , Takizuka T. , Itoh S.‐I. , Itoh K. 
Published: July 2007

AbstractNumerical simulation of the behavior of carbon impurity for the JT‐60U divertor experiment has been carried out. Two approaches are examined for the impurity model: (1) a full charge state model and (2) a single average ion model. The full model simulates fairly well the power loss due to the impurities. The amount of power loss obtained by the single average ion model disagrees with that of the full model.
Investigations on Plasma Assisted Surface Cleaning of Aluminum in an Oxygen Glow Discharge
Authors: Kersten H. , Behnke J. F. , Eggs C. 
Published: July 2007

AbstractAluminum plates which are contaminated with hydrocarbon containing compounds (oil, grease) were treated in an Ar‐, O2‐ and Ar/O2‐plasma generated by a dc‐discharge. Besides a variation of the macroscopic discharge parameters (power, pressure) also different modes (anomalous glow regime, hollow cathode regime) have been studied. In most cases the contaminated substrates served as cathodes of an anomalous glow discharge where the combined influence of chemically reactive radicals and energetic ions was very effective.During the plasma process the discharge was monitored by means of power variation and optical emission spectroscopy. The spectral line intensities of several species (etchants and products) have been measured as functions of the process duration. Simultaneously the removal of the contamination layers was observed by means of in‐situ ellipsometry. The temporal change of the ellipsometric parameters ψ and δ during the cleaning process was taken as a measure for the state of the surface. The combination of spectroscopic and ellipsometric measurements which indicate the progress of the plasma treatment gave interesting results on the mechanisms at the surface. In addition, surface analysis was used to assess the quality of the substrates treated.
Coaxial Discharge and Transverse Magnetic Field
Authors: Soliman H. M. , El‐Kashaf G. M. , Masoud M. M. 
Published: July 2007

AbstractThe study deals with the effect of an applied transverse magnetic field on the dynamics and parameters of the focused and expanded plasma in a coaxial discharge. The experimental results were found with a 3 kJ Plasma focus device of a Mather geometry. The discharge takes place in hydrogen gas with base pressure of 0.5 Torr. The experiments are conducted with a 10 kV bank voltage, which corresponds to 100 kA peak discharge current with rise time 8 μs. Helmholtz magnetic coils are placed outside the expansions chamber to produce a transverse magnetic field with intensity 280 G perpendicular to the plasma expanded from the coaxial electrodes. The investigations have shown that the plasma flow along the expansion chamber axis is restricted when applying the externally transverse magnetic field and the maximum axial velocity of the expanded plasma is decreased by 33%. X‐ray probe has been used to measure the focused plasma electron temperature (Te). The experimental results and the calculations showed that Te is decreased from 2.2 keV to 800 eV with the application of a transverse magnetic field. The expanded plasma electron temperature and density have been measured by an electric double probe, the results cleared that the expanded plasma electron temperature is decreased by 2.6 times while its density is increased by 9 times, when a transverse magnetic field is applied.
Kinetic Description of Elastic Processes in Hydrogen‐Helium Plasmas
Authors: Bachmann P. , Reiter D. 
Published: July 2007

AbstractRecent experiments with high density divertor plasma operation in tokamaks and future tokamak design projects have revived interest in the much earlier work on elastic collision processes between neutral and charged components in hot plasmas. In revisiting these papers, we employ classical methods to calculate deflection functions, cross sections and collision rates for the most important of such elastic collision processes. A phyiscally motivated cut‐off procedure for the model interaction potential function is introduced. An algorithm for implementation of such processes into kinetic Monte Carlo neutral gas transport models is described, which accurately accounts also for possible singularities in the deflection function. Data fits for the relevant quantities are provided for hydrogenic and helium species. The relevance of elastic neutral‐ion collisions is illustrated by a numerical simulation of an ITER relevant divertor model.
Plasma Phase Transition in Fluid Hydrogen‐Helium Mixtures
Authors: Schlanges M. , Bonitz M. , Tschttschjan A. 
Published: July 2007

AbstractThe composition and the equation of state for a binary mixture of dense partially ionized hydrogen and helium are investigated on the basis of quantum statistical theory. Theoretical evidence for the existence of a hydrogen‐like and helium‐like plasma phase transition is found. Critical data for the phase transitions are given for the whole range of the mixing parameter.
Nonstationary and Quasi‐stationary Treatment of Distribution Anisotropy in the Temporal Relaxation of an Energetic Electron Group
Authors: Winkler R. , Braglia G. L. , Wilhelm J. 
Published: July 2007

AbstractA relaxation study of an electron group in collision dominated weakly ionized plasmas has been performed. The study is based on the two‐term approximation of the Legendre polynomial expansion of the electron velocity distribution in the nonstationary Boltzmann equation. To overcome the limitation of the conventional quasi‐stationary treatment of the distribution anisotropy, a very efficient solution approach of the nonstationary kinetic equation in two‐term approximation has been developed which allows for a strict nonstationary treatment of the distribution anisotropy. By using this approach the temporal evolution of the isotropic and anisotropic distribution of the electrons has been investigated for a model plasma, which involves typical features of an inert gas plasma. A comparison of the results with corresponding ones obtained by applying the conventional approach under various parameter conditions clearly indicates a pronounced falsification of the real relaxation course by the latter approach.
A Barrier Discharge Reactor with Ferroelectric Electrodes I. Influence of thickness and surface area of electrodes
Authors: Opalińska T. , Szymański A. 
Published: July 2007

AbstractA study aimed at finding a way of scaling‐up a small laboratory reactor employing an electric discharge with a dielectric barrier was carried out. The dielectric used was ferroelectric ceramic material of a high permittivity (ϵ above 1000) comparing to glass (ϵ ≈︁ 3–10), which is generally used. The main component of the ceramics was BaTiO3. The advantage of using this type of ceramics is related to a considerable increase in power density without the need of increasing voltage which supplies the system.The influence of the thickness and surface of ferroelectric electrodes on the macroscopic characteristics of the discharge and efficiency of chemical process was investigated. Ozone synthesis from oxygen was the reaction under consideration.A new structure of the reactor was proposed comprising a series of parallelly spaced thin ceramic plates. High electric permittivity of the ferroelectric ceramics enables such „sandwich”︁ structure to be supplied by only two edge ceramic electrodes.
Self‐Consistent Model of a Positive Column in an Inert Gas Discharge at Low Pressures and Small Currents
Authors: Behnke J. , Golubovsky Yu. B. , Nisimov S. U. , Porokhova I. A. 
Published: July 2007

AbstractA formalism of the self‐consistent solution of the kinetic equation and the field equation is described for the positive plasma column in an inert gas discharge. The model considers the presence of electrons trapped in the potential well transfering the discharge current and of free electrons which reach the walls in a free diffusion regime supporting the required ionization level in the discharge. The calculations have been carried out for neon. In the model application range the comparison is made with experimental data of axial fields, wall potentials, wall currents and in some cases with distribution functions. A good correspondence takes place.
New Developments in Plasma Edge Modeling with Particular Emphasis on Drift Flows and Electric Fields
Authors: Baelmans M. , Reiter D. , Weynants R. R. 
Published: July 2007

AbstractThis paper reviews the present status of 2‐dimensional plasma edge codes with respect to simulation of electric fields and drift flows. Starting from experimental results and based on available simple analytic theories, different features of important mechanisms in the edge of a tokamak plasma are discussed and their availability in advanced numerical codes is established.
Self‐consistent Core‐Edge Nonlinear Transport Simulations with CORSICA 2
Authors: Tarditi A. , Cohen R. H. , Craddock G. G. , Crotinger J. A. , Porter G. D. , Rognlien T. D. , Shestakov A. I. , Smith G. R. 
Published: July 2007

AbstractThe coupled core‐edge nonlinear transport code CORSICA 2 is introduced and the structure of its iterative coupling algorithm is briefly discussed. Selected application results are reported that reproduce equilibria in DIII‐D discharges with plasma profiles initialized from the experimental data. Simulations for an L‐H transition and for a gas puffing experiment in DIII‐D plasmas are presented.
Simulation of the Alcator C‐Mod Divertor with an Improved Neutral Fluid Model
Authors: Wising F. , Knoll D. A. , Krasheninnikov S. I. , Rognlien T. D. , Sigmar D. J. 
Published: July 2007

AbstractWe have simulated detachment in Alcator C‐Mod, using an improved neutral fluid model. It features a parallel neutral momentum equation, fully coupled to the ions, allowing parallel plasma momentum to be converted into neutral momentum, which is dispersed to the material walls due to the high neutral viscosity. The simulations reproduce the pervasive experimental feature that the plasma detaches gradually, starting at the strike point, while always remaining attached above the nose of the divertor channel. The strike point heat flux and current drop by an order of magnitude as 0.5% of carbon is introduced to induce partial detachment. The plate temperature remains at or above about 1 eV all the way out to the divertor nose, in agreement with the experimental data.