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1

Kinetic description of quantum plasma dielectric response  

NASA Astrophysics Data System (ADS)

A linear response tensor for nonrelativistic isotropic quantum plasma of spinless particles interacting electromagnetically is obtained within Hartree's mean-field approximation, and its phenomenological relativistic generalization is proposed. Analytic properties of quantum plasma longitudinal response function are considered, and their implication for collective longitudinal oscillations in quantum plasmas (and evolution of perturbations) is discussed.

Vladimirov, S. V.; Tyshetskiy, Yu. O.

2012-02-01

2

Unified fluid/kinetic description of magnetized plasmas  

SciTech Connect

Unified fluid/kinetic equations for the plasma perturbed density ({tilde n}), parallel flow velocity ({tilde u}{sub {parallel}}) and temperature ({tilde T}) are developed in a sheared slab geometry by calculating the fluid moment closure relations kinetically. At first, a set of (unclosed) nonlinear perturbed fluid equations for {tilde n}, {tilde u}{sub {parallel}} and {tilde T} is developed using a drift ordering analysis and a new gyroviscous force ({del} {center dot} {product}{sub g}). Thereafter, to develop linear closure relations for b {center dot} {del} {center dot} {tilde product}{sub {parallel}} and {tilde q}{sub {parallel}}, a drift-kinetic version of a Chapman-Enskog-like (CEL) equation is developed and solved by using a moment approach and a physically realistic collision operator (Lorentz scattering operator plus the momentum restoring terms.) The resultant closure relations for b {center dot} {del} {center dot} {tilde product}{sub {parallel}} and {tilde q}{sub {parallel}} unify both the fluid and kinetic approaches. In the collisional fluid limit the equations reduce to the well-known Braginskii equations. In the adiabatic limit they reproduce the usual kinetic results, including Landau damping. It is shown that the CEL approach is more compatible with a fluid-like description of plasmas than the usual drift/gyro kinetic approach. A remarkable simplification of these complicated closure relations is achieved by using single power of plasma dispersion functions with modified arguments. The results are compared with other recently developed Landau damping models and shown to be more accurate, complete and physically meaningful. The resultant set of nonlinear fluid/kinetic equations (with linear closure relations) will be applied to various microinstabilities in tokamak plasmas and drift type microturbulence in a separate paper. 19 refs., 7 refs., 1 tab.

Chang, Zuoyang; Callen, J.D.

1991-06-01

3

Kinetic description of electron plasma waves with orbital angular momentum  

SciTech Connect

We describe the kinetic theory of electron plasma waves with orbital angular momentum or twisted plasmons. The conditions for a twisted Landau resonance to exist are established, and this concept is introduced for the first time. Expressions for the kinetic dispersion relation and for the electron Landau damping are derived. The particular case of a Maxwellian plasma is examined in detail. The new contributions to wave dispersion and damping due the orbital angular momentum are discussed. It is shown that twisted plasmons can be excited by rotating electron beams.

Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)

2012-11-15

4

On kinetic description of electromagnetic processes in a quantum plasma  

NASA Astrophysics Data System (ADS)

A nonlinear kinetic equation for nonrelativistic quantum plasma with electromagnetic interaction of particles is obtained in the Hartree's mean-field approximation. It is cast in a convenient form of Vlasov-Boltzmann-type equation with ``quantum interference integral'', which allows for relatively straightforward modification of existing classical Vlasov codes to incorporate quantum effects (quantum statistics and quantum interference of overlapping particles wave functions), without changing the bulk of the codes. Such modification (upgrade) of existing Vlasov codes may provide a direct and effective path to numerical simulations of nonlinear electrostatic and electromagnetic phenomena in quantum plasmas, especially of processes where kinetic effects are important (e.g., modulational interactions and stimulated scattering phenomena involving plasma modes at short wavelengths or high-order kinetic modes, dynamical screening and interaction of charges in quantum plasma, etc.) Moreover, numerical approaches involving such modified Vlasov codes would provide a useful basis for theoretical analyses of quantum plasmas, as quantum and classical effects can be easily separated there.

Tyshetskiy, Yu.; Vladimirov, S. V.; Kompaneets, R.

2011-11-01

5

Unified fluid/kinetic description of magnetized plasmas  

NASA Astrophysics Data System (ADS)

The unified fluid/kinetic equations developed in part 1 of this work are used to study plasma drift type microinstabilities. A generalized perturbed Ohm's law derived which is uniformly valid for arbitrary collisionality omega/nu and adiabaticity omega/k(parallel) upsilon(sub t). For electron drift waves we demonstrate that the collisional and collisionless drift wave instabilities can be uniformly described by replacing the Spitzer resistivity with a generalized pseudo-resistivity. Similarly, for ion drift type modes we obtain a uniformly valid dispersion relation for the ion temperature gradient modes (eta(sub i) modes). The eta(sub i) threshold as a function of ion-ion collisionality and ion Landau damping strength is addressed. Applying the unified equations to electron electromagnetic modes leads to generalized coupled equations for tilde phi and tilde A(parallel) which include electron Landau damping effects and are valid for any omega/nu. It is shown that the semi-collisional micro-tearing and drift-tearing modes of Drake and Lee can be easily reproduced in the appropriate limit. Generalization of the two-field Hasegawa-Wakatani turbulent equations to include electron temperature fluctuations and linear Landau damping effects is also discussed. Finally, a new method is presented to facilitate the study of magnetic trapped particle modes using our kinetic closure procedure. It is found that by including the trapped particle effects in the closure relations, the usual separation of the fluid equations into trapped and untrapped components becomes unnecessary.

Chang, Zuoyang; Callen, J. D.

1991-07-01

6

Reduced kinetic description of weakly-driven plasma waves  

SciTech Connect

A model of kinetic effects in Langmuir wave dynamics is presented using a nonlinear distribution function that includes particle separatrix crossing and self-consistent electrostatic evolution. This model is based on the adiabatic motion of electrons in the wave to describe Bernstein-Greene-Kruskal-like Langmuir waves over a wide range of temperatures (0.1{<=}k{lambda}{sub D}{<=}0.4). The asymptotic distribution function yields a nonlinear frequency shift of the Langmuir wave that agrees well with Vlasov simulations, and can furthermore be used to determine the electrostatic energy required to develop the phase-mixed, asymptotic state. From this incoherent energy, energy conservation is employed to determine a simplified model of nonlinear Landau damping. The resulting nonlinear, dynamic frequency shift and damping are then used in an extended three-wave-type model of driven Langmuir waves and compared to Vlasov simulations in the context of backward Raman scattering.

Lindberg, R. R.; Charman, A. E.; Wurtele, J. S. [Department of Physics, University of California, Berkeley, Berkeley, California 94720 (United States) and Center for Beam Physics, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2008-05-15

7

Kinetic and spectral descriptions for atomic processes involving autoionizing resonances in high-temperature plasmas  

NASA Astrophysics Data System (ADS)

An investigation has been in progress on the influence of autoionizing resonances on atomic processes in high-temperature plasmas, particularly those encountered in magnetic- and laser-fusion research and in astrophysics. In the kinetic-theory description, account is taken of the indirect contributions of autoionizing resonances to the effective rates for excitation, de-excitation, ionization, and recombination. A microscopic kinetic-theory foundation is employed for the systematic reduction to the macroscopic radiation-hydrodynamics description. From the spectral perspective, particular emphasis has been directed at radiative emission processes from autoionizing resonances. These processes can give rise to resolvable dielectronic-recombination satellite features, which have been analyzed to determine plasma temperatures, densities, electric and magnetic-field distributions, and charge-state distributions. We also investigate radiative absorption processes, which play important roles in the denser plasmas encountered in laser-matter interactions. Particular emphasis is directed at radiative excitation processes involving autoionizing resonances, which can provide significant contributions to the non-equilibrium ionization structures and to the radiative absorption and emission spectra in the presence of intense electromagnetic fields. A reduced-density-matrix formulation has been under development for the microscopic description of the electromagnetic interactions of many-electron atomic systems in the presence of collisional and radiative decoherence and relaxation processes. A central objective is to develop a fundamental quantum-statistical formulation, in which bound-state and autoionization-resonance phenomena can be treated on an equal footing. An ultimate goal is to provide a comprehensive framework for a systematic and self-consistent treatment of non-equilibrium (possibly coherent) atomic-state kinetics and high-resolution (possibly overlapping) spectral-line shapes. This should enable a unified treatment for a broad class of atomic processes in laboratory and astrophysical plasmas covering extensive density and field regimes.

Jacobs, Verne L.

2009-06-01

8

Unified fluid/kinetic description of magnetized plasmas. Part 2, Applications.  

National Technical Information Service (NTIS)

The unified fluid/kinetic equations developed in part 1 of this work are used to study plasma drift type microinstabilities. A generalized perturbed Ohm's law derived which is uniformly valid for arbitrary collisionality (omega)/(nu) and adiabaticity (ome...

Z. Chang J. D. Callen

1991-01-01

9

Unified fluid/kinetic description of plasma microinstabilities. Part I: Basic equations in a sheared slab geometry  

SciTech Connect

Unified fluid/kinetic equations for the plasma perturbed density ({ital {tilde n}}), parallel flow velocity ({ital {tilde u}}{sub {parallel}}) and temperature ({ital {tilde T}}) are developed in a sheared slab geometry by calculating the fluid moment closure relations kinetically. At first, a set of (unclosed) nonlinear perturbed fluid equations for {ital {tilde n}}, {ital {tilde u}}{sub {parallel}} and {ital {tilde T}} is developed using a drift ordering analysis and a new gyroviscous force ((spec. char. missing){center dot}{Pi}{sub {ital g}}). Thereafter, to develop linear closure relations for {bold b}{center dot}{del}{center dot}{tilde {Pi}}{sub {parallel}} and {ital {tilde q}}{sub {parallel}}, a drift-kinetic version of a new Chapman--Enskog-like (CEL) equation is developed and solved by using a moment approach and a physically realistic collision operator (Lorentz scattering operator plus the momentum restoring terms). The resultant closure relations for {bold b}{center dot}(spec. char. missing){center dot}{tilde {Pi}}{sub {parallel}} and {ital {tilde q}}{sub {parallel}} unify the fluid and kinetic approaches. In the collisional fluid limit the equations reduce to the well-known Braginskii equations. In the adiabatic limit they reproduce the usual kinetic results, including Landau damping. It is shown that this new CEL approach is more compatible with a fluidlike description of plasmas than the usual drift/gyrokinetic approach. Remarkably simplified forms of the closure relations are presented. The results are compared with other Landau damping models and shown to be more accurate, complete, and physically realistic. Applications of this set of equations to various microinstabilities in tokamak plasmas are presented in a separate paper (Part II) (Phys. Fluids B {bold 4}, 1182 (1992)).

Chang, Z.; Callen, J.D. (Department of Nuclear Engineering and Engineering Physics, University of Wisconsin, Madison, Wisconsin 53706-1687 (United States))

1992-05-01

10

Plasma Kinetics  

NASA Astrophysics Data System (ADS)

In Chapter 7 of ISSI SR-001, Schwartz et al. [1998] explain the basic ideas of analysis by means of plasma kinetics: Liouville mapping and finite gyroradius effects. Liouville mapping can be used to relate features of distribution functions such as heating, anisotropies or beams, to the field variations. It is based on the conservation of phase space density along particle trajectories in collisionless plasmas, and therefore requires that particle trajectories (or at least their initial and final states) can be accurately approximated. This requirement generally relies on invariants of the particle motion such as the energy and adiabatic invariants and some knowledge of the electromagnetic fields along the trajectories. The large gyroradius of energetic ions has the consequence that ions detected at different directions are actually probing conditions at considerable distances around the space- craft. Density gradients then appear as gyrophase anisotropies in the angular distributions. This effect was first employed by Kaufmann and Konradi [1973] to probe the magnetopause. Section 7.5 of Schwartz et al. [1998] explain how it can be used to remotely sense sharp boundaries in ion densities. In particular, see Figures 7.4 and 7.6 in that chapter for a graphical demonstration. For a historical perspective on these topics, see also the classic paper by Northrop and Teller [1960] on the motion of charged particles in the Earth's magnetic field. In addition, Whipple et al. [1998] present an alternative framework that builds on the underlying concepts, while Whipple et al. [1986] describe extensions to the classic adiabatic theory that apply even in regions of strong gradients.

Daly, Patrick W.; Schwartz, Steven J.; Lefebvre, Betrand

11

Kinetic Description of the Impedance Probe  

NASA Astrophysics Data System (ADS)

Active plasma resonance spectroscopy is a well known diagnostic method. Many concepts of this method are theoretically investigated and realized as a diagnostic tool, one of which is the impedance probe (IP). The application of such a probe in plasmas with pressures of a few Pa raises the question whether kinetic effects have to be taken into account or not. To address this question a kinetic model is necessary. A general kinetic model for an electrostatic concept of active plasma spectroscopy was presented by R.P. Brinkmann [1] and can be used to describe the multipole resonance probe (MRP) [2]. In principle the IP is interpretable as a special case of the MRP in lower order. Thus, we are able to describe the IP by the kinetic model of the MRP. Based on this model we derive a solution to investigate the influence of kinetic effects to the resonance behavior of the IP.[4pt] [1] R.P. Brinkmann, Bulletin of the APS 54 no. 12, BM 4 (2009)[0pt] [2] M. Lapke et al., Appl. Phys. Lett. 93, 051502 (2008)

Oberrath, Jens; Lapke, Martin; Mussenbrock, Thomas; Brinkmann, Ralf Peter

2011-11-01

12

Kinetic Modeling of the Advanced Plasma Source  

NASA Astrophysics Data System (ADS)

Plasma ion assisted-deposition (PIAD) is a well-established technology for the creation of high quality coatings on mirrors, lenses, and other optical devices. This paper investigates the Advanced Plasma Source (APS), a plasma beam source employed for PIAD. A field enhanced glow discharge generates a radially expanding plasma flow with an ion energy of about 80 - 120,V. Charge exchange collions with the neutral background gas (pressure 0.1,a and below) produce a cold secondary plasma which expands as well. A hybrid model is developed which consists of a drift-kinetic description of the magnetized electrons, coupled to a simplified Boltzmann equation for the primary ions and fluid-dynamic representation of the secondary ions. All results compare well to experiments conducted at a commercial APS system.

Schroeder, Benjamin; Brinkmann, Ralf Peter; Harhausen, Jens; Ohl, Andreas

2011-11-01

13

Kinetic Profiles in NSTX Plasmas  

SciTech Connect

The National Spherical Torus Experiment (NSTX) is a low aspect ratio (R/a approximately 1.3) device with auxiliary heating from neutral-beam injection (NBI) and high-harmonic fast-wave heating (HHFW). Typical NSTX parameters are R(subscript ''0'') = 85 cm, a = 67 cm, I(subscript ''p'') = 0.7-1.4 MA, B(subscript ''phi'') = 0.25-0.45 T. Three co-directed deuterium neutral-beam sources have injected P(subscript ''NB'') less than or equal to 4.7 MW. HHFW plasmas typically have delivered P(subscript ''RF'') less than or equal to 3 MW. Important to the understanding of NSTX confinement are the new kinetic profile diagnostics: a multi-pulse Thomson scattering system (MPTS) and a charge-exchange recombination spectroscopy (CHERS) system. The MPTS diagnostic currently measures electron density and temperature profiles at 30 Hz at ten spatial locations. The CHERS system has recently become available to measure carbon ion temperature and toroidal flow at 17 radial positions spanning the outer half of the minor radius with 20 msec time resolution during NBI. Experiments conducted during the last year have produced a wide range of kinetic profiles in NSTX. Some interesting examples are presented below.

R.E. Bell; B.P. LeBlanc; C. Bourdelle; D.R. Ernst; E.D. Fredrickson; D.A. Gates; J.C. Hosea; D.W. Johnson; S.M. Kaye; R. Maingi; S. Medley; J.E. Menard; D. Mueller; M. Ono; F. Paoletti; M. Peng; S.A. Sabbagh; D. Stutman; D.W. Swain; E.J. Synakowski; and J.R. Wilson

2001-07-10

14

Kinetic equation for spin-polarized plasmas  

SciTech Connect

The usual kinetic description of a plasma is extended to include variables to describe the spin. The distribution function, over phase-space and the new spin variables, provides a sufficient description of a spin-polarized plasma. The evolution equation for the distribution function is given. The equations derived are used to calculate depolarization due to four processes, inhomogeneous fields, collisions, collisions in inhomogeneous fields, and waves. It is found that depolarization by field inhomogeneity on scales large compared with the gyroradius is totally negligible. The same is true for collisional depolarization. Collisions in inhomogeneous fields yield a depolarization rate of order 10/sup -4/S/sup -1/ for deuterons and a negligible rate for tritons in a typical fusion reactor design. This is still sufficiently small on reactor time scales. However, small amplitude magnetic fluctuations (of order one gauss) resonant with the spin precession frequency can lead to significant depolarization (depolarises triton in ten seconds and deuteron in a hundred seconds.)

Cowley, S.C.; Kulsrud, R.M.; Valeo, E.

1984-07-01

15

Computer models for kinetic equations of magnetically confined plasmas  

SciTech Connect

This paper presents four working computer models developed by the computational physics group of the National Magnetic Fusion Energy Computer Center. All of the models employ a kinetic description of plasma species. Three of the models are collisional, i.e., they include the solution of the Fokker-Planck equation in velocity space. The fourth model is collisionless and treats the plasma ions by a fully three-dimensional particle-in-cell method.

Killeen, J.; Kerbel, G.D.; McCoy, M.G.; Mirin, A.A.; Horowitz, E.J.; Shumaker, D.E.

1987-01-01

16

Kinetic theory of plasma waves, homogeneous plasmas  

Microsoft Academic Search

The linear theory of plasma waves in homogeneous plasma is arguably the most mature and best understood branch of plasma physics. Given the recently revised version of Stix's excellent Waves in Plasmas (1992), one might ask whether another book on this subject is necessary only a few years later. The answer lies in the scope of this volume; it is

Miklos Porkolab

1998-01-01

17

Kinetic Modeling of Complex Plasma Equipment  

Microsoft Academic Search

Kinetics of electrons, ions and neutrals play an important role in industrial plasma systems. These systems are often characterized by complex geometries and require 2D and 3D models of varying resolution for realistic simulations of relevant processes. We will describe hybrid approach to modeling such systems using kinetic models for electrons and hydrodynamic (fluid) models for ion and neutral components.

Vladimir Kolobov

2009-01-01

18

A self-consistent kinetic plasma model with rapid convergence  

SciTech Connect

Algorithms for very efficient solution of kinetic equations have previously been developed and used to obtain a self-consistent kinetic description of electrons and ions in various plasmas, including RF glow discharges. Since RF discharge calculations may take many thousands of cycles to converge, a solution which follows the time evolution throughout this process is inevitably computationally costly. The authors have implemented a scaleup procedure which obviates the need to follow the entire time evolution in this or other plasma models. by running the full calculation for a short time, the authors extract information which permits an extrapolation of the time evolution over a very long time, or a scaleup. In this paper a detailed description of the basis for the scaleup is given, as well as an example of the use of a scaleup procedure, as applied to a moderately high-pressure RF discharge in helium.

Hitchon, W.N.G. (Wisconsin Univ., Madison, WI (United States). Dept. of Electrical and Computer Engineering); Sommerer, T.J. (Illinois Univ., Urbana, IL (United States). Dept. of Electrical and Computer Engineering); Lawler, J.E. (Wisconsin Univ., Madison, WI (United States). Dept. of Physics)

1991-04-01

19

Wave kinetics of relativistic quantum plasmas  

SciTech Connect

A quantum kinetic equation, valid for relativistic unmagnetized plasmas, is derived here. This equation describes the evolution of a quantum quasi-distribution, which is the Wigner function for relativistic spinless charged particles in a plasma, and it is exactly equivalent to a Klein-Gordon equation. Our quantum kinetic equation reduces to the Vlasov equation in the classical limit, where the Wigner function is replaced by a classical distribution function. An approximate form of the quantum kinetic equation is also derived, which includes first order quantum corrections. This is applied to electron plasma waves, for which a new dispersion relation is obtained. It is shown that quantum recoil effects contribute to the electron Landau damping with a third order derivative term. The case of high frequency electromagnetic waves is also considered. Its dispersion relation is shown to be insensitive to quantum recoil effects for equilibrium plasma distributions.

Mendonca, J. T. [IPFN, Instituto Superior Tecnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)

2011-06-15

20

Kinetic description of the far regions of the 3d tails\\/streamers formed by coupling of the external maxwellian plasma flows with magnetic dipole and toroid at active region  

Microsoft Academic Search

We consider in terms of the Vlasov Maxwell kinetic approach a classical problem of inductive generation by the solar wind flow of the 3D solar streamer tail structures originating by magnetic flux sources at the Sun magnetoactive regions The input flow is a hot collisionless plasma with maxwellian distribution function We separated magnetic field interacting particles on trapped and untrapped

V. M. Gubchenko; H. K. Biernat; H. O. Rucker

2006-01-01

21

A kinetic description of antifreeze glycoprotein activity.  

PubMed

The antifreeze glycoproteins (AFGP) of polar fish have the ability to depress the freezing temperature of water approximately 500 times the amount expected based on the number of AFGP molecules in solution; yet AFGP solutions have a purely colligative melting point depression. The difference of solution melting and freezing temperatures is the antifreeze activity of AFGP. One characteristic of AFGP activity that requires further examination is the effect of concentration on antifreeze activity, especially whether the activity saturates at high concentrations or the measured activity increases ad infinitum. This study first surveys the activity of the various antifreeze components from both Pagothenia borchgrevinki and the Arg-containing antifreeze glycoprotein from Eleginus gracilis (EgAF). It was found that all AFGP components examined have a plateau in activity at high concentration, but the actual value of the plateau activity differs between the different length AFGP components and between AFGP and EgAF. While the low molecular weight components of both AFGP and EgAF lose activity at deep supercooling, at high concentration activity is restored. The activity data is then shown to fit a reversible kinetic model of AFGP activity, and the coefficients obtained are used to compare the activity differences between AFGP components and between AFGP and EgAF. The model is also shown to describe the activity of the antifreeze protein of the fish Pseudopleuronectes americanus and the thermal hysteresis protein of the insect, Tenebrio molitor. PMID:3700396

Burcham, T S; Osuga, D T; Yeh, Y; Feeney, R E

1986-05-15

22

Relativistic (covariant) kinetic theory of linear plasma waves and instabilities  

SciTech Connect

The fundamental kinetic description is of vital importance in high-energy astrophysics and fusion plasmas where wave phenomena evolve on scales small comparing with binary collision scales. A rigorous relativistic analysis is required even for nonrelativistic plasma temperatures for which the classical theory yielded unphysical results: e.g. collisonless damping of superluminal waves (phase velocity exceeds the speed of light). The existing nonrelativistic approaches are now improved by covariantly correct dispersion theory. As an important application, the Weibel instability has been recently investigated and confirmed as the source of primordial magnetic field in the intergalactic medium.

Lazar, M. [Institut fuer Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); 'Alexandru Ioan Cuza' University, Faculty of Physics, 6600 Iasi (Romania); Schlickeiser, R. [Institut fuer Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany); Centre for Plasma Science and Astrophysics, Ruhr-University, D-44780 Bochum (Germany)

2006-06-19

23

Nonlinear modeling of kinetic plasma instabilities  

NASA Astrophysics Data System (ADS)

Many kinetic plasma instabilities, in quite different physical systems, share a genuinely similar mathematical structure near isolated phase-space islands. For this reason, dynamical features such as faster-than-exponential growth of the instability, as well as nonlinear frequency sweeping, are found to be universal. Numerical ?f methods, which follow the evolution of the (nonlinear) perturbed distribution function along single-particle orbits, have been applied to analytic models, which include a continuous particle source, resonant particle collisions, and wave damping. The result is a series of codes that can reliably model the nonlinear evolution of kinetic instabilities, including some specific to tokamak plasmas, over experimentally relevant time scales. New results include (i) nonlinear simulations of two-species, one-degree-of-freedom plasmas; (ii) simulations of fishbone bursts in tokamak plasmas; (iii) nonlinear modeling of beam-driven toroidal Alfvén eigenmode activity in tokamaks.

Candy, J.; Berk, H. L.; Breizman, B. N.; Porcelli, F.

1999-05-01

24

Kinetic coefficients for quark-antiquark plasma.  

National Technical Information Service (NTIS)

The quark-antiquark plasma near equilibrium is studied. The results are based on the Heinz kinetic equations with the Boltzmann collision operator approximated by a relaxation term with the relaxation time, tau, treated as a small parameter. Linear in tau...

W. Czyz W. Florkowski

1986-01-01

25

BOOK REVIEW: Plasma Kinetics in Atmospheric Gases  

Microsoft Academic Search

The book Plasma Kinetics in Atmospheric Gases is a worthwhile contribution to the basic phenomena in nitrogen, oxygen and other atmospheric gases. It contains basic introductory chapters on relaxation in translational, rotational (short) and vibrational (extensive) distribution and on the physics of electron excitation and electron distribution functions. In the latter, electron beam excitation (i.e. high electron energies) are included.

M. Capitelli; C. M. Ferreira; B. F. Gordiets; A. I. Osipov

2001-01-01

26

Kinetic modelling of dusty plasmas  

NASA Astrophysics Data System (ADS)

Formation of dust structures in a capacitively coupled RF discharge was studied with a self-consistent particle simulation. For this purpose 3D Particle-in-Cell code with Monte Carlo collisions (PIC MCC), resolving also the sheath in front of the wall including all relevant species (neutrals, ions, electrons) and their reactions was developed and applied. In the simulation dust particles trapped in the sheath over the lower electrode form vertical strings, in which negative particles are attracted due to polarization of the ion flow (wake-field effect). A quasi 2 dimensional (simple hexagonal) structure is formed by the dust in which flat layers with hexagonal symmetry are vertically aligned due to the unidirectional ion background flow towards the electrode in the sheath. Particle-Particle/Particle-Mesh (P3M) algorithm was introduced into the model in order to accurately resolve the close-range interaction between the dust grains and plasma particles. Charging of the dust grains due to absorption of plasma particles was studied self-consistently with this model.

Matyash, K.; Schneider, R.; Kersten, H.

2005-01-01

27

Kinetic Alfvén waves in preflare plasma  

NASA Astrophysics Data System (ADS)

Low-frequency instabilities of plasma waves in the arch structures in solar active regions have been investigated before a flare. In the framework of mechanism of "direct initiation" of instability by slowly increasing (quasi-static) large-scale electric field in a loop the dispersion relation has been studied for the perturbations which propagate almost perpendicularly to the magnetic field of the loop. The case has been considered, when amplitude of weak ("subdreicer") electric field sharply increases before a flare, low-frequency instability develops on the background of ion-acoustic turbulence and thickness of this turbulent plasma layer plays the role of mean characteristic scale of inhomogeneity of plasma density. If the values of the main plasma parameters, i.e. temperature, density, magnetic field amplitude allow to neglect the influence of the shear of magnetic strength lines on the instability development , then two types of the waves can be generated in preflare plasma: the kinetic Alfvén waves and some new kind of the waves from the range of slowly magneto-acoustic ones. Instability of kinetic Alfvén waves has clearly expressed threshold character with respect to the amplitude of "subdreicer" electric field. This fact seems to be useful for the short-time prediction of a flare in arch structure.

Kryshtal, A. N.; Gerasimenko, S. V.

2005-01-01

28

Fundamental Statistical Descriptions of Plasma Turbulence in Magnetic Fields  

SciTech Connect

A pedagogical review of the historical development and current status (as of early 2000) of systematic statistical theories of plasma turbulence is undertaken. Emphasis is on conceptual foundations and methodology, not practical applications. Particular attention is paid to equations and formalism appropriate to strongly magnetized, fully ionized plasmas. Extensive reference to the literature on neutral-fluid turbulence is made, but the unique properties and problems of plasmas are emphasized throughout. Discussions are given of quasilinear theory, weak-turbulence theory, resonance-broadening theory, and the clump algorithm. Those are developed independently, then shown to be special cases of the direct-interaction approximation (DIA), which provides a central focus for the article. Various methods of renormalized perturbation theory are described, then unified with the aid of the generating-functional formalism of Martin, Siggia, and Rose. A general expression for the renormalized dielectric function is deduced and discussed in detail. Modern approaches such as decimation and PDF methods are described. Derivations of DIA-based Markovian closures are discussed. The eddy-damped quasinormal Markovian closure is shown to be nonrealizable in the presence of waves, and a new realizable Markovian closure is presented. The test-field model and a realizable modification thereof are also summarized. Numerical solutions of various closures for some plasma-physics paradigms are reviewed. The variational approach to bounds on transport is developed. Miscellaneous topics include Onsager symmetries for turbulence, the interpretation of entropy balances for both kinetic and fluid descriptions, self-organized criticality, statistical interactions between disparate scales, and the roles of both mean and random shear. Appendices are provided on Fourier transform conventions, dimensional and scaling analysis, the derivations of nonlinear gyrokinetic and gyrofluid equations, stochasticity criteria for quasilinear theory, formal aspects of resonance-broadening theory, Novikov's theorem, the treatment of weak inhomogeneity, the derivation of the Vlasov weak-turbulence wave kinetic equation from a fully renormalized description, some features of a code for solving the direct-interaction approximation and related Markovian closures, the details of the solution of the EDQNM closure for a solvable three-wave model, and the notation used in the article.

John A. Krommes

2001-02-16

29

Kinetic description of the far regions of the 3d tails/streamers formed by coupling of the external maxwellian plasma flows with magnetic dipole and toroid at active region  

NASA Astrophysics Data System (ADS)

We consider in terms of the Vlasov Maxwell kinetic approach a classical problem of inductive generation by the solar wind flow of the 3D solar streamer tail structures originating by magnetic flux sources at the Sun magnetoactive regions The input flow is a hot collisionless plasma with maxwellian distribution function We separated magnetic field interacting particles on trapped and untrapped fly by particles Trapped particles partly are parameterized by magnetic flux source configuration The source is approximated by densities of magnetic dipole and magnetic toroid currents distributed on the characteristic scale and characterized by ratio of their integral currents Fly by particles motion we treat via perturbations resulting a linear analytical approach to the flowing plasma Plasma appeared as a result in the problem like resistive and diamagnetic media Non local resistive currents are characterized by anomalous skin scale and diamagnetic currents by magnetic Debye scale Ratio of the diamagnetic currents to the resistive currents is a Quality of the streamer magnetosphere We get integral representation of a selfconsistent global 3D magnetic configuration which is defined via two different kinds of cylindrical harmonics For maxwellian plasma we get a low Quality regime when 3D structure is with resistive currents and only parameter is a specific collisionless magnetic Reynolds number A dipole generates 3D two wire multi magnetic ropes current configuration cylindrical dipole harmonics which is observed in the far down tail

Gubchenko, V. M.; Biernat, H. K.; Rucker, H. O.

30

The model of macroscopic kinetics in non-equilibrium plasma chemical reactions. I - General considerations and basic relations  

Microsoft Academic Search

The reaction of a chemical active nonequilibrium plasma system is studied within simple kinetic models in principle. Of special interest are steady states of the system with the meaning of a reversible chemical equilibrium. Starting from a schematized description of the nonisothermal plasma chemical reactor the basic relations of the so-called macroscopic kinetics are developed and in the case of

A. Rutscher; H. E. Wagner

1985-01-01

31

Kinetic Modeling of Complex Plasma Equipment  

NASA Astrophysics Data System (ADS)

Kinetics of electrons, ions and neutrals play an important role in industrial plasma systems. These systems are often characterized by complex geometries and require 2D and 3D models of varying resolution for realistic simulations of relevant processes. We will describe hybrid approach to modeling such systems using kinetic models for electrons and hydrodynamic (fluid) models for ion and neutral components. Kinetic modeling of electrons involves numerical solution of the Boltzmann equation or its derivatives. Using two-term spherical harmonics expansion in velocity space, the 6D Boltzmann equation can be reduced to a 4D Fokker-Plank (F-P) equation for the Electron Energy Distribution Function (EEDF), which depends of electron energy and spatial position. This equation can be conveniently solved using total electron energy (kinetic + potential) for a wide range of discharge conditions. Further simplifications are possible in the two extremes. At high gas pressures one can solve local F-P equation for the EEDF as a function of local electric field and plasma composition, and generate Look-Up-Tables (LUTs) for electron transport coefficients and rates of electron induced chemical reactions to be used in fluid models for electrons. The other extreme corresponds to a ``nonlocal approach'' where the EEDF depend solely on the total energy and does to depend explicitly on spatial position. We will describe the architecture of the F-P solver for electrons in the CFD-ACE+ software package and its application to simulations of low-pressure ICP, CCP, and DC discharges, as well as high-pressure micro-plasmas. The peculiarities of the EEDF formation in these systems, and the importance of nonlocal kinetic effects for the formation of striations, electron heating and macro-plasma parameters will be discussed. We will also discuss the limitations of the F-P approach and our current efforts to develop a full Boltzmann solver for simulations of fast (runaway) electrons and nonlocal electromagnetic phenomena in low-pressure RF discharges.

Kolobov, Vladimir

2009-10-01

32

Kinetic stress and intrinsic flow in a toroidal plasma.  

PubMed

A new mechanism for intrinsic plasma flow has been experimentally identified in a toroidal plasma. For reversed field pinch plasmas with a few percent ? (ratio of plasma pressure to magnetic pressure), measurements show that parallel pressure fluctuations correlated with magnetic fluctuations create a kinetic stress that can affect momentum balance and the evolution of intrinsic plasma flow. This implies kinetic effects are important for flow generation and sustainment. PMID:23432267

Ding, W X; Lin, L; Brower, D L; Almagri, A F; Chapman, B E; Fiksel, G; Den Hartog, D J; Sarff, J S

2013-02-08

33

Nonlinear Modeling of Kinetic Plasma Instabilities  

NASA Astrophysics Data System (ADS)

There is a wide variety of plasma problems for which instability arises due to the release of free energy from an inverted population of energetic particles. Understanding the long--time nonlinear dynamics of these instabilities remains a daunting theoretical challenge. The presence of multiple disparate timescales makes a brute--force numerical simulation for many inverse growth times unrealistic if at all possible. For this reason, simulations are often performed for only a relatively short time. These may entirely miss long--time features of the instability observed in experiments. We show that many seemingly unrelated kinetic plasma instabilities share a genuinely similar mathematical structure near isolated phase--space islands. For this reason, dynamical features such as faster--than--exponential growth of the instability, as well as nonlinear frequency chirping, are found to be truly universal. Novel numerical methods have been applied to analytic models which include a continuous particle source, resonant particle collisions, and wave damping. The result is a series of ? f codes(J. Candy, J. Comput. Phys. 129,) 160 (1996). which can reliably model the nonlinear evolution of kinetic instabilities over experimentally relevant timescales (??>> 1). In the case of the bump--on--tail instability, we have made a great deal of progress in understanding collisionless nonlinear frequency sweeping, and more recently we have examined the case of two kinetic species (one stable, one unstable) for which both drive and damping can be nonlinear.(H.L. Berk, B.N. Breizman, J. Candy, N.V. Petviashvili, in preparation; H.L. Berk, B.N. Breizman, and M.S. Pekker, Plasma Phys. Rep. 23), 842 (1997). As well, we have developed a toroidal TAE--beam code to simulate TAE--induced beam--ion losses in TFTR plasmas. This code, which can treat many TAE modes simultaneously, shows that nonlinear (2nd and higher order) islands may be of critical importance for understanding losses due to TAE bursts. Finally, a new operator technique(B.N. Breizman, J. Candy, F. Porcelli, and H.L. Berk, Phys. Plasmas 5), 2326 (1998). has been developed to enable the nonlinear modelling of fishbone modes. We have reproduced the strong nonlinear frequency downshift of precessional modes, as well as an explosive regime in diamagnetic modes predicted by nonlinear theory.(J. Candy, H.L. Berk, B.N. Breizman, and F. Porcelli, in preparation; J. Candy, F. Porcelli, B.N. Breizman, and H.L. Berk, Proc. 24th EPS Conf. Berchtesgaden, Vol. 21A III, 1189 (1997).)

Candy, J.

1998-11-01

34

BOOK REVIEW: Kinetic theory of plasma waves, homogeneous plasmas  

NASA Astrophysics Data System (ADS)

The linear theory of plasma waves in homogeneous plasma is arguably the most mature and best understood branch of plasma physics. Given the recently revised version of Stix's excellent Waves in Plasmas (1992), one might ask whether another book on this subject is necessary only a few years later. The answer lies in the scope of this volume; it is somewhat more detailed in certain topics than, and complementary in many fusion research relevant areas to, Stix's book. (I am restricting these comments to the homogeneous plasma theory only, since the author promises a second volume on wave propagation in inhomogeneous plasmas.) This book is also much more of a theorist's approach to waves in plasmas, with the aim of developing the subject within the logical framework of kinetic theory. This may indeed be pleasing to the expert and to the specialist, but may be too difficult to the graduate student as an `introduction' to the subject (which the author explicitly states in the Preface). On the other hand, it may be entirely appropriate for a second course on plasma waves, after the student has mastered fluid theory and an introductory kinetic treatment of waves in a hot magnetized `Vlasov' plasma. For teaching purposes, my personal preference is to review the cold plasma wave treatment using the unified Stix formalism and notation (which the author wisely adopts in the present book, but only in Chapter 5). Such an approach allows one to deal with CMA diagrams early on, as well as to provide a framework to discuss electromagnetic wave propagation and accessibility in inhomogeneous plasmas (for which the cold plasma wave treatment is perfectly adequate). Such an approach does lack some of the rigour, however, that the author achieves with the present approach. As the author correctly shows, the fluid theory treatment of waves follows logically from kinetic theory in the cold plasma limit. I only question the pedagogical value of this approach. Otherwise, I welcome this addition to the literature, for it gives the teacher of the subject a valuable reference where the inquisitive student will be able to read up on and satisfy himself about the practicality and reliability of the Vlasov theory in a hot magnetized and collisionless plasma. The book has excellent treatments of several new topics not included in previous textbooks, for example, the relativistic theory of plasma wave propagation, so important in electron cyclotron heating of magnetically confined fusion plasmas, a discussion of current drive theory and there is a welcome introduction to parametric instabilities in the final chapter. There are some things that make the readability of the book somewhat difficult. In the early parts, certain advanced concepts are introduced without much motivation or explanation, although the author is trying to be helpful by providing a list of relevant references at the end of each chapter. Here the teacher's role will be critical. Again, a certain amount of previous knowledge of the subject would prove to be invaluable to the student. The main content of the book is included in 11 chapters. Use is made of CGS Gaussian units, a favourite of plasma theorists. As the author states, these are still widely used in advanced plasma theory, and the student is well advised to become familiar with this system of units (as well as the SI system for applications). To help the reader in the Introduction, the author defines various expressions often used in plasma physics in practical units (frequencies in hertz, lengths in centimetres, temperatures in kiloelectronvolts and magnetic fields in teslas). Chapter 2 is entitled `Plasma Electrodynamics' and it introduces the Maxwell-Vlasov set of equations, as well as the important fundamentals of wave propagation, such as polarization, dispersion and the dielectric tensor, and energy relations. In Chapter 3, `Elementary Plasma Kinetic Theory', the author derives the Vlasov equation and the Fokker-Planck equation from the BBGKY hierarchy. This is a somewhat unusual chapter in a book on plasma waves, but I

Porkolab, Miklos

1998-11-01

35

Kinetic simulation of open beam-plasma systems  

SciTech Connect

Kinetic simulation of open plasma systems is considered within the Maxwell and Vlasov-Fokker-Planck equations (MVFP). Two approaches to the discrete simulation of open beam-plasma systems are described. 16 refs., 5 figs.

Batishchev, O.V.; Karas, V.I.; Levchenko, V.D. [Keldysh Institute of Applied Mathematics, Moscow (Russian Federation)] [and others

1994-07-01

36

Kinetic theory of partially ionized complex (dusty) plasmas  

SciTech Connect

The general approach to the kinetic theory of complex (dusty) plasmas [Tsytovich and de Angelis, Phys. Plasmas 6, 1093 (1999)], which was formulated with the assumption of a regular (nonfluctuating) source of plasma particles, is reformulated to include ionization by electron impact on neutrals as the plasma source and the effects of collisions of ions and dust particles with neutrals.

Tsytovich, V.N.; De Angelis, U.; Ivlev, A.V.; Morfill, G.E. [General Physics Institute, Russian Academy of Sciences, 117942 Moscow (Russian Federation); Department of Physical Sciences, University of Naples 'Federico II', 80126 Naples (Italy); Max-Planck-Institut fuer Extraterrestrische Physik, D-85741 Garching (Germany)

2005-08-15

37

Detailed and reduced chemical-kinetic descriptions for hydrocarbon combustion  

NASA Astrophysics Data System (ADS)

Numerical and theoretical studies of autoignition processes of fuels such as propane are in need of realistic simplified chemical-kinetic descriptions that retain the essential features of the detailed descriptions. These descriptions should be computationally feasible and cost-effective. Such descriptions are useful for investigating ignition processes that occur, for example, in homogeneous-charge compression-ignition engines, for studying the structures and dynamics of detonations and in fields such as multi-dimensional Computational Fluid Dynamics (CFD). Reduced chemistry has previously been developed successfully for a number of other hydrocarbon fuels, however, propane has not been considered in this manner. This work focuses on the fuels of propane, as well propene, allene and propyne, for several reasons. The ignition properties of propane resemble those of other higher hydrocarbons but are different from those of the lower hydrocarbons (e.g. ethylene and acetylene). Propane, therefore, may be the smallest hydrocarbon that is representative of higher hydrocarbons in ignition and detonation processes. Since the overall activation energy and ignition times for propane are similar to those of other higher hydrocarbons, including liquid fuels that are suitable for many applications, propane has been used as a model fuel for several numerical and experimental studies. The reason for studying elementary chemistry of propene and C3H4 (allene or propyne) is that during the combustion process, propane breaks down to propene and C3H4 before proceeding to products. Similarly, propene combustion includes C3H4 chemistry. In studying propane combustion, it is therefore necessary to understand the underlying combustion chemistry of propene as well as C3H 4. The first part of this thesis focuses on obtaining and testing a detailed chemical-kinetic description for autoignition of propane, propene and C 3H4, by comparing predictions obtained with this detailed mechanism against numerous experimental data available from shock-tube studies and flame-speed measurements. To keep the detailed mechanism small, attention is restricted to pressures below about 100 atm, temperatures above about 1000 K and equivalence ratios less than about 3. Based on this detailed chemistry description, short (or skeletal) mechanisms are then obtained for each of the three fuels by eliminating reactions that are unimportant for the autoignition process under conditions presented above. This was achieved by utilizing tools such as sensitivity and reaction pathway analyses. Two distinct methodologies were then used in order to obtain a reduced mechanism for autoignition from the short mechanisms. A Systematic Reduction approach is first taken that involves introducing steady-state approximations to as many species as analytically possible. To avoid resorting to numerical methods, the analysis for obtaining ignition times for heptane, presented by Peters and co-workers is followed in order to obtain a rough estimate for an expression of propane ignition time. The results from this expression are then compared to the ignition times obtained computationally with the detailed mechanism. The second method is an Empirical Approach in which chemistry is not derived formally, but rather postulated empirically on the basis of experimental, computational and theoretical observations. As a result, generalized reduced mechanisms are proposed for autoignition of propane, propene and C3H 4. Expressions for ignition times obtained via this empirical approach are compared to the computational results obtained from the detailed mechanism.

Petrova, Maria V.

38

Comet giacobini-zinner: plasma description.  

PubMed

A strong interaction between the solar wind and comet Giacobini-Zinner was observed oh 11 September 1985 with the Los Alamos plasma electron experiment on the International Cometary Explorer (ICE) spacecraft. As ICE approached an intercept point 7800 kilometers behind the nucleus from the south and receded to the north, upstream phenomena due to the comet were observed. Periods of enhanced electron heat flux from the comet as well as almost continuous electron density fluctuations were measured. These effects are related to the strong electron heating observed in the cometary interaction region and to cometary ion pickup by the solar wind, respectively. No evidence for a conventional bow shock was found as ICE entered and exited the regions of strongest interaction of the solar wind with the cometary environment. The outer extent of this strong interaction zone was a transition region in which the solar wind plasma was heated, compressed, and slowed. Inside the inner boundary of the transition region was a sheath that enclosed a cold intermediate coma. In the transition region and sheath, small-scale enhancements in density were observed. These density spikes may be due to an instability associated with cometary ion pickup or to the passage of ICE through cometary ray structures. In the center of the cold intermediate coma a narrow, high-density core of plasma, presumably the developing plasma tail was found. In some ways this tail can be compared to the plasma sheet in Earth's magnetotail and to the current sheet in the tail at Venus. This type of configuration is expected in the double-lobe magnetic topology detected at the comet, possibly caused by the theoretically expected draping of the interplanetary magnetic field around its ionosphere. PMID:17792144

Bame, S J; Anderson, R C; Asbridge, J R; Baker, D N; Feldman, W C; Fuselier, S A; Gosling, J T; McComas, D J; Thomsen, M F; Young, D T; Zwickl, R D

1986-04-18

39

Ducted kinetic Alfven waves in plasma with steep density gradients  

SciTech Connect

Given their high plasma density (n {approx} 10{sup 13} cm{sup -3}), it is theoretically possible to excite Alfven waves in a conventional, moderate length (L {approx} 2 m) helicon plasma source. However, helicon plasmas are decidedly inhomogeneous, having a steep radial density gradient, and typically have a significant background neutral pressure. The inhomogeneity introduces regions of kinetic and inertial Alfven wave propagation. Ion-neutral and electron-neutral collisions alter the Alfven wave dispersion characteristics. Here, we present the measurements of propagating kinetic Alfven waves in helium helicon plasma. The measured wave dispersion is well fit with a kinetic model that includes the effects of ion-neutral damping and that assumes the high density plasma core defines the radial extent of the wave propagation region. The measured wave amplitude versus plasma radius is consistent with the pile up of wave magnetic energy at the boundary between the kinetic and inertial regime regions.

Houshmandyar, Saeid [Solar Observatory Department, Prairie View A and M University, Prairie View, Texas 77446 (United States); Department of Physics, West Virginia University, Morgantown, West Virginia 26506-6315 (United States); Scime, Earl E. [Department of Physics, West Virginia University, Morgantown, West Virginia 26506-6315 (United States)

2011-11-15

40

Parametric instabilities of Alfven waves in a multispecies plasma: Kinetic effects  

SciTech Connect

Parametric instabilities of a circularly polarized Alfven wave in a multispecies magnetized plasma are considered. An analytic kinetic description and hybrid simulations for the linear behavior of the instabilities are given. It is found that, even for low-{beta} regimes, both the kinetic effects and the presence of heavy ions substantially modify the characteristics of parametric instabilities as compared to the fluid model. The decay instability can be severely quenched in a plasma composed of massless electrons, protons, and alpha particles when the alphas are slightly hotter than the protons. These results could be important in describing the heating processes of heavy ions in the solar corona.

Kauffmann, K.; Araneda, J. A. [Departamento de Fisica, Facultad de Ciencias Fisicas y Matematicas, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile)

2008-06-15

41

On the kinetic Alfvén waves in nonrelativistic spin quantum plasmas  

NASA Astrophysics Data System (ADS)

We have studied the effect of electron spin on the kinetic Alfvén waves in the presence of uniform static magnetic field in an electron-ion plasma. We deduce that the usual kinetic Alfvén waves are modified via spin quantum effects of electrons. The dimensionless parameters that determine the relative importance of the electron spin become prominent at higher densities. It is found that the kinetic Alfvén wave frequency decreases due to the electron spin contribution in the kinetic limit while in the inertial limit they are almost unaffected in a hot magnetized plasma.

Hussain, A.; Iqbal, Z.; Brodin, G.; Murtaza, G.

2013-11-01

42

Fully implicit kinetic modelling of collisional plasmas  

SciTech Connect

This dissertation describes a numerical technique, Matrix-Free Newton Krylov, for solving a simplified Vlasov-Fokker-Planck equation. This method is both deterministic and fully implicit, and may not have been a viable option before current developments in numerical methods. Results are presented that indicate the efficiency of the Matrix-Free Newton Krylov method for these fully-coupled, nonlinear integro-differential equations. The use and requirement for advanced differencing is also shown. To this end, implementations of Chang-Cooper differencing and flux limited Quadratic Upstream Interpolation for Convective Kinematics (QUICK) are presented. Results are given for a fully kinetic ion-electron problem with a self consistent electric field calculated from the ion and electron distribution functions. This numerical method, including advanced differencing, provides accurate solutions, which quickly converge on workstation class machines. It is demonstrated that efficient steady-state solutions can be achieved to the non-linear integro-differential equation, obtaining quadratic convergence, without incurring the large memory requirements of an integral operator. Model problems are presented which simulate plasma impinging on a plate with both high and low neutral particle recycling typical of a divertor in a Tokamak device. These model problems demonstrate the performance of the new solution method.

Mousseau, V.A.

1996-05-01

43

Supergravity description of boost invariant conformal plasma at strong coupling  

SciTech Connect

We study string theory duals of the expanding boost invariant conformal gauge theory plasmas at strong coupling. The dual supergravity background is constructed as an asymptotic late-time expansion, corresponding to equilibration of the gauge theory plasma. The absence of curvature singularities in the first few orders of the late-time expansion of the dual gravitational background unambiguously determines the equilibrium equation of state, and the shear viscosity of the gauge theory plasma. While the absence of the leading pole singularities in the gravitational curvature invariants at third order in late-time expansion determines the relaxation time of the plasma, the subleading logarithmic singularity cannot be canceled within a supergravity approximation. Thus, a supergravity approximation to a dual description of the strongly coupled boost invariant expanding plasma is inconsistent. Nevertheless we find that the relaxation time determined from the cancellation of pole singularities is quite robust.

Benincasa, Paolo [Department of Applied Mathematics, University of Western Ontario, London, Ontario N6A 5B7 (Canada); Buchel, Alex [Department of Applied Mathematics, University of Western Ontario, London, Ontario N6A 5B7 (Canada); Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2J 2W9 (Canada); Heller, Michal P.; Janik, Romuald A. [Institute of Physics, Jagellonian University, Reymonta 4, 30-059 Cracow (Poland)

2008-02-15

44

Kinetic instability of ion acoustic mode in permeating plasmas  

SciTech Connect

In plasmas with electron drift (current) relative to static ions, the ion acoustic wave is subject to the kinetic instability which takes place if the directed electron speed exceeds the ion acoustic speed. The instability threshold becomes different in the case of one quasineutral electron-ion plasma propagating through another static quasineutral (target) plasma. The threshold velocity of the propagating plasma may be well below the ion acoustic speed of the static plasma. Such a currentless instability may frequently be expected in space and astrophysical plasmas.

Vranjes, J.; Poedts, S. [Center for Plasma Astrophysics and Leuven Mathematical Modeling and Computational Science Center (LMCC), K. U. Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium); Ehsan, Zahida [Salam Chair in Department of Physics, GC University, Lahore 54000, Pakistan and Plasma Physics Group, Blackett Laboratory, Imperial College, London SW7 2AZ (United Kingdom)

2009-07-15

45

Kinetic Signatures and Intermittent Turbulence in the Solar Wind Plasma  

NASA Astrophysics Data System (ADS)

A connection between kinetic processes and intermittent turbulence is observed in the solar wind plasma using measurements from the Wind spacecraft at 1 A.U. In particular, kinetic effects such as temperature anisotropy and plasma heating are concentrated near coherent structures, such as current sheets, which are nonuniformly distributed in space. Furthermore, these coherent structures are preferentially found in plasma unstable to the mirror and firehose instabilities. The inhomogeneous heating in these regions, which is present in both the magnetic field parallel and perpendicular temperature components, results in protons at least 3-4 times hotter than under typical stable plasma conditions. These results offer a new understanding of kinetic processes in a turbulent regime, where linear Vlasov theory is not sufficient to explain the inhomogeneous plasma dynamics operating near non-Gaussian structures.

Osman, K. T.; Matthaeus, W. H.; Hnat, B.; Chapman, S. C.

2012-06-01

46

Fluctuation approach to description of nonideal plasma. II: Collisional recombination in nonequilibrium plasma  

SciTech Connect

A model capable of describing the kinetics of collisional recombination in nonideal plasmas by the methods of molecular dynamics is developed. The dependence of the collisional recombination rate on the coupling parameter is found to differ substantially from the extrapolation of the three-body recombination rate in nonideal plasmas. A sharp decrease in the recombination rate in strongly nonideal plasmas is revealed. As the coupling parameter decreases, collisional recombination transforms into three-body recombination.

Lankin, A. V.; Norman, G. E. [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

2010-12-15

47

Good relationship between saliva cotinine kinetics and plasma cotinine kinetics after smoking one cigarette.  

PubMed

This study investigated the relationship between plasma and saliva cotinine kinetics after smoking one cigarette and the relationship between cotinine kinetics and estimated nicotine intake, which was calculated as mouth level exposure (MLE) of nicotine, from smoking two test cigarettes with different nicotine yields. This study was conducted in 16 healthy adult Japanese smokers, who did not have null nor reduced-activity alleles of CYP2A6, with a quasi-randomized crossover design of smoking a low-tar cigarette or a high-tar cigarette. Saliva cotinine showed similar concentration profiles to plasma cotinine, and all of the calculated pharmacokinetic parameters of cotinine showed the same values in plasma and saliva. The Cmax and AUC of cotinine showed almost the same dose-responsiveness to the estimated MLE of nicotine between plasma and saliva, but the tmax and t1/2 of cotinine were not affected by the estimated MLE of nicotine in either plasma or saliva. The results show that saliva cotinine kinetics reflects plasma cotinine kinetics, and measurement of saliva cotinine concentration gives the same information as plasma cotinine on the nicotine intake. Thus, saliva cotinine would be a good and less-invasive exposure marker of cigarette smoke, reflecting the plasma cotinine concentration and kinetics. PMID:23933006

Yuki, Dai; Kikuchi, Akira; Miura, Naoki; Kakehi, Aoi; Onozawa, Masahiro

2013-08-08

48

Active plasma resonance spectroscopy: a functional analytic description  

NASA Astrophysics Data System (ADS)

The term ‘active plasma resonance spectroscopy’ denotes a class of diagnostic methods which employ the ability of plasmas to resonate on or near the plasma frequency. The basic idea dates back to the early days of discharge physics: a signal in the GHz range is coupled to the plasma via an electrical probe; the spectral response is recorded, and then evaluated with a mathematical model to obtain information on the electron density and other plasma parameters. In recent years, the concept has found renewed interest as a basis of industry compatible plasma diagnostics. This paper analyzes the diagnostic technique in terms of a general description based on functional analytic (or Hilbert Space) methods which hold for arbitrary probe geometries. It is shown that the response function of the plasma-probe system can be expressed as a matrix element of the resolvent of an appropriately defined dynamical operator. A specialization of the formalism to a symmetric probe design is given, as well as an interpretation in terms of a lumped circuit model consisting of series resonance circuits. We present ideas for an optimized probe design based on geometric and electrical symmetry.

Lapke, M.; Oberrath, J.; Mussenbrock, T.; Brinkmann, R. P.

2013-04-01

49

BOOK REVIEW: Kinetic theory of plasma waves, homogeneous plasmas  

Microsoft Academic Search

The linear theory of plasma waves in homogeneous plasma is arguably the most mature and best understood branch of plasma physics. Given the recently revised version of Stix's excellent Waves in Plasmas (1992), one might ask whether another book on this subject is necessary only a few years later. The answer lies in the scope of this volume; it is

M. Brambilla

1998-01-01

50

Pair correlation function and nonlinear kinetic equation for a spatially uniform polarizable nonideal plasma  

SciTech Connect

Taking into account the first non-Markovian correction to the Balescu-Lenard equation, we have derived an expression for the pair correlation function and a nonlinear kinetic equation valid for a nonideal polarized classical plasma. This last equation allows for the description of the correlational energy evolution and shows the global conservation of energy with dynamical polarization. {copyright} {ital 1996 The American Physical Society.}

Belyi, V.V.; Kukharenko, Y.A.; Wallenborn, J. [IZMIRAN, Troitsk, Moscow region, 142092 (Russia)]|[UITPRAN, Moscow (Russia)]|[Physique Statistique, Plamsas et Optique non Lineaire, Universite Libre de Bruxelles, C.P.231, 1050 Bruxelles (Belgium)

1996-05-01

51

A unified description of tearing modes in plasmas  

Microsoft Academic Search

A unified description of tearing modes in an electron-ion plasma is presented. For this purpose, by employing the two-fluid model, which is valid beyond the magnetohydrodynamic model, new coupled mode equations for tearing modes are derived by retaining magnetic shear, the parallel electron inertia, the electron resistivity, the electron\\/ion neutral drag, as well as the ion Lorentz and the perpendicular

P. K. Shukla

1999-01-01

52

A unified description of tearing modes in plasmas  

Microsoft Academic Search

A unified description of tearing modes in an electron–ion plasma is presented. For this purpose, by employing the two-fluid model, which is valid beyond the magnetohydrodynamic model, new coupled mode equations for tearing modes are derived by retaining magnetic shear, the parallel electron inertia, the electron resistivity, the electron\\/ion neutral drag, as well as the ion Lorentz and the perpendicular

P. K. Shukla

1999-01-01

53

Kinetic theory of plasma sheaths surrounding electron-emitting surfaces.  

PubMed

A one-dimensional kinetic theory of sheaths surrounding planar, electron-emitting surfaces is presented which accounts for plasma electrons lost to the surface and the temperature of the emitted electrons. It is shown that ratio of plasma electron temperature to emitted electron temperature significantly affects the sheath potential when the plasma electron temperature is within an order of magnitude of the emitted electron temperature. The sheath potential goes to zero as the plasma electron temperature equals the emitted electron temperature, which can occur in the afterglow of an rf plasma and some low-temperature plasma sources. These results were validated by particle in cell simulations. The theory was tested by making measurements of the sheath surrounding a thermionically emitting cathode in the afterglow of an rf plasma. The measured sheath potential shrunk to zero as the plasma electron temperature cooled to the emitted electron temperature, as predicted by the theory. PMID:23992073

Sheehan, J P; Hershkowitz, N; Kaganovich, I D; Wang, H; Raitses, Y; Barnat, E V; Weatherford, B R; Sydorenko, D

2013-08-16

54

Kinetic Theory of Plasma Sheaths Surrounding Electron-Emitting Surfaces  

NASA Astrophysics Data System (ADS)

A one-dimensional kinetic theory of sheaths surrounding planar, electron-emitting surfaces is presented which accounts for plasma electrons lost to the surface and the temperature of the emitted electrons. It is shown that ratio of plasma electron temperature to emitted electron temperature significantly affects the sheath potential when the plasma electron temperature is within an order of magnitude of the emitted electron temperature. The sheath potential goes to zero as the plasma electron temperature equals the emitted electron temperature, which can occur in the afterglow of an rf plasma and some low-temperature plasma sources. These results were validated by particle in cell simulations. The theory was tested by making measurements of the sheath surrounding a thermionically emitting cathode in the afterglow of an rf plasma. The measured sheath potential shrunk to zero as the plasma electron temperature cooled to the emitted electron temperature, as predicted by the theory.

Sheehan, J. P.; Hershkowitz, N.; Kaganovich, I. D.; Wang, H.; Raitses, Y.; Barnat, E. V.; Weatherford, B. R.; Sydorenko, D.

2013-08-01

55

Pedestal Fueling Simulations with a Coupled Kinetic-kinetic Plasma-neutral Transport Code  

SciTech Connect

A Monte Carlo neutral transport routine, based on DEGAS2, has been coupled to the guiding center ion-electron-neutral neoclassical PIC code XGC0 to provide a realistic treatment of neutral atoms and molecules in the tokamak edge plasma. The DEGAS2 routine allows detailed atomic physics and plasma-material interaction processes to be incorporated into these simulations. The spatial pro le of the neutral particle source used in the DEGAS2 routine is determined from the uxes of XGC0 ions to the material surfaces. The kinetic-kinetic plasma-neutral transport capability is demonstrated with example pedestal fueling simulations.

D.P. Stotler, C.S. Chang, S.H. Ku, J. Lang and G.Y. Park

2012-08-29

56

Energy Conservation Tests of a Coupled Kinetic-kinetic Plasma-neutral Transport Code  

SciTech Connect

A Monte Carlo neutral transport routine, based on DEGAS2, has been coupled to the guiding center ion-electron-neutral neoclassical PIC code XGC0 to provide a realistic treatment of neutral atoms and molecules in the tokamak edge plasma. The DEGAS2 routine allows detailed atomic physics and plasma-material interaction processes to be incorporated into these simulations. The spatial pro le of the neutral particle source used in the DEGAS2 routine is determined from the uxes of XGC0 ions to the material surfaces. The kinetic-kinetic plasma-neutral transport capability is demonstrated with example pedestal fueling simulations.

D.P. Stotler, C.S. Chang, S.H. Ku, J. Lang and G. Park

2012-08-29

57

Plasma sheet particle precipitation: A kinetic model  

Microsoft Academic Search

Ionospheric and plasma sheet particle densities, fluxes and bulk velocities along an auroral magnetic field line have been calculated for an ion-exosphere model. It is shown that such a collisionless model accounts for many features observed above the auroral regions. Except for very strong plasma sheet electron precipitation, no large potential difference is needed along the magnetic field lines to

J. Lemaire; M. Scherer

1973-01-01

58

Kinetic Modifications to MHD Phenomena in Toroidal Plasmas  

SciTech Connect

Particle kinetic effects involving small spatial and fast temporal scales can strongly affect MHD phenomena and the long time behavior of plasmas. In particular, kinetic effects such as finite ion gyroradii, trapped particle dynamics, and wave-particle resonances have been shown to greatly modify the stability of MHD modes. Here, the kinetic effects of trapped electron dynamics and finite ion gyroradii are shown to have a large stabilizing effect on kinetic ballooning modes in low aspect ratio toroidal plasmas such as NSTX [National Spherical Torus Experiment]. We also present the analysis of Toroidicity-induced Alfven Eigenmodes (TAEs) destabilized by fast neutral-beam injected ions in NSTX experiments and TAE stability in ITER due to alpha-particles and MeV negatively charged neutral beam injected ions.

C.Z. Cheng; N.N. Gorelenkov; G.J. Kramer; E. Fredrickson

2004-09-03

59

Collisionless kinetic regimes for quasi-stationary axisymmetric accretion disc plasmas  

SciTech Connect

This paper is concerned with the kinetic treatment of quasi-stationary axisymmetric collisionless accretion disc plasmas. The conditions of validity of the kinetic description for non-relativistic magnetized and gravitationally bound plasmas of this type are discussed. A classification of the possible collisionless plasma regimes which can arise in these systems is proposed, which can apply to accretion discs around both stellar-mass compact objects and galactic-center black holes. Two different classifications are determined, which are referred to, respectively, as energy-based and magnetic field-based classifications. Different regimes are pointed out for each plasma species, depending both on the relative magnitudes of kinetic and potential energies and the magnitude of the magnetic field. It is shown that in all cases, there can be quasi-stationary Maxwellian-like solutions of the Vlasov equation. The perturbative approach outlined here permits unique analytical determination of the functional form for the distribution function consistent, in each kinetic regime, with the explicit inclusion of finite Larmor radius-diamagnetic and/or energy-correction effects.

Cremaschini, C. [International School for Advanced Studies (SISSA) and INFN, Trieste (Italy); Tessarotto, M. [Department of Mathematics and Geosciences, University of Trieste, Trieste (Italy)

2012-08-15

60

Plasma outflow from a corrugated trap in the kinetic regime  

SciTech Connect

The problem of stationary plasma outflow from an open corrugated trap in the kinetic regime is considered with allowance for pair collisions in the framework of a kinetic equation with the Landau collision integral. The distribution function is studied in the limit of small-scale corrugation and a large mirror ratio. In considering a single corrugation cell, a correction for the distribution function is calculated analytically. An equation describing variations of the distribution function along the system is derived and used to study the problem of plasma outflow into vacuum.

Skovorodin, D. I.; Beklemishev, A. D. [Russian Academy of Sciences, Budker Institute of Nuclear Physics, Siberian Branch (Russian Federation)

2012-03-15

61

Hybrid drift-kinetic electron/full kinetic ion PIC simulation of RF plasma discharge in magnetic mirror machine  

NASA Astrophysics Data System (ADS)

We present numerical simulations of a radio-frequency- (RF-) induced plasma discharge in magnetic mirror machines, with relevance to Electron Cyclotron Ion Source (ECRIS) devices. The simulations are done in 2D cylindrically symmetric geometry. The code SIMPL is a PIC code, which uses drift-kinetic electron and full kinetic ion description. The RF wave heating is implemented as a ``kick'' model, i.e., electrons get an increment in their perpendicular velocity when they cross the magnetic resonance surface. Atomic physics is for Argon and includes the following basic reactions: single ionization by electron impact, excitation, elastic scattering, and charge exchange. We will discuss the steady-state spatial structure of the discharge.

Evstatiev, Evstati

2012-10-01

62

Electron Kinetic Effects on Raman Backscatter in Plasmas  

SciTech Connect

We augment the usual three-wave cold-fluid equations governing Raman backscatter (RBS) with a new kinetic thermal correction, proportional to an average of particle kinetic energy weighted by the ponderomotive phase. From closed-form analysis within a homogeneous kinetic three-wave model and ponderomotively averaged kinetic simulations in a more realistic pulsed case, the magnitude of these new contributions is shown to be a measure of the dynamical detuning between the pump laser, seed laser, and Langmuir wave. Saturation of RBS is analyzed, and the role of trapped particles illuminated. Simple estimates show that a small fraction of trapped particles ({approx}6%) can significantly suppress backscatter. We discuss the best operating regime of the Raman plasma amplifier to reduce these deleterious kinetic effects.

Hur, M.S.; Suk, H. [Center for Advanced Accelerators, KERI, Changwon, Kyongnam 641-120 (Korea, Republic of); Lindberg, R.R.; Charman, A.E. [Department of Physics, University of California, Berkeley, Berkeley, California 94720 (United States); Wurtele, J.S. [Department of Physics, University of California, Berkeley, Berkeley, California 94720 (United States); Center for Beam Physics, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)

2005-09-09

63

Complete Spectrum of Kinetic Eigenmodes for Plasma Oscillations in a Weakly Collisional Plasma  

NASA Astrophysics Data System (ADS)

Kinetic eigenmodes of plasma oscillations in a weakly collisional plasma, described by a collision operator of the Fokker-Planck type, are obtained in closed form for initial-value as well as for boundary-value problems. These eigenmodes, which are smooth and compose a complete discrete spectrum, play the same role for weakly collisional plasmas as the Case Van Kampen modes do for collisionless plasmas.

Ng, C. S.; Bhattacharjee, A.; Skiff, F.

2004-02-01

64

Kinetic Theory of Equilibrium Axisymmetric Collisionless Plasmas in Off-equatorial Tori around Compact Objects  

NASA Astrophysics Data System (ADS)

The possible occurrence of equilibrium off-equatorial tori in the gravitational and electromagnetic fields of astrophysical compact objects has been recently proved based on non-ideal magnetohydrodynamic theory. These stationary structures can represent plausible candidates for the modeling of coronal plasmas expected to arise in association with accretion disks. However, accretion disk coronae are formed by a highly diluted environment, and so the fluid description may be inappropriate. The question is posed of whether similar off-equatorial solutions can also be determined in the case of collisionless plasmas for which treatment based on kinetic theory, rather than a fluid one, is demanded. In this paper the issue is addressed in the framework of the Vlasov-Maxwell description for non-relativistic, multi-species axisymmetric plasmas subject to an external dominant spherical gravitational and dipolar magnetic field. Equilibrium configurations are investigated and explicit solutions for the species kinetic distribution function are constructed, which are expressed in terms of generalized Maxwellian functions characterized by isotropic temperature and non-uniform fluid fields. The conditions for the existence of off-equatorial tori are investigated. It is proved that these levitating systems are admitted under general conditions when both gravitational and magnetic fields contribute to shaping the spatial profiles of equilibrium plasma fluid fields. Then, specifically, kinetic effects carried by the equilibrium solution are explicitly provided and identified here with diamagnetic energy-correction and electrostatic contributions. It is shown that these kinetic terms characterize the plasma equation of state by introducing non-vanishing deviations from the assumption of thermal pressure.

Cremaschini, Claudio; Ková?, Ji?í; Slaný, Petr; Stuchlík, Zden?k; Karas, Vladimír

2013-11-01

65

Nonlocal, Kinetic Stimulated Raman Scattering in Nonuniform Plasmas  

NASA Astrophysics Data System (ADS)

Excitation of continuously phase-locked (autoresonant) plasma waves in a nonuniform plasma via stimulated Raman backscattering is analyzed with a focus on the kinetic regime (k?D˜1). The dominant nonlinear effect in this regime is that of resonant particles and the plasma wave excitation is a nonlocal process involving formation and transport of the electron phase space holes. Whitham's averaged variational principle is applied in studying the coupled plasma, laser pump and seed waves dynamics. A flat-top electron velocity distribution is used as the simplest model allowing a variational formulation within the water bag theory. The corresponding Lagrangian, averaged over the fast phase variable, yields evolution equations for the slow field variables. The adiabatic multiple water bag extension of the theory for application to autoresonant plasma waves in nonuniform plasmas with more realistic initial distributions is also discussed. Numerical solutions of the system of slow variational equations are compared with Vlasov-Ampere simulations.

Khain, Pavel; Friedland, Lazar; Shagalov, Arkadiy; Wurtele, Jonathan

2012-10-01

66

Spin Kinetic Models of Plasmas - Semiclassical and Quantum Mechanical Theory  

SciTech Connect

In this work a recently published semiclassical spin kinetic model, generalizing those of previous authors are discussed. Some previously described properties are reviewed, and a new example illustrating the theory is presented. The generalization to a fully quantum mechanical description is discussed, and the main features of such a theory is outlined. Finally, the main conclusions are presented.

Brodin, Gert; Marklund, Mattias; Zamanian, Jens [Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden)

2009-11-10

67

The Mechanism and kinetics of plasma polymerization  

Microsoft Academic Search

The discussion presented in this review has shown that plasma polymerization is a complex process involving a large number of both homogeneous and heterogeneous reactions. While the details of the overall polymer deposition mechanism are not yet understood fully, certain features have been elucidated. Thus, the available experimental evidence suggests that free radicals are the primary species propagating chain growth,

Alexis T. Bell

68

Kinetic model for generation and growth of plasma dust nanoparticles  

Microsoft Academic Search

A kinetic model is presented to describe the production and the growth of clusters and dust nanoparticles in low-pressure plasmas. The important processes of losses by diffusion and collisions with electrons and ions of the clusters and grains have been taken into consideration. Formulas and equations have been provided to calculate neutral and negatively charged cluster function distribution according to

B. F. Gordiets; E. Bertran

2005-01-01

69

PLASMAKIN: A chemical kinetics library for plasma physics modeling  

Microsoft Academic Search

PLASMAKIN is a software library to handle physical and chemical data used in plasma physics modeling and to compute kinetics data from the reactions taking place in the gas or at the surfaces - particle generation and loss rates, photon emission rates and energy exchange rates. PLASMAKIN supports any number of chemical species and reactions, is independent of problem dimensions

2001-01-01

70

PLASMAKIN: A chemical kinetics library for plasma physics modeling  

Microsoft Academic Search

PLASMAKIN is a software library to handle physical and chemical data used in plasma physics modeling and to compute kinetics data from the reactions taking place in the gas or at the surfaces — particle generation and loss rates, photon emission rates and energy exchange rates. PLASMAKIN supports any number of chemical species and reactions, is independent of problem dimensions

Nuno R. Pinhão

2001-01-01

71

Kinetics in Gas Mixtures for Problem of Plasma Assisted Combustion.  

National Technical Information Service (NTIS)

Throughout the whole period of the research we performed the following tasks: The current state of the art in approaches to the study of kinetics of plasma assisted combustion and ignition has been reviewed. It was demonstrated that, in spite of a large b...

S. Starikovskaia

2010-01-01

72

Kinetic description of electron beams in the solar chromosphere  

SciTech Connect

We formulate the relativistic Fokker-Plank equation for a beam of accelerated electrons interacting with a partially ionized plasma. In our derivation we conserved those terms contributing to velocity diffusion and found that this effect cannot be neglected a priori. We compute the terms accounting for elastic and inelastic collisions with neutral hydrogen and helium. Collisions with neutral hydrogen are found to be dominant throughout the chromosphere, except at the uppermost layers close to the transition region. As an application, we compute the loss of energy and momentum for a power-law beam impinging on the solar chromosphere, for a particular case in which the Fokker-Planck equation can be integrated analytically. We find that most of the beam energy is deposited in a relatively thin region of the chromosphere, a result which is largely insensitive to the theoretical method employed to compute the energy deposition rate. 26 refs.

Gomez, D.O.; Mauas, P.J. (Hawaii Univ., Honolulu (United States) Arcetri Osservatorio Astrofisico, Florence (Italy))

1992-10-01

73

Toward a Fully Kinetic Theory of Turbulence in Magnetized Plasmas  

SciTech Connect

This paper outlines the present status of the kinetic theory of turbulence in magnetized plasmas as being developed by the present author. The systematic program to formulate the theory of turbulence starting from the Vlasov-Klimontovich formalism began with the works by pioneers of modern plasma physics in the 1960s and 1970s. However, early efforts adopted the heuristic semi-classical method instead of the statistical mechanical formulation, which is necessary for a quantitative analysis. Recently, the present author picked up where the early pioneers left, and began to reformulate the kinetic turbulence theory of turbulence in magnetized plasmas from statistical mechanical formalism. This paper is a brief outline of the progress to date.

Yoon, Peter H. [IPST, University of Maryland, College Park, MTL, Inc., 330 Pleasant Street, Belmont, MA, SSR, Kyung Hee University (Korea, Republic of)

2010-12-30

74

Kinetic Alfven waves in plasmas with heavy ions  

SciTech Connect

Since its wide identification in measurements by satellites in space plasmas as well as its potential importance in the energization of plasma particles, the kinetic Alfven wave (KAW) has been discussed extensively in the two-component (electron-proton) plasma model. The component of heavy ions, however, can frequently be found in space and astrophysical plasmas and can affect considerably the properties of the KAWs in them. In this paper, based on a three-component (i.e., electrons, protons, and heavy ions) plasma model, characteristics of KAWs are investigated. The results show that the dispersion of KAWs splits up into two branches. In the long wavelength limit, one branch has an asymptotic solution of shear Alfven waves, while the other approaches an electrostatic wave with a frequency between the proton and heavy ion gyrofrequencies. Their polarization and resonance are also discussed.

Yang, L.; Wu, D.J. [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); and Graduate School of the Chinese Academy of Sciences, Beijing 100039 (China); Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2005-06-15

75

From kinetic MHD in stellarators to a fully kinetic description of wave particle interaction  

Microsoft Academic Search

We use a linearized model of kinetic MHD for the perturbative calculation of growth rates of Alfvén eigenmodes. The numerical model, a code called CAS3D-K, is based on the three-dimensional ideal MHD stability code CAS3D and a numeric solution of the drift kinetic equation which avoids approximations to the magnetic geometry but neglects the drifts of the particles away from

Axel Koenies; Alexey Mishchenko; Roman Hatzky

2008-01-01

76

Collisionless energy-independent kinetic equilibria in axisymmetric magnetized plasmas  

NASA Astrophysics Data System (ADS)

The proof of existence of Vlasov-Maxwell equilibria which do not exhibit a functional dependence in terms of the single-particle energy is established. The theory deals with the kinetic treatment of multispecies axisymmetric magnetized plasmas, with particular reference to plasma systems which are slowly time varying. Aside from collisionless laboratory plasmas, the theory concerns important aspects of astrophysical scenarios, such as accretion-disk and coronal plasmas arising in the gravitational field of compact objects. Qualitative properties of the solution are investigated by making use of a perturbative kinetic theory. These concern the realization of the equilibrium kinetic distribution functions in terms of generalized Gaussian distributions and the constraints imposed by the Maxwell equations. These equilibria are shown to be generally non-neutral and characterized by the absence of the Debye screening effect. As a further application, the stability properties of these equilibria with respect to axisymmetric electromagnetic perturbations are addressed. This permits us to establish absolute stability criteria holding in such a case.

Cremaschini, Claudio; Stuchlík, Zden?k; Tessarotto, Massimo

2013-09-01

77

Energy conservation tests of a coupled kinetic plasma–kinetic neutral transport code  

NASA Astrophysics Data System (ADS)

An approach to coupling two kinetic particle codes for the simulation of neutral–plasma interactions in magnetic fusion devices is described. The behavior of the neutral atoms and molecules is modeled with a Monte Carlo code. The plasma species are simulated with a particle-in-cell code that integrates the guiding center equations of motion and computes a self-consistent electric field. The coupling algorithm is designed to conserve mass in the neutral–plasma exchanges to statistical accuracy. Although energy is not fully conserved due to the velocity dependence of the charge exchange cross section and the kinetic character of both species, the impact of this non-conservation on the overall simulation is negligible.

Stotler, D. P.; Chang, C. S.; Park, G.; Ku, S. H.

2013-01-01

78

Kinetic integrated modeling of tokamak plasmas by TASK3G  

NASA Astrophysics Data System (ADS)

Deviation of momentum distribution function from the Maxwellian is unavoidable in tokamak plasmas under heating and current drive. The deviation may affect transport, global stability, diagnostics and fusion reaction rate of burning plasmas. In order to describe the time evolution of the momentum distribution functions of plasma species self-consistently, we have developed a kinetic version of the integrated tokamak modeling code TASK3G as the third generation of the TASK code. Transport, heating and current drive are described by the bounce averaged Fokker-Planck equation. The calculated momentum distribution function is used for the analyses of wave propagation and absorption, global stability, and diagnostics. The bounce-averaged Fokker-Planck equation includes nonlinear Coulomb collision, quasi-linear wave interaction, neoclassical and turbulent-driven radial transport and particle source/sink. A typical example of TASK3G result for ITER burning plasma will be presented.

Fukuyama, A.; Murakami, S.; Wakasa, A.; Nuga, H.; Okamoto, T.

2009-11-01

79

Charging kinetics of dust in interplanetary space plasma  

NASA Astrophysics Data System (ADS)

A theoretical kinetic model for the physical understanding of the charging of dust particles in the interplanetary space plasma has been developed. In contrast to earlier studies, the present analysis incorporates (i) uniform potential theory for complex plasmas with size distribution of the dust particles, (ii) charge, number and energy balance of the constituents and (iii) appropriate expressions for photoelectric emission from a positively charged particle with inherent charge neutrality of the interplanetary space plasma. Further utilizing the population balance equation (given by Matsoukas and Russel) for the interplanetary dust particles, the fluctuations in steady-state charge (or electric potential) has also been investigated. For the illustration purpose, the computations have been performed for the interplanetary space plasma at 1 au from the sun; for this distance, reasonably good information on the gaseous and dust components are available. As an interesting feature, the theoretical predictions are in reasonably good agreement with observations and earlier estimates.

Misra, Shikha; Mishra, S. K.

2013-07-01

80

Chemical Cycle Kinetics: Removing the Limitation of Linearity of a Non-equilibrium Thermodynamic Description  

NASA Astrophysics Data System (ADS)

Chemical cycle kinetics is customarily analyzed by means of the law of mass action which describes how the concentrations of the substances vary with time. The connection of this approach with non-equilibrium thermodynamics (NET) has traditionally been restricted to the linear domain close to equilibrium in which the reaction rates are linear functions of the affinities. We show, by a pertinent formulation of the concept of local equilibrium in the mesoscopic description along the reaction coordinates, that the connection between kinetic and thermodynamic approaches is deeper than thought and holds in the nonlinear domain far from equilibrium, for higher values of the affinity. This new perspective indicates how to overcome the inherent limitation of classical NET in treating cyclic reactions, providing a description of closed and open cycles operating far from equilibrium, in accordance with thermodynamic principles. We propose that the new set of equations are tested and used for data reduction in chemical reaction kinetics.

Rubi, J. M.; Bedeaux, D.; Kjelstrup, S.; Pagonabarraga, I.

2013-07-01

81

Weakly Ionized Plasmas in Hypersonics: Fundamental Kinetics and Flight Applications  

NASA Astrophysics Data System (ADS)

The paper reviews some of the recent studies of applications of weakly ionized plasmas to supersonic/hypersonic flight. Plasmas can be used simply as means of delivering energy (heating) to the flow, and also for electromagnetic flow control and magnetohydrodynamic (MHD) power generation. Plasma and MHD control can be especially effective in transient off-design flight regimes. In cold air flow, nonequilibrium plasmas must be created, and the ionization power budget determines design, performance envelope, and the very practicality of plasma/MHD devices. The minimum power budget is provided by electron beams and repetitive high-voltage nanosecond pulses, and the paper describes theoretical and computational modeling of plasmas created by the beams and repetitive pulses. The models include coupled equations for non-local and unsteady electron energy distribution function (modeled in forward-back approximation), plasma kinetics, and electric field. Recent experimental studies at Princeton University have successfully demonstrated stable diffuse plasmas sustained by repetitive nanosecond pulses in supersonic air flow, and for the first time have demonstrated the existence of MHD effects in such plasmas. Cold-air hypersonic MHD devices are shown to permit optimization of scramjet inlets at Mach numbers higher than the design value, while operating in self-powered regime. Plasma energy addition upstream of the inlet throat can increase the thrust by capturing more air (Virtual Cowl), or it can reduce the flow Mach number and thus eliminate the need for an isolator duct. In the latter two cases, the power that needs to be supplied to the plasma would be generated by an MHD generator downstream of the combustor, thus forming the ``reverse energy bypass'' scheme. MHD power generation on board reentry vehicles is also discussed.

Macheret, Sergey

2005-05-01

82

Kinetic theory of Jeans instability of a dusty plasma.  

PubMed

A kinetic theory of the Jeans instability of a dusty plasma has been developed in the present work. The effect of grain charge fluctuations due to the attachment of electrons and ions to the grain surface has been considered in the framework of Krook's collisional model. We demonstrate that the grain charge fluctuations alter the growth rate of the gravitational collapse of the dusty plasma. The Jeans length has been derived under limiting cases, and its dependence on the attachment frequency is shown. In the absence of gravity, we see that the damping rate of the dust acoustic mode is proportional to the electron-dust collision frequency. PMID:11970688

Pandey, B P; Lakhina, G S; Krishan, V

1999-12-01

83

Kinetic Properties of Alfvén Modes in Tokamak Plasmas  

Microsoft Academic Search

The ability to predict the stability of fast-particle-driven Alfvén eigenmodes in burning fusion plasmas requires a detailed understanding of the dissipative mechanisms that damp these modes. In order to address this question, the linear gyro-kinetic, electromagnetic code LIGKA is employed to investigate their behaviour in realistic tokamak geometry. The eigenvalue formulation of LIGKA allows to calculate self-consistently the coupling of

Ph. Lauber; S. Guenter; M. Bruedgam; A. Koenies; S. D. Pinches

2006-01-01

84

Plasma kinetics in man of epicatechin from black chocolate  

Microsoft Academic Search

Objective: To evaluate the plasma kinetics in man of epicatechin from black chocolate.Design: An intervention study with 8 volunteers. Each served as his own control. Theobromine was used as control marker of the chocolate intake.Setting: Metabolic Unit, Nestlé Research Center, Vers-chez-les-Blanc, Switzerland.Subjects: Eight healthy male volunteers (4 smokers and 4 non-smokers) were enrolled in this study. They abstained from foods

M Richelle; I Tavazzi; M Enslen; EA Offord

1999-01-01

85

Plasma transport induced by kinetic Alfven wave turbulence  

SciTech Connect

At the Earth's magnetopause that separates the hot-tenuous magnetospheric plasma from the cold dense solar wind plasma, often seen is a boundary layer where plasmas of both origins coexist. Plasma diffusions of various forms have been considered as the cause of this plasma mixing. Here, we investigate the plasma transport induced by wave-particle interaction in kinetic Alfven wave (KAW) turbulence, which is one of the candidate processes. We clarify that the physical origin of the KAW-induced cross-field diffusion is the drift motions of those particles that are in Cerenkov resonance with the wave: E Multiplication-Sign B-like drift that emerges in the presence of non-zero parallel electric field component and grad-B drift due to compressional magnetic fluctuations. We find that KAW turbulence, which has a spectral breakpoint at which an MHD inertial range transits to a dissipation range, causes selective transport for particles whose parallel velocities are specified by the local Alfven velocity and the parallel phase velocity at the spectral breakpoint. This finding leads us to propose a new data analysis method for identifying whether or not a mixed plasma in the boundary layer is a consequence of KAW-induced transport across the magnetopause. The method refers to the velocity space distribution function data obtained by a spacecraft that performs in situ observations and, in principle, is applicable to currently available dataset such as that provided by the NASA's THEMIS mission.

Izutsu, T. [Department of Earth and Planetary Science, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 133-0033 (Japan); Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Hasegawa, H.; Fujimoto, M. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Nakamura, T. K. M. [X-Computational Physics Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2012-10-15

86

Consistent Recycling in a Coupled Kinetic Plasma - Neutral Transport Code  

NASA Astrophysics Data System (ADS)

The role of neutral fueling in the buildup of the H-mode pedestal is a topic of interest for the FY2011 Joint Research Target on Pedestal Structure. The particular effects of kinetic neutral and plasma phenomena in the pedestal buildup are being examined via the coupled DEGAS 2 Monte Carlo neutral and XGC neoclassical particle transport codes, developed as part of the Center for Plasma Edge Simulation. The coupled codes have recently been used to quantify the particle pinch associated with cold ions resulting from recycling at the plasma edgeootnotetextW. Wan et al., Phys. Plasmas 18, 056116 (2011). The next step in the code development is to use the flux of ions striking material surfaces in XGC as the source of recycled neutral atoms and molecules in DEGAS 2. In this way, the poloidal distribution of the neutral source will evolve consistently with the plasma as the pedestal builds up. XGC will also provide the energy of the ions hitting the surface, allowing the application of detailed plasma material interaction models to determine the relative fractions of atoms and molecules generated by recycling. The atom / molecule ratio in turn impacts the velocity distribution of the neutral species and, thus, their penetration into the core plasma.

Stotler, D. P.; Chang, C. S.; Park, G.

2011-11-01

87

Kinetic properties of shear Alfvén eigenmodes in tokamak plasmas  

NASA Astrophysics Data System (ADS)

This work reports on numerical calculations concerning the kinetic properties of low-n, low-m toroidal Alfvén eigenmodes (TAEs) in tokamak plasmas for fusion relevant parameters. The self-consistent and nonperturbative code LIGKA [Ph. Lauber, Ph.D. thesis, TU München (2003)] is employed. It is based on a linear gyrokinetic model consisting of the quasineutrality equation and the moment equation for the perturbed current. It is shown that in a certain limit the underlying equations of LIGKA can be simplified to the equations known as the ``reduced kinetic model.'' An antenna-like version of LIGKA allows one to systematically find all shear-Alfvén-type modes in a given frequency interval, such as kinetic TAEs (KTAEs) and kinetically modified TAEs. The coupling to the kinetic Alfvén wave (KAW) is found in the form of continuum damping and radiative damping. For the cases examined here, no mode conversion in the centre is found. In the case of a large nonideal parameter, damping rates around 0.5%-1% are found, close to experimental measurements.

Lauber, Ph.; Günter, S.; Pinches, S. D.

2005-12-01

88

H atom surface loss kinetics in pulsed inductively coupled plasmas  

NASA Astrophysics Data System (ADS)

Pulsed plasmas are very powerful tools to investigate mechanisms. This paper is focused on H atom kinetics in low-pressure high-density inductively coupled pulsed plasmas. We explore pure H2, H2/N2, CH4/H2 and CH4/N2 mixtures. These gas mixtures offer two very different kinds of wall conditions, which are stainless-steel and hydrocarbon-coated walls. It shows that H loss probability (?) is sensitive to wall conditions. Efforts are made to understand ? evolutions with the different parameters. The effect of pressure in non-depositing plasmas is also investigated. Evolution of H atom surface loss probability is linked to ion flux measurements. Ion bombardment promotes H surface loss.

Jacq, S.; Cardinaud, C.; Le Brizoual, L.; Granier, A.

2013-10-01

89

Kinetic simulations of ultra-intense laser plasma interactions  

NASA Astrophysics Data System (ADS)

Kinetic simulations are used to investigate the interaction of an ultra-intense, small spot-size laser beam with a preformed plasma. The beam is sufficiently intense to drive the electrons relativistically and to impart a pressure in excess of hundreds of Mbars to the plasma. Key features of the interaction include generation of electrons and inward-directed ions with energies in the Mev range and strong hole boring which enhances the absorption. The simulations also show self-generated magnetic fields of order 10(exp 8) Gauss, a Rayleigh-Taylor like instability of the light-plasma interface, as well as self-focusing of the laser beam and strong Raman backscatter.

Kruer, W. L.; Wilks, S. C.

1992-06-01

90

The Effects of Weak Collisions on Nonlinear Plasma Kinetics  

NASA Astrophysics Data System (ADS)

Kinetic plasma behaviors have long been of interest to those studying space and laboratory plasmas. For instance, kinetic plasma instabilities are widely believed to be responsible for the generation of anomalous resistivity in reconnection layers, providing a possible mechanism for fast reconnection. The concept of Landau damping is fundamental to such wave kinetic instabilities in space, and is treated typically within the framework of the collisionless Vlasov equation. It has become clear in recent theoretical and experimental work that weak collisions are a singular perturbation on the collisionless theory, and qualitatively alter the results of the collisionless theory. In particular, it has been demonstrated by C. S. Ng, A. Bhattacharjee, and F. Skiff that the Case-Van Kampen continuous spectrum, which are the underlying eigenmodes of the collisionless system, are completely eliminated and replaced by a discrete spectrum (hereafter referred to as the NBS spectrum). The NBS spectrum includes Landau-damped roots as exact eigenmodes, but is significantly broader, including a larger spectrum of discrete roots. We discuss the implications of these results for two nonlinear applications, the plasma wave echo and the ion acoustic instability, by means of a new Vlasov code that has been modified to include the Lenard-Bernstein collision operator. We show that the existing collisional theories for the echo, which fail to account for the discrete collisional spectrum, come close, but do not quite yield the appropriate collisional damping rates. Of greater practical importance to problems involving dissipation and anomalous transport is the generation of anomalous resistivity due to microinstabilities. As a specific example, we consider the ion acoustic wave. We compare our numerical findings with the anomalous resistivity estimates of A. Galeev and R. Z. Sagdeev for both collisionless and weakly collisional systems. In the regime of applicability of the theoretical estimates, the agreement is good within an order of magnitude.

Black, Carrie E.

91

Linking the hydrodynamic and kinetic description of a dissipative relativistic conformal theory  

SciTech Connect

We use the entropy production variational method to associate a one-particle distribution function to the assumed known energy-momentum and entropy currents describing a relativistic conformal fluid. Assuming a simple form for the collision operator we find this one-particle distribution function explicitly, and show that this method of linking the hydro and kinetic descriptions is a nontrivial generalization of Grad's ansatz. The resulting constitutive relations are the same as in the conformal dissipative type theories discussed by J. Peralta-Ramos and E. Calzetta [Phys. Rev. D 80, 126002 (2009)]. Our results may prove useful in the description of freeze-out in ultrarelativistic heavy-ion collisions.

Calzetta, E.; Peralta-Ramos, J. [CONICET and Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires-Ciudad Universitaria, Pabellon I, 1428 Buenos Aires (Argentina); Instituto de Fisica Teorica, Universidade Estadual Paulista, Rua Doutor Bento Teobaldo Ferraz 271 - Bloco II, 01140-070 Sao Paulo (Brazil)

2010-11-15

92

Krook collisional models of the kinetic susceptibility of plasmas  

NASA Astrophysics Data System (ADS)

An assessment is made of Krook collisional models used to describe the kinetic behavior of collective oscillations, i.e., when Landau damping and collisions must be considered, as is often the case for low-frequency waves. The study focuses on an early energy-conserving model [B. D. Fried, A. N. Kaufman, and D. L. Sachs, Phys. Fluids 9, 292 (1966)] that is shown to be identical to a more modern version used in drift-wave stability studies [G. Rewoldt, W. M. Tang, and R. J. Hastie, Phys. Fluids 29, 2893 (1986)]. The inadequacy of the simpler, and often used, nonconserving model is illustrated. Comparisons are established with recent collisional studies of ion acoustic waves [V. Yu. Bychenkov, J. Myatt, W. Rozmus, and V. T. Tikhonchuk, Phys. Plasmas 1, 2419 (1994)] and electron plasma waves [C. S. Ng, A. Bhattacharjee, and F. Skiff, Phys. Rev. Lett. 83, 1974 (1999)]. A connection is also established with contemporary studies of condensed matter and quantum liquids [K. Morawetz and U. Fuhrmann, Phys. Rev. E 61, 2272 (2000); 62, 4382 (2000)]. A useful empirical fit is found that corrects the Braginskii susceptibility to incorporate the kinetic behavior associated with the Krook kinetic susceptibility.

Opher, M.; Morales, G. J.; Leboeuf, J. N.

2002-07-01

93

Krook collisional models of the kinetic susceptibility of plasmas.  

PubMed

An assessment is made of Krook collisional models used to describe the kinetic behavior of collective oscillations, i.e., when Landau damping and collisions must be considered, as is often the case for low-frequency waves. The study focuses on an early energy-conserving model [B. D. Fried, A. N. Kaufman, and D. L. Sachs, Phys. Fluids 9, 292 (1966)] that is shown to be identical to a more modern version used in drift-wave stability studies [G. Rewoldt, W. M. Tang, and R. J. Hastie, Phys. Fluids 29, 2893 (1986)]. The inadequacy of the simpler, and often used, nonconserving model is illustrated. Comparisons are established with recent collisional studies of ion acoustic waves [V. Yu. Bychenkov, J. Myatt, W. Rozmus, and V. T. Tikhonchuk, Phys. Plasmas 1, 2419 (1994)] and electron plasma waves [C. S. Ng, A. Bhattacharjee, and F. Skiff, Phys. Rev. Lett. 83, 1974 (1999)]. A connection is also established with contemporary studies of condensed matter and quantum liquids [K. Morawetz and U. Fuhrmann, Phys. Rev. E 61, 2272 (2000); 62, 4382 (2000)]. A useful empirical fit is found that corrects the Braginskii susceptibility to incorporate the kinetic behavior associated with the Krook kinetic susceptibility. PMID:12241490

Opher, M; Morales, G J; Leboeuf, J N

2002-07-29

94

Anomalous Ion Kinetic Effects in RF Plasma Sheaths  

NASA Astrophysics Data System (ADS)

An ion PIC code (1d2v) has been written to examine anomalous ion kinetic effects in rf sheaths. These phenomena are more pronounced in low pressure, plasma processing, capacitive applicators, where rf frequencies are typically less than the ion plasma frequency. For computational stability, a Newton Krylov solver was used to solve the Poisson Boltzmann equation. Using this code, the average ion velocity in the pre-sheath can be shown to have dramatic effects on the ion kinetics in sheath and pre-sheath regions when it exceeds the ion sound speed, Cs. As previously shown [Sternberg & Godyak, IEEE Trans. Plasma Sci., 35(5), 2007], the ion average velocity can be ˜2.5 Cs at the pre-sheath/sheath interface - thereby creating a region where the ions in the pre-sheath have a Mach number greater than unity, giving rise to a wave-train of ion acoustic shock waves in a limited region. These waves are critically damped as they enter the sheath and give rise to additional structure in the ion velocity distribution function, particularly at lower sheath voltages. The nature of the dual peaked ion velocity distribution function will also be discussed in terms of ion resonance with the sheath electric field that derives from the motion of the electron sheath.

Barnes, Michael; Gekelman, Walter; Pribyl, Patrick

2011-11-01

95

Kinetic phenomena in charged particle transport in gases and plasmas  

NASA Astrophysics Data System (ADS)

The key difference between equilibrium (thermal) and non-equilibrium (low temperature - a.k.a. cold) plasmas is in the degree in which the shape of the cross sections influences the electron energy distribution function (EEDF). In this paper we will discuss the issue of kinetic phenomena from two different angles. The first will be how to take advantage of the strong influence and use low current data to obtain the cross sections. This is also known as the swarm technique and the product of a ``swarm analysis'' is a set of cross sections giving good number, momentum and energy balances of electrons or other charged particles. At the same time understanding the EEDF is based on the cross section data. Nevertheless sometimes the knowledge of the cross sections and even the behaviour of individual particles are insufficient to explain collective behaviour of the ensemble. The resulting ``kinetic'' effects may be used to favour certain properties of non-equilibrium plasmas and even may be used as the basis of some new plasma applications.

Petrovi?, Zoran Lj.; Dujko, Saša; Šaši?, Olivera; Stojanovi?, Vladimir; Malovi?, Gordana

2012-05-01

96

Kinetic phenomena in charged particle transport in gases and plasmas  

SciTech Connect

The key difference between equilibrium (thermal) and non-equilibrium (low temperature - a.k.a. cold) plasmas is in the degree in which the shape of the cross sections influences the electron energy distribution function (EEDF). In this paper we will discuss the issue of kinetic phenomena from two different angles. The first will be how to take advantage of the strong influence and use low current data to obtain the cross sections. This is also known as the swarm technique and the product of a ''swarm analysis'' is a set of cross sections giving good number, momentum and energy balances of electrons or other charged particles. At the same time understanding the EEDF is based on the cross section data. Nevertheless sometimes the knowledge of the cross sections and even the behaviour of individual particles are insufficient to explain collective behaviour of the ensemble. The resulting ''kinetic'' effects may be used to favour certain properties of non-equilibrium plasmas and even may be used as the basis of some new plasma applications.

Petrovic, Zoran Lj.; Dujko, Sasa; Sasic, Olivera; Stojanovic, Vladimir; Malovic, Gordana [Institute of Physics, University of Belgrade, POB 68 11080 Zemun (Serbia); Faculty of Traffic Engineering, University of Belgrade Belgrade (Serbia); Institute of Physics, University of Belgrade, POB 68 11080 Zemun (Serbia)

2012-05-25

97

Kinetic Properties of Alfvén Modes in Tokamak Plasmas  

NASA Astrophysics Data System (ADS)

The ability to predict the stability of fast-particle-driven Alfvén eigenmodes in burning fusion plasmas requires a detailed understanding of the dissipative mechanisms that damp these modes. In order to address this question, the linear gyro-kinetic, electromagnetic code LIGKA is employed to investigate their behaviour in realistic tokamak geometry. The eigenvalue formulation of LIGKA allows to calculate self-consistently the coupling of large-scaled MHD modes to the gyroradius scale-length kinetic Alfvén waves. Therefore, the properties of the kineticly modified TAE mode in or near the gap (KTAE, radiative damping or `tunnelling') and its coupling to the continuum close to the edge can be analysed numerically. In addition, an antenna-like version of LIGKA allows for a frequency scan, analogous to an external antenna. The model and the implementation of LIGKA were recently extended in order to capture the coupling of the shear Alfvén waves to the sound waves. This coupling becomes important for the investigation of kinetic effects on the low-frequency phase of cascade modes, where e.g. geodesic acoustic effects play a significant role.

Lauber, Ph.; Günter, S.; Brüdgam, M.; Könies, A.; Pinches, S. D.

2006-11-01

98

Propagation of radiation in fluctuating multiscale plasmas. II. Kinetic simulations  

SciTech Connect

A numerical algorithm is developed and tested that implements the kinetic treatment of electromagnetic radiation propagating through plasmas whose properties have small scale fluctuations, which was developed in a companion paper. This method incorporates the effects of refraction, damping, mode structure, and other aspects of large-scale propagation of electromagnetic waves on the distribution function of quanta in position and wave vector, with small-scale effects of nonuniformities, including scattering and mode conversion approximated as causing drift and diffusion in wave vector. Numerical solution of the kinetic equation yields the distribution function of radiation quanta in space, time, and wave vector. Simulations verify the convergence, accuracy, and speed of the methods used to treat each term in the equation. The simulations also illustrate the main physical effects and place the results in a form that can be used in future applications.

Pal Singh, Kunwar; Robinson, P. A.; Cairns, Iver H.; Tyshetskiy, Yu. [School of Physics, University of Sydney, Sydney, NSW 2006 (Australia)

2012-11-15

99

Complete Spectrum of Kinetic Eigenmodes for Plasma Oscillations in a Weakly Collisional Plasma  

NASA Astrophysics Data System (ADS)

Kinetic eigenmodes of plasma oscillations in a weakly collisional plasma, described by a collision operator of the Fokker-Planck-type, are obtained in closed form for initial-value as well as boundary-value problems. These eigenmodes, which are smooth and comprise a complete discrete spectrum, play the same role for weakly collisional plasmas as the Case-Van Kampen modes do for collisionless plasmas. It is shown analytically in the limit of zero collision that the eigenfrequency of an eigenmode belonging to a subset of the spectrum tends to the value given by the usual Landau damping analysis. Fundamental implications of these results for classical as well as recent experimental and theoretical findings on the collisional decay of plasma echoes and the ballistic response are discussed.

Ng, C. S.; Bhattacharjee, A.; Skiff, F.

2003-10-01

100

Solitary kinetic Alfven waves in bi-ion plasmas  

SciTech Connect

A Sagdeev equation is provided for the solitary kinetic Alfven waves (SKAWs) in a low-{beta} (m{sub e}/m{sub i}<<{beta}<<1 or m{sub i}/m{sub e}>>{alpha}>>1), three-component (electrons, protons, and heavy ions) plasma. Then we get the numerical solution of the equation. It is found that the density humps of SKAWs can exist in the sub-Alfvenic region. The heavy ion density amplitude and the width of the SKAWs rise with the increase in the initial density of heavy ions n{sub b0} in such bi-ion plasmas. The perturbed electromagnetic fields E{sub z}, E{sub x}, and B{sub y} are also studied further to discuss the effects of heavy ions on them. Also, numerical outcomes have been offered for cases with several different parameters to illustrate these results.

Yang, L.; Wu, D.J. [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China) and Graduate School of Chinese Academy of Sciences, Beijing 100039 (China); Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2005-11-15

101

Ultrahigh performance three-dimensional electromagnetic relativistic kinetic plasma simulation  

SciTech Connect

The algorithms, implementation details, and applications of VPIC, a state-of-the-art first principles 3D electromagnetic relativistic kinetic particle-in-cell code, are discussed. Unlike most codes, VPIC is designed to minimize data motion, as, due to physical limitations (including the speed of light{exclamation_point}), moving data between and even within modern microprocessors is more time consuming than performing computations. As a result, VPIC has achieved unprecedented levels of performance. For example, VPIC can perform {approx}0.17 billion cold particles pushed and charge conserving accumulated per second per processor on IBM's Cell microprocessor--equivalent to sustaining Los Alamos's planned Roadrunner supercomputer at {approx}0.56 petaflop (quadrillion floating point operations per second). VPIC has enabled previously intractable simulations in numerous areas of plasma physics, including magnetic reconnection and laser plasma interactions; next generation supercomputers like Roadrunner will enable further advances.

Bowers, K. J.; Albright, B. J.; Yin, L.; Bergen, B.; Kwan, T. J. T. [Plasma Theory and Applications (X-1-PTA), Los Alamos National Laboratory, MS F699, P.O. Box 1663, Los Alamos, New Mexico 87545 (United States)

2008-05-15

102

Auto-ionization Effects on NLTE Kinetics of Laser Plasmas  

NASA Astrophysics Data System (ADS)

The ion charge state distribution of laser heated plasmas must often be modeled by a non-Local-Thermodynamic-Equilibrium (NLTE) kinetics scheme. Typically this results from a relatively weak ambient radiation field as compared with the influence of the local thermal (free) electrons. At modest to low densities a familiar picture is that the one-electron transition processes of collisional excitation and ionization are balanced by radiative recombination and decay. In fact, this regime is one in which the two-electron transition processes of auto-ionization and resonant-capture can also play an important role. Here we describe NLTE detailed configuration accounting (DCA) simulations which display the effects of the competition to establish the ion charge state balance of the plasma.

Albritton, J. R.; Wilson, B. G.

1998-11-01

103

Charged particle dynamics and molecular kinetics in the hydrogen postdischarge plasma  

SciTech Connect

The afterglow of a parallel plate radio frequency discharge in hydrogen is studied by numerical modelling to compare ion dynamics and chemical effects on the behavior of negative ions. While the ion dynamics requires a kinetic description of space dependent plasma relaxation (at least 1D), chemical effects require a vibrational kinetics of hydrogen molecules. Since previous models did not include both features it has not been possible until now to realize both effects in a single simulation. We apply an updated version of the 1D Bari model which includes a 1.5D (1Dr2Dv) Particle in Cell/Monte Carlo (PIC/MC) multispecies module coupled to the space and time dependent master equation for H{sub 2}(X{sup 1}{sigma}{sub g}{sup +},v=0,...,14) vibrational level population. Negative ion fronts are described in hydrogen for the first time and their impact on the plasma limiting surfaces produces a negative ion current evolution compatible with experimental findings. In the same conditions, the attachment rate overshoot is found to contribute about 7% to the average ion density in the plasma.

Diomede, P.; Longo, S.; Capitelli, M. [Dipartimento di Chimica dell'Universita di Bari, Via Orabona 4, 70126 Bari, Italy and IMIP/CNR, Via Orabona 4, 70126 Bari (Italy)

2006-11-15

104

Age differences in plasma norepinephrine kinetics in humans  

SciTech Connect

To determine if the increased plasma norepinephrine (NE) of older individuals is due to greater plasma NE appearance rate and/or decreased NE clearance, arterialized plasma NE kinetics were measured in 25 healthy young (27 +/- 6 yr, M +/- SD) and 18 healthy older volunteers (68 +/- 5 yr) using a tritium-labeled NE isotope dilution technique. Basal NE levels were 54% greater in the older participants (282 +/- 24 vs. 183 +/- 11 pg/ml, M +/- SEM, p less than .001). The mean plasma NE appearance rate was 32% higher (0.33 +/- 0.03 vs. 0.25 +/- 0.02 microgram/m2/min, p less than .016) and NE clearance was 19% lower (1.21 +/- 0.08 vs. 1.49 +/- 0.06 L/min/m2, p less than .006) in the older participants. There was a close correlation between NE appearance rate and NE levels (r = .76, p less than .001, N = 43), but only modest inverse correlation between NE clearance and NE levels (r = -.37, p less than .01, N = 43). Stepwise multiple linear regression analysis revealed that NE appearance rate and clearance explained 80% of the variance in NE levels and that 57% of the variance was attributable to NE appearance, F (1,41) = 54.8, p less than .001, compared with only 14% by NE clearance, F (1, 41) = 6.5, p = .01. We conclude that the principal factor accounting for the higher plasma NE levels of older individuals is an increase in plasma NE appearance rate.

Veith, R.C.; Featherstone, J.A.; Linares, O.A.; Halter, J.B.

1986-05-01

105

ASPEN: A Fully Kinetic, Reduced-Description Particle-in-Cell Model for Simulating Parametric Instabilities  

NASA Astrophysics Data System (ADS)

A fully kinetic, reduced-description particle-in-cell (RPIC) model is presented in which deviations from quasineutrality, electron and ion kinetic effects, and nonlinear interactions between low-frequency and high-frequency parametric instabilities are modeled correctly. The model is based on a reduced description where the electromagnetic field is represented by three separate temporal envelopes in order to model parametric instabilities with low-frequency and high-frequency daughter waves. Because temporal envelope approximations are invoked, the simulation can be performed on the electron time scale instead of the time scale of the light waves. The electrons and ions are represented by discrete finite-size particles, permitting electron and ion kinetic effects to be modeled properly. The Poisson equation is utilized to ensure that space-charge effects are included. The RPIC model is fully three dimensional and has been implemented in two dimensions on the Accelerated Strategic Computing Initiative (ASCI) parallel computer at Los Alamos National Laboratory, and the resulting simulation code has been named ASPEN. We believe this code is the first particle-in-cell code capable of simulating the interaction between low-frequency and high-frequency parametric instabilites in multiple dimensions. Test simulations of stimulated Raman scattering, stimulated Brillouin scattering, and Langmuir decay instability are presented.

Vu, H. X.; Bezzerides, B.; Dubois, D. F.

1999-11-01

106

Approximate analytical description of the underdense short plasma lens  

SciTech Connect

The perturbative approach for describing the underdense plasma-ultrarelativistic electron bunch system is developed, using the ratio n{sup o}{sub b} as a small parameter (n{sub b}-bunch, n{sub o} plasma electron densities). Focusing of the electron bunch emerged in the first approximation of the perturbative procedure as a result of the plasma electrons redistribution. Focusing gradient and strength for ultrarelativistic, flat, uniform and short bunch are obtained and compared with the previous results.

Amatuni, A.Ts. [Yerevan Physics Institute (Armenia)

1996-05-01

107

Complex (dusty) plasmas-kinetic studies of strong coupling phenomena  

SciTech Connect

'Dusty plasmas' can be found almost everywhere-in the interstellar medium, in star and planet formation, in the solar system in the Earth's atmosphere, and in the laboratory. In astrophysical plasmas, the dust component accounts for only about 1% of the mass, nevertheless this component has a profound influence on the thermodynamics, the chemistry, and the dynamics. Important physical processes are charging, sputtering, cooling, light absorption, and radiation pressure, connecting electromagnetic forces to gravity. Surface chemistry is another important aspect. In the laboratory, there is great interest in industrial processes (e.g., etching, vapor deposition) and-at the fundamental level-in the physics of strong coupling phenomena. Here, the dust (or microparticles) are the dominant component of the multi-species plasma. The particles can be observed in real time and space, individually resolved at all relevant length and time scales. This provides an unprecedented means for studying self-organisation processes in many-particle systems, including the onset of cooperative phenomena. Due to the comparatively large mass of the microparticles (10{sup -12}to10{sup -9}g), precision experiments are performed on the ISS. The following topics will be discussed: Phase transitions, phase separation, electrorheology, flow phenomena including the onset of turbulence at the kinetic level.

Morfill, Gregor E.; Ivlev, Alexei V.; Thomas, Hubertus M. [Max-Planck-Institut fuer Extraterrestrische Physik, D-85740 Garching (Germany)

2012-05-15

108

Electromagnetic effects of kinetic geodesic acoustic mode in tokamak plasmas  

SciTech Connect

Electromagnetic effects of the kinetic geodesic acoustic modes (KGAMs) are numerically studied in low {beta}(= plasma pressure/magnetic pressure) tokamak plasmas. The parallel component of the perturbed vector potential is considered along with the electrostatic potential perturbation. The finite Larmor radius and finite orbit width of the ions as well as electron parallel dynamics are all taken into account. Systematic harmonic and ordering analysis is performed for collisionless damping of the KGAMs, assuming {beta}{approx}({kappa}{rho}{sub i}){sup 2}, where {kappa}and {rho}{sub i}are the radial component of the KGAM wave vector and the Larmor radius of the ions, respectively. It is found that the electron parallel dynamics enhances the damping of the electrostatic KGAM modes when the safety factor q is high. In addition, the electromagnetic (finite {beta} effect is revealed to enhance and weaken the damping of the modes in plasmas of low and high safety factor q{approx}2.0 and 5.5, respectively. The harmonic features of the KGAMs are discussed as well.

Wang Lingfeng; Shen, Y.; He, H. D. [Southwestern Institute of Physics, Chengdu 610041 (China); Dong, J. Q. [Southwestern Institute of Physics, Chengdu 610041 (China); Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China)

2011-05-15

109

Kinetic studies of microinstabilities in toroidal plasmas: Simulation and theory  

SciTech Connect

A comprehensive program for the development and use of particle simulation techniques for solving the gyrokinetic Vlasov-Maxwell equations on massively parallel computers has been carried out at Princeton Plasma Physics Laboratory. This is a key element of our ongoing theoretical efforts to systematically investigate physics issues vital to understanding tokamak plasmas. In this paper, our focus is on spatial-gradient-driven microinstabilities. Their importance is supported by the recent progress in achieving a physics-based understanding of anomalous transport in toroidal systems which has been based on the proposition that these drift-type electrostatic modes dependent on ion temperature gradient (ITG) and trapped particle effects are dominant in the bulk ( confinement'') region. Although their presence is consistent with a number of significant confinement trends, results from high temperature tokamaks such as TFTR have highlighted the need for better insight into the nonlinear properties of such instabilities in long-mean-free-path plasmas. In addressing this general issue, we report important new results including (i) the first fully toroidal 3D gyrokinetic simulation of ITG modes and (ii) realistic toroidal eigenmode calculations demonstrating the unique capability to deal with large scale kinetic behavior extending over many rational surfaces. The effects of ITG modes (iii) on the inward pinch of impurities in 3D slab geometry and (iv) on the existence of microtearing modes in 2D slab are also discussed. Finally, (v) sheared toroidal flow effects on trapped-particle modes are presented.

Lee, W.W.; Haham, T.S.; Parker, S.E.; Perkins, F.W.; Rath, S.; Rewoldt, G.; Reynders, J.V.W.; Santoro, R.A.; Tang, W.M.

1992-12-01

110

Kinetic studies of microinstabilities in toroidal plasmas: Simulation and theory  

SciTech Connect

A comprehensive program for the development and use of particle simulation techniques for solving the gyrokinetic Vlasov-Maxwell equations on massively parallel computers has been carried out at Princeton Plasma Physics Laboratory. This is a key element of our ongoing theoretical efforts to systematically investigate physics issues vital to understanding tokamak plasmas. In this paper, our focus is on spatial-gradient-driven microinstabilities. Their importance is supported by the recent progress in achieving a physics-based understanding of anomalous transport in toroidal systems which has been based on the proposition that these drift-type electrostatic modes dependent on ion temperature gradient (ITG) and trapped particle effects are dominant in the bulk (``confinement``) region. Although their presence is consistent with a number of significant confinement trends, results from high temperature tokamaks such as TFTR have highlighted the need for better insight into the nonlinear properties of such instabilities in long-mean-free-path plasmas. In addressing this general issue, we report important new results including (i) the first fully toroidal 3D gyrokinetic simulation of ITG modes and (ii) realistic toroidal eigenmode calculations demonstrating the unique capability to deal with large scale kinetic behavior extending over many rational surfaces. The effects of ITG modes (iii) on the inward pinch of impurities in 3D slab geometry and (iv) on the existence of microtearing modes in 2D slab are also discussed. Finally, (v) sheared toroidal flow effects on trapped-particle modes are presented.

Lee, W.W.; Haham, T.S.; Parker, S.E.; Perkins, F.W.; Rath, S.; Rewoldt, G.; Reynders, J.V.W.; Santoro, R.A.; Tang, W.M.

1992-12-01

111

Chemical kinetics study of a nanosecond pulsed He-O2 plasma Jet  

NASA Astrophysics Data System (ADS)

Atmospheric-pressure, nanosecond pulsed plasma jets have shown promising applications in biomedical and dental fields. In order to better understand the mechanisms associated to the plasma processes, a zero-dimensional plasma chemistry model was used to study the chemical kinetics of an atmospheric-pressure, nanosecond pulsed He-O2 plasma jet. Density kinetics of the charged and neutral species in the plasma jet as a function of the input parameters including the oxygen concentration and the electric field are calculated. The roles played by different reactions in the kinetics schemes are assessed. In addition, both of He-O2 and He-O2-N2 plasma chemical kinetics reaction schemes are discussed to examine the effects of air entrainment on the characteristics of the plasma jet.

Xia, Shengguo; Jiang, Chunqi

2011-11-01

112

Kinetic Simulations of Collisionless Reconnection in Pair Plasmas  

NASA Astrophysics Data System (ADS)

Despite a great deal of research effort, many basic issues regarding collisionless reconnection remain poorly understood. Although fully kinetic simulations offer a first principles approach, the large separation between electron and ion spatial and temporal scales has severally limited these computational studies. In contrast, the problem of magnetic reconnection in an electron-positron plasma is feasible in both 2D and 3D. It has been suggested that reconnection in pair plasmas may be of interest to certain astrophysical problems. Furthermore, this limit is useful to consider in the effort to understand the essential physics of magnetic reconnection, since there is no scale separation and it can be shown analytically that there are no whistler waves. In this work, we first examine the limit of large-scale 2D systems. Consistent with recent publications, it is demonstrated that reconnection rates remain fast for very large systems but a steady-state is never achieved. Instead the reconnection dynamics proceeds by the repeated formation of secondary islands as the diffusion region expands. From linear Vlasov theory, the unstable eigenmodes in a pair plasma include collisionless tearing and the drift-kink mode. In 3D simulations, the box length in the direction of the current can be selected to either permit or exclude the drift-kink. In the limit where the box length is short enough to exclude the drift-kink mode, reconnection proceeds essentially in the same manner as the 2D simulations. However, when the simulation box is long enough to allow the drift-kink mode, the reconnection dynamics change dramatically with complicated 3D structures resulting from the nonlinear interaction between collisionless tearing and drift-kink. These results may have some relevance to reconnection in hydrogen plasmas since the drift-kink mode is replaced by the ion-ion kink mode at high mass ratio.

Yin, L.; Daughton, W.; Bowers, K. J.

2007-05-01

113

Kinetic modeling of plasma methane conversion in a dielectric barrier discharge  

Microsoft Academic Search

Methane conversion by plasma offers a promising route to produce higher value-added products. As plasma reaction is a relatively complex process, kinetic modeling is necessary to obtain a general pattern of the complex interaction on the basis of chemical reaction and products. In this paper, we present a method to obtain the kinetic rate coefficient (k) from the experimental data.

Antonius Indartoa; Nowarat Coowanitwong; Jae-Wook Choi; Hwaung Lee; Hyung Keun Song

2008-01-01

114

REVIEWS OF TOPICAL PROBLEMS: Nonlocal electron kinetics in gas-discharge plasma  

NASA Astrophysics Data System (ADS)

The field of electron kinetics in extremely nonequilibrium glow discharge plasma is reviewed, starting from the classical works of Langmuir. It is shown that it is only in terms of kinetics that many aspects of nonequilibrium plasma — such as the structure of near-electrode regions, spatial profiles of ionization and luminosity, striations and particle and energy flows — can be adequately understood.

Tsendin, Lev D.

2010-05-01

115

Advances in petascale kinetic plasma simulation with VPIC and Roadrunner  

SciTech Connect

VPIC, a first-principles 3d electromagnetic charge-conserving relativistic kinetic particle-in-cell (PIC) code, was recently adapted to run on Los Alamos's Roadrunner, the first supercomputer to break a petaflop (10{sup 15} floating point operations per second) in the TOP500 supercomputer performance rankings. They give a brief overview of the modeling capabilities and optimization techniques used in VPIC and the computational characteristics of petascale supercomputers like Roadrunner. They then discuss three applications enabled by VPIC's unprecedented performance on Roadrunner: modeling laser plasma interaction in upcoming inertial confinement fusion experiments at the National Ignition Facility (NIF), modeling short pulse laser GeV ion acceleration and modeling reconnection in magnetic confinement fusion experiments.

Bowers, Kevin J [Los Alamos National Laboratory; Albright, Brian J [Los Alamos National Laboratory; Yin, Lin [Los Alamos National Laboratory; Daughton, William S [Los Alamos National Laboratory; Roytershteyn, Vadim [Los Alamos National Laboratory; Kwan, Thomas J T [Los Alamos National Laboratory

2009-01-01

116

Self-consistent multidimensional electron kinetic analysis for inductively coupled plasma sources  

Microsoft Academic Search

Based upon the kinetic equations coupled with electromagnetic analysis for the recently developed inductively coupled plasma sources (ICPS), a self-consistent electron kinetic model is presented for 2-D (r, z) in a cylindrically symmetric configuration space and 2-D (? ?, ?z) in the velocity space, The EM model is based on the mode analysis, while the kinetic analysis gives the perturbed

Fa Dai; C.-H. J. Wu

1995-01-01

117

Kinetic development of crystallization fronts in complex plasmas  

NASA Astrophysics Data System (ADS)

Although it is relatively straightforward to measure the atomic structure of crystals, the detailed dynamics of crystal growth (including the evolution of self-organization, structure formation, and the associated kinetic and thermodynamic development) remains one of the most important topics of solid-state physics. Very little is known, for instance, about the evolutionary paths of crystal structure development, and the structural complexity of the surface down to atomic dimensions and its change with time. This is, to a large extent, due to the lack of suitable systems that can be studied at the appropriate length- and timescales. Here, we report experimental observations of a crystallization front propagating in a supercooled region of a three-dimensional fluid complex plasma. The structure and evolution of the front are analysed using kinetic measurements of individual microparticle dynamics. It is found that the fluid-crystalline transition is accompanied by short-lived `nano'-crystallites in the fluid and `nano'-droplets in the crystalline phases, that the surface structure is scale-free (fractal) in the experimentally accessible regime (2-10 lattice distances) and that crystal growth follows a universal self-organization pattern at the particle level, leading to oscillations in the surface roughness.

Rubin-Zuzic, M.; Morfill, G. E.; Ivlev, A. V.; Pompl, R.; Klumov, B. A.; Bunk, W.; Thomas, H. M.; Rothermel, H.; Havnes, O.; Fouquét, A.

2006-03-01

118

PLASMAKIN: A chemical kinetics library for plasma physics modeling  

NASA Astrophysics Data System (ADS)

PLASMAKIN is a software library to handle physical and chemical data used in plasma physics modeling and to compute kinetics data from the reactions taking place in the gas or at the surfaces - particle generation and loss rates, photon emission rates and energy exchange rates. PLASMAKIN supports any number of chemical species and reactions, is independent of problem dimensions and can be used both in stationary and time-dependent problems. PLASMAKIN supports a large number of species properties and reaction types. Namely gas or electron temperature dependent collision rate coefficients, vibrational and cascade levels, evaluation of branching ratios, superelastic and other reverse processes, three-body collisions, radiation imprisonment and photoelectric emission. Non-standard rate coefficient functions can be handled by a user supplied routine. The interaction of the user with the library is limited to the preparation of an input file characterizing the interacting species and reactions, accessing the data or the chemical kinetics results through a reduced number of procedure calls with similar interfaces. PLASMAKIN allows the user to concentrate on the physical nature of the problems independently of the gas mixture properties and reactions model. As an example a program has been prepared to evaluate the maintenance field, equilibrium populations, relative contribution of each reaction, photon emission spectra and the energy losses rates on the positive column region of a discharge in electropositive gases. The program is applied to a discharge in neon. The library is written in Fortran 95 and has error support.

Pinha~o, N. R.

2001-03-01

119

ASPEN: A Fully Kinetic, Reduced-Description Particle-in-Cell Model for Modeling Parametric Instabilities  

NASA Astrophysics Data System (ADS)

A fully kinetic, reduced-description particle-in-cell (RPIC) model is presented in which deviations from quasineutrality, electron and ion kinetic effects, and nonlinear interactions between low-frequency and high-frequency parametric instabilities are modeled correctly. The model is based on a reduced description where the electromagnetic field is represented by three separate temporal WKB envelopes in order to model low-frequency and high-frequency parametric instabilities. Because temporal WKB approximations are invoked, the simulation can be performed on the electron time scale instead of the time scale of the light waves. The electrons and ions are represented by discrete finite-size particles, permitting electron and ion kinetic effects to be modeled properly. The Poisson equation is utilized to ensure that space-charge effects are included. Although RPIC is fully three dimensional, it has been implemented in only two dimensions on a CRAY-T3D with 512 processors and on the Accelerated Strategic Computing Initiative (ASCI) parallel computer at Los Alamos National Laboratory, and the resulting simulation code has been named ASPEN. Given the current computers available to the authors, one and two dimensional simulations are feasible to, and have been, performed. Three dimensional simulations are much more expensive, and are not feasible at this time. However, with rapidly advancing computer technologies, three dimensional simulations may be feasible in the near future. We believe this code is the first PIC code capable of simulating the interaction between low-frequency and high-frequency parametric instabilites in multiple dimensions. Test simulations of stimulated Raman scattering (SRS), stimulated Brillouin scattering (SBS), and Langmuir decay instability (LDI), are presented.

Vu, H. X.; Bezzerides, B.; Dubois, D. F.

1998-11-01

120

Fluid and kinetic models of the low temperature H{sub 2} plasma produced by a radio-frequency reactor  

SciTech Connect

A comparative study of two models, a kinetic and a fluid one, for the numerical simulation of H{sub 2} plasmas in parallel plate capacitively coupled rf discharges in one space dimension is presented. Both models adopt a multicomponent plasma description including several ionic species, take into account the self-consistent electric field by solving the Poisson equation and include a self-consistent coupling with the vibrational kinetics of the electronic ground state of H{sub 2} molecules. The peculiarities of this particular test case for model comparison with respect to previous studies are highlighted. The merits and the limitations of both approaches are discussed and the results are compared, in particular the steady-state density of charged species, the space-time variation of the electron energy, the vibrational distribution, and the atomic density.

Diomede, P. [Dipartimento di Chimica dell'Universita' di Bari, Via Orabona 4, 70126 Bari (Italy); Michau, A.; Redolfi, M.; Hassouni, K. [LIMHP, CNRS-UPR 1311, Institut Galilee-Universite Paris 13, 99 Avenue J. B. Clement, 93430 Villetaneuse (France); Morscheidt, W. [LGPPTS, ENSCP-Universite Pierre et Marie Curie, 11 Rue Pierre et Marie Curie, 75005 Paris (France); Longo, S.; Capitelli, M. [Dipartimento di Chimica dell'Universita' di Bari, Via Orabona 4, 70126 Bari (Italy); IMIP/CNR, Via Orabona 4, 70126 Bari (Italy)

2008-10-15

121

Numerical description of discharge characteristics of the plasma needle  

SciTech Connect

The plasma needle is a small atmospheric, nonthermal, radio-frequency discharge, generated at the tip of a needle, which can be used for localized disinfection of biological tissues. Although several experiments have characterized various qualities of the plasma needle, discharge characteristics and electrical properties are still not well known. In order to provide initial estimates on electrical properties and quantities such as particle densities, we employed a two-dimensional, time-dependent fluid model to describe the plasma needle. In this model the balance equation is solved in the drift-diffusion approach for various species and the electron energy, as well as Poisson's equation. We found that the plasma production occurs in the sheath region and results in a steady flux of reactive species outwards. Even at small (<0.1%) admixtures of N{sub 2} to the He background, N{sub 2}{sup +} is the dominant ion. The electron density is typically 10{sup 11} cm{sup -3} and the dissipated power is in the order of 10 mW. These results are consistent with the experimental data available and can give direction to the practical development of the plasma needle.

Brok, W.J.M.; Bowden, M.D.; Dijk, J. van; Mullen, J.J.A.M. van der; Kroesen, G.M.W. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven (Netherlands)

2005-07-01

122

Electrical and kinetic model of an atmospheric rf device for plasma aerodynamics applications  

SciTech Connect

The asymmetrically mounted flat plasma actuator is investigated using a self-consistent two-dimensional fluid model at atmospheric pressure. The computational model assumes the drift-diffusion approximation and uses a simple plasma kinetic model. It investigated the electrical and kinetic properties of the plasma, calculated the charged species concentrations, surface charge density, electrohydrodynamic forces, and gas speed. The present computational model contributes to understand the main physical mechanisms, and suggests ways to improve its performance.

Pinheiro, Mario J. [Department of Physics, Institute for Plasma and Nuclear Fusion, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Martins, Alexandre A. [Institute for Plasma and Nuclear Fusion, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal)

2010-08-15

123

Molecular Dynamics Description of Partially Ionized Dense Plasmas  

NASA Astrophysics Data System (ADS)

A report on work in progress: the approach to steady-state of partially ionized dense plasmas, containing more than one atomic element, is being simulated with the quasi-classical method known as Fermi Molecular Dynamics (FMD). We recap the FMD method, recalling its several advantages and disadvantages, and present an overview of past work. we have continued to develop the FMD method as a tool for simulating the behaviors of a variety of inhomogeneous, partially ionized, dense plasma systems, in cases for which more rigorous methods are still unavailable. Predictions of the average ionization state Z* of atoms, in a plasma containing more than one atomic element, is complicated by many factors, especially under conditions of high density, and not too high temperature. Average atom models become problematic when two or more atomic elements are present together. In order to address this problem, we have applied the FMD method to plasmas containing selected mixtures of atomic elements, determining Z* for each element over a range of temperatures and densities. LANL archived abstract: LA-UR-04-2186

Lagattuta, Ken

2004-11-01

124

Porting fluid and kinetic plasma models for space plasma physics to heterogeneous architectures: Benefits and Challenges (Invited)  

NASA Astrophysics Data System (ADS)

Advances in processor technology provide the opportunity to simulate space plasma dynamics at unprecedented resolution. As processor clock speeds have begun to plateau in recent years, new technologies have emerged that maintain exponential growth in computational capability, in particular multi-core processors and heterogeneous approaches to computing, e.g., the STI Cell processor and general purpose GPUs. We will discuss two projects that aim at porting existing codes to efficiently run on heterogeneous processors. The Particle Simulation Code (PSC) is a 3D fully electromagnetic particle-in-cell code, solving the kinetic plasma equations, including a collision operator. This code is applied to problems requiring a kinetic model, like particle acceleration and modeling the microscopic structure of a reconnecting current sheets. We will discuss the performance gains enabled by porting the code to NVIDIA's GPU CUDA programming environment, as well as the challenges in exploiting the full capabilities of GPUs for the current deposition step. OpenGGCM is a community global magnetosphere model. The main computational challenge is the solution of the 3D MHD equations which are discretized using finite-difference / finite-volume. We ported this code to the Cell processor using a novel code generator. This approach allows us to specify the discretized equations in near-symbolic form as a stencil computation, and then have highly-optimized code be generated automatically. From the same description we are able to generate plain C code, C code with SIMD/SSE2 extensions and code for the Cell processor, yielding significant performance gains. We will also present first results of a new extension to the code generator that creates CUDA code for GPUs.

Germaschewski, K.; Raeder, J.; Ruhl, H.

2010-12-01

125

Kinetic and Fluid Modelling of Plasmas: Energetic Beams and Tilt Stability in Field Reversed Configurations  

Microsoft Academic Search

Plasma problems include features on disparate scales. One example is the dynamical coupling of the microscopic details of individual particle motion to the macroscopic plasma flow. A small energetic particle component can modify the low frequency fluid response of a plasma. This work extends fluid models to include a minority component of energetic kinetic particles and applies it to the

John Winston Cobb

1993-01-01

126

Variational formulation of particle algorithms for kinetic plasma simulations  

NASA Astrophysics Data System (ADS)

Common time-explicit numerical methods for kinetic simulations of plasmas in the low-collisions limit fall into two classes of algorithms: momentum conserving (also known as particle-in-cell (PIC)) and energy conserving. Each has certain drawbacks. The PIC algorithm does not conserve total energy, which may lead to spurious numerical heating (grid heating). Its overall accuracy is at most second due to the nature of the force interpolation between grid and particle position. Energy-conserving algorithms do not exhibit grid heating, but because their formulation uses potentials, computationally undesirable matrix inversions may be necessary. In addition, compared to PIC algorithms for the same accuracy, these algorithms have higher numerical noise due to the restricted choice of particle shapes. Here we formulate time-explicit, finite-size particle algorithms using particular reductions of the particle distribution function. These reductions are used in two variational principles, a Lagrangian-based and a Hamiltonian-based in conjunction with a non-canonical Poisson bracket. The Lagrangian formulations here generalize previous such formulations. The Hamiltonian formulation is presented here for the first time. Many drawbacks of the two classes of particle methods are mitigated. For example, restrictions on particle shapes are relaxed in energy conserving algorithms, which can decrease the numerical noise in these methods. The Hamiltonian formulation of particle algorithms is done in terms of fields instead of potentials, thus avoiding solving Poisson's equation. An algorithm that conserves both energy and momentum is presented. Other features of the algorithms include a natural way to perform coordinate transformations, the use of various time integrating methods, and the ability to increase the overall accuracy beyond second order, including all generalizations. For clarity of presentation, we restrict our discussion to one-dimensional, non-relativistic, unmagnetized, electrostatic plasmas.

Evstatiev, E. G.; Shadwick, B. A.

2013-07-01

127

SOLAR WIND TURBULENT SPECTRUM AT PLASMA KINETIC SCALES  

SciTech Connect

The description of the turbulent spectrum of magnetic fluctuations in the solar wind in the kinetic range of scales is not yet completely established. Here, we perform a statistical study of 100 spectra measured by the STAFF instrument on the Cluster mission, which allows us to resolve turbulent fluctuations from ion scales down to a fraction of electron scales, i.e., from {approx}10{sup 2} km to {approx}300 m. We show that for k {rho} {sub e} in [0.03, 3] (which corresponds approximately to the frequency in the spacecraft frame f in [3, 300] Hz), all the observed spectra can be described by a general law E(k ){proportional_to}k {sup -8/3} exp (- k {rho} {sub e}), where k is the wavevector component normal to the background magnetic field and {rho} {sub e} the electron Larmor radius. This exponential tail found in the solar wind seems compatible with the Landau damping of magnetic fluctuations onto electrons.

Alexandrova, O.; Lacombe, C.; Mangeney, A.; Maksimovic, M. [LESIA-Observatoire de Paris, CNRS, UPMC Universite Paris 06, Universite Paris-Diderot, 5 place J. Janssen, F-92190 Meudon (France); Grappin, R. [LUTH-Observatoire de Paris, CNRS, Universite Paris-Diderot, 5 place J. Janssen, F-92190 Meudon (France)

2012-12-01

128

PLASMAKIN: A chemical kinetics library for plasma physics modeling  

NASA Astrophysics Data System (ADS)

PLASMAKIN is a package to handle physical and chemical data used in plasma physics modeling and to compute kinetics data from the reactions taking place in the gas or at the surfaces: particle production and loss rates, photon spectra and energy exchange rates. It has no limits on the number of species and reactions that can be handled, is independent of problem dimensions and can be used in both steady-state and time-dependent problems. A broad range of species properties and reaction types are supported: gas or electron temperature dependent rate coefficients, vibrational and cascade levels, branching ratios, superelastic and other reverse processes, three-body collisions, radiation imprisonment and photoelectric emission. Non-standard rate coefficient functions can be handled by a user-supplied shared library. Reaction data is supplied in text files and is independent of the user's program. Recent additions include the simulation of emission spectra taking line broadening into account; reactions with excited ionic species; 3-body reactions with species with different efficiencies as 3rd body; a species properties database and a Python interface for rapid scripting and debugging.

Pinhao, Nuno

2007-10-01

129

Current Sheets and Collisionless Damping in Kinetic Plasma Turbulence  

NASA Astrophysics Data System (ADS)

We present the first study of the formation and dissipation of current sheets at electron scales in a wave-driven, weakly collisional, three-dimensional kinetic turbulence simulation. We investigate the relative importance of dissipation associated with collisionless damping via resonant wave-particle interactions versus dissipation in small-scale current sheets in weakly collisional plasma turbulence. Current sheets form self-consistently from the wave-driven turbulence, and their filling fraction is well correlated to the electron heating rate. However, the weakly collisional nature of the simulation necessarily implies that the current sheets are not significantly dissipated via Ohmic dissipation. Rather, collisionless damping via the Landau resonance with the electrons is sufficient to account for the measured heating as a function of scale in the simulation, without the need for significant Ohmic dissipation. This finding suggests the possibility that the dissipation of the current sheets is governed by resonant wave-particle interactions and that the locations of current sheets correspond spatially to regions of enhanced heating.

TenBarge, J. M.; Howes, G. G.

2013-07-01

130

Existence of Weakly Damped Kinetic Alfven Eigenmodes in Reversed Shear Tokamak Plasmas.  

National Technical Information Service (NTIS)

A kinetic theory of weakly damped Alfven Eigenmode (AE) solutions strongly interacting with the continuum is developed for tokamak plasmas with reversed magnetic shear. We show that the ideal MHD model is not sufficient for the eigenmode solutions if the ...

N. N. Gorelenkov

2008-01-01

131

Initial measurement of the kinetic dust temperature of a weakly coupled dusty plasma  

SciTech Connect

Measurements of the velocity space distribution function of 2.9 {mu}m diameter silica particles in an argon dc glow discharge dusty plasma are made through the use of stereoscopic particle image velocimetry (stereo-PIV). These distribution functions are then used to determine the kinetic temperature of the dust component. These measurements show that the kinetic temperature of the dust component is significantly larger than the other plasma components (electrons, ions, and background neutrals)

Williams, Jeremiah D.; Thomas, Edward Jr. [Department of Physics, Auburn University, Auburn, Alabama 36849 (United States)

2006-06-15

132

Generation of kinetic Alfven waves by beam-plasma interaction in non-uniform plasma  

SciTech Connect

This work reports a novel mechanism of the generation of kinetic Alfven waves (KAWs) using a two-dimensional hybrid simulation: the KAWs are generated by ion beam-plasma interaction in a non-uniform plasma boundary layer, in which the bulk velocity of the ion beam is assumed to be parallel to the ambient magnetic field. As a result of the beam-plasma interaction, strong shear Alfven waves as well as fast mode compressional waves are first generated on the side of the boundary layer with a high density and thus a low Alfven speed, propagating along the background magnetic field. Later, Alfven waves also form inside the boundary layer with a continuous spectrum. As the perpendicular wave number k{sub Up-Tack} of these unstably excited waves increases with time, large-amplitude, short wavelength KAWs with k{sub Up-Tack } Much-Greater-Than k{sub ||} clearly form in the boundary layer. The physics for the generation of KAWs is discussed.

Hong, M. H. [Institute of Geology and Geophysics, CAS, Beijing 100029 (China); Lin, Y. [Physics Department, Auburn University, Auburn, Alabama 36849-5311 (United States); Department of Geophysics and Planetary Science, USTC, Hefei 230026 (China); Wang, X. Y. [Physics Department, Auburn University, Auburn, Alabama 36849-5311 (United States)

2012-07-15

133

Kinetic parameters for plasma. beta. -endorphin in lean and obese Zucker rats  

SciTech Connect

To determine plasma clearance kinetics for {beta}-endorphin (BE) by empirical compartmental analysis, a bolus of radioactive labeled 125I-BE was rapidly injected into a carotid artery catheter of unanesthetized lean (L) and obese (O) Zucker rats. The plasma disappearance of 125I was followed over a 3-h period. A 3-component exponential equation provided the best fit for plasma data. Plasma transit times were very short (10 s); however, plasma fractional catabolic rate was much slower. Plasma mean residence time was similar for both groups (50 min) as was recycle time (1.3 min). These data suggest that BE plasma disappearance kinetics are similar in L and O rats.

Rodd, D.; Farrell, P.A.; Caston, A.L.; Green, M.H. (Department of Exercise and Sport Science, Pennsylvania State University, University Park (USA))

1991-03-01

134

Kinetic extensions of magnetohydrodynamics for axisymmetric toroidal plasmas  

NASA Astrophysics Data System (ADS)

A nonvariational kinetic-MHD stability code (NOVA-K) has been developed to integrate non-Hermitian integro-differential eigenmode equations due to energetic particles in a general flux coordinate (?, ?, ?) system with an arbitrary Jacobian. The NOVA-K code employs the Galerkin method involving Fourier expansions in the generalized poloidal angle ? and generalized toroidal angle ? directions, and cubic-B spline finite elements in the radial ? direction. Extensive comparisons with the existing variational ideal MHD codes show that the NOVA-K code coverages faster and gives more accurate results. We have employed the NOVA-K code to study the effects of energetic particles on MHD type modes: (1) the stabilization of ideal MHD internal kink modes and the excitation of ``fishbone'' internal kink modes; (2) the ?-particle destabilization of toroidicity-induced Alfvén eigenmodes (TAE) via transit and/or trapped particle resonances. Analytical theories are also presented to help explain the NOVA-K results. For energetic trapped particles generated by neutral-beam injection (NBI) and ion cyclotron resonant heating (ICRH) a stability window for the n = 1 internal kink mode in the hot particle beta space exists. On the other hand, the trapped ?-particles can resonantly destabilize the n = 1 resonant fishbone mode even for total plasma ? value smaller than the ? threshold value for the n = 1 ideal internal kink mode. Finally, we show that the TAE modes can be destabilizedby ?-particles via inverse Landau damping associated with the spatial gradient of the ?-particle pressure with very low ?-particle ? threshold in the order of 10-4 for major tokamak DT experiments.

Cheng, C. Z.

1992-02-01

135

Kinetic extensions of magnetohydrodynamic models for axisymmetric toroidal plasmas  

SciTech Connect

A nonvariational kinetic-MHD stability code (NOVA-K) has been developed to integrate a set of non-Hermitian integro-differential eigenmode equations due to energetic particles for axisymmetric toroidal plasmas in a general flux coordinate system with an arbitrary Jacobian. The NOVA-K code employs the Galerkin method involving Fourier expansions in the generalized poloidal angle theta and generalized toroidal angle /zeta/ directions, and cubic-B spline finite elements in the radial /Psi/ direction. Extensive comparisons with the existing variational ideal MHD codes show that the ideal MHD version of the NOVA-K code converges faster and gives more accurate results. The NOVA-K code is employed to study the effects of energetic particles on MHD-type modes: the stabilization of ideal MHD internal kink modes and the excitation of ''fishbone'' internal kink modes; and the alpha particle destabilization of toroidicity-induced Alfven eigenmodes (TAE) via transit resonances. Analytical theories are also presented to help explain the NOVA-K results. For energetic trapped particles generated by neutral beam injection (NBI) or ion cyclotron resonant heating (ICRH), a stability window for the n = 1 internal kink mode in the hot particle beta space exists even in the absence of the core ion finite Larmor radius effect. On the other hand, the trapped alpha particles are found to have negligible effects on the stability of the n = 1 internal kink mode, but the circulating alpha particles can strongly destabilize TAE modes via inverse Landau damping associated with the spatial gradient of the alpha particle pressure. 60 refs., 24 figs., 1 tab.

Cheng, C.Z.

1989-04-01

136

Non-Markovian renormalization of kinetic coefficients for drift-type turbulence in magnetized plasmas  

SciTech Connect

The problem of derivation of the kinetic equations for inhomogeneous plasma in an external magnetic field is considered. The Fokker-Planck-type equations with the non-Markovian kinetic coefficients are proposed. In the time-local limit (small correlation times with respect to the distribution function relaxation time) the relations obtained recover the results known from the appropriate quasilinear theory and the Dupree-Weinstock theory of plasma turbulence. Kinetic calculations of the dielectric response function are also performed with regard to the influence of turbulent fields on particle motion. The equations proposed are used to describe zonal flow generation and to estimate the diffusion coefficient for saturated turbulence.

Zagorodny, A.; Weiland, J. [Bogolyubov Institute for Theoretical Physics, Kiev (Ukraine)

2009-05-15

137

Observation of Kinetic Plasma Jets in a Coronal-Loop Simulation Experiment  

SciTech Connect

Under certain conditions an intense kinetic plasma jet is observed to emerge from the apex of laboratory simulations of coronal plasma loops. Analytic and numerical models show that these jets result from a particle orbit instability in a helical magnetic field whereby magnetic forces radially eject rather than confine ions with sufficiently large countercurrent axial velocity.

Tripathi, S. K. P.; Bellan, P. M.; Yun, G. S. [Applied Physics, California Institute of Technology, Pasadena, California 91125 (United States)

2007-03-30

138

Integrated Plasma-Surface Kinetics Model to Predict Deposition Rates in an HDP-CVD Reactor  

Microsoft Academic Search

A comprehensive model for HDP-CVD reactors used in semiconductor processing, such as the Novellus SPEED, remains challenging due to the complex coupling of plasma transport, gas-phase and surface chemical reaction pathways in the chamber. The Hybrid Plasma Equipment Model (HPEM) is employed here to predict deposition rates at the wafer. The HPEM has a Surface Kinetics Module (SKM) that accepts

Ananth Bhoj; Prashanth Kothnur; Ron Kinder

2008-01-01

139

Efficiency at which the kinetic energy of a hypersonic dense plasma flow is converted into light  

Microsoft Academic Search

This paper reports a study of the physics of light sources in which a plasma is heated through the randomization of the directed kinetic energy of a dense plasma stream which is accelerated electrodynamically to a hypersonic velocity and then suddenly stopped at an obstacle. This heating method is shown to have several fundamental advantages over the most common methods

A. S. Kamrukov; N. P. Kozlov; E. P. Myshelov; Iu. S. Protasov

1981-01-01

140

Kinetic effects of non-equilibrium plasma-assisted methane oxidation on diffusion flame extinction limits  

Microsoft Academic Search

The kinetic effects of low temperature non-equilibrium plasma assisted CH4 oxidation on the extinction of partially premixed methane flames was studied at 60Torr by blending 2% CH4 by volume into the oxidizer stream of a counterflow system. The experiments showed that non-equilibrium plasma can dramatically accelerate the CH4 oxidation at low temperature. The rapid CH4 oxidation via plasma assisted combustion

Wenting Sun; Mruthunjaya Uddi; Sang Hee Won; Timothy Ombrello; Campbell Carter; Yiguang Ju

141

BRIEF COMMUNICATION: On the drift kinetic equation driven by plasma flows  

NASA Astrophysics Data System (ADS)

A drift kinetic equation that is driven by plasma flows has previously been derived by Shaing and Spong 1990 (Phys. Fluids B 2 1190). The terms that are driven by particle speed that is parallel to the magnetic field B have been neglected. Here, such terms are discussed to examine their importance to the equation and to show that these terms do not contribute to the calculations of plasma viscosity in large aspect ratio toroidal plasmas, e.g. tokamaks and stellarators.

Shaing, K. C.

2010-07-01

142

Extent of validity of the hydrodynamic description of ions in dense plasmas  

SciTech Connect

We show that the hydrodynamic description can be applied to modeling the ionic response in dense plasmas for a wide range of length scales that are experimentally accessible. Using numerical simulations for the Yukawa model, we find that the maximum wave number k{sub max} at which the hydrodynamic description applies is independent of the coupling strength, given by k{sub max}{lambda}s{approx_equal}0.43, where {lambda}{sub s} is the ionic screening length. Our results show that the hydrodynamic description can be used for interpreting x-ray scattering data from fourth generation light sources and high power lasers. In addition, our investigation sheds new light on how the domain of validity of the hydrodynamic description depends on both the microscopic properties and the thermodynamic state of fluids in general.

Mithen, James P.; Gregori, Gianluca [Department of Physics, Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU (United Kingdom); Daligault, Jerome [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2011-01-15

143

Spatially intermittent kinetic range turbulence and plasma heating in fully self-consistent kinetic (PIC) simulations of reconnection  

NASA Astrophysics Data System (ADS)

Recent fully self-consistent kinetic (PIC) simulations of reconnection in three dimensions [Daughton et al, Nat. Phys, 2011] are strongly suggestive that collisionless magnetic reconnection leads to self-generation of turbulence. We investigate whether this 'turbulent reconnection', in particular when evolved on kinetic scales, does indeed proceed in a manner that shares features of its phenomenology with classical intermittent fluid turbulence. If so, this would be the first indication of a universal physics central to turbulent reconnection and would provide quantitative insights into the role that turbulence plays in plasma heating. We present the results of formal quantitative tests for reconnection driven turbulence in these fully self-consistent kinetic (PIC) simulations. In the finite sized domain of a reconnection region, one anticipates a generalized scaling, that is, Extended Self Similarity (ESS). We find the characteristic signatures of intermittent turbulence, specifically ESS and non-Gaussian pdfs of fluctuations and confirm that these show multifractal scaling, which is anisotropic. Importantly, we can distinguish this scaling from that of the correlated noise generated by the PIC simulation. We find that the scalar field J.E is also multifractal so that plasma heating is spatially intermittent, following the topology of the magnetic field fluctuations. Similarities and differences between simulations in two and three dimensions will also be discussed. This quantitative characterization of fully kinetic simulations of turbulent reconnection in terms of turbulence phenomenology also suggests tests that could be applied to in-situ satellite observations of regions where reconnection is occurring.

Leonardis, Ersilia; Chapman, Sandra; Daughton, William; Roytershteyn, Vadim; Karimabadi, Homayoun

2013-04-01

144

Simulating Electron Cyclotron Resonance Heating in Kinetic and Dielectric Plasma Models with VORPAL  

NASA Astrophysics Data System (ADS)

We present results of electron cyclotron resonance heating (ECRH) in a plasma sustained by microwaves using VORPAL. Specifically, we look at the electron temperature, sheath size, rate of plasma formation and power absorbed for simulations with an argon gas at 10s of mTorr pressure and 2.45 GHz. We look at the effects of including elastic, inelastic and ionizing Monte Carlo collisions on the formation of the kinetic plasma. We also discuss the use of higher-order particle algorithms for smoothing out the particle current and charge which can help reduce unphysical heating in PIC simulations of high pressure, low temperature plasmas and the effect this has on sheath size and electron temperature. We then compare these simulations to a method replacing the kinetic particles with an equivalent plasma dielectric model.

Roark, Christine; Smithe, David; Stoltz, Peter

2011-11-01

145

Kinetic Study of Injected Gas Effects On Divertor Plasma Detachment  

Microsoft Academic Search

Divertor plasma detachment is an important operation regime for the modern fusion devices since it can dramatically reduce the plasma energy flux load to the divertor wall. Due to its good performance for energy and impurities transport, the detachment operation regime can prolong the lifetime of the divertor wall, compared with other operation regimes. However, it is very difficult to

Tengfei Tang; Chaofeng Sang; Jizhong Sun; Dezhen Wang

146

Kinetic theory of stimulated Raman sidescattering from magnetized plasmas  

Microsoft Academic Search

A theory of stimulated Raman sidescattering in magnetized plasmas is presented based on a solution of the Vlasov–Maxwell equations. The incident laser light, in the form of extraordinary mode radiation, decays into light waves which propagate along the uniform magnetic field as right or left circularly polarized waves. The scattered plasma mode is an obliquely propagating electron-Bernstein wave. The possible

R. Rankin; T. J. M. Boyd

1985-01-01

147

Plasma kinetics of sup 125 I beta endorphin turnover in lean and obese Zucker rats  

SciTech Connect

Plasma clearance kinetics for Beta Endorphin (BEP) are not well-defined and no definitive data exist for lean versus obese animals. To determine such kinetic parameters, a bolus of {sup 125}I BEP (1{mu}Ci/kg) was infused into awake lean(L) and obese(O) Zucker rats. Arterial blood samples were withdrawn initially at 20 seconds intervals and less frequently as a 3-hour experimental period progressed. Donor rat blood was infused (venous catheter) to replace withdrawn blood. At 180 minutes approximately 10% of the initial dose remained in the plasma. Clearance kinetics for {sup 125}I BEP were analyzed by compartmental analysis. A 3-component equation (i.e., 3 compartment model) provided the best fit for both L and O groups. Plasma transit times were very rapid; however, plasma fractional catabolic rate was low. Plasma mean residence time was similar for both groups (50 minutes) as was recycle time. These data suggest that BEP kinetics are similar in L and O rats, and that this peptide may undergo extensive recycling into and out of the plasma compartment. The identity of the other two compartments requires further investigation.

Rodd, D.; Caston, A.L.; Green M.H.; Farrell, P.A. (Pennsylvania State Univ., University Park (United States))

1990-02-26

148

Charging kinetics of dust particles in a non-Maxwellian Lorentzian plasma  

NASA Astrophysics Data System (ADS)

Charging kinetics of uniformly dispersed spherical dust particles in a non-Maxwellian plasma, characterized by a Lorentzian (?) distribution function of electrons/ions has been developed; the formulation is based on the uniform potential theory, applicable to the dust particles characterized by a size distribution function. Owing the openness character of the complex plasmas, the charging kinetics has been developed on the basis of number and energy balance of the plasma constituents along with the charge balance over the dust particles; the neutrality of the complex plasma is a consequence of the number balance of electrons/ions and charge balance on the dust particles. A more rigorous approach, proposed by Mott-Smith and Langmuir [Phys. Rev. 28, 727 (1926)] has been adopted to derive the expressions for the electron/ion accretion current over the dust surface and corresponding mean energy in a non-Maxwellian Lorentzian plasma. Further the formulation has been implemented to determine the secondary electron emission (SEE) from the spherical dust particles in such plasmas. The departure of the results for the Lorentzian plasma, from that in the case of Maxwellian plasma has been graphically illustrated and discussed. It is seen that the Lorentzian nature of the plasma and the inclusion of the collective effect of the dust particles significantly affects the dust charge and other plasma parameters; the formulation and understanding of the charging kinetics in a Lorentzian plasma have implications for both the physics (e.g. grain growth and disruption) and the dynamics of dust in laboratory and space environment, when the dimension of the plasma are much larger than the diffusion length.

Mishra, Sanjay K.; Misra, Shikha; Singh Sodha, Mahendra

2013-10-01

149

Decay instability of kinetic Alfvén waves in preflare plasmas of the loops in active solar regions  

Microsoft Academic Search

We examine the physical conditions for the origin of the decay instability of kinetic Alfv?n waves in loop plasmas at the\\u000a early flare stages. The synchronism conditions are used to derive a modified expression for the nonlinear growth rate of the\\u000a process of the decay of the primary kinetic Alfv?n wave (KAW) into an ion-acoustic wave and a secondary KAW.

A. N. Kryshtal’; E. K. Sirenko; S. V. Gerasimenko

2007-01-01

150

The role of kinetic effects, including plasma rotation and energetic particles, in resistive wall mode stability  

SciTech Connect

The resistive wall mode (RWM) instability in high-beta tokamaks is stabilized by energy dissipation mechanisms that depend on plasma rotation and kinetic effects. Kinetic modification of ideal stability calculated with the 'MISK' code [B. Hu et al., Phys. Plasmas 12, 057301 (2005)] is outlined. For an advanced scenario ITER [R. Aymar et al., Nucl. Fusion 41, 1301 (2001)] plasma, the present calculation finds that alpha particles are required for RWM stability at presently expected levels of plasma rotation. Kinetic stabilization theory is tested in an experiment in the National Spherical Torus Experiment (NSTX) [M. Ono et al., Nucl. Fusion 40, 557 (2000)] that produced marginally stable plasmas with various energetic particle contents. Plasmas with the highest and lowest energetic particle content agree with calculations predicting that increased energetic particle pressure is stabilizing but does not alter the nonmonotonic dependence of stability on plasma rotation due to thermal particle resonances. Presently, the full MISK model, including thermal particles and an isotropic slowing-down distribution function for energetic particles, overpredicts stability in NSTX experiments. Minor alteration of either effect in the theory may yield agreement; several possibilities are discussed.

Berkery, J. W.; Sabbagh, S. A.; Reimerdes, H. [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States); Betti, R.; Hu, B.; Bell, R. E. [Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States); Gerhardt, S. P.; Manickam, J.; Podesta, M. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)

2010-08-15

151

Theoretical studies on kinetics of singlet oxygen in nonthermal plasma  

Microsoft Academic Search

An idea to replace singlet delta oxygen (SDO) generator working with wet chemistry by electric discharge generator has got much attention last years. Different kinds of discharge were examined for this purpose, but without a great success. The existing theoretical models are not validated by well-characterized experimental data. To describe complicated kinetics in gas discharge with oxygen one needs to

Mikhail P. Frolov; Andrei A. Ionin; Andrei A. Kotkov; Igor V. Kochetov; Anatolii P. Napartovich; Yurii P. Podmarkov; Leonid V. Seleznev; Dmitrii V. Sinitsyn; Nikolai P. Vagin; Nikolay N. Yuryshev

2004-01-01

152

Molecular photocatalytic processes. I. Kinetic description and conversion efficiency of light energy  

SciTech Connect

This paper investigates the kinetic models of photocatalytic processes. The efficiency and productivity of systems for converting solar energy my molecular photocatalytic systems are analyzed within the framework of a kinetic approach. Equations have been obtained which relate the energy conversion and productivity factors of the systems to the intensity of the light flux being absorbed and the concentrations of electron donors and acceptors.

Varfolomeev, S.D.

1985-11-01

153

Modeling of High Kinetic Energy Plasma Jets for Fusion Applications  

NASA Astrophysics Data System (ADS)

We used semi-analytical models for high velocity (>200 km/s) and density (>10^17 cm-3) plasma jets to describe the acceleration in coaxial electrodes geometry, the collision, and plasma liner implosion, assuming that jets have merged into a spherical or cylindrical shell. The results are compared with experimental data and are being used for guiding LSP and MACH2 codes simulation and for optimization. The simplest model which uses the adiabatic invariant for oscillator revealed the basic relation between the velocity and the parameters of the plasma accelerator. Plasma slug model was extended for including friction and mass addition by electrode erosion. A simple model of blow-by instability by using the canting angle of the plasma current was formulated. As plasma jets collision at high interfacial Mach number generates shock fronts, we analyzed their possible consequences on the merging process and liner formation. The structure of the spherical shell liner during adiabatic implosion and the effect of the shock wave generated at void closure on the confinement time were also investigated.

Bogatu, I. N.; Galkin, S. A.; Kim, J. S.

2006-10-01

154

Plasma heating by ion gyro-scale blobs in the kinetic and fluid regimes  

NASA Astrophysics Data System (ADS)

Strongly localized concentrations of plasma density (‘blobs’) are ubiquitous in the near-edge region of tokamak plasmas. They contribute significantly to heating and transport in that region, and therefore to overall energy confinement. The blob population may include some whose characteristic length scales are on the order of the ion gyro-scale, and cannot be resolved by contemporary diagnostics. Using simulations of ion gyro-scale blobs that include full ion kinetics, we perform the first comparison between the heating ability of ions in small, kinetic blobs and in larger, fluid ones. We find that, embedded in a flowing plasma, small scale blobs contribute more heating per ion than larger blobs, as a result of ion pick-up at the upstream blob-background boundary. This may result in significant excess plasma heating by an ion population that is not yet directly observable.

Gingell, P. W.; Chapman, S. C.; Dendy, R. O.

2013-05-01

155

Growth kinetics and initial stage growth during plasma-enhanced Ti atomic layer deposition  

Microsoft Academic Search

We have investigated the growth kinetics of plasma-enhanced Ti atomic layer deposition (ALD) using a quartz crystal microbalance. Ti ALD films were grown at temperatures from 20 to 200 °C using TiCl4 as a source gas and rf plasma-produced atomic H as the reducing agent. Postdeposition ex situ chemical analyses of thin films showed that the main impurity is oxygen,

H. Kim; S. M. Rossnagel

2002-01-01

156

Landau damping and kinetic instability in non-Maxwellian highly electronegative multi-species plasma  

NASA Astrophysics Data System (ADS)

The effect of two negative ions on the Landau damping and stellar solar wind driven instability is analyzed using kinetic theory for the Lorentzian plasmas. It is investigated that the dispersion relations, damping rates and instability growths are appreciably modified in the presence of Generalized Lorentzian or kappa distributed function and additional negative ion in our plasma system. A quantitative measurement of the threshold value of the streaming velocity is also determined to estimate the condition of the growing instability.

Arshad, Kashif; Mirza, Arshad M.

2013-10-01

157

Kinetic dissipation and anisotropic heating in a turbulent collisionless plasma  

SciTech Connect

The kinetic evolution of the Orszag-Tang vortex is studied using collisionless hybrid simulations. In magnetohydrodynamics (MHD) this configuration leads rapidly to broadband turbulence. At large length scales, the evolution of the hybrid simulations is very similar to MHD, with magnetic power spectra displaying scaling similar to a Kolmogorov scaling of -5/3. At small scales, differences from MHD arise, as energy dissipates into heat almost exclusively through the magnetic field. The magnetic energy spectrum of the hybrid simulation shows a break where linear theory predicts that the Hall term in Ohm's law becomes significant, leading to dispersive kinetic Alfven waves. A key result is that protons are heated preferentially in the plane perpendicular to the mean magnetic field, creating a proton temperature anisotropy of the type observed in the corona and solar wind.

Parashar, T. N.; Shay, M. A.; Cassak, P. A.; Matthaeus, W. H. [Department of Physics and Astronomy, 217 Sharp Laboratory, University of Delaware, Newark, Delaware 19716 (United States)

2009-03-15

158

Exact kinetic theory for the instability of an electron beam in a hot magnetized plasma  

NASA Astrophysics Data System (ADS)

Efficiency of collective beam-plasma interaction strongly depends on the growth rates of dominant instabilities excited in the system. Nevertheless, exact calculations of the full unstable spectrum in the framework of relativistic kinetic theory for arbitrary magnetic fields and particle distributions were unknown until now. In this paper, we give an example of such a calculation answering the question whether the finite thermal spreads of plasma electrons are able to suppress the fastest growing modes in the beam-plasma system. It is shown that nonrelativistic temperatures of Maxwellian plasmas can stabilize only the oblique instabilities of relativistic beam. On the contrary, non-Maxwellian tails typically found in laboratory beam-plasma experiments are able to substantially reduce the growth rate of the dominant longitudinal modes affecting the efficiency of turbulent plasma heating.

Timofeev, I. V.; Annenkov, V. V.

2013-09-01

159

Nonlocal, kinetic stimulated Raman scattering in nonuniform plasmas: Averaged variational approach  

NASA Astrophysics Data System (ADS)

Excitation of continuously phase-locked (autoresonant) plasma waves in a nonuniform plasma via stimulated Raman backscattering is analyzed with a focus on the kinetic regime (k?D~1). The dominant nonlinear effect in this regime is that of resonant particles, and the plasma wave excitation is a nonlocal process involving formation and transport of the electron phase space holes. Whitham's averaged variational principle is applied in studying the coupled plasma, laser pump, and seed waves dynamics. A flat-top electron velocity distribution is used as the simplest model allowing a variational formulation within the water bag theory. The corresponding Lagrangian, averaged over the fast phase variable, yields evolution equations for the slow field variables. The adiabatic multiple water bag extension of the theory for application to autoresonant plasma waves in nonuniform plasmas with more realistic initial distributions is also discussed. Numerical solutions of the system of slow variational equations are compared with Vlasov-Ampere simulations.

Khain, P.; Friedland, L.; Shagalov, A. G.; Wurtele, J. S.

2012-07-01

160

Mechanism and kinetics of plasma deposition of hydrocarbon films  

Microsoft Academic Search

The plasma polymerization of ethane was studied in a flow reactor with parallel plate electrodes sustaining a discharge at 13.56 MHz. Local deposition rates were measured as a function of axial position in the reactor with a quartz crystal microbalance. Effluent gas composition was analyzed with a gas chromatograph capable of separating C⁠through Câ hydrocarbons. The effluent gas is

1981-01-01

161

On quantum plasma kinetic equations with a Bohmian force  

NASA Astrophysics Data System (ADS)

The dispersion relation arising from a Vlasov-Poisson system with a Bohmian force term is examined and compared to the more fundamental Bohm and Pines dispersion relation for quantum plasmas. Discrepancies are found already when considering the leading order thermal effects. The time-averaged energy densities for longitudinal modes are also shown to be noticeably different.

Haas, F.

2010-08-01

162

A fluid description for the discharge equilibrium of a divergent electron cyclotron resonance plasma source  

SciTech Connect

A fluid description of the presheath of a magnetized plasma is used to model a divergent electron cyclotron resonance (ECR) plasma source. The fluid equations are moments of the time-independent Boltzman equation when cross-field particle motion occurs only through a static {bold E}{times}{bold B} drift. Closure is obtained by neglecting third-order moments. The electrons are assumed to have constant temperature along the magnetic field, to obey a Maxwell--Boltzmann potential-density relationship, and to be warmer than the ions. Interactions between plasma and neutral gas are included by specifying the profile of the gas density along the magnetic field and collision cross sections. A form of the equations is derived that can be used to study ions with anisotropic temperatures. The model is used to estimate the axial profiles of the density, ion flow, and ion temperature of an ECR plasma source. The calculated global relationships between (1) the electron temperature and the equilibrium neutral gas density, and (2) the absorbed microwave power and the equilibrium plasma density are comparable with experimental measurements. Furthermore, the calculated ion temperature is comparable to recently reported measurements (Appl. Phys. Lett. {bold 57}, 661 (1990) and Appl. Phys. Lett. {bold 58}, 458 (1991)).

Guan, G.; Mauel, M.E. (Department of Applied Physics, Columbia University, New York, New York 10027 (United States)); Holber, W.M.; Caughman, J.B.O. (IBM Research Division, T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States))

1992-12-01

163

Relativistic kinetic theory of electromagnetic waves in equilibrium magnetized plasma. General dispersion equations  

Microsoft Academic Search

The relativistic kinetic theory of parallel propagating electromagnetic waves in a magnetized equilibrium plasma is presented. On the basis of relativistic Vlasov-Maxwell equations, a general explicit dispersion relation is derived by a correct analytical continuation for all complex frequencies of electromagnetic waves.

M. Lazar; R. Schlickeiser

2003-01-01

164

Plasma surface functionalization and dyeing kinetics of Pan-Pmma copolymers  

NASA Astrophysics Data System (ADS)

Fiber surface modification with air corona plasma has been studied through dyeing kinetics under isothermal conditions at 30 °C on an acrylic-fiber fabric with a cationic dye (CI Basic Blue 3) analyzing the absorption, desorption and fixing on the surface of molecules having defined cationic character.

Labay, C.; Canal, C.; Rodríguez, C.; Caballero, G.; Canal, J. M.

2013-10-01

165

Effects of Charge in Heavy Ions on Solitary Kinetic Alfvén Waves in Double-Ion Plasmas  

Microsoft Academic Search

After the charge of heavy ions is considered, a Sagdeev equation is obtained for the solitary kinetic Alfvén waves (SKAWs) in a low-beta (me\\/mp << beta << 1 or mp\\/me >> alpha >> 1), three-component (electrons, protons, and highly charged heavy ions) plasma. Numerical results show that the charge number q of heavy ions can cause the width of the

Lei Yang; De-Jin Wu

2006-01-01

166

Study of kinetic shear Alfvén modes driven by ion temperature gradient in tokamak plasmas  

Microsoft Academic Search

Discrete kinetic shear Alfvén modes driven by ion temperature gradient (AITG) are investigated in the full gyrokinetic limit. It is shown that AITG instability may occur when the plasma pressure gradient is well below the threshold value for ideal MHD ballooning instabilities and that the critical magnetic shear required to completely stabilize the former is significantly higher than that for

Jiaqi Dong; L. Chen; F. Zonca

1999-01-01

167

Simulation of Low Pressure Plasma Processing Reactors: Kinetics of Electrons and Neutrals  

Microsoft Academic Search

In this paper, we illustrate different aspects of electron kinetics and rarefied gas effects in low pressure inductively coupled plasmas (ICPs). We focus on deterministic methods of solving the Boltzmann equation and its derivatives. Due to small electron mass, the Boltzmann equation for electrons can be reduced to a Fokker-Planck equation of lower dimensionality and solved together with electromagnetic and

R. R. Arslanbekov; V. I. Kolobov

168

Experimental method for gas kinetic temperature measurements in a thermal plasma  

NASA Astrophysics Data System (ADS)

A laser-based diagnostic technique has been developed to probe a thermal plasma for kinetic temperature and velocity measurements. The system employs a scanning tandem Fabry-Perot interferometer to measure the Doppler broadening and Doppler shift of Rayleigh scattered laser light. Practical problems of implementing the method are described.

Reynolds, Larry D.; Shaw, C. B.

1991-12-01

169

Jovian plasma torus interaction with Europa: 3D hybrid kinetic simulation. First results  

Microsoft Academic Search

The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect to variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical for improving the interpretation of the existing Europa flyby measurements from the Galileo orbiter

A. S. Lipatov; J. F. Cooper; W. R. Paterson; E. C. Sittler; R. E. Hartle; D. G. Simpson

2010-01-01

170

Jovian's plasma torus interaction with Europa: 3D hybrid kinetic simulation  

Microsoft Academic Search

The hybrid kinetic model approach supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect to variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical to improved interpretation of the existing measurements for surface and atmospheric composition from

A. S. Lipatov; J. F. Cooper; W. R. Paterson

2009-01-01

171

Capacitively Coupled Radio Frequency Discharge Plasmas In Hydrogen: Particle Modeling and Negative Ion Kinetics  

SciTech Connect

We present a 1D(r)2D(v) particle code for capacitively coupled radio frequency discharge plasmas in hydrogen, which includes a rigorous kinetic modeling of ion transport and several solutions to speed up the convergence. In a test case the effect of surface atom recombination and molecule vibrational deactivation on H- concentration is investigated.

Diomede, P.; Longo, S.; Capitelli, M. [Dipartimento di Chimica dell'Universita' di Bari, Via Orabona 4, 70126 Bari (Italy); IMIP/CNR, Via Orabona 4, 70126 Bari (Italy)

2005-05-16

172

Kinetic temperature and charge of a dust grain in weakly ionized gas-discharge plasmas  

SciTech Connect

Analytical relations are given for estimating the energy of the stochastic motion of an individual dust grain heated by electrostatic ion oscillations in a weakly ionized gas-discharge plasma. Dust grain charging processes are analyzed, and an empirical approximation is obtained for the ion current to the grain surface. The processes are simulated under conditions similar to those of laboratory experiments on dusty plasmas. It is found that the kinetic temperature of a dust grain heated by electrostatic ion oscillations in a gas-discharge plasma can exceed the background gas temperature.

Vaulina, O. S., E-mail: vaul@ihed.ras.ru; Repin, A. Yu.; Petrov, O. F.; Adamovich, K. G. [Russian Academy of Sciences, Institute for High Energy Densities, Joint Institute for High Temperatures (Russian Federation)

2006-06-15

173

Role of plasma activation in kinetics of carbon nanotube growth in plasma-enhanced chemical vapor deposition  

NASA Astrophysics Data System (ADS)

The effect of the acceleration of carbon nanotube (CNT) growth from methane via modification of the gas composition with plasma discharge is studied by means of kinetic modeling. A model of CNT growth describing the detailed gas-phase and surface kinetics of hydrocarbons in catalytic chemical vapor deposition is used. It is shown that the effect of plasma is related to the formation of active species in the gas phase that can easily adsorb and dissociate on the catalyst surface. It is also demonstrated that in addition to the adsorption of carbon precursors, the CNT growth rate can be limited by the gas-phase diffusion of carbon species to the catalyst surface. The critical energy input above which the dominant contribution to CNT growth is provided by non-radical neutral species is calculated and confirmed by analytic estimates.

Lebedeva, Irina V.; Knizhnik, Andrey A.; Gavrikov, Alexey V.; Baranov, Alexey E.; Potapkin, Boris V.; Smith, David J.; Sommerer, Timothy J.

2012-04-01

174

Energy transfer and dual cascade in kinetic magnetized plasma turbulence.  

PubMed

The question of how nonlinear interactions redistribute the energy of fluctuations across available degrees of freedom is of fundamental importance in the study of turbulence and transport in magnetized weakly collisional plasmas, ranging from space settings to fusion devices. In this Letter, we present a theory for the dual cascade found in such plasmas, which predicts a range of new behavior that distinguishes this cascade from that of neutral fluid turbulence. These phenomena are explained in terms of the constrained nature of spectral transfer in nonlinear gyrokinetics. Accompanying this theory are the first observations of these phenomena, obtained via direct numerical simulations using the gyrokinetic code AstroGK. The basic mechanisms that are found provide a framework for understanding the turbulent energy transfer that couples scales both locally and nonlocally. PMID:21599375

Plunk, G G; Tatsuno, T

2011-04-20

175

Kinetic simulation of plasma flows in the inner magnetosphere  

SciTech Connect

A one-dimensional hybrid particle code is used to study the interactions between upflowing thermal ions from conjugate ionospheres. The simulation model allows for multiple species, convection of plasmaspheric flux tubes, and Coulomb self-collisions which conserve momentum and energy locally. The model incorporates a variable-flux boundary condition where the flux, at the boundaries, approaches zero as the plasmasphere fills and equilibrium conditions are reached. The effects of two important processes on plasmaspheric refilling have been considered. The first includes convection of the plasmaspheric flux tube. The second is the interaction of ionospheric thermal plasma and particle injection from an external source. Particle injection seems to play an important role in the evolution of the total particle distribution on the early timescales (t<1 hour); however, for late timescales (t>8 days) the thermal plasma from the ionosphere dominates the particle distribution. 48 refs., 9 figs.

Miller, R.H.; Rasmussen, C.E.; Gombosi, T.I. [Univ. of Michigan, Ann Arbor, MI (United States)] [and others

1993-11-01

176

Kinetic simulations of argon dusty plasma afterglow including metastable atom kinetics  

NASA Astrophysics Data System (ADS)

The afterglow of a dusty plasma of rf discharge in argon is simulated by the particle-in-cell-Monte Carlo collision (PIC-MCC) method. The experimental observation that heavy dust contamination of plasma leads to an anomalous increase in the electron density at the beginning of afterglow is explained by release of electrons from the dust surface. Under the assumption that the floating potential of particles is in equilibrium with plasma conditions, the fast cooling of electrons in afterglow plasma due to a rapid escape of hot electrons from the volume leads to a decrease in the magnitude of the floating potential and hence to a loss of charge by dust. The intensive desorption of electrons from nanoparticles is the origin of anomalous behavior of the electron density. At the next stage of afterglow, when the electrons become cool, the plasma decay is defined by ambipolar diffusion. The effect of metastable argon atoms is also considered. Additional ionization due to metastable atom collisions affects the electron temperature but does not change the behavior of the electron density qualitatively.

Alexandrov, A. L.; Schweigert, I. V.; Ariskin, D. A.

2013-04-01

177

A kinetic model of the plasma flow at the magnetic z-pinch and the plasmoid structure. Part 2 (in English)  

NASA Astrophysics Data System (ADS)

In this article we will follow the approach developed in articles N.~N.~Bogoliubov, V.~Hr.~Samoilenko, Ukr. Fiz. Zh., 37, 147 (1992); J.~Gibbon, Physica D, 3, 503 (1981) using modern Lie--algebraic and symplectic geometry methods. It is devoted to the description of Boltzman--Vlasov type kinetic equations and some two--dimensional hydrodynamic Benney type flows associated with them. In our case of the cylindrical symmetry taking place at the interrupted magnetic z--pinch in plasma we used intensively the corresponding two--dimensionality of the plasma flow under consideration which made it possible to build a kinetic model of the plasmoid vortex structure with a conserved number of linkages of vortex lines. The latter can be used to explain the observed earlier stability of the plasmoid structure at the magnetic z--pinch.

Kubes, P.; Prykarpatsky, A. K.; Zagrodzinski, J.; Prykarpatsky, Y. A.

178

Plasma kinetics of complement component C4: comparison of three models  

SciTech Connect

Plasma C4 kinetics were studied in members of a kindred with hereditary incomplete C4 deficiency and in control subjects. Test subjects received iodine /sup 125/-labeled C4 intravenously, and plasma disappearance curves for 125I-C4 were plotted. By nonlinear least-squares analysis, we fit two-, three-, and four-exponential models of plasma disappearance to the plasma curves of each subject. Goodness of fit was significantly better for all subjects with the three-exponential versus the two-exponential model (p less than 0.0005). No further improvement in curve fit was accomplished by using a four-exponential model (p greater than 0.5). Metabolic rates and extravascular/plasma ratios calculated from the two- and three-exponential models were significantly different. As judged by extravascular/plasma ratio, the two-exponential model underestimated the amount of extravascular C4. Furthermore, the two-exponential model significantly over-estimated catabolic and synthetic rates. Hence, our results show that C4 kinetics are not optimally described by a conventional, two-exponential model. A possible explanation for our findings is that in previous studies of C4 metabolism, the analysis of plasma radioactivity disappearance curves was done by inspection, whereas we used least-squares analysis, a method that determines the number of exponentials with greater reliability.

Wisnieski, J.J.; Nathanson, M.H.

1989-02-01

179

Kinetic analysis and energy efficiency of phenol degradation in a plasma-photocatalysis system.  

PubMed

Combination of two kinds of advanced oxidation processes (AOPs) is an effective approach to control wastewater pollution. In this research, a pulsed discharge plasma system with multi-point-to-plate electrode and an immobilized TiO(2) photocatalysis system is coupled to oxidize target pollutant in aqueous solution. Kinetic analysis (pseudo-first order kinetic constant, k) and energy efficiency (energy yield value at 50% phenol conversion, G(50)) of phenol oxidation in different reaction systems (plasma alone and plasma-photocatalysis) are reviewed to account for the synergistic mechanism of plasma and photocatalysis. The experimental results show that higher k and G(50) of phenol oxidation can be obtained in the plasma-photocatalysis system under the conditions of different gas bubbling varieties, initial solution pH and radical scavenger addition. Moreover, the investigation tested hydroxyl radical (OH) is the most important species for phenol removal in the synergistic system of plasma-photocatalysis as well as in the plasma alone system. PMID:21232856

Wang, Hui-juan; Chen, Xiao-yang

2010-12-27

180

Cadmium and zinc kinetics in rat plasma following intravenous injection  

SciTech Connect

Previous studies with isolated perfused rat liver suggested several hypotheses concerning Cd and Zn transport across the hepatic sinusoidal membrane. The studies presented here were designed to verify these observations in vivo. Either Cd or Zn was injected iv and plasma samples were collected for 15 min. Cd doses ranged from 0.15 to 1.48 mg/kg, Zn doses from 0.35 to 1.47 mg/kg. Cd clearance from plasma decreased from 5.29 +- 0.69 ml/min at the lowest dose to 3.84 +- 0.19 ml/min at the highest dose. Although Cd clearance in vivo fell within the range observed in the isolated perfused liver, at low doses Cd clearance in the isolated perfused liver was significantly above that observed in vivo. This difference is attributed to flow-limited delivery of Cd to the liver via the portal circulation in vivo. Intravenous injection of Cd doses greater than 0.30 mg/kg resulted in an elevation of plasma Zn levels; however, plateau values did not exhibit a well-defined dose-response relationship. Hepatic and renal Cd concentrations were linearly related to dose. Zn clearance from plasma was approximately one-fifth as rapid as Cd clearance. Although the liver played a dominant role in Cd clearance, accumulating 50 to 75% of the dose, it played a minor if not negligible role in Zn clearance. The data indicate the difficulties involved in resolving hepatic transport mechanisms in the intact animal and support the validity of the isolated perfused rat liver preparation as a system in which to investigate these mechanisms.

Frazier, J.M.

1980-05-01

181

One-dimensional hybrid-direct kinetic simulation of the discharge plasma in a Hall thruster  

NASA Astrophysics Data System (ADS)

In order to model the non-equilibrium plasma within the discharge region of a Hall thruster, the velocity distribution functions (VDFs) must be obtained accurately. A direct kinetic (DK) simulation method that directly solves the plasma Boltzmann equation can achieve better resolution of VDFs in comparison to particle simulations, such as the particle-in-cell (PIC) method that inherently include statistical noise. In this paper, a one-dimensional hybrid-DK simulation, which uses a DK simulation for heavy species and a fluid model for electrons, is developed and compared to a hybrid-PIC simulation. Time-averaged results obtained from the hybrid-DK simulation are in good agreement with hybrid-PIC results and experimental data. It is shown from a comparison of using a kinetic simulation and solving the continuity equation that modeling of the neutral atoms plays an important role for simulations of the Hall thruster discharge plasma. In addition, low and high frequency plasma oscillations are observed. Although the kinetic nature of electrons is not resolved due to the use of a fluid model, the hybrid-DK model provides spatially and temporally well-resolved plasma properties and an improved resolution of VDFs for heavy species with less statistical noise in comparison to the hybrid-PIC method.

Hara, Kentaro; Boyd, Iain D.; Kolobov, Vladimir I.

2012-11-01

182

One-dimensional hybrid-direct kinetic simulation of the discharge plasma in a Hall thruster  

SciTech Connect

In order to model the non-equilibrium plasma within the discharge region of a Hall thruster, the velocity distribution functions (VDFs) must be obtained accurately. A direct kinetic (DK) simulation method that directly solves the plasma Boltzmann equation can achieve better resolution of VDFs in comparison to particle simulations, such as the particle-in-cell (PIC) method that inherently include statistical noise. In this paper, a one-dimensional hybrid-DK simulation, which uses a DK simulation for heavy species and a fluid model for electrons, is developed and compared to a hybrid-PIC simulation. Time-averaged results obtained from the hybrid-DK simulation are in good agreement with hybrid-PIC results and experimental data. It is shown from a comparison of using a kinetic simulation and solving the continuity equation that modeling of the neutral atoms plays an important role for simulations of the Hall thruster discharge plasma. In addition, low and high frequency plasma oscillations are observed. Although the kinetic nature of electrons is not resolved due to the use of a fluid model, the hybrid-DK model provides spatially and temporally well-resolved plasma properties and an improved resolution of VDFs for heavy species with less statistical noise in comparison to the hybrid-PIC method.

Hara, Kentaro; Boyd, Iain D. [University of Michigan, Ann Arbor, Michigan 48109 (United States); Kolobov, Vladimir I. [CFD Research Corporation, Huntsville, Alabama 35805 (United States)

2012-11-15

183

Kinetic theory for low-frequency turbulence in magnetized plasmas including discrete-particle effects  

NASA Astrophysics Data System (ADS)

In a recently developed kinetic theory for low-frequency turbulence propagating parallel to the ambient magnetic field [P. H. Yoon, Phys. Plasmas 14, 10230 (2007); P. H. Yoon and T.-M. Fang, Phys. Plasmas 14, 102303 (2007); P. H. Yoon and T.-M. Fang, Plasmas Phys. Control. Fusion 50, 085007 (2008)], the effects arising from the discrete particle nature, or the spontaneous thermal effects were ignored. Such an assumption thus limited the theory to purely collisionless ``Vlasov'' regime. In the present paper the previous formalism is generalized to include discrete-particle effects by reformulating the problem on the basis of the Klimontovich equation. The new terms that appear in the particle and wave kinetic equations as a result of the new formalism are the spontaneous drag term associated with the particles and the spontaneous emission and scattering terms associated with the waves.

Yoon, Peter H.; Fang, Ta-Ming

2008-12-01

184

Nonlinear excitations of kinetic Alfven waves in electron-positron-ion plasmas  

SciTech Connect

A detailed study of nonlinear excitations (solitons and double layers) of kinetic Alfven waves in low but finite-beta electron-positron-ion plasma is presented using pseudopotential approach, which is valid for arbitrary wave amplitude. While sub- and super-Alfvenic solitonic structures and sub-Alfvenic double layer structures are found for both r (equilibrium positron-to-ion density ratio) <1 and r>1, super-Alfvenic double layers are found to be favorable in the region r>1. In any case, however, only compressive nonlinear excitations are found to exist. This contradicts the earlier result [H. Kakati and K. S. Goswami, Phys. Plasmas 7, 808 (2000)] predicting the existence of small-amplitude rarefactive sub- and super-Alfvenic kinetic Alfven double layers under the assumption r<<1. The effects of positron/ion density, ion temperature, obliqueness of the wave propagation, and plasma-beta on nonlinear excitations are also examined.

Sah, O. P. [Department of Physics, Birjhora Mahavidyalaya, Pancha-Swahid Path, Bongaigaon-783380, Assam (India)

2010-03-15

185

Alfven continuum deformation by kinetic geodesic effect in rotating tokamak plasmas  

SciTech Connect

Using a quasitoroidal set of coordinates with coaxial circular magnetic surfaces, Vlasov equation is solved for collisionless plasmas in drift approach and a perpendicular dielectric tensor is found for large aspect ratio tokamaks in a low frequency band. Taking into account plasma rotation and charge separation parallel electric field, it is found that an ion geodesic effect deform Alfven wave continuum producing continuum minimum at the rational magnetic surfaces, which depends on the plasma rotation and poloidal mode numbers. In kinetic approach, the ion thermal motion defines the geodesic effect but the mode frequency also depends on electron temperature. A geodesic ion Alfven mode predicted below the continuum minimum has a small Landau damping in plasmas with Maxwell distribution but the plasma rotation may drive instability.

Elfimov, A. G. [Institute of Physics, University of Sao Paulo, 05508-900 Sao Paulo (Brazil)

2010-02-15

186

Orszag Tang vortex - Kinetic study of a turbulent plasma  

SciTech Connect

Kinetic evolution of the Orszag-Tang vortex is studied using collisionless hybrid simulations based on particle in cell ions and fluid electrons. In magnetohydrodynamics (MHD) this configuration leads rapidly to broadband turbulence. An earlier study estimated the dissipation in the system. A comparison of MHD and hybrid simulations showed similar behavior at large scales but substantial differences at small scales. The hybrid magnetic energy spectrum shows a break at the scale where Hall term in the Ohm's law becomes important. The protons heat perpendicularly and most of the energy is dissipated through magnetic interactions. Here, the space time structure of the system is studied using frequency-wavenumber (k-omega) decomposition. No clear resonances appear, ruling out the cyclotron resonances as a likely candidate for the perpendicular heating. The only distinguishable wave modes present, which constitute a small percentage of total energy, are magnetosonic modes.

Parashar, T. N.; Servidio, S.; Shay, M. A.; Matthaeus, W. H. [Department of Physics and Astronomy, 217 Sharp Lab, University of Delaware, Newark, Delaware 19716 (United States); Cassak, P. A. [Department of Physics and Astronomy, 217 Sharp Lab, University of Delaware, Newark, Delaware 19716 (United States); Department of Physics, Hodges Hall, Box 6315, West Virginia University, Morgantown, WV 26506 (United States)

2010-03-25

187

A DRIFT ORDERED SHORT MEAN-FREE DESCRIPTION FOR PARTIALLY IONIZED MAGNETIZED PLASMA  

SciTech Connect

Effects of neutral particles, most prominently the associated heat flux and viscosity, can be very important or even dominant at the edge of a tokamak and so must be self-consistently accounted for in a description of magnetized tokamak edge plasma. To the best of our knowledge, this has only been done so far for short mean-free path plasma under MHD-like Braginskii's orderings i.e. assuming that species velocities are on the order of the ion thermal speed. Since plasma flows in modern tokamaks are usually slow compared with the ion thermal speed (at least in the absence of strong external momentum sources) it is more appropriate to use drift orderings in which the plasma flow velocity is instead comparable with the diamagnetic heat flow divided by pressure. Employing drift orderings and evaluating species distribution functions through second order in the small gyroradius and mean-free path expansion parameters allows accounting for the important effects of heat fluxes on species momentum transport (viscosities), which are missing from the large flow ordered treatments. In this work we consider short mean-free path plasma consisting of electrons and single species of singly-charged ions and neutrals. We neglect neutral-neutral and elastic electron-neutral collisions and approximate the neutral-ion charge-exchange cross-section with a constant. We employ drift orderings to evaluate ion, neutral, and electron heat fluxes, viscosity tensors, and momentum and energy exchange terms and formulate a self-consistent system of electron, ion, and neutral fluid equations, thereby generalizing the drift-ordered treatment of fully ionized plasma.

SIMAKOV, ANDERI N. [Los Alamos National Laboratory

2007-02-08

188

Kinetic Theory in Hot Plasmas and Neutral Gases Applications to the Computation of the transport coefficients  

SciTech Connect

The conference is devoted to the study of systems consisting of a large number of particles by using the kinetic theory. In a first part, we present a general overview of the kinetic theory. In particular, the role of the correlations between particles is shown and discussed through the main models reported in the literature. In a second part, we present three applications to the transport properties in plasmas and neutral gases. The first application is devoted to the transport in hot plasmas perturbed with respect to the global equilibrium. The quasi-static and collisionless distribution function and transport coefficients are established. The influence of relativistic effects is also discussed. The second application deals with strongly inhomogeneous magnetized plasmas. The transport coefficients of Braginskii are calculated numerically in the local and the weakly nonlocal approximations. New nonlocal transport coefficients are emphasized. Finally, we apply the kinetic theory to the neutral gases by calculating the semi-collisional dispersion relation of acoustic waves. In particular, the dispersion and the damping of these waves in rarefied gases are highlighted. The method used to solve the kinetic equations is compared with the conventional method of Chapman-Enskog.

Bendib, A. [Laboratoire Electronique Quantique, Faculte de Physique Universite des Sciences et de la Technologie Houari Bouedienne USTHB Bab Ezzouar (Algeria)

2008-09-23

189

Plasma radioiron kinetics in man: explanation for the effect of plasma iron concentration.  

PubMed Central

The plasma iron turnover was measured in 19 normal subjects. A correlation was found between plasma iron concentration and plasma iron turnover. In addition to the turnover of 55Fe at normal plasma iron concentration (predominantly monoferric transferrin), a second turnover in which the labeled plasma was saturated with iron (to produce predominantly diferric transferrin) was studied with 50Fe. It was demonstrated that diferric transferrin had a greater rate of iron turnover but that the distribution between erythroid and non-erythroid tissues was unchanged. It was concluded that plasma iron turnover is dependent on the monoferric/diferric transferrin ratio in the plasma but that the internal distribution of iron is unaffected.

Skarberg, K; Eng, M; Huebers, H; Marsaglia, G; Finch, C

1978-01-01

190

Kinetic and fluid modelling of plasmas: Energetic beams and tilt stability on field reversed configurations. Ph.D. Thesis  

Microsoft Academic Search

Plasma problems include features on disparate scales. One example is the dynamical coupling of the microscopic details of individual particle motion to the macroscopic plasma flow. A small energetic particle component can modify the low frequency fluid response of a plasma. This work extends fluid models to include a minority component of energetic kinetic particles and applies it to the

Cobb

1993-01-01

191

Kinetic Theory for Plasmas and Wave-Particle Hamiltonian Dynamics  

NASA Astrophysics Data System (ADS)

The plasma limit is characterized by the fact that a particle interacts with many partners. The dynamics leads to the Vlasov equation in the mean-field limit. Collective behaviour in the {mathcal N}-body system is naturally described by M ? {mathcal N} wavelike degrees of freedom, which behave as harmonic oscillator interacting with a population of N?{mathcal N} particles. The self-consistent hamiltonian dynamics with M waves is also mean-field for the N particles, and a Vlasov equation applies for N -> infty. The careful understanding of the limit N -> infty requires taking into account a continuous spectrum of singular excitations of van Kampen-Case type. For M -> infty, the motion of a single particle obeys a Fokker-Planck equation in the strong resonance overlap limit, and the full particle-wave system obeys the quasilinear evolution equations in the weak turbulence regime.

Elskens, Yves

192

A comparison of kinetic and multifluid simulations of laser-produced colliding plasmas  

SciTech Connect

The collision and subsequent interaction of counter-streaming plasmas occurs in several areas of laser-plasma research including double foil targets for x-ray lasers and the plasma blow-off inside ICF hohlraums. Because a single fluid model allows for only one value of the flow velocity at any one spatial location, interpenetration of the plamas is not allowed resulting in immediate stagnation with complete conversion of the ion-streaming kinetic energy to thermal energy. Multifluid models have been developed which employ multiple ion fluid species that interact through the self-consistent electrostatic field and collisional coupling. Because they are approximations to a kinetic situation, the form of these coupling coefficients is not unique, with various workers using differing approximations. More recently, Larroche has implemented a finite difference approach to the ion Fokker-Planck equation while Jones and co-workers have performed two-dimensional simulations of colliding plasmas using a particle-in-cell code with a new collisional model. Our kinetic modeling also makes use of particle in cell (PIC) techniques with Monte Carlo (MC) particle-particle collisions algorithm that is equivalent to the Fokker-Planck collision operator. We have made direct comparison of this MC-PIC model to multifluid simulations on both simple slowing-down and equilibration problems as well as problems characteristic of laser generated colliding plasmas. These comparisons have established the validity of the multifluid model as well as aided in the development of the kinetic capability for more challenging geometries.

Rambo, P.W.; Procassini, R.J.

1994-09-01

193

Growth kinetics of carbon nanowall-like structures in low-temperature plasmas  

NASA Astrophysics Data System (ADS)

The results of a hybrid numerical simulation of the growth kinetics of carbon nanowall-like nanostructures in the plasma and neutral gas synthesis processes are presented. The low-temperature plasma-based process was found to have a significant advantage over the purely neutral flux deposition in providing the uniform size distribution of the nanostructures. It is shown that the nanowall width uniformity is the best (square deviations not exceeding 1.05) in high-density plasmas of 3.0×1018 m-3, worsens in lower-density plasmas (up to 1.5 in 1.0×1017 m-3 plasmas), and is the worst (up to 1.9) in the neutral gas-based process. This effect has been attributed to the focusing of ion fluxes by irregular electric field in the vicinity of plasma-grown nanostructures on substrate biased with -20 V potential, and differences in the two-dimensional adatom diffusion fluxes in the plasma and neutral gas-based processes. The results of our numerical simulations are consistent with the available experimental reports on the effect of the plasma process parameters on the sizes and shapes of relevant nanostructures.

Levchenko, I.; Ostrikov, K.; Rider, A. E.; Tam, E.; Vladimirov, S. V.; Xu, S.

2007-06-01

194

Kinetic study of the secondary plasma created in the ITER neutraliser  

SciTech Connect

The properties of the secondary plasma created inside the ITER Neutral Beam Injector (NBI) neutraliser, through the interaction of the high energetic hydrogen beam with the molecular hydrogen gas, have been analysed. Starting from the results of our OBI-2 PIC Monte-Carlo numerical code, detailed kinetic of the hydrogen plasma has been studied using a Collisional-Radiative model. In this model, the electron distribution function is determined by solving a Boltzmann equation, whereas main plasma species are derived from balance equations. This paper presents preliminary results obtained in a 0D geometry, boundary conditions bing introduced through effective rates for gain and loss of particles at the neutraliser walls. It has been found that the main ion specie is H{sub 2}{sup +}, essentially coming from the ionisation of the target gas. The electron energy distribution function is not maxwellian and its mean energy is about 5 eV. The plasma-wall interactions yield a strong contribution, in particular regarding the density of molecular ion H{sub 3}{sup +}. Assuming several independent slices of plasma along the negative ions beam axis, the axial profile of the secondary plasma has been analysed. It has been found that the density and mean energy profiles of the plasma electrons are directly related to the plasma potential profile, which in turn closely follows the gas density one.

Dure, F.; Lifschitz, A.; Bretagne, J.; Maynard, G.; Katsonis, K.; Minea, T. [LPGP, CNRS-Universite Paris Sud, Orsay (France); Simonin, A. [DRFC, CEA Cadarache, 13108 Saintt-Paul lez Durance (France)

2009-03-12

195

A coarse-grained kinetic equation for neutral particles in turbulent fusion plasmas  

NASA Astrophysics Data System (ADS)

A coarse-grained kinetic equation for neutral particles (atoms, molecules) in magnetized fusion plasmas, valid on time scales large compared to the turbulence correlation time, is presented. This equation includes the effects of plasma density fluctuations, described by gamma statistics, on the transport of neutral particles. These effects have so far been neglected in plasma edge modeling, in spite of the fact that the amplitude of fluctuations can be of order unity. Density fluctuations are shown to have a marked effect on the screening of neutrals and on the spatial localization of the ionization source, in particular at high density. The coarse-grained equations obtained in this work are readily implemented in edge code suites currently used for fusion plasma analysis and future divertor design (ITER, DEMO).

Mekkaoui, A.; Marandet, Y.; Reiter, D.; Boerner, P.; Catoire, F.; Genesio, P.; Rosato, J.; Stamm, R.; Capes, H.; Koubiti, M.; Godbert-Mouret, L.

2012-06-01

196

Various applications of atomic physics and kinetics codes to plasma modeling  

NASA Astrophysics Data System (ADS)

A collection of computer codes developed at Los Alamos have been applied to a variety of plasma modeling problems. The CATS, RATS, ACE, and GIPPER codes are used to calculate a consistent set of atomic physics data for a given problem. The calculated data include atomic energy levels, oscillator strengths, electron impact excitation and ionization cross sections, photoionization cross sections, and autoionization rates. The FINE and LINES codes access these data sets directly to perform plasma modeling calculations. Preliminary results of some of the current applications are presented, including, the calculation of holmium opacity, the modeling of plasma flat panel display devices, the analysis of some new results from the LANL TRIDENT laser and prediction of the radiative properties of the plasma wakefield light source for extreme ultraviolet lithography (EUVL). For the latter project, the simultaneous solution of atomic kinetics for the level populations and the Boltzmann equation for the electron energy distribution is currently being implemented.

Abdallah, J.; Clark, R. E. H.; Kilcrease, D. P.; Csanak, G.; Fontes, C. J.

1996-07-01

197

3D Kinetic Simulation of Plasma Jet Penetration in Magnetic Field  

NASA Astrophysics Data System (ADS)

A high velocity plasmoid penetration through a magnetic barrier is a problem of a great experimental and theoretical interest. Our LSP PIC code 3D fully kinetic numerical simulations of high density (10^16 cm-3) high velocity (30-140 km/sec) plasma jet/bullet, penetrating through the transversal magnetic field, demonstrate three different regimes: reflection by field, penetration by magnetic field expulsion and penetration by magnetic self-polarization. The behavior depends on plasma jet parameters and its composition: hydrogen, carbon (A=12) and C60-fullerene (A=720) plasmas were investigated. The 3D simulation of two plasmoid head-on injections along uniform magnetic field lines is analyzed. Mini rail plasma gun (accelerator) modeling is also presented and discussed.

Galkin, Sergei A.; Bogatu, I. N.; Kim, J. S.

2009-11-01

198

Spectral evolution of two-dimensional kinetic plasma turbulence in the wavenumber-frequency domain  

NASA Astrophysics Data System (ADS)

We present a method for studying the evolution of plasma turbulence by tracking dispersion relations in the energy spectrum in the wavenumber-frequency domain. We apply hybrid plasma simulations in a simplified two-dimensional geometry to demonstrate our method and its applicability to plasma turbulence in the ion kinetic regime. We identify four dispersion relations: ion-Bernstein waves, oblique whistler waves, oblique Alfvén/ion-cyclotron waves, and a zero-frequency mode. The energy partition and frequency broadening are evaluated for these modes. The method allows us to determine the evolution of decaying plasma turbulence in our restricted geometry and shows that it cascades along the dispersion relations during the early phase with an increasing broadening around the dispersion relations.

Comi?el, H.; Verscharen, D.; Narita, Y.; Motschmann, U.

2013-09-01

199

Fully kinetic description of the linear excitation and nonlinear saturation of fast-ion-driven geodesic acoustic mode instability  

NASA Astrophysics Data System (ADS)

We show in this paper that geodesic acoustic modes (GAMs) can be efficiently excited by a population of fast ions even when Landau damping on thermal ions is accounted for. We report in particular fully kinetic calculations of the GAM dispersion relation and its complete solution. Written under a variational form, the quasi-neutrality condition, together with the kinetic Vlasov equation, leads to the density of exchanged energy between particles and the mode. In particular, a linear threshold for the GAMs excitation is derived. Two examples of fast ion distribution have been discussed analytically. It turns out that particles with high perpendicular energy compared to the parallel resonance energy are most responsible for the excitation of the mode. Subsequent numerical simulations of circular plasmas using gysela code have been carried out. In particular, the linear kinetic threshold has been reproduced during the excitation phase, and a nonlinear saturation has been observed. Analysis in the phase space of the evolution of the equilibrium distribution function is presented and the saturation level quantified.

Zarzoso, D.; Garbet, X.; Sarazin, Y.; Dumont, R.; Grandgirard, V.

2012-02-01

200

Excited level populations and excitation kinetics of nonequilibrium ionizing argon discharge plasma of atmospheric pressure  

SciTech Connect

Population densities of excited states of argon atoms are theoretically examined for ionizing argon plasma in a state of nonequilibrium under atmospheric pressure from the viewpoint of elementary processes with collisional radiative model. The dependence of excited state populations on the electron and gas temperatures is discussed. Two electron density regimes are found, which are distinguished by the population and depopulation mechanisms for the excited states in problem. When the electron impact excitation frequency for the population or depopulation is lower than the atomic impact one, the electron density of the plasma is considered as low to estimate the population and depopulation processes. Some remarkable characteristics of population and depopulation mechanisms are found for the low electron density atmospheric plasma, where thermal relaxation by atomic collisions becomes the predominant process within the group of close-energy states in the ionizing plasma of atmospheric pressure, and the excitation temperature is almost the same as the gas temperature. In addition to the collisional relaxation by argon atoms, electron impact excitation from the ground state is also an essential population mechanism. The ratios of population density of the levels pairs, between which exists a large energy gap, include information on the electron collisional kinetics. For high electron density, the effect of atomic collisional relaxation becomes weak. For this case, the excitation mechanism is explained as electron impact ladderlike excitation similar to low-pressure ionizing plasma, since the electron collision becomes the dominant process for the population and depopulation kinetics.

Akatsuka, Hiroshi [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1-N1-10, O-Okayama, Meguro-ku, Tokyo 152-8550 (Japan)

2009-04-15

201

Kinetics of Fluid Demixing in Complex Plasmas: Role of Two-Scale Interactions  

SciTech Connect

Using experiments and combining theory and computer simulations, we show that binary complex plasmas are particularly good model systems to study the kinetics of fluid-fluid demixing at the 'atomistic' (individual particle) level. The essential parameters of interparticle interactions in complex plasmas, such as the interaction range(s) and degree of nonadditivity, can be varied significantly, which allows systematic investigations of different demixing regimes. The critical role of competition between long-range and short-range interactions at the initial stage of the spinodal decomposition is discussed.

Wysocki, A.; Loewen, H. [Heinrich-Heine-Universitaet Duesseldorf, 40225 Duesseldorf (Germany); Raeth, C.; Ivlev, A. V.; Suetterlin, K. R.; Thomas, H. M.; Khrapak, S.; Zhdanov, S.; Morfill, G. E. [Max-Planck-Institut fuer Extraterrestrische Physik, 85741 Garching (Germany); Fortov, V. E.; Lipaev, A. M.; Molotkov, V. I.; Petrov, O. F. [Joint Institute for High Temperatures, 125412 Moscow (Russian Federation)

2010-07-23

202

Kinetics of fluid demixing in complex plasmas: role of two-scale interactions.  

PubMed

Using experiments and combining theory and computer simulations, we show that binary complex plasmas are particularly good model systems to study the kinetics of fluid-fluid demixing at the "atomistic" (individual particle) level. The essential parameters of interparticle interactions in complex plasmas, such as the interaction range(s) and degree of nonadditivity, can be varied significantly, which allows systematic investigations of different demixing regimes. The critical role of competition between long-range and short-range interactions at the initial stage of the spinodal decomposition is discussed. PMID:20867851

Wysocki, A; Räth, C; Ivlev, A V; Sütterlin, K R; Thomas, H M; Khrapak, S; Zhdanov, S; Fortov, V E; Lipaev, A M; Molotkov, V I; Petrov, O F; Löwen, H; Morfill, G E

2010-07-21

203

Gyrocenter-gauge kinetic algorithm for high frequency waves in magnetized plasmas  

SciTech Connect

A kinetic simulation algorithm for high-frequency electromagnetic waves has been developed based on the gyrocenter-gauge kinetic theory. The magnetized plasma system is simulated in the gyrocenter coordinate system. The gyrocenter distribution function F is sampled on the gyrocenter, parallel velocity, and magnetic moment coordinates. The gyrocenter-gauge function S is sampled on the Kruskal rings and shares the first five coordinates with F. The moment integral of pullback transformation is directly calculated using the Monte Carlo method and an explicit difference scheme for Maxwell's equations in terms of potentials is adopted. The new algorithm has been successfully applied to the simulation studies of high frequency extraordinary wave, electron Bernstein wave, and the mode conversion process between the extraordinary wave and the electron Bernstein wave in inhomogeneous plasmas.

Yu Zhi [Department of Modern Physics, University of Science and Technology of China, Hefei 230027 (China); Qin Hong [Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543 (United States)

2009-03-15

204

Effect of driving frequency on excitation of turbulence in a kinetic plasma  

SciTech Connect

The effect of driving frequency on the efficiency of turbulence generation through magnetic forcing is studied using kinetic hybrid simulations with fully kinetic ions and fluid electrons. The efficiency of driving is quantified by examining the energy input into magnetic field as well as the thermal energy for various driving frequencies. The driving is efficient in exciting turbulence and heating the plasma when the time period of the driving is larger than the nonlinear time of the system. For driving at faster time scales, the energy input is weak and the steady state energy is much lower. The heating of the plasma is correlated with intermittent properties of the magnetic field, which are manifested as non-Gaussian statistics. Implications for turbulence in solar corona are discussed.

Parashar, T. N.; Shay, M. A.; Matthaeus, W. H. [Department of Physics and Astronomy, 217 Sharp Laboratory, University of Delaware, Newark, Delaware 19716 (United States); Servidio, S. [Dipartimento di Fisica, Universita' della Calabria, I-87036 Cosenza (Italy); Breech, B. [Army Research Lab, Aberdeen, Maryland 21005 (United States)

2011-09-15

205

AEGIS-K code for linear kinetic analysis of toroidally axisymmetric plasma stability  

NASA Astrophysics Data System (ADS)

A linear kinetic stability code for tokamak plasmas: AEGIS-K (Adaptive EiGenfunction Independent Solutions-Kinetic), is described. The AEGIS-K code is based on the newly developed gyrokinetic theory [L.J. Zheng, M.T. Kotschenreuther, J.W. Van Dam, Phys. Plasmas 14 (2007) 072505]. The success in recovering the ideal magnetohydrodynamics (MHD) from this newly developed gyrokinetic theory in the proper limit leads the AEGIS-K code to be featured by being fully kinetic in essence but hybrid in appearance. The radial adaptive shooting scheme based on the method of the independent solution decomposition in the MHD AEGIS code [L.J. Zheng, M.T. Kotschenreuther, J. Comp. Phys. 211 (2006) 748] is extended to the kinetic calculation. A numerical method is developed to solve the gyrokinetic equation of lowest order for the response to the independent solutions of the electromagnetic perturbations, with the quasineutrality condition taken into account. A transform method is implemented to allow the pre-computed Z-function (i.e., the plasma dispersion function) to be used to reduce the integration dimension in the moment calculation and to assure the numerical accuracy in determining the wave-particle resonance effects. Periodic boundary condition along the whole banana orbit is introduced to treat the trapped particles, in contrast to the usual reflection symmetry conditions at the banana tips. Due to the adaptive feature, the AEGIS-K code is able to resolve the coupling between the kinetic resonances and the shear Alfvén continuum damping. Application of the AEGIS-K code to compute the resistive wall modes in ITER is discussed.

Zheng, L. J.; Kotschenreuther, M. T.; van Dam, J. W.

2010-05-01

206

Von kármán energy decay and heating of protons and electrons in a kinetic turbulent plasma.  

PubMed

Decay in time of undriven weakly collisional kinetic plasma turbulence in systems large compared to the ion kinetic scales is investigated using fully electromagnetic particle-in-cell simulations initiated with transverse flow and magnetic disturbances, constant density, and a strong guide field. The observed energy decay is consistent with the von Kármán hypothesis of similarity decay, in a formulation adapted to magnetohydrodyamics. Kinetic dissipation occurs at small scales, but the overall rate is apparently controlled by large scale dynamics. At small turbulence amplitudes the electrons are preferentially heated. At larger amplitudes proton heating is the dominant effect. In the solar wind and corona the protons are typically hotter, suggesting that these natural systems are in the large amplitude turbulence regime. PMID:24093244

Wu, P; Wan, M; Matthaeus, W H; Shay, M A; Swisdak, M

2013-09-18

207

Kinetic Alfven wave instability driven by electron temperature anisotropy in high-beta plasmas  

SciTech Connect

Based on the kinetic dispersion equation in the low-frequency condition of omegaplasmas, which is associated with kinetic Alfven waves in the wave vector range of k{sub ||}lambda{sub I}<<1 and k{sub perpendicular}rho{sub i}<<1 (where lambda{sub I} and rho{sub i} are the ion inertial length and gyroradius, respectively), is investigated. The results show that the structures of both the growth rate and the real frequency are different from those driven by the ion temperature anisotropy. The growth rate is larger than that driven by the ion anisotropy. The critical instability condition is modified dramatically, in which the electron driven growth rate does not vanish at the classical critical point and its deviation from zero increases with the kinetic effect due to the short-wavelength modification.

Chen, L. [Purple Mountain Observatory, CAS, Nanjing 210008 (China)] [Graduate School, CAS, Beijing 100012 (China); Wu, D. J. [Purple Mountain Observatory, CAS, Nanjing 210008 (China)

2010-06-15

208

von Kármán Energy Decay and Heating of Protons and Electrons in a Kinetic Turbulent Plasma  

NASA Astrophysics Data System (ADS)

Decay in time of undriven weakly collisional kinetic plasma turbulence in systems large compared to the ion kinetic scales is investigated using fully electromagnetic particle-in-cell simulations initiated with transverse flow and magnetic disturbances, constant density, and a strong guide field. The observed energy decay is consistent with the von Kármán hypothesis of similarity decay, in a formulation adapted to magnetohydrodyamics. Kinetic dissipation occurs at small scales, but the overall rate is apparently controlled by large scale dynamics. At small turbulence amplitudes the electrons are preferentially heated. At larger amplitudes proton heating is the dominant effect. In the solar wind and corona the protons are typically hotter, suggesting that these natural systems are in the large amplitude turbulence regime.

Wu, P.; Wan, M.; Matthaeus, W. H.; Shay, M. A.; Swisdak, M.

2013-09-01

209

Kinetic aspects of aluminium titanate layer formation on titanium alloys by plasma electrolytic oxidation  

Microsoft Academic Search

The paper reports on a systematic investigation into the effects of process parameters on the growth kinetics and associated changes in the structure, phase composition and mechanical properties of surface layers formed on Ti–6Al–4V alloy by plasma electrolytic oxidation (PEO) treatment in 0.05–0.2moll?1 solutions of sodium aluminate. Methods of gravimetric, SEM and XRD analysis, as well as microhardness and scratch

A. L. Yerokhin; A. Leyland; A. Matthews

2002-01-01

210

Langmuir solitons in plasma with ?-distributed electrons in the kinetic regime  

NASA Astrophysics Data System (ADS)

Superthermal electrons are often observed in space and astrophysics, and can be appropriately modeled by the family of kappa distribution functions. The Langmuir solitons are studied in the plasma with kappa-distributed electrons based on the Zakharov equation in the kinetic regime. It is shown that the presence of additional superthermal particles does not make qualitative changes to the important aspect of soliton behavior, but modifies the thickness of solitons.

Chen, Hui; Liu, San-Qiu

2011-11-01

211

Generation of coherent wave packets of kinetic Alfven waves in solar plasmas  

SciTech Connect

This work presents the numerical simulations to study the filamentation of kinetic Alfven waves in solar plasmas. Using the modified nonlinear Schroedinger equation model, we study the effect of changing the initial perturbation on filament formation and their nonlinear dynamics. The spectral indices of the power spectrum are calculated with different initial conditions of the simulations. The relevance of the present investigation in coronal heating and solar wind acceleration/turbulence is also pointed out.

Singh, H. D.; Sharma, R. P. [Centre for Energy Studies, Indian Institute of Technology Delhi, New Delhi-110016 (India)

2007-10-15

212

Effective-Viscosity Approach for Nonlocal Electron Kinetics in Inductively Coupled Plasmas  

SciTech Connect

In inductively coupled plasmas, nonlocal electron kinetics lead to the anomalous skin effect. We show that this can be approximately described through a fluid equation for electron momentum including a viscosity term with an effective-viscosity coefficient. The solution of this momentum equation coupled with the Maxwell equations is in good agreement with results from a particle-in-cell simulation over a wide range of conditions, reproducing the nonmonotonic structure of the anomalous skin with sometimes local negative power absorption.

Hagelaar, G. J. M. [Laboratoire Plasma et Conversion d'Energie (LAPLACE, CNRS-UPS), Batiment 3R2, Universite de Toulouse, 118 Route de Narbonne, 31062 Toulouse Cedex 9 (France)

2008-01-18

213

Hypovalency--a kinetic-energy density description of a 4c-2e bond.  

PubMed

A bond descriptor based on the kinetic energy density, the localized-orbital locator (LOL), is used to characterize the nature of the chemical bond in electron deficient multi-center bonds. The boranes B(2)H(6), B(4)H(4), B(4)H(10), [B(6)H(6)](2-), and [B(6)H(7)](-) serve as prototypical examples of hypovalent 3c-2e and 4c-2e bonding. The kinetic energy density is derived from a set of Kohn-Sham orbitals obtained from pure density functional calculations (PBE/TZVP), and the topology of LOL is analyzed in terms of (3,-3) attractors (Gamma). The B-B-B and B-H-B 3c-2e, and the B-B-H-B 4c-2e bonding situations are defined by their own characteristic LOL profiles. The presence of one attractor in relation to the three or four atoms that are engaged in electron deficient bonding provides sufficient indication of the type of 3c-2e or 4c-2e bond present. For the 4c-2e bond in [B(6)H(7)](-) the LOL analysis is compared to results from an experimental QTAIM study. PMID:19452076

Jacobsen, Heiko

2009-04-22

214

A mechanistic description of radiation-induced damage to normal tissue and its healing kinetics.  

PubMed

We introduce a novel mechanistic model of the yield of tissue damage at the end of radiation treatment and of the subsequent healing kinetics. We find explicit expressions for the total number of functional proliferating cells as well as doomed (functional but non-proliferating) cells as a function of time post treatment. This leads to the possibility of estimating-for any given cohort of patients undergoing radiation therapy-the probability distribution of those kinetic parameters (e.g. proliferation rates) that determine times to injury onset and ensuing resolution. The model is suitable for tissues with simple duplication organization, meaning that functionally competent cells are also responsible for tissue renewal or regeneration following injury. An extension of the model to arbitrary temporal patterns of dose rate is presented. To illustrate the practical utility of the model, as well as its limitations, we apply it to data on the time course of urethral toxicity following fractionated radiation treatment and brachytherapy for prostate cancer. PMID:23337571

Hanin, Leonid; Zaider, Marco

2013-01-21

215

Continuum description of rarefied gas dynamics. I. Derivation from kinetic theory.  

PubMed

We describe an asymptotic procedure for deriving continuum equations from the kinetic theory of a simple gas. As in the works of Hilbert, of Chapman, and of Enskog, we expand in the mean flight time of the constituent particles of the gas, but we do not adopt the Chapman-Enskog device of simplifying the formulas at each order by using results from previous orders. In this way, we are able to derive a new set of fluid dynamical equations from kinetic theory, as we illustrate here for the relaxation model for monatomic gases. We obtain a stress tensor that contains a dynamical pressure term (or bulk viscosity) that is process dependent and our heat current depends on the gradients of both temperature and density. On account of these features, the equations apply to a greater range of Knudsen number (the ratio of mean free path to macroscopic scale) than do the Navier-Stokes equations, as we see in the accompanying paper. In the limit of vanishing Knudsen number, our equations reduce to the usual Navier-Stokes equations with no bulk viscosity. PMID:11690147

Chen, X; Rao, H; Spiegel, E A

2001-09-26

216

A mechanistic description of radiation-induced damage to normal tissue and its healing kinetics  

NASA Astrophysics Data System (ADS)

We introduce a novel mechanistic model of the yield of tissue damage at the end of radiation treatment and of the subsequent healing kinetics. We find explicit expressions for the total number of functional proliferating cells as well as doomed (functional but non-proliferating) cells as a function of time post treatment. This leads to the possibility of estimating—for any given cohort of patients undergoing radiation therapy—the probability distribution of those kinetic parameters (e.g. proliferation rates) that determine times to injury onset and ensuing resolution. The model is suitable for tissues with simple duplication organization, meaning that functionally competent cells are also responsible for tissue renewal or regeneration following injury. An extension of the model to arbitrary temporal patterns of dose rate is presented. To illustrate the practical utility of the model, as well as its limitations, we apply it to data on the time course of urethral toxicity following fractionated radiation treatment and brachytherapy for prostate cancer.

Hanin, Leonid; Zaider, Marco

2013-02-01

217

Astrophysical Gyrokinetics: Kinetic and Fluid Turbulent Cascades In Magentized Weakly Collisional Plasmas  

SciTech Connect

This paper presents a theoretical framework for understanding plasma turbulence in astrophysical plasmas. It is motivated by observations of electromagnetic and density fluctuations in the solar wind, interstellar medium and galaxy clusters, as well as by models of particle heating in accretion disks. All of these plasmas and many others have turbulentmotions at weakly collisional and collisionless scales. The paper focuses on turbulence in a strong mean magnetic field. The key assumptions are that the turbulent fluctuations are small compared to the mean field, spatially anisotropic with respect to it and that their frequency is low compared to the ion cyclotron frequency. The turbulence is assumed to be forced at some system-specific outer scale. The energy injected at this scale has to be dissipated into heat, which ultimately cannot be accomplished without collisions. A kinetic cascade develops that brings the energy to collisional scales both in space and velocity. The nature of the kinetic cascade in various scale ranges depends on the physics of plasma fluctuations that exist there. There are four special scales that separate physically distinct regimes: the electron and ion gyroscales, the mean free path and the electron diffusion scale. In each of the scale ranges separated by these scales, the fully kinetic problem is systematically reduced to a more physically transparent and computationally tractable system of equations, which are derived in a rigorous way. In the "inertial range" above the ion gyroscale, the kinetic cascade separates into two parts: a cascade of Alfvenic fluctuations and a passive cascade of density and magnetic-fieldstrength fluctuations. The former are governed by the Reduced Magnetohydrodynamic (RMHD) equations at both the collisional and collisionless scales; the latter obey a linear kinetic equation along the (moving) field lines associated with the Alfvenic component (in the collisional limit, these compressive fluctuations become the slow and entropy modes of the conventional MHD). In the "dissipation range" below ion gyroscale, there are again two cascades: the kinetic-Alfven-wave (KAW) cascade governed by two fluid-like Electron Reduced Magnetohydrodynamic (ERMHD) equations and a passive cascade of ion entropy fluctuations both in space and velocity. The latter cascade brings the energy of the inertial-range fluctuations that was Landau-damped at the ion gyroscale to collisional scales in the phase space and leads to ion heating. The KAWenergy is similarly damped at the electron gyroscale and converted into electron heat. Kolmogorov-style scaling relations are derived for all of these cascades. The relationship between the theoretical models proposed in this paper and astrophysical applications and observations is discussed in detail.

A.A. Schekochihin, S.C. Cowley, W. Dorland, G.W. Hammett, G.G. Howes, E. Quataert, and T. Tatsuno

2009-04-23

218

From a hybrid model to a fully kinetic model: On the modeling of planetary plasma environments by a fully kinetic electromagnetic global model HYB-em  

Microsoft Academic Search

We have developed a fully kinetic electromagnetic model to study instabilities and waves in planetary plasma environments. In the particle-in-a-cell (PIC) model both ions and electrons are modeled as particles. An important feature of the developed global kinetic model, called HYB-em, compared to other electromagnetic codes is that it is built up on an earlier quasi-neutral hybrid simulation platform called

Valter Pohjola; Esa Kallio

2010-01-01

219

The LANL atomic kinetics modeling effort and its application to W plasmas  

SciTech Connect

This is the work of the LANL group on atomic kinetics modelling. There are various levels of detail in the LANL suite of atomic physics codes: (1) Non-relativistic configuration average kinetics (nl{sup w}) + UTA spectra, (2) Relativistic configuration average kinetics (nlj{sup w}) + UTA spectra, (3) Mixed UTA (MUTA) - configuration average kinetics and spectra composed of mixture of UTAs and fine-structure features and (4) Fine-structure levels. The LANL suite of atomic physics codes consists of 5 codes: (1) CATS/RATS atomic structure codes (semi-relativistic Cowan code or Dirac-Fock-Slater code), (2) ACE collisional excitation code (Plane-wave Born, Columb-Born and distorted-wave methods) and (3) GIPPER ionization code (scaled-hydrogenic and distorted-wave methods). An on-line version of the codes is available at http://aphysics2.lanl.gov/tempweb. ATOMIC kinetics modelling code uses the atomic data for LTE or NLTE population kinetics models and spectral modelling of a broad range of plasma applications. The mixed UTA (MUTA) approach was developed for the spectra of complex ions and the results are in very good agreement with the Sandia-Z Iron opacity experiments. The LANL configuration-average/MUTA calculations were applied to tungsten problems of the non-LTE kinetics code comparison workshops. The LANL group plans to perform much larger calculations to assess the accuracy of the older results and to investigate low-temperature tungsten processes relevant to the divertor modelling.

Colgan, James [Los Alamos National Laboratory; Abdallah, Joseph [Los Alamos National Laboratory; Fontes, Christopher [Los Alamos National Laboratory; Zhang, Honglin [Los Alamos National Laboratory

2010-12-10

220

Kinetic-Alfven-wave current drive in elongated-cross-section plasmas  

SciTech Connect

Efficient kinetic-Alfven-wave current drive is possible in plasmas with elongated cross sections (l{gt}1,5) due to the reduction in the relative (compared with the antenna radius) penetration distance from the antenna to the plasma core. Localization of current drive close to the plasma axis alleviates the problems due to the trapped-particle effects. The net fraction (1{minus}{var epsilon}{sup 1/2})/(1+0.5{ital Z}) of the wave momentum contributing to the subthermal current drive far exceeds the existing projections. For the bootstrap-current contribution in the range 0.9{ge}{ital I}{sub {ital b}}/{ital I}{sub {ital p}}{ge}0.1, the current-drive efficiency {gamma}=R{ital n}{sub 20}{ital I}/{ital P} assumes the values 22{ge}{gamma}{ge}1.1.

Puri, S.; Wilhelm, R. (Max-Planck Institut fuer Plasmaphysik, EURATOM Association, Garhing bei Muenchen (Federal Republic of Germany))

1989-07-01

221

Spatially autoresonant stimulated Raman scattering in inhomogeneous plasmas in the kinetic regime  

SciTech Connect

The impact of spatial autoresonance on backward stimulated Raman scattering in inhomogeneous plasmas is investigated in the regime where the dominant nonlinear frequency shift of the Langmuir wave is due to kinetic effects. By numerically solving the coupled mode equations, the spatial growth of the Langmuir wave is observed to self-adjust so as to cancel the detuning from resonance due to inhomogeneity, giving rise to phase-locked solutions to the electron plasma wave equation. For a single resonant point in a linear density profile, the envelope of the electron plasma wave is characterized by a growth that begins at the resonant point and is proportional to the square of distance propagated. In the more physical case where the scattered light is seeded with a broadband noise, autoresonance may lead to a reflectivity well above the level predicted by the usual Rosenbluth gain factor [M. N. Rosenbluth, Phys. Rev. Lett. 29, 565 (1972)].

Chapman, T.; Hueller, S.; Pesme, D. [Centre de Physique Theorique, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex (France); Masson-Laborde, P. E. [CEA, DAM, DIF, F-91297 Arpajon (France); Rozmus, W. [Department of Physics, Theoretical Physics Institute, University of Alberta, Edmonton, Alberta, T6G 2G7 (Canada)

2010-12-15

222

Release kinetics of platelet-derived and plasma-derived growth factors from autologous plasma rich in growth factors.  

PubMed

Many studies have evaluated the biological effects of platelet rich plasma reporting the final outcomes on cell and tissues. However, few studies have dealt with the kinetics of growth factor delivery by plasma rich in growth factors. Venous blood was obtained from three healthy volunteers and processed with PRGF-Endoret technology to prepare autologous plasma rich in growth factors. The gel-like fibrin scaffolds were then incubated in triplicate, in a cell culture medium to monitor the release of PDGF-AB, VEGF, HGF and IGF-I during 8 days of incubation. A leukocyte-platelet rich plasma was prepared employing the same technology and the concentrations of growth factors and interleukin-1? were determined after 24h of incubation. After each period, the medium was collected, fibrin clot was destroyed and the supernatants were stored at -80°C until analysis. The growth factor delivery is diffusion controlled with a rapid initial release by 30% of the bioactive content after 1h of incubation and a steady state release when almost 70% of the growth factor content has been delivered. Autologous fibrin matrix retained almost 30% of the amount of the growth factors after 8 days of incubation. The addition of leukocytes to the formula of platelet rich plasma did not increase the concentration of the growth factors, while it drastically increased the presence of pro-inflammatory IL-1?. Further studies employing an in vitro inflammatory model would be interesting to study the difference in growth factors and pro-inflammatory cytokines between leukocyte-free and leukocyte-rich platelet rich plasma. PMID:23722041

Anitua, Eduardo; Zalduendo, Mari Mar; Alkhraisat, Mohammad Hamdan; Orive, Gorka

2013-04-30

223

Propagation of Alfv'en Waves from Kinetic to Inertial Regimes in a Helicon Plasma Source  

NASA Astrophysics Data System (ADS)

Ion heating by Alfv'en waves is an active area of research in both laboratory and space plasma physics. As new instruments have enabled more detailed exploration of the solar corona (e.g. Hinode spacecraft, Science, Dec. 2007), the evidence in support of significant role of Alfv'en waves in coronal ion heating continues to accumulate. Due to their high density, helicon sources can be employed for coronal plasma studies (e.g., ?HELIX / ?HELIX ?Corona 0.1-1 . - ?Corona 0.1-1). However, the non-uniform electron density and temperature profiles of helicon sources (?=?HELIXmi / mi me=( vth-e / vth-e vA . - vA )^2 . - me=( vth-e / vth-e vA . - vA )^2=0.1-20) lead to kinetic and inertial regimes in Alfv'en wave propagation. As showed by Vincena et al. (PRL, 93, 105003, 2004), the accumulation of magnetic field energy at the kinetic-inertial boundary results from a turning point in the perpendicular group velocity. Here we present observation of Alfv'en waves in HELIX (Hot hELIcon eXperiment) launched by a dipole antenna whose axis is aligned along the background magnetic field. The waves are excited at sub-cyclotronic frequencies within the high density region of a helium plasma. Profile measurements of the wave amplitude show evidence of ducting of the waves along the high density core of the plasma as well as wave energy accumulation at the kinetic-inertial boundary. Furthermore, phase and group velocities measurements are also compared to Alfv'en wave dispersion models.

Houshmandyar, Saeid; Scime, Earl

2009-11-01

224

Sacrificial bonds and hidden length in biomaterials -- a kinetic description of strength and toughness in bone  

NASA Astrophysics Data System (ADS)

Sacrificial bonds and hidden length in structural molecules account for the greatly increased fracture toughness of biological materials compared to synthetic materials without such structural features, by providing a molecular-scale mechanism of energy dissipation. One example of occurrence of sacrificial bonds and hidden length is in the polymeric glue connection between collagen fibrils in animal bone. In this talk, we propose a simple kinetic model that describes the breakage of sacrificial bonds and the revelation of hidden length, based on Bell's theory. We postulate a master equation governing the rates of bond breakage and formation, at the mean-field level, allowing for the number of bonds and hidden lengths to take up non-integer values between successive, discrete bond-breakage events. This enables us to predict the mechanical behavior of a quasi-one-dimensional ensemble of polymers at different stretching rates. We find that both the rupture peak heights and maximum stretching distance increase with the stretching rate. In addition, our theory naturally permits the possibility of self-healing in such biological structures.

Lieou, Charles K. C.; Elbanna, Ahmed E.; Carlson, Jean M.

2013-03-01

225

Gyrokinetic Electron and Fully Kinetic Ion Particle Simulation of Collisionless Plasma Dynamics  

SciTech Connect

Fully kinetic-particle simulations and hybrid simulations have been utilized for decades to investigate various fundamental plasma processes, such as magnetic reconnection, fast compressional waves, and wave-particle interaction. Nevertheless, due to disparate temporal and spatial scales between electrons and ions, existing fully kinetic-particle codes have to employ either unrealistically high electron-to-ion mass ratio, me/mi, or simulation domain limited to a few or a few ten's of the ion Larmor radii, or/and time much less than the global Alfven time scale in order to accommodate available computing resources. On the other hand, in the hybrid simulation, the ions are treated as fully kinetic particles but the electrons are treated as a massless fluid. The electron kinetic effects, e.g., wave-particle resonances and finite electron Larmor radius effects, are completely missing. Important physics, such as the electron transit time damping of fast compressional waves or the triggering mechanism of magnetic reconnection in collisionless plasmas is absent in the hybrid codes. Motivated by these considerations and noting that dynamics of interest to us has frequencies lower than the electron gyrofrequency, we planned to develop an innovative particle simulation model, gyrokinetic (GK) electrons and fully kinetic (FK) ions. In the GK-electron and FK-ion (GKe/FKi) particle simulation model, the rapid electron cyclotron motion is removed, while keeping finite electron Larmor radii, realistic me/mi ratio, wave-particle interactions, and off-diagonal components of electron pressure tensor. The computation power can thus be significantly improved over that of the full-particle codes. As planned in the project DE-FG02-05ER54826, we have finished the development of the new GK-electron and FK-ion scheme, finished its benchmark for a uniform plasma in 1-D, 2-D, and 3-D systems against linear waves obtained from analytical theories, and carried out a further convergence test and benchmark for a 2-D Harris current sheet against tearing mode and other instabilities in linear theories/models. More importantly, we have, for the first time, carried out simulation of linear instabilities in a 2-D Harris current sheet with a broad range of guide field BG and the realistic mi/me, and obtained important new results of current sheet instabilities in the presence of a finite BG. Indeed the code has accurately reproduced waves of interest here, such as kinetic Alfven waves, compressional Alfven/whistler wave, and lower-hybrid/modified two-stream waves. Moreover, this simulation scheme is capable of investigating collisionless kinetic physics relevant to magnetic reconnection in the fusion plasmas, in a global scale system for a long-time evolution and, thereby, produce significant new physics compared with both full-particle and hybrid codes. The results, with mi/me=1836 and moderate to large BG as in the real laboratory devices, have not been obtained in previous theory and simulations. The new simulation model will contribute significantly not only to the understanding of fundamental fusion (and space) plasma physics but also to DOE's SciDAC initiative by further pushing the frontiers of simulating realistic fusion plasmas.

Yu Lin; Xueyi Wang; Liu Chen; Zhihong Lin

2009-08-11

226

Kinetics of ion and prompt electron emission from laser-produced plasma  

NASA Astrophysics Data System (ADS)

We investigated ion emission dynamics of laser-produced plasma from several elements, comprised of metals and non-metals (C, Al, Si, Cu, Mo, Ta, W), under vacuum conditions using a Faraday cup. The estimated ion flux for various targets studied showed a decreasing tendency with increasing atomic mass. For metals, the ion flux is found to be a function of sublimation energy. A comparison of temporal ion profiles of various materials showed only high-Z elements exhibited multiple structures in the ion time of flight profile indicated by the observation of higher peak kinetic energies, which were absent for low-Z element targets. The slower ions were seen regardless of the atomic number of target material propagated with a kinetic energy of 1-5 keV, while the fast ions observed in high-Z materials possessed significantly higher energies. A systematic study of plasma properties employing fast photography, time, and space resolved optical emission spectroscopy, and electron analysis showed that there existed different mechanisms for generating ions in laser ablation plumes. The origin of high kinetic energy ions is related to prompt electron emission from high-Z targets.

Farid, N.; Harilal, S. S.; Ding, H.; Hassanein, A.

2013-07-01

227

Determination of plasma-free fatty acid kinetics with tracers: Methodologic considerations  

SciTech Connect

Plasma-free fatty acids (FFA) are an important source of energy for a variety of tissues. Recently, there has been an increased interest in the measurement of FFA kinetics in vivo, using radiolabeled or stable isotopic tracers. Standard techniques for measurement of FFA-specific activity are relatively imprecise and have limited sensitivity. The authors have developed a method for determination of the concentration and specific activity of individual plasma FFA that is precise (coefficient of variation less than 2%) and sensitive (detection limit in the high femptomolar to low picomolar range). Using this method, one can measure the kinetics of three or more long-chain fatty acids simultaneously. Its sensitivity is a particular advantage if one wishes to measure low rates of FFA turnover such as are encountered during hyperinsulinemia. It has been suggested that, for optimal accuracy in the determination of substrate kinetics, the tracer should be administered in the left ventricle and mixed venous blood samples should be obtained from the right heart. They have conducted experiments in dogs which demonstrate that peripheral tracer infusion and more conventional arterial (or arterialized venous) sampling actually provide more accurate estimates of FFA turnover; this is fortunate, since intracardiac infusion and sampling are not practical for human studies. 39 references.

Miles, J.M.; Jensen, M.D. (Mayo Medical School, Rochester, MN (USA))

1991-05-01

228

Kinetic simulations of finite gyroradius effects in the lunar plasma environment on global, meso, and microscales  

NASA Astrophysics Data System (ADS)

The recent in situ particle measurements near the Moon by Chandrayaan-1 and Kaguya missions as well as the earlier observation by the Lunar Prospector have shown that the Moon-solar wind interaction is more complicated than believed earlier. The new observations have arisen the need for a detailed modelling of the near surface plasma-surface processes and regions near the lunar magnetic anomalies. Especially, interpretation of ion, electron, and energetic neutral atoms (ENA) observations have shown that the plasma cannot be treated as a single fluid but that kinetic effects have to be taken into account. We have studied the kinetic effects and, especially, the role of finite gyro-radius effects at the Moon by kinetic plasma simulations at three different length-scales which exist in the Moon-solar wind interaction. The solar wind interaction with a magnetic dipole, which mimics the lunar magnetic anomalies in this study, is investigated by a 3D self-consistent hybrid model (HYB-Moon) where protons are particles and electrons form a charge neutralizing mass less fluid. This study shows that the particle flux and density and the bulk velocity of the solar wind protons that hit the lunar surface just above the dipole are decreased compared to their undisturbed values. In addition, a particle "halo" region was identified in the simulation, a region around the dipole where the proton density and the particle flux are higher than in the solar wind, qualitatively in agreement with energetic hydrogen atom observations made by the Chandrayaan-1 mission. The near surface plasma within the magnetic anomaly within a Debye sheath is studied by an electromagnetic Particle-in-Cell, PIC, simulation (HYB-es). In the PIC simulation both ions and electrons are treated as particles. Further, we assume in the PIC simulation that the magnetic anomaly blocks away all solar wind particles and the simulation contains only photo-electrons. The analysis shows that the increased magnetic field decreases the strength of the electric potential and results in a thinner potential sheath than without the magnetic field. Overall, the simulations give support for the suggestions that kinetic effects play an important role on the properties of the lunar plasma environment.

Kallio, Esa; Jarvinen, Riku; Dyadechkin, Sergey; Wurz, Peter; Barabash, Stas; Alvarez, Francisco; Fernandes, Vera A.; Futaana, Yoshifumi; Harri, Ari-Matti; Heilimo, Jyri; Lue, Charles; Mäkelä, Jakke; Porjo, Niko; Schmidt, Walter; Siili, Tero

2012-12-01

229

A kinetic theory description of the viscosity of dense fluids consisting of chain molecules  

NASA Astrophysics Data System (ADS)

An expression for the viscosity of a dense fluid is presented that includes the effect of molecular shape. The molecules of the fluid are approximated by chains of equal-sized, tangentially jointed, rigid spheres. It is assumed that the collision dynamics in such a fluid can be approximated by instantaneous collisions between two rigid spheres belonging to different chains. The approach is thus analogous to that of Enskog for a fluid consisting of rigid spheres. The description is developed in terms of two molecular parameters, the diameter ? of the spherical segment and the chain length (number of segments) m. It is demonstrated that an analysis of viscosity data of a particular pure fluid alone cannot be used to obtain independently effective values of both ? and m. Nevertheless, the chain lengths of n-alkanes are determined by assuming that the diameter of each rigid sphere making up the chain can be represented by the diameter of a methane molecule. The effective chain lengths of n-alkanes are found to increase linearly with the number C of carbon atoms present. The dependence can be approximated by a simple relationship m=1+(C-1)/3. The same relationship was reported within the context of a statistical associating fluid theory equation of state treatment of the fluid, indicating that both the equilibrium thermodynamic properties and viscosity yield the same value for the chain lengths of n-alkanes.

de Wijn, Astrid S.; Vesovic, Velisa; Jackson, George; Trusler, J. P. Martin

2008-05-01

230

ANNEX XV Lattice Boltzmann simulations in magnetohydrodynamics and plasmas  

Microsoft Academic Search

LB SIMULATIONS IN MHD AND PLASMAS LB simulations provide a mesoscopic description of the transport properties of physical systems using a linearized kinetic equation. The benefits of these kinetic descriptions arise from the avoidance of the expensive computation present in both microscopic and macroscopic descriptions. Molecular dynamics models quickly become computationally unmanageable as the number of particles increase, while the

G. Breyiannis; S. Naris; D. Valougeorgis

231

Kinetic simulation of an extreme ultraviolet radiation driven plasma near a multilayer mirror  

SciTech Connect

Future generation lithography tools will use extreme ultraviolet radiation to enable the printing of sub-50 nanometer features on silicon wafers. The extreme ultraviolet radiation, coming from a pulsed discharge, photoionizes the low pressure background gas in the tool. A weakly ionized plasma is formed, which will be in contact with the optical components of the lithography device. In the plasma sheath region ions will be accelerated towards the surfaces of multilayer mirrors. A self-consistent kinetic particle-in-cell model has been applied to describe a radiation driven plasma. The simulations predict the plasma parameters and notably the energy at which ions impact on the plasma boundaries. We have studied the influence of photoelectron emission from the mirror on the sheath dynamics and on the ion impact energy. Furthermore, the ion impact energy distribution has been convoluted with the formula of Yamamura and Tawara [At. Data Nucl. Data Tables 62, 149 (1996)] for the sputter yield to obtain the rate of physical sputtering. The model predicts that the sputter rate is dominated by the presence of doubly ionized argon ions.

Velden, M. H. L. van der; Brok, W. J. M.; Mullen, J. J. A. M. van der; Banine, V. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands); ASML Netherlands B.V., De Run 6501, 5504 DR Veldhoven (Netherlands)

2006-10-01

232

Kinetic Alfven wave instability driven by a field-aligned current in high-{beta} plasmas  

SciTech Connect

Including the ion-gyroradius effect, a general low-frequency kinetic dispersion equation is presented, which simultaneously takes account of a field-aligned current and temperature anisotropy in plasmas. Based on this dispersion equation, kinetic Alfven wave (KAW) instability driven by the field-aligned current, which is carried by the field-aligned drift of electrons relative to ions at a drift velocity V{sub D}, is investigated in a high-{beta} plasma, where {beta} is the kinetic-to-magnetic pressure ratio in the plasma. The numerical results show that the KAW instability driven by the field-aligned current has a nonzero growth rate in the parallel wave-number range 0plasma particles, the result shows that the instability conditions for these two driven mechanisms are both modified considerably, in which the growing parametric ranges of KAWs widen. The results have potential importance in understanding the physics of space and astrophysical plasma active phenomena since the field-aligned current, also called the Birkeland current, is one of the most active factors in plasma phenomena.

Chen, L.; Wu, D. J.; Hua, Y. P. [Purple Mountain Observatory, CAS, Nanjing 210008, China and Graduate School, CAS, Beijing 100012 (China); Purple Mountain Observatory, CAS, Nanjing 210008 (China); Purple Mountain Observatory, CAS, Nanjing 210008, China and Graduate School, CAS, Beijing 100012 (China)

2011-10-15

233

Diagnostic Experiment and Kinetic Model Analysis of Microwave CH4\\/H2 Plasmas for Deposition of Diamondlike Carbon Films  

Microsoft Academic Search

Medium-pressure CH4\\/H2 plasmas were generated in a discharge tube on the axis of a cylindrical 2.45-GHz-microwave TM011-mode-resonance cavity for chemical vapor deposition of diamondlike carbon films. Diamondlike carbon synthesis, plasma diagnostic measurements and kinetic model analyses were conducted to examine the correlation between plasma properties and film features. The characteristics of the calculated H-atom density of the excitation quantum level

Hirokazu Tahara; Ken-ichiro Minami; Akira Murai; Toshiaki Yasui; Takao Yoshikawa

1995-01-01

234

Kinetics and specificity of insulin uptake from plasma into cerebrospinal fluid.  

PubMed

To characterize the relationship between insulin levels in plasma and those in cerebrospinal fluid (CSF), we studied the kinetics of both the uptake of insulin into CSF from plasma and the turnover of insulin within the CSF compartment. Sustained physiological levels of euglycemic hyperinsulinemia (plasma insulin approximately 500 pM) did not alter CSF insulin levels within the 1st h, but by 90 min a significant increase was observed (P less than 0.01). During graded hyperinsulinemic clamps (mean plasma insulin approximately 500-15,000 pM), CSF insulin rose in a dose-dependent fashion. This rise was characterized by an initial delay followed by a continuous increase for the next 150 min. We also found that after brief, high-dose intravenous insulin infusions, the t1/2 of CSF insulin was 143 +/- 7 min (means +/- SE; n = 4), similar to that of CSF turnover by bulk flow. To test the specificity of CSF insulin uptake from plasma, we compared this uptake during intravenous insulin infusions with that of proinsulin, a peptide with reduced affinity for the insulin receptor. We observed a significantly lower increment of CSF proinsulin levels over 180 min (13.6 +/- 1.6 pM; means +/- SE; n = 4) compared with that of insulin (22.4 +/- 0.6 pM; n = 4; P less than 0.01), despite plasma proinsulin levels higher than insulin (1,890 +/- 287 vs. 1,283 +/- 192 pM; P less than 0.001). When corrected for the difference in plasma levels, the uptake of insulin was fivefold greater than that of proinsulin.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2205107

Schwartz, M W; Sipols, A; Kahn, S E; Lattemann, D F; Taborsky, G J; Bergman, R N; Woods, S C; Porte, D

1990-09-01

235

Plasma Physics for Nuclear Fusion  

Microsoft Academic Search

The book focuses on the properties of gaseous plasmas needed in the attainment of controlled fusion reactions. The first five chapters develop the fundamentals of plasma physics and present the conditions of nuclear fusion reactions. The next four provide a magnetohydrodynamic description of plasmas, followed by four chapters that explain wave phenomena and instabilities by means of a kinetic model.

K. Miyamoto; Robert L. Dewar

1980-01-01

236

Nonlinear Gyrokinetics: A Powerful Tool for the Description of Microturbulence in Magnetized Plasmas  

SciTech Connect

Gyrokinetics is the description of low-frequency dynamics in magnetized plasmas. In magnetic-confinement fusion, it provides the most fundamental basis for numerical simulations of microturbulence; there are astrophysical applications as well. In this tutorial, a sketch of the derivation of the novel dynamical system comprising the nonlinear gyrokinetic (GK) equation (GKE) and the coupled electrostatic GK Poisson equation will be given by using modern Lagrangian and Lie perturbation methods. No background in plasma physics is required in order to appreciate the logical development. The GKE describes the evolution of an ensemble of gyrocenters moving in a weakly inhomogeneous background magnetic field and in the presence of electromagnetic perturbations with wavelength of the order of the ion gyroradius. Gyrocenters move with effective drifts, which may be obtained by an averaging procedure that systematically, order by order, removes gyrophase dependence. To that end, the use of the Lagrangian differential one-form as well as the content and advantages of Lie perturbation theory will be explained. The electromagnetic fields follow via Maxwell's equations from the charge and current density of the particles. Particle and gyrocenter densities differ by an important polarization effect. That is calculated formally by a "pull-back" (a concept from differential geometry) of the gyrocenter distribution to the laboratory coordinate system. A natural truncation then leads to the closed GK dynamical system. Important properties such as GK energy conservation and fluctuation noise will be mentioned briefly, as will the possibility (and diffculties) of deriving nonlinear gyro fluid equations suitable for rapid numerical solution -- although it is probably best to directly simulate the GKE. By the end of the tutorial, students should appreciate the GKE as an extremely powerful tool and will be prepared for later lectures describing its applications to physical problems.

John E. Krommes

2010-09-27

237

Some kinetic properties of plasma lecithin-cholesterol acyltransferase in hyper-alphalipoproteinemia in man  

SciTech Connect

The aim of this investigation was to study some kinetic properties of lecithin-cholesterol acyltransferase (LCAT) in the blood plasma of patients with hyper-alpha-lipoproteinemia, enabling the presence of LCAT isozymes in the blood to be detected. The velocity of the LCAT reaction was judged by determining labeled CHE formed from /sup 14/C-nonesterified CH and lecithin of HDL on incubation of the latter with the enzyme. Dependence of the velocity of the LCAT reaction on concentration of substrate (nonesterified HDL cholesterol) in four subjects with hyper-alpha-lipoproteinemia is shown.

Nikiforova, A.A.; Alksnis, E.G.; Ivanova, E.M.

1985-07-01

238

Plasma drift-kinetic equation calculations in three-dimensional magnetic geometries  

SciTech Connect

A new code to simulate three-dimensional plasmas in complex toroidal geometries is presented. It solves drift-kinetic equations for the one-particle distribution function f based on their projection onto a functional basis consisting of an arbitrary number of Legendre-Laguerre polynomials. In this paper, these theoretical aspects of the code are exposed together with their relation with the standard formalism. Comparisons with neoclassical theory for the large aspect ratio case and first calculations in the geometry of the TJ-II Heliac are also presented.

Reynolds, J. M. [Instituto de Biocomputacion y Fisica de Sistemas Complejos, Universidad de Zaragoza, 50018 Zaragoza (Spain); Lopez-Bruna, D. [Laboratorio Nacional de Fusion, CIEMAT, 28040 Madrid (Spain)

2010-07-15

239

Jovian plasma torus interaction with Europa. Plasma wake structure and effect of inductive magnetic field: 3D hybrid kinetic simulation  

NASA Astrophysics Data System (ADS)

The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect to a variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical for improving the interpretation of the existing Europa flyby measurements from the Galileo Orbiter mission, and for planning flyby and orbital measurements (including the surface and atmospheric compositions) for future missions. The simulations are based on recent models of the atmosphere of Europa (Cassidy et al., 2007; Shematovich et al., 2005). In contrast to previous approaches with MHD simulations, the hybrid model allows us to fully take into account the finite gyroradius effect and electron pressure, and to correctly estimate the ion velocity distribution and the fluxes along the magnetic field (assuming an initial Maxwellian velocity distribution for upstream background ions). Photoionization, electron-impact ionization, charge exchange and collisions between the ions and neutrals are also included in our model. We consider the models with O++ and S++ background plasma, and various betas for background ions and electrons, and pickup electrons. The majority of O2 atmosphere is thermal with an extended non-thermal population (Cassidy et al., 2007). In this paper, we discuss two tasks: (1) the plasma wake structure dependence on the parameters of the upstream plasma and Europa's atmosphere (model I, cases (a) and (b) with a homogeneous Jovian magnetosphere field, an inductive magnetic dipole and high oceanic shell conductivity); and (2) estimation of the possible effect of an induced magnetic field arising from oceanic shell conductivity. This effect was estimated based on the difference between the observed and modeled magnetic fields (model II, case (c) with an inhomogeneous Jovian magnetosphere field, an inductive magnetic dipole and low oceanic shell conductivity).

Lipatov, A. S.; Cooper, J. F.; Paterson, W. R.; Sittler, E. C., Jr.; Hartle, R. E.; Simpson, D. G.

2013-03-01

240

Statistical description of the fluctuation particle fluxes in the plasma edge  

NASA Astrophysics Data System (ADS)

Plasma turbulence studies carried out in the last few decades have shown that the measured distributions of amplitudes of the fluctuational particle fluxes in the laboratory plasma as well as in the solar wind have non-Gaussian probability density functions. These distributions are leptocurtic and have slowly decreasing exponential tails. Fractional stable densities (FSD) « ? β?? β?? q(x;?,β,Î&)cedil; = 0 g(xy ;?,Î&)cedil;g(y;β,1)y dy, was applied for it description, where 0 < ? ? 2, 0 < β ? 1, |Î&|cedil;? min(1,2?? - 1) and g(x;?,Î&)cedil; and g(y;β,1) respectively is strictly stable and one sided strictly stable distribution. This distributions have heavy slowly decreasing exponential tails too. As is well known [1] through the FSD the solution of the generalization diffusion equation ?βp(x,t) ??2 t-β^(x) --?tβ---= - D(- ) p(x,t)+ Î? (1--β) is expressed. Here β ??tβ is Riman-Liuville fractional derivative and (-)??2 is Laplacian of the fractional order. The probability density function of the fluctuational particle fluxes in plasma peripheral region of stellarator L-2m is studied in the work. The parameters of fractional stable distributions were statistically estimated from measured signals [2]. It is shown that fractional stable distributions give a good fit to the probability density functions of amplitudes of fluctuating particle fluxes. The Hurst parameter was calculated for all the discharges under study. Its values lie in the range 0.64 to 0.75, which agrees with results obtained in other devices. Algorithms for data processing and the algorithm for estimation of parameters of FS densities, along with results of calculations, will be presented in the report. The work is completed under the support of the Russian Fund for Basic Research (projects No's. 07-01-00517, 07-02-00455, 08-02-00651) References [1] V. V. Uchaikin. International Journal of Theoretical Physics 39 p. 2087 (2000). [2] V. E. Bening, V. Yu. Korolev, V. N. Kolokol'tsov, V. V. Saenko, V. V. Uchaikin, and V. M. Zolotarev. J. Math. Sci., 123 p.3722 (2004)

Saenko, V.

2009-04-01

241

LIGKA: A linear gyrokinetic code for the description of background kinetic and fast particle effects on the MHD stability in tokamaks  

Microsoft Academic Search

In a plasma with a population of super-thermal particles generated by heating or fusion processes, kinetic effects can lead to the additional destabilisation of MHD modes or even to additional energetic particle modes. In order to describe these modes, a new linear gyrokinetic MHD code has been developed and tested, LIGKA (linear gyrokinetic shear Alfvén physics) [Ph. Lauber, Linear gyrokinetic

Ph. Lauber; S. Guenter; A. Koenies; S. D. Pinches

2007-01-01

242

Comparative kinetics of metabolism of beclomethasone propionate esters in human lung homogenates and plasma.  

PubMed

The systemic availability of inhaled beclomethasone dipropionate (BDP) is the net result of the absorption of the glucocorticoid from the lower respiratory and gastrointestinal tracts, and metabolism in the lung, plasma, and other sites. The metabolism kinetics of BDP and its active metabolite, beclomethasone 17-monopropionate (17-BMP), in human lung 1000 x g supernatant (HLu) and human plasma (HP) at 37 degrees C were compared. The effect of MgCl(2) and/or an NADPH-generating system on the decomposition of BDP and 17-BMP in HLu was also investigated. The concentrations of BDP and its metabolites were determined by HPLC with UV detection at 242 nm. Kinetics of decomposition of BDP and 17-BMP in HLu and HP were qualitatively and quantitatively different. The decomposition of BDP in HLu involved only hydrolysis. In comparison, three reactions are involved following incubation of BDP in HP; namely, hydrolysis, transesterification, and loss of hydrogen chloride. The hydrolysis of BDP and 17-BMP in HLu seem to be inhibited appreciably by MgCl(2) with the NADPH-generating system. Effective activation of BDP in HLu, in combination with transesterification of 17-BMP in HP, might favor a high ratio of local antiinflammatory activity to systemic side effects following inhalation of BDP. PMID:10944379

Foe, K; Brown, K F; Seale, J P

2000-09-01

243

Energy transport by kinetic-scale electromagnetic waves in fast plasma sheet flows  

NASA Astrophysics Data System (ADS)

We report observations from the THEMIS spacecraft characterizing the nature and importance of low frequency electromagnetic fluctuations on kinetic scales embedded within fast flows in the Earth's plasma sheet. A consideration of wave property variations with frequency and flow speed suggest that for spacecraft frame frequencies satisfying |vf|/ñi ? ùsc ? 100|vf|/ñi (or 0.2 ? fsc ? 20 Hz) these fluctuations can generally be described as kinetic Alfvén waves. Here vf is the flow speed, ñi the ion gyroradius, and ùsc and fsc are the angular and cyclical frequencies respectively in the spacecraft frame. The statistics of energy transport via Poynting flux (S) in these fluctuations and ion energy flux (å) in the flow follow log normal distributions with mean values of = 101.1 ± 0.7 and = 102.4 ± 0.4 mW/m2 respectively where the values are ‘mapped’ to a reference magnetic field at 100 km altitude. Here the indices following ‘ ± ’ correspond to one standard deviation. We find that = 10-1.3 ± 0.7 or that kinetic Alfvén waves on average transport ˜5% of the total energy transport in the flow but note that the values larger than 25% are within one standard deviation of the mean. Our observations show that these waves are continually radiated outward from the flow toward the auroral oval, low latitude boundary layer or lobes and that over several Earth-radii the integrated energy loss from the flow channel can be comparable to the total energy content of the flow itself. We find that this plasma sheet energy loss process is particularly effective within |XGSE| ? 15 RE.

Chaston, C. C.; Bonnell, J. W.; Clausen, L.; Angelopoulos, V.

2012-09-01

244

On the modeling of planetary plasma environments by a fully kinetic electromagnetic global model HYB-em  

Microsoft Academic Search

We have developed a fully kinetic electromagnetic model to study instabilities and waves in planetary plasma environments. In the particle-in-a-cell (PIC) model both ions and electrons are modeled as particles. An important feature of the developed global kinetic model, called HYB-em, compared to other electromagnetic codes is that it is built up on an earlier quasi-neutral hybrid simulation platform called

V. Pohjola; E. Kallio

2010-01-01

245

Excitation of kinetic Alfvén turbulence by MHD waves and energization of space plasmas  

NASA Astrophysics Data System (ADS)

There is abundant observational evidence that the energization of plasma particles in space is correlated with an enhanced activity of large-scale MHD waves. Since these waves cannot interact with particles, we need to find ways for these MHD waves to transport energy in the dissipation range formed by small-scale or high-frequency waves, which are able to interact with particles. In this paper we consider the dissipation range formed by the kinetic Alfvén waves (KAWs) which are very short- wavelengths across the magnetic field irrespectively of their frequency. We study a nonlocal nonlinear mechanism for the excitation of KAWs by MHD waves via resonant decay AW(FW)?KAW1+KAW2, where the MHD wave can be either an Alfvén wave (AW), or a fast magneto-acoustic wave (FW). The resonant decay thus provides a non-local energy transport from large scales directly in the dissipation range. The decay is efficient at low amplitudes of the magnetic field in the MHD waves, B/B0~10-2. In turn, KAWs are very efficient in the energy exchange with plasma particles, providing plasma heating and acceleration in a variety of space plasmas. An anisotropic energy deposition in the field-aligned degree of freedom for the electrons, and in the cross-field degrees of freedom for the ions, is typical for KAWs. A few relevant examples are discussed concerning nonlinear excitation of KAWs by the MHD wave flux and consequent plasma energization in the solar corona and terrestrial magnetosphere.

Voitenko, Y.; Goossens, M.

2004-11-01

246

Kinetics  

NSDL National Science Digital Library

Conceptual questions about kinetics. For example, "[w]hat are the reaction velocity, the rates of formation of N2 and H2, and the rate of decomposition of ammonia for the decomposition of ammonia on a tungsten surface under the conditions reflected in the figure."

Nurrenbern, Susan C.; Robinson, William R.

2008-02-27

247

Effects of plasma kinetic parameters on turbulent layer formation by the Kelvin-Helmholtz instability  

NASA Astrophysics Data System (ADS)

We have recently shown by 2D MHD simulations of the Kelvin-Helmholtz instability (KHI) in a highly asymmetric density layer in a large simulation domain that rapid formation of a broad plasma turbulent layer can be achieved by forward and inverse energy cascades of the KHI [Matsumoto and Seki, JGR, in press.]. The forward cascade is triggered by the growth of the secondary Rayleigh-Taylor instability (RTI) excited during the nonlinear evolution. The inverse cascade is accomplished by a nonlinear coupling of the fastest growing mode of the KHI with other unstable modes. We suggested that the proposed mechanism well explained the observational requirements of the LLBL formation, although some issues are remained to be understood. One major issue, which is not treated accurately in the MHD simulation, is the mixing process itself; the mixing of plasmas is due to the numerical dissipation implicitly or explicitly added in the simulation. To understand all the mechanisms ranging from the dissipating scale to the scale of the largest vortex in a self-consistent manner, we have carried out 2D fully kinetic particle-in-cell (PIC) simulations of the KHI in a large simulation domain which allows growth of multiple KH unstable modes. As a result, we found the inverse energy cascade among the KH unstable modes as have been shown by the 2D MHD simulation. It is also found that the direct energy cascade results in plasma mixing by exciting strong electric fields embedded in electron inertial scales with amplitudes larger than the initial convective electric field. The locally excited electric field is the key agent for the mixing. We have also found two-component distribution functions in the mixed region for the ion and the electron which have been reported by in-situ observations. In this presentation, we show that both direct and inverse energy cascades of the KHI contribute to formation of a large scale plasma mixing layer in a time scale much faster than we expect from the linear theory of the KHI. Also, dependence of the mixing efficiency on the mass ratio (M/m) and the ratio of plasma to gyro frequencies (?pe/?ge) are discussed by results from simulation runs with various kinetic parameters.

Matsumoto, Y.; Seki, K.

2010-12-01

248

Plasma kinetics and efficacy of oral megazol treatment in Trypanosoma brucei brucei-infected sheep.  

PubMed

Experimentally infected sheep have been previously developed as an animal model of trypanosomosis. We used this model to test the efficacy of megazol on eleven Trypanosoma brucei brucei-infected sheep. When parasites were found in blood on day 11 post-infection, megazol was orally administered at a single dose of 40 or 80mg/kg. After a transient aparasitaemic period, all animals except two relapsed starting at day 2 post-treatment, which were considerated as cured on day 150 post-treatment and showed no relapse after a follow-up period of 270 days. In order to understand the high failure of megazol treatment to cure animals, a kinetic study was carried out. Plasma concentrations of megazol determined, by reverse-phase high-performance liquid chromatography at 8h post-treatment in these animals, were lowered, suggesting slow megazol absorption, except in cured animals. However, megazol plasma profiles in uninfected sheep after a single oral dose of megazol showed a fast megazol lowered absorption associated with a short plasma half-life of drug. Inter-individual variation of megazol pharmacokinetic properties was also observed. These findings suggested that the high failure rates of megazol treatment were related to poor drug availability after oral administration in sheep. In conclusion, megazol could cure sheep with T. b. brucei infection but oral administration was not an effective route. PMID:15135860

Boda, Caroline; Enanga, Bertin; Dumet, Hélène; Chauviere, Gérard; Labrousse, François; Couquet, Claude; Saivin, Sylvie; Houin, Georges; Perie, Jacques; Dumas, Michel; Bouteille, Bernard

2004-05-26

249

Kinetic studies on CF/sub 4/ plasmas during etching of Si  

SciTech Connect

Mass spectrometric kinetic measurements were performed on a dc plasma during the etching of Si by CF/sub 4/. The apparatus and procedures used were identical to those developed and used in an earlier study dealing with the Si/SF/sub 6/ system. The signals representative of CF/sup +//sub 3/, CF/sup +//sub 2/, CF/sup +/, F/sup +/, SiF/sup +//sub 3/, SiF/sup +/, and C/sub 2/F/sup +//sub 5/ were studied in some detail. CF/sup +//sub 3/ and CF/sup +//sub 2/ transients produced by stepwise changes of the applied voltage were found to be very similar, on a fractional basis. CF/sup +/ and C/sub 2/F/sup +//sub 5/ signals showed a close correlation, while the F/sup +/ signals indicated a small amount of extra fluorine atoms or ions to be present at relatively high applied voltages. The initial transient rates, following plasma ignition, tended to be slower than those obtained at the higher applied voltages, so the sample surface is somehow etched more rapidly after the first few seconds. In contrast to this, slow signal changes of the sort observed in the Si/SF/sub 6/ system were absent, so the carbonaceous layers which may form on the Si sample surface appear to adjust rapidly to composition changes in the plasma.

Brandt, W.W.; Roselle, P.

1983-09-01

250

Self-consistent simulation of electron cyclotron radiation transport and suprathermal electron kinetics in tokamak plasmas  

NASA Astrophysics Data System (ADS)

Numerical simulations of radial profile of the net radiated electron cyclotron (EC) power density, W(r), in hot tokamak plasmas with strong enough magnetic field revealed strong sensitivity of W(r) to contribution of suprathermal electrons (produced, e.g., by ECRH or ECCD), in contrast to weak sensitivity of total (i.e. volume-integrated) EC power loss (Proc. EPS-2004, P1-175). Here we self-consistently simulate W(r) for ITER-like conditions under competition of three mechanisms: (a) flattening of electron velocity distribution (EVD) in EC radiation field -- and respective partial enlightenment of an optically thick medium; (b) depletion of EVD ``tail'' due to intense radiation emission by the fast electrons; (c) relaxation of EVD to a Maxwellian due to Coulomb collisions. In the plasma core, mechanism ``b'' appears to be stronger than ``a'', whereas in the plasma periphery, situation is opposite. These kinetic effects redistribute W(r) toward weakening of the net power loss in the core and weakening of the net power absorption in the periphery. The implications for ignition conditions are discussed.

Cherepanov, K. V.; Kukushkin, A. B.

2004-11-01

251

A description of the wire explosion process for ETC plasma generators  

Microsoft Academic Search

In an electrothermal-chemical (ETC) gun, electrical energy from a storage device is used to influence the combustion processes that occur within a conventional gun chamber. This typically occurs via a dense, highly nonideal plasma. The ability to simulate an ETC gun system is dependent upon a prediction of the output from the plasma generator. Improvements to a plasma generator computer

Michael J. Taylor; J. Dunnett

2003-01-01

252

Propagator expansion method for solving linearized plasma kinetic equations with collisions. Environmental research papers, June 1983-June 1984  

SciTech Connect

A propagator expansion method is presented for solving linearized plasma kinetic equations with collisions. The essence of the method is the representation and use of the collisional propagator for a given problem as an expansion in powers of the collision frequency. The linearized Balescu-Lenard collision operator and the zero-order distribution function Maxwellian were determined. An exact expression for the collisional damping rate is obtained in the long-wavelength approximation to the first order in the plasma parameter.

Jasperse, J.R.

1984-06-25

253

Jovian's plasma torus interaction with Europa. Plasma wake structure: 3D hybrid kinetic simulation and comparison with E4 flyby Galileo's observations  

Microsoft Academic Search

Abstract The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect to variable upstream magnetic field and flux or density distributions of plasma and energetic ions, electrons, and neutral atoms. This capability is critical for improving the interpretation of the existing Europa flyby measurements from Galileo orbital

A. S. Lipatov; J. F. Cooper; W. R. Paterson; E. C. Sittler; R. E. Hartle

2010-01-01

254

A kinetic model of retarding field analyser measurements in strongly magnetized, flowing, collisional plasmas  

NASA Astrophysics Data System (ADS)

Interpretation of retarding field analyser (RFA) measurements in flowing tokamak scrape-off layer plasmas requires a model of the perturbation introduced by the wake, or presheath, of the instrument. We extend a collisionless kinetic Mach probe theory to include a simple model of ion-ion collisions. Collisions lead to significant modifications in the downstream presheath. Depending on the ion-to-electron temperature ratio, flow speed and collisionality, the measurement obtained by averaging the apparent temperatures on each side of a bi-directional RFA is predicted to overestimate the unperturbed ion temperature, but with errors not exceeding 50% most of the time. The error increases with Mach number, and decreases with the ion-to-electron temperature ratio.

Gunn, J. P.; Fuchs, V.; Ko?an, M.

2013-04-01

255

3D feature profile simulation based on realistic surface kinetic modeling of fluorocarbon plasma etch process  

NASA Astrophysics Data System (ADS)

Recently, one of the critical issues in the etching processes is to achieve ultra high deep contact hole without anomalous behaviors such as sidewall bowing and twisting. To address this issue, we have developed a 3D topography simulator using the level set algorithm based on new memory saving technique, which is suitable in the contact hole etching. For this feature profile simulation, we performed a fluorocarbon plasma-surface kinetic modeling based on our experimental data, a polymer layer based this model was proposed as considering material balance of deposition and etching through steady-state FC layer. Finally, the modeling results showed good agreements with experimental data and could be used successfully for 3D etch profile simulations with consideration of polymer layer.

Chang, Won-Seok; Kwon, Deuk-Chul; Yu, Dong-Hun; Cho, Deog-Gyun; Yook, Yeong-Geun; Kim, Jin-Tae; Yoon, Jung-Sik; Im, Yeon-Ho

2011-11-01

256

Kinetic Theory for Distribution Functions of Wave-Particle Interactions in Plasmas  

SciTech Connect

The evolution of a charged particle distribution function under the influence of coherent electromagnetic waves in a plasma is determined from kinetic theory. For coherent waves, the dynamical phase space of particles is an inhomogeneous mix of chaotic and regular orbits. The persistence of long time correlations between the particle motion and the phase of the waves invalidates any simplifying Markovian or statistical assumptions--the basis for usual quasilinear theories. The generalized formalism in this Letter leads to a hierarchy of evolution equations for the reduced distribution function. The evolution operators, in contrast to the quasilinear theories, are time dependent and nonsingular and include the rich phase space dynamics of particles interacting with coherent waves.

Kominis, Y.; Hizanidis, K. [School of Electrical and Computer Engineering, National Technical University of Athens, Association EURATOM-Hellenic Republic, Zographou GR-15773 (Greece); Ram, A. K. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2010-06-11

257

Kinetics of illuminated complex plasmas considering Mie scattering by spherical dust particles with a size distribution  

SciTech Connect

In this paper Mie scattering of light by dust particles having Mathis, Rumpl, and Nordsieek power law distribution of size has been incorporated in the formulation of the kinetics of an illuminated complex plasma which takes into account the ionization of neutral atoms by an external agency, ion-electron recombination, photoemission of electrons by the dust particles, and accretion of electrons and ions on the surface of the particles; the number and energy balance of the constituent species has also been taken into account. An interesting conclusion is that unlike the usual case (when Mie scattering is neglected) the charge on a particle is not proportional to the radius and that for certain sets of parameters the smaller particles are negatively charged while the larger particles, carry positive charge.

Sodha, M. S. [Disha Institute of Management and Technology, Satya Vihar, Vidhan Sabha-Chandrakhuri Marg, Mandir Hasaud, Raipur, 492101 Chhattisgarh (India); Mishra, S. K.; Misra, Shikha [Department of Education Building, University of Lucknow, Lucknow 226007 (India)

2011-01-01

258

Fully kinetic simulations of magnetic reconnction in semi-collisional plasmas  

SciTech Connect

The influence of Coulomb collisions on the dynamics of magnetic reconnection is examined using fully kinetic simulations with a Monte-Carlo treatment of the Fokker-Planck collision operator. This powerful first-principles approach offers a bridge between kinetic and fluid regimes, which may prove useful for understanding the applicability of various fluid models. In order to lay the necessary groundwork, the collision algorithm is first carefully bench marked for a homogeneous plasma against theoretical predictions for beam-plasma interactions and electrical resistivity. Next, the collisional decay of a current layer is examined as a function of guide field, allowing direct comparisons with transport theory for the parallel and perpendicular resistivity as well as the thermoelectric force. Finally, the transition between collisional and collision less reconnection is examined in neutral sheet geometry. For modest Lundquist numbers S {approx}< 1000, a distinct transition is observed when the thickness of the Sweet-Parker layers falls below the ion inertia length {delta}{sub sp} {approx}< d,. At higher Lundquist number, deviations from the Sweet-Parker scaling are observed due to the growth of plasmoids (secondary-islands) within the elongated resistive layer. In certain cases, this instability leads to the onset of fast reconnection sooner than expected from {delta}{sub sp} {approx} d, condition. After the transition to fast reconnection, elongated electron current layers are formed which are unstable to the formation of new plasmoids. The structure and time-dependence of the electron diffusion region in these semi-collisional regimes is profoundly different than reported in two-fluid simulations.

Daughton, William S [Los Alamos National Laboratory; Roytershteyn, Vadim S [Los Alamos National Laboratory; Albright, Brian J [Los Alamos National Laboratory; Yin, Lin [Los Alamos National Laboratory; Bowers, Kevin J [Los Alamos National Laboratory; Karimabadi, Homa [UCSD

2009-01-01

259

Magnetic field generation in a jet-sheath plasma via the kinetic Kelvin-Helmholtz instability  

NASA Astrophysics Data System (ADS)

We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic jet and an unmagnetized sheath plasma. We have examined the strong magnetic fields generated by kinetic shear (Kelvin-Helmholtz) instabilities. Compared to the previous studies using counter-streaming performed by Alves et al. (2012), the structure of the kinetic Kelvin-Helmholtz instability (KKHI) of our jet-sheath configuration is slightly different, even for the global evolution of the strong transverse magnetic field. In our simulations the major components of growing modes are the electric field Ez, perpendicular to the flow boundary, and the magnetic field By, transverse to the flow direction. After the By component is excited, an induced electric field Ex, parallel to the flow direction, becomes significant. However, other field components remain small. We find that the structure and growth rate of KKHI with mass ratios mi/me = 1836 and mi/me = 20 are similar. In our simulations saturation in the nonlinear stage is not as clear as in counter-streaming cases. The growth rate for a mildly-relativistic jet case (?j = 1.5) is larger than for a relativistic jet case (?j = 15).

Nishikawa, K.-I.; Hardee, P.; Zhang, B.; Du?an, I.; Medvedev, M.; Choi, E. J.; Min, K. W.; Niemiec, J.; Mizuno, Y.; Nordlund, A.; Frederiksen, J. T.; Sol, H.; Pohl, M.; Hartmann, D. H.

2013-09-01

260

Plasma kinetics of Ar/O{sub 2} magnetron discharge by two-dimensional multifluid modeling  

SciTech Connect

Multifluid two-dimensional model was developed to describe the plasma kinetics of the direct current Ar/O{sub 2} magnetron, coupling two modules: charged particles and neutrals. The first module deals with three positive ions - Ar{sup +}, O{sub 2}{sup +}, and O{sup +} - and two negative species - e{sup -} and O{sup -} - treated by the moments of Boltzmann's equation. The second one follows seven neutral species (Ar, O{sub 2}, O, O{sub 3}, and related metastables) by the multicomponent diffusion technique. The two modules are self-consistently coupled by the mass conservation and kinetic coefficients taking into account more than 100 volume reactions. The steady state is obtained when the overall convergence is achieved. Calculations for 10%O{sub 2} in Ar/O{sub 2} mixture at 2.67 and 4 Pa show that the oxygen excited species are mainly created by electron collisions in the negative glow of the discharge. Decreasing the pressure down to 0.67 Pa, the model reveals the nonlocal behavior of the reactive species. The density gradient of O{sub 2} ground state is reversed with respect to all gradients of the other reactive species, since the latter ones originate from the molecular ground state of oxygen. It is also found that the wall reactions drastically modify the space gradient of neutral reactive species, at least as much as the pressure, even if the discharge operates in compound mode.

Costin, C.; Minea, T. M.; Popa, G.; Gousset, G. [LPGP, UMR 8578, CNRS-Paris-Sud XI University, Bat. 210, Orsay Cedex 91405, France and Faculty of Physics, Al. I. Cuza University, 11 Carol I Blvd., Iasi 700506 (Romania); LPGP, UMR 8578, CNRS-Paris-Sud XI University, Bat. 210, Orsay Cedex 91405 (France); Faculty of Physics, Al. I. Cuza University, 11 Carol I Blvd., Iasi 700506 (Romania); LPGP, UMR 8578, CNRS-Paris-Sud XI University, Bat. 210, Orsay Cedex 91405 (France)

2010-03-15

261

Fast, Kinetically self-consistent simulation of RF modulated plasma boundary sheaths  

NASA Astrophysics Data System (ADS)

A mathematical model is presented which enables the efficent, kinetically self-consistent simulation of RF modulated plasma boundary sheaths in all technically relevant discharge regimes. The model consists of a set of kinetic equations for the ions, Boltzmann's relation for the electrons and Poisson's equation for the electrical field. Boundary conditions specify the ion flux at a point deep in the bulk and a periodically modulated sheath voltage or sheath charge. The equations are solved in a statistical sense. However, it is not the well-known particle-in-cell (PIC) scheme that is employed, but an alternative iterative algorithm termed ensemble-in-spacetime (EST). Three modules are called in a sequence: a Monte Carlo module, a harmonic analysis module, and a field module. The iteration is started with the potential values of a self-consistent fluid model and terminates when the updates become sufficiently small, i.e. when self-consistency is achieved. A drastic reduction of the computational effort compared with PIC calculations is achieved. As a first application of the new model, the influence of ion inertia on the dynamics of a collisionless sheath is studied and a comparison of the simulated ion energy distribution with published analytical solutions is performed.

Shihab, Mohammed; Brinkmann, Ralf Peter

2012-10-01

262

Kinetics of Densification and Grain Growth of Pure Tungsten During Spark Plasma Sintering  

NASA Astrophysics Data System (ADS)

The kinetics of densification and grain growth of tungsten during spark plasma sintering (SPS) was studied under isothermal conditions. The results show that using SPS, high-density (>97 pct) pure tungsten can be produced without the addition of sintering aids. The estimated sintering exponent ( m = 0.4 ± 0.03) suggests that the rate-controlling mechanism of sintering is diffusion along the grain contacts into the interparticles neck region. The activation energy of tungsten self-diffusion was calculated ( Q = 277 ± 15 kJ/mol) in the temperature range 1523 K to 1773 K (1250 °C to 1500 °C). The activation energy is smaller than the values in previous studies using conventional sintering. This suggests that there may be some differences in the sintering conditions and mechanisms during SPS processing compared to conventional sintering. Grain-growth kinetics was studied in the range 1873 K to 2073 K (1600 °C to 1800 °C) and classified as normal grain growth according to the estimated grain-growth exponent ( m = 2 ± 0.2). The grain-growth activation energy was calculated as 231 ± 15 kJ/mol.

Gao, Zhipeng; Viola, Giuseppe; Milsom, Ben; Whitaker, Iain; Yan, Haixue; Reece, Mike J.

2012-12-01

263

Kinetic Plasma Turbulence in the Fast Solar Wind Measured by Cluster  

NASA Astrophysics Data System (ADS)

The k-filtering technique and wave polarization analysis are applied to Cluster magnetic field data to study plasma turbulence at the scale of the ion gyroradius in the fast solar wind. Waves are found propagating in directions nearly perpendicular to the background magnetic field at such scales. The frequencies of these waves in the solar wind frame are much smaller than the proton gyrofrequency. After the wavevector k is determined at each spacecraft frequency f sc, wave polarization property is analyzed in the plane perpendicular to k. Magnetic fluctuations have ?B > ?B ? (here the ? and refer to the background magnetic field B 0). The wave magnetic field has right-handed polarization at propagation angles ? kB < 90° and >90°. The magnetic field in the plane perpendicular to B 0, however, has no clear sense of a dominant polarization but local rotations. We discuss the merits and limitations of linear kinetic Alfvén waves (KAWs) and coherent Alfvén vortices in the interpretation of the data. We suggest that the fast solar wind turbulence may be populated with KAWs, small-scale current sheets, and Alfvén vortices at ion kinetic scales.

Roberts, O. W.; Li, X.; Li, B.

2013-05-01

264

Phenomenological description of the nonequilibrium magnetospheric plasma in the adiabatic approximation  

NASA Astrophysics Data System (ADS)

D'iarmati's (1974) variational principle is used to derive a phenomenological equation of a collisionless nonequilibrium plasma in a strong magnetic field in the adiabatic approximation. Conditions for the investigation of the magnetospheric plasma in the general case are considered; i.e., the parallel-velocity is not equal to zero, the H field is not steady, and the plasma is not quasi-neutral. It is shown that Volosov's (1962) asymptotic method can be used to solve the phenomenological equation.

Pletnev, V. D.; Skuridin, G. A.

1980-11-01

265

Detection of the kinetic geodesic acoustic mode (KGAM) near the centre region of JIPPT-IIU tokamak plasmas  

NASA Astrophysics Data System (ADS)

The broad and intense spectrum of the geodesic acoustic mode (GAM) oscillations near the magnetic axis of tokamak plasmas with Te/Ti Gt 1 becomes narrow and weak during neutral beam heating. It then becomes wide and weak during third harmonics ICRF heating. The wide spectra of GAMs are generally consistent with recent kinetic GAM (KGAM) theories.

Hamada, Y.; Watari, T.; Nishizawa, A.; Yamagishi, O.; Narihara, K.; Ida, K.; Kawasumi, Y.; Ido, T.; Kojima, M.; Toi, K.; JIPPT-IIU Group

2011-03-01

266

Lagrangian fluid description with simple applications in compressible plasma and gas dynamics  

Microsoft Academic Search

The Lagrangian fluid description, in which the dynamics of fluids is formulated in terms of trajectories of fluid elements, not only presents an alternative to the more common Eulerian description but has its own merits and advantages. This aspect, which seems to be not fully explored yet, is getting increasing attention in fluid dynamics and related areas as Lagrangian codes

Hans Schamel

2004-01-01

267

CHEMKIN-III: A FORTRAN chemical kinetics package for the analysis of gas-phase chemical and plasma kinetics.  

National Technical Information Service (NTIS)

This document is the user's manual for the third-generation CHEMKIN package. CHEMKIN is a software package whose purpose is to facilitate the formation, solution, and interpretation of problems involving elementary gas-phase chemical kinetics. It provides...

R. J. Kee F. M. Rupley E. Meeks J. A. Miller

1996-01-01

268

Obliquely propagating solitary kinetic Alfven wave in a collisional dusty plasma  

SciTech Connect

An obliquely propagating solitary kinetic Alfven wave in a low beta dusty plasma (beta<plasma is re-examined. It is found that there is an upper limit of the possible Alfvenic Mach velocity, imposed by dust particles. The Mach number lies between l{sub z} and l{sub z}/sq root(N{sub d}), where l{sub z} is the directional cosine and N{sub d} is the dust particle charge density. In the collisional case, the same upper limit of the Mach velocity is found, and the solitary wave turns into an oscillating double layer. The damping scale and the size of the oscillation structure increase with increasing dust particle charge density. The damping scale and the size of the oscillation structure are estimated by using the virial theorem.

Woo, M. H.; Ryu, C.-M. [Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Choi, C.-R. [Department of Physics, Korea Advanced Institute of Science and Technology, Taejon 305-701 (Korea, Republic of)

2010-05-15

269

Kinetic Alfven wave instability in a Lorentzian dusty plasma: Non-resonant particle approach  

SciTech Connect

Analysis of the electromagnetic streaming instability is carried out which is related to the cross field drift of kappa distributed ions. The linear dispersion relation for electromagnetic wave using Vlasov-fluid equations in a dusty plasma is derived. Modified two stream instability (MTSI) in a dusty plasma has been discussed in the limit {omega}{sub pd}{sup 2}/c{sup 2}k{sub perpendicular}{sup 2}<<1. Numerical calculations of the growth rate of instability have been carried out. Growth rates of kinetic Alfven instability are found to be small as compared to MTSI. Maximum growth rates for both instabilities occur in oblique directions for V{sub 0}{>=}V{sub A}. It is shown that the presence of both the charged dust particles and perpendicular ion beam sensibly modify the dispersion relation of low-frequency electromagnetic wave. The dispersion characteristics are found to be insensible to the superthermal character of the ion distribution function. Applications to different intersteller regions are discussed.

Rubab, N.; Biernat, H. K. [Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, A-8042 Graz (Austria); Institute of Physics, University of Graz, Universitaetplatz 5, A-8010 Graz (Austria); Erkaev, V. [Institute of Computational Modelling, 660036 Krasnoyarsk, Russia and Siberian Federal University, 660041 Krasnoyarsk (Russian Federation); Langmayr, D. [Virtual Vehicle Competence Center (vif), Inffeldgasse 21a, 8010 Graz (Austria)

2011-07-15

270

Kinetic modeling of electronically enhanced reaction pathways in Plasma Assisted Combustion  

NASA Astrophysics Data System (ADS)

The use of plasma energy to enhance and control the chemical reactions during combustion, a technology referred to as ``plasma assisted combustion'' (PAC), can result in a variety of beneficial effects: e.g. stable lean operation, pollution reduction, and wider range of p-T operating conditions. While experimental evidence abounds, theoretical understanding of PAC is at best incomplete, and numerical tools still lack in reliable predictive capabilities. In the context of a joint experimental-numerical effort at Michigan State University, we present here a modular Python framework dedicated to the dynamic optimization of non-equilibrium PAC systems. We first describe a novel kinetic global model, which aims at exploring scaling laws in parameter space, as well as the effect of a non-Maxwellian electron energy distribution function (EEDF). With such a model, we reproduce literature results and we critically review the effect of data uncertainty and limiting assumptions. Then, we explore means of measuring a non-Maxwellian EEDF through the use of a detailed collisional-radiative model, coupled to optical emission spectroscopy. Finally, we investigate the effect of different numerical integrators, as well as customized routines specifically designed to solve stiff sparse ODE systems.

Parsey, Guy; Gü?lü, Yaman; Verboncoeur, John; Christlieb, Andrew

2012-10-01

271

Kinetic simulations of intense light pulses generated by Brillouin backscattering in laser-plasma interaction  

NASA Astrophysics Data System (ADS)

Due to their extremely high damage threshold, plasmas can sustain much higher light intensities than conventional solid state optical materials. Because of this, lately much attention has been devoted to the possibility of using parametric instabilities in plasmas to generate very intense light pulses in a low-cost way. Although short-pulse amplification based on the Raman approach has been successful and goes back a long time, it is shown that using Brillouin in the so called strong-coupling regime (sc-SBS) has several advantages and is very well suited to amplify and compress laser seed pulses on short distances to very high intensities. We present here recent multi-dimensional kinetic simulations that show the feasibility of achieving amplified light pulses of up to 1018W/cm2. Contrary to what was traditionally thought, this scheme is able to amplify pulses of extremely short duration. Although seed amplification via sc-SBS has already been shown experimentally, these results suggest further experimental exploration, in order to improve the energy transfer.

Riconda, C.; Weber, S.; Fuchs, J.; Lancia, L.; Marquès, J.-R.; Mourou, G.

2013-05-01

272

Frequency dependent ion kinetics in a 300 mm dual-frequency capacitively coupled plasma reactor  

NASA Astrophysics Data System (ADS)

Argon ion kinetics were measured in a dual frequency, capacitively coupled 300 mm chamber. Laser induced fluorescence measurements of the argon ion metastable lineshape yield information on the ion temperature, density and drift velocity. The spatially-resolved LIF technique is a nonperturbative probe to investigate energy deposition mechanisms, ion energy distribution functions, charge exchange reactions, neutral heating, and plasma potential gradients within the plasma. This talk will discuss ion characteristics for a single rf frequency drive (13, 60 and 160 MHz), combinations of rf drive frequencies, as well as scaling with pressure (10 -- 70 mTorr) , rf power, and radial position. We find that the ion density increased linearly with rf power, as did the electron density, indicating the ion metastable state is formed from direct impact ionization. The ion temperature was on the order of 500 K. Radially resolved ion drift velocity measurements show the radial drift velocity can be lower at 60 MHZ than 13 MHz. Additional details will be discussed. This work was supported by Applied Materials and Sandia National Laboratories, a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Hebner, G. A.; Barnat, E. V.; Miller, P. A.; Paterson, A. M.; Holland, J. P.

2006-10-01

273

Electron kinetics and non-Joule heating in near-collisionless inductively coupled plasmas  

SciTech Connect

Electron kinetics in an inductively coupled plasma sustained by a coaxial solenoidal coil is studied for the near-collisionless regime when the electron mean free path is large compared to the tube radius. Emphasis is placed on the influence of the oscillatory magnetic field induced by the coil current and the finite dimension of the plasma on electron heating and formation of the electron distribution function (EDF). A nonlocal approach to the solution of the Boltzmann equation is developed for the near-collisionless regime when the traditional two-term Legendre expansion for the EDF is not applicable. Dynamic Monte Carlo (DMC) simulations are performed to calculate the EDF and electron heating rate in argon in the pressure range 0.3{endash}10 mTorr and driving frequency range 2{endash}40 MHz, for given distributions of electromagnetic fields. The wall potential {phi}{sub w} in DMC simulations is found self-consistently with the EDF. Simulation results indicate that the EDF of trapped electrons with total energy {var_epsilon}{lt}e{phi}{sub w} is almost isotropic and is a function solely of {var_epsilon}, while the EDF of untrapped electrons with {var_epsilon}{gt}e{phi}{sub w} is notably anisotropic and depends on the radial position. These results are in agreement with theoretical analysis. {copyright} {ital 1997} {ital The American Physical Society}

Kolobov, V.I. [Plasma Processing Laboratory, Department of Chemical Engineering, University of Houston, Houston, Texas 77204-4792 (United States); Lymberopoulos, D.P. [Applied Materials, 3100 Bowers Avenue, Santa Clara, California 95054 (United States); Economou, D.J. [Plasma Processing Laboratory, Department of Chemical Engineering, University of Houston, Houston, Texas 77204-4792 (United States)

1997-03-01

274

Plasma kinetics, tissue distribution, and cerebrocortical sources of reverse triiodothyronine in the rat.  

PubMed

Studies in vitro have shown that rT3 is a potent and competitive inhibitor of T4 5'-deiodination (5'D). Recent studies in vivo have shown that cerebrocortical (Cx) T4 5'D-type II (5'D-II) activity [propylthiouracil (PTU) insensitive pathway], is reduced by T4 and rT3, the latter being more potent than T3 in Cx 5'D-II suppression. Some other reports had described rT3 production in rat brain as a very active pathway of thyroid hormone metabolism. To examine the possibility that rT3 plays a physiological role in regulating Cx 5'D-II, we have explored rT3 plasma kinetics, plasma to tissue exchange, and uptake by tissues in the rat, as well as the metabolic routes of degradation and the sources of rT3 in cerebral cortex (Cx). Plasma and tissue levels were assessed with tracer [125I]rT3. Two main compartments were defined by plasma disappearance curves in euthyroid rats (K1 = -6.2 h-1 and K2 = -0.75 h-1). In Cx of euthyroid rats, [125I]rT3 peaked 10 min after iv injection, tissue to plasma ratio being 0.016 +/- 0.004 (SE). In thyroidectomized rats, plasma and tissue [125I]rT3 concentrations were higher than in euthyroid rats, except for the Cx that did not change. PTU caused further increases in all the tissues studied, except for the Cx and the pituitaries of thyroidectomized rats. From the effect of blocking 5'D-I with PTU or reducing its activity by making the animals hypothyroid, we concluded that 5'D-I accounts for most of the rT3 clearance from plasma. In contrast, in Cx and pituitary the levels of rT3 seem largely affected by 5'D-II activity. Since the latter results suggest that plasma rT3 does not play a major role in determining rT3 levels in these tissues, we explored the sources of rT3 in Cx using [125I]T4. The [125I]rT3 (T4) to [125I]T4 ratio remained constant at 0.03 from 1 up to 5 h after injection of [125I]T4. From plasma levels of T4 and rT3, Cx concentration was calculated to be 30 pg rT3/g Cx in euthyroid rats, more than 98% locally produced from T4 deiodination. We conclude that rT3 has a very rapid metabolism, mainly attributed to 5'D-I activity, but that 5'D-II could also play a role in certain tissues. Nearly all rT3 present in Cx is locally derived from T4. PMID:3996308

Obregon, M J; Larsen, P R; Silva, J E

1985-06-01

275

CONFERENCE DESCRIPTION Theory of Fusion Plasmas: Varenna-Lausanne International Workshop  

NASA Astrophysics Data System (ADS)

The Joint Varenna-Lausanne international workshop on Theory of Fusion Plasmas takes place every other year in a place particularly favourable for informal and in-depth discussions. Invited and contributed papers present state-of-the-art research in theoretical plasma physics, covering all domains relevant to fusion plasmas. This workshop always welcomes a fruitful mix of experienced researchers and students, to allow a better understanding of the key theoretical physics models and applications. Theoretical issues related to burning plasmas Anomalous Transport (Turbulence, Coherent Structures, Microinstabilities) RF Heating and Current Drive Macroinstabilities Plasma-Edge Physics and Divertors Fast particles instabilities Further details: http://Varenna-Lausanne.epfl.ch The conference is organized by: Centre de Recherches en Physique des Plasmas, Ecole Polytechnique Fédérale de Lausanne, Association EURATOM - Confédération Suisse 'Piero Caldirola' International Centre for the Promotion of Science and International School of Plasma Physics Istituto di Fisica del Plasma del CNR, Milano Editors: X Garbet (CEA, Cadarache, France) and O Sauter (CRPP-EPFL, Lausanne, Switzerland)

Garbet, X.; Sauter, O.

2010-12-01

276

Kinetic and infrared spectroscopic studies of ionic reactions of interest to various plasma media  

NASA Astrophysics Data System (ADS)

A selected ion flow tube (SIFT) and a Flowing Afterglow (FA) with extensive spectroscopic facilities were used in the kinetic and dynamic studies of gas phase reactions between ions, electrons, and neutral atoms and molecules. Along with the interest, these reactions have importance in planetary atmospheres, interstellar gas clouds, circumstellar shells, comets, laser plasmas, combustion flames, and etchant plasmas. SIFT studies of H3O+(H2O)0,1 reactions with sulfides and thiols were performed because of their significance as atmospheric pollutants and in molecular synthesis in interstellar gas clouds. The study shows that proton transfer and ligand switching with internal proton transfer are important mechanisms. Furthermore, it indicates that the proton affinities of n- and iso-propanethiol are larger than previously thought. Using these and other data on H3O+ proton transfer reactions and our experimental determination of the first complete branching ratios for the dissociative electron-ion recombination of H3O +, a limited chemical model that predicts the H2O abundance in some of the giant interstellar molecular clouds was developed. The product distribution shows that the H2O channel is 7 times smaller than previously assumed and that fragmentation into three body channels is considerable. The model predicts an H2O abundance in good agreement with recent observations and that proton transfer to neutral species is a significant loss process for H3O+. Dissociative charge transfer in reactions of CCl4 and SF 6 with common plasma ions was also investigated. Kinetic and product ion information was used in conjunction with photoelectron- photoion coincidence data, from the literature, to provide insight into the fragmentation of excited CC14+ and SF6+ ions. The degree of fragmentation and the energy thresholds at which product ions are observed are generally consistent with a long range mechanism in which the energy goes into fragmentation. A technique for observing IR emissions from gas phase ionic reactions was developed. This method was proven by studying well-characterized neutral reactions and the associative detachment reaction of Cl- with H atoms. Excellent agreement of the vibrational product state populations was obtained with previous studies. Data acquisition times were reduced by a factor of four while resolution improved by an order of magnitude.

Williams, Ted Lee

1999-11-01

277

Theoretical modeling of molecular and electron kinetic processes. Volume 1: Theoretical formulation of analysis and description of computer program  

Microsoft Academic Search

This report describes and documents a comprehensive and reasonably general computer analysis applicable to a broad class of transient, electrically excited laser systems. The theoretical model is formulated, for a spatially homogeneous medium, in terms of the coupled set of equations which describe the molecular kinetics, electron kinetics, external discharge circuit, and optical radiative extraction. One of the unique features

W. B. Lacina

1979-01-01

278

Pulsar electrodynamics: Relativistic kinetic theory of radiative plasmas—collective phenomena and their radiation  

NASA Astrophysics Data System (ADS)

The classical modeling of radiation by accelerated charged particles in pulsars predicts a cutoff in photon energy at around 25 GeV. While this is broadly consistent with observations, the classical treatment is not self-consistent, and cannot be extended to explain the rare high-energy detections of photons in the 100s of GeV range. In this paper we revisit the theoretical modeling of high-energy radiation processes in very strong electromagnetic fields, in the context of both single particles and collective plasmas. There are no classical constraints on this description. We find that there is indeed a critical energy of around 50 GeV that arises naturally in this self-consistent treatment, but rather than being a cutoff, this critical energy signals a transition from radiation that is classical to a quasiquantum description, in which the particle is able to radiate almost its total energy in a single event. This new modeling therefore places pulsar radiation processes on a more secure physical basis, and admits the possibility of the production of TeV photons in a self-consistent way.

da Costa, A. A.; Diver, D. A.; Laing, E. W.; Stark, C. R.; Teodoro, L. F. A.

2011-01-01

279

Self-Consistent Kinetic Approach for Low Frequency and Quasi-static Electromagnetic Perturbations in Magnetic-Mirror Confined Plasmas  

NASA Astrophysics Data System (ADS)

We describe a new self-consistent kinetic approach of collisionless plasmas. The basic equations are obtained from a linearization of the cyclotron and bounce averaged Vlasov and Maxwell equations. In the low frequency limit the Gauss equation is shown to be equivalent to the Quasi-Neutrality Condition (QNC). First we describe the work of Hurricane et al., 1995b, who investigated the effect of stochasticity on the stability of ballooning modes. An expression for the energy principle is obtained in the stochastic case, with comparisons with the adiabatic case. Notably, we show how the non adiabaticity of ions allows to recover a MHD-like theory with a modification of the polytropic index, for waves with frequencies smaller than the bounce frequency of protons. The stochasticity of protons can be due, in the far plasma sheet (beyond 10-12 RE, RE being the Earth radius), to the development of thin Current Sheet (CS) with a curvature radius that becomes smaller than the ion Larmor radius. Conversely the near Earth plasma sheet (6-8 RE), where the curvature radius is larger, is expected to be in the adiabatic regime. We give a description of slowly evolving (quasi-static) magnetic configurations, during the formation of high altitudes CS's, for instance during substorm growth phase in the Earth magnetosphere, and tentatively during the formation of CS's in the solar corona. Thanks to the use of a simple equilibrium magnetic field, a 2D dipole, the linear electromagnetic perturbations are computed analytically as functions of a forcing electrical current. The QNC, which is valid for long perpendicular wavelength electromagnetic perturbations (k?D1 where ?D is the Debye length), is developed via an expansion in the small parameter Te/Ti. To the lowest order in Te/Ti (Te/Ti->0) we find that the enforcement of the QNC implies the presence of an electrostatic potential which is constant along the field line, but varies across it. The corresponding potential electric field is perpendicular to the magnetic field; it corresponds to the self-consistent response of the plasma to an externally applied time varying perturbation. This potential electric field tends to reduce the effect of the induced electric field, hence producing a partial ``shielding'' of the motion that would correspond to the induced electric field if it was alone. The effect of the total azimuthal electric field, obtained from the QNC, on the radial transport of the plasma is investigated. We show that the direction of the perpendicular electric field varies with the latitude. As a consequence, for a time dependent transport, the equatorial electric field cannot usually be mapped onto the low altitude electric field (ionosphere for the Earth), even in the absence of a parallel electric field. Present calculations show that during the substorm growth phase, the (total) azimuthal electric field is directed eastward, close to the equator, and westward off-equator. Thus, large equatorial pitch-angle particles drift tailward whereas small pitch-angle particles drift earthward. Finally, to the next order in Te/Ti, we show that the formation of the thin current sheet lead to the development of a finite parallel electric field. Thus time variations in high altitude CS's are coupled to the low altitude regions (ionosphere for the Earth) via (i) an electrostatic component constant along the magnetic field line and via (ii) the parallel electric fields. Associated with this parallel electric field, a parallel current develops. We suggest that this current drives an instability at frequencies well above that imposed by the forcing current. Unstable waves are electromagnetic and have frequencies of the order of the proton gyrofrequency. Given their large amplitudes these waves can produce a fast electron and ion diffusion which modify the electrical currents in a such manner that the reconfiguration of the magnetic field occurs.

Pellat, Rene; Le Contel, Olivier; Roux, Alain; Perraut, Sylvaine; Hurricane, Omar; Coroniti, Ferdinand V.

280

Ulysses solar wind plasma investigation: Description and initial in-ecliptic results.  

National Technical Information Service (NTIS)

During the in-ecliptic flight of Ulysses from the Earth toward its encounter with Jupiter, the Los Alamos solar wind plasma experiment has performed well. Briefly described, the instrumentation contains two independent electrostatic analyzers, one for ion...

S. J. Bame J. L. Phillips D. J. McComas J. T. Gosling B. E. Goldstein

1991-01-01

281

On Supergravity Description of Boost-Invariant Conformal Plasma at Strong Coupling  

SciTech Connect

We study string theory duals of the expanding boost invariant conformal gauge theory plasmas at strong coupling. The dual supergravity background is constructed as an asymptotic late-time expansion, corresponding to equilibration of the gauge theory plasma. The absence of curvature singularities in the first few orders of the late-time expansion of the dual gravitational background unambiguously determines the equilibrium equation of the state, and the shear viscosity of the gauge theory plasma. While the absence of the leading pole singularities in the gravitational curvature invariants at the third order in late-time expansion determines the relaxation time of the plasma, the subleading logarithmic singularity can not be canceled within a supergravity approximation. We comment on the possible interpretations of this singularity.

Buchel, Alex [Department of Applied Mathematics, University of Western Ontario London, Ontario N6A 5B7 (Canada); Perimeter Institute for Theoretical Physics, Waterloo, Ontario N2J 2W9 (Canada)

2008-07-28

282

Multimode Description of the Non-Linear Evolution of Modulational Instabilities in Plasmas.  

National Technical Information Service (NTIS)

A general discussion of modulational instabilities in plasmas is given. The basic mechanism is a four wave interaction and examples include the Langmuir modulational instability, the oscillating two-stream instability and the filamentation of laser light ...

R. Bingham C. N. Lashmore-Davies

1984-01-01

283

Descriptions of a linear device developed for research on advanced plasma imaging and dynamics  

SciTech Connect

The research on advanced plasma imaging and dynamics (RAPID) device is a newly developed linear electron cyclotron resonance (ECR) plasma device. It has a variety of axial magnetic field profiles provided by eight water-cooled magnetic coils and two dc power supplies. The positions of the magnetic coils are freely adjustable along the axial direction and the power supplies can be operated with many combinations of electrical wiring to the coils. A 6 kW 2.45 GHz magnetron is used to produce steady-state ECR plasmas with central magnetic fields of 875 and/or 437.5 G (second harmonic). The cylindrical stainless steel vacuum chamber is 300 mm in diameter and 750 mm in length and has eight radial and ten axial ports including 6-in. and 8-in. viewing windows for heating and diagnostics. Experimental observation of ECR plasma heating has been recently carried out during the initial plasma operation. The main diagnostic systems including a 94 GHz heterodyne interferometer, a high-resolution 25 channel one-dimensional array spectrometer, a single channel survey spectrometer, and an electric probe have been also prepared. The RAPID device is a flexible simulator for the understanding of tokamak edge plasma physics and new diagnostic system development. In this work, we describe the RAPID device and initial operation results.

Chung, J.; Lee, K. D.; Seo, D. C.; Nam, Y. U.; Ko, W. H.; Lee, J. H. [National Fusion Research Institute, Gwahangno 113, Daejeon 305-333 (Korea, Republic of); Choi, M. C. [Korea Basic Science Institute, 804-1 Ochang, Cheongwon 363-883 (Korea, Republic of)

2009-10-15

284

Kinetics of plasma membrane and mitochondrial alterations in cells undergoing apoptosis  

SciTech Connect

Programmed cell death or apoptosis is characterized by typical morphological alterations. By transmission electron microscopy, apoptotic cells are identified by condensation of the chromatin in tight apposition to the nuclear envelope, alteration of the nuclear envelope and fragmentation of the nucleus, whereas integrity of the plasma membrane and organelles is preserved. Conversely cells undergoing necrosis display and early desintegration of cytoplasmic membrane and swelling of mitochondria. In this study we assessed by flow cytometry the sequential alterations of forward angle light scatter, 90{degrees} light scatter, and fluorescence associated with fluorescein diacetate, rhodamine 123, and propidium iodide in two human B cell lines undergoing apoptosis induced by the topoisomerase II inhibitor VP-16. The kinetics of these modifications were compared to those of cells undergoing necrosis induced by the topoisomerase II inhibitor VP-16. The kinetics of these modifications were compared to those of cells undergoing necrosis induced by sodium azide. At the same time intervals, cells were examined by transmission electron microscopy and by UV microscopy after staining with Hoechst 33342. We report that sequential changes in light scatters and fluorescein diacetate are similar in cells undergoing apoptosis or necrosis, whereas apoptosis is characterized by a slightly delayed decrease of mitochondrial activity as assessed by rhodamine 123 staining. Surprisingly, a part of cells undergoing apoptosis displayed an early uptake of propidium iodide followed by a condensation and then a fragmentation of their nuclei. It is concluded that uptake of propidium iodide is a very early marker of cell death which does not discriminate between necrosis and apoptosis. Along with biochemical criteria, nuclear morphology revealed by staining with Hoechst 33342 would seem to be of the most simple and most discriminative assay of apoptosis. 33 refs., 5 figs., 1 tab.

Lizard, G.; Fournel, S.; Genestier, L.; Dhedin, N. [Hospital Edouard Herriot, Lyon (France)] [and others

1995-11-01

285

Fast, kinetically self-consistent simulation of RF modulated plasma boundary sheaths  

NASA Astrophysics Data System (ADS)

A mathematical model is presented which enables the efficient, kinetically self-consistent simulation of RF modulated plasma boundary sheaths in all technically relevant discharge regimes. It is defined on a one-dimensional geometry where a Cartesian x-axis points from the electrode or wall at xE ? 0 towards the plasma bulk. An arbitrary endpoint xB is chosen ‘deep in the bulk’. The model consists of a set of kinetic equations for the ions, Boltzmann's relation for the electrons and Poisson's equation for the electrical field. Boundary conditions specify the ion flux at xB and a periodically—not necessarily harmonically—modulated sheath voltage V(t) or sheath charge Q(t). The equations are solved in a statistical sense. However, it is not the well-known particle-in-cell (PIC) scheme that is employed, but an alternative iterative algorithm termed ensemble-in-spacetime (EST). The basis of the scheme is a discretization of the spacetime, the product of the domain [xE, xB] and the RF period [0, T]. Three modules are called in a sequence. A Monte Carlo module calculates the trajectories of a large set of ions from their start at xB until they reach the electrode at xE, utilizing the potential values on the nodes of the spatio-temporal grid. A harmonic analysis module reconstructs the Fourier modes nim(x) of the ion density ni(x, t) from the calculated trajectories. A field module finally solves the Boltzmann-Poisson equation with the calculated ion densities to generate an updated set of potential values for the spatio-temporal grid. The iteration is started with the potential values of a self-consistent fluid model and terminates when the updates become sufficiently small, i.e. when self-consistency is achieved. A subsequent post-processing determines important quantities, in particular the phase-resolved and phase-averaged values of the ion energy and angular distributions and the total energy flux at the electrode. A drastic reduction of the computational effort compared with PIC calculations is achieved. As a first application of the new model, the influence of ion inertia on the dynamics of a collisionless sheath is studied and a comparison of the simulated ion energy distribution with published analytical solutions is performed.

Shihab, Mohammed; Ziegler, Dennis; Brinkmann, Ralf Peter

2012-05-01

286

Products and bioenergy from the pyrolysis of rice straw via radio frequency plasma and its kinetics.  

PubMed

The radio frequency plasma pyrolysis technology, which can overcome the disadvantages of common pyrolysis methods such as less gas products while significant tar formation, was used for pyrolyzing the biomass waste of rice straw. The experiments were performed at various plateau temperatures of 740, 813, 843 and 880K with corresponding loading powers of 357, 482, 574 and 664W, respectively. The corresponding yields of gas products (excluding nitrogen) from rice straw are 30.7, 56.6, 62.5 and 66.5wt.% with respect to the original dried sample and the corresponding specific heating values gained from gas products are about 4548, 4284, 4469 and 4438kcalkg(-1), respectively, for the said cases. The corresponding combustible portions remained in the solid residues are about 64.7, 35, 28.2 and 23.5wt.% with specific heating values of 4106, 4438, 4328 and 4251kcalkg(-1) with respective to solid residues, while that in the original dried sample is 87.2wt.% with specific heating value of 4042kcalkg(-1). The results indicated that the amount of combustibles converted into gas products increases with increasing plateau temperature. The kinetic model employed to describe the pyrolytic conversion of rice straw at constant temperatures agrees well with the experimental data. The best curve fittings render the frequency factor of 5759.5s(-1), activation energy of 74.29kJ mol(-1) and reaction order of 0.5. Data and information obtained are useful for the future design and operation of pyrolysis of rice straw via radio frequency plasma. PMID:19046633

Tu, Wen-Kai; Shie, Je-Lung; Chang, Ching-Yuan; Chang, Chiung-Fen; Lin, Cheng-Fang; Yang, Sen-Yeu; Kuo, Jing T; Shaw, Dai-Gee; You, Yii-Der; Lee, Duu-Jong

2008-11-30

287

Fokker-Planck description of the scattering of radio frequency waves at the plasma edge  

SciTech Connect

In magnetic fusion devices, radio frequency (rf) waves in the electron cyclotron (EC) and lower hybrid (LH) range of frequencies are being commonly used to modify the plasma current profile. In ITER, EC waves are expected to stabilize the neoclassical tearing mode (NTM) by providing current in the island region [R. Aymar et al., Nucl. Fusion 41, 1301 (2001)]. The appearance of NTMs severely limits the plasma pressure and leads to the degradation of plasma confinement. LH waves could be used in ITER to modify the current profile closer to the edge of the plasma. These rf waves propagate from the excitation structures to the core of the plasma through an edge region, which is characterized by turbulence--in particular, density fluctuations. These fluctuations, in the form of blobs, can modify the propagation properties of the waves by refraction. In this paper, the effect on rf due to randomly distributed blobs in the edge region is studied. The waves are represented as geometric optics rays and the refractive scattering from a distribution of blobs is formulated as a Fokker-Planck equation. The scattering can have two diffusive effects--one in real space and the other in wave vector space. The scattering can modify the trajectory of rays into the plasma and it can affect the wave vector spectrum. The refraction of EC waves, for example, could make them miss the intended target region where the NTMs occur. The broadening of the wave vector spectrum could broaden the wave generated current profile. The Fokker-Planck formalism for diffusion in real space and wave vector space is used to study the effect of density blobs on EC and LH waves in an ITER type of plasma environment. For EC waves the refractive effects become important since the distance of propagation from the edge to the core in ITER is of the order of a meter. The diffusion in wave vector space is small. For LH waves the refractive effects are insignificant but the diffusion in wave vector space is important. The theoretical model is general enough to study the effect of density blobs on all propagating cold plasma waves.

Hizanidis, Kyriakos; Kominis, Yannis; Tsironis, Christos [School of Electrical and Computer Engineering, National Technical University of Athens, Athens GR 15773 (Greece); Ram, Abhay K. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2010-02-15

288

New chemical kinetics for description of chemical noise in small, heterogeneous biological systems: Beyond the paradigm of the rate constant concept  

NASA Astrophysics Data System (ADS)

We introduce a novel chemical kinetics for quantitative description of chemical fluctuations in a small, heterogeneous biological reaction system. At first, we discuss the recently proposed renewal chemical kinetics, and its application to quantitative interpretation of the randomness in fluctuating enzymatic turnover times of a-galactosidase. From the analysis of the randomness parameter data of the single enzyme reaction, one can extract valuable quantitative information about the enzyme reaction system, beyond the reach of the conventional Michaelis-Menten analysis. Next, we discuss a new universal behavior in the time dependence of the chemical fluctuation of product density for a small, heterogeneous reaction system, which is predicted from an exact analytic study for a general reaction model and confirmed by stochastic simulation results. We also discuss the dependence of the chemical noise on substrate concentrations for a heterogeneous enzyme reaction system, which turns out qualitatively different from that for a homogeneous enzyme reaction system.

Sung, Jaeyoung

2012-02-01

289

Evidence for plasma transport via kinetic Alfven waves at the magnetopause: An event study of THEMIS observations  

NASA Astrophysics Data System (ADS)

We investigated the plasma transport induced by kinetic Alfven waves (KAWs) as a candidate process of efficient plasma entry across the magnetopause during northward IMF periods. Due to the lack of observational evidence based on particle data, it remains unclear even whether KAWs really transport the plasma into the magnetosphere. First we show the physical process of the plasma transport via KAWs including the finite beta effect. A particle satisfying Cerenkov resonance condition experiences ExB drift via parallel electric field fluctuations and gradient-B drift via parallel magnetic field fluctuations, both resulting in cross-field transport. This process occurs selectively for particles in a specific velocity space. Then we report THEMIS observations of the dayside magnetopause at which kinetic Alfven turbulence exists. By comparing ion velocity distribution functions obtained in the magnetosheath and the low-latitude boundary layer, we found that cold ions in the low-latitude boundary layer result from the selective transport of the magnetosheath ions as expected from the theory of the KAW-induced transport. This is the first time to show by particle data that KAWs can indeed transport plasma across the magnetopause.

Izutsu, T.; Hasegawa, H.; Nakamura, T.; Fujimoto, M.; McFadden, J. P.; Auster, H.; Angelopoulos, V.

2011-12-01

290

Co-existence of whistler waves with kinetic Alfven wave turbulence for the high-beta solar wind plasma  

SciTech Connect

It is shown that the dispersion relation for whistler waves is identical for a high or low beta plasma. Furthermore, in the high-beta solar wind plasma, whistler waves meet the Landau resonance with electrons for velocities less than the thermal speed, and consequently, the electric force is small compared to the mirror force. As whistlers propagate through the inhomogeneous solar wind, the perpendicular wave number increases through refraction, increasing the Landau damping rate. However, the whistlers can survive because the background kinetic Alfven wave (KAW) turbulence creates a plateau by quasilinear (QL) diffusion in the solar wind electron distribution at small velocities. It is found that for whistler energy density of only {approx}10{sup -3} that of the kinetic Alfven waves, the quasilinear diffusion rate due to whistlers is comparable to KAW. Thus, very small amplitude whistler turbulence can have a significant consequence on the evolution of the solar wind electron distribution function.

Mithaiwala, Manish; Crabtree, Chris; Ganguli, Gurudas [Plasma Physics Division, Naval Research Laboratory, Washington, DC 20375-5346 (United States); Rudakov, Leonid [Icarus Research Inc., P.O. Box 30780, Bethesda, Maryland 20824-0780 (United States)

2012-10-15

291

Forward and backward test-kinetic simulations of non-Maxwellian velocity distribution functions in space plasmas  

NASA Astrophysics Data System (ADS)

Test-kinetic simulations provide a useful tool to investigate plasma dynamics for various configurations of the electromagnetic field. This method gives useful information about the plasma kinetic structure in complex situations when self-consistent techniques are not practical. In this paper we make a review of forward and backward test-kinetic method applied to compute the velocity distribution function (VDF) of protons of a plasma stream in the vicinity of a magnetic discontinuity. We consider two different profiles of the electric field. The forward method is used first to investigate the formation of an energy-dispersed structure with typical ring-shaped and crescent-shaped velocity distribution functions formed at the edges of the cloud by the gradient-B drift. The backward method is applied to test the VDFs in the same spatial regions investigated with the forward approach. We compare in detail the results obtained with the forward and backward approaches. In the forward approach the velocity distribution function is computed for a two-dimensional spatial bin. In order to obtain results consistent with the forward approach, the distribution function computed with the backward approach is averaged over a spatial bin with the same size as for the forward method and using a two-dimensional trapezoidal integration scheme. It is shown that the forward and backward test-kinetic simulations lead to similar results, except for the situations when the VDFs are computed for spatial bins in which the velocity distribution function varies sharply. The kinetic features revealed by the numerical solutions have similarities with in-situ distribution functions observed by Cluster satellites in the magnetotail, close to the neutral sheet.

Voitcu, Gabriel; Echim, Marius; Marchand, Richard

2013-04-01

292

Advanced oxidation processes; Description of a kinetic model for the oxidation of hazardous materials in aqueous media  

SciTech Connect

A model is presented that describes the kinetics of the oxidation of micropollutants in water with the combination of ozone and hydrogen peroxide in a sparged, semibatch reactor. The model is based on known reactions of the 0{sub 3}/H{sub 2}O{sub 2} system plus mass-transfer characteristics of the reactor. The principal kinetic species for micropollutant oxidation is assumed to be the hydroxyl radical. The model is tested and validated in distilled water spiked with an excess of bicarbonate, a known hydroxyl radical scavenger.

Glaze, W.H. (Engineering, School of Public Health, The Univ of North Carolina at Chapel Hill, Chapel Hill, NC (US)); Kang, J.W. (Environmental Science Engineering Program, School of Public Health, Univ of California, Los Angeles, CA (US))

1989-11-01

293

Cell-Free Fetal DNA in Maternal Plasma during Physiological Single Male Pregnancies: Methodology Issues and Kinetics  

Microsoft Academic Search

Objective: To analyze methodological influences and characterize the concentrations of cell-free fetal DNA (cffDNA) circulating in maternal plasma at different gestational ages in physiological pregnancies. Methods: We investigated 238 independent samples from single male-bearing pregnancies of different gestation age. In the other 50 pregnancies, the samples were collected three times during pregnancy (at all trimesters) to evaluate the kinetics of

Ales Horinek; Marie Korabecna; Ales Panczak; Zdenka Ulcova Gallova; Kamila Nouzova; Pavel Calda; Miroslava Hancarova

2008-01-01

294

Self-Consistent Kinetic Approach for Low Frequency and Quasi-static Electromagnetic Perturbations in Magnetic-Mirror Confined Plasmas  

Microsoft Academic Search

We describe a new self-consistent kinetic approach of collisionless plasmas. The basic equations are obtained from a linearization\\u000a of the cyclotron and bounce averaged Vlasov and Maxwell equations. In the low frequency limit the Gauss equation is shown\\u000a to be equivalent to the Quasi-Neutrality Condition (QNC). First we describe the work of Hurricane et al., 1995b, who investigated the effect

Rene Pellat; Olivier Le Contel; Alain Roux; Sylvaine Perraut; Omar Hurricane; Ferdinand V. Coroniti

2000-01-01

295

Kinetics of Photon Radiation off an e-e+-Plasma Created from the Vacuum in a Strong Laser Field  

NASA Astrophysics Data System (ADS)

We consider the one-photon annihilation mechanism in a electron - positron quasiparticle plasma (EPP) created from the vacuum in a strong subcritical laser field due to the dynamical Schwinger mechanism. On the basis of a kinetic theory approach we show that the secondary photons have a radiation spectrum proportional to 1/k (flicker noise). This effect is very small for EPP excitations in the optical spectrum but can reach quite observable values in the gamma - ray region.

Blaschke, D. B.; Röpke, G.; Schmidt, S. M.; Smolyansky, S. A.; Tarakanov, A. V.

2011-06-01

296

Chemical kinetics and reactive species in atmospheric pressure helium-oxygen plasmas with humid-air impurities  

NASA Astrophysics Data System (ADS)

In most applications helium-based plasma jets operate in an open-air environment. The presence of humid air in the plasma jet will influence the plasma chemistry and can lead to the production of a broader range of reactive species. We explore the influence of humid air on the reactive species in radio frequency (rf)-driven atmospheric-pressure helium-oxygen mixture plasmas (He-O2, helium with 5000 ppm admixture of oxygen) for wide air impurity levels of 0-500 ppm with relative humidities of from 0% to 100% using a zero-dimensional, time-dependent global model. Comparisons are made with experimental measurements in an rf-driven micro-scale atmospheric pressure plasma jet and with one-dimensional semi-kinetic simulations of the same plasma jet. These suggest that the plausible air impurity level is not more than hundreds of ppm in such systems. The evolution of species concentration is described for reactive oxygen species, metastable species, radical species and positively and negatively charged ions (and their clusters). Effects of the air impurity containing water humidity on electronegativity and overall plasma reactivity are clarified with particular emphasis on reactive oxygen species.

Murakami, Tomoyuki; Niemi, Kari; Gans, Timo; O'Connell, Deborah; Graham, William G.

2013-02-01

297

Description of the kinetic enzymatic browning in banana ( Musa cavendish) slices using non-uniform color information from digital images  

Microsoft Academic Search

A novel methodology “fractal browning indicator” (FBI) is presented, that describes the enzymatic browning kinetic based on the use of irregular color patterns from banana slice images. It uses the fractal Fourier texture image value in a selected area, to calculate a fractal dimension (FD), which represents the complexity of color distribution. During the procedure, colors from digital images were

Roberto Quevedo; Oscar Díaz; Betty Ronceros; Franco Pedreschi; José Miguel Aguilera

2009-01-01

298

Spatially modulated phase in the holographic description of quark-gluon plasma.  

PubMed

We present a string theory construction of a gravity dual of a spatially modulated phase. Our earlier work shows that the Chern-Simons term in the five-dimensional Maxwell theory destabilizes the Reissner-Nordström black holes in anti-de Sitter space if the Chern-Simons coupling is sufficiently high. In this Letter, we show that a similar instability is realized on the world volume of 8-branes in the Sakai-Sugimoto model in the quark-gluon plasma phase. Our result suggests a new spatially modulated phase in quark-gluon plasma when the baryon density is above 0.8Nf??fm(-3) at temperature 150 MeV. PMID:21405455

Ooguri, Hirosi; Park, Chang-Soon

2011-02-11

299

Hybrid Description of Outflowing Ionospheric Plasma: A Monte Carlo\\/n-Moment Transport Equations Model  

Microsoft Academic Search

At terrestrial high latitudes, the plasma flows along ``open'' field lines, gradually going from a collision-dominated region into a collisionless region. Over several decades, the (fluid-like) generalized transport equations, TE, and the particle-based Monte Carlo, MC, approaches evolved as two of the most powerful simulation techniques that address this problem. In contrast to the computationally intensive Monte Carlo, the transport

J. Ji; A. R. Barakat; R. W. Schunk

2009-01-01

300

The GHIBLI plasma wind tunnel: Description of the new CIRA-PWT facility  

NASA Astrophysics Data System (ADS)

A new plasma wind tunnel is under construction at the Italian Aerospace Research Centre (CIRA) located at Capua. It is named GHIBLI and the plasma is generated by a segmented arc heater whose power is about 2 MW. Such a new facility will be able to perform test campaigns on models up to 80 mm in diameter, and may be used to develop researches in the aerospace field of the hypersonic plasma flows from the reentry technologies to the validation of CFD codes for the theoretical predictions of aerothermodynamic phenomena. Target of the present paper is the presentation of results obtained by means of CFD simulation by using the well-known FLUENT code, Such a code has been used to simulate the aerothermodynamic field inside the conical nozzle of the facility to obtain some analytical correlations (fits) between the main aerodynamic parameters at the nozzle exit, such as the Mach number, flow density, mass flow rate, etc. and the reservoir conditions inside the arc heater column, total pressure and total enthalpy. Such fits allow fast theoretical prediction of the facility operation parameters for given reservoir conditions.

Purpura, Carlo; Filippis, Federico De; Graps, Egidio; Trifoni, Eduardo; Savino, Raffaele

2007-06-01

301

A mean field description of reversed field pinch: equilibrium, dynamo, plasma heating and confinement  

NASA Astrophysics Data System (ADS)

Three simple physics constraints are applied to describe the reversed field pinch (RFP) in a mean field sense. These constraints are: (a) a steady state equilibrium, (b) a negative radial pressure gradient, and (c) a net volumetric source of mean field magnetic energy that is always locally negative. Using these constraints, realistic RFP equilibria are calculated, plasma heating profiles are determined, and the role of the dynamo in rearranging profiles can be described by a mean field one dimensional picture. The RFP exists in a near minimum energy state characterized by a mu profile (where ? identical to ? 0aJ.B/B2) that decreases to a small value at the plasma edge. The resulting RFP confinement picture has three regions: a poorly confined plasma core characterized by parallel (radial) transport and flux surfaces destroyed by m=1 tearing mode activity associated with dynamo relaxation, a medium confined edge limited by ideal pressure gradient driven modes, and a good confinement region located near the reversal layer. This good confinement region determines the global confinement characteristics of the RFP, and, if limited by resistive interchange modes, is consistent with the Conner-Taylor scaling that has provided a good fit to international RFP results

Werley, K. A.

1995-04-01

302

Spatiotemporal evolution and nonlinear kinetic simulations of stimulated Brillouin scattering  

Microsoft Academic Search

The spatiotemporal evolution of stimulated Brillouin scattering (SBS) in homogeneous plasmas and some aspects of the influence that nonlinear and kinetic effects have on the evolution of SBS were studied. A one-dimensional analytical linear model based on a fluid description of the plasma was developed initially. It was found that the threshold intensity of the absolute instability and the steady-state

Rodolfo E. Giacone

1998-01-01

303

Co-existence of Whistler Waves with Kinetic Alfven Wave Turbulence for the High-Beta Solar Wind Plasma  

NASA Astrophysics Data System (ADS)

It is shown that the dispersion relation for whistler waves is identical for a high or low beta plasma. Furthermore in the high-beta solar wind plasma whistler waves meet the Landau resonance with electrons for velocities less than the thermal speed, and consequently the electric force is small compared to the mirror force. As whistlers propagate through the inhomogeneous solar wind, the perpendicular wave number increases through refraction, increasing the Landau damping rate. However, the whistlers are not damped since the background kinetic Alfven wave turbulence creates a plateau by quasilinear diffusion in the solar wind electron distribution at small velocities [Rudakov et al., 2011]. The diffusion coefficient for whistlers in a high beta plasma is determined from mirror force. For a whistler spectrum similar to that of KAW, it is found that for whistler energy density of only ˜10-3 of the kinetic Alfven waves, the quasilinear diffusion rate due to whistlers and KAW are comparable. Thus very small amplitude whistler turbulence can have a significant consequence on the evolution of the solar wind electron distribution function. L. Rudakov, M. Mithaiwala, G. Ganguli, and C. Crabtree. Phys. Plasmas 18, 012307 (2011); http://dx.doi.org/10.1063/1.3532819

Mithaiwala, Manish; Rudakov, Leonid; Ganguli, Gurudas; Crabtree, Chris

2012-10-01

304

Intermittent Heating in Solar Wind and Kinetic Simulations  

NASA Astrophysics Data System (ADS)

Low-density astrophysical plasmas may be described by magnetohydrodynamics at large scales, but require kinetic description at ion scales in order to include dissipative processes that terminate the cascade. Here kinetic plasma simulations and high-resolution spacecraft observations are compared to facilitate the interpretation of signatures of various dissipation mechanisms. Kurtosis of increments indicates that kinetic scale coherent structures are present, with some suggestion of incoherent activity near ion scales. Conditioned proton temperature distributions suggest heating associated with coherent structures. The results reinforce the association of intermittent turbulence, coherent structures, and plasma dissipation.

Wu, P.; Perri, S.; Osman, K.; Wan, M.; Matthaeus, W. H.; Shay, M. A.; Goldstein, M. L.; Karimabadi, H.; Chapman, S.

2013-02-01

305

A Particle-in-cell Method with Adaptive Phase-space Remapping for Kinetic Plasmas  

NASA Astrophysics Data System (ADS)

The numerical solution of the Vlasov-Poisson equation is usually performed by the particle-in-cell (PIC) method. However, it is well-known that, in some cases, the PIC method has difficulty in accurately modeling the phase space distribution function because of numerical noise, an inherent drawback of particle-based methods. In this thesis, a second-order PIC method is presented for computing the dynamics of kinetic plasmas. The method reduces the numerical noise by periodically remapping the distribution function on a hierarchy of locally refined grids in phase space. The new remapping scheme has several features which result in an accurate and efficient method. First, a conservative high-order interpolation function, i.e., a modified B-spline, is chosen for remapping. This interpolation function approximates a quadratic function exactly without solving a matrix system. Second, a local mass redistribution algorithm is provided to enforce the positivity of the distribution function after highorder interpolation. Third, mesh refinement is introduced to reduce the number of small strength particles, mostly located at the tail of the distribution function. Remapping on a phase space grid also provides an opportunity to integrate a collisional model and an associated grid-based solver. A simplified Fokker-Planck equation is used as the collisional model and solved by a second-order finite volume discretization along with a second-order L0 stable implicit time integrator. The collisional model is coupled to the Vlasov-Poisson equation with a second-order operator splitting. A rigorous study of particle methods for the one-dimensional Vlasov-Poisson system has been performed by Cottet and Raviart [1]. We extend the approach to the PIC method for the one-dimensional Vlasov-Poisson equation based on the work in [1].

Wang, Bei

306

The Ulysses solar wind plasma investigation: Description and initial in-ecliptic results  

SciTech Connect

During the in-ecliptic flight of Ulysses from the Earth toward its encounter with Jupiter, the Los Alamos solar wind plasma experiment has performed well. Briefly described, the instrumentation contains two independent electrostatic analyzers, one for ions and one for electrons. Initial analysis of solar wind electron core temperatures obtained between 1.15 and 3.76 AU yields a gradient of T {proportional to} R{sup {minus}0.7} which is flatter than expected for adiabatic expansion of a single-temperature Maxwellian velocity distribution and steeper than that obtained from Mariner-Voyager.

Bame, S.J.; Phillips, J.L.; McComas, D.J.; Gosling, J.T. (Los Alamos National Lab., NM (United States)); Goldstein, B.E. (Jet Propulsion Lab., Pasadena, CA (United States))

1991-01-01

307

Description of the Fokker-Plank code used to model ECRH of the Constance 2 plasma  

SciTech Connect

The time-dependent Fokker-Plank code which is used to model the development of the electron velocity distribution during ECRH of the Constance 2 mirror-confined plasma is described in this report. The ECRH is modeled by the bounce-averaged quasilinear theory derived by Mauel. The effect of collisions are found by taking the appropriate gradients of the Rosenbluth potentials, and the electron distribution is advanced in time by using a modified alternating direction implicit (ADI) technique as explained by Killeen and Marx. The program was written in LISP to be run in the MACSYMA environment of the MACSYMA Consortium's PDP-10 computer.

Mauel, M.E.

1982-01-01

308

Chemical kinetics of radio-frequency driven atmospheric-pressure helium-oxygen plasmas in humid air  

NASA Astrophysics Data System (ADS)

We describe the chemical kinetics of radio-frequency (rf) driven atmospheric-pressure helium-based plasmas in ambient air as determined through a zero-dimensional time-dependent global model. The effects of humid-air admixtures on the plasma-induced chemical reactions and the evolution of species concentrations in the helium-oxygen mixture (He-O2, helium with 5000 ppm admixture of oxygen) are studied for wide air impurity levels of 1-5000 ppm with the relative humidity of 0-100%. Comparisons made with experiments using an rf driven micro-scale atmospheric pressure plasma jet and one-dimensional simulations suggest that the plausible air impurity level in the experiments is not more than hundreds ppm. Effects of the air impurity containing water-humidity on electro-negativity and chemical activity are clarified with particular emphasis on reactive oxygen species.

Murakami, Tomoyuki; Niemi, Kari; Gans, Timo; O'Connell, Deborah; Graham, William

2011-11-01

309

Global 3D kinetic model of cometary rarefied atmosphere toward a description of the coma of Comet 103P/Hartley 2  

NASA Astrophysics Data System (ADS)

The recent images from the Deep Impact spacecraft at Comet 9P/Tempel 1 and from its extended mission EPOXI at Comet 103P/Hartley 2 showed heterogeneous gas release from the nucleus with multiple jets and complex active areas. The coma structure of a comet with such active areas differs from typical models where gas is often produced more uniformly from the surface of the nucleus. While 2D kinetic models are already able to describe relatively complex gas production and can give some critical insights of the physics of the coma, most of them assume cylindrical symmetry around the Sun-Nucleus axis preventing to model small active areas and solar orientations not aligned with the symmetry axis. With constantly increasing computer capacities, 3D kinetic models can now be implemented to give a complete insight from the near nucleus region of the coma where collisions drive its thermodynamics to larger distances where the atmosphere becomes rarefied. We describe a fully 3D kinetic Direct Simulation of Monte Carlo approach to modeling the coma, and a first application to enable progress toward a general tridimensional description of the rarefied atmosphere of Comet Hartley 2 from Fougere et al. (2013) with realistic day-night illumination not only with respect to the EPOXI geometry at closest approach but for other observations. [This work was supported by grant NNX09AB58G from the NASA Planetary Atmosphere program.

Fougere, Nicolas; Combi, M. R.; Tenishev, V.

2013-10-01

310

Low frequency, electrodynamic simulation of kinetic plasmas with the DArwin Direct Implicit Particle-In-Cell (DADIPIC) method  

SciTech Connect

This dissertation describes a new algorithm for simulating low frequency, kinetic phenomena in plasmas. DArwin Direct Implicit Particle-in-Cell (DADIPIC), as its name implies, is a combination of the Darwin and direct implicit methods. One of the difficulties in simulating plasmas lies in the enormous disparity between the fundamental scale lengths of a plasma and the scale lengths of the phenomena of interest. The objective is to create models which can ignore the fundamental constraints without eliminating relevant plasma properties. Over the past twenty years several PIC methods have been investigated for overcoming the constraints on explicit electrodynamic PIC. These models eliminate selected high frequency plasma phenomena while retaining kinetic phenomena at low frequency. This dissertation shows that the combination of Darwin and Direct Implicit allows them to operate better than they have been shown to operate in the past. Through the Darwin method the hyperbolic Maxwell`s equations are reformulated into a set of elliptic equations. Propagating light waves do not exist in the formulation so the Courant constraint on the time step is eliminated. The Direct Implicit method is applied only to the electrostatic field with the result that electrostatic plasma oscillations do not have to be resolved for stability. With the elimination of these constraints spatial and temporal discretization can be much larger than that possible with explicit, electrodynamic PIC. The code functions in a two dimensional Cartesian region and has been implemented with all components of the particle velocities, the E-field, and the B-field. Internal structures, conductors or dielectrics, may be placed in the simulation region, can be set at desired potentials, and driven with specified currents.

Gibbons, M.R.

1995-06-01

311

A Kinetic-fluid Model  

SciTech Connect

A nonlinear kinetic-fluid model for high-beta plasmas with multiple ion species which can be applied to multiscale phenomena is presented. The model embeds important kinetic effects due to finite ion Larmor radius (FLR), wave-particle resonances, magnetic particle trapping, etc. in the framework of simple fluid descriptions. When further restricting to low frequency phenomena with frequencies less than the ion cyclotron frequency the kinetic-fluid model takes a simpler form in which the fluid equations of multiple ion species collapse into single-fluid density and momentum equations and a low frequency generalized Ohm's law. The kinetic effects are introduced via plasma pressure tensors for ions and electrons which are computed from particle distribution functions that are governed by the Vlasov equation or simplified plasma dynamics equations such as the gyrokinetic equation. The ion FLR effects provide a finite parallel electric field, a perpendicular velocity that modifies the ExB drift, and a gyroviscosity tensor, all of which are neglected in the usual one-fluid MHD description. Eigenmode equations are derived which include magnetosphere-ionosphere coupling effects for low frequency waves (e.g., kinetic/inertial Alfven waves and ballooning-mirror instabilities).

First Author = C.Z. Cheng [Princeton Plasma Physics Laboratory, Princeton, NJ 08543 (US); Jay R. Johnson

1998-07-10

312

A Fractional Differential Kinetic Equation and Applications to Modelling Bursts in Turbulent Nonlinear Space Plasmas  

NASA Astrophysics Data System (ADS)

Since the 1960s Mandelbrot has advocated the use of fractals for the description of the non-Euclidean geometry of many aspects of nature. In particular he proposed two kinds of model to capture persistence in time (his Joseph effect, common in hydrology and with fractional Brownian motion as the prototype) and/or prone to heavy tailed jumps (the Noah effect, typical of economic indices, for which he proposed Lévy flights as an exemplar). Both effects are now well demonstrated in space plasmas, notably in the turbulent solar wind. Models have, however, typically emphasised one of the Noah and Joseph parameters (the Lévy exponent ? and the temporal exponent ?) at the other's expense. I will describe recent work in which we studied a simple self-affine stable model-linear fractional stable motion, LFSM, which unifies both effects and present a recently-derived diffusion equation for LFSM. This replaces the second order spatial derivative in the equation of fBm with a fractional derivative of order ?, but retains a diffusion coefficient with a power law time dependence rather than a fractional derivative in time. I will also show work in progress using an LFSM model and simple analytic scaling arguments to study the problem of the area between an LFSM curve and a threshold. This problem relates to the burst size measure introduced by Takalo and Consolini into solar-terrestrial physics and further studied by Freeman et al [PRE, 2000] on solar wind Poynting flux near L1. We test how expressions derived by other authors generalise to the non-Gaussian, constant threshold problem. Ongoing work on extension of these LFSM results to multifractals will also be discussed.

Watkins, N. W.; Rosenberg, S.; Sanchez, R.; Chapman, S. C.; Credgington, D.

2008-12-01

313

Plasma Kinetics and Urinary Excretion of the Flavanones Naringenin and Hesperetin in Humans after Ingestion of Orange Juice and Grapefruit Juice1  

Microsoft Academic Search

The flavanones naringenin and hesperetin exhibit estrogenic, anticarcinogenic and antioxidative properties. Orange juice and grapefruit juice contain high amounts of these compounds, and therefore their intake from the diet can be relatively high. No data are available regarding plasma concentrations or plasma kinetics of flavanones. The objectives of this study were to develop methods allowing the analysis of naringenin and

Iris Erlund; Esa Meririnne; Georg Alfthan; Antti Aro

314

Relationships between changes in plasma lipid transfer proteins and apolipoprotein B-100 kinetics during fenofibrate treatment in the metabolic syndrome.  

PubMed

The aim of the present study was to investigate the association between changes in apoB (apolipoprotein B-100) kinetics and plasma PLTP (phospholipid transfer protein) and CETP (cholesteryl ester transfer protein) activities in men with MetS (the metabolic syndrome) treated with fenofibrate. Eleven men with MetS underwent a double-blind cross-over treatment with fenofibrate (200 mg/day) or placebo for 5 weeks. Compared with placebo, fenofibrate significantly increased the FCRs (fractional catabolic rates) of apoB in VLDL (very-low-density lipoprotein), IDL (intermediate-density lipoprotein) and LDL (low-density lipoprotein) (all P<0.01), with no significant reduction (-8%; P=0.131) in VLDL-apoB PR (production rate), but an almost significant increase (+15%, P=0.061) in LDL-apoB PR. Fenofibrate significantly lowered plasma TG [triacylglycerol (triglyceride); P<0.001], the VLDL-TG/apoB ratio (P=0.003) and CETP activity (P=0.004), but increased plasma HDL (high-density lipoprotein)-cholesterol concentration (P<0.001) and PLTP activity (P=0.03). The increase in PLTP activity was positively associated with the increase in both LDL-apoB FCR (r=0.641, P=0.034) and PR (r=0.625, P=0.040), and this was independent of the fall in plasma CETP activity and lathosterol level. The decrease in CETP activity was positively associated with the decrease in VLDL-apoB PR (r=0.615, P=0.044), but this association was not robust and not independent of changes in PLTP activity and lathosterol levels. Hence, in MetS, the effects of fenofibrate on plasma lipid transfer protein activities, especially PLTP activity, may partially explain the associated changes in apoB kinetics. PMID:16700661

Watts, Gerald F; Ji, Juying; Chan, Dick C; Ooi, Esther M M; Johnson, Anthony G; Rye, Kerry-Anne; Barrett, P Hugh R

2006-09-01

315

The kinetics of a bounded collisionless plasma in a gravitational radiation field  

Microsoft Academic Search

The possibility of collective mode generation in a semibounded collisionless plasma in a plasma layer due to the effect of an incident plane gravitational wave is discussed. The particle distribution function, electric current, and electric and magnetic field intensities are calculated for a plasma with plane boundaries, parallel and perpendicular to the gravitational wave front, in the case of mirror

A. B. Balakin

1986-01-01

316

The Effects of Kinetic Alfven and Whistler Wave Turbulence and the Evolution of Electron Distribution in Solar Wind Plasma  

NASA Astrophysics Data System (ADS)

The high beta solar wind plasma turbulence is dominated by the kinetic Alfven waves (KAW) [1]. Though the measured high-energy tail on the electron distribution function can be a signature of the presence of whistler waves (WW) as well [2]. In Maxwellian plasma both KAW and WW are Landau damped at high beta, and only for the specific case of WW with kperp=0 is there no Landau damping. Due to the inhomogeneous solar wind plasma these parallel propagating WW should quickly develop large perpendicular wavenumbers kperp>k|| . However, as we have shown recently using measured KAW spectra, Landau damping establishes a plateau in the parallel electron distribution function and damping is strongly diminished [3]. The theory of WW in high beta inhomogeneous plasma will be presented and the impact of the electron cyclotron resonance with WW on the evolution of the electrons high energy tail will be discussed. [1] O. Alexandrova et. al., PRL (2009) ; F. Sahraoui et. al., PRL (2010). [2] T. Nieves-Chinchilla and A. F. Vinas, JGR (2008). [3] L. Rudakov et. al., Phys. Plasma, 18, 012307 (2011).

Mithaiwala, M.; Rudakov, L.; Ganguli, G.; Crabtree, C. E.

2011-12-01

317

The Effects of Kinetic Alfven and Whistler Wave Turbulence and the Evolution of Electron Distribution in Solar Wind Plasma  

NASA Astrophysics Data System (ADS)

The high beta solar wind plasma turbulence is dominated by the kinetic Alfven waves (KAW) [1]. Though the measured high-energy tail on the electron distribution function can be a signature of the presence of whistler waves (WW) as well [2]. In Maxwellian plasma both KAW and WW are Landau damped at high beta, and only for the specific case of WW with k=0 is there no Landau damping. Due to the inhomogeneous solar wind plasma these parallel propagating WW should quickly develop large perpendicular wavenumbers >. However, as we have shown recently using measured KAW spectra, Landau damping establishes a plateau in the parallel electron distribution function and damping is strongly diminished [3]. The theory of WW in high beta inhomogeneous plasma will be presented and the impact of the electron cyclotron resonance with WW on the evolution of the electrons high energy tail will be discussed. Supported by ONR. [0pt] [1] O. Alexandrova et. al., PRL (2009) ; F. Sahraoui et. al., PRL (2010). [0pt] [2] T. Nieves-Chinchilla and A. F. Vin& tilde;as, JGR (2008). [0pt] [3] L. Rudakov et. al., Phys. Plasma, 18, 012307 (2011).

Mithaiwala, Manish; Rudakov, Leonid; Ganguli, Gurudas; Crabtree, Chris

2011-11-01

318

Kinetic effects in the conversion of fast waves in pre-heated, low aspect ratio tokamak plasmas  

NASA Astrophysics Data System (ADS)

Kinetic effects in the conversion of fast waves to Alfvèn waves and their subsequent deposition in low aspect ratio (spherical) tokamaks (LARTs) have been investigated theoretically. More specifically, we have considered the consequences of incorporation of kinetic effects in the electron parallel (to the ambient magnetic field) dynamics derived by following the drift-tearing mode analysis of Chen et al (Chen L, Rutherford P H and Tang W M 1977 Phys. Rev. Lett. 39 460), and particle-conserving Krook collision operator for the passing electrons involved (Mett R R and Mahajan S M 1992 Phys. Fluids B 4 2885). The perpendicular plasma dynamics is described by a quite general resistive two-fluid (2F) model based dielectric tensor-operator (Cuperman S, Bruma C and Komoshvili K 2002 Solution of the resistive 2F wave equations for Alfvènic modes in spherical tokamak plasmas J. Plasma Phys. accepted for publication). The full-wave electromagnetic equations, formulated in terms of the vector and scalar potentials, have been solved by the aid of an advanced finite elements numerical code (Sewell G 1993 Adv. Eng. Software 17 105). Detailed solutions of the full-wave equations are obtained and compared with those corresponding to a pure resistive 2F model, this, for the illustrative pre-heated START-type device (Sykes 1994). Our results quantitatively confirm the general theory of the conversion of fast waves with subsequent power dissipation for the conditions of spherical tokamaks thus providing the required auxilliary energy source for the succesful operation of LARTs. Moreover, these results indicate the absolute necessity of using a full model for the parallel electron dynamics, i.e. including both kinetic and collisional effects.

Kommoshvili, K.; Cuperman, S.; Bruma, C.

2003-03-01

319

Sacrificial bonds and hidden length in biomaterials: a kinetic constitutive description of strength and toughness in bone.  

PubMed

Sacrificial bonds and hidden length in structural molecules account for the greatly increased fracture toughness of biological materials compared to synthetic materials without such structural features by providing a molecular-scale mechanism for energy dissipation. One example is in the polymeric glue connection between collagen fibrils in animal bone. In this paper we propose a simple kinetic model that describes the breakage of sacrificial bonds and the release of hidden length, based on Bell's theory. We postulate a master equation governing the rates of bond breakage and formation. This enables us to predict the mechanical behavior of a quasi-one-dimensional ensemble of polymers at different stretching rates. We find that both the rupture peak heights and maximum stretching distance increase with the stretching rate. In addition, our theory naturally permits the possibility of self-healing in such biological structures. PMID:23944488

Lieou, Charles K C; Elbanna, Ahmed E; Carlson, Jean M

2013-07-03

320

Indium kinetics during the plasma-assisted molecular beam epitaxy of semipolar (11-22) InGaN layers  

SciTech Connect

We report on the growth kinetics of semipolar (11-22) InGaN layers by plasma-assisted molecular beam epitaxy. Similarly to (0001)-oriented InGaN, optimum growth conditions for this crystallographic orientation correspond to the stabilization of two atomic layers of In on the growing InGaN surface, and the limits of this growth window in terms of substrate temperature and In flux lie at same values for both polar and semipolar material. However, in semipolar samples, the incorporation of In is inhibited, even for growth temperatures within the Ga-limited regime of polar InGaN growth.

Das, A.; Kotsar, Y.; Kandaswamy, P. K.; Gayral, B.; Monroy, E. [CEA/CNRS group 'Nanophysique et semiconducteurs', INAC/SP2M/NPSC, CEA-Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9 (France); Magalhaes, S.; Lorenz, K.; Alves, E. [Unidade de Fisica e Aceleradores, Instituto Tecnologico e Nuclear, Estrada Nacional 10, P-2686-953 Sacavem (Portugal); Ruterana, P. [CIMAP, UMR 6252 CNRS-ENSICAEN, 6 Boulevard du Marechal Juin, 14050 Caen Cedex (France)

2010-05-03

321

High kinetic energy plasma jet generation and its injection into the Globus-M spherical tokamak  

NASA Astrophysics Data System (ADS)

Progress in the theoretical and experimental development of the plasma jet source and injection of hydrogen plasma and neutral gas jets into the Globus-M spherical tokamak is discussed. An experimental test bed is described for investigation of intense plasma jets that are generated by a double-stage plasma gun consisting of an intense source for neutral gas production and a conventional pulsed coaxial accelerator. A procedure for optimizing the accelerator parameters so as to achieve the maximum possible flow velocity with a limited discharge current and a reasonable length of the coaxial electrodes is presented. The calculations are compared with experiment. Plasma jet parameters, among them pressure distribution across the jet, flow velocity, plasma density, etc, were measured. Plasma jets with densities of up to 1022 m-3, total numbers of accelerated particles (1-5) × 1019, and flow velocities of 50-100 km s-1 were successfully injected into the plasma column of the Globus-M tokamak. Interferometric and Thomson scattering measurements confirmed deep jet penetration and a fast density rise (<0.5 ms) at all spatial points up to a radius rap 0.3a. The plasma particle inventory increase by ~50% (from 0.65 × 1019 to 1 × 1019) did not result in plasma degradation.

Voronin, A. V.; Gusev, V. K.; Petrov, Yu. V.; Sakharov, N. V.; Abramova, K. B.; Sklyarova, E. M.; Tolstyakov, S. Yu.

2005-09-01

322

Kinetic description of intense nonneutral beam propagation through a periodic solenoidal focusing field based on the nonlinear Vlasov-Maxwell equations  

SciTech Connect

A kinetic description of intense nonneutral beam propagation through a periodic solenoidal focusing field B{sup sol}({rvec x}) is developed. The analysis is carried out for a thin beam with characteristic beam radius r{sub b} {much_lt} S, and directed axial momentum {gamma}{sub b}m{beta}{sub b}c (in the z-direction) large compared with the transverse momentum and axial momentum spread of the beam particles. Making use of the nonlinear Vlasov-Maxwell equations for general distribution function f{sub b}({rvec x},{rvec p},t) and self-consistent electrostatic field consistent with the thin-beam approximation, the kinetic model is used to investigate detailed beam equilibrium properties for a variety of distribution functions. Examples are presented both for the case of a uniform solenoidal focusing field B{sub z}(z) = B{sub 0} = const. and for the case of a periodic solenoidal focusing field B{sub z}(z + S) = B{sub z}(z). The nonlinear Vlasov-Maxwell equations are simplified in the thin-beam approximation, and an alternative Hamiltonian formulation is developed that is particularly well-suited to intense beam propagation in periodic focusing systems. Based on the present analysis, the Vlasov-Maxwell description of intense nonneutral beam propagation through a periodic solenoidal focusing field {rvec B}{sup sol}({rvec x}) is found to be remarkably tractable and rich in physics content. The Vlasov-Maxwell formalism developed here can be extended in a straightforward manner to investigate detailed stability behavior for perturbations about specific choices of beam equilibria.

Davidson, R.C. [Princeton Univ., NJ (United States). Princeton Plasma Physics Lab.; Chen, C. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Plasma Science and Fusion Center

1997-08-01

323

Kinetic instabilities that limit ? in the edge of a tokamak plasma: a picture of an H-mode pedestal.  

PubMed

Plasma equilibria reconstructed from the Mega-Amp Spherical Tokamak have sufficient resolution to capture plasma evolution during the short period between edge-localized modes (ELMs). Immediately after the ELM, steep gradients in pressure, P, and density, n(e), form pedestals close to the separatrix, and they then expand into the core. Local gyrokinetic analysis over the ELM cycle reveals the dominant microinstabilities at perpendicular wavelengths of the order of the ion Larmor radius. These are kinetic ballooning modes in the pedestal and microtearing modes in the core close to the pedestal top. The evolving growth rate spectra, supported by gyrokinetic analysis using artificial local equilibrium scans, suggest a new physical picture for the formation and arrest of this pedestal. PMID:22540707

Dickinson, D; Roach, C M; Saarelma, S; Scannell, R; Kirk, A; Wilson, H R

2012-03-26

324

Kinetic Instabilities that Limit ? in the Edge of a Tokamak Plasma: A Picture of an H-Mode Pedestal  

NASA Astrophysics Data System (ADS)

Plasma equilibria reconstructed from the Mega-Amp Spherical Tokamak have sufficient resolution to capture plasma evolution during the short period between edge-localized modes (ELMs). Immediately after the ELM, steep gradients in pressure, P, and density, ne, form pedestals close to the separatrix, and they then expand into the core. Local gyrokinetic analysis over the ELM cycle reveals the dominant microinstabilities at perpendicular wavelengths of the order of the ion Larmor radius. These are kinetic ballooning modes in the pedestal and microtearing modes in the core close to the pedestal top. The evolving growth rate spectra, supported by gyrokinetic analysis using artificial local equilibrium scans, suggest a new physical picture for the formation and arrest of this pedestal.

Dickinson, D.; Roach, C. M.; Saarelma, S.; Scannell, R.; Kirk, A.; Wilson, H. R.

2012-03-01

325

Investigation of chemical kinetics and energy transfer in a pulsed microwave H2\\/CH4 plasma  

Microsoft Academic Search

We present a modelling study of pulsed H2\\/CH4 microwave plasmas obtained under moderate pressure discharge conditions in a tubular quartz reactor. The transport in the reactor was described using a Nusselt model for a radially quasi-homogeneous plasma. The thermal behaviour of the plasma was modelled by distinguishing a single heavy species energy mode and the electron translation mode. The chemistry

K. Hassouni; X. Duten; A. Rousseau; A. Gicquel

2001-01-01

326

Reduced fluid-kinetic equations for low-frequency dynamics, magnetic reconnection, and electron heating in low-beta plasmas  

NASA Astrophysics Data System (ADS)

A minimal model for magnetic reconnection and, generally, low-frequency dynamics in low-beta plasmas is proposed. The model combines analytical and computational simplicity with physical realizability: it is a rigorous limit of gyrokinetics for plasma beta of order the electron-ion mass ratio. The model contains collisions and can be used both in the collisional and collisionless reconnection regimes. It includes gyrokinetic ions (not assumed cold) and allows for the topological rearrangement of the magnetic field lines by either resistivity or electron inertia, whichever predominates. The two-fluid dynamics are coupled to electron kinetics--electrons are not assumed isothermal and are described by a reduced drift-kinetic equation. The model, therefore allows for irreversibility and conversion of magnetic energy into electron heat via parallel phase mixing in velocity space. An analysis of the exchanges between various forms of free energy and its conversion into electron heat is provided. It is shown how all relevant linear waves and regimes of the tearing instability (collisionless, semicollisional, and fully resistive) are recovered in various limits of our model. An efficient way to simulate our equations numerically is proposed, via the Hermite representation of the velocity space. It is shown that small scales in velocity space will form, giving rise to a shallow Hermite-space spectrum, whence it is inferred that, for steady-state or sufficiently slow dynamics, the electron heating rate will remain finite in the limit of vanishing collisionality.

Zocco, Alessandro; Schekochihin, Alexander A.

2011-10-01

327

Funktsii nelinejnogo otklika plazmenno-molekulyarnoj sredy. (Nonlinear response functions for plasma-molecular medium).  

National Technical Information Service (NTIS)

Within the framework of the kinetical description the nonlinear responce functions for the combined plasma-molecular medium are calculated. The general expressions for the nonlinear susceptibility of the system under consideration are obtained in all orde...

G. F. Goryunova I. P. Yakimenko

1987-01-01

328

Kinetic Description of Intense Beam Propagation Through a Periodic Focusing Field for Uniform Phase-Space Density  

SciTech Connect

The Vlasov-Maxwell equations are used to investigate the nonlinear evolution of an intense sheet beam with distribution function f{sub b}(x,x{prime},s) propagating through a periodic focusing lattice k{sub x}(s+S) = k{sub x}(s), where S = const is the lattice period. The analysis considers the special class of distribution functions with uniform phase-space density f{sub b}(x,x{prime},s) = A = const inside of the simply connected boundary curves, x{prime}{sub +}(x,s) and x{prime}{sub -}(x,s), in the two-dimensional phase space (x,x{prime}). Coupled nonlinear equations are derived describing the self-consistent evolution of the boundary curves, x{prime}{sub +}(x,s) and x{prime}{sub -}(x,s), and the self-field potential {psi}(x,s) = e{sub b}{phi}(x,s)/{gamma}{sub b}m{sub b}{beta}{sub g}{sup 2}c{sup 2}. The resulting model is shown to be exactly equivalent to a (truncated) warm-fluid description with zero heat flow and triple-adiabatic equation-of-state with scalar pressure P{sub b}(x,s) = const x [n{sub b}(x,s)]. Such a fluid model is amenable to direct analysis by transforming to Lagrangian variables following the motion of a fluid element. Specific examples of periodically focused beam equilibria are presented, ranging from a finite-emittance beam in which the boundary curves in phase space (x,x{prime}) correspond to a pulsating parallelogram, to a cold beam in which the number density of beam particles, n{sub b}(x,s), exhibits large-amplitude periodic oscillations. For the case of a sheet beam with uniform phase-space density, the present analysis clearly demonstrates the existence of periodically focused beam equilibria without the undesirable feature of an inverted population in phase space that is characteristic of the Kapchinskij-Vladimirskij beam distribution.

Ronald C. Davidson; Hong Qin; Stephan I. Tzenov; Edward A. Startsev

2003-02-26

329

Hybrid Kinetic Model of Asymmetric Thin Current Sheets with Sheared Flows in a Collisionless Plasma.  

National Technical Information Service (NTIS)

A new model of equilibrium current sheets in a collisionless plasma incorporating ion flows that are asymmetric and sheared across the current sheet is developed. Ions are treated as single particles and electrons as a massless fluid. The resulting curren...

A. Szabo D. E. Larson J. Chen R. A. Sabtoro

2010-01-01

330

Kinetics of Neutrophil-Releasing Activity of Post-Leukopheresis Plasma.  

National Technical Information Service (NTIS)

The studies carried out during the first year of this contract were concerned principally with determining the optimal dosage of plasma from rats which had undergone filtration leukopheresis (PPP) to stimulate a granulocytosis in other rats to be used as ...

A. J. Roy

1978-01-01

331

Kinetics of Plasma Membrane Electron Transport in a Pulmonary Endothelial Cell-Column  

Microsoft Academic Search

Thiazine dyes such as toluidine blue O (TBO) are reduced at the luminal endothelial surface. The purpose of this study was to determine the rate of this reaction in endothelial cells in culture. A multiple indicator dilution method was used to measure the reaction kinetics during transient passage of a TBO-containing bolus through a chromatographic column filled with bovine pulmonary

L. E. Olson; M. P. Merker; R. D. Bongard; B. M. Brantmeier; S. H. Audi; J. H. Linehan; C. A. Dawson

1998-01-01

332

Chemical kinetics simulation for atmospheric pressure air plasmas in a streamer regime  

Microsoft Academic Search

We present a theoretical analysis of air discharges at high pressure which operates in a streamer regime. The aim is to provide a simplified framework to study the chemical kinetics in the discharge gas phase. We have tried to model the characteristics of actually existing devices, such as dc and ac discharges in sharp point-plane, point to point, or coaxial

R. Barni; P. Esena; C. Riccardi

2005-01-01

333

Plasma kinetics of carbamazepine and its epoxide metabolite in man after single and multiple doses  

Microsoft Academic Search

Carbamazepine (Tegretol®) was administered orally to four patients as a single dose, and one week later three times daily for 15–21 days. The plasma half-lives of the drug were shorter in all patients after multiple doses (20.9±5.0 hours) than after the initial single dose (35.6±15.3 hours). During multiple doses the plasma concentrations of the metabolite carbamazepine-10,11-epoxide followed those of the

M. Eichelbaum; K. Ekbom; L. Bertilsson; V. A. Ringberger; A. Rane

1975-01-01

334

A simplified chemical kinetic model for slightly ionized, atmospheric pressure nitrogen plasmas  

Microsoft Academic Search

Nitrogen plasmas at atmospheric pressure produced by 2.45 GHz microwaves at a power density of approximately 10 MW m-3 have a degree of ionization less than about 10-7. Nevertheless they have interesting and potentially important effects on polymer and metal surfaces exposed to them. An experimental programme is underway to identify the active species in the plasma and its afterglow.

J. Hugill; T. Saktioto

2001-01-01

335

Plasma kinetics of apoC-III and apoE in normolipidemic and hypertriglyceridemic subjects  

Microsoft Academic Search

Apolipoprotein (apo) C-III and apoE play a cen- tral role in controlling the plasma metabolism of triglyceride- rich lipoproteins (TRL). We have investigated the plasma ki- netics of total, very low density lipoprotein (VLDL) and high density lipoprotein (HDL) apoC-III and apoE in nor- molipidemic (NL) (n 5 5), hypertriglyceridemic (HTG, n 5 5), and Type III hyperlipoproteinemic (n 5

Rami Batal; Michel Tremblay; P. Hugh; R. Barrett; Hélène Jacques; Alexandre Fredenrich; Orval Mamer; Jean Davignon; Jeffrey S. Cohn

336

Gyrokinetic turbulence simulations of high-beta tokamak and helical plasmas with full-kinetic and hybrid models  

NASA Astrophysics Data System (ADS)

Turbulent transport in high-beta toroidal plasmas is investigated by means of an electromagnetic gyrokinetic model and a newly developed electromagnetic hybrid model consisting of the gyrokinetic equation for ions and drift-Landau-fluid equations for electrons. Full gyrokinetic simulation results for Cyclone base case tokamak and for Large Helical Device (LHD) plasmas are quickly and accurately reproduced by the hybrid simulation. In the kinetic ballooning mode (KBM)-driven turbulence the ion heat and particle fluxes are mainly caused by electrostatic perturbation, and the contribution of magnetic perturbation is small and negative. The electron heat flux is caused by both electrostatic and magnetic perturbations. The numerical solutions satisfy the entropy balance equation, and the entropy is transferred from ions to electrons through electrostatic and magnetic perturbations. An analysis based on the entropy balance equation shows that the zonal structure is produced by magnetic nonlinearity corresponding to the Maxwell stress in the fluid limit but is weakened by the electrostatic one related to the Reynolds stress. A linear analysis on the standard configuration of LHD plasmas shows the suppression of the ion temperature gradient mode by finite-beta effects and the destabilization of KBM at high beta.

Ishizawa, A.; Maeyama, S.; Watanabe, T.-H.; Sugama, H.; Nakajima, N.

2013-05-01

337

Modeling of population kinetics of plasmas that are not in local thermodynamic equilibrium, using a versatile collisional-radiative model based on analytical rates.  

PubMed

We discuss the modeling of population kinetics of nonequilibrium steady-state plasmas using a collisional-radiative model and code based on analytical rates (ABAKO). ABAKO can be applied to low-to-high Z ions for a wide range of laboratory plasma conditions: coronal, local thermodynamic equilibrium or nonlocal thermodynamic equilibrium, and optically thin or thick plasmas. ABAKO combines a set of analytical approximations to atomic rates, which yield substantial savings in computer running time, still comparing well with more elaborate codes and experimental data. A simple approximation to calculate the electron capture cross section in terms of the collisional excitation cross section has been adapted to work in a detailed-configuration-accounting approach, thus allowing autoionizing states to be explicitly included in the kinetics in a fast and efficient way. Radiation transport effects in the atomic kinetics due to line trapping in the plasma are taken into account via geometry-dependent escape factors. Since the kinetics problem often involves very large sparse matrices, an iterative method is used to perform the matrix inversion. In order to illustrate the capabilities of the model, we present a number of results which show that the ABAKO compares well with customized models and simulations of ion population distribution. The utility of ABAKO for plasma spectroscopic applications is also outlined. PMID:20365078

Florido, R; Rodríguez, R; Gil, J M; Rubiano, J G; Martel, P; Mínguez, E; Mancini, R C

2009-11-04

338

Kinetic Self-Organization of Microinstabilities in Astrophysical and in Laboratory Plasmas  

NASA Astrophysics Data System (ADS)

Microinstabilities can be considered as effective collisions. The small scale electromagnetic fluctuations due to microinstabilties can be considered as collisions on the particles, leading to a similar point-like and instantaneous-like change in the particle momentum. This paradigm, the anomalous transport paradigm, requires us to derive theories that can predict the correct transport parameters (particularly the anomalous viscosity and anomalous resistivity) from the properties of the microinstabilties. Our recent work [1-3] has shown that another possible effect of microinstabilties is to lead to a direct macroscopic change in the equilibrium by affecting the plasma flow, temperature anisotropy and current profile on a macroscopic level. Our previous work has focused on space and astrophysical systems. But similar effects can be considered for experimental plasmas. A particularly intriguing possible analogy is with zonal flows and ``angular momentum generation'' believed to be happening in accretion disks in astrophysical systems [4] and with the ``spontaneous toroidal rotation'' of axisymmetric plasmas in fusion devices such as Jet and Alcator C-Mod [5]. [1] G. Lapenta, J.U. Brackbill, W.S. Daughton, Phys. Plasmas, 10, 1577 (2003). [2] W. Daughton, G. Lapenta, P. Ricci, Phys. Rev. Lett., 93, 105004, 2004 [3] P. Ricci, J.U. Brackbill, W.S. Daughton, G. Lapenta, Phys. Plasmas, 11, 4102, 2004. [4] B. Coppi 2002 Nucl. Fusion 42 1-4 [5] E. S. Marmar, et al., Fusion Energy 2002 (IAEA, Vienna) Paper OV/4-1

Lapenta, Giovanni

2006-04-01

339

Studies on the formation of large amplitude kinetic Alfven wave solitons and double layers in plasmas  

SciTech Connect

A two fluid model has been employed to study the oblique propagation of solitary kinetic Alfven waves. Formation of solitary waves and double layers is observed. Amplitude, width (in the case of solitons), and thickness (in the case of double layers) of the nonlinear structures are studied in some detail. Wider solitary structures are found to exist for oblique propagation nearer to the magnetic field direction.

Devi, N.; Gogoi, R.; Das, G. C.; Roychoudhury, R. [Department of Mathematics, Cotton College, Guwahati-781001, Assam (India); Mathematical Sciences Division, Institute of Advanced Study in Science and Technology, Paschim Boragaon, Guwahati-781035, Assam (India); Physics and Applied Mathematical Unit, Indian Statistical Institute, Kolkata 700108 (India)

2007-01-15

340

Electron Kinetics and Self-Consistent Modeling of High Current Positive Column Plasmas  

NASA Astrophysics Data System (ADS)

We present results of a recently developed self-consistent plasma model for high-current positive column plasmas. The model solves the Boltzmann equation in the two-term approximation accounting for the radial plasma nonuniformity. Coulomb collisions are included by using a well-known Fokker-Planck operator. Our Boltzmann solver is based on a control volume approach. The resulting system of equations is solved using a relaxation method. The ambipolar space charge potential is determined from the Poisson equation. For a given electron density as input parameter, we self-consistently determine the axial electric field strength such that the ionization-wall loss balance for the column is fulfilled. This work was supported in part by NSF (grant ECS-9713137), DOE (grant ER54554), the University of Minnesota Supercomputing Institute, and General Electric.

Kortshagen, Uwe; Michael, J. Darryl; Ingold, John H.

2000-10-01

341

REVIEW ARTICLE: On simplifying approaches to the solution of the Boltzmann equation in spatially inhomogeneous plasmas  

Microsoft Academic Search

With the continuing progress of plasma modelling in recent years the desire arose to develop simplified approaches to the kinetic description of the electron component in weakly ionized plasmas. Methods which are based on the direct solution of the Boltzmann equation in some limiting situations, namely the `nonlocal' approximation in a weakly collisional plasma and the `local' approximation in a

U. Kortshagen; C. Busch; L. D. Tsendin

1996-01-01

342

Generation of Plasma Perturbations Under Collisionless Interaction of SUPER-ALFVÉNIC Flows  

NASA Astrophysics Data System (ADS)

Generation of plasma perturbations because of collisionless super-Alfvénic dense plasma clouds expanding through and decelerating in an ambient plasma background is studied. Using an universal hybrid kinetic-hydrodynamical description, the calculations are made for a 2D and 3D expansion of a spherical cloud into an initially uniform background with uniform magnetic field.

Dudnikova, G.; Liseykina, T.; Vshivkov, K.

2007-08-01

343

Kinetic effect of high energy ions on the temperature profile in the boundary plasma region  

NASA Astrophysics Data System (ADS)

Importance of ion dynamics in the boundary region has been discussed with experimental results of ion temperature (Ti) measurements in linear plasma devices and its analytical model. Radial profiles of Ti have been measured by using an ion sensitive probe in the linear devices CTP-HC and NAGDIS-II. The experiments indicate that Ti is growing radially. Analytical ion-mean-energy profiles based on the ion Larmor motion are qualitatively consistent with the experimental Ti profiles. These results clarify that the higher energy ions exist in the outside region of plasma flux tube.

Ezumi, N.; Hayashi, Y.; Todoroki, K.; Okazaki, K.; Tanaka, H.; Masuzaki, S.; Ohno, N.

2013-07-01

344

Kinetic analysis of the ion temperature gradient modes in toroidally rotating plasmas  

Microsoft Academic Search

With the two time scale feature revealed, an analytical method is developed to solve the combined eigenvalue and initial value problem describing the ion temperature gradient (ITG) modes in the toroidally rotating plasmas. With full gyrokinetics and toroidal geometry effects being taken into account in an ordering consistent manner, dispersion relations are obtained for ITG modes both of toroidal and

L.-J. Zheng; M. Tessarotto

1996-01-01

345

Kinetic Models of the Cyclotron Resonant Wave-Particle Interaction in Heliospheric Plasmas  

Microsoft Academic Search

The resonant cyclotron interaction between gyrating ions and MHD waves is fundamental to understanding the behavior of many plasma phenomena in the heliosphere. Close to the Sun, the heating and acceleration of the solar wind in the corona is likely caused by the resonant dissipation of ion cyclotron waves. In the outer heliosphere, the ionization of inflowing interstellar neutrals creates

Philip Isenberg

2006-01-01

346

Kinetic modelling for an atmospheric pressure argon plasma jet in humid air  

NASA Astrophysics Data System (ADS)

A zero-dimensional, semi-empirical model is used to describe the plasma chemistry in an argon plasma jet flowing into humid air, mimicking the experimental conditions of a setup from the Eindhoven University of Technology. The model provides species density profiles as a function of the position in the plasma jet device and effluent. A reaction chemistry set for an argon/humid air mixture is developed, which considers 84 different species and 1880 reactions. Additionally, we present a reduced chemistry set, useful for higher level computational models. Calculated species density profiles along the plasma jet are shown and the chemical pathways are explained in detail. It is demonstrated that chemically reactive H, N, O and OH radicals are formed in large quantities after the nozzle exit and H2, O2(1?g), O3, H2O2, NO2, N2O, HNO2 and HNO3 are predominantly formed as ‘long living’ species. The simulations show that water clustering of positive ions is very important under these conditions. The influence of vibrational excitation on the calculated electron temperature is studied. Finally, the effect of varying gas temperature, flow speed, power density and air humidity on the chemistry is investigated.

Van Gaens, W.; Bogaerts, A.

2013-07-01

347

Effects of acute bovine trypanosomosis ( Trypanosoma vivax) on plasma kinetics of intravenously administered lactose  

Microsoft Academic Search

Four calves infected with Trypanosoma vivax and four uninfected control calves were each injected intravenously with repeated doses of 0.5 g lactose kg?1 body weight, thrice daily at intervals of 4 h. Plasma samples were collected at specified time intervals and analysed for lactose. Pharmacokinetic parameters were calculated from the data. T. vivax infection delayed excretion of lactose from the

I. A Umar; J. J Omage; A Shugaba; I. O Igbokwe; N. D. G Ibrahim; Kwem B Kadima; D. A Ameh; Helen O Kwanashie; R. I. S Agbede; D. I Saror; K. A. N Esievo

1998-01-01

348

2-D analytic model for inductively coupled plasma sources. I. Electromagnetic model and kinetic analysis  

Microsoft Academic Search

Inductively coupled plasma sources (ICPS) have recently received increasing interest for semiconductor etching and deposition. A 2-D (r, z) electromagnetic (EM) model of ICPS is developed in terms of the mode analysis (MA) technique. Based upon the eigenmode expansion, a closed-form of the vector and scalar potentials of the EM fields is obtained, which provides exact and fast computing for

Fa Dai; Chwan-Hwa John Wu

1995-01-01

349

Comparison of initial value and eigenvalue codes for kinetic toroidal plasma instabilities  

Microsoft Academic Search

In plasma physics, linear instability calculations can be implemented either as initial value calculations or as eigenvalue calculations. Here, comparisons between comprehensive linear gyrokinetic calculations employing the ballooning formalism for high-n (toroidal mode number) toroidal instabilities are described. One code implements an initial value calculation on a grid using a Lorentz collision operator and the other implements an eigenvalue calculation

Mike Kotschenreuther; G. Rewoldt; W. M. Tang

1995-01-01

350

MULTICOMPARTMENT KINETIC MODEL FOR LEAD. PART 3. LEAD IN BLOOD PLASMA AND ERYTHROCYTES  

EPA Science Inventory

Multicompartment models have been fitted to experimental data on plasma lead and blood lead concentrations of subjects studied by de Silva (1981, Brit. J. Industr. Med. 38, 209-217) and one subject studied by Manton and Malloy (1983, Brit. J. Industr. Med., 40, 51-57). Nonlinear ...

351

Cluster observations of kinetic structures and electron acceleration within a dynamic plasma bubble  

NASA Astrophysics Data System (ADS)

Fast plasma flows are believed to play important roles in transporting mass, momentum and energy in the magnetotail during active periods, such as the magnetospheric substorms. In this paper, we present Cluster observations of a plasma-depleted flux tube, i.e., a plasma bubble associated with fast plasma flow before the onset of a substorm in the near-Earth tail around X= -18RE. The bubble is bounded by both sharp leading (?bz/?x<0) and trailing (?bz/?x>0) edges. The two edges are thin current layers (~ ion inertial length) that carry not only intense perpendicular current but also field-aligned current. The leading edge is a dipolarization front (DF) within a slow plasma flow, while the trailing edge is embedded in a super-Alfvénic convective ion jet. The electron jet speed exceeds the ion flow speed thus producing a large tangential current at the trailing edge. The electron drift is primarily given by the E×B drift. Interestingly, the trailing edge moves faster than the leading edge, which causes shrinking of the bubble and local flux pileup inside the bubble. This resulted in a further intensification of Bz, or a secondary dipolarization. Both the leading and trailing edges are tangential discontinuities that confine the electrons inside the bubble. Strong electron acceleration occurred corresponding to the secondary dipolarization, with perpendicular fluxes dominating the field-aligned fluxes. We suggest that betatron acceleration is responsible for the electron energization. Whistler waves and lower hybrid drift waves were identified inside the bubble. Their generation mechanisms and potential roles in electron dynamics are discussed.

Zhou, Meng; Deng, Xiaohua; Ashour-Abdalla, Maha; Walker, Raymod J.; Pang, Ye; Tang, Chaoling; Huang, Shiyong; El-Alaoui, Mostafa; Yuan, Zhigang; Li, Huimin

2013-04-01

352

What is a plasma?  

SciTech Connect

This introduction will define the plasma fourth state of matter, where we find plasmas on earth and beyond, and why they are useful. There are applications to many consumer items, fusion energy, scientific devices, satellite communications, semiconductor processing, spacecraft propulsion, and more. Since 99% of our observable universe is ionized gas, plasma physics determines many important features of astrophysics, space physics, and magnetosphere physics in our solar system. We describe some plasma characteristics, examples in nature, some useful applications, how to create plasmas. A brief introduction to the theoretical framework includes the connection between kinetic and fluid descriptions, quasi neutrality, Debye shielding, ambipolar electric fields, some plasma waves. Hands-on demonstrations follow. More complete explanations will follow next week.

Intrator, Thomas P. [Los Alamos National Laboratory

2012-08-30

353

Effect of Type of Dietary Fat, Cholesterol and Chenodeoxycholic Acid on Gallstone Formation, Bile Acid Kinetics and Plasma Lipids in Squirrel Monkeys1  

Microsoft Academic Search

To explore the effect of type of dietary fat, cholesterol and chenodeoxycholic acid on gallstone formation, bile formation, bile com position, bile acid kinetics and plasma lipids in squirrel monkeys, 39 monkeys were studied using seven different diets. Samower oil, a highly unsaturated fat, added to a diet with cholesterol resulted in at least as high an incidence of cholesterol

NAOMI TANAKA; OSCAR W. PORTMAN

354

Arbitrary amplitude double layers in warm dust kinetic Alfven wave plasmas  

SciTech Connect

Large amplitude electrostatic structures associated with low-frequency dust kinetic Alfvenic waves are investigated under the pressure (temperature) gradient indicative of dust dynamics. The set of equations governing the dust dynamics, Boltzmann electrons, ions and Maxwell's equation have been reduced to a single equation known as the Sagdeev potential equation. Parameter ranges for the existence of arbitrary amplitude double layers are observed. Exact analytical expressions for the energy integral is obtained and computed numerically through which sub-Alfvenic arbitrary amplitude rarefactive double layers are found to exist.

Gogoi, Runmoni; Devi, Nirupama [Department of Mathematics, Cotton College, Guwahati-781001, Assam (India)

2008-07-15

355

Kinetic studies of the transfer of esterified cholesterol between human plasma low and high density lipoproteins  

Microsoft Academic Search

In vitro incubations (6 hr at 37°C) of human low density lipoproteins (LDL), high density lipoproteins (HDL), and lipoprotein-free plasma revealed no significant net mass transfers of esterified cholesterol from either lipo- protein fraction to the other. Transfers of esterified (3H)cholesterol from LDL to HDL must therefore have represented a process of molecular exchange between the two fractions. In molar

Philip J. Barter; Michael E. Jones

356

Dynamics of kinetic geodesic-acoustic modes and the radial electric field in tokamak neoclassical plasmas  

Microsoft Academic Search

We present edge gyrokinetic simulations of tokamak plasmas using the fully non-linear (full-f) continuum code TEMPEST. A non-linear Boltzmann model is used for the electrons. The electric field is obtained by solving the 2D gyrokinetic Poisson equation. We demonstrate the following. (1) High harmonic resonances (n > 2) significantly enhance geodesic-acoustic mode (GAM) damping at high q (tokamak safety factor),

X. Q. Xu; E. Belli; K. Bodi; J. Candy; C. S. Chang; R. H. Cohen; P. Colella; A. M. Dimits; M. R. Dorr; Z. Gao; J. A. Hittinger; S. Ko; S. Krasheninnikov; G. R. McKee; W. M. Nevins; T. D. Rognlien; P. B. Snyder; J. Suh; M. V. Umansky

2009-01-01

357

Plasma Arginine and Citrulline Kinetics in Adults Given Adequate and Arginine-Free Diets  

Microsoft Academic Search

The fluxes of arginine and citrulline through plasma and the rate of conversion of labeled citrulline to arginine were estimated in two pilot studies (with a total of six adult subjects) and in a dietary study with five healthy young men. These latter subjects received an L-amino acid-based diet that was arginine-rich or arginine-free each for 6 days prior to

Leticia Castillo; Thomas E. Chapman; Melchor Sanchez; Yong-Ming Yu; John F. Burke; Alfred M. Ajami; Josef Vogt; Vernon R. Young

1993-01-01

358

In situ ellipsometric monitoring of GaAs surface modifications during plasma processing: chemistry and kinetics  

Microsoft Academic Search

In situ real time ellipsometry has been applied to control and monitor GaAs exposure to H2, O2 and N2 plasmas for the processes of native oxide removal, oxidation and nitridation, respectively. Single wavelength ellipsometry is suitable for detecting the cleaning end-point and for defining the optimal cleaning conditions, whereas both single wavelength and spectroscopic ellipsometry measurements are needed to elucidate

M. Losurdo; P Capezzuto; G Bruno

1998-01-01

359

Kinetics of inflow of matter from electrodes in a radiating cluster of arc discharge plasma  

Microsoft Academic Search

The spectrum of the radiation of a gas-discharge plasma cluster is linked with the inflow of the material of the electrodes into the interelectrode space. Therefore the characteristics of the emission of matter from the electrodes can have a significant effect on the results of spectral analysis. It is known [1-3] that in a variable-current arc the disintegration of the

I. G. Nekrashevich; V. M. Tkachenko

1969-01-01

360

Kinetic model of electric potentials in localized collisionless plasma structures under steady quasi-gyrotropic conditions  

SciTech Connect

Localized plasma structures, such as thin current sheets, generally are associated with localized magnetic and electric fields. In space plasmas localized electric fields not only play an important role for particle dynamics and acceleration but may also have significant consequences on larger scales, e.g., through magnetic reconnection. Also, it has been suggested that localized electric fields generated in the magnetosphere are directly connected with quasi-steady auroral arcs. In this context, we present a two-dimensional model based on Vlasov theory that provides the electric potential for a large class of given magnetic field profiles. The model uses an expansion for small deviation from gyrotropy and besides quasineutrality it assumes that electrons and ions have the same number of particles with their generalized gyrocenter on any given magnetic field line. Specializing to one dimension, a detailed discussion concentrates on the electric potential shapes (such as 'U' or 'S' shapes) associated with magnetic dips, bumps, and steps. Then, it is investigated how the model responds to quasi-steady evolution of the plasma. Finally, the model proves useful in the interpretation of the electric potentials taken from two existing particle simulations.

Schindler, K. [Ruhr University Bochum, 44780 Bochum (Germany); Birn, J. [Space Science Institute, Boulder, Colorado 80301 (United States); Hesse, M. [Nasa Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States)

2012-08-15

361

Glycogen phosphorylase isoenzyme BB plasma kinetics is not related to myocardial ischemia induced by exercise stress echo test.  

PubMed

Abstract Background: Glycogen phosphorylase BB (GPBB) is released from cardiac cells during myocyte damage. Previous studies have shown contradictory results regarding the relation of enzyme release and reversible myocardial ischemia. The aim of this study was to determine the plasma kinetics of GPBB as a response to the exercise stress echocardiographic test (ESET), and to define the relationship between myocardial ischemia and enzyme plasma concentrations. Methods: We studied 46 consecutive patients undergoing ESET, with recent coronary angiography. In all patients, a submaximal stress echo test according to Bruce protocol was performed. Concentration of GPBB was measured in peripheral blood that was sampled 5 min before and 10, 30 and 60 min after ESET. Results: There was significant increase of GPBB concentration after the test (p=0.021). Significant increase was detected 30 min (34.9% increase, p=0.021) and 60 min (34.5% increase, p=0.016) after ESET. There was no significant effect of myocardial ischemia on GPBB concentrations (p=0.126), and no significant interaction between sampling intervals and myocardial ischemia, suggesting a similar release profile of GPBB in ischemic and non-ischemic conditions (p=0.558). Patients in whom ESET was terminated later (stages 4 or 5 of standard Bruce protocol; n=13) had higher GPBB concentrations than patients who terminated ESET earlier (stages 1, 2 or 3; n=33) (p=0.049). Baseline GPBB concentration was not correlated to any of the patients' demographic, clinical and hemodynamic characteristics. Conclusions: GPBB plasma concentration increases after ESET, and it is not related to inducible myocardial ischemia. However, it seems that GPBB release during ESET might be related to exercise load/duration. PMID:23729628

Dobric, Milan; Giga, Vojislav; Beleslin, Branko; Ignjatovic, Svetlana; Paunovic, Ivana; Stepanovic, Jelena; Djordjevic-Dikic, Ana; Kostic, Jelena; Nedeljkovic, Ivana; Nedeljkovic, Milan; Tesic, Milorad; Dajak, Marijana; Ostojic, Miodrag

2013-10-01

362

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES: Numerical Simulation of Solitary Kinetic Alfvén Waves  

NASA Astrophysics Data System (ADS)

Using the two-fluid model in the case of ? ? 1 (? = ?/2Q, ? is the ratio of thermal pressure to magnetic pressure, and Q = me/mi), we numerically investigate the interactions between two solitary kinetic Alfvén waves (SKAWs) and between an SKAW and a density discontinuity. The results show that the two SKAWs would remain in their original shapes and propagate at their initiating speeds, which indicates that SKAWs behave just like standard solitons. The simulation also shows that SKAWs will reflect and refract when crossing a discontinuity and propagating into a higher density region. The transmission wave is an SKAW with increasing density, and the reverberation is a disturbance with lower amplitude.

Ding, Jian; Li, Yi; Wang, Shui

2008-07-01

363

Transition form collisional to kinetic reconnection in large-scale plasmas  

SciTech Connect

Using first-principles fully kinetic simulations with a Fokker-Planck collision operator, it is demonstrated that Sweet-Parker reconnection layers are unstable to a chain of plasmoids (secondary islands) for Lundquist numbers beyond S >{approx} 1000. The instability is increasingly violent at higher Lundquist number, both in terms of the number of plasmoids produced and the super-Alfvenic growth rate. A dramatic enhancement in the reconnection rate is observed when the half-thickness of the current sheet between two plasmoids approaches the ion inertial length. During this transition, the reconnection electric field rapidly exceeds the runaway limit, resulting in the formation of electron-scale current layers that are unstable to the continual formation of new plasmoids.

Daughton, William S [Los Alamos National Laboratory; Roytershteyn, Vadim S [Los Alamos National Laboratory; Albright, Brian J [Los Alamos National Laboratory; Yin, Lin [Los Alamos National Laboratory; Bowers, Kevin J [Los Alamos National Laboratory; Karimabadi, Homa [UCSD

2009-01-01

364

Plasma Effects on Fast Pair Beams. II. Reactive versus Kinetic Instability of Parallel Electrostatic Waves  

NASA Astrophysics Data System (ADS)

The interaction of TeV gamma-rays from distant blazars with the extragalactic background light produces relativistic electron-positron pair beams by the photon-photon annihilation process. Using the linear instability analysis in the kinetic limit, which properly accounts for the longitudinal and the small but finite perpendicular momentum spread in the pair momentum distribution function, the growth rate of parallel propagating electrostatic oscillations in the intergalactic medium is calculated. Contrary to the claims of Miniati and Elyiv, we find that neither the longitudinal nor the perpendicular spread in the relativistic pair distribution function significantly affect the electrostatic growth rates. The maximum kinetic growth rate for no perpendicular spread is even about an order of magnitude greater than the corresponding reactive maximum growth rate. The reduction factors in the maximum growth rate due to the finite perpendicular spread in the pair distribution function are tiny and always less than 10–4. We confirm earlier conclusions by Broderick et al. and our group that the created pair beam distribution function is quickly unstable in the unmagnetized intergalactic medium. Therefore, there is no need to require the existence of small intergalactic magnetic fields to scatter the produced pairs, so that the explanation (made by several authors) for the Fermi non-detection of the inverse Compton scattered GeV gamma-rays by a finite deflecting intergalactic magnetic field is not necessary. In particular, the various derived lower bounds for the intergalactic magnetic fields are invalid due to the pair beam instability argument.

Schlickeiser, R.; Krakau, S.; Supsar, M.

2013-11-01

365

Computational Plasma Physics at the Bleeding Edge: Simulating Kinetic Turbulence Dynamics in Fusion Energy Sciences  

NASA Astrophysics Data System (ADS)

Advanced computing is generally recognized to be an increasingly vital tool for accelerating progress in scientific research in the 21st Century. The imperative is to translate the combination of the rapid advances in super-computing power together with the emergence of effective new algorithms and computational methodologies to help enable corresponding increases in the physics fidelity and the performance of the scientific codes used to model complex physical systems. If properly validated against experimental measurements and verified with mathematical tests and computational benchmarks, these codes can provide more reliable predictive capability for the behavior of complex systems, including fusion energy relevant high temperature plasmas. The magnetic fusion energy research community has made excellent progress in developing advanced codes for which computer run-time and problem size scale very well with the number of processors on massively parallel supercomputers. A good example is the effective usage of the full power of modern leadership class computational platforms from the terascale to the petascale and beyond to produce nonlinear particle-in-cell simulations which have accelerated progress in understanding the nature of plasma turbulence in magnetically-confined high temperature plasmas. Illustrative results provide great encouragement for being able to include increasingly realistic dynamics in extreme-scale computing campaigns to enable predictive simulations with unprecedented physics fidelity. Some illustrative examples will be presented of the algorithmic progress from the magnetic fusion energy sciences area in dealing with low memory per core extreme scale computing challenges for the current top 3 supercomputers worldwide. These include advanced CPU systems (such as the IBM-Blue-Gene-Q system and the Fujitsu K Machine) as well as the GPU-CPU hybrid system (Titan).

Tang, William

2013-04-01

366

Plasma reactivity in high-power impulse magnetron sputtering through oxygen kinetics  

NASA Astrophysics Data System (ADS)

The atomic oxygen metastable dynamics in a Reactive High-Power Impulse Magnetron Sputtering (R-HiPIMS) discharge has been characterized using time-resolved diode laser absorption in an Ar/O2 gas mixture with a Ti target. Two plasma regions are identified: the ionization region (IR) close to the target and further out the diffusion region (DR), separated by a transition region. The ?s temporal resolution allows identifying the main atomic oxygen production and destruction routes, which are found to be very different during the pulse as compared to the afterglow as deduced from their evolution in space and time.

Vitelaru, Catalin; Lundin, Daniel; Brenning, Nils; Minea, Tiberiu

2013-09-01

367

Multicomponent kinetic spectrophotometric determination of pefloxacin and norfloxacin in pharmaceutical preparations and human plasma samples with the aid of chemometrics.  

PubMed

A spectrophotometric method for the simultaneous determination of the important pharmaceuticals, pefloxacin and its structurally similar metabolite, norfloxacin, is described for the first time. The analysis is based on the monitoring of a kinetic spectrophotometric reaction of the two analytes with potassium permanganate as the oxidant. The measurement of the reaction process followed the absorbance decrease of potassium permanganate at 526 nm, and the accompanying increase of the product, potassium manganate, at 608 nm. It was essential to use multivariate calibrations to overcome severe spectral overlaps and similarities in reaction kinetics. Calibration curves for the individual analytes showed linear relationships over the concentration ranges of 1.0-11.5 mg L(-1) at 526 and 608 nm for pefloxacin, and 0.15-1.8 mg L(-1) at 526 and 608 nm for norfloxacin. Various multivariate calibration models were applied, at the two analytical wavelengths, for the simultaneous prediction of the two analytes including classical least squares (CLS), principal component regression (PCR), partial least squares (PLS), radial basis function-artificial neural network (RBF-ANN) and principal component-radial basis function-artificial neural network (PC-RBF-ANN). PLS and PC-RBF-ANN calibrations with the data collected at 526 nm, were the preferred methods--%RPE(T) approximately 5, and LODs for pefloxacin and norfloxacin of 0.36 and 0.06 mg L(-1), respectively. Then, the proposed method was applied successfully for the simultaneous determination of pefloxacin and norfloxacin present in pharmaceutical and human plasma samples. The results compared well with those from the alternative analysis by HPLC. PMID:18060832

Ni, Yongnian; Wang, Yong; Kokot, Serge

2007-10-23

368

Kinetics Analysis of the Plasma Membrane Sucrose-H+ Symporter from Sugar Beet (Beta vulgaris L.) Leaves.  

PubMed Central

The kinetics behavior of the H+-sucrose (Suc) symporter was investigated in plasma membrane vesicles from sugar beet (Beta vulgaris L.) leaves by analyzing the effect of external and internal pH (pHo and pHi, respectively) on Suc uptake. The apparent Km for Suc uptake increased 18-fold as the pHo increased from 5.5 to 7.5. Over this same pHo range, the apparent Vmax for Suc uptake remained constant. The effects of pHi in the presence or absence of internal Suc were exclusively restricted to changes in Vmax. Thus, proton concentration on the inside of the membrane vesicles ([H+]i) behaved as a noncompetitive inhibitor of Suc uptake. The Km for the proton concentration on the outside of the membrane vesicles was estimated to be pH 6.3, which would indicate that at physiological apoplastic pH Suc transport might be sensitive to changes in pHo. On the other hand, the [H+]i for half-maximal inhibition of Suc uptake was approximately pH 5.4, making regulation of Suc transport through changes in [H+]i unlikely. These results were interpreted in the framework of the kinetics models for co-transport systems developed by D. Sanders, U.-P. Hansen, D. Gradmann, and C. L. Slayman (J Membr Biol [1984] 77: 123-152). Based on their analysis, the behavior of the Suc symporter with respect to the [H+]i is interpreted as an ordered binding mechanism by which the binding of Suc on the apoplastic side of the membrane and its release on the symplastic side precedes that of H+ (i.e. a first-on, first-off model).

Buckhout, T. J.

1994-01-01

369

Kinetics of polar mesospheric plasma layers: Comparison of theoretical results with observations  

SciTech Connect

This paper presents an analytical model for the physical understanding of the charge distribution on ice dust particles in plasma layers of polar mesospheric clouds PMCs (Noctilucent clouds and polar mesospheric summer echoes). For the case of pure ice dust (with high work function), the charging of the particles occurs only because of the accretion of electronic and ionic species on the surface of ice grains. The analysis is based on the number and energy balance of constituents and allows the charge to be only an integral multiple (positive or negative) of the electronic charge. Amongst other interesting results, the theory explains the observed charge distribution on pure ice particles and corresponding reduction of electron density (viz., Bite out) in the PMCs.

Sodha, M. S.; Misra, Shikha; Mishra, S. K. [Department of Education Building, University of Lucknow, Lucknow 226007 (India); Dixit, Amrit [Disha Institute of Management and Technology, Satya Vihar, Vidhan Sabha-Chandrakhuri Marg, Mandir Hasaud, Raipur 492101, Chhattisgarh (India)

2011-08-15

370

Comparison of initial value and eigenvalue codes for kinetic toroidal plasma instabilities  

SciTech Connect

In plasma physics, linear instability calculations can be implemented either as initial value calculations or as eigenvalue calculations. Here, comparisons between comprehensive linear gyrokinetic calculations employing the ballooning formalism for high-n (toroidal mode number) toroidal instabilities are described. One code implements an initial value calculation on a grid using a Lorentz collision operator and the other implements an eigenvalue calculation with basis functions using a Krook collision operator. An electrostatic test case with artificial parameters for the toroidal drift mode destabilized by the combined effects of trapped particles and an ion temperature gradient has been carefully analyzed both in the collisionless limit and with varying collisionality. Good agreement is found. Results from applied studies using parameters from the Tokamak Fusion Test Reactor (TFTR) experiment are also compared.

Kotschenreuther, M. [Univ. of Texas, Austin, TX (United States). Institute for Fusion Studies; Rewoldt, G.; Tang, W.M. [Princeton Univ., NJ (United States). Plasma Physics Lab.

1994-04-01

371

Kinetics of plasma membrane electron transport in a pulmonary endothelial cell-column.  

PubMed

Thiazine dyes such as toluidine blue O (TBO) are reduced at the luminal endothelial surface. The purpose of this study was to determine the rate of this reaction in endothelial cells in culture. A multiple indicator dilution method was used to measure the reaction kinetics during transient passage of a TBO-containing bolus through a chromatographic column filled with bovine pulmonary arterial endothelial cells grown on microcarrier beads (cell-column). A bolus containing TBO and an inert extracellular reference indicator (FITC-Dextran) was injected upstream of the cell-column, and the indicator concentrations were measured downstream using on-line photodetection. The effects of column flow rate, PO2, and TBO concentration were studied. The fraction of TBO reduced upon passage through the cell-column decreased with increasing flow indicating that the reaction rate rather than TBO delivery controlled TBO reduction. The fraction of TBO reduced did not change with PO2 or dose in the ranges studied. TBO reduction was about 10 times that for steady state TBO sequestration by these cells which, along with the lack of a PO2 effect indicates that the rapid rate of reduction is not the rate-limiting step in steady state sequestration. PMID:10355556

Olson, L E; Merker, M P; Bongard, R D; Brantmeier, B M; Audi, S H; Linehan, J H; Dawson, C A

372

Plasma transport in stochastic magnetic fields. III. Kinetics of test-particle diffusion  

SciTech Connect

A discussion is given of test particle transport in the presence of specified stochastic magnetic fields, with particular emphasis on the collisional limit. Certain paradoxes and inconsistencies in the literature regarding the form of the scaling laws are resolved by carefully distinguishing a number of physically distinct correlation lengths, and thus by identifying several collisional subregimes. The common procedure of averaging the conventional fluid equations over the statistics of a random field is shown to fail in some important cases because of breakdown of the Chapman-Enskog ordering in the presence of a stochastic field component with short autocorrelation length. A modified perturbation theory is introduced which leads to a Kubo-like formula valid in all collisionality regimes. The direct-interaction approximation is shown to fail in the interesting limit in which the orbit exponentiation length L/sub K/ appears explicitly. A higher order renormalized kinetic theory in which L/sub K/ appears naturally is discussed and used to rederive more systematically the results of the heuristic scaling arguments.

Krommes, J.A.; Oberman, C.; Kleva, R.G.

1982-07-01

373

Electrical description of a magnetic pole enhanced inductively coupled plasma source: Refinement of the transformer model by reverse electromagnetic modeling  

SciTech Connect

The magnetic pole enhanced inductively coupled source (MaPE-ICP) is an innovative low-pressure plasma source that allows for high plasma density and high plasma uniformity, as well as large-area plasma generation. This article presents an electrical characterization of this source, and the experimental measurements are compared to the results obtained after modeling the source by the equivalent circuit of the transformer. In particular, the method applied consists in performing a reverse electromagnetic modeling of the source by providing the measured plasma parameters such as plasma density and electron temperature as an input, and computing the total impedance seen at the primary of the transformer. The impedance results given by the model are compared to the experimental results. This approach allows for a more comprehensive refinement of the electrical model in order to obtain a better fitting of the results. The electrical characteristics of the system, and in particular the total impedance, were measured at the inductive coil antenna (primary of the transformer). The source was modeled electrically by a finite element method, treating the plasma as a conductive load and taking into account the complex plasma conductivity, the value of which was calculated from the electron density and electron temperature measurements carried out previously. The electrical characterization of the inductive excitation source itself versus frequency showed that the source cannot be treated as purely inductive and that the effect of parasitic capacitances must be taken into account in the model. Finally, considerations on the effect of the magnetic core addition on the capacitive component of the coupling are made.

Meziani, T.; Colpo, P.; Rossi, F. [European Commission-Joint Research Centre, IHCP, TP 203, Via E. Fermi 1, 21020 Ispra (Vatican City State, Holy See,) (Italy)

2006-02-01

374

Kinetic theory of electromagnetic plane wave obliquely incident on bounded plasma slab  

SciTech Connect

The effects of electromagnetic plane waves obliquely incident on a warm bounded plasma slab of finite length L are studied by solving the coupled Vlasov-Maxwell set of equations. It is shown that the solution can be greatly simplified in the limit where thermal effects are most important by expanding in small parameters and introducing self-similar variables. These solutions reveal that the coupling of thermal effects with the angle of incidence is negligible in the region of bounce resonance and anomalous skin effect. In the region of the anomalous skin effect, the heating is shown to scale linearly with the anomalous skin depth {delta}{sub a} when {delta}{sub a}<>L, the heating is shown to decay with 1/{delta}{sub a}{sup 3}. The transmission is found to be exponentially larger than that predicted from a local theory in the appropriate region of the anomalous skin effect.

Angus, J. R.; Krasheninnikov, S. I. [Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, California 92093-0411 (United States); Smolyakov, A. I. [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, Saskatchewan (Canada)

2010-10-15

375

Electron kinetic effects on interferometry and polarimetry in high temperature fusion plasmas  

NASA Astrophysics Data System (ADS)

At anticipated high electron temperatures in ITER, the effects of electron thermal motion on phase measurements made by the toroidal interferometer/polarimeter (TIP) and poloidal polarimeter (PoPola) diagnostics will be significant and must be precisely treated or the measurement accuracy will fail to meet the specified requirements for ITER operation. We calculate electron thermal corrections to the interferometric phase and polarization state of an electromagnetic wave propagating along tangential and poloidal chords (Faraday and Cotton-Mouton polarimetry) and incorporate them into the Stokes vector equation for evolution of polarization. Although these corrections are small at electron temperatures Te ? 1 keV, they become sizable at Te ? 10 keV. The precision of the previous lowest order linear in the ? = Te/mec2 model may be insufficient; we present a more precise model with ?2-order corrections to satisfy the high accuracy required for ITER TIP and PoPola diagnostics. Proper treatment of temperature effects will ensure more accurate interpretation of interferometric and polarimetric measurements in fusion devices like ITER and DEMO. The use of precise analytic expressions is especially important for burning plasmas where various interferometric techniques will be used for direct real time feedback control of device operations with time resolution ˜1 ms to regulate the rate of the thermonuclear burn and monitor/control the safety factor profile.

Mirnov, V. V.; Brower, D. L.; Den Hartog, D. J.; Ding, W. X.; Duff, J.; Parke, E.

2013-11-01

376

Observation of nonlinear couplings between coexisting kinetic geodesic acoustic modes in the edge plasmas of the HT-7 tokamak  

NASA Astrophysics Data System (ADS)

Coexisting multi-geodesic acoustic modes (GAMs), especially coexisting dual GAMs, are observed and studied through Langmuir probe arrays at the edge plasmas of the HT-7 tokamak with lithium-coated walls. The dual GAMs are named a low-frequency GAM (LFGAM) and a high-frequency GAM (HFGAM), and it is found that within the measuring range, the HFGAM propagates outwards while the LFGAM propagates both inwards and outwards with their central frequencies nearly unchanged, and both modes have maximum amplitudes at positions with radial wavenumbers close to zero; meanwhile, the two positions happen to be where the continuum GAM frequency is closest to the central frequencies of the LFGAM and the HFGAM. These characteristics are consistent with those of a kinetic GAM converted from a continuum GAM. The nonlinear couplings between the LFGAM and the HFGAM are also analysed. In this study, we observed not only the interaction between the LFGAM and the HFGAM, but also the self-coupling of the GAM with the beat frequency between them, as well as the coupling between the LFGAM and an unknown mode at ?50 kHz. These nonlinear interactions may play important roles during the saturation process of GAMs. Additionally, amplitude correlation analyses of multi-GAMs indicate that second harmonic GAMs are probably generated from the self-interaction of fundamental GAMs.

Kong, D. F.; Liu, A. D.; Lan, T.; Qiu, Z. Y.; Zhao, H. L.; Sheng, H. G.; Yu, C. X.; Chen, L.; Xu, G. S.; Zhang, W.; Wan, B. N.; Chen, R.; Ding, W. X.; Sun, X.; Xie, J. L.; Li, H.; Liu, W. D.

2013-11-01

377

Properties of cupric ions in benzylamine oxidase from pig plasma as studied by magnetic-resonance and kinetic methods.  

PubMed Central

Benzylamine oxidase from pig plasma has been studied by a variety of chemical and physical techniques. 1. Analytical ultracentrifugation, gel electrophoresis and isoelectric-focusing studies suggest that the enzyme is composed of two subunits with closely similar primary structures. 2. E.s.r. and n.m.r. measurements show that the enzyme contains two well-separated (greater than 0.6 nm) Cu2+ ions at chemically distinct sites. Each Cu2+ ion is coordinated by two water molecules, one 'axial' and the other 'equatorial'. Both water molecules undergo fast exchange (10(5)--10(8) s-1) with solvent and are deprotonated in the pH range 8--9, but only the equatorial water molecule is displaced by the inhibitors N3- and CN-. 3. Kinetic and e.s.r. measurements show that azide and cyanide compete against O2 binding and also make the two Cu2+ sites identical. It is concluded that Cu2+ must participate in the re-oxidation of reduced enzyme by molecular O2.

Barker, R; Boden, N; Cayley, G; Charlton, S C; Henson, R; Holmes, M C; Kelly, I D; Knowles, P F

1979-01-01

378

Chemical kinetics modelling of a decaying SF6 arc plasma in the presence of a solid organic insulator, copper, oxygen and water  

Microsoft Academic Search

The composition variations occurring in decaying SF6 arc plasmas in the presence of atoms released from the vaporization of organic insulators (e.g. Teflon, polyethylene, polypropylene, megelit, nylon), copper, oxygen and water were studied between 12 000 K and 300 K by means of a chemical kinetics model. From the results obtained at 300 K and a pressure of 101.3 kPa:

I. Coll; A. M. Casanovas; L. Vial; A. Gleizes; J. Casanovas

2000-01-01

379

Measurement of Fluorocarbon Radicals Generated from C4F8\\/H2 Inductively Coupled Plasma: Study on SiO2 Selective Etching Kinetics  

Microsoft Academic Search

The kinetics of highly selective SiO2 etching were studied on the basis of appearance mass spectroscopy (AMS) measurement of fluorocarbon radicals generated from C4F8\\/H2 inductlvely coupled plasma (ICP). Results obtained by varying of H2 concentration in C4F8, total pressure and RF power implied that CF1 radical played a major role in the polymer film deposition. In particular, radical measurements carried

Kazuhiro Kubota; Hiroyuki Matsumoto; Haruo Shindo; Shoso Shingubara; Yasuhiro Horiike

1995-01-01

380

Higher-order growth rate of instability of obliquely propagating kinetic Alfvén and ion-acoustic solitons in a magnetized non-thermal plasma  

Microsoft Academic Search

The higher-order growth rate of instability for obliquely propagating kinetic Alfvén and ion-acoustic solitons in a magnetized non-thermal plasma have been obtained by the multiple-scale perturbation expansion method developed by Allen and Rowlands (1993). The growth rate of instability is obtained correct to order k2, where k is the wave number of a long-wavelength plane-wave perturbation. The corresponding lowest-order stability

Anup Bandyopadhyay; K. P. Das

2001-01-01

381

Activation of the Guinea Pig Granulocyte NAD(P)H-Dependent Superoxide Generating Enzyme: Localization in a Plasma Membrane Enriched Particle and Kinetics of Activation  

Microsoft Academic Search

The subcellular localization, kinetics of activation, and substrate specificity of the guinea pig granulocyte superoxide (02) generating system was investigated. Membrane-enriched particles (podosomes) were made from granulocytes by mild sonication and differential centrifugation. These podosomes are enriched threefold for known plasma membrane markers, 5'-nucleotidase, and adenylate cyclase. Podosomes made from resting granulocytes have very little NAD(P)H-dependent 02 production. Podosomes made

Harvey J. Cohen; Margaret E. Chovaniec; Wayne A. Davies; Brian G. M. Dune; Sydney E. Salmon; Thomas E. Moon; Jay H. Beckstead; Dorothy F. Bainton; Stephen E. Sallan; Jerome Ritz; John Pesando; Richard Gelben; Carmeline O'Brien; Suzanne Hitchcock; Felice Coral; Stuart F. Schlossman

1980-01-01

382

Sheared rotation effects on kinetic stability in enhanced confinement tokamak plasmas, and nonlinear dynamics of fluctuations and flows in axisymmetric plasmas  

NASA Astrophysics Data System (ADS)

Sheared rotation dynamics are widely believed to have significant influence on experimentally-observed confinement transitions in advanced operating modes in major tokamak experiments, such as DIII-D and TFTR with reversed magnetic shear regions in the plasma interior, or the VH-mode or high-li H-mode for DIII-D. The high-n toroidal instabilities destabilized by the combined effects of ion temperature gradients and trapped particles in toroidal geometry can be strongly affected by radially-sheared toroidal and poloidal plasma rotation. In previous work with the FULL linear microinstability code, a simplified rotation model including only toroidal rotation was employed, and results were obtained for DIII-D and TFTR. However, a more complete rotation model, that includes contributions from toroidal and poloidal rotation and the ion pressure gradient to the total radial electric field, is needed for a proper self-consistent treatment of this key problem. Both models result in additional stabilizing or destabilizing drifts added to the normal magnetic drifts. Specifically, this new model is capable of including effects of the E × B shearing, written in terms of equilibrium quantities, ?E ~= |[(R B_?)^2 / B] d/d? (E_r/RB_?)|, on an equal basis with the other rotation model terms in the linear instability calculation. All of the rotation terms are now evaluated for a numerically-calculated flux-coordinate MHD equilibrium with magnetic surfaces of arbitrary cross-sectional shape and aspect ratio. Needed Er levels for marginal stability with this approach will be compared with corresponding levels from the heuristic stabilization criterion ?E ~ ?, as observed in ITG simulations, where ? is the linear growth rate without rotation effects, which has sometimes shown good correlations with experimental transitions. Relevant advanced operating mode cases for DIII-D, TFTR, JET, JT-60U, and NSTX will be presented. In addition, the complementary problem of the dynamics of fluctuation-driven E × B flow is investigated by an integrated program of analytic nonlinear theory, gyrokinetic simulation in annulus geometry, and gyrofluid simulation in flux tube geometry. New three-dimensional global gyrokinetic simulations systematically including both collisional and turbulent transport contributions will help assess the validity regimes for estimates of poloidal rotation damping and buildup. The flow dynamics is studied kinetically via a high-order Lie-perturbative analysis of the bounce-averaged Vlasov and Poisson equations.

Rewoldt, G.

1997-11-01

383

Growth kinetics and doping of gallium nitride grown by rf-plasma assisted molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

A reduced rate for growth of GaN by plasma-assisted molecular beam epitaxy often limits growth to temperatures less than 750°C, with the reduction significantly larger than thermal decomposition rates. Conditions producing a flux consisting predominantly of either atomic nitrogen or nitrogen metastables have been established using various rf-sources. Atomic nitrogen, possibly coupled with the presence of low energy ions, is associated with the premature decrease in growth rate. An active nitrogen flux consisting primarily of nitrogen metastables produces a temperature dependence more consistent with decomposition rates. Growth with molecular nitrogen metastables results in significantly improved electrical properties. Magnesium incorporation was studied for both (0001), or Ga-polarity and (0001), or N-polarity, orientations for various growth conditions. A significant dependence on surface polarity of Mg incorporation was observed, with up to a factor of twenty-five times more Mg incorporated on the Ga-polarity. Measurements supported surface accumulation of Mg during growth, with stable accumulations of close to a monolayer of Mg. Mg coverage of a monolayer on the Ga-polarity induced a surface polarity inversion. Atomic hydrogen was found to increase the incorporation of Mg without also incorporating potentially compensating hydrogen. Beryllium incorporation was also studied for both polarities of GaN. Unlike Mg, surface polarity-related incorporation differences were less pronounced for Be. Measurements also support surface accumulation of Be during growth, with stable accumulations approaching a monolayer for heavier doping levels. Transmission electron microscopy studies indicate the surface layer of Be has a significant effect on structure, with severe degradation occurring when accumulation nears monolayer coverage. High-quality GaN films were grown to study the dependence of controlled oxygen incorporation on polarity and oxygen partial pressure. Oxygen concentrations up to 2.5 x 1022 cm-3 were obtained. About 10 times more oxygen incorporates on N-polar GaN than on the Ga-polarity in high quality epilayers. Oxygen doping is controllable, reproducible, and uncompensated up to concentrations of at least 1018 cm-3 with higher levels showing significant compensation. Layers with oxygen levels above 1022 cm-3 exhibit severe cracking. Oxygen incorporation has a weak dependence on Ga overpressure during Ga-stable growth but dramatically increases for conditions approaching N-stable growth.

Ptak, Aaron Joseph

384

Human muscle sympathetic nerve activity and plasma noradrenaline kinetics in space  

PubMed Central

Astronauts returning from space have reduced red blood cell masses, hypovolaemia and orthostatic intolerance, marked by greater cardio–acceleration during standing than before spaceflight, and in some, orthostatic hypotension and presyncope. Adaptation of the sympathetic nervous system occurring during spaceflight may be responsible for these postflight alterations. We tested the hypotheses that exposure to microgravity reduces sympathetic neural outflow and impairs sympathetic neural responses to orthostatic stress. We measured heart rate, photoplethysmographic finger arterial pressure, peroneal nerve muscle sympathetic activity and plasma noradrenaline spillover and clearance, in male astronauts before, during (flight day 12 or 13) and after the 16 day Neurolab space shuttle mission. Measurements were made during supine rest and orthostatic stress, as simulated on Earth and in space by 7 min periods of 15 and 30 mmHg lower body suction. Mean (± s.e.m.) heart rates before lower body suction were similar pre–flight and in flight. Heart rate responses to ?30 mmHg were greater in flight (from 56 ± 4 to 72 ± 4 beats min?1) than pre–flight (from 56 ± 4 at rest to 62 ± 4 beats min?1, P < 0.05). Noradrenaline spillover and clearance were increased from pre–flight levels during baseline periods and during lower body suction, both in flight (n = 3) and on post–flight days 1 or 2 (n = 5, P < 0.05). In–flight baseline sympathetic nerve activity was increased above pre–flight levels (by 10–33 %) in the same three subjects in whom noradrenaline spillover and clearance were increased. The sympathetic response to 30 mmHg lower body suction was at pre–flight levels or higher in each subject (35 pre–flight vs. 40 bursts min?1 in flight). No astronaut experienced presyncope during lower body suction in space (or during upright tilt following the Neurolab mission). We conclude that in space, baseline sympathetic neural outflow is increased moderately and sympathetic responses to lower body suction are exaggerated. Therefore, notwithstanding hypovolaemia, astronauts respond normally to simulated orthostatic stress and are able to maintain their arterial pressures at normal levels.

Ertl, Andrew C; Diedrich, Andre; Biaggioni, Italo; Levine, Benjamin D; Robertson, Rose Marie; Cox, James F; Zuckerman, Julie H; Pawelczyk, James A; Ray, Chester A; Buckey, Jay C; Lane, Lynda D; Shiavi, Richard; Gaffney, F Andrew; Costa, Fernando; Holt, Carol; Blomqvist, C Gunnar; Eckberg, Dwain L; Baisch, Friedhelm J; Robertson, David

2002-01-01

385

Plasma-assisted combustion: Systematic decoupling of the kinetic enhancement mechanisms of ignition, flame propagation, and flame stabilization by long-lifetime species  

NASA Astrophysics Data System (ADS)

The advancement of propulsion devices and combustion systems has created ever increasingly more restrictive reactive environments that push the limits of combustion technology. Precise combustion control for higher efficiencies, reduced emissions, and limited residence times to react can exceed what is possible with traditional combustion chemistry, and therefore require new and creative solutions. The application of plasma to combustion systems offers a promising solution, with significant enhancement having been shown by many researchers. Nevertheless, there remain many unknowns with respect to the key species and mechanisms of enhancement. Detailed systematic experimental and numerical investigations were performed to identify the kinetic mechanisms of combustion enhancement by long-lifetime species generated by non-equilibrium plasma discharges. Two burner systems were adopted and integrated with plasma discharge devices to establish unique combustion platforms to study ignition, flame propagation, and flame stabilization phenomena. A counterflow diffusion flame burner was adopted for the investigation of the effects of plasma on flame stabilization. A newly developed non-equilibrium magnetic gliding arc plasma discharge was integrated with a counterflow diffusion flame burner and was found to significantly extend the limits of flame stabilization when activating air. Laser diagnostic methods of planar Rayleigh scattering and OH planar laser-induced fluorescence were applied and comparison to numerical simulations showed that the extension of the extinction limits was predominately through thermal effects due to rapid recombination of radicals. To elucidate the kinetic effects of plasma, the counterflow burner was augmented for ignition experiments. The application of Fourier transform infrared spectroscopy and comparison to numerical simulations showed significant kinetic ignition enhancement by plasma-produced NOx when activating air. The results established the existence of new ignition regimes for NO x addition that were strongly dependent upon the strain rates (residence times) in the system. The addition of small concentrations of fuel to the air upstream of the plasma produced fuel fragments and partially oxidized products that inhibited ignition. The dominating effects of plasma-produced NOx significantly mitigated the inhibitive effects of these species on chain-branching reaction pathways. To further decouple the plasma-flame interaction, the two long-lifetime plasma species of O3 and O2(a1Delta g) were produced, isolated, measured, and transported to a lifted flame burner to investigate their effect on flame propagation speed. The effects of O3 at atmospheric and sub-atmospheric pressure were found to be significant because of the decomposition of O3 releasing O to rapidly react with the fuel and extract chemical heat early in the pre-heat zone of the flame. The effect of O2(a1Delta g) was isolated by the addition of NO to the plasma afterglow to eliminate O3 and O catalytically. The O2(a1Delta g) was isolated, measured quantitatively using high sensitivity off-axis integrated cavity output absorption spectroscopy, and observed to enhance flame speed. The comparison of experimental and numerical simulation results showed that the current enhancement mechanism including O2(a 1Deltag) could not accurately explain the increase in flame speed observed. Furthermore, a novel filter system was developed to minimize the concentration of all plasma-produced species other than O3 and O2(a1Deltag) through gas phase and wall surface quenching. Lastly, a new simplified and well-defined plasma-combustion system was developed to provide a platform to study the plasma-flame interaction. In addition, a flow visualization technique was proposed by using plasma activation and NO seeding which could be applied to a system where particle seeding of the flow is prohibitive.

Ombrello, Timothy M.

386

Rotavirus NSP4: Cell type-dependent transport kinetics to the exofacial plasma membrane and release from intact infected cells  

PubMed Central

Background Rotavirus NSP4 localizes to multiple intracellular sites and is multifunctional, contributing to RV morphogenesis, replication and pathogenesis. One function of NSP4 is the induction of early secretory diarrhea by binding surface receptors to initiate signaling events. The aims of this study were to determine the transport kinetics of NSP4 to the exofacial plasma membrane (PM), the subsequent release from intact infected cells, and rebinding to naïve and/or neighboring cells in two cell types. Methods Transport kinetics was evaluated using surface-specific biotinylation/streptavidin pull-downs and exofacial exposure of NSP4 was confirmed by antibody binding to intact cells, and fluorescent resonant energy transfer. Transfected cells similarly were monitored to discern NSP4 movement in the absence of infection or other viral proteins. Endoglycosidase H digestions, preparation of CY3- or CY5- labeled F(ab)2 fragments, confocal imaging, and determination of preferential polarized transport employed standard laboratory techniques. Mock-infected, mock-biotinylated and non-specific antibodies served as controls. Results Only full-length (FL), endoglycosidase-sensitive NSP4 was detected on the exofacial surface of two cell types, whereas the corresponding cell lysates showed multiple glycosylated forms. The C-terminus of FL NSP4 was detected on exofacial-membrane surfaces at different times in different cell types prior to its release into culture media. Transport to the PM was rapid and distinct yet FL NSP4 was secreted from both cell types at a time similar to the release of virus. NSP4-containing, clarified media from both cells bound surface molecules of naïve cells, and imaging showed secreted NSP4 from one or more infected cells bound neighboring cell membranes in culture. Preferential sorting to apical or basolateral membranes also was distinct in different polarized cells. Conclusions The intracellular transport of NSP4 to the PM, translocation across the PM, exposure of the C-terminus on the cell surface and subsequent secretion occurs via an unusual, complex and likely cell-dependent process. The exofacial exposure of the C-terminus poses several questions and suggests an atypical mechanism by which NSP4 traverses the PM and interacts with membrane lipids. Mechanistic details of the unconventional trafficking of NSP4, interactions with host-cell specific molecules and subsequent release require additional study.

2011-01-01

387

Analytical Description of the Process of Influx of the Sample Material into an Alternating-Current Arc Discharge Plasma  

Microsoft Academic Search

Physical and mathematical models of the influx of the sample material into an alternating-current arc discharge plasma are suggested. Analytical expressions describing changes in the rate of influx of the base metal and impurities into the discharge have been derived. Experimental results on the rates of influx of elements from metal samples of gold and silver are presented. They are

E. S. Voropai; A. P. Zazhogin; K. I. Chervyakovskii

2004-01-01

388

Advanced oxidation processes. description of a kinetic model for the oxidation of hazardous materials in aqueous media with ozone and hydrogen peroxide in a semibatch reactor  

Microsoft Academic Search

A model is presented that describes the kinetics of the oxidation of micropollutants in water with the combination of ozone and hydrogen peroxide in a sparged, semibatch reactor. The model is based on known reactions of the Oâ\\/HâOâ system plus mass-transfer characteristics of the reactor. The principal kinetic species for micropollutant oxidation is assumed to be the hydroxyl radical. The

William H. Glaze; Joon Wun Kang

1989-01-01

389

Interaction between two shock waves in a collisionless plasma: Description of the behavior of the heliospheric termination shock  

SciTech Connect

A shock in a collisionless plasma should be treated as a place where the superthermal particles are continuously produced. The Rankine-Hugoniot conditions modified so as to describe the loss of the energy flux during the production process are presented. The model of the interaction between the two colliding shocks in the collisionless magnetized plasma is used to describe the behavior of the heliospheric termination shock. Both forward-reverse and reverse-reverse shock pairs are considered. In consequence of these interactions the termination shock is in a constant in and out motion with velocities equal to 100-200 km/s. The dependence of the interaction parameters on the production efficiency of the superthermal population is discussed. 15 refs., 6 figs.

Ziemkiewicz, J. [Space Research Center, Warsaw (Poland)

1995-09-01

390

Geometric description of the magnetic field and plasma coupling in the near-Earth stretched tail prior to a substorm  

Microsoft Academic Search

Topological properties of the self-organized magnetic field and plasma turbulence in the near-Earth stretched tail prior to the magnetospheric substorm onset are analyzed. We found that the magnetotail turbulence structures at the late substorm growth phase should be associated with the hierarchical (“singular”) geometry; this geometry includes fractal objects, i.e., self-similar “clumpy” structures with “voids” present on many scales. The

Alexander V Milovanov; Lev M Zelenyi; Pierluigi Veltri; Gaetano Zimbardo; Alexander L Taktakishvili

2001-01-01

391

Kinetic waves near the drift frequency  

NASA Astrophysics Data System (ADS)

We consider the possibility of dynamically significant kinetic waves, of the type observed previously in the ion acoustic and ion-cyclotron frequency range, in a weakly- collisional, nearly-maxwellian plasma. The calculation is motivated by recent experimental results of drift-wave fluctuations which are clearly outside of a fluid description. Experiments and theory have shown that in non-maxwellian weakly collisional plasma there can exist multiple modes, in addition to the fluid modes. These are effectively other Landau poles; remnants of the Case-Van Kampen continuum. Normally, kinetic modes represent rapidly phase-mixed perturbations (and thus strongly damped modes), but in non-maxwellian plasma these modes may be weakly damped. Experimentally, these kinetic modes can account for a large fraction of the plasma fluctuation. Even a relatively small component of kinetic waves could change the phase between density and ExB velocity and have a significant impact on particle transport. A technique for finding the dispersion relation using a Hilbert transform on measured ion distribution functions, that has been used at ion cyclotron frequencies, is generalized to treat fluctuations at drift wave frequencies.

Skiff, Fred

2003-10-01

392

Study of gradient effects on inertial Alfvén waves in plasma sheet boundary layer region—kinetic approach  

NASA Astrophysics Data System (ADS)

Inertial Alfvén waves are investigated using Maxwell-Boltzmann-Vlasov equation to evaluate the dispersion relation and growth/damping rate in inhomogeneous plasma. Expressions for the dispersion relation and growth/damping rate are evaluated in inhomogeneous plasma. The effects of density, temperature and velocity gradient are included in the analysis. The results are interpreted for the space plasma parameters appropriate to the plasma sheet boundary layer. It is found that the inhomogeneities of plasma contribute significantly to enhance the growth rate of inertial Alfvén wave. The applicability of this model is assumed for auroral acceleration region and plasma sheet boundary layer.

Agarwal, P.; Varma, P.; Tiwari, M. S.

2013-09-01

393

Advanced oxidation processes. description of a kinetic model for the oxidation of hazardous materials in aqueous media with ozone and hydrogen peroxide in a semibatch reactor  

SciTech Connect

A model is presented that describes the kinetics of the oxidation of micropollutants in water with the combination of ozone and hydrogen peroxide in a sparged, semibatch reactor. The model is based on known reactions of the O{sub 3}/H{sub 2}O{sub 2} system plus mass-transfer characteristics of the reactor. The principal kinetic species for micropollutant oxidation is assumed to be the hydroxyl radical. The model is tested and validated in distilled water spiked with an excess of bicarbonate, a known hydroxyl radical scavenger.

Glaze, W.H.; Kang, J.W.

1989-01-01

394

Relativistic kinetic theory of magnetoplasmas  

SciTech Connect

Recently, an increasing interest in astrophysical as well as laboratory plasmas has been manifested in reference to the existence of relativistic flows, related in turn to the production of intense electric fields in magnetized systems. Such phenomena require their description in the framework of a consistent relativistic kinetic theory, rather than on relativistic MHD equations, subject to specific closure conditions. The purpose of this work is to apply the relativistic single-particle guiding-center theory developed by Beklemishev and Tessarotto, including the nonlinear treatment of small-wavelength EM perturbations which may naturally arise in such systems. As a result, a closed set of relativistic gyrokinetic equations, consisting of the collisionless relativistic kinetic equation, expressed in hybrid gyrokinetic variables, and the averaged Maxwell's equations, is derived for an arbitrary four-dimensional coordinate system.

Beklemishev, Alexei [Budker Institute of Nuclear Physics, Novosibirsk (Russian Federation); Nicolini, Piero [Department of Mathematics and Informatics, University of Trieste (Italy); National Institute of Nuclear Physics (INFN), Trieste Section (Italy); Tessarotto, Massimo [Department of Mathematics and Informatics, University of Trieste (Italy); Consortium for Magnetofluid Dynamics, University of Trieste (Italy)

2005-05-16

395

ADVANCED OXIDATION PROCESSES - DESCRIPTION OF A KINETIC MODEL FOR THE OXIDATION OF HAZARDOUS MATERIALS IN AQUEOUS MEDIA WITH OZONE AND HYDROGEN PEROXIDE IN A SEMIBATCH REACTOR  

EPA Science Inventory

A model is presented that describes the kinetics of the oxidation of micropollutants in water with the combination of ozone and hydrogen peroxide in a sparged, semi batch reactor. he model is based on known reactions of the O3/H2O2 system plus mass-transfer characteristics of the...

396

Energetic particle physics with applications in fusion and space plasmas  

SciTech Connect

Energetic particle physics is the study of the effects of energetic particles on collective electromagnetic (EM) instabilities and energetic particle transport in plasmas. Anomalously large energetic particle transport is often caused by low frequency MHD instabilities, which are driven by these energetic particles in the presence of a much denser background of thermal particles. The theory of collective energetic particle phenomena studies complex wave-particle interactions in which particle kinetic physics involving small spatial and fast temporal scales can strongly affect the MHD structure and long-time behavior of plasmas. The difficulty of modeling kinetic-MHD multiscale coupling processes stems from the disparate scales which are traditionally analyzed separately: the macroscale MHD phenomena are studied using the fluid MHD framework, while microscale kinetic phenomena are best described by complicated kinetic theories. The authors have developed a kinetic-MHD model that properly incorporates major particle kinetic effects into the MHD fluid description. For tokamak plasmas a nonvariational kinetic-MHD stability code, the NOVA-K code, has been successfully developed and applied to study problems such as the excitation of fishbone and Toroidal Alfven Eigenmodes (TAE) and the sawtooth stabilization by energetic ions in tokamaks. In space plasmas the authors have employed the kinetic-MHD model to study the energetic particle effects on the ballooning-mirror instability which explains the multisatellite observation of the stability and field-aligned structure of compressional Pc 5 waves in the magnetospheric ring current plasma.

Cheng, C.Z.

1997-05-01

397

Statistical derivation of basic equations of diffusional kinetics in alloys with application to the description of diffusion of carbon in austenite  

SciTech Connect

Basic equations of diffusional kinetics in alloys are statistically derived using the master equation approach. To describe diffusional transformations in substitution alloys, we derive the 'quasi-equilibrium' kinetic equation that generalizes its earlier versions by taking possible 'interaction renormalization' effects into account. For the interstitial alloys Me-X, we derive an explicit expression for the diffusivity D of an interstitial atom X. This expression notably differs from those used in previous phenomenological treatments. This microscopic expression for D is applied to describe the diffusion of carbon in austenite based on some simple models of carbon-carbon interaction. The results obtained enable us to make certain conclusions about the real form of these interactions and about the scale of the 'transition state entropy' for diffusion of carbon in austenite.

Vaks, V. G., E-mail: vaks@mbslab.kiae.ru; Zhuravlev, I. A. [National Research Center 'Kurchatov Institute,' Dolgoprudnyi (Russian Federation)

2012-10-15

398

The effect of pH on the kinetics of spontaneous Fe(II) oxidation by O 2 in aqueous solution – basic principles and a simple heuristic description  

Microsoft Academic Search

The spontaneous chemical oxidation of Fe(II) to Fe(III) by O2 is a complex process involving meta-stable partially oxidized intermediate species such as green rusts, which ultimately transform into a variety of stable iron oxide end-products such as hematite, magnetite, goethite and lepidocrocite. Although in many practical situations the nature of the end-products is of less interest than the oxidation kinetics,

Barak Morgan; Ori Lahav

2007-01-01

399

Kinetic description of the transition from a one-phase to a two-phase growth regime in Al\\/Pd lateral diffusion couples  

Microsoft Academic Search

The kinetics of the solid-state reaction between Al and Pd is studied in the geometry of a lateral Al-Pd diffusion couple in the temperature range between 250 and 430 °C. The first reaction phase is the crystalline Al3Pd2(?) phase. After the growth of Al3Pd2 reaches a critical length, the quasicrystalline decagonal Al3Pd(?’) phase starts to grow in between the Al

B. Blanpain; J. W. Mayer; Joyce C. Liu; K. N. Tu

1990-01-01

400

Culture of Normal Human Blood Cells in a Diffusion Chamber System II. Lymphocyte and Plasma Cell Kinetics.  

National Technical Information Service (NTIS)

Normal human blood leukocytes were cultured in Millipore diffusion chambers implanted into the peritoneal cavities of irradiated mice. The evaluation of survival and proliferation kinetics of cells in lymphyocytic series suggested that the lymphoid cells ...

G. Chikkappa A. L. Carsten A. D. Chanana E. P. Cronkite

1979-01-01

401

Plasma kinetics of an oral dose of [2H4]retinyl acetate in human subjects with estimated low or high total body stores of vitamin A.  

PubMed

The deuterated retinol dilution technique is an indirect method for quantitatively estimating total body stores of vitamin A by using the postequilibration plasma isotopic ratio [2H4]retinol:retinol and the prediction model described by Furr et al (Am J Clin Nutr 1989;49:713-6). Limited data are available on the time required for an oral dose of labeled vitamin A to mix with vitamin A body stores in human subjects. This article describes the plasma retinol kinetics of an oral dose of [2H4] retinyl acetate in 4 healthy adults (2 men and 2 women) and 1 healthy female child in the United States and in 4 Bangladeshi women. After an oral dose of [2H4]retinyl acetate was administered, plasma samples were collected at 6, 12, and 24 h postdose during the first day and at 15 time points during the subsequent 90-d period for measurement of plasma [2H4]retinol:retinol. The mean respective plasma isotopic ratios on day 20 for US and Bangladeshi subjects (0.02 +/- 0.02 and 0.17 +/- 0.12, P = 0.03) and estimated total body vitamin A reserves (1.03 +/- 0.45 and 0.10 +/- 0.11 mmol, P = 0.003) were significantly different. The fraction of dose in plasma was plotted against time, and biexponential equations were fit to the kinetic data by using the time points from 24 h through day 90. The mean equilibration time (time required for the fraction of dose in plasma to reach a plateau) for all subjects was 16.6 +/- 3.8 d (11-23 d). There was no difference in estimated equilibration time between the group of US and Bangladeshi adult subjects (17.5 +/- 4.4 and 16.3 +/- 3.9 d, respectively, P = 0.69). Thus, the size of hepatic vitamin A reserves does not appear to affect equilibration time within the range of values observed. PMID:9665101

Haskell, M J; Islam, M A; Handelman, G J; Peerson, J M; Jones, A D; Wahed, M A; Mahalanabis, D; Brown, K H

1998-07-01

402

Quantification of the plasma clearance kinetics of a gadolinium-based contrast agent by photoinduced triplet harvesting.  

PubMed

The use of gadolinium-based contrast agents (GBCA) is integral to the field of diagnostic magnetic resonance imaging (MRI). Pharmacokinetic evaluation of the plasma clearance of GBCA is required for all new agents or improved formulations, to address concerns over toxicity or unforeseen side effects. Current methods to measure GBCA in plasma lack either a rapid readout or the sensitivity to measure small samples or require extensive processing of plasma, all obstacles in the development and characterization of new GBCA. Here, we quantify the plasma concentration of a labeled analogue of a common clinical GBCA by ligand triplet harvesting and energy transfer. The nonemittive GBCA becomes a "dark donor" to a fluorescent detector molecule, with a lower limit of detection of 10(-7) M in unprocessed plasma. On a time scale of minutes, we determine the plasma clearance rate in the wild-type mouse, using time-resolved fluorescence on a standard laboratory plate reader. PMID:22971115

Russell, Stewart; Casey, Ryan; Hoang, Dung M; Little, Benjamin W; Olmsted, Peter D; Rumschitzki, David S; Wadghiri, Youssef Zaim; Fisher, Edward A

2012-09-18

403

Deuterium enrichment of plasma determined by nuclear magnetic resonance spectroscopy: Dilution kinetics of sup 2 H sub 2 O and estimation of total body water  

SciTech Connect

We demonstrate the feasibility of quantifying the abundance of {sup 2}H in plasma by nuclear magnetic resonance (NMR) spectroscopy. After adding internal standard (tert-butyl-d9 alcohol) to deproteinized plasma samples containing {sup 2}H{sub 2}O, we determined the ratio of NMR peak areas for {sup 2}H{sub 2}O and tert-butyl-d9 alcohol. This peak-area ratio was directly proportional to the exogenous {sup 2}H enrichment of plasma (difference between measured and naturally occurring {sup 2}H) between 0 and 0.272 atom % (r = 0.999). The coefficient of variation was 1.34% at an exogenous enrichment of 0.136 atom %. We applied this method to a study of the dilution kinetics of {sup 2}H{sub 2}O to determine the optimal time and method of blood sampling for estimation of total body water content. The {sup 2}H enrichment of plasma stabilized by 4 h after intravenous injection of {sup 2}H{sub 2}O, 1 g/kg of body weight, and fluctuated within 2-4% of the 4- to 8-h mean thereafter.

Brans, Y.W.; Schwartz, C.A.; Hood, R.J.; Ksebati, M.B.; Konduri, G.G. (Wayne State Univ., Detroit, MI (USA))

1990-10-01

404

Simulation of ECR Discharges with Kinetic Treatment of Resonant Absorption  

NASA Astrophysics Data System (ADS)

We have formulated the ECR absorption process in terms of a wave kinetic equation, together with a self-consistent quasilinear representation of the plasma electron response. The distribution of deposited energy with respect to the electron velocities is correctly represented, so the scheme is compatible with a full kinetic description of the plasma. The formulation integrates analytically over the time scale of the microwave frequency; numerical time steps can be orders of magnitude longer. This absorption model is used within our 2-D quasineutral PIC/MC code QUASI-rz, which provides a full kinetic description of the plasma without having to resolve short time scales such as the plasma frequency and gyrofrequency, and which includes Coulomb collisions between charged particles as well as elastic and inelastic encounters between charged and neutral particles. We present spatially resolved calculations of the electron and ion velocity distributions in argon and chlorine plasmas, and discuss the possibility of tailoring the electron distribution function by adjusting the magnetic field profile in the absorption region.

Lampe, M.; Manheimer, W. M.; Joyce, G.; Fernsler, R. F.; Slinker, S. P.

1998-11-01

405

BBGKY kinetic approach for an e{sup -}e{sup +}{gamma} plasma created from the vacuum in a strong laser-generated electric field: The one-photon annihilation channel  

SciTech Connect

In the present work a closed system of kinetic equations is obtained from the truncation of the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy for the description of the vacuum creation of an electron-positron plasma and secondary photons due to a strong laser field. This truncation is performed in the Markovian approximation for the one-photon annihilation channel which is accessible due to the presence of the strong external field. Estimates of the photon production rate are obtained for different domains of laser field parameters (frequency {nu} and field strength E). A huge quantity of optical photons of the quasiclassical laser field is necessary to satisfy the conservation laws of the energy and momentum of the constituents (e{sup -}, e{sup +} and {gamma}) in this channel. Since the number of these optical photons corresponds to the order of perturbation theory, a vanishingly small photon production rate results for the optical region and strongly subcritical fields E<

Blaschke, D. B. [Institute for Theoretical Physics, University of Wroclaw, 50-204 Wroclaw (Poland); Bogoliubov Laboratory for Theoretical Physics, Joint Institute for Nuclear Research, RU - 141980 Dubna (Russian Federation); Dmitriev, V. V.; Smolyansky, S. A. [Department of Physics, Saratov State University, RU - 410026 Saratov (Russian Federation); Roepke, G. [Institut fuer Physik, University of Rostock, D - 18051 Rostock (Germany)

2011-10-15

406

Kinetics of human soluble and membrane-bound catechol O-methyltransferase: a revised mechanism and description of the thermolabile variant of the enzyme.  

PubMed

Human soluble (S) and membrane-bound (MB) catechol O-methyltransferase (COMT, EC 2.1.1.6) enzymes have been expressed at sufficiently high levels in Escherichia coli and in baculovirus-infected insect cells to allow kinetic characterization of the enzyme forms. The use of tight-binding inhibitors such as entacapone enabled the estimation of actual enzyme concentrations and, thereby, comparison of velocity parameters, substrate selectivity, and regioselectivity of the methylation of both enzyme forms. Kinetics of the methylation reaction of dopamine, (-)-noradrenaline, L-dopa, and 3,4-dihydroxybenzoic acid was studied in detail. Here, the catalytic number (Vmax) of S-COMT was somewhat higher than that of MB-COMT for all four substrates. The Km values varied considerably, depending on both substrate and enzyme form. S-COMT showed about 15 times higher Km values for catecholamines than MB-COMT. The distinctive difference between the enzyme forms was also the higher affinity of MB-COMT for the coenzyme S-adenosyl-L-methionine (AdoMet). The average dissociation constants Ks were 3.4 and 20.2 microM for MB-COMT and S-COMT, respectively. Comparison between the kinetic results and the atomic structure of S-COMT is presented, and a revised mechanism for the reaction cycle is discussed. Two recently published human COMT cDNA sequences differed in the position of S-COMT amino acid 108, the residue being either Val-108 [Lundström et al. (1991) DNA Cell. Biol. 10, 181-189] or Met-108 [Bertocci et al. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 1416-1420].(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7703232

Lotta, T; Vidgren, J; Tilgmann, C; Ulmanen, I; Melén, K; Julkunen, I; Taskinen, J

1995-04-01

407

Nonlinear Langmuir wave modulation in weakly magnetized plasmas  

Microsoft Academic Search

It is assumed that the magnetic field is only important for the ion motion. Both a fluid and a kinetic description of the ions are considered. It is found that the presence of electrostatic ion cyclotron waves, in addition to the ion acoustic waves also found in unmagnetized plasmas, has a strong influence on the modulation stability of plane Langmuir

K B Dysthe; H L Pécseli

1978-01-01

408

Exposure to glyceryl trinitrate during gun powder production: plasma glyceryl trinitrate concentration, elimination kinetics, and discomfort among production workers  

Microsoft Academic Search

Plasma glyceryl trinitrate (GTN) concentration was studied in 12 volunteers producing gun powder. Serial blood samples were obtained from the cubital vein before and during work at two sites of production; high concentrations of GTN were detected in the plasma. Control specimens from a femoral vein contained much less GTN, indicating that blood in the cubital vein was enriched by

K Gjesdal; S Bille; J E Bredesen; E Bjørge; B Halvorsen; K Langseth; P K Lunde; E Silvertssen

1985-01-01

409

Prediction of steady-state plasma levels of nortriptyline from single oral dose kinetics: A study in twins  

Microsoft Academic Search

Five identical (monozygotic) and 6 fraternal (dizygotic) sets of healthy twins between 47 and 53 years of age were given a single oral dose of nortriptyline (NT) hydrochloride 1 mg\\/kg. The plasma half-life, the apparent volume of distribution, and the plasma clearance of NT were estimated for each subject as well as the urinary excretion rate of conjugated and unconjugated

B. Alexanderson

1973-01-01

410

Evaluation of transporter-mediated hepatic uptake in a non-radioactive high-throughput assay: a study of kinetics, species difference and plasma protein effect.  

PubMed

1.?In this manuscript we describe a non-radioactive, high-throughput method to evaluate hepatic uptake using cryopreserved hepatocytes. We have validated the uptake of pravastatin with different amounts of hepatocytes and the impact of the oil layer used in separation. The time- and concentration-dependent uptake profiles of several anionic and cationic charged drugs were evaluated. The results with our method compare favourably with the literature for pravastatin, atorvastatin and estrone 3-sulfate. 2.?Two approaches for kinetic determination (temperature difference and fitting the linear and non-saturable passive diffusion rate in the equation, i.e. V = (V(max) × S)/(K(m) + S) + P(dif) × S) have been evaluated. Kinetic studies indicate that the different approaches for determining passive diffusion can affect K(m) and V(max), but not the clearance of active uptake (V(max)/K(m)). 3.?Using pravastatin as a probe substrate, species differences were observed in the organic anion-transporting polypeptide (OATP) 1B1 and 1B3 activities. Plasma protein significantly reduced the uptake of atorvastatin, but not pravastatin. 4.?Our data suggests that evaluation of the role of active uptake in hepatic clearance in humans should consider the relative ratio of active uptake to passive diffusion, species differences and plasma protein binding when applying in vitro uptake data. PMID:22928802

Li, Ling; Nouraldeen, Amr; Wilson, Alan G E

2012-08-28

411

Modulatory ATP binding to the E2 state of maize plasma membrane H(+) -ATPase indicated by the kinetics of vanadate inhibition.  

PubMed

P-type ATPases, as major consumers of cellular ATP in eukaryotic cells, are characterized by the formation of a phosphorylated enzyme intermediate (E2P), a process that is allosterically coupled to translocation of cations against an electrochemical gradient. The catalytic cycle comprises binding of Mg-ATP at the nucleotide-binding domain, phosphorylation of the E1 state (E1), conformational transition to the E2P state, and dephosphorylation through the actuator domain and re-establishment of the E1 state. Recently, it has been suggested that, for several P-type ATPases, Mg-ATP binds to the phosphorylated enzyme, thereby accelerating the transition to the E1 state, before then becoming the enzyme's catalytic substrate. Here, we provide evidence supporting this viewpoint. We employed kinetic models based on steady-state kinetics in the presence and absence of the reversible inhibitor orthovanadate. Vanadate is generally considered to be a conformational probe that specifically binds to the E2 state, arresting the enzyme in a state analogous to the E2P state. Hydrolytic H(+) -ATPase activities were measured in inside-out plasma membrane vesicles isolated from roots and shoots of maize plants. For root enzymes, kinetic models of vanadate inhibition that allow simultaneous binding of Mg-ATP and vanadate to the same enzyme state were most plausible. For shoot enzymes, application of the competitive inhibitor Mg-free ATP attenuated vanadate inhibition, which is consistent with a model in which either Mg-free ATP or Mg-ATP is bound to the enzyme when vanadate binds. Therefore, data from roots and shoots indicate that binding of ATP species before transition to the E1 state plays an important role in the catalytic cycle of plant plasma membrane H(+) -ATPase. PMID:23879673

Wang, Xiaozhi; Qian, Xiaoqing; Stumpf, Beate; Fatima, Ammara; Feng, Ke; Schubert, Sven; Hanstein, Stefan

2013-08-23

412

Saturation of backward stimulated scattering of laser in kinetic regime: Wavefront bowing, trapped particle modulational instability, and trapped particle self-focusing of plasma waves  

SciTech Connect

Backward stimulated Raman and Brillouin scattering (SRS and SBS) of laser are examined in the kinetic regime using particle-in-cell simulations. The SRS reflectivity measured as a function of the laser intensity in a single hot spot from two-dimensional (2D) simulations shows a sharp onset at a threshold laser intensity and a saturated level at higher intensities, as obtained previously in Trident experiments [D.