bluuebunny/crossref_metadata_2025_split huggingface dataset:
Investigation of the Radiation Mechanism of Microwave Excited Cluster Lamps
Authors: Heintel M. , Neiger M. , Scholl R. 
Published: July 2007

AbstractExperimental and theoretical investigations towards a better understanding of the radiation mechanisms in WO2Br2‐discharges, so‐called “cluster lamps” are presented. The main purpose of the investigation is to find out whether a major part of the continuum emitted from these discharges, which in the past has been interpreted as thermal cluster radiation, could also originate from molecular band radiation, in particular from triatomic molecules in colder discharge regions. Comparing emission spectra of WO2Br2‐discharges from different plasma regions, using lamps operated at different vapor pressures and power levels (i.e. non‐LTE and LTE‐discharges), we conclude that by far the major part of the strong continuum radiation emitted from WO2Br2 lamps is indeed thermal radiation of hot tungsten cluster particles. WO— (below 550 nm) and WO2‐molecular radiation (above 650 nm), which is superimposed on the cluster continuum, also contribute to the total radiation output, but to a lesser degree. A crude model for WO2 molecular emission is presented. Unfortunately, the WO2 emission component greatly impedes proper fitting of the measured cluster continuum to a thermal cluster model.
Modal and Focusing Properties of Plasma Based Waveguides for X‐Ray Beams
Authors: Kukhlevsky S. V. , Kozma L. 
Published: July 2007

AbstractModal and focusing properties of the plasma based waveguide having a parabolic profile of the electron density are treated for x‐ray beams with the ray‐transfer and paraxial‐envelope equations. Conditions on the single mode, multimode and leaky mode propagation in straight and tapered plasma channels are evaluated. The near‐ and far‐field patterns of these modes are calculated. The main result is that the mode structure is guide length and wavelength dependent, resulting in the guide length and wavelength dependent conditions for the guiding and focusing. The modal analysis finds its application in the field of x‐ray lasers, extremly high harmonic generation and x‐ray beam focusing, in which it may be helpful to design guides for optimum beam propagation. Futhermore, the mode properties are extremly simple and provide an idealised model for the real plasma waveguides.
Highly Ionised Carbon in Capillary Discharge Plasma
Authors: Föurster A. , Beule D. , Conrads H. , Ebeling W. 
Published: July 2007

AbstractSpectroscopic data indicate that fully ionised carbon ions occur in capillary discharge experiment using a polyethylene tube. On the basis of the simultaneously obtained data for electron density and temperature we calculate the charge‐state distribution. The theoretical model takes into account several dense plasma effects and yields the detailed composition of the polyethylene plasma over time. For typical densities of the discharge plasma a temperature of ≥ 30eV/kB is shown to be sufficient to generate a substantial amount of fully ionised carbon.
Shock‐Compression Experiments and Reflectivity Measurements in Deuterium up to 3.5 Mbar using the Nova Laser
Authors: Collins G. W. , Celliers P. M. , Gold D. M. , Da Silva L. B. , Cauble R. 
Published: July 2007

AbstractWe report on measurements of the equation of state and optical reflectivity at 1064 nm wavelength of a high pressure shock front propagating through a sample of liquid deuterium. We find that the shock front reflectivity increases from a low value (< 3.5%) to a saturation level of 65% in the pressure range of 0.22 ‐ 0.55 Mbar. The pressure range where this metallization transformation takes place coincides with the pressure range where high compressibilities were observed on the principal Hugoniot.
Model for Shock‐Compressed Liquid Deuterium
Authors: Ross M. 
Published: July 2007

AbstractThe equation of state of dense liquid deuterium has been calculated using a model in which the Helmholtz free energy is approximated as the composition average of the free energy of pure molecular and metallic hydrogen. The composition is determined by free energy minimization. Calculations for shock‐compressed liquid deuterium are in good agreement with experiments to a pressure of 2.1 Mbar. At about 1 Mbar and 20000 K, liquid deuterium is 90 % dissociated and is a nearly liquid degenerate metal. The model predicts that molecular dissociation will lead to negative values of (∂P/∂T)v in the range 4000 K to 10 000 K and volumes below 7 cm3/mol. This feature suggests the formation of covalently bonded species in the partially dissociated mixture.
Generalized Kadanoff–Baym Theory for Non–Equilibrium Many–Body Systems in External Fields. An Effective Multi–Band Approach
Authors: Bonitz M. , Kwong N. H. , Semkat D. , Kremp D. 
Published: July 2007

AbstractThe Kadanoff‐Baym approach (two‐time nonequilibrium Green's functions approach) is extended to charged particle systems in external fields. It is shown that its combination with an effecive multi‐band pictureThis concept was first presented at the German Physical Society (DPG) Spring meeting, Regensburg, March 1998 [1].
yields a powerful theoretical and numerical method to describe correlated many‐body systems in nonequilibrium.
Wave Packet Molecular Dynamics Simulations of Hydrogen Near the Transition to a Metallic Fluid
Authors: Knaup M. , Reinhard P.‐G. , Toepffer Ch. 
Published: July 2007

AbstractRecent multiple‐shock experiments of hydrogen at very high pressures show a transition from nonconducting to metallic behaviour at about 140 GPa and a temperature of approximately 3000 K [1].We simulate hydrogen at various densities and temperatures in the region of this transition. As a theoretical tool we employ “Wave Packet Molecular Dynamics” simulations. This method was originally used by Heller for a description of the scattering of composite particles like simple atoms and molecules [2]; later it was applied to Coulomb systems by Klakow et al. [3]. From the simulations we can extract for example energies, pressure, structure information like pair‐correlations and auto‐correlation functions of current and velocity as well as the resulting transport coefficients.In this work we show the equation of state and proton‐proton pair correlation functions for a constant electron number‐density n = 2.016 × 1029m−3 (rs = 2). We compare our results with other theoretical approaches: Path Integral Monte Carlo simulations of Magro et al. [5], Tight Binding Molecular Dynamics calculations of Lenosky et al. [7], and analytical approaches via dissociation model by Nagel et al. [8] and the linear mixing model by Ross [9].
The Long‐wavelength Limit of the Dielectric Function for Dense Plasmas
Authors: Reinholz H. , Redmer R. , Röpke G. , Wierling A. 
Published: July 2007

AbstractThe dielectric function of a system of charged particles is investigated for arbitrary degeneracy within a linear response theory. This approach allows for inclusion of collisions, thus going beyond the RPA and treating the electrical conductivity in consistency with the dielectric function. A general expression for the collision integral in the whole (k, w) plane is presented. Special attention is given to the long‐wavelength limit deriving a frequency‐dependent collision term. In the limit k = 0 and w = 0, the Ziman formula for the electrical conductivity in metallic systems is reproduced. By inspection of the high‐frequency limit, it is shown that the third moment of the response function is in accordance with the well‐known third moment sum rule.
Thermodynamic Properties of Dense Plasma of Shock—Compressed Metals
Authors: Gryaznov V. , Iosilevski I. , Fortov V. E. 
Published: July 2007

AbstractQuasi‐chemical representation (“Chemical Model”) was extrapolated for description of thermodynamic properties of plasma of shock compressed extra‐foam nickel and iron samples. Modified Coulomb correction [High Temperature, 18 (1980) 447], was generalised for the case of multiply ionised partially degenerated hot dense plasmas. Intensive short‐range repulsion of heavy particles (atoms and ions) and electron degeneracy was taken into account in combination with simplified form of “Cold Additive”. Satisfactory agreement of theory and experiment was obtained for nickel and iron Hugoniots. This agreement proved to be valid when the approximation was extrapolated into the region of extra‐dense plasma of highly compressed solid iron.
Relaxation of Background Electrons and Ions in Plasma Crystals
Authors: Chutov Yu. , Schram P. 
Published: July 2007

AbstractThe Liouville equation is considered for the statistical system consisting of identical constructureless free particles and grains initially. It relaxes then due to a collection of the particles by the grains. Dusty plasmas are particular cases of this system. The free and collected particles are considered as a common sub‐system which is described by the common whole distribution function. It is shown that this sub‐system is described by the complex integral‐differential equation which can be expected to lead to Non‐Markovian kinetics.Computer modeling shows that background electrons and ions can be non‐ideal components of relaxing dusty plasmas in plasma crystals due to the intensive charge exchange of electrons and ions with dust particles even in the cases where their numbers in the Debye cube are large. The selective collection of electrons and ions by dust particles causes their deviation from the initial equilibrium as well as the non‐equilibrium evolution of the self‐consistent electric potential and electric charge of dust particles.
Molecular Dynamics Simulations of the Dynamics of Correlations and Relaxation in an OCP
Authors: Zwicknagel G. 
Published: July 2007

AbstractThe short time dynamics of the transition from an initial nonequilibrium state to an equilibrium state is investigated for an OCP by molecular dynamics (MD) simulations. Two different initial configurations are considered which allow to study either the build‐up of binary correlations or the relaxation of the single particle distribution. For a weakly coupled plasma the observed time scale for relaxation is much longer than the characteristic time for the correlation build‐up while the two time scales become equal for nonideal plasmas with Γ > 0.5.
Conductivity Measurements of Nonideal C Plasmas
Authors: Haun J. , Kunze H.‐J. 
Published: July 2007

AbstractWe report measurements of the conductivity of nonideal C‐plasmas. They are produced by evaporating a carbon‐wire placed in a capillary within some hundred nanoseconds. Homogeneity of the plasma is obtained by the use of a ‘pre‐heating‐system’ which heats the wire before the main discharge. This way the initial resistivity of the wire is decreased, the discharge time is shortened. The reproducibility of the plasma is enhanced, the growth of instabilities is reduced. The conductivity is measured during 1 ms of the discharge. The particle density is of the order of 1022 cm−3 while the electron temperature is varying between 8000 K and 25000 K, the electron density is about 1018 cm−3. The temperature is measured spectroscopically by fitting a Planck curve to the spectrally resolved emission profile. The results are compared with theories from Spitzer, Ziman and the SESAME‐data.
Current Jumps and Hysteresis in a Single‐ended Q‐Machine in Connection with the Electrostatic Ion‐Cyclotron Instability
Authors: Avram C. , Schrittwieser R. , Sanduloviciu M. 
Published: July 2007

AbstractWe report on an investigation in a single‐ended Q‐machine where the current‐voltage characteristic of a small collector showed some interesting new features. The most interesting of these was a sudden jump of the current at the onset of the electrostatic ion‐cyclotron instability. This jump was also accompanied by hysteresis. Besides that, the characteristic showed another trivial type of hysteresis that was only due to a temporary covering of the collector by alkaline metal from the plasma. The former phenomenon could be an indication that the well‐known nonlinear potential structures that appear periodically in front of the collector during a cycle of a high‐amplitude electrostatic ion‐cyclotron instability, are related to inelastic collisions of accelerated electrons with alkaline vapour present in the plasma column.
A Comparative Study of Single and Double Langmuir Probe Techniques for RF Plasma Characterization
Authors: Castro R. M. , Cirino G. A. , Verdonck P. , Maciel H. S. , Massi M. , Pisani M. B. , Mansano R. D. 
Published: July 2007

AbstractIn this study, the plasma density and electron temperature of Radio Frequency (RF) plasmas were determined by three types of Langmuir probes, namely a conventional double probe, a single probe with RF choke and a single probe with RF choke and compensating electrode. The same plasmas were characterized by the three probes, each performing three measurements per plasma condition, in order to determine the precision of the measurement results. After performing a comparative analysis, which looked at the precision and the accuracy of these results, the conclusion is that the double probe, which has already the advantage of the simplest construction, yields the most reliable results for both capacitively and inductively coupled RF plasmas. The single probe with RF choke and compensating electrode has a similar precision as the single probe without compensating electrode, but its accuracy is better.
Quasiclassical Statistical Thermodynamics and New Padé Approximations for the Free Charges in Strongly‐Coupled Plasma
Authors: Ebeling W. , Stolzmann W. , Förster A. , Kasch M. 
Published: July 2007

AbstractHNC equations in combination with effective quasi‐classical potentials are used to calculate correlation functions and the thermodynamic properties of the free charges in semi‐classical non‐degenerate quantum plasmas. The interactions of the free particles are taken into account via effective potentials obtained from the Slater sum method. Analytical formulae reproducing the known limits and the HNC‐results are constructed. Finally quantum effects are included as corrections by using known analytical results. This method is used to develope new Padé approximations for the subsystem of the free charges in mass‐symmetrical as well as for mass‐unsymmetrical hydrogen‐like plasmas. The most essential result of our investigations is, that in the classical limit the scaling properties correspond to the OCP, e.g. the thermodynamic functions follow for large coupling strength Γ a Berlin‐Montroll‐Rosenfeld asymptotics via a Γ + b Γv + c ln Γ + d. Including quantum effects, the coefficients depend on the temperature, e.g. the slope a(T) increases with decreasing T converging to the classical limit. The new formulae are compared with earlier variants.
The Ponderomotive Force on a Charge q, Moving in an Electromagnetic Field
Authors: Kildal A. 
Published: July 2007

AbstractEquations of motion of a single charged particle are derived to second order in E where E is an electromagnetic field. By averaging over the wave‐period we find the ponderomotive force on the particle. This force may lead to a transport of matter as is also the case in ordinary hydrodynamics. There the effect is called acoustic streaming. We also suggest that the well‐known Landau damping may be considered as beeing due to a ponderomotive force.
Ion Temperature Measurement in the Edge Region of SINP Tokamak by a Retarding Field Analyser
Authors: Raychaudhuri S. 
Published: July 2007

AbstractBased on the principle of retarding field analyser an ion energy analyser has been developed for the measurement of ion temperature in the edge plasma region of the SINP tokamak. This has been used to determine the dependence of the ion temperature on the safety factor q in the normal q region (q=2 to 4), plasma current, plasma electron temperature and also the Spitzer resistivity.
Thermal Plasmas for Material Processing
Authors: Henne R. 
Published: July 2007

AbstractPlasma technologies have undoubtedly gained high importance due to their outstanding properties and they have found a large field of scientific and technical applications. Thermal plasmas with temperatures of around 10,000 K and more are particularly suitable for material processing, e.g. for melting, cutting, welding or coating. They are also of increased interest in waste destruction or material synthesis. Following some remarks about the definition of “thermal plasmas” and their generation some representative examples of applications are described in more detail together with considerations about the relevant technical and economic importance at present and potentially in future.
Effects of Energetic Electrons on Collector and Source Potentials in a Finite Ion Temperature Plasma
Authors: Čerček M. , Gyergyek T. , Stanojević M. 
Published: July 2007

AbstractFormation of the potential in a two‐electron‐temperature plasma region facing a floating collector was studied theoretically with a kinetic plasma‐sheath model and by electrostatic particle simulation. The electrons were described by truncated full Maxwellian velocity distribution functions and the ions by an accelerated half‐Maxwellian velocity distribution function. The collector potential and the plasma source sheath or presheath potential drop were evaluated as functions of the hot to cool electron temperature ratio and the hot electron density ratio using Vlasov and Poison equations. The results showed that the presheath potential drop varied continuously with electron composition ratio for lower values of the electron temperature ratio, while for higher values in a narrow composition ratio range, triple values of the potential were found. Of the two physically acceptable values, the lower was characterized by the cool electrons and the higher by the hot electrons. It is anticipated that a current‐free double layer structure is formed in the plasma system between these two potential regions. The collector floating potential, as a function of electron composition ratio, is mainly dominated by the hot electrons, since already a small value of hot electron current is sufficient to compensate the ion saturation current. In order to complete the theoretical investigation we also study the hydrogen plasma system with the XPDP1 particule‐in‐cell simulation code composed at Berkeley. At certain plasma parameter values formation of a double layer structure was observed. The potential Values on the upper and lower side of the double layer, as well as that of the collector floating potential, corresponded very well to the calculated values. On the upper side the plasma was composed of ions, accelerated through the source sheath potential drop, and electrons consisting of cool full Maxwellian and hot truncated full Maxwellian populations. On the lower side only hot electrons and ions additionally accelerated through the double layer were found.
The design and installation of the Cleveland, Ohio point‐to‐multipoint CATV fiber‐optic transport system
Authors: Brinkerhuff William C. 
Published: July 2007

AbstractAnalog fiber‐optic transmission system use is becoming commonplace and widespread for point‐to‐point CATV programme channel trunking applications. Owing to improvements in single‐mode fiber, device technologies and availability of single‐mode optical splitter/couplers, it is now technically and economically feasible to implement point‐to‐multipoint CATV trunking systems.This paper will describe the Cleveland, Ohio point‐to‐multipoint fiber‐optic transport system design, the pros and cons of analog FM versus digital systems, the fiber plant and the end‐to‐end performance of the installed fiber‐optic system.The multichannel FM/FDM fiber‐optic system deployed by The Ohio Bell Telephone Company (OBT), an Ameritech company, was manufactured and installed by Catel Telecommunications, Inc. of Fremont, California.
Admission control over mixed traffic in ATM networks
Authors: Lombardo A. , Palazzo S. , Panno D. 
Published: July 2007

AbstractThe new techniques for broadband ISDNs, such as ATM, will provide flexible and efficient allocation and bandwidth for communication services. These services may have very different traffic statistics and performance requirements. Therefore, criteria to decide about acceptance of new connection requests into the network must take into account which traffic and performance class connections belong to. This paper proposes a decision rule for admission control over mixed traffic which consists of connections possibly referring to different classes of traffic and performance. The rule, which is derived by approximate analysis, is based on the concept of maximum use of an ATM link. It is shown that it can be applied to a wide range of telecommunication services.
Dynamic capacity management in the BISDN
Authors: Burgin John 
Published: July 2007

AbstractUse of virtual paths (VPs) in the broadband ISDN (BISDN) presents network operators with the ability to make processing intensive resource management decisions for flows of traffic instead of individual connections. Altering the amount of capacity assigned to different VPs provides the ability to reconfigure the network dynamically to respond to changes in traffic demand. This paper studies the dynamic behaviour of some algorithms for assigning capacity to VPs for a range of time‐varying offered traffic inputs.
An approach to controlling congestion in ATM networks
Authors: Eckberg A. E. , Luan D. T. , Lucantoni D. M. 
Published: July 2007

AbstractDetermining approaches to congestion and flow control, especially real‐time components in an overall strategy, is recognized as one of the fundamental challenges facing broadband ‘packet‐based’ information transport, as, for instance, in the case of BISDN/ATM, In this paper we summarize basic issues underlying this subject, and describe a particular approach to achieving a multilayer broadband congestion, flow and error‐control architecture, based on a ‘core’ congestion control strategy that we term bandwidth management. The modular and layered nature of this control architecture is described, and shown to lend itself to a structured approach to characterizing the control architecture performance.
CATV fibre‐optic supertrunking: A comparison of parameters and topologies using analog and/or digital techniques
Authors: Borelli Vincent R. , Gysel Hermann 
Published: July 2007

AbstractFibre‐optic supertrunking has a well‐established place in larger CATV networks. Supertrunks have to be transparent to the quality of the transmitted TV signals and they have to have a negligible impact on the system reliability of the total network. At least 60 dB (weighted) video SNR has to be achieved and down times of less than one hour per year per fibre are desirable. AM on fibre can achieve these goals only in shorter supertrunks. FM and digital modulation techniques with a higher loss budget than AM are well suited for high transmission quality as well as for redundant supertrunk topologies, achieving excellent system availability numbers at the expense of increased equipment complexity.
Cable television on fibre in stand‐alone networks and in systems combined with telephony
Authors: Edwards Terry 
Published: July 2007

AbstractThis paper presents details of dedicated cable television systems (stand‐alone cable TV), and combined cable TV/telephony systems, based upon the economic implementation of optical fibre technology. The factors that determine the choice of these two approaches are described and examples are given based upon systems designed by Raynet Corporation. Techno‐economic issues are debated and the need for effective future‐proofing is emphasized. In particular, the critical choice between fibre to the last amplifier (FTTLA) and fibre to the curb (FTTC) is discussed. Architectures are described for trunk and distributed systems and performance characteristics are given for a specific network, optical elements and electro‐optic interfaces. Detailed considerations relating to future developments conclude the paper.