bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ion‐ion Correlations in Dense Plasma Derived from a Quasimolecular Thomas‐Fermi Model
Authors: Frey H.‐D. , Meyer‐ter‐Vehn J. 
Published: July 2007

AbstractIon‐ion correlation functions of shock‐compressed, strongly coupled aluminum plasma with 1–5 times solid density and 1–20 eV temperature are calculated by using a quasimolecular Thomas‐Fermi model to determine the interaction potential between ions and by solving the Ornstein‐Zernike equation together with the Percus‐Yevick and, alternatively, the hypernetted chain aproximation. The results are checked by Monte‐Carlo simulations and are compared with other independent calculations taken from the literature.
Dissociation and Thermodynamics in Dense Hydrogen Fluid
Authors: Bunker A. , Nagel S. , Redmer R. , Röpke G. 
Published: July 2007

AbstractThe behavior of matter at high pressures is studied for a better understanding of planetary interiors and the structure and evolution of stars, or for inertial confinement fusion. Especially, the phase diagram of hydrogen and helium as the most abundant elements in the universe has been studied both theoretically and experimentally up to ultra‐high pressures in the Mbar region where metallization is expected to occur. While static high‐pressure experiments in diamond anvil cells give no evidence for metallic conduction in solid hydrogen up to 250 GPa, recent dynamic shock‐wave experiments in fluid hydrogen have demonstrated metallization for the first time at 140 GPa and 3000 K. The equation of state, possible phase transitions, and the structural properties of fluid hydrogen at ultra‐high pressures as well as of hydrogen plasma at elevated temperatures are of special interest. We use here analytical calculations and Monte Carlo simulations to determine the pair distribution functions in partly dissociated hydrogen. The equation of state and the degree of dissociation are calculated. The gradual transition from molecular to atomic hydrogen occurs due to pressure dissociation. Furthermore, we show the influence of dissociation on the proton‐proton pair distribution function.
The Interplay of Electron‐Phonon and Electron‐Electron Scattering within the Two‐Time Green's Function Description
Authors: Köhler H. S. , Binder R. 
Published: July 2007

AbstractWe present numerical results for electron‐phonon and electron‐electron scattering in optically excited electron plasmas in bulk semiconductors. Our results are based on the full two‐time Green's function approach. They include quantum mechanical memory and correlation effects because the scattering integrals are generalizations of the conventional Boltzmann scattering integrals. The interplay of two different scattering mechanisms is studied and compared to results where only one scattering mechanism is present.
Lenard—Balescu—type Kinetic Equation for Composite Particles in Dense Quantum Plasmas
Authors: Schlanges M. , Bornath Th. 
Published: July 2007

AbstractA kinetic equation for the distribution function of two—particle bound states in dense quantum plasmas is derived in the framework of the real—time Green's function technique. Using a generalized V5‐approximation Lenard—Balescu—type collision integrals are derived taking into account elastic, inelastic and reactive three—particle processes with dynamically screened interaction. An extended random phase approximation is discussed for the polarization function.
To the Theory of Colloidal Plasmas
Authors: Schram P. P. J. M. , Trigger S. A. 
Published: July 2007

AbstractThe problem of the microscopic effective pair interaction is discussed for two‐ and many‐macroion colloidal plasmas. For a crystallized state of colloids with charged particles the melting curve and the minimal charge for crystallization is considered analytically for a DLVO‐type of effective potential. The damping of longitudinal waves is investigated for infinite and finite sizes of colloidal crystals.
Debye Length in a Neutral‐beam‐heated Plasma
Authors: Wolle B. 
Published: July 2007

AbstractThe scale length for an effective shielding of a charged particle in a plasma is the Debye length, which is for Maxwellian velocity distributions determined by the ratio of the temperature to the density. However, fusion plasmas heated by neutral‐beam injection (NBI) exhibit highly non‐Maxwellian slowing‐down velocity distributions. In this case, the evaluation of the characteristic shielding distance from these velocity distributions requires the solution of Fokker‐Planck‐Poisson equations. In this paper, the effect of NBI slowing‐down velocity distributions on the shielding distance are discussed. Analytic expressions for the Debye length of a neutral‐beam‐heated plasma are given. The results are compared to the Maxwellian case.
Modelling Efforts on the Helical Near Field Divertor of the Dynamic Ergodic Divertor (DED) for TEXTOR‐94
Authors: Eich Th. , Finken K. H. , Kaleck A. 
Published: July 2007

AbstractAs a first step for the modelling of the plasma‐wall interaction of the proposed Dynamic Ergodic Divertor (DED) of TEXTOR‐94, the topology of the magnetic field lines of the divertor is analysed. Despite the strong ergodization, the magnetic field lines intersecting the wall in one poloidal turn form continuous sets. These sets are visualised by a 2‐D imaging technique; the field lines of each set of starting values is traced one poloidal turn clockwise and ctr. clockwise, marking those lines intersecting the wall. An overlay of the marked starting points defines areas with properties of a scrape‐off layer and areas with field lines ending on one side in the ergodic layer and one side on the wall. The edge plasma can be described by a 2‐D model; the model treats a part of the plasma as that of a conventional scrape‐off layer and another part with “half open” field lines connecting the divertor target plate with the ergodic layer. Calculations of the power flux distribution in the DED‐near field divertor are presented.
Scrape‐Off Layer Turbulence Theory and Simulations
Authors: Xu X. Q. , Cohen R. H. 
Published: July 2007

AbstractSignificant investigations in the area of scrape‐off layer (SOL) turbulence theory and simulations are reviewed. The paper begins with description and derivation of the various models investigating specific linear modes as well as a discussion of the regions of validity. Special attention is given to various low‐frequency electromagnetic drift‐types modes in an x‐point divertor geometry, which are generally believed to be relevant under normal operating conditions for current and future large fusion devices. The anomalous transport from simulations and from mixing length estimates are discussed and compared with results infered from experiments. Studies of mechanisms for the L‐H transition due to turbulent transport in the SOL, and its impact on the H‐mode power threshold, are also surveyed.
Comparisons of physical and chemical sputtering in high density divertor plasmas with the Monte Carlo Impurity (MCI) transport model
Authors: Evans T. E. , Finkenthal D. F. , Loh Y. S. , Fenstermacher M. E. , Porter G. D. , West W. P. 
Published: July 2007

AbstractThe MCI transport model was used to compare chemical and physical sputtering for a DIII‐D divertor plasma near detachment. With physical sputtering alone the integrated carbon influx was 8.4 × 1019 neutrals/s while physical plus chemical sputtering produced an integrated carbon influx of 1.7 × 1021 neutrals/s. The average carbon concentration in the computational volume increased from 0.012% with only physical sputtering to 0.182% with both chemical and physical sputtering. This increase in the carbon inventory produced more radiated power which is in better agreement with experimental measurements.
Experimental Study of Atmospheric Pressure Glow Discharge
Authors: Trunec D. , Brablec A. , Šťastný F. 
Published: July 2007

AbstractThe atmospheric pressure glow discharge (APGD) is a new type of the discharge discovered by OKAZAKI et al. [1] recently. The APGD can be used in practical application (e.g. ozone generation), but the phenomena occurring in the discharge are not fully understood. We studied the APGD driven at 50 Hz, applied voltage up to 5 kV and burning in helium, argon and nitrogen. We used a planar configuration of discharge cell: metal electrode ‐ dielectric plate (1 mm thick) ‐ discharge gap (1.5 mm thick) ‐ dielectric plate ‐ metal electrode. Between the metal electrode and the dielectric plate a fine metal mesh was placed. For each gas we recorded the time dependence of power supply voltage and the time dependence of charge transferred through the discharge. We recorded also the discharges by the CCD camera with a video recorder. The same measurements were done in case of the discharge cells without the metal mesh. The metal mesh changes the discharge significantly. In the case of discharge cell with the mesh we can observe a homogeneous discharge and only one peak in the discharge current per half cycle of applied voltage while in the case of the discharge without mesh we observed individual micro‐discharges and many pulses in the current per half cycle. This effect is most obvious in helium.In order to explain the observed phenomena we calculated the electric field in the discharge cell for APGD and propose a possible explanation of APGD. It has been found that the mesh does not influence the electric field in the discharge gap. Thus we propose that the mesh could influence the discharge by its electrical resistance, which is higher than the resistance of the metallic electrode.
Optical Properties of Laser‐Produced Plasmas
Authors: Fehr R. , Schlanges M. , Kraeft W.‐D. 
Published: July 2007

AbstractThe interaction of high intensity femtosecond laser pulses with matter allows the production of plasmas with high electron densities. This enables the study of basic plasma physics in regimes relevant to astrophysics, atomic physics, or in strongly correlated plasmas. Much of the understanding of such plasmas depends on the knowledge of the optical properties. The diagnostic requires theoretical models for the interpretation of experimental data. We study the dielectric function and the electric conductivity in the framework of a generalized Drude model. The required collision frequencies are taken in Born and strong coupling (T‐matrix) approximations. Furthermore, we try to give an estimation of the influence of nonlinear, high frequency effects of the electrical field. In order to describe the temporal evolution of the plasma, we determine the composition of the plasma solving Saha's equation. Therefore we investigate different approximations for the effective ionization energy including Padé formulas for the correlation part of the chemical potential.
Ionization Equilibrium and Equation of State of Hydrogen Plasmas in Strong Magnetic Fields
Authors: Potekhin A. Y. , Chabrier G. , Shibanov Yu. A. , Ventura J. 
Published: July 2007

AbstractWe study hydrogen plasmas at magnetic fields B ∼ 1012 – 1013 G, densities pH ∼ 10−3 – 103 g cm−3 and temperatures T ∼ 105.5 –106.5 K, typical of photospheres of middle‐aged cooling neutron stars. We construct an analytical free energy model of the partially ionized plasma, including into consideration the decentred atomic states, which arise due to the thermal motion across the strong field. We show that these states, neglected in previous studies, may contribute appreciably into thermodynamics of the outer atmospheric layers at pH ≲ 1 g cm−3 and typical B and T. We take into account Coulomb non‐ideality of the ionized component of the plasma affected by intense magnetic field. Ionization degree, occupancies and equation of state are calculated, and their dependences on the temperature, density and magnetic field are studied.
Remarks on Luttinger's Derivation of Kubo's Conductivity Formula
Authors: Lee M. H. 
Published: July 2007

AbstractLuttinger has given a derivation of Kubo's static conductivity formula in a famous paper some thirty years ago. In a subsequent analysis to obtain the Einstein relation, he introduced an assumption. We show that this assumption is not consistent with linear response theory, on the basis of which the conductivity formula is derived. This inconsistency can be removed. At the same time, one can extend Luttinger's treatment to include the dynamic conductivity. This generalization is allowed by the recurrence relations method, which solves the Heisenberg equation of motion formally as well as explicitly.
Characterization of the State of Hydrogen at High Temperature and Density
Authors: Militzer B. , Magro W. , Ceperley D. 
Published: July 2007

AbstractFermionic path integral Monte Carlo simulations have been applied to study the equilibrium properties of the hydrogen and deuterium in the density and temperature range of 1.6 < r3 < 14.0 and 5000K < T < 167000K. We use this technique to determine the phase diagram by identifying the the plasma, the molecular, atomic and metallic regime. We explain how one can identify the phases in the path integral formalism and discuss the state of hydrogen for 5 points in the temperature‐density plane. Further we will provide arguments for the nature of the transitions between the regimes.
Diagnostics of a Chemically Active, Pulsed Microwave Plasma for Deposition of Quartz‐like Films
Authors: Brockhaus A. , Behle St. , Georg A. , Schwabedissen A. , Soll Ch. , Engemann J. 
Published: July 2007

AbstractA remote microwave plasma has been used for the deposition of scratch‐resistant quartz‐like films. Process gases are argon, oxygen, and hexamethyl‐disiloxane. Input power is modulated and the effects on the plasma as well as on the deposition process are studied by means of various diagnostic methods. The film deposition rate is slightly reduced under most conditions but film quality (i.e., cluster size, roughness, scratch resistance) may be improved. A precursor has been identified by mass spectrometric measurements. Its relation to volatile oxides is discussed. The atomic oxygen density and the electron density are determined temporally‐resolved. By a suitable choice of the pulse frequency the time‐averaged densities of both species can be significantly enhanced as compared to the continuous case. Consideration of the plasma power balance explains how electron density and temperature are influenced by pulsing. It is concluded that the optimum pulse frequency has to be matched to the electron loss rate which mainly depends on the geometrical dimensions of the process chamber.
Architecture for delivery of broadband services to the residence
Authors: Coathup L. , Goddard G. W. , McEachern J. , Bears J. 
Published: July 2007

AbstractThis paper presents a technology and architecture perspective on the cost of evolving today's copper access network, optimized for POTS, to a fibre access network providing both narrowband and broadband services. Architectures are assessed using application studies based on cost models for actual routes in North America. This study identifies three architectures as serious candidates (i.e. close to copper in cost) for providing POTS service in 1992: the double star, the active pedestal and the star‐bus.The active pedestal and the star‐bus architectures were similar in first costs and were the least expensive, costing between 5 and 15 per cent more than the copper reference depending on the number of subscribers subtending a given optical fibre. The double star is 20 per cent more expensive than the copper reference.All three architectures are potentially attractive for broadband service upgrade depending on the bandwidth required per subscriber. The star‐bus is most bandwidth sensitive. Moderate video bandwidths, nominally 150 Mb/s/subscriber, favour the active pedestal architecture. Conversely, service environments requiring much greater than 150 Mb/s/subscriber favour the double star architecture.
The realization of integrated services in a digital distributed star local network
Authors: Brady Jon D. 
Published: July 2007

AbstractThe BIDS system will go on trial in early 1990 and it will be a unique system for combining broadband, telephony and data services. The present design uses analogue and digital transmission techniques, but a design for a completely digital system may be required. A study of future requirements had to be undertaken to ensure that the system would adequately serve the customer of the year 2000 and onwards. A design for a digital secondary link is presented employing a modular optical dual‐wavelength diplex system.
A fiber‐optic system for deployment of pots and CATV services in the FRG
Authors: Romans Claude , Large David 
Published: July 2007

AbstractAn optical system architecture intended to provide subscriber access for future network sevices must also support existing services at a cost equivalent to copper. An integrated optical‐fiber system which meets this criterion and provides both CATV and telephone service has been designed under contract to the Deutsche Bundespost and is planned for pilot installation early in 1990 in Köln, Federal Republic of Germany.A bus network was chosen for implementation of the trial system because of the advantages it provides over a point‐to‐point star network. Economies result from using much less fiber per subscriber, and from the sharing of optical transmitter and receiver costs among many subscribers.The telephony portion of the system initially provides existing telephone service based on digital transmission technology yet is configured to support the development of new services. The CATV portion of the network is designed to be functionally equivalent to the coaxial system now being deployed, but offers advantages in reliability and future expansion possibilities.The implementation of a system using a bus architecture to provide network access for telephone and broadband CATV services over optical fiber cables is described.
A star‐configured fiber‐to‐the‐curb system
Authors: Menendez R. C. , Vogel M. O. 
Published: July 2007

AbstractFiber‐to‐the‐curb (FTTC) system proposals have arisen because of the present high cost of fiber‐to‐the‐home (FTTH) systems. With FTTC systems, fiber is brought only as far as the service access point (SAP). From there, copper drops carry signals from the SAP to several residences. Owing to the extensive sharing of optical sources and the fibers running to the SAP, the per‐subscriber system cost is greatly reduced relative to the per‐subscriber cost of a FTTH system. In addition, elimination of the optical network unit (ONU) at the home may offer new options for powering and battery back‐up.This paper presents an analysis of a star‐configured, fiber‐to‐the‐curb distribution network that serves up to ninety‐six customers, initially providing two plain old telephone service (POTS) channels to each customer. Three system variations, serving either four, six, or eight customers per SAP, are examined. We also estimate the installed first costs (IFC) of the distribution link (remote node to customer) for the three FTTC scenarios and compare them to the IFC of a FTTH system with similar capabilities. Star‐configured FTTC architectures can be installed for substantially less ($1180‐$825/customer for four to eight customers per SAP) than the estimated $2920 per subscriber cost associated with FTTH systems. Finally, we propose an upgrade strategy, consistent with the passive photonic loop (PPL) network, to support future high bandwidth services.
Priority cell discarding for overload control in BISDN/ATM networks: An analysis framework
Authors: Petr David W. , Frost Victor S. 
Published: July 2007

AbstractThe broadband integrated services digital networks (BISDNs) of the future will use asynchronous transfer mode (ATM) for switching and transport of basic transport units called cells. These networks are likely to exhibit extremely bursty traffic characteristics which could cause significant queue overload conditions. This paper suggests that priority cell discarding, in which a delivery priority (also known as a loss priority) is assigned to each cell, is a viable alternative for controlling this overload. We also present a framework for the analysis and comparison of the performance of such priority discarding systems. The framework consists of a general analysis model appropriate for BISDNs using ATM, a two‐dimensional structural classification of priority discarding algorithms and suggestions for performance measures, one of which is a generalization of the often‐used throughput measure. We illustrate how this framework can be useful in systems analysis by introducing a specific discarding optimization problem.
New microwave and fibre‐optic supertrunking system configurations
Authors: Straus T. M. , Hsu R. T. , Kaufman L. A. 
Published: July 2007

AbstractRapidly changing fibre‐optic and AML microwave technologies have opened up a new range of possibilities in implementing CATV supertrunks. These considerations apply not only to new builds, but also to many existing AML microwave systems whose reach could be extended. The same technologies can be applied to improve system reliability either through redundancy configurations or by dividing overly long microwave paths into smaller segments. Combinations of the two technologies are explored. System performance improvements possible with higher power transmitters and on‐frequency repeaters are delineated. Advantages of configurations employing fibre to AML, AML to fibre, ‘low power’ channelized AML with high power microwave repeaters, and fibre in parallel with AML are set forth.
Standardization of a multi‐configuration medium access protocol for broadband ISDN
Authors: Woloszynski Charles H. 
Published: July 2007

AbstractThis paper examines the current work within various standards bodies to define a multi‐configuration medium access control (MAC) protocol for operation between broadband ISDN terminals. To begin, the configurations in which the MAC protocol is expected to operate are introduced. The relation between the MAC protocol and the broadband ISDN resource allocation schemes is then discussed. Several MAC protocol proposals currently being discussed in various standards bodies, each with unique assumptions regarding resource allocation in broadband ISDN, are then described and compared. Finally, areas for future work on this topic are identified.