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CHAPTER 5. PLASMA DESCRIPTIONS I: KINETIC, TWO-FLUID 1 Plasma Descriptions I

CHAPTER 5. PLASMA DESCRIPTIONS I: KINETIC, TWO-FLUID 1 Chapter 5 Plasma Descriptions I: Kinetic, Two-Fluid Descriptions of plasmas are obtained from extensions of the kinetic theory of gases of charged particles in the plasma, and because the electric and magnetic fields in the plasma must

Callen, James D.

2

Kinetic description of electron plasma waves with orbital angular momentum

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

3

On description of quantum plasma

A plasma becomes quantum when the quantum nature of its particles significantly affects its macroscopic properties. To answer the question of when the collective quantum plasma effects are important, a proper description of such effects is necessary. We consider here the most common methods of description of quantum plasma, along with the related assumptions and applicability limits. In particular, we analyze in detail the hydrodynamic description of quantum plasma, as well as discuss some kinetic features of analytic properties of linear dielectric response function in quantum plasma. We point out the most important, in our view, fundamental problems occurring already in the linear approximation and requiring further investigation. (submitted to Physics-Uspekhi)

S. V. Vladimirov; Yu. O. Tyshetskiy

2011-01-21

4

A closed theoretical model to describe slow, macroscopic plasma processes in a fusion-relevant collisionality regime is set forward. This formulation is a hybrid one, with fluid conservation equations for particle number, momentum and energy, and drift-kinetic closures. Intended for realistic application to the core of a high-temperature tokamak plasma, the proposed approach is unconventional in that the ion collisionality is ordered lower than in the ion banana regime of neoclassical theory. The present first part of a two-article series concerns the electron system, which is still equivalent to one based on neoclassical electron banana orderings. This system is derived such that it ensures the precise compatibility among the complementary fluid and drift-kinetic equations, and the rigorous treatment of the electric field and the Fokker-Planck-Landau collision operators. As an illustrative application, the special limit of an axisymmetric equilibrium is worked out in detail.

Ramos, J. J. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge Massachusetts 02139-4307 (United States)

2010-08-15

5

Kinetic description of avalanching systems.

Avalanching systems are treated analytically using the renormalization group (in the self-organized-criticality regime) or mean-field approximation, respectively. The latter describes the state in terms of the mean number of active and passive sites, without addressing the inhomogeneity in their distribution. This paper goes one step further by proposing a kinetic description of avalanching systems making use of the distribution function for clusters of active sites. We illustrate an application of the kinetic formalism to a model proposed for the description of the avalanching processes in the reconnecting current sheet of the Earth's magnetosphere. A description of avalanching systems is proposed that makes use of the distribution function for clusters of active sites. A general kinetic equation is derived that describes the temporal evolution of the distribution function, in terms of growth and shrinking probabilities. The distribution of clusters is derived for the stationary regime, for a quite general class of avalanching systems or arbitrary dimensionality. The approach, including the probability calculation, is illustrated by an application of the kinetic description to the recently proposed burning model. PMID:16241616

Gedalin, M; Balikhin, M; Coca, D; Consolini, G; Treumann, R A

2005-09-01

6

Wave-kinetic description of atmospheric turbulence

NASA Astrophysics Data System (ADS)

We propose a wave-kinetic description of atmospheric turbulence, where the turbulence spectrum is described as a gas of quasi-particles. We apply this description to the case of zonal structures in the atmosphere, which can be excited by internal gravity wave turbulence. A general expression for the instability growth rates is derived, and the particular example of a nearly mono-kinetic turbulent spectrum is discussed.

Mendonça, J. T.; Onishchenko, O. G.; Pokhotelov, O. A.; Stenflo, L.

2014-12-01

7

Lagrangian description of warm plasmas

NASA Technical Reports Server (NTRS)

Efforts are described to extend the averaged Lagrangian method of describing small signal wave propagation and nonlinear wave interaction, developed by earlier workers for cold plasmas, to the more general conditions of warm collisionless plasmas, and to demonstrate particularly the effectiveness of the method in analyzing wave-wave interactions. The theory is developed for both the microscopic description and the hydrodynamic approximation to plasma behavior. First, a microscopic Lagrangian is formulated rigorously, and expanded in terms of perturbations about equilibrium. Two methods are then described for deriving a hydrodynamic Lagrangian. In the first of these, the Lagrangian is obtained by velocity integration of the exact microscopic Lagrangian. In the second, the expanded hydrodynamic Lagrangian is obtained directly from the expanded microscopic Lagrangian. As applications of the microscopic Lagrangian, the small-signal dispersion relations and the coupled mode equations are derived for all possible waves in a warm infinite, weakly inhomogeneous magnetoplasma, and their interactions are examined.

Kim, H.

1970-01-01

8

Kinetic Description of a Granular Particle Ensemble

NASA Astrophysics Data System (ADS)

Including adhesive effects in the description of viscoelastic binary particle collisions, we are able to reproduce the main features of lab experiments done for icy particles at low temperatures. In terms of the coefficient of restitution, it is furthermore possible to tell aggregation from restitution. A critical impact velocity for aggregation to occur has been obtained. Collisional outcomes are crucially determined by the impacting speed and masses of the collision partners. Since collisions can either result in aggregation, restitution, or fragmentation, the velocity-mass parameter space will be devided accordingly and thus the validity of kinetic equations such as the Smoluchowski equation will be limited. We numerically simulated the size distribution dynamics of a granular particle ensemble. Here we present a combined kinetic description and discuss the influence of fragmentation due to catastrophic impacts on otherwise reduced growth processes. This work is funded by the Studienstiftung des deutschen Volkes.

Albers, N.; Spahn, F.

2005-08-01

9

Kinetic theory of relativistic plasmas

NASA Technical Reports Server (NTRS)

The thermalization of particle kinetic motion by binary collisions is considered for a plasma with a Boltzmann constant-temperature product approximately equal to 10 to 100 times the product of the electron mass with the square of the speed of light. At this temperature, the principal mechanism for relaxation of electron motion is via radiationless electron-electron collisions (Moller scattering). Ions are nonrelativistic, but are energetic enough so that their Coulomb scattering can be treated in the Born approximation. Relaxation times are computed and Boltzmann-equation Fokker-Planck operators are derived for the various binary-collision processes. The expression for the rate of kinetic energy exchange between electron and ion gases is derived for the case where the gases are at different temperatures.

Gould, R. J.

1981-01-01

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Kinetic Profiles in NSTX Plasmas

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

11

Kinetic theory of plasma waves, homogeneous plasmas

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

12

NLTE4 Plasma Population Kinetics Database

National Institute of Standards and Technology Data Gateway

SRD 159 NLTE4 Plasma Population Kinetics Database (Web database for purchase) This database contains benchmark results for simulation of plasma population kinetics and emission spectra. The data were contributed by the participants of the 4th Non-LTE Code Comparison Workshop who have unrestricted access to the database. The only limitation for other users is in hidden labeling of the output results. Guest users can proceed to the database entry page without entering userid and password.

13

A fluid description of plasma double-layers

NASA Technical Reports Server (NTRS)

The space-charge double-layer that forms between two plasmas with different densities and thermal energies was investigated using three progressively realistic models which are treated by fluid theory, and take into account four species of particles: electrons and ions reflected by the double-layer, and electrons and ions transmitted through it. The two plasmas are assumed to be cold, and the self-consistent potential, electric field and space-charge distributions within the double-layer are determined. The effects of thermal velocities are taken into account for the reflected particles, and the modifications to the cold plasma solutions are established. Further modifications due to thermal velocities of the transmitted particles are examined. The applicability of a one dimensional fluid description, rather than plasma kinetic theory, is discussed. Theoretical predictions are compared with double layer potentials and lengths deduced from laboratory and space plasma experiments.

Levine, J. S.; Crawford, F. W.

1979-01-01

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Complete Spectrum of Kinetic Eigenmodes for Plasma

Complete Spectrum of Kinetic Eigenmodes for Plasma Oscillations in a Weakly Collisional Plasma C. S damping rate measured with a discrete spectrum. Ng, Bhattacharjee, & Skiff (1999): discrete collisional spectrum found numerically which tends to Landau spectrum as collision tends to zero. Short & Simon (2002

Ng, Chung-Sang

15

Wave kinetics of relativistic quantum plasmas

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

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Neutral Vlasov kinetic theory of magnetized plasmas

NASA Astrophysics Data System (ADS)

The low-frequency limit of Maxwell equations is considered in the Maxwell-Vlasov system. This limit produces a neutral Vlasov system that captures essential features of plasma dynamics, while neglecting radiation effects. Euler-Poincaré reduction theory is used to show that the neutral Vlasov kinetic theory possesses a variational formulation in both Lagrangian and Eulerian coordinates. By construction, the new model recovers all collisionless neutral models employed in plasma simulations. Then, comparisons between the neutral Vlasov system and hybrid kinetic-fluid models are presented in the linear regime.

Tronci, Cesare; Camporeale, Enrico

2015-02-01

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MHD description of plasma: handbook of plasma physics

The basic sets of MHD equations for the description of a plasma in various limits are derived and their usefulness and limits of validity are discussed. These limits are: the one fluid collisional plasma, the two fluid collisional plasma, the Chew-Goldberger Low formulation of the guiding center limit of a collisionless plasma and the double-adiabatic limit. Conservation relations are derived from these sets and the mathematics of the concept of flux freezing is given. An example is given illustrating the differences between guiding center theory and double adiabatic theory.

Kulsrud, R.M.

1980-10-01

18

Inertial range turbulence in kinetic plasmas

The transfer of turbulent energy through an inertial range from the driving scale to dissipative scales in a kinetic plasma followed by the conversion of this energy into heat is a fundamental plasma physics process. A theoretical foundation for the study of this process is constructed, but the details of the kinetic cascade are not well understood. Several important properties are identified: (a) the conservation of a generalized energy by the cascade; (b) the need for collisions to increase entropy and realize irreversible plasma heating; and (c) the key role played by the entropy cascade--a dual cascade of energy to small scales in both physical and velocity space--to convert ultimately the turbulent energy into heat. A strategy for nonlinear numerical simulations of kinetic turbulence is outlined. Initial numerical results are consistent with the operation of the entropy cascade. Inertial range turbulence arises in a broad range of space and astrophysical plasmas and may play an important role in the thermalization of fusion energy in burning plasmas.

G. G. Howes

2007-11-27

19

Nonlinear Kinetic Modeling of Stimulated Raman Scattering in a Plasma

NASA Astrophysics Data System (ADS)

When a large amplitude plasma wave grows inside a plasma, it strongly modifies the electron distribution function which, in turn, affects the propagation of this wave. The purpose of this paper is to provide a theoretical description of these nonlinear kinetic phenomena when the electrostatic wave results from stimulated Raman scattering (SRS), in order to address the efficiency of this process. In particular, two effects will be discussed in detail, collisionless dissipation, which needs to be described much more generally than by simply resorting to Landau damping, and the impact of the nonlinear variations of the wave frequency on the matching conditions required for the growth of SRS. A very accurate description of these phenomena allows the quantification of Raman reflectivity, which is a key issue for inertial confinement fusion, using an envelope code that runs much faster than those (the so-called kinetic codes) which explicitly calculate the nonlinear variations of the electron distribution function. Comparisons between the outcomes of our envelope modeling and of kinetic simulations will be shown and discussed.

Bénisti, D.

2012-07-01

20

Electron kinetic theory in laser heated plasmas

NASA Astrophysics Data System (ADS)

Since the formulation of the linearized nonlocal hydrodynamic equations [Phys. Rev. Lett. 75, 4405 (1995)] our studies of collisional thermal processes in laser produced plasmas have led to better understanding of the electron transport, plasma fluctuations, electron distribution functions, and parametric instabilities. This talk will discuss some of these advances. The linear nonlocal theory of electron transport is derived from the solution to the Fokker-Planck (FP) equation and provides plasma description, which is valid in the entire range of electron collisionality. Numerical studies involving FP and collisional particle-in-cell codes have confirmed our analytical theories and provided more general results in a nonlinear regime of large perturbations. A nonlinear expression has been proposed for the thermal transport coefficient, which explains numerical results. The nonlocal hydrodynamic equations have been used as the framework for the theoretical description of thermal stimulated Brillouin scattering, filamentation instability, return current instability and hydrodynamical fluctuations. Results from laser plasma interaction and Thomson scattering experiments are consistent with theoretical scenarios involving nonlocal thermal effects. New nonequilibrium electron distribution functions have been found. They occur in laser heated plasmas due to competing effects of strong laser field, inverse bremsstrahlung absorption, electron-electron collisions and plasma inhomogeneity. In addition to well known flattening of the low velocity part, these distribution functions usually display superthermal tails of fast electrons.

Rozmus, Wojciech

2001-10-01

21

A kinetic model of plasma turbulence

NASA Astrophysics Data System (ADS)

A Hybrid Vlasov-Maxwell (HVM) model is presented and recent results about the link between kinetic effects and turbulence are reviewed. Using five-dimensional (2D in space and 3D in the velocity space) simulations of plasma turbulence, it is found that kinetic effects (or non-fluid effects) manifest through the deformation of the proton velocity distribution function (DF), with patterns of non-Maxwellian features being concentrated near regions of strong magnetic gradients. The direction of the proper temperature anisotropy, calculated in the main reference frame of the distribution itself, has a finite probability of being along or across the ambient magnetic field, in general agreement with the classical definition of anisotropy T ?/T ? (where subscripts refer to the magnetic field direction). Adopting the latter conventional definition, by varying the global plasma beta (?) and fluctuation level, simulations explore distinct regions of the space given by T ?/T ? and ??, recovering solar wind observations. Moreover, as in the solar wind, HVM simulations suggest that proton anisotropy is not only associated with magnetic intermittent events, but also with gradient-type structures in the flow and in the density. The role of alpha particles is reviewed using multi-ion kinetic simulations, revealing a similarity between proton and helium non-Maxwellian effects. The techniques presented here are applied to 1D spacecraft-like analysis, establishing a link between non-fluid phenomena and solar wind magnetic discontinuities. Finally, the dimensionality of turbulence is investigated, for the first time, via 6D HVM simulations (3D in both spaces). These preliminary results provide support for several previously reported studies based on 2.5D simulations, confirming several basic conclusions. This connection between kinetic features and turbulence open a new path on the study of processes such as heating, particle acceleration, and temperature-anisotropy, commonly observed in space plasmas.

Servidio, S.; Valentini, F.; Perrone, D.; Greco, A.; Califano, F.; Matthaeus, W. H.; Veltri, P.; Veltri

2015-01-01

22

Nonlocal electron kinetics in collisional gas discharge plasmas

Nonlocal phenomena in electron kinetics of collisional gas discharge plasmas, their kinetic treatment by a nonlocal approach, and relevant experimental results are reviewed in this paper. Using the traditional two-term approximation for the electron distribution function, a general method to analyze electron kinetics in nonuniform plasmas in DC and RF fields for atomic gases is presented for the nonlocal case,

Vladimir I. Kolobov; Valery A. Godyak

1995-01-01

23

Kinetics of wet sodium vapor complex plasma

NASA Astrophysics Data System (ADS)

In this paper, we have investigated the kinetics of wet (partially condensed) Sodium vapor, which comprises of electrons, ions, neutral atoms, and Sodium droplets (i) in thermal equilibrium and (ii) when irradiated by light. The formulation includes the balance of charge over the droplets, number balance of the plasma constituents, and energy balance of the electrons. In order to evaluate the droplet charge, a phenomenon for de-charging of the droplets, viz., evaporation of positive Sodium ions from the surface has been considered in addition to electron emission and electron/ion accretion. The analysis has been utilized to evaluate the steady state parameters of such complex plasmas (i) in thermal equilibrium and (ii) when irradiated; the results have been graphically illustrated. As a significant outcome irradiated, Sodium droplets are seen to acquire large positive potential, with consequent enhancement in the electron density.

Mishra, S. K.; Sodha, M. S.

2014-04-01

24

Kinetics of wet sodium vapor complex plasma

In this paper, we have investigated the kinetics of wet (partially condensed) Sodium vapor, which comprises of electrons, ions, neutral atoms, and Sodium droplets (i) in thermal equilibrium and (ii) when irradiated by light. The formulation includes the balance of charge over the droplets, number balance of the plasma constituents, and energy balance of the electrons. In order to evaluate the droplet charge, a phenomenon for de-charging of the droplets, viz., evaporation of positive Sodium ions from the surface has been considered in addition to electron emission and electron/ion accretion. The analysis has been utilized to evaluate the steady state parameters of such complex plasmas (i) in thermal equilibrium and (ii) when irradiated; the results have been graphically illustrated. As a significant outcome irradiated, Sodium droplets are seen to acquire large positive potential, with consequent enhancement in the electron density.

Mishra, S. K., E-mail: nishfeb@rediffmail.com [Institute for Plasma Research (IPR), Gandhinagar 382428 (India); Sodha, M. S. [Centre of Energy Studies, Indian Institute of Technology Delhi (IITD), New Delhi 110016 (India)] [Centre of Energy Studies, Indian Institute of Technology Delhi (IITD), New Delhi 110016 (India)

2014-04-15

25

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

26

Generalized Langmuir Waves in Magnetized Kinetic Plasmas

NASA Technical Reports Server (NTRS)

The properties of unmagnetized Langmuir waves and cold plasma magnetoionic waves (x, o, z and whistler) are well known. However, the connections between these modes in a magnetized kinetic plasma have not been explored in detail. Here, wave properties are investigated by numerically solving the dispersion equation derived from the Vlasov equations both with and without a beam instability present. For omega(sub p)>Omega(sub e), it is shown that the generalized Langmuir mode at oblique propagation angles has magnetic z-mode characteristics at low wave numbers and thermal Langmuir mode characteristics at high wave numbers. For omega(sub p)

Willes, A. J.; Cairns, Iver H.

2000-01-01

27

Fundamental Statistical Descriptions of Plasma Turbulence in Magnetic Fields

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

28

The Gaussian Radial Basis Function Method for Plasma Kinetic Theory

A fundamental macroscopic description of a magnetized plasma is the Vlasov equation supplemented by the nonlinear inverse-square force Fokker-Planck collision operator [Rosenbluth et al., Phys. Rev., 107, 1957]. The Vlasov part describes advection in a six-dimensional phase space whereas the collision operator involves friction and diffusion coefficients that are weighted velocity-space integrals of the particle distribution function. The Fokker-Planck collision operator is an integro-differential, bilinear operator, and numerical discretization of the operator is far from trivial. In this letter, we describe a new approach to discretize the entire kinetic system based on an expansion in Gaussian Radial Basis functions (RBFs). This approach is particularly well-suited to treat the collision operator because the friction and diffusion coefficients can be analytically calculated. Although the RBF method is known to be a powerful scheme for the interpolation of scattered multidimensional data, Gaussian RBFs also...

Hirvijoki, Eero; Belli, Emily; Embréus, Ola

2015-01-01

29

Ducted kinetic Alfven waves in plasma with steep density gradients

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

30

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

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

31

Kinetic plasma modeling with quiet Monte Carlo direct simulation.

The modeling of collisions among particles in space plasma media poses a challenge for computer simulation. Traditional plasma methods are able to model well the extremes of highly collisional plasmas (MHD and Hall-MHD simulations) and collisionless plasmas (particle-in-cell simulations). However, neither is capable of trealing the intermediate, semi-collisional regime. The authors have invented a new approach to particle simulation called Quiet Monte Carlo Direct Simulation (QMCDS) that can, in principle, treat plasmas with arbitrary and arbitrarily varying collisionality. The QMCDS method will be described, and applications of the QMCDS method as 'proof of principle' to diffusion, hydrodynamics, and radiation transport will be presented. Of particular interest to the space plasma simulation community is the application of QMCDS to kinetic plasma modeling. A method for QMCDS simulation of kinetic plasmas will be outlined, and preliminary results of simulations in the limit of weak pitch-angle scattering will be presented.

Albright, B. J. (Brian J.); Jones, M. E. (Michael E.); Lemons, D. S. (Don S.); Winske, D. (Dan)

2001-01-01

32

Solitary kinetic Alfven waves in dusty plasmas

Solitary kinetic Alfven waves in dusty plasmas are studied by considering the dust charge variation. The effect of the dust charge-to-mass ratio on the soliton solution is discussed. The Sagdeev potential is derived analytically with constant dust charge and then calculated numerically by taking the dust charge variation into account. We show that the dust charge-to-mass ratio plays an important role in the soliton properties. The soliton solutions are comprised of two branches. One branch is sub-Alfvenic and the soliton velocity is obviously smaller than the Alfven speed. The other branch is super-Alfvenic and the soliton velocity is very close to or greater than the Alfven speed. Both compressive and rarefactive solitons can exist. For the sub-Alfvenic branch, the rarefactive soliton is bell-shaped and it is much narrower than the compressive one. However, for the super-Alfvenic branch, the compressive soliton is bell-shaped and narrower, and the rarefactive one is broadened. When the charge-to-mass ratio of the dust grains is sufficiently high, the width of the rarefactive soliton, in the super-Alfvenic branch, will broaden extremely and a electron depletion will be observed. It is also shown that the bell-shaped soliton can transition to a cusped structure when the velocity is sufficiently high.

Li Yangfang [Purple Mountain Observatory, Chinese Academy of Science, Nanjing 210008 (China); Max-Planck-Institute for Extraterrestrial Physics, 85748 Garching (Germany); Wu, D. J. [Purple Mountain Observatory, Chinese Academy of Science, Nanjing 210008 (China); Morfill, G. E. [Max-Planck-Institute for Extraterrestrial Physics, 85748 Garching (Germany)

2008-08-15

33

Multicompartment kinetic model for lead. III. Lead in blood plasma and erythrocytes

Multicompartment models have been fitted to experimental data on plasma lead and blood lead concentrations of subjects studied by P.E. deSilva and one subject studied by W.I. Manton and C.R. Malloy. Nonlinear models for plasma lead vs blood lead in populations provide significantly better descriptions than does a linear model. Short-term kinetic data do not clearly resolve the precise nonlinear mechanism, however, parameters of plasma and erythrocyte distribution in a single subject were significantly different on two occasions.

Marcus, A.H.

1985-04-01

34

Solar wind plasma : kinetic properties and micro-instabilities

The kinetic properties of ions in the solar wind plasma are studied. Observations of solar wind +H and +2He by the Faraday Cup instrument component of the Solar Wind Experiment on the Wind spacecraft show that these ions ...

Kasper, Justin Christophe, 1977-

2003-01-01

35

Kinetic modelling of runaway electron avalanches in tokamak plasmas

Runaway electrons (REs) can be generated in tokamak plasmas if the accelerating force from the toroidal electric field exceeds the collisional drag force due to Coulomb collisions with the background plasma. In ITER, disruptions are expected to generate REs mainly through knock-on collisions, where enough momentum can be transferred from existing runaways to slow electrons to transport the latter beyond a critical momentum, setting off an avalanche of REs. Since knock-on runaways are usually scattered off with a significant perpendicular component of the momentum with respect to the local magnetic field direction, these particles are highly magnetized. Consequently, the momentum dynamics require a full 3-D kinetic description, since these electrons are highly sensitive to the magnetic non-uniformity of a toroidal configuration. A bounce-averaged knock-on source term is derived. The generation of REs from the combined effect of Dreicer mechanism and knock-on collision process is studied with the code LUKE, a s...

Nilsson, E; Peysson, Y; Granetz, R S; Saint-Laurent, F; Vlainic, M

2015-01-01

36

A consistent description of kinetic equation with triangle anomaly

We provide a consistent description of the kinetic equation with triangle anomaly which is compatible with the entropy principle of the second law of thermodynamics and the charge/energy-momentum conservation equations. In general an anomalous source term is necessary to ensure that the equations for the charge and energy-momentum conservation are satisfied and that the correction terms of distribution functions are compatible to these equations. The constraining equations from the entropy principle are derived for the anomaly-induced leading order corrections to the particle distribution functions. The correction terms can be determined for minimum number of unknown coefficients in one charge and two charge cases by solving the constraining equations.

Shi Pu; Jian-hua Gao; Qun Wang

2011-05-06

37

Consistent description of kinetic equation with triangle anomaly

We provide a consistent description of the kinetic equation with a triangle anomaly which is compatible with the entropy principle of the second law of thermodynamics and the charge/energy-momentum conservation equations. In general an anomalous source term is necessary to ensure that the equations for the charge and energy-momentum conservation are satisfied and that the correction terms of distribution functions are compatible to these equations. The constraining equations from the entropy principle are derived for the anomaly-induced leading order corrections to the particle distribution functions. The correction terms can be determined for the minimum number of unknown coefficients in one charge and two charge cases by solving the constraining equations.

Pu Shi; Gao Jianhua; Wang Qun [Interdisciplinary Center for Theoretical Study and Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China)

2011-05-01

38

Kinetic treatment of nonlinear magnetized plasma motions - General geometry and parallel waves

NASA Technical Reports Server (NTRS)

The expansion of kinetic equations in the limit of a strong magnetic field is presented. This gives a natural description of the motions of magnetized plasmas, which are slow compared to the particle gyroperiods and gyroradii. Although the approach is 3D, this very general result is used only to focus on the parallel propagation of nonlinear Alfven waves. The derivative nonlinear Schroedinger-like equation is obtained. Two new terms occur compared to earlier treatments, a nonlinear term proportional to the heat flux along the magnetic field line and a higher-order dispersive term. It is shown that kinetic description avoids the singularities occurring in magnetohydrodynamic or multifluid approaches, which correspond to the degenerate case of sound speeds equal to the Alfven speed, and that parallel heat fluxes cannot be neglected, not even in the case of low parallel plasma beta. A truly stationary soliton solution is derived.

Khabibrakhmanov, I. KH.; Galinskii, V. L.; Verheest, F.

1992-01-01

39

Kinetic study of ion-acoustic plasma vortices

The kinetic theory of electron plasma waves with finite orbital angular momentum has recently been introduced by Mendonca. This model shows possibility of new kind of plasma waves and instabilities. We have extended the theory to ion-acoustic plasma vortices carrying orbital angular momentum. The dispersion equation is derived under paraxial approximation which exhibits a kind of linear vortices and their Landau damping. The numerical solutions are obtained and compared with analytical results which are in good agreement. The physical interpretation of the ion-acoustic plasma vortices and their Landau resonance conditions are given for typical case of Maxwellian plasmas.

Khan, S. A. [National Centre for Physics (NCP), Quaid-i-Azam University Campus, Islamabad 45320 (Pakistan); Aman-ur-Rehman, E-mail: amansadiq@gmail.com [Pakistan Institute of Engineering and Applied Sciences (PIEAS), P.O. Nilore, Islamabad 45650 (Pakistan); Mendonca, J. T. [IPFN, Instituto Superior Téchnico, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)

2014-09-15

40

Kinetic study of ion-acoustic plasma vortices

NASA Astrophysics Data System (ADS)

The kinetic theory of electron plasma waves with finite orbital angular momentum has recently been introduced by Mendonca. This model shows possibility of new kind of plasma waves and instabilities. We have extended the theory to ion-acoustic plasma vortices carrying orbital angular momentum. The dispersion equation is derived under paraxial approximation which exhibits a kind of linear vortices and their Landau damping. The numerical solutions are obtained and compared with analytical results which are in good agreement. The physical interpretation of the ion-acoustic plasma vortices and their Landau resonance conditions are given for typical case of Maxwellian plasmas.

Khan, S. A.; Aman-ur-Rehman, Mendonca, J. T.

2014-09-01

41

Kinetic-theory approach to quark-gluon plasma oscillations

The difficulties in the unique definition of oscillations of a plasma with a non-Abelian interaction are considered. The recently formulated kinetic theory of the quark-gluon plasma in the semiclassical limit is presented and discussed with particular attention to the gluon sector of the theory. The transport equations are linearized around the global equilibrium and the chromoelectric permeability tensor is found. The dispersion relations of the plasma oscillations are discussed and the rate of oscillation damping is estimated.

Mrowczyn-acute-accentski, S.

1989-04-01

42

BOOK REVIEW: Kinetic theory of plasma waves, homogeneous plasmas

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

43

Fully Kinetic Simulations of Dense Plasma Focus Z-Pinch

NASA Astrophysics Data System (ADS)

Dense plasma focus (DPF) z pinch devices are sources of copious high energy electrons and ions, x-rays, and neutrons. The mechanisms through which these physically simple devices generate such high energy beams in a relatively short distance are not fully understood. We now have, for the first time, demonstrated a capability to model these plasmas fully kinetically, allowing us to simulate the pinch process at the particle scale. We present here the results of the initial kinetic simulations, which reproduce experimental neutron yields and high energy (MeV) beams for the first time. We present a comparison between fully kinetic, hybrid (kinetic ions/fluid electrons), and fluid simulations. Only fully kinetic simulations predict MeV-energy ions and experimental neutron yields. A frequency analysis of the electric field in the fully kinetic simulation shows plasma fluctuations near the lower hybrid frequency. This suggests the presence of lower hybrid drift instability, a possible contributor to anomalous resistivity in the plasma. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344 and supported by the Laboratory Directed Research and Development Program (11-ERD-063) at LLNL.

Schmidt, Andrea; Tang, Vincent; Welch, Dale

2012-10-01

44

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

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.

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

2012-08-29

45

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

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

46

Fully kinetic simulations of megajoule-scale dense plasma focus

Dense plasma focus (DPF) Z-pinch devices are sources of copious high energy electrons and ions, x-rays, and neutrons. Megajoule-scale DPFs can generate 10{sup 12} neutrons per pulse in deuterium gas through a combination of thermonuclear and beam-target fusion. However, the details of the neutron production are not fully understood and past optimization efforts of these devices have been largely empirical. Previously, we reported on the first fully kinetic simulations of a kilojoule-scale DPF and demonstrated that both kinetic ions and kinetic electrons are needed to reproduce experimentally observed features, such as charged-particle beam formation and anomalous resistivity. Here, we present the first fully kinetic simulation of a MegaJoule DPF, with predicted ion and neutron spectra, neutron anisotropy, neutron spot size, and time history of neutron production. The total yield predicted by the simulation is in agreement with measured values, validating the kinetic model in a second energy regime.

Schmidt, A.; Link, A.; Tang, V.; Halvorson, C.; May, M. [Lawrence Livermore National Laboratory, Livermore California 94550 (United States); Welch, D. [Voss Scientific, LLC, Albuquerque, New Mexico 87108 (United States); Meehan, B. T.; Hagen, E. C. [National Security Technologies, LLC, Las Vegas, Nevada 89030 (United States)

2014-10-15

47

Simulations of Magnetic Reconnection - Kinetic Mechanisms Underlying the Fluid Description of Ions

NASA Technical Reports Server (NTRS)

Because of its ability to transfer the energy stored in magnetic field together with the breaking of the flux freezing constraint, magnetic reconnection is considered as one of the most important phenomena in plasma physics. When it happens in a collision less environment such as the terrestrial magnetosphere, it should a priori be modelled with in the framework of kinetic physics. The evidence of kinetic features has incidentally for a long time, been shown by researchers with the help of both numerical simulations and satellite observations. However, most of our understanding of the process comes from the more intuitive fluid interpretation with simple closure hypothesis which do not include kinetic effects. To what extent are these two separate descriptions of the same phenomenon related? What is the role of kinetic effects in the averaged/fluid dynamics of reconnection? This thesis addresses these questions for the proton population in the particular case of anti parallel merging with the help of 2D Hybrid simulations. We show that one can not assume, as is usually done, that the acceleration of the proton flow is only due to the Laplace force. Our results show, for symmetric and asymmetric connection, the importance of the pressure force, opposed to the electric one on the separatrices, in the decoupling region. In the symmetric case, we emphasize the kinetic origin of this force by analyzing the proton distribution functions and explain their structure by studying the underlying particle dynamics. Protons, as individual particles, are shown to bounce in the electric potential well created by the Hall effect. The spatial divergence of this well results in a mixing in phase space responsible for the observed structure of the pressure tensor. A detailed energy budget analysis confirms the role of the pressure force for the acceleration; but, contrary to what is sometimes assumed, it also reveals that the major part of the incoming Poynting flux is transferred to the thermal energy flux rather than to the convective kinetic energy flux, although the latter is generally supposed dominant. In the symmetric case, we propose the pressure tensor to be an additional proxy of the ion decoupling region in satellite data and verify this suggestion by studying a reconnection event encountered by the Cluster spacecrafts. Finally, the last part of this thesis is devoted to the study of the kinetic structure of asymmetric tangential current sheets where connection can develop. This theoretical part consists in finding a steady state solution to the Vlasov-Maxwell system for the protons in such a configuration. We present the theory and its first confrontation to numerical tests.

Aunai, icolas; Belmont, Gerard; Smets, Roch

2012-01-01

48

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

49

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

50

Fluid description of a magnetized toroidal plasma

NASA Astrophysics Data System (ADS)

A closed system of fluid equations to describe the evolution of a weakly collisional toroidal plasma is presented. The primary physical phenomena incorporated are gyration, guiding center motion, and parallel flows of particles and heat. The systematic use of the drift ordering allows for faster dynamics than in a transport context, and in order to capture important spatial variation, no flux-surface average is taken. A notable feature of this model is a generalized bootstrap current: applying the neoclassical limit and flux-surface average to the expression for the parallel current annihilates more general terms, leaving the canonical bootstrap current as the result. Thus, the model reduces to neoclassical transport in the proper limit, but generally includes more physical effects.

Dieter, Abinadab

51

Decharging of complex plasmas: first kinetic observations.

The first experiment on the decharging of a complex plasma in microgravity conditions was conducted. After switching off the rf power, in the afterglow plasma, ions and electrons rapidly recombine and leave a cloud of charged microparticles. Because of microgravity, the particles remain suspended in the experimental chamber for a sufficiently long time, allowing precise measurements of the rest particle charge. A simple theoretical model for the decharging is proposed which agrees quite well with the experiment results and predicts the rest charge at lower gas pressures. PMID:12633365

Ivlev, A V; Kretschmer, M; Zuzic, M; Morfill, G E; Rothermel, H; Thomas, H M; Fortov, V E; Molotkov, V I; Nefedov, A P; Lipaev, A M; Petrov, O F; Baturin, Yu M; Ivanov, A I; Goree, J

2003-02-01

52

Supergravity description of boost invariant conformal plasma at strong coupling

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

53

Plasma kinetic processes in a strong d.c. magnetic field

NASA Technical Reports Server (NTRS)

Recent results in the kinetic theory of a strongly magnetized plasma are surveyed. Emphasis is on the electrostatic guiding-center plasma in two dimensions, in both the fluid and 'charged rod' descriptions. The basic kinetic description of the plasma is in terms of the statistically-distributed Fourier coefficients associated with the velocity and 'enstrophy' (charge density) fields. It is a universal tendency in such media for enstrophy to flow to shorter wavelengths but for energy to flow to longer wavelengths. A consequence of the energy flow to longer wavelengths is the generation of long-range order in the form of macroscopic vortices. These kinds of structure have been called 'convection cells' and can be extraordinarily efficient in transporting particles transverse to a magnetic field. The tendency to vortex formation can be disrupted by collisions between particles. Modifications of the Fokker-Planck equation for a plasma produced by a strong dc magnetic field are considered in both two and three dimensions.

Montgomery, D.

1976-01-01

54

NASA Technical Reports Server (NTRS)

Parametric variation of independent variables which may affect the characteristics of the NASA Lewis Bumpy Torus plasma have identified those which have a significant effect on the plasma current, ion kinetic temperature, and plasma number density, and those which do not. Empirical power-law correlations of the plasma current, and the ion kinetic temperature and number density were obtained as functions of the potential applied to the midplane electrode rings, the background neutral gas pressure, and the magnetic field strength. Additional parameters studied include the type of gas, the polarity of the midplane electrode rings (and hence the direction of the radial electric field), the mode of plasma operation, and the method of measuring the plasma number density. No significant departures from the scaling laws appear to occur at the highest ion kinetic temperatures or number densities obtained to date.

Roth, J. R.

1976-01-01

55

NASA Technical Reports Server (NTRS)

Parametric variation of independent variables which may affect the characteristics of bumpy torus plasma have identified those which have a significant effect on the plasma current, ion kinetic temperature, and plasma number density, and those which do not. Empirical power law correlations of the plasma current, and the ion kinetic temperature and number density were obtained as functions of potential applied to the midplane electrode rings, the background neutral gas pressure, and the magnetic field strength. Additional parameters studied included the type of gas, the polarity of the midplane electrode rings, the mode of plasma operation, and the method of measuring the plasma number density. No significant departures from the scaling laws appear to occur at the highest ion kinetic temperatures or number densities obtained to date.

Roth, J. R.

1976-01-01

56

Kinetic theory of nonlinear transport phenomena in complex plasmas

In contrast to the prevalent use of the phenomenological theory of transport phenomena, a number of transport properties of complex plasmas have been evaluated by using appropriate expressions, available from the kinetic theory, which are based on Boltzmann's transfer equation; in particular, the energy dependence of the electron collision frequency has been taken into account. Following the recent trend, the number and energy balance of all the constituents of the complex plasma and the charge balance on the particles is accounted for; the Ohmic loss has also been included in the energy balance of the electrons. The charging kinetics for the complex plasma comprising of uniformly dispersed dust particles, characterized by (i) uniform size and (ii) the Mathis, Rumpl, and Nordsieck power law of size distribution has been developed. Using appropriate expressions for the transport parameters based on the kinetic theory, the system of equations has been solved to investigate the parametric dependence of the complex plasma transport properties on the applied electric field and other plasma parameters; the results are graphically illustrated.

Mishra, S. K. [Institute for Plasma Research (IPR), Gandhinagar 382428 (India); Sodha, M. S. [Centre for Energy Studies (CES), Indian Institute of Technology Delhi (IITD), New Delhi 110016 (India)

2013-03-15

57

Complexity reduction of collisional-radiative kinetics for atomic plasma

Thermal non-equilibrium processes in partially ionized plasmas can be most accurately modeled by collisional-radiative kinetics. This level of detail is required for an accurate prediction of the plasma. However, the resultant system of equations can be prohibitively large, making multi-dimensional and unsteady simulations of non-equilibrium radiating plasma particularly challenging. In this paper, we present a scheme for model reduction of the collisional-radiative kinetics, by combining energy levels into groups and deriving the corresponding macroscopic rates for all transitions. Although level-grouping is a standard approach to this type of problem, we provide here a mechanism for achieving higher-order accuracy by accounting for the level distribution within a group. The accuracy and benefits of the scheme are demonstrated for the generic case of atomic hydrogen by comparison with the complete solution of the master rate equations and other methods.

Le, Hai P. [ERC Inc., Edwards AFB, California 93524 (United States)] [ERC Inc., Edwards AFB, California 93524 (United States); Karagozian, Ann R. [Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, California 90095 (United States)] [Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, California 90095 (United States); Cambier, Jean-Luc [Air Force Research Laboratory, Edwards AFB, California 93524 (United States)] [Air Force Research Laboratory, Edwards AFB, California 93524 (United States)

2013-12-15

58

The kinetic description of relativistic plasmas in the presence of time-varying and spatially non-uniform electromagnetic (EM) fields is a fundamental theoretical issue both in astrophysics and plasma physics. This refers, in particular, to the treatment of collisionless and strongly-magnetized plasmas in the presence of intense radiation sources. In this paper, the problem is investigated in the framework of a covariant gyrokinetic treatment for Vlasov–Maxwell equilibria. The existence of a new class of kinetic equilibria is pointed out, which occur for spatially-symmetric systems. These equilibria are shown to exist in the presence of non-uniform background EM fields and curved space-time. In the non-relativistic limit, this feature permits the determination of kinetic equilibria even for plasmas in which particle energy is not conserved due to the occurrence of explicitly time-dependent EM fields. Finally, absolute stability criteria are established which apply in the case of infinitesimal symmetric perturbations that can be either externally or internally produced.

Cremaschini, Claudio, E-mail: claudiocremaschini@gmail.com; Stuchlík, Zden?k [Faculty of Philosophy and Science, Institute of Physics, Silesian University in Opava, Bezru?ovo nám.13, CZ-74601 Opava (Czech Republic)] [Faculty of Philosophy and Science, Institute of Physics, Silesian University in Opava, Bezru?ovo nám.13, CZ-74601 Opava (Czech Republic); Tessarotto, Massimo [Faculty of Philosophy and Science, Institute of Physics, Silesian University in Opava, Bezru?ovo nám.13, CZ-74601 Opava (Czech Republic) [Faculty of Philosophy and Science, Institute of Physics, Silesian University in Opava, Bezru?ovo nám.13, CZ-74601 Opava (Czech Republic); Department of Mathematics and Geosciences, University of Trieste, Via Valerio 12, 34127 Trieste (Italy)

2014-03-15

59

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

Complete Spectrum of Kinetic Eigenmodes for Plasma Oscillations in a Weakly Collisional Plasma C. S. These eigenmodes, which are smooth and compose a complete discrete spectrum, play the same role for weakly, a broad and continuous spectrum of CaseVan Kampen modes is excited. The Landau-damped solutions emerge

Ng, Chung-Sang

60

Kinetic theory of weak turbulence in plasmas.

From the nonlinear Vlasov equation, a nonlinear turbulence scattering term is found to describe stochastic dissipation on a time scale longer than the turbulence correlation time. The evolution of the plasma distribution is determined by the well-understood unperturbed motion of charged particles, with the effects of the fluctuating part of fields described by the turbulence scattering term. In the present framework, one can identify various important physics, from the linear and quasilinear regimes to the nonlinear regime, in particular, the connections between the widely used Kadomtsev-Pogutse equation [B. B. Kadomtsev and O. P. Pogutse, in Reviews of Plasma Physics, edited by M. A. Leontovich (Consultants Bureau, New York, 1970), pp. 368-387] and the Frieman-Chen equation [Frieman and Chen, Phys. Fluids 25, 502 (1982)]. The nonlinear scattering term indicates the Onsager symmetry relation of turbulent transport and a nonlinear frequency or k spectrum shift of a resonantly excited wave. PMID:23848785

Wang, Shaojie

2013-06-01

61

Macroscopic Quantum Electrodynamics of a Plasma Model: Derivation of the Vlasov Kinetics

Macroscopic Quantum Electrodynamics of a Plasma Model: Derivation of the Vlasov Kinetics derive the largeÂscale Vlasov kinetics of a plasma model from its underlying quantum electrodynamics with the extraction of the largeÂscale kinetics of a plasma model from its underlying quantum electrodynamics

62

Collisionless energy-independent kinetic equilibria in axisymmetric magnetized plasmas.

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. PMID:24125369

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

2013-09-01

63

The problem of formulating a kinetic treatment for quasi-stationary collisionless plasmas in axisymmetric systems subject to the possibly independent presence of local strong velocity-shear and supersonic rotation velocities is posed. The theory is developed in the framework of the Vlasov-Maxwell description for multi-species non-relativistic plasmas. Applications to astrophysical accretion discs arising around compact objects and to plasmas in laboratory devices are considered. Explicit solutions for the equilibrium kinetic distribution function (KDF) are constructed based on the identification of the relevant particle adiabatic invariants. These are shown to be expressed in terms of generalized non-isotropic Gaussian distributions. A suitable perturbative theory is then developed which allows for the treatment of non-uniform strong velocity-shear/supersonic plasmas. This yields a series representation for the equilibrium KDF in which the leading-order term depends on both a finite set of fluid fields as well as on the gradients of an appropriate rotational frequency. Constitutive equations for the fluid number density, flow velocity, and pressure tensor are explicitly calculated. As a notable outcome, the discovery of a new mechanism for generating temperature and pressure anisotropies is pointed out, which represents a characteristic feature of plasmas considered here. This is shown to arise as a consequence of the canonical momentum conservation and to contribute to the occurrence of temperature anisotropy in combination with the adiabatic conservation of the particle magnetic moment. The physical relevance of the result and the implications of the kinetic solution for the self-generation of quasi-stationary electrostatic and magnetic fields through a kinetic dynamo are discussed.

Cremaschini, Claudio; Stuchlík, Zden?k [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezru?ovo nám.13, CZ-74601 Opava (Czech Republic)] [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezru?ovo nám.13, CZ-74601 Opava (Czech Republic); Tessarotto, Massimo [Department of Mathematics and Geosciences, University of Trieste, Via Valerio 12, 34127 Trieste (Italy)] [Department of Mathematics and Geosciences, University of Trieste, Via Valerio 12, 34127 Trieste (Italy)

2013-05-15

64

Kinetic description of fermion production in the oscillator representation

We investigate the fermion creation in quantum kinetic theory by applying ``oscillator representation'' approach, which was earlier developed for bosonic systems. We show that in some particular cases (Yukawa-like interaction, fixed direction of external vector field) resulting Kinetic Equation (KE) reduces to KE obtained by time-dependent Bogoliubov transformation method. We conclude ``oscillator representation'' approach to be more universal for the derivation of quantum transport equations in strong space-homogeneous time-dependent fields. We discuss some possible applications of obtained KE to cosmology and particle production in strong laser fields.

V. N. Pervushin; V. V. Skokov

2006-11-25

65

Kinetic Alfvén solitary and rogue waves in superthermal plasmas

We investigate the small but finite amplitude solitary Kinetic Alfvén waves (KAWs) in low ? plasmas with superthermal electrons modeled by a kappa-type distribution. A nonlinear Korteweg-de Vries (KdV) equation describing the evolution of KAWs is derived by using the standard reductive perturbation method. Examining the dependence of the nonlinear and dispersion coefficients of the KdV equation on the superthermal parameter ?, plasma ?, and obliqueness of propagation, we show that these parameters may change substantially the shape and size of solitary KAW pulses. Only sub-Alfvénic, compressive solitons are supported. We then extend the study to examine kinetic Alfvén rogue waves by deriving a nonlinear Schrödinger equation from the KdV equation. Rational solutions that form rogue wave envelopes are obtained. We examine how the behavior of rogue waves depends on the plasma parameters in question, finding that the rogue envelopes are lowered with increasing electron superthermality whereas the opposite is true when the plasma ? increases. The findings of this study may find applications to low ? plasmas in astrophysical environments where particles are superthermally distributed.

Bains, A. S.; Li, Bo, E-mail: bbl@sdu.edu.cn; Xia, Li-Dong [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, School of Space Science and Physics, Shandong University at Weihai, 264209 Weihai (China)] [Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, School of Space Science and Physics, Shandong University at Weihai, 264209 Weihai (China)

2014-03-15

66

Advances in petascale kinetic plasma simulation with VPIC and Roadrunner

NASA Astrophysics Data System (ADS)

VPIC [1], a first-principles 3d electromagnetic charge-conserving relativistic kinetic particle-in-cell code, was recently adapted to run on Los Alamos's Roadrunner [2], the first supercomputer to break a petaflop (1015 floating point operations per second) in the TOP500 supercomputer performance rankings. [3] We summarize VPIC's modeling capabilities, VPIC's optimization techniques and Roadrunner's computational characteristics. We 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, modeling short-pulse laser GeV ion acceleration and modeling reconnection in space and laboratory plasmas.

Bowers, K. J.; Albright, B. J.; Yin, L.; Daughton, W.; Roytershteyn, V.; Bergen, B.; Kwan, T. J. T.

2009-07-01

67

Species separation and kinetic effects in collisional plasma shocks

The properties of collisional shock waves propagating in uniform plasmas are studied with ion-kinetic calculations, in both slab and spherical geometry and for the case of one and two ion species. Despite the presence of an electric field at the shock front—and in contrast to the case where an interface is initially present [C. Bellei et al., Phys. Plasmas 20, 044702 (2013)]—essentially no ion reflection at the shock front is observed due to collisions, with a probability of reflection ?10{sup ?4} for the cases presented. A kinetic two-ion-species spherical convergent shock is studied in detail and compared against an average-species calculation, confirming effects of species separation and differential heating of the ion species at the shock front. The effect of different ion temperatures on the DT and D{sup 3}He fusion reactivity is discussed in the fluid limit and is estimated to be moderately important.

Bellei, C., E-mail: bellei1@llnl.gov; Wilks, S. C.; Amendt, P. A. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 (United States); Rinderknecht, H.; Zylstra, A.; Rosenberg, M.; Sio, H.; Li, C. K.; Petrasso, R. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)] [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2014-05-15

68

Ion kinetic energy distributions in laser-induced plasma

NASA Astrophysics Data System (ADS)

Studies of ion emissions from laser-induced plasmas (LIPs) provide insights into the hydrodynamic expansion of the plume. Investigations of the kinetic energy distributions (KEDs) of ionized species for various experimental conditions are vital for a fundamental understanding of the formation and expansion dynamics of plasma. This knowledge, in turn, leads to promising improvements in LIP-based technological applications. This article aims to review some of the dominating mechanisms concerning ion emission kinetics during laser-surface interactions from a basic point of view. The diagnostic methods for ion KEDs are roughly classified. Interesting features of ion KEDs and their angular distributions, as well as the dependence on laser beam properties, ambient surroundings, and target properties, are summarized.

Wang, Xiaohua; Zhang, Shudi; Cheng, Xiaoling; Zhu, Eryi; Hang, Wei; Huang, Benli

2014-09-01

69

Transition of electron kinetics in weakly magnetized inductively coupled plasmas

NASA Astrophysics Data System (ADS)

Transition of the electron kinetics from nonlocal to local regime was studied in weakly magnetized solenoidal inductively coupled plasma from the measurement of the electron energy probability function (EEPF). Without DC magnetic field, the discharge property was governed by nonlocal electron kinetics at low gas pressure. The electron temperatures were almost same in radial position, and the EEPFs in total electron energy scale were radially coincided. However, when the DC magnetic field was applied, radial non-coincidence of the EEPFs in total electron energy scale was observed. The electrons were cooled at the discharge center where the electron heating is absent, while the electron temperature was rarely changed at the discharge boundary with the magnetic field. These changes show the transition from nonlocal to local electron kinetics and the transition is occurred when the electron gyration diameter was smaller than the skin depth. The nonlocal to local transition point almost coincided with the calculation results by using nonlocal parameter and collision parameter.

Kim, Jin-Yong; Lee, Hyo-Chang; Kim, Young-Do; Kim, Young-Cheol; Chung, Chin-Wook

2013-10-01

70

Transition of electron kinetics in weakly magnetized inductively coupled plasmas

Transition of the electron kinetics from nonlocal to local regime was studied in weakly magnetized solenoidal inductively coupled plasma from the measurement of the electron energy probability function (EEPF). Without DC magnetic field, the discharge property was governed by nonlocal electron kinetics at low gas pressure. The electron temperatures were almost same in radial position, and the EEPFs in total electron energy scale were radially coincided. However, when the DC magnetic field was applied, radial non-coincidence of the EEPFs in total electron energy scale was observed. The electrons were cooled at the discharge center where the electron heating is absent, while the electron temperature was rarely changed at the discharge boundary with the magnetic field. These changes show the transition from nonlocal to local electron kinetics and the transition is occurred when the electron gyration diameter was smaller than the skin depth. The nonlocal to local transition point almost coincided with the calculation results by using nonlocal parameter and collision parameter.

Kim, Jin-Yong; Lee, Hyo-Chang; Kim, Young-Do; Chung, Chin-Wook [Department of Electrical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)] [Department of Electrical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of); Kim, Young-Cheol [Department of Nanoscale Semiconductor Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)] [Department of Nanoscale Semiconductor Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)

2013-10-15

71

On bias of kinetic temperature measurements in complex plasmas

The kinetic temperature in complex plasmas is often measured using particle tracking velocimetry. Here, we introduce a criterion which minimizes the probability of faulty tracking of particles with normally distributed random displacements in consecutive frames. Faulty particle tracking results in a measurement bias of the deduced velocity distribution function and hence the deduced kinetic temperature. For particles with a normal velocity distribution function, mistracking biases the obtained velocity distribution function towards small velocities at the expense of large velocities, i.e., the inferred velocity distribution is more peaked and its tail is less pronounced. The kinetic temperature is therefore systematically underestimated in measurements. We give a prescription to mitigate this type of error.

Kantor, M. [Association Euratom-Max-Planck-Institut für Plasmaphysik, D-85748 Garching bei München (Germany) [Association Euratom-Max-Planck-Institut für Plasmaphysik, D-85748 Garching bei München (Germany); Association Euratom-FOM Institute DIFFER, 3430 BE Nieuwegein (Netherlands); Ioffe Institute, RAS, St. Petersburg 194021 (Russian Federation); Moseev, D., E-mail: dmitry.moseev@ipp.mpg.de [Association Euratom-Max-Planck-Institut für Plasmaphysik, D-85748 Garching bei München (Germany); Association Euratom-FOM Institute DIFFER, 3430 BE Nieuwegein (Netherlands); Salewski, M. [Association Euratom-DTU, Department of Physics, Technical University of Denmark, DTU Ris o Campus, DK-4000 Roskilde (Denmark)] [Association Euratom-DTU, Department of Physics, Technical University of Denmark, DTU Ris o Campus, DK-4000 Roskilde (Denmark)

2014-02-15

72

Plasma kinetics in man of epicatechin from black chocolate

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

73

Plasma transport induced by kinetic Alfven wave turbulence

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

74

NASA Technical Reports Server (NTRS)

Based on a theoretical model of the propagation of electromagnetic waves through a hypersonically induced plasma, it has been demonstrated that the classical radiofrequency communications blackout that is experienced during atmospheric reentry can be mitigated through the appropriate control of an external magnetic field of nominal magnitude. The model is based on the kinetic equation treatment of Vlasov and involves an analytical solution for the electric and magnetic fields within the plasma allowing for a description of the attendant transmission, reflection and absorption coefficients. The ability to transmit through the magnetized plasma is due to the magnetic windows that are created within the plasma via the well-known whistler modes of propagation. The case of 2 GHz transmission through a re-entry plasma is considered. The coefficients are found to be highly sensitive to the prevailing electron density and will thus require a dynamic control mechanism to vary the magnetic field as the plasma evolves through the re-entry phase.

Manning, Robert M.

2009-01-01

75

Photon kinetic modeling of laser pulse propagation in underdense plasma A. J. W. Reitsma

Photon kinetic modeling of laser pulse propagation in underdense plasma A. J. W. Reitsma Department to the interaction of laser pulses with underdense plasma and the transfer of energy and momentum between the laser pulse and the plasma is described in photon kinetic terms. A comparison is made between a one

Strathclyde, University of

76

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

77

Kinetic phenomena in charged particle transport in gases and plasmas

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

78

The weak collisionality typical of turbulence in many diffuse astrophysical plasmas invalidates an MHD description of the turbulent dynamics, motivating the development of a more comprehensive theory of kinetic turbulence. In particular, a kinetic approach is essential for the investigation of the physical mechanisms responsible for the dissipation of astrophysical turbulence and the resulting heating of the plasma. This chapter reviews the limitations of MHD turbulence theory and explains how kinetic considerations may be incorporated to obtain a kinetic theory for astrophysical plasma turbulence. Key questions about the nature of kinetic turbulence that drive current research efforts are identified. A comprehensive model of the kinetic turbulent cascade is presented, with a detailed discussion of each component of the model and a review of supporting and conflicting theoretical, numerical, and observational evidence.

Howes, Gregory G

2015-01-01

79

NASA Astrophysics Data System (ADS)

The weak collisionality typical of turbulence in many diffuse astrophysical plasmas invalidates an MHD description of the turbulent dynamics, motivating the development of a more comprehensive theory of kinetic turbulence. In particular, a kinetic approach is essential for the investigation of the physical mechanisms responsible for the dissipation of astrophysical turbulence and the resulting heating of the plasma. This chapter reviews the limitations of MHD turbulence theory and explains how kinetic considerations may be incorporated to obtain a kinetic theory for astrophysical plasma turbulence. Key questions about the nature of kinetic turbulence that drive current research efforts are identified. A comprehensive model of the kinetic turbulent cascade is presented, with a detailed discussion of each component of the model and a review of supporting and conflicting theoretical, numerical, and observational evidence.

Howes, Gregory G.

80

Kinetic Description of a Finite Temperature Meson Gas

A transport model based on the mean free path approach for an interacting meson system at finite temperatures is discussed. A transition to a quark gluon plasma is included within the framework of the bag model. We discuss some calculations for a pure meson gas where the Hagedorn limiting temperature is reproduced when including the experimentally observed resonances. Next we include the possibility for a QGP formation based on the MIT bag model. The results obtained compare very well with Lattice QCD calculations. In particular the cross over to the QGP at about 175 MeV temperature is nicely reproduced.

Zhi Guang Tan; Dai-Mei Zhou; S. Terranova; A. Bonasera

2006-06-28

81

Fluid description of multi-component solar partially ionized plasma

We derive self-consistent formalism for the description of multi-component partially ionized solar plasma, by means of the coupled equations for the charged and neutral components for an arbitrary number of chemical species, and the radiation field. All approximations and assumptions are carefully considered. Generalized Ohm's law is derived for the single-fluid and two-fluid formalism. Our approach is analytical with some order-of-magnitude support calculations. After general equations are developed, we particularize to some frequently considered cases as for the interaction of matter and radiation.

Khomenko, E., E-mail: khomenko@iac.es; Collados, M.; Vitas, N. [Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife (Spain); Departamento de Astrofísica, Universidad de La Laguna, 38205 La Laguna, Tenerife (Spain); Díaz, A. [Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)

2014-09-15

82

Fluid description of multi-component solar partially ionized plasma

NASA Astrophysics Data System (ADS)

We derive self-consistent formalism for the description of multi-component partially ionized solar plasma, by means of the coupled equations for the charged and neutral components for an arbitrary number of chemical species, and the radiation field. All approximations and assumptions are carefully considered. Generalized Ohm's law is derived for the single-fluid and two-fluid formalism. Our approach is analytical with some order-of-magnitude support calculations. After general equations are developed, we particularize to some frequently considered cases as for the interaction of matter and radiation.

Khomenko, E.; Collados, M.; Díaz, A.; Vitas, N.

2014-09-01

83

Vibrational and chemical kinetics in plasma of CO containing gases

NASA Astrophysics Data System (ADS)

This paper discusses the experimental results pointing to the efficient channel of the CO vibrational to the C2 electron energy transfer. The radiation spectra of e3?, C1?, D1? states of C2 molecules were investigated and the relation of their kinetics to vibrational excitation of CO (X1?, v) molecules in the He-CO-O2 gas discharge plasma was discussed. The rate constant for VE- process CO (X1?, v>= 25) + C2 ? CO(X1?) + C2(D1?u), was estimated, and kvE ~ 10-14 cm3/c.

Grigorian, G. M.; Cenian, A.

2014-08-01

84

Kinetic description of electron beams in the solar chromosphere

NASA Technical Reports Server (NTRS)

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.

Gomez, Daniel O.; Mauas, Pablo J.

1992-01-01

85

Kinetic description of electron beams in the solar chromosphere

NASA Astrophysics Data System (ADS)

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.

Gomez, Daniel O.; Mauas, Pablo J.

1992-10-01

86

Ultrahigh performance three-dimensional electromagnetic relativistic kinetic plasma simulation

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

87

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 a flexible and powerful tool for incorporating complex chemical kinetics into simulations of fluid dynamics. The package consists of two major software components: an Interpreter and a Gas-Phase Subroutine Library. The Interpreter is a program that reads a symbolic description of an elementary, user-specified chemical reaction mechanism. One output from the Interpreter is a data file that forms a link to the Gas-Phase Subroutine Library. This library is a collection of about 100 highly modular FORTRAN subroutines that may be called to return information on equations of state, thermodynamic properties, and chemical production rates. CHEMKIN-III includes capabilities for treating multi-fluid plasma systems, that are not in thermal equilibrium. These new capabilities allow researchers to describe chemistry systems that are characterized by more than one temperature, in which reactions may depend on temperatures associated with different species; i.e. reactions may be driven by collisions with electrons, ions, or charge-neutral species. These new features have been implemented in such a way as to require little or no changes to CHEMKIN implementation for systems in thermal equilibrium, where all species share the same gas temperature. CHEMKIN-III now has the capability to handle weakly ionized plasma chemistry, especially for application related to advanced semiconductor processing.

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

1996-05-01

88

Kinetic Theory of Plasma Adiabatic Major Radius Compression in Tokamaks

A kinetic approach is developed to understand the individual charged particle behavior as well as plasma macro parameters (temperature, density, etc.) during the adiabatic R-compression in a tokamak. The perpendicular electric field from Ohm's law at zero resistivity E = -v{sub E}{times}B/c is made use of to obtain the equation for particle velocity evolution in order to describe the particle motion during the R-compression. Expressions for both passing and trapped particle energy and pitch angle change are obtained for a plasma with high aspect ratio and circular magnetic surfaces. The particle behavior near the trapped passing boundary during the compression is also studied to understand the shift induced loss of alpha particles produced by D-T fusion reactions in Tokamak Fusion Test Reactor experiments. Qualitative agreement is obtained with the experiments. Solving the drift kinetic equation in the collisional case, i.e., when the collisional frequency of given species exceeds the inverse compression time, we obtain that the temperature and the density evolution is reduced to the MHD results T {approximately} R{super -4/3} and n {approximately} R{super -2}, respectively. In the opposite case, the collisional frequency of given species is smaller than the inverse compression time, the longitudinal component of the temperature evolve like R{super -2} and perpendicular component of the temperature is R{super -1}. The effect of toroidicity is negligible in both cases.

A.N. Romannikov; E.A. Azizov; H.W. Herrmann; M.V. Gorelenkova; N.N. Gorelenkov

1997-10-01

89

Unified description of linear screening in dense plasmas

NASA Astrophysics Data System (ADS)

Electron screening of ions is among the most fundamental properties of plasmas, determining the effective ionic interactions that impact all properties of a plasma. With the development of new experimental facilities that probe high-energy-density physics regimes ranging from warm dense matter to hot dense matter, a unified framework for describing dense plasma screening has become essential. Such a unified framework is presented here based on finite-temperature orbital-free density functional theory, including gradient corrections and exchange-correlation effects. We find a new analytic pair potential for the ion-ion interaction that incorporates moderate electronic coupling, quantum degeneracy, gradient corrections to the free energy, and finite temperatures. This potential can be used in large-scale "classical" molecular dynamics simulations, as well as in simpler theoretical models (e.g., integral equations and Monte Carlo), with no additional computational complexity. The new potential theoretically connects limits of Debye-Hückel-Yukawa, Lindhard, Thomas-Fermi, and Bohmian quantum hydrodynamics descriptions. Based on this new potential, we predict ionic static structure factors that can be validated using x-ray Thomson scattering data.

Stanton, L. G.; Murillo, M. S.

2015-03-01

90

Electromagnetic effects of kinetic geodesic acoustic mode in tokamak plasmas

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

91

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

'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

92

Kinetic plasma instabilities due to charge exchange and elastic collisions

NASA Astrophysics Data System (ADS)

With numerical particle-in-cell simulations, we study kinetic plasma instabilities induced by collisions between plasma particles and neutral background in magnetized drifting plasmas. We consider the role of charge exchange as well as elastic collisions in the evolution of the system. Charge exchange collisions can give rise to velocity distributions in the form of loss- cone or ring shaped distributions that can become linearly unstable. Elastic collisions also lead to the instability, but in this case the principal mechanism may be attributed to the generalized two-stream instability. We investigate the growth rates and saturation levels for instabilities associated with these collisional processes, and find higher saturation levels and stronger fluctuations for the case with charge exchange collisions. Characteristics of the studied system are similar to the E- and F-regions of the Earth's ionosphere. Our results are relevant for explaining some of the low frequency oscillations observed in the lower parts of the Earth's ionosphere, and are also relevant for some laboratory experiments.

Horký, M.; Miloch, W. J.

2015-03-01

93

Fluid description of ion dynamics in a toroidally confined plasma

NASA Astrophysics Data System (ADS)

Fluid equations describing ion dynamics in a toroidally confined plasma at low collision frequency are derived. The principle motivation is to present a framework for incorporating basic neoclassical effects into a fluid theory. The ions are assumed to be magnetized in the sense that relevant scale lengths are much longer than the ion gyroradius, and time scales of interest are assumed long compared to the ion bounce time. These assumptions are consistent with, for example, the evolution of unstable magnetic islands, as well as conventional transport. A special case of the present description is the quasistatic, axisymmetric state with nearly uniform pressure and density on flux surfaces. In that case the equations reproduce the radial ion heat transport predicted by neoclassical transport theory. The essential feature of our derivation is its emphasis on heat flow in the direction of the magnetic field.

Dieter, Abinadab; Hazeltine, R. D.

2005-05-01

94

Effects of Kinetic Processes in Shaping Io's Global Plasma Environment: A 3D Hybrid Model

NASA Technical Reports Server (NTRS)

The global dynamics of the ionized and neutral components in the environment of Io plays an important role in the interaction of Jupiter's corotating magnetospheric plasma with Io. The stationary simulation of this problem was done in the MHD and the electrodynamics approaches. One of the main significant results from the simplified two-fluid model simulations was a production of the structure of the double-peak in the magnetic field signature of the I0 flyby that could not be explained by standard MHD models. In this paper, we develop a method of kinetic ion simulation. This method employs the fluid description for electrons and neutrals whereas for ions multilevel, drift-kinetic and particle, approaches are used. We also take into account charge-exchange and photoionization processes. Our model provides much more accurate description for ion dynamics and allows us to take into account the realistic anisotropic ion distribution that cannot be done in fluid simulations. The first results of such simulation of the dynamics of ions in the Io's environment are discussed in this paper.

Lipatov, Alexander S.; Combi, Michael R.

2004-01-01

95

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

96

Astrophysical plasmas in the surrounding of compact objects and subject to intense gravitational and electromagnetic fields are believed to give rise to relativistic regimes. Theoretical and observational evidences suggest that magnetized plasmas of this type are collisionless and can persist for long times (e.g., with respect to a distant observer, coordinate, time), while exhibiting geometrical structures characterized by the absence of well-defined spatial symmetries. In this paper, the problem is posed whether such configurations can correspond to some kind of kinetic equilibrium. The issue is addressed from a theoretical perspective in the framework of a covariant Vlasov statistical description, which relies on the method of invariants. For this purpose, a systematic covariant variational formulation of gyrokinetic theory is developed, which holds without requiring any symmetry condition on the background fields. As a result, an asymptotic representation of the relativistic particle magnetic moment is obtained from its formal exact solution, in terms of a suitably defined invariant series expansion parameter (perturbative representation). On such a basis, it is shown that spatially non-symmetric kinetic equilibria can actually be determined, an example being provided by Gaussian-like distributions. As an application, the physical mechanisms related to the occurrence of a non-vanishing equilibrium fluid 4-flow are investigated.

Cremaschini, Claudio, E-mail: claudiocremaschini@gmail.com; Stuchlík, Zden?k [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezru?ovo nám.13, CZ-74601 Opava (Czech Republic)] [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezru?ovo nám.13, CZ-74601 Opava (Czech Republic); Tessarotto, Massimo [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezru?ovo nám.13, CZ-74601 Opava (Czech Republic) [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezru?ovo nám.13, CZ-74601 Opava (Czech Republic); Department of Mathematics and Geosciences, University of Trieste, Via Valerio 12, 34127 Trieste (Italy)

2014-05-15

97

Advances in petascale kinetic plasma simulation with VPIC and Roadrunner

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

98

D-Dimensional Radiative Plasma: A Kinetic Approach

The covariant kinetic approach for the radiative plasma, a mixture of a relativistic moving gas plus radiation quanta (photons, neutrinos, or gravitons) is generalized to D spatial dimensions. The operational and physical meaning of Eckart's temperature is reexamined and the D-dimensional expressions for the transport coefficients (heat conduction, bulk and shear viscosity) are explicitly evaluated to first order in the mean free time of the radiation quanta. Weinberg's conclusion that the mixture behaves like a relativistic imperfect simple fluid (in Eckart's formulation) depends neither on the number of spatial dimensions nor on the details of the collisional term. The case of Thomson scaterring is studied in detail, and some consequences for higher dimensional cosmologies are also discussed.

A. Maia Jr.; J. A. S. Lima

1996-10-31

99

Air plasma kinetics under the influence of sprites

NASA Astrophysics Data System (ADS)

A full time-dependent kinetic study is presented for the main microscopic collisional and radiative processes underlying the optical flashes associated with an impulsive (? = 5 µs) discharge in the form of a single sprite streamer passing through an air region of the mesosphere at three different altitudes (63, 68 and 78 km). The kinetic formalism developed includes the coupling of the rate equations of each of the different species considered (electrons, ions, atoms and molecules) with the Boltzmann transport equation so that, in this way, all the kinetics is self-consistent, although, in the present approach, the electrodynamics (no Poisson equation is considered) is not coupled. The chemical model set up for air plasmas includes more than 75 species and almost 500 reactions. In addition, a complete set of reactions (more than 110) has been considered to take into account the possible impact of including H2O (humid chemistry) in the generated air plasmas. This study also considers the vibrational kinetics of N2 and CO2 and explicitly evaluates the optical emissions associated with a number of excited states of N2, O2, O in the visible, CO2 in the infrared (IR) and ultraviolet (UV) emissions of sprite streamers due to the N2 Lyman-Birge-Hopfield (LBH) and the NO-? band systems. All the calculations are conducted for midnight conditions in mid-latitude regions (+38°N) and 0° longitude, using as initial values for the neutral species those provided by the latest version of the Whole Atmosphere Community Climate Model (WACCM). According to our calculations, the impact of 4 ppm of H2O is only slightly visible in O_{3}^{-} at 68 and 78 km while it strongly affects the behaviour of the anion CO_{4}^{-} at all the altitudes investigated. The local enhancement of NOx predicted by the present model varies with the altitude. At 68 km, the concentrations of NO and NO2 increase by about one order of magnitude while that of NO3 exhibits a remarkable growth of up to almost three orders of magnitude. The variation of the O3 density predicted by the model in the sprite streamer head is negligible in all the altitudes investigated. The analysis of the time dependence of the electron distribution function (EDF) in the sprite plasma during the pulse reveals that the EDF transient is quite fast, reaching its 'steady' values during the pulse in less than 100 ns (much shorter than streamer head lifetimes). In addition, the calculated EDF during the pulse and in the afterglow is far from being Maxwellian, especially for energetic electrons (with ? > 30 eV). Finally, the evaluation of the mid-latitude nighttime electrical conductivity of air plasmas under the influence of a single sprite event reveals an increase of up to four orders of magnitude (at 68 km) above its measured background level of 10^{-11}\\,\\mho\\,cm^{-1} at an altitude of ~70 km. This sudden increase in the electrical conductivity lasts for 100 ms (at 68 km), being shorter (~1 ms) and longer (1 s) at 63 km and 78 km, respectively. The total power delivered by the streamer head of a single sprite event has been estimated to be approximately 1677 W (at 78 km), 230 kW (at 68 km) and 78 MW (at 63 km).

Gordillo-Vázquez, F. J.

2008-12-01

100

Air Plasma Kinetics Under the Influence of Sprites

NASA Astrophysics Data System (ADS)

A full time-dependent kinetic study is presented for the main microscopic collisional and radiative processes underlying the optical flashes associated to an impulsive (t = 5 ms) discharge in the form of a single sprite streamer going through an air region of the mesosphere at three different altitudes (63 km, 68 km and 78 km). The kinetic formalism developed includes the coupling of the rate equations of each of the different species considered (electrons, ions, atoms and molecules) with the Boltzmann transport equation so that, in this way, all the kinetics is self-consistent, although, in the present approach, the electrodynamics (no Poisson equation is considered) is not coupled. The chemical model set up for air plasmas includes more than 75 species and almost 500 reactions. In addition, a complete set of reactions (more than 110) has been considered to take into account the possible impact of including H2O (humid chemistry) in the generated air plasmas. This study also considers the vibrational kinetics of N2 and CO2, and explicitly evaluates the optical emissions associated to a number of excited states of N2, O2, O in the visible, CO2 in the infrared (IR) and ultraviolet (UV) emissions of sprite streamers due to the N2 Lyman-Birge-Hopfield (LBH) and the NO-? band systems. All the calculations are conducted for midnight conditions in mid- latitude regions (+ 38°), and 0° longitude, using as initial values for the neutral species those provided by the latest version of the Whole Atmosphere Community Climate Model (WACCM). According to our calculations, the impact of 4 ppm of H2O is only slightly visible in O3- at 68 km and 78 km while it strongly affects the behaviour of the anion CO4- at all the altitudes investigated. The local enhancement of NOX predicted by the present model varies with the altitude. At 68 km, the concentrations of NO and NO2 increase in about one order of magnitude while that of NO3 exhibits a remarkable growth of up to almost three orders of magnitude. The variation of the O3 density predicted by the model in the sprite streamer head is negligible in all the altitudes investigated. The analysis of the time dependence of the electron distribution function (EDF) in the sprite plasma during the pulse reveals that the EDF transient is quite fast, reaching its "steady" values during the pulse in less than 100 nanoseconds (much shorter than streamer head lifetimes). In addition, the calculated EDF during the pulse and in the afterglow is far from being Maxwellian, especially for energetic electrons (with ? > 30 eV). Finally, the evaluation of the mid-latitude nighttime electrical conductivity of air plasmas under the influence of a single sprite event reveals an increase of up to four orders of magnitude (at 68 km) above its measured background level of 10-11 mho/cm at an altitude of ~ 70 km. This sudden increase of the electrical conductivity lasts for 100 ms (at 68 km), being shorter (~ 1 ms) and longer (1 s) at 63 km and 78 km, respectively. The total power delivered by the streamer head of a single sprite event has been estimated to be approximately 1677 W (at 78 km), 230 kW (at 68 km) and 78 MW (at 63 km).

Gordillo-Vazquez, F. J.

2008-12-01

101

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

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

102

NASA Astrophysics Data System (ADS)

Recent progress in several related research areas such as first-principles electronic-structure calculations of atoms and diatomic molecules, theory of elementary processes, kinetics, and numerical engineering, and also continued exponential growth in computational resources enhanced by recent advances in massively parallel computing have opened the possibility of directly designing kinetics mechanisms to describe chemical processes and light emission in such complex media as nonequilibrium plasmas and reacting gases. It is important that plasma and combustion kinetics can be described in the framework of this direct approach to a sufficiently high accuracy, which makes it an independent predictive research tool complementary to experimental techniques. This paper demonstrates the capabilities of the first-principles based approach to develop kinetic mechanisms. Two examples are discussed in detail: (1) the mechanism of hydrocarbon fuel combustion at high temperatures and (2) light emission in non-thermal glow discharge plasma of metal halides; special attention is paid to a comparison of the results obtained at every level of system description with the appropriate experimental data. In house software tools that can be used in such multilevel theoretical works are discussed as well.

Astapenko, Valerie; Bagatur'yants, Alexander; Chernishova, Irina; Deminsky, Maxim; Eletskii, Alexander; Kirillov, Igor; Knizhnik, Andrei; Potapkin, Boris; Rykova, Elena; Umanskii, Stanislaw; Zaitsevskii, Andrei; Strelkova, Marina; Sukhanov, Leonid; Safonov, Andrei; Cotzas, George M.; Dean, Anthony; Michael, J. Darryl; Midha, Vikas; Smith, David J.; Sommerer, Timothy J.; Varatharajan, Bala; Tentner, Adrian

2007-04-01

103

In this work, we detail the derivation of a plasma kinetic theory leading to the components of the dielectric tensor for a magnetized dusty plasma with variable charge on the dust particles, considering that the dust component of the plasma contains spherical dust particles with different sizes, which are charged both by inelastic collisions of electrons and ions and by photoionization.

Galvao, R. A.; Ziebell, L. F. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP 91501-970, Porto Alegre, RS (Brazil)

2012-09-15

104

Kinetic Modeling of the Lunar Dust-Plasma Environment

NASA Astrophysics Data System (ADS)

Modeling of the lunar dust and plasma environment is a challenging task because a self-consistent model should include ions, electrons and dust particles and numerous other factors. However, most of the parameters are not well established or constrained by measurements in the lunar environment. More precisely, a comprehensive model should contain electrons originating from 1) the solar wind, 2) the lunar material (photoelectrons, secondary electrons) and 3) the lunar dust. Ions originate from the solar wind, the lunar material, the lunar exosphere and the dust. To model the role of the dust in the lunar plasma environment is a highly complex task since the properties of the dust particles in the exosphere are poorly known (e.g. mass, size, shape, conductivity) or not known (e.g. charge and photoelectron emission) and probably are time dependent. Models should also include the effects of interactions between the surface and solar wind and energetic particles, and micrometeorites. Largely different temporal and spatial scales are also a challenge for the numerical models. In addition, the modeling of a region on the Moon - for example on the South Pole - at a given time requires also knowledge of the solar illumination conditions at that time, mineralogical and electric properties of the local lunar surface, lunar magnetic anomalies, solar UV flux and the properties of the solar wind. Harmful effects of lunar dust to technical devices and to human health as well as modeling of the properties of the lunar plasma and dust environment have been topics of two ESA funded projects L-DEPP and DPEM. In the presentation we will summarize some basic results and characteristics of plasma and fields near and around the Moon as studied and discovered in these projects. Especially, we analyse three different space and time scales by kinetic models: [1] the "microscale" region near surface with an electrostatic PIC (ions and electrons are particles) model, [2] the "mesoscale" region including lunar magnetic anomalies and [3] the global scale Moon-solar wind interaction with hybrid (ions as particles in massless electron fluid) models.

Kallio, Esa; Alho, Markku; Alvarez, Francisco; Barabash, Stas; Dyadechkin, Sergey; Fernandes, Vera; Futaana, Yoshifumi; Harri, Ari-Matti; Haunia, Touko; Heilimo, Jyri; Holmström, Mats; Jarvinen, Riku; Lue, Charles; Makela, Jakke; Porjo, Niko; Schmidt, Walter; Shahab, Fatemi; Siili, Tero; Wurz, Peter

2014-05-01

105

SOLAR WIND TURBULENT SPECTRUM AT PLASMA KINETIC SCALES

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

106

NASA Astrophysics Data System (ADS)

Within the Vlasov's kinetic theory, describing the plasma wake field interaction, the collective transport of a warm nonlaminar relativistic charged particle beam is analyzed in the strongly nonlocal regime, where the beam spot-size is much less than the plasma wavelength. This is done in the overdense regime, i.e., the beam density is much less than the plasma density. The beam is supposed to be sufficiently long to experience the adiabatic shielding by the plasma. In these conditions, we neglect the longitudinal beam dynamics and focus on the transverse one only. We derive the virial description (envelope description) from the 2D Vlasov-Poisson-type system of equations that governs the transverse self-consistent plasma wake field excitation. The resulting envelope equation is then reduced, in the aberration-less approximation, to a differential equation for the beam spot size, where the role of the ambient magnetic field is evaluated in both laboratory and astrophysical environments. An analysis of the beam envelope self-modulation is then carried out and the criteria for the occurrence of the instability are found. Contribution to the Topical Issue "Theory and Applications of the Vlasov Equation", edited by Francesco Pegoraro, Francesco Califano, Giovanni Manfredi and Philip J. Morrison.

Fedele, Renato; Mannan, Abdul; De Nicola, Sergio; Jovanovi?, Dusan; Akhter, Tahmina

2014-09-01

107

CURRENT SHEETS AND COLLISIONLESS DAMPING IN KINETIC PLASMA TURBULENCE

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., E-mail: jason-tenbarge@uiowa.edu [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States)

2013-07-10

108

Effect of antenna size on electron kinetics in inductively coupled plasmas

Spatially resolved measurements of electron energy distribution functions (EEDFs) are investigated in inductively coupled plasmas with two planar antenna coils. When the plasma is sustained by the antenna with a diameter of 18 cm, the nonlocal kinetics is preserved in the argon gas pressure range from 2 mTorr to 20 mTorr. However, electron kinetics transit from nonlocal kinetics to local kinetics in discharge sustained by the antenna coil with diameter 34 cm. The results suggest that antenna size as well as chamber length are important parameters for the transition of the electron kinetics. Spatial variations of plasma potential, effective electron temperature, and EEDF in terms of total electron energy scale are also presented.

Lee, Hyo-Chang; Chung, Chin-Wook [Department of Electrical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)] [Department of Electrical Engineering, Hanyang University, Seoul 133-791 (Korea, Republic of)

2013-10-15

109

In this paper, we present our nonlinear kinetic modeling of stimulated Raman scattering in a uniform and collisionless plasma using envelope equations. We recall the derivation of these equations, as well as our theoretical predictions for each of the nonlinear kinetic terms, the precision of which having been carefully checked against Vlasov simulations. We particularly focus here on the numerical resolution of these equations, which requires the additional concept of ''self-optimization'' that we explain, and we describe the envelope code BRAMA that we used. As an application of our modeling, we present one-dimensional BRAMA simulations of stimulated Raman scattering which predict threshold intensities, as well as time scales for Raman growth above threshold, in very good agreement with those inferred from Vlasov simulations. Finally, we discuss the differences between our modeling and other published ones.

Benisti, Didier; Morice, Olivier; Gremillet, Laurent; Siminos, Evangelos; Strozzi, David J. [CEA, DAM, DIF, F-91297 Arpajon (France); AX Division, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

2010-10-15

110

Effects of kinetic processes in shaping Io's global plasma environment: A 3D hybrid model

NASA Astrophysics Data System (ADS)

The global dynamics of the ionized and neutral gases in the environment of Io plays an important role in the interaction of Jupiter's corotating magnetospheric plasma with Io. Stationary simulations of this problem have already been done using the magnetohydrodynamics (MHD) and the electrodynamics approaches. One of the major results of recent simplified two-fluid model simulations [Saur, J., Neubauer, F.M., Strobel, D.F., Summers, M.E., 2002. J. Geophys. Res. 107 (SMP5), 1-18] was the production of the structure of the double-peak in the magnetic field signature of the I0 flyby. These could not be explained before by standard MHD models. In this paper, we present a hybrid simulation for Io with kinetic ions and fluid electrons. This method employs a fluid description for electrons and neutrals, whereas for ions a particle approach is used. We also take into account charge-exchange and photoionization processes and solve self-consistently for electric and magnetic fields. Our model may provide a much more accurate description for the ion dynamics than previous approaches and allows us to account for the realistic anisotropic ion velocity distribution that cannot be done in fluid simulations with isotropic temperatures. The first results of such a simulation of the dynamics of ions in Io's environment are discussed in this paper. Comparison with the Galileo I0 flyby results shows that this approach provides an accurate physical basis for the interaction and can therefore naturally reproduce all the observed salient features.

Lipatov, Alexander S.; Combi, Michael R.

2006-02-01

111

Note on quantitatively correct simulations of the kinetic beam-plasma instability

NASA Astrophysics Data System (ADS)

A large number of model particles are shown necessary for quantitatively correct simulations of the kinetic beam-plasma instability with the clouds-in-cells method. The required number of particles scales inversely with the expected growth rate, as only a narrow interval of beam velocities is resonant with the wave in the kinetic regime.

Lotov, K. V.; Timofeev, I. V.; Mesyats, E. A.; Snytnikov, A. V.; Vshivkov, V. A.

2015-02-01

112

Kinetic Ignition Enhancement of Diffusion Flames by Nonequilibrium Magnetic Gliding Arc Plasma

Kinetic Ignition Enhancement of Diffusion Flames by Nonequilibrium Magnetic Gliding Arc Plasma Drexel University, Philadelphia, Pennsylvania 19104 DOI: 10.2514/1.33005 Kinetic ignition enhancement of of ignition temperatures and major species, as well as computations of rates of production and sensitivity

Ju, Yiguang

113

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

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

114

A statistical approach to a self-consistent description of kinetic and hydrodynamic processes in systems of interacting particles is formulated on the basis of the nonequilibrium statistical operator method by D.N.Zubarev. It is shown how to obtain the kinetic equation of the revised Enskog theory for a hard sphere model, the kinetic equations for multistep potentials of interaction and the Enskog-Landau kinetic equation for a system of charged hard spheres. The BBGKY hierarchy is analyzed on the basis of modified group expansions. Generalized transport equations are obtained in view of a self-consistent description of kinetics and hydrodynamics. Time correlation functions, spectra of collective excitations and generalized transport coefficients are investigated in the case of weakly nonequilibrium systems of interacting particles.

M. V. Tokarchuk; I. P. Omelyan; A. E. Kobryn

1999-03-04

115

Kinetic Description of the Coulomb Explosion of a Spherically Symmetric Cluster

The particle distribution function is calculated for the Coulomb explosion of a spherically symmetric charged cluster formed through the interaction of intense ultrashort laser pulses with a cluster gas. The particle density and mean velocity distributions as well as the energy spectra of the accelerated particles are obtained. These characteristics are analyzed in detail for a cold cluster plasma, where the kinetic effects determine the physics of multiple flows emerging after the turnover of the cluster particle velocity profile. We find the boundaries of the multiple-flow regions and study the characteristics of an exploding cluster as a function of its initial density profile. The energy spectra of the accelerated ions are obtained for a cluster plasma with a specified cluster size distribution.

Kovalev, V.F. [Institute for Mathematical Modeling, Russian Academy of Sciences, Moscow, 125047 (Russian Federation); Bychenkov, V.Yu. [Lebedev Physical Institute, Russian Academy of Sciences, Moscow, 119991 (Russian Federation)

2005-08-01

116

Ion kinetics in a helicon plasma source reactor

In this contribution we present correlated measurements of plasma optical emission, plasma potential and density, and ion axial and radial drift velocities in an extended {open_quotes}helicon{close_quotes} source/diffusion chamber system. This enables us to have insights about plasma excitation, transport and loss processes in this low pressure, high density plasma source.

Chatain, F.; Boswell, R.; Dalaire, A. [Universite Joseph Fourier, Saint Martin d`Heres (France)] [and others

1995-12-31

117

Field Theoretic Description of Ultrarelativistic Electron-Positron Plasmas

Ultrarelativistic electron-positron plasmas can be produced in high-intensity laser fields and play a role in various astrophysical situations. Their properties can be calculated using QED at finite temperature. Here we will use perturbative QED at finite temperature for calculating various important properties, such as the equation of state, dispersion relations of collective plasma modes of photons and electrons, Debye screening, damping rates, mean free paths, collision times, transport coefficients, and particle production rates, of ultrarelativistic electron-positron plasmas. In particular, we will focus on electron-positron plasmas produced with ultra-strong lasers.

Markus H. Thoma

2009-07-06

118

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

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

Ted Lee Williams

1999-01-01

119

Kinetic effects of non-equilibrium plasma-assisted methane oxidation on diffusion flame extinction discharge Plasma flame chemistry reactions Path flux analysis Counterflow extinction Partially premixed oxidation on the extinction of partially premixed methane flames was studied at 60 Torr by blending 2% CH4

Ju, Yiguang

120

We present a new, fully kinetic mechanism of generation of spatial magnetic vortices that results from the resonant wave-particle interaction in a plasma. This phenomenon is of basic theoretical interest. It can be responsible for the magnetic vortices observed in numerical simulations in the wake of an ultrastrong, ultraintense laser pulse in an underdense plasma. PMID:11019156

Califano; Pegoraro; Bulanov

2000-04-17

121

Electron kinetics and non-Joule heating in near-collisionless inductively coupled plasmas V. I of Houston, Houston, Texas 77204-4792 Received 1 July 1996 Electron kinetics in an inductively coupled plasma magnetic field induced by the coil current and the finite dimension of the plasma on electron heating

Economou, Demetre J.

122

Interaction between a high kinetic energy plasma jet and a target surface

NASA Astrophysics Data System (ADS)

A model is constructed to estimate the net energy deposited on a target wall bombarded by a plasma jet with gross kinetic energy much greater than its temperature and with density on the order of about 10 to the 19th power/CC (such as the plasma generated by a rail gun). Both one- and two-dimensional cases are examined to study the interactions between incident and reflected plasma ions. The results show that the reflected plasma plays an essential role in stopping the incident plasma energy over some small range of parameters.

Chen, Y. K.; Varghese, P. L.; Howell, J. R.

1986-12-01

123

Surface kinetics modeling of silicon oxide etching in fluorocarbon plasmas

Fluorocarbon plasma for silicon oxide etching is a complicated system involving many ion and neutral species. Depending on the plasma condition, many difficulties arise such as RIE lag, etch stop, and low selectivity to ...

Kwon, Ohseung, 1969-

2004-01-01

124

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

D. B. Blaschke; V. V. Dmitriev; G. Röpke; S. A. Smolyansky

2011-01-01

125

Implicit Methods for the Magnetohydrodynamic Description of Magnetically Confined Plasmas

Implicit algorithms are essential for predicting the slow growth and saturation of global instabilities in today’s magnetically confined fusion plasma experiments. Present day algorithms for obtaining implicit solutions to the magnetohydrodynamic (MHD) equations for highly magnetized plasma have their roots in algorithms used in the 1960s and 1970s. However, today’s computers and modern linear and non?linear solver techniques make practical much more comprehensive implicit algorithms than were previously possible. Combining these advanced implicit algorithms with highly accurate spatial representations of the vector fields describing the plasma flow and magnetic fields and with improved methods of calculating anisotropic thermal conduction now makes possible simulations of fusion experiments using realistic values of plasma parameters and actual configuration geometry.

S.C. Jardin

2010-09-28

126

NASA Astrophysics Data System (ADS)

This paper presents a systematic kinetic characterization of a low pressure high power hydrogen plasma. The plasma physics is described with a global model coupled to a homogeneous kinetic model for hydrogen. This model involves reactions which describe the vibrational and electronic excited kinetics of H2, the positive ?ft( H{+}{,}H2{+}{,}H3{+} \\right) and negative (H?) ion kinetics and the H chemistry. This enables the estimation of the particle density and the electron temperature and their evolutions as a function of power (1–100 kW) and pressure (0.3–4 Pa). These very specific plasma conditions involve physical phenomena not occurring in more usual plasmas, such as gas depletion. To account for this gas depletion, we incorporate in the global model both the H neutral heat equation to calculate the H temperature, and the gas pumping. Indeed, the gas depletion is mainly due to H atom heating leading to a higher pumping loss for H atoms. The consideration of the gas depletion allows us to obtain similar behaviors to the experiments when varying power and pressure. From an accurate analysis of the main formation and destruction pathways for each particle, the species kinetics is discussed and a simplified kinetic model that may be used to describe the non-equilibrium plasma in the negative source for ITER is proposed. Finally, the results point to strong coupling existing between the H atom wall recombination coefficient ?H and the gas depletion. An increase of ?H reduces the gas depletion, affecting the electron temperature and the electron density as well as the whole plasma kinetics.

Gaboriau, F.; Boeuf, J. P.

2014-12-01

127

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

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

128

Recent progress in the understanding of electron kinetics in low-pressure inductive plasmas

NASA Astrophysics Data System (ADS)

The electron kinetics of low-pressure plasmas is often dominated by the so-called "nonlocal" behavior of electrons which becomes evident if the electron energy relaxation length is of the order or larger than typical discharge dimensions. In this paper, a brief review of the various manifestations of "nonlocal electron kinetics" is given. Two effects based on nonlocal electron behavior are discussed in more detail. (1) In a steady-state inductive plasma, a flux pattern in electron energy-configuration space was observed through Langmuir probe measurements which resembles a convection cell. Comparisons between Langmuir probe measurements and numerical solutions of the Boltzmann equation are presented. (2) The temporal evolution of the electron distribution function was studied in the afterglow of a pulsed inductive plasma. An unusually fast decay of the electron mean kinetic energy was observed which is related to "diffusive cooling" of electrons.

Kortshagen, U.; Maresca, A.; Orlov, K.; Heil, B.

2002-05-01

129

Plasma-assisted ignition and combustion: nanosecond discharges and development of kinetic mechanisms

NASA Astrophysics Data System (ADS)

This review covers the results obtained in the period 2006-2014 in the field of plasma-assisted combustion, and in particular the results on ignition and combustion triggered or sustained by pulsed nanosecond discharges in different geometries. Some benefits of pulsed high voltage discharges for kinetic study and for applications are demonstrated. The necessity of and the possibility of building a particular kinetic mechanism of plasma-assisted ignition and combustion are discussed. The most sensitive regions of parameters for plasma-combustion kinetic mechanisms are selected. A map of the pressure and temperature parameters (P-T diagram) is suggested, to unify the available data on ignition delay times, ignition lengths and densities of intermediate species reported by different authors.

Starikovskaia, S. M.

2014-09-01

130

Nonlinear kinetic Alfvén waves with non-Maxwellian electron population in space plasmas

NASA Astrophysics Data System (ADS)

The present work discusses the effects of non-Maxwellian electron distributions on kinetic Alfvén waves in low-beta plasmas. Making use of the two-potential theory and employing the Sagdeev potential approach, the existence of solitary kinetic Alfvén waves having arbitrary amplitude is investigated. It is found that the use of non-Maxwellian population of electrons in the study of kinetic Alfvén waves leads to solutions corresponding to solitary structures that do not exist for Maxwellian electrons. The present investigation solves the riddle of plasma density fluctuations associated with strong electromagnetic perturbations observed by the Freja satellite. The present findings can also be applied to regions of space where various satellite missions have observed the presence of suprathermal populations of plasma species and where the low ? assumption is valid.

Masood, W.; Qureshi, M. N. S.; Yoon, P. H.; Shah, H. A.

2015-01-01

131

Closure of a kinetic model of plasma in strong turbulence by relaxation

NASA Technical Reports Server (NTRS)

A Fokker-Planck kinetic equation for a turbulent plasma is derived by a repeated cascade decomposition. Calculation of the propagator and the kinetic equation determine the transport coefficients (diffusivity and turbulent viscosity) by means of a closure based on a relaxation procedure governing the approach to equilibrium. The k to the minus third power spectral law is obtained, which governs the coupling between the velocity and the electrostatic field fluctuations.

Tchen, C. M.

1978-01-01

132

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

133

Kinetic limit of N-body description of wave-particle self-consistent interaction

NASA Astrophysics Data System (ADS)

The system of N particles ?^N=(x_1, v_1, ... x_N,v_N) interacting with M waves Zn = An exp( i ?_n) has been used to study the dynamics of Landau damping [1] and warm beam-plasma instability [2]. Given initial data (Z(0), ?^N(0)), it evolves according to hamiltonian dynamics to (Z^N(t), ?^N(t)). In the limit N arrow ?, the hamiltonian dynamics generates a Vlasov-like kinetic equation for f(x,v) coupled to envelope equations for the Zn : initial data (Z(0), f(0)) evolve to (Z(t), f(t)). We show that, for any time T>0, given a sequence of initial data with N arrow ? particles distributed so that f^N(0) arrow f(0) weakly, the states generated by the hamiltonian dynamics at all times 0

Firpo, M. C.; Elskens, Y.

1996-11-01

134

NASA Astrophysics Data System (ADS)

The quartz crystal microbalance (QCM) was exploited for cardiac markers detection and kinetic studies of immunochemical reaction of cardiac troponin I (cTnI) and human heart fatty acid binding protein (H-FABP) with the corresponding monoclonal antibodies in undiluted plasma (serum) and standard solutions. The QCM technique allowed to dynamically monitor the kinetic differences in specific interactions and nonspecific sorption, without multiple labeling procedures and separation steps. The affinity binding process was characterized by the association (ka) and the dissociation (kd) kinetic constants and the equilibrium association (K) constant, all of which were obtained from experimental data.

Agafonova, L. E.; Shumyantseva, V. V.; Archakov, A. I.

2014-06-01

135

Fully kinetic numerical modeling of a plasma thruster

A Hall effect plasma thruster with conductive acceleration channel walls was numerically modeled using 2D3V Particle-in-Cell (PIC) and Monte-Carlo Collision (MCC) methodolo- gies. Electron, ion, and neutral dynamics were ...

Szabo, James Joseph, 1969-

2001-01-01

136

Gas Kinetic Study of Magnetic Field Effects on Plasma Plumes

in the Hall regime are performed, confirming the theoretically predicted azimuthal rotation of the plasma jet due to Hall physics. The primary conclusion from this work is that the addition of the Hall effect generates helical structures in magnetic nozzle...

Ebersohn, Frans 1987-

2012-12-07

137

Theoretical studies on kinetics of singlet oxygen in nonthermal plasma

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

138

Turbulence in strongly coupled dusty plasmas using generalized hydrodynamic description

NASA Astrophysics Data System (ADS)

The properties of decaying turbulence have been studied with the help of a Generalized Hydrodynamic (GHD) fluid model in the context of strongly coupled dusty plasma medium in two dimensions. The GHD model treats the strongly coupled dusty plasma system as a visco-elastic medium. The incompressible limit of the GHD model is considered here. The studies carried out here are, however, applicable to a wider class of visco-elastic systems, and are not merely confined to the dusty plasma medium. Our simulations studies show that an initial spectrum that is confined in a limited domain of wave numbers becomes broad, even when the Reynold's number is much less than the critical value required for the onset of turbulence in Newtonian fluids. This is a signature of elastic turbulence, where Weissenberg's number also plays an important role on the onset of turbulence. This feature has been observed in several experiments. It is also shown that the existence of memory relaxation time parameter and the transverse shear wave inhibit the normal process (for 2-D systems) of inverse spectral cascade in this case. A detailed simulation study has been carried out for the understanding of this inhibition.

Tiwari, Sanat Kumar; Dharodi, Vikram Singh; Das, Amita; Patel, Bhavesh G.; Kaw, Predhiman

2015-02-01

139

Analytical solution of the kinetic equation for a uniform plasma in a magnetic field

The kinetic equation for a single-component uniform plasma in a magnetic field is analytically solved by the moment method. The linear system of ordinary differential equations for the moments is decomposed into subsystems of lower dimensions by a geometric method. The eigensystem of each subsystem shows that parallel moments decay monotonically, but perpendicular lth harmonic moments decay while oscillating with the l,l-2,...,-th harmonics of gyrofrequency. A generalization to a multicomponent plasma is discussed.

Ji, Jeong-Young; Held, Eric D. [Department of Physics, Utah State University, Logan, Utah 84322 (United States)

2010-07-15

140

NASA Astrophysics Data System (ADS)

A kinetic theory of tenuous plasmas and gases is elaborated, which is physically equivalent to the conventional theory and is based on the construction of distribution function propagators that depend on these distribution functions. A theory of short high-intensity laser pulse-plasma interaction is constructed on the basis of this kinetic theory. A general characteristic is provided for the absorption of high-intensity laser radiation by a plasma and its associated parametric instabilities. Considered next are diverse regimes of subpicosecond relativistic laser pulse-plasma interaction. In the framework of the theory elaborated here, an investigation was made of hot-electron production in the interaction of relativistic femtosecond laser pulses with a weakly nonuniform plasma at densities of the order of and above the critical density, as well as of fast-proton production in the irradiation of a thin foil with an admixture of hydrogen. Calculations were carried out with real ion charges and at realistic ion charges and realistic plasma densities. The results are consistent both with calculations by the generally accepted particle-in-cell technique and with experimental data.

Kosarev, Igor'N.

2006-12-01

141

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

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. [Budker Institute of Nuclear Physics SB RAS, Novosibirsk, Russia Novosibirsk State University, Novosibirsk (Russian Federation)] [Budker Institute of Nuclear Physics SB RAS, Novosibirsk, Russia Novosibirsk State University, Novosibirsk (Russian Federation)

2013-09-15

142

Advances in Fully-Kinetic PIC Simulations of a Near-Vacuum Hall Thruster and Other Plasma Systems

Advances in Fully-Kinetic PIC Simulations of a Near- Vacuum Hall Thruster and Other Plasma Systems;3 Advances in Fully-Kinetic PIC Simulations of a Near- Vacuum Hall Thruster and Other Plasma Systems Abstract In recent years, many groups have numerically modeled the near-anode region of a Hall thruster

143

2924 IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 36, NO. 6, DECEMBER 2008 Kinetic Ignition and Yiguang Ju Abstract--Kinetic ignition enhancement of H2 diffusion flames by a nonequilibrium plasma of a well-defined counterflow system. Measurements of ignition temperatures and major species as well

Ju, Yiguang

144

Kinetic dissipation and anisotropic heating in a turbulent collisionless plasma

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

145

Advances in petascale kinetic plasma simulation with VPIC and Roadrunner

VPIC [1], a first-principles 3d electromagnetic charge-conserving relativistic kinetic particle-in-cell code, was recently adapted to run on Los Alamos's Roadrunner [2], the first supercomputer to break a petaflop (1015 floating point operations per second) in the TOP500 supercomputer performance rankings. [3] We summarize VPIC's modeling capabilities, VPIC's optimization techniques and Roadrunner's computational characteristics. We then discuss three applications enabled by

Kevin J Bowers; Brian J Albright; Lin Yin; William S Daughton; Vadim Roytershteyn; B. Bergen; T. J. T. Kwan

2009-01-01

146

Drift kinetic Alfvén wave in temperature anisotropic plasma

By using the gyrokinetic theory, the kinetic Alfvén waves (KAWs) are discussed to emphasize the drift effects through the density inhomogeneity and the temperature anisotropy on their dispersion characteristics. The dependence of stabilization mechanism of the drift-Alfvén wave instability on the temperature anisotropy is highlighted. The estimate of the growth rate and the threshold condition for a wide range of parameters are also discussed.

Naim, Hafsa, E-mail: roohi-phy@yahoo.com; Bashir, M. F. [Salam Chair in Physics, G. C. University Lahore, Katchery Road, Lahore 54000 (Pakistan) [Salam Chair in Physics, G. C. University Lahore, Katchery Road, Lahore 54000 (Pakistan); Department of Physics, G. C. University Lahore, Katchery Road, Lahore 54000 (Pakistan); Murtaza, G. [Salam Chair in Physics, G. C. University Lahore, Katchery Road, Lahore 54000 (Pakistan)] [Salam Chair in Physics, G. C. University Lahore, Katchery Road, Lahore 54000 (Pakistan)

2014-03-15

147

Solar wind kinetic instabilities at small plasma betas

The ordinary perpendicular mode of drifting bi-Maxwellian plasma particle distributions with and without temperature anisotropy can provide aperiodic instabilities. These instabilities occur if the perpendicular thermal energy is much smaller than the streaming energy. This provides instabilities at small parallel plasma betas ?{sub ?}<1 and temperature anisotropies A?

Ibscher, D., E-mail: ibscher@tp4.rub.de; Schlickeiser, R. [Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany)] [Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany)

2014-02-15

148

Fluctuation-dissipation relations for a plasma-kinetic Langevin equation

NASA Astrophysics Data System (ADS)

A linearised kinetic equation describing electrostatic perturbations of a Maxwellian equilibrium in a weakly collisional plasma forced by a random source is considered. The problem is treated as a kinetic analogue of the Langevin equation and the corresponding fluctuation-dissipation relations are derived. The kinetic fluctuation-dissipation relation reduces to the standard ``fluid'' one in the regime where the Landau damping rate is small and the system has no real frequency; in this case the simplest possible Landau-fluid closure of the kinetic equation coincides with the standard Langevin equation. Phase mixing of density fluctuations and emergence of fine scales in velocity space is diagnosed as a constant flux of free energy in Hermite space; the fluctuation-dissipation relations for the perturbations of the distribution function are derived, in the form of a universal expression for the Hermite spectrum of the free energy. Finite-collisionality effects are included. This work is aimed at establishing the simplest fluctuation-dissipation relations for a kinetic plasma, clarifying the connection between Landau and Hermite-space formalisms, and setting a benchmark case for a study of phase mixing in turbulent plasmas.

Kanekar, A.; Schekochihin, A. A.; Dorland, W.; Loureiro, N. F.; Loureiro

2015-01-01

149

Imaging the assembly and disassembly kinetics of cis-SNARE complexes on native plasma membranes

Mild sonication of eukaryotic cells produces native plasma membrane sheets that retain their docked organelles, cytoskeleton structures and cytoplasmic complexes. While the delicate organization of membranous protein complexes remains undisturbed, their inner plasmalemmel leaflet can be rapidly exposed to bathing solutions, enabling specific biochemical manipulations. Here, we apply this system to track membrane-biochemistry kinetics. We monitor soluble NSF-attachment protein receptor

Dana Bar-On; Ulrike Winter; Esther Nachliel; Menachem Gutman; Dirk Fasshauer; Thorsten Lang; Uri Ashery

2008-01-01

150

American Institute of Aeronautics and Astronautics 1 Kinetic Effects of Non-Equilibrium Plasma 2011, Orlando, Florida AIAA 2011-971 Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved. #12;American Institute of Aeronautics and Astronautics 2 Xf = fuel mole

Ju, Yiguang

151

Kinetic theory on the current-filamentation instability in collisional plasmas

NASA Astrophysics Data System (ADS)

The current filamentation instability (CFI) or Weibel-type instability is studied for a nonrelativistic electron beam penetrating an infinite uniform plasma, taking into account both the collisional effects and the space-charge effect (SCE). We consider three configurations for the beam and plasma: the kinetic domain, the hydrodynamic domain, and the hybrid domain with one in kinetic and the other in hydrodynamic domain. It is shown that the CFI is determined by the current-driven drift-anisotropy rather than the classical anisotropy of the beam and the background plasma. Therefore, collisional effects can either attenuate or enhance the CFI depending on the drift-anisotropy of the beam and the background plasma. It is found that the collisional effects usually attenuate the CFI for nearly symmetric counterstreaming in the whole unstable range but enhance it for asymmetric counterstreaming in the long wavelength region both in the kinetic and the hydrodynamic domains, although the mechanisms are different. As for the case of the hybrid domain the collisional effects enhance the CFI growth rate in the long wavelength region but reduce it in the short wavelength region. The SCE can be ignored for the hydrodynamic domain while for the kinetic and the hybrid domains it is still significant though damped by the collisional effects. The combination of the SCE and the collisional effects usually reduce the CFI growth rate and suppress the unstable range further, especially in the short wavelength region.

Hao, Biao; Sheng, Z.-M.; Zhang, J.

2008-08-01

152

Ablation damage to solid targets with high heat flux impulses is generally greater high-energy electron beam heat sources compared to low-energy plasma guns. This sensitivity to incoming particle kinetic energy is explored with computer modelling; a fast-running routine (DESIRE) is developed for initial scoping analysis and is found to be in reasonable agreement with several experiments on graphite and tungsten targets. If tokamak disruptions are characterized by particle energies less than {approximately}1 keV, then we expect plasma guns are a better analogue than electron beams for simulating disruption behavior and testing candidate plasma-facing materials.

Ehst, D.A.; Hassanein, A.

1996-02-01

153

Localization of linear kinetic Alfvén wave in an inhomogeneous plasma and generation of turbulence

This paper presents a model for the propagation of Kinetic Alfvén waves (KAWs) in inhomogeneous plasma when the inhomogeneity is transverse to the background magnetic field. The semi-analytical technique and numerical simulations have been performed to study the KAW dynamics when plasma inhomogeneity is incorporated in the dynamics. The model equations are solved in order to study the localization of KAW and their magnetic power spectrum which indicates the direct transfer of energy from lower to higher wave numbers. The inhomogeneity scale length plays a very important role in the turbulence generation and its level. The relevance of these investigations to space and laboratory plasmas has also been pointed out.

Sharma, R. P.; Goyal, R., E-mail: ravig.iitd@gmail.com [Centre for Energy Studies, Indian Institute of Technology, Delhi-110016 (India); Scime, Earl E. [Department of Physics, West Virginia University, Morgantown, West Virginia 26506-6315 (United States)] [Department of Physics, West Virginia University, Morgantown, West Virginia 26506-6315 (United States); Dwivedi, N. K. [Austrian Academy of Sciences, Space Research Institute, Schmiedlstrasse 6, 8042 Graz (Austria)] [Austrian Academy of Sciences, Space Research Institute, Schmiedlstrasse 6, 8042 Graz (Austria)

2014-04-15

154

Time dependent evolution of linear kinetic Alfvén waves in inhomogeneous plasma

NASA Astrophysics Data System (ADS)

The propagation of linear Kinetic Alfvén waves (KAWs) in inhomogeneous magnetized plasma has been studied while including inhomogeneities in transverse and parallel directions relative to the background magnetic field. The propagation of KAWs in inhomogeneous magnetized plasma is expected to play a key role in energy transfer and turbulence generation in space and laboratory plasmas. The inhomogeneity scale lengths in both directions may control the nature of fluctuations and localization of the waves. We present a theoretical study of the localization of KAWs, variations in magnetic field amplitude in time, and variation in the frequency spectra arising from inhomogeneities. The relevance of the model to space and laboratory observations is discussed.

Goyal, R.; Sharma, R. P.; Scime, Earl E.

2015-02-01

155

Imaging the assembly and disassembly kinetics of cis-SNARE complexes on native plasma membranes.

Mild sonication of eukaryotic cells produces native plasma membrane sheets that retain their docked organelles, cytoskeleton structures and cytoplasmic complexes. While the delicate organization of membranous protein complexes remains undisturbed, their inner plasmalemmel leaflet can be rapidly exposed to bathing solutions, enabling specific biochemical manipulations. Here, we apply this system to track membrane-biochemistry kinetics. We monitor soluble NSF-attachment protein receptor (SNARE) complex assembly and disassembly on the plasma membrane at high time resolution. The results suggest two-phase kinetics for the assembly process and dependence of the disassembly kinetics on both N-ethyl maleimide-sensitive factor (NSF) and soluble NSF-attachment protein (alpha-SNAP) concentrations. PMID:18822290

Bar-On, Dana; Winter, Ulrike; Nachliel, Esther; Gutman, Menachem; Fasshauer, Dirk; Lang, Thorsten; Ashery, Uri

2008-10-15

156

Nonlocal electron kinetics in a weakly ionized plasma

NASA Astrophysics Data System (ADS)

Electron dynamics in a time dependent inhomogeneous electric field in a weakly ionized plasma with elastic electron-neutral collisions is analyzed. We consider the most general ordering when the electron mean free path vTe/?e is arbitrary with respect to the characteristic length scale k-1 of the electric field, and frequency ? of the electric field is arbitrary with respect to the electron collisional frequency ?e ?~?e~kvt. In this case the standard two-term approximation is not valid and higher order spherical harmonics in the perturbed electron distribution function should be taken into account. This results in an infinite hierarchy of coupled equations for angular harmonics that can be solved in the form of the infinite continued fraction. This method is easily generalized for a wide class of scattering cross sections with angular dependencies. The developed approach uniformly describes both local (strongly collisional) and nonlocal regimes. As an example, a closed form of the perturbed electron distribution function is found for the argon gas with nonmonotic dependence of the collisional cross section as function of energy (Ramsauer effect). The conductivity and surface impedance of a semi-infinite plasma are calculated in different collisionality regimes, and anomalous penetration of the electric field into such plasma is analyzed. The nonmonotonous behavior of the amplitude of the external electric field inside of a plasma has been recovered for the nonlocal case (?>1).

Furkal, E.; Smolyakov, A.; Hirose, A.

1998-07-01

157

Using a Krook collision model with relaxation to a flowing Maxwellian distribution function, a one dimensional flowing plasma solution to the kinetic equation is obtained for ions. The theory extends the analysis of collisionless flow from a theta pinch to include collisions, and yields a distribution function in the transition regime between collisonless and collisional flow. The model shows features of each extreme, and permits calculation of the fundamental system parameters including thermal energy flux and parallel viscosity to replace classically derived fluid description concepts which break down in this regime. A second problem which is investigated is the analysis of collisionless flow interaction with a representative reflecting surface. Reflected densities are calculated and presented for both specular and diffuse reflection. A comparison with a conventional reflected shock wave is also presented. The results indicate a density buildup near the reflector, as would be expected, and this effect is more pronounced when the reflected temperature is lower.

Ott, M. W.

1981-04-01

158

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

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

159

Transition from gas to plasma kinetic equilibria in gravitating axisymmetric structures

The problem of the transition from gas to plasma in gravitating axisymmetric structures is addressed under the assumption of having initial and final states realized by kinetic Maxwellian-like equilibria. In astrophysics, the theory applies to accretion-disc scenarios around compact objects. A formulation based on non-relativistic kinetic theory for collisionless systems is adopted. Equilibrium solutions for the kinetic distribution functions describing the initial neutral matter and the resulting plasma state are constructed in terms of single-particle invariants and expressed by generalized Maxwellian distributions. The final plasma configuration is related to the initial gas distribution by the introduction of appropriate functional constraints. Qualitative aspects of the solution are investigated and physical properties of the system are pointed out. In particular, the admitted functional dependences of the fluid fields carried by the corresponding equilibrium distributions are determined. Then, the plasma is proved to violate the condition of quasi-neutrality, implying a net charge separation between ions and electrons. This result is shown to be independent of the precise realization of the plasma distribution function, while a physical mechanism able to support a non-neutral equilibrium state is proposed.

Cremaschini, Claudio; Stuchlík, Zden?k [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezru?ovo nám.13, CZ-74601 Opava (Czech Republic)] [Institute of Physics, Faculty of Philosophy and Science, Silesian University in Opava, Bezru?ovo nám.13, CZ-74601 Opava (Czech Republic)

2014-04-15

160

Description of plasma focus current sheath as the Turner relaxed state of a Hall magnetofluid

The central mystery of plasma focus research is the two orders-of-magnitude-higher-than-thermal fusion reaction rate and the fact that both the space-resolved neutron spectra and space-resolved reaction proton spectra show features which can be ascribed only to a rotational motion of the center-of-mass of the reacting deuteron population. It has been suggested earlier [S. K. H. Auluck, IEEE Trans. Plasma Sci. 25, 37 (1997)] that this and other experimental observations can be consistently explained in terms of a hypothesis involving rotation of the current carrying plasma annulus behind the imploding gas-dynamic shock. Such rotation (more generally, mass flow) is an in-built feature of relaxed state of a two-fluid plasma [R. N. Sudan, Phys. Rev. Lett. 42, 1277 (1979)]. Relaxation in the 'Hall magnetofluid' approximation, in which the generalized Ohm's law includes the Hall effect term and the magnetic convection term but omits the contributions to the electric field from resistive dissipation, electron pressure gradient, thermoelectric effect, electron inertia, etc., has been extensively studied by many authors. In the present paper, Turner's [IEEE Trans. Plasma Sci. PS-14, 849 (1986)] degenerate solution for the relaxed state of the Hall magnetohydrodynamic plasma has been adapted to the case of an infinitely long annular current carrying plasma, a tractable idealization of the current sheath of a plasma focus. The resulting model is consistent with experimental values of ion kinetic energy and observation of predominantly radially directed neutron emission in good shots.

Auluck, S. K. H. [Advanced Technology Systems Section, Bhabha Atomic Research Centre, Mumbai 400085 (India)

2009-12-15

161

Kinetic simulations of argon dusty plasma afterglow including metastable atom kinetics

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., E-mail: a_alex@itam.nsc.ru; Schweigert, I. V.; Ariskin, D. A. [Siberian Branch of the Russian Academy of Sciences, Institute of Theoretical and Applied Mechanics (Russian Federation)

2013-04-15

162

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

163

Finite amplitude solitary structures of coupled kinetic Alfven-acoustic waves in dense plasmas

NASA Astrophysics Data System (ADS)

In this paper, we have investigated the nonlinear propagating coupled Kinetic Alfven-acoustic waves in a low beta degenerate quantum plasma in the presence of trapped Fermi electrons using the quantum hydrodynamic (QHD) model. By using the two potential theory and the Sagdeev potential approach, we have investigated the formation of solitary structures for coupled kinetic Alfven-acoustic waves in the presence of quantum mechanically trapped electrons. We have shown that there are regions of propagation and non-propagation for such solitary structures. We have also highlighted the differences between the classical and quantum mechanically trapped electrons. Interestingly, it has been found that the nature of the nonlinearity for the quantum mechanically trapped electrons is different from its classical counterpart. The results presented here may have applications in white dwarf asteroseismology as well as next generation laser-plasma experiments where low beta plasma condition is met.

Sabeen, A.; Shah, H. A.; Masood, W.; Qureshi, M. N. S.

2015-02-01

164

Plasma-Resistivity-Induced Strong Damping of the Kinetic Resistive Wall Mode

NASA Astrophysics Data System (ADS)

An energy-principle-based dispersion relation is derived for the resistive wall mode, which incorporates both the drift kinetic resonance between the mode and energetic particles and the resistive layer physics. The equivalence between the energy-principle approach and the resistive layer matching approach is first demonstrated for the resistive plasma resistive wall mode. As a key new result, it is found that the resistive wall mode, coupled to the favorable average curvature stabilization inside the resistive layer (as well as the toroidal plasma flow), can be substantially more stable than that predicted by drift kinetic theory with fast ion stabilization, but with the ideal fluid assumption. Since the layer stabilization becomes stronger with decreasing plasma resistivity, this regime is favorable for reactor scale, high-temperature fusion devices.

He, Yuling; Liu, Yueqiang; Liu, Yue; Hao, Guangzhou; Wang, Aike

2014-10-01

165

Plasma-resistivity-induced strong damping of the kinetic resistive wall mode.

An energy-principle-based dispersion relation is derived for the resistive wall mode, which incorporates both the drift kinetic resonance between the mode and energetic particles and the resistive layer physics. The equivalence between the energy-principle approach and the resistive layer matching approach is first demonstrated for the resistive plasma resistive wall mode. As a key new result, it is found that the resistive wall mode, coupled to the favorable average curvature stabilization inside the resistive layer (as well as the toroidal plasma flow), can be substantially more stable than that predicted by drift kinetic theory with fast ion stabilization, but with the ideal fluid assumption. Since the layer stabilization becomes stronger with decreasing plasma resistivity, this regime is favorable for reactor scale, high-temperature fusion devices. PMID:25379920

He, Yuling; Liu, Yueqiang; Liu, Yue; Hao, Guangzhou; Wang, Aike

2014-10-24

166

Alfven continuum deformation by kinetic geodesic effect in rotating tokamak plasmas

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

167

Energy Transfer and Dual Cascade in Kinetic Magnetized Plasma Turbulence

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.

Plunk, G. G.; Tatsuno, T. [Department of Physics and IREAP, University of Maryland, College Park, Maryland 20742 (United States)

2011-04-22

168

Ion kinetic properties in Mercury's pre-midnight plasma sheet

NASA Astrophysics Data System (ADS)

With data from the Fast Imaging Plasma Spectrometer sensor on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft, we demonstrate that the average distributions for both solar wind and planetary ions in Mercury's pre-midnight plasma sheet are well-described by hot Maxwell-Boltzmann distributions. Temperatures and densities of the H+-dominated plasma sheet, in the ranges ~1-10 cm-3 and ~5-30 MK, respectively, maintain thermal pressures of ~1 nPa. The dominant planetary ion, Na+, has number densities about 10% that of H+. Solar wind ions retain near-solar-wind abundances with respect to H+ and exhibit mass-proportional ion temperatures, indicative of a reconnection-dominated heating in the magnetosphere. Conversely, planetary ion species are accelerated to similar average energies greater by a factor of ~1.5 than that of H+. This energization is suggestive of acceleration in an electric potential, consistent with the presence of a strong centrifugal acceleration process in Mercury's magnetosphere.

Gershman, Daniel J.; Slavin, James A.; Raines, Jim M.; Zurbuchen, Thomas H.; Anderson, Brian J.; Korth, Haje; Baker, Daniel N.; Solomon, Sean C.

2014-08-01

169

Orszag Tang vortex - Kinetic study of a turbulent plasma

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

170

Kinetic Effects in Plasmas Relevant to Hot Spot Ignition

NASA Astrophysics Data System (ADS)

The use of radiation hydrodynamics codes to study laser-based Inertial Confinement Fusion and High Energy Density Physics is ubiquitous. In general, a single species fluid approximation is adequate during most of the interaction. However, there are critical times where electric fields, magnetic fields, or kinetic effects are potentially non-negligible. A number of examples where these effects are observed with the hybrid simulation code LSP will be presented. In particular, the effects of the tail of the electron and ion energy distributions on the fuel assembly and burn phases of hot spot ignition have been investigated in detail. The influence of electric and magnetic fields in 2-D will also be discussed.

Wilks, Scott; Amendt, P.; Bellei, C.; Williams, E.; Haines, M. G.; Welch, D.; Li, C.; Petrasso, R.

2012-10-01

171

Electron cyclotron resonance ion source (ECRIS) plasmas are prone to kinetic instabilities due to anisotropy of the electron energy distribution function stemming from the resonant nature of the electron heating process. Electron cyclotron plasma instabilities are related to non-linear interaction between plasma waves and energetic electrons resulting to strong microwave emission and a burst of energetic electrons escaping the plasma, and explain the periodic oscillations of the extracted beam currents observed in several laboratories. It is demonstrated with a minimum-B 14 GHz ECRIS operating on helium, oxygen, and argon plasmas that kinetic instabilities restrict the parameter space available for the optimization of high charge state ion currents. The most critical parameter in terms of plasma stability is the strength of the solenoid magnetic field. It is demonstrated that due to the instabilities the optimum Bmin-field in single frequency heating mode is often ?0.8BECR, which is the value suggested by the semiempirical scaling laws guiding the design of modern ECRISs. It is argued that the effect can be attributed not only to the absolute magnitude of the magnetic field but also to the variation of the average magnetic field gradient on the resonance surface. PMID:25725830

Tarvainen, O; Laulainen, J; Komppula, J; Kronholm, R; Kalvas, T; Koivisto, H; Izotov, I; Mansfeld, D; Skalyga, V

2015-02-01

172

NASA Astrophysics Data System (ADS)

Electron cyclotron resonance ion source (ECRIS) plasmas are prone to kinetic instabilities due to anisotropy of the electron energy distribution function stemming from the resonant nature of the electron heating process. Electron cyclotron plasma instabilities are related to non-linear interaction between plasma waves and energetic electrons resulting to strong microwave emission and a burst of energetic electrons escaping the plasma, and explain the periodic oscillations of the extracted beam currents observed in several laboratories. It is demonstrated with a minimum-B 14 GHz ECRIS operating on helium, oxygen, and argon plasmas that kinetic instabilities restrict the parameter space available for the optimization of high charge state ion currents. The most critical parameter in terms of plasma stability is the strength of the solenoid magnetic field. It is demonstrated that due to the instabilities the optimum Bmin-field in single frequency heating mode is often ?0.8BECR, which is the value suggested by the semiempirical scaling laws guiding the design of modern ECRISs. It is argued that the effect can be attributed not only to the absolute magnitude of the magnetic field but also to the variation of the average magnetic field gradient on the resonance surface.

Tarvainen, O.; Laulainen, J.; Komppula, J.; Kronholm, R.; Kalvas, T.; Koivisto, H.; Izotov, I.; Mansfeld, D.; Skalyga, V.

2015-02-01

173

Quantification of Transthyretin Kinetic Stability in Human Plasma Using Subunit Exchange

The transthyretin (TTR) amyloidoses are a group of degenerative diseases caused by TTR aggregation, requiring rate-limiting tetramer dissociation. Kinetic stabilization of TTR, by preferential binding of a drug to the native tetramer over the dissociative transition state, dramatically slows the progression of familial amyloid polyneuropathy. An established method for quantifying the kinetic stability of recombinant TTR tetramers in buffer is subunit exchange, in which tagged TTR homotetramers are added to untagged homotetramers at equal concentrations to measure the rate at which the subunits exchange. Herein, we report a subunit exchange method for quantifying the kinetic stability of endogenous TTR in human plasma. The subunit exchange reaction is initiated by the addition of a substoichiometric quantity of FLAG-tagged TTR homotetramers to endogenous TTR in plasma. Aliquots of the subunit exchange reaction, taken as a function of time, are then added to an excess of a fluorogenic small molecule, which immediately arrests further subunit exchange. After binding, the small molecule reacts with the TTR tetramers, rendering them fluorescent and detectable in human plasma after subsequent ion exchange chromatography. The ability to report on the extent of TTR kinetic stabilization resulting from treatment with oral tafamidis is important, especially for selection of the appropriate dose for patients carrying rare mutations. This method could also serve as a surrogate biomarker for the prediction of the clinical outcome. Subunit exchange was used to quantify the stabilization of WT TTR from senile systemic amyloidosis patients currently being treated with tafamidis (20 mg orally, once daily). TTR kinetic stability correlated with the tafamidis plasma concentration. PMID:24661308

2015-01-01

174

Kinetic study of the secondary plasma created in the ITER neutraliser

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

175

Kinetic theory of a two-dimensional magnetized plasma.

NASA Technical Reports Server (NTRS)

Several features of the equilibrium and nonequilibrium statistical mechanics of a two-dimensional plasma in a uniform dc magnetic field are investigated. The charges are assumed to interact only through electrostatic potentials. The problem is considered both with and without the guiding-center approximation. With the guiding-center approximation, an appropriate Liouville equation and BBGKY hierarchy predict no approach to thermal equilibrium for the spatially uniform case. For the spatially nonuniform situation, a guiding-center Vlasov equation is discussed and solved in special cases. For the nonequilibrium, nonguiding-center case, a Boltzmann equation, and a Fokker-Planck equation are derived in the appropriate limits. The latter is more tractable than the former, and can be shown to obey conservation laws and an H-theorem, but contains a divergent integral which must be cut off on physical grounds. Several unsolved problems are posed.

Vahala, G.; Montgomery, D.

1971-01-01

176

A Hybrid Fluid-Kinetic Theory for Plasma Physics

We parameterize the phase space density by time dependent diffeomorphic, Poisson preserving transformations on phase space acting on a reference density solution. We can look at these as transformations which fix time on the extended space of phase space and time. In this formulation the Vlasov equation is replaced by a constraint equation for the above maps. The new equations are formulated in terms of hamiltonian generators of one parameter families of diffeomorphic, Poisson preserving maps e.g. generators with respect to time or a perturbation parameter. We also show that it is possible to parameterize the space of solutions of the Vlasov equation by composition of maps subject to certain compatibility conditions on the generators. By using this composition principle we show how to formulate new equations for a hybrid fluid kinetic theory. This is done by observing that a certain subgroup of the group of phase space maps with generators which are linear in momentum correspond to the group of diffeomorphic maps parameterizing the continuity equation in fluid theory.

Tor Fla

2001-10-30

177

Dimension reduction of non-equilibrium plasma kinetic models using principal component analysis

NASA Astrophysics Data System (ADS)

The chemical complexity of non-equilibrium plasmas poses a challenge for plasma modeling because of the computational load. This paper presents a dimension reduction method for such chemically complex plasmas based on principal component analysis (PCA). PCA is used to identify a low-dimensional manifold in chemical state space that is described by a small number of parameters: the principal components. Reduction is obtained since continuity equations only need to be solved for these principal components and not for all the species. Application of the presented method to a CO2 plasma model including state-to-state vibrational kinetics of CO2 and CO demonstrates the potential of the PCA method for dimension reduction. A manifold described by only two principal components is able to predict the CO2 to CO conversion at varying ionization degrees very accurately.

Peerenboom, Kim; Parente, Alessandro; Kozák, Tomáš; Bogaerts, Annemie; Degrez, Gérard

2015-04-01

178

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

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.; Genesio, P.; Rosato, J.; Stamm, R.; Capes, H.; Koubiti, M.; Godbert-Mouret, L. [PIIM, CNRS/Aix-Marseille Univ., Marseille F-13397 Cedex 20 (France); Reiter, D.; Boerner, P. [IEK-4 Plasmaphysik, Forschungszentrum Juelich GmbH, TEC Euratom association, D-52425 Juelich (Germany); Catoire, F. [CELIA, UMR5107 CNRS-CEA-Universite de Bordeaux I, Talence F-33405 (France)

2012-06-15

179

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

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. [Institut für Theoretische Physik, Technische Universität Braunschweig, Mendelssohnstr. 3, D-38016 Braunschweig (Germany) [Institut für Theoretische Physik, Technische Universität Braunschweig, Mendelssohnstr. 3, D-38016 Braunschweig (Germany); Institute for Space Sciences, Atomi?tilor 409, P.O. Box MG-23, Bucharest-M?gurele RO-077125 (Romania); Verscharen, D. [Space Science Center, University of New Hampshire, 8 College Rd., Durham, New Hampshire 03824 (United States)] [Space Science Center, University of New Hampshire, 8 College Rd., Durham, New Hampshire 03824 (United States); Narita, Y. [Space Research Institute, Austrian Academy of Sciences, Schmiedlstr. 6, A-8042 Graz (Austria)] [Space Research Institute, Austrian Academy of Sciences, Schmiedlstr. 6, A-8042 Graz (Austria); Motschmann, U. [Institut für Theoretische Physik, Technische Universität Braunschweig, Mendelssohnstr. 3, D-38016 Braunschweig (Germany) [Institut für Theoretische Physik, Technische Universität Braunschweig, Mendelssohnstr. 3, D-38016 Braunschweig (Germany); Deutsches Zentrum für Luft- und Raumfahrt, Institut für Planetenforschung, Rutherfordstr. 2, D-12489 Berlin (Germany)

2013-09-15

180

Weakly relativistic quantum kinetic theory for electrostatic wave modes in magnetized plasmas

We have derived the electrostatic dispersion relation in a magnetized plasma using a recently developed quantum kinetic model based on the Dirac equation. The model contains weakly relativistic spin effects such as Thomas precession, the polarization currents associated with the spin and the spin-orbit coupling. It turns out that for strictly electrostatic perturbations the non-relativistic spin effects vanish, and the modification of the classical dispersion relation is solely associated with the relativistic terms. Several new wave modes appear due the electron spin effects, and an example for astrophysical plasmas are given.

Hussain, Azhar [Department of Physics, GC University Lahore, 54000 Lahore (Pakistan)] [Department of Physics, GC University Lahore, 54000 Lahore (Pakistan); Stefan, Martin; Brodin, Gert [Department of Physics, Umeå University, SE-901 87 Umeå (Sweden)] [Department of Physics, Umeå University, SE-901 87 Umeå (Sweden)

2014-03-15

181

Laboratory study of kinetic instabilities in a nonequilibrium mirror-confined plasma

NASA Astrophysics Data System (ADS)

Kinetic instabilities of nonequilibrium plasma heated by powerful radiation of gyrotron in electron cyclotron resonance conditions and confined in a mirror magnetic trap are reported. Instabilities are manifested as the generation of short pulses of electromagnetic radiation accompanied by precipitation of hot electrons from magnetic trap. Measuring electromagnetic field with high temporal resolution allowed to observe various dynamic spectra of electromagnetic radiation related to at least five types of kinetic instabilities. This paper may be of interest in the context of a laboratory modeling of nonstationary wave-particle interaction processes in nonequilibrium space plasma since the observed phenomena have much in common with similar processes occurring in the magnetosphere of the Earth, planets, and in solar coronal loops.

Viktorov, M.; Mansfeld, D.; Golubev, S.

2015-03-01

182

NASA Astrophysics Data System (ADS)

The paper describes an Adaptive Mesh in Phase Space (AMPS) technique for solving kinetic equations with deterministic mesh-based methods. The AMPS technique allows automatic generation of adaptive Cartesian mesh in both physical and velocity spaces using a Tree-of-Trees data structure. We illustrate advantages of AMPS for simulations of rarefied gas dynamics and electron kinetics on low temperature plasmas. In particular, we consider formation of the velocity distribution functions in hypersonic flows, particle kinetics near oscillating boundaries, and electron kinetics in a radio-frequency sheath. AMPS provide substantial savings in computational cost and increased efficiency of the mesh-based kinetic solvers.

Kolobov, Vladimir; Arslanbekov, Robert; Frolova, Anna

2014-12-01

183

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

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

2013-09-20

184

Electron kinetics in a discharge plasma produced by a focused microwave beam in free space

A study is made of the electron kinetics in a discharge plasma produced by a high-power beam of electromagnetic radiation\\u000a in the centimeter-wave region under conditions approaching free space, when the dimensions of the chamber are much greater\\u000a than the wavelength of the microwave radiation. Two regimes of discharge production are investigated: the regime of short\\u000a microsecond pulses at a

A. A. Kuzovnikov; V. M. Shibkov; L. V. Shibkova

1997-01-01

185

A description of hydrolysis kinetics in anaerobic degradation of particulate organic matter

Four types of hydrolysis kinetics were tested for anaerobic degradation of complex organic matter using the generalized simulation model described earlier. The simulation dynamics from all types of hydrolysis kinetics of swine waste, sewage sludge and cattle manure for continuous-flow reactors at a defined SRT fitted the experimental data comparatively well. However, differences were found for particulate organic matter degradation

V. A. Vavilin; S. V. Rytov; L. Ya. Lokshina

1996-01-01

186

Surface kinetics and plasma equipment model for Si etching by fluorocarbon plasmas

with the goal of combining plasma chemistry and surface chemistry in a self-consistent fashion. The SKM obtains during Si etching using fluorocarbon gases in an induc- tively coupled plasma ICP reactor.4 They observed equipment, surface chemistry, and molecular dynamics mod- els have been successful in separately addressing

Kushner, Mark

187

BACKGROUND Conventional concept suggests that infused crystalloid fluid is first distributed in the plasma volume and then, since the capillary permeability for fluid is very high, almost instantly equilibrates with the extracellular fluid space. We challenge whether this view is consistent with findings based on volume kinetic analysis. METHODS Fifteen volunteers received an IV infusion of 15 mL/kg of lactated Ringer’s solution during 10 min. Simultaneous arterial and venous blood hemoglobin (Hgb) samples were obtained and Hgb concentrations measured. The arteriovenous (AV) difference in Hgb dilution in the forearm was determined and a volume kinetic model was fitted to the series of Hgb concentrations in arterial and venous blood. RESULTS The AV difference in plasma dilution was only positive during the infusion and for 2.5 min thereafter, which represents the period of net flow of fluid from plasma to tissue. Kinetic analysis showed that volume expansion of the peripheral fluid space began to decrease 14 min (arterial blood) and 20 min (venous blood) after the infusion ended. Distribution of lactated Ringer’s solution apparently occurs much faster in the forearm than in the body as a whole. Therefore, the AV difference in the arm does not accurately reflect the distribution of Ringer’s solutions or whole-body changes in plasma volume. CONCLUSIONS The relatively slow whole-body distribution of lactated Ringer’s solution, which boosts the plasma volume expansion during and for up to 30 min after an infusion, is probably governed by a joint effect of capillary permeability and differences in tissue perfusion between body regions. PMID:19095840

Svensen, Christer H.; Rodhe, Peter M.; Olsson, Joel; Børsheim, Elisabet; Aarsland, Asle; Hahn, Robert G.

2015-01-01

188

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

189

Core Physics and Kinetics Calculations for the Fissioning Plasma Core Reactor

NASA Technical Reports Server (NTRS)

Highly efficient, compact nuclear reactors would provide high specific impulse spacecraft propulsion. This analysis and numerical simulation effort has focused on the technical feasibility issues related to the nuclear design characteristics of a novel reactor design. The Fissioning Plasma Core Reactor (FPCR) is a shockwave-driven gaseous-core nuclear reactor, which uses Magneto Hydrodynamic effects to generate electric power to be used for propulsion. The nuclear design of the system depends on two major calculations: core physics calculations and kinetics calculations. Presently, core physics calculations have concentrated on the use of the MCNP4C code. However, initial results from other codes such as COMBINE/VENTURE and SCALE4a. are also shown. Several significant modifications were made to the ISR-developed QCALC1 kinetics analysis code. These modifications include testing the state of the core materials, an improvement to the calculation of the material properties of the core, the addition of an adiabatic core temperature model and improvement of the first order reactivity correction model. The accuracy of these modifications has been verified, and the accuracy of the point-core kinetics model used by the QCALC1 code has also been validated. Previously calculated kinetics results for the FPCR were described in the ISR report, "QCALC1: A code for FPCR Kinetics Model Feasibility Analysis" dated June 1, 2002.

Butler, C.; Albright, D.

2007-01-01

190

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

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

191

Plasma low density lipoprotein transport kinetics in noninsulin-dependent diabetes mellitus.

Plasma low density lipoprotein (LDL) transport kinetics were determined from the disappearance of 125I-LDL injected into age- and weight-matched groups of 13 normal subjects, 20 mild diabetics, and 8 moderately severe diabetic patients (fasting plasma glucose less than 150 and greater than 150 mg/100 ml, respectively). In mild diabetics, LDL apo-lipoprotein-B (apo-B) synthetic rate (SR) was significantly greater than normal. The fractional catabolic rate (FCR), however, was also increased so that plasma LDL concentration remained normal. In moderately severe diabetics, LDL SR was normal but FCR was reduced resulting in increased plasma LDL cholesterol and apo-B concentrations. In normal subjects, moderate obesity was associated with increased LDL secretion. In diabetic subjects, however, changes in LDL turnover were of equal magnitude in obese and nonobese patients. In normolipemic and hyperlipemic mild diabetic subjects with equal degrees of glucose intolerance, both LDL apo-B SR and FCR were greater than normal. The magnitude of these increases, however, was lower in the hyperlipemic individuals. Stepwise regression analysis revealed that both LDL SR and FCR correlated positively and linearly with insulin response to glucose loading, but negatively and curvilinearly with fasting plasma glucose and glucose response. We propose that in noninsulin-dependent diabetes, mild hyperglycemia is accompanied by increased LDL turnover, despite normal plasma LDL levels, whereas moderately severe hyperglycemia is associated with decreased LDL catabolism, resulting in increased plasma LDL levels. These changes cannot be attributed to the presence of obesity or hypertriglyceridemia, and may relate to varying degrees of insulin resistance and decreased insulin secretion affecting plasma very low density lipoprotein (VLDL) secretion, VLDL conversion to LDL, and LDL catabolism. Both increased LDL turnover in mild diabetes and delayed removal of LDL in moderately severe diabetes could increase cholesterol ester availability to peripheral tissues, and may result in an increased risk of atherosclerosis. PMID:6338042

Kissebah, A H; Alfarsi, S; Evans, D J; Adams, P W

1983-01-01

192

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

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

193

A Hamiltonian fluid-kinetic model for a two-species non-neutral plasma

A model for describing the dynamics of a pure electron plasma in the presence of a population of massive charged particles is presented. The model couples the fluid dynamics of the pure electron plasma with the dynamics of the massive particle population, the latter being treated kinetically. The model is shown to possess a noncanonical Hamiltonian structure and to preserve invariants analogous to those of the two-dimensional (2D) Euler equation for an incompressible inviscid fluid, and of the Vlasov equation. The Hamiltonian structure of the model is used to derive a set of stability conditions for rotating coherent structures of the two-species system, in the case of negatively charged massive particles. According to these conditions, stability is attained if both the equilibrium distribution function of the kinetic species and the equilibrium density of the electron fluid are monotonically decreasing functions of the corresponding single-particle energies in the rotating frame. For radially confined equilibria near the axis, the stability condition corresponds to the existence of a finite interval of rotation frequencies for the reference frame, with the upper bound determined by the presence of the kinetic population.

Tassi, E.; Chandre, C. [Aix-Marseille Université, Université de Toulon, CNRS CPT UMR 7332, 13288 Marseille (France)] [Aix-Marseille Université, Université de Toulon, CNRS CPT UMR 7332, 13288 Marseille (France); Romé, M. [INFN Sezione di Milano and Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, I-20133 Milano (Italy)] [INFN Sezione di Milano and Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, I-20133 Milano (Italy)

2014-04-15

194

Plasma Physics for Nuclear Fusion

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

195

NASA Astrophysics Data System (ADS)

An extensive self-consistent air-plasma model based upon the Boltzmann equation for the electron energy distribution function, coupled with a heavy particle kinetics was developed to study electric discharges in a preexisting air plasma column [1]. Incorporated in the model are the steady-state balance equations for various nitrogen and oxygen species in ground and excited states, as well as atomic and molecular ions. The influence of the gas temperature is accounted for by reduction of the neutral density, collisional processes such as recombination, dissociation, V-V and V-T reactions [2], and by reactions involving electronically excited states of O2. The model was applied to study the influence of the gas temperature and vibrational kinetics on the breakdown processes in a preformed air plasma channel. Numerical calculations predict that electrical breakdown occurs at relatively low electric field. The calculated self-consistent breakdown electric field is ˜10 kV/cm for gas temperature of 300 K, while at temperature of 600 K it drops to ˜5.7 kV/cm, in excellent agreement with the experimentally determined breakdown electric field [1]. * NRC-NRL Postdoc [1] Tz.B. Petrova, H.D. Ladouceur, and A.P. Baronavski, 58th Gaseous Electronics Conference, 2005; San Jose, California, FM.00062 [2] J. Loureiro and C.M. Ferreira, J. Phys. D: Appl. Phys 19 (1986) 17-35

Ladouceur, Harold; Baronavski, Andrew; Petrova, Tzvetelina

2006-03-01

196

Kinetics of general electromagnetic fluctuations in unmagnetized plasmas: aperiodic thermal noise

NASA Astrophysics Data System (ADS)

Any fully-ionized collisionless plasma with finite random particle velocities contains electric and magnetic field fluctuations which are of three different types: weakly damped, weakly propagating or aperiodic. The kinetics of these fluctuations in general unmagnetized plasmas is governed by the competition of spontaneous emission, absorption and stimulated emission processes. The generalized Kirchhoff laws for both collective and non-collective fluctuations are derived, which in stationary plasmas provide the equilibrium energy densities of electromagnetic fluctuations by the ratio of the respective spontaneous emission and true absorption coefficients. The equilibrium energy densities of aperiodic transverse collective electric and magnetic fluctuations in an isotropic thermal electron–proton plasma of density ne is calculated as \\mid ? B\\mid =\\sqrt{{{(? B)}2}}=2.8{{({{n}e}{{m}e}{{c}2})}1/2}{{g}1/2}? e7/4 and \\mid ? E\\mid =\\sqrt{{{(? E)}2}}=3.2{{({{n}e}{{m}e}{{c}2})}1/2}{{g}1/3}? e2 , where g and ?e denote the plasma parameter and the thermal electron velocity in units of the speed of light. For densities and temperatures of the reionized early intergalactic medium ??B? = 6 · 10?18 G and ??E? = 2 · 10?16 G result.

Schlickeiser, R.; Yoon, P. H.

2015-01-01

197

Electron and ion kinetic effects on non-linearly driven electron plasma and ion acoustic waves

Fully non-linear kinetic simulations of electron plasma and ion acoustic waves (IAWs) have been carried out with a new multi-species, parallelized Vlasov code. The numerical implementation of the Vlasov model and the methods used to compute the wave frequency are described in detail. For the first time, the nonlinear frequency of IAWs, combining the contributions from electron and ion kinetic effects and from harmonic generation, has been calculated and compared to Vlasov results. Excellent agreement of theory with simulation results is shown at all amplitudes, harmonic generation being an essential component at large amplitudes. For IAWs, the positive frequency shift from trapped electrons is confirmed and is dominant for the effective electron-to-ion temperature ratio, Z T{sub e}/T{sub i} Greater-Than-Or-Equivalent-To 10 with Z as the charge state. Furthermore, numerical results demonstrate unambiguously the dependence [R. L. Dewar, Phys. Fluids 15, 712 (1972)] of the kinetic shifts on details of the distribution of the trapped particles, which depends in turn on the conditions under which the waves were generated. The trapped particle fractions and energy distributions are derived and, upon inclusion of harmonic effects, shown to agree with the simulation results, completing a consistent picture. Fluid models of the wave evolution are considered but prove unable to capture essential details of the kinetic simulations. Detrapping by collisions and sideloss is also discussed.

Berger, R. L.; Chapman, T.; Divol, L.; Still, C. H. [Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Livermore, California 94551 (United States); Brunner, S. [Centre de Recherches en Physique des Plasmas, Association Euratom-Confederation Suisse, Ecole Polytechnique Federale de Lausanne, CRPP-PPB, CH-1015 Lausanne (Switzerland); Valeo, E. J. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543-0451 (United States)

2013-03-15

198

The relative importance of fluid and kinetic frequency shifts of an electron plasma wave

The total nonlinear frequency shift of a plasma wave including both fluid and kinetic effects is estimated when the phase velocity of the wave is much less than the speed of light. Using a waterbag or fluid model, the nonlinear frequency shift due to harmonic generation is calculated for an arbitrary shift in the wavenumber. In the limit where the wavenumber does not shift, the result is in agreement with previously published work [R. L. Dewar and J. Lindl, Phys. Fluids 15, 820 (1972); T. P. Coffey, ibid. 14, 1402 (1971)]. This shift is compared to the kinetic shift of Morales and O'Neil [G. J. Morales and T. M. O'Neil, Phys. Rev. Lett. 28, 417 (1972)] for wave amplitudes and values of k{lambda}{sub D} of interest to Raman backscatter of a laser driver in inertial confinement fusion.

Winjum, B. J.; Fahlen, J.; Mori, W. B. [Department of Physics and Astronomy, University of California, Los Angeles, California 90095 (United States); Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States); Department of Physics and Astronomy and Department of Electrical Engineering, University of California, Los Angeles, California 90095 (United States)

2007-10-15

199

Nonlinear interaction and parametric instability of kinetic Alfven waves in multicomponent plasmas

Nonlinear couplings among kinetic Alfven waves are investigated for a three-component plasma consisting of electrons, protons, and heavy ions. The parametric instability is investigated, and the growth rate is obtained. In the kinetic regime, the growth rate for the parallel decay instability increases with the heavy ion content, but the growth rate for the reverse decay is independent of the latter since the perpendicular wavelength is much larger than the ion gyroradius. It decreases with the heavy ion content when the perpendicular wavelength is of the order of the ion gyroradius. It is also found that in the short perpendicular wavelength limit, the growth rate is only weakly affected by the heavy ions. On the other hand, in the inertial regime, for both parallel and reverse decay cases, the growth rate decreases as the number of heavy ions becomes large.

Zhao, J. S.; Yang, L. [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Wu, D. J. [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Lu, J. Y. [College of Mathematics and Statistics, Nanjing University of Information Science and Technology, Nanjing 210044 (China); National Center for Space Weather, China Meteorology Administration, Beijing 100081 (China)

2013-03-15

200

Suprathermal tails in the distributions of electron velocities parallel to the magnetic field are found in many areas of plasma physics, from magnetic confinement fusion to solar system plasmas. Parallel electron kinetic energy can be transferred into plasma waves and perpendicular gyration energy of particles through the anomalous Doppler instability (ADI), provided that energetic electrons with parallel velocities v{sub ||}?(?+?{sub ce})/k{sub ||} are present; here ?{sub ce} denotes electron cyclotron frequency, ? the wave angular frequency, and k{sub ||} the component of wavenumber parallel to the magnetic field. This phenomenon is widely observed in tokamak plasmas. Here, we present the first fully self-consistent relativistic particle-in-cell simulations of the ADI, spanning the linear and nonlinear regimes of the ADI. We test the robustness of the analytical theory in the linear regime and follow the ADI through to the steady state. By directly evaluating the parallel and perpendicular dynamical contributions to j·E in the simulations, we follow the energy transfer between the excited waves and the bulk and tail electron populations for the first time. We find that the ratio ?{sub ce}/(?{sub pe}+?{sub ce}) of energy transfer between parallel and perpendicular, obtained from linear analysis, does not apply when damping is fully included, when we find it to be ?{sub pe}/(?{sub pe}+?{sub ce}); here ?{sub pe} denotes the electron plasma frequency. We also find that the ADI can arise beyond the previously expected range of plasma parameters, in particular when ?{sub ce}>?{sub pe}. The simulations also exhibit a spectral feature which may correspond to the observations of suprathermal narrowband emission at ?{sub pe} detected from low density tokamak plasmas.

Lai, W. N. [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)] [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Chapman, S. C. [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom) [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Department of Mathematics and Statistics, University of Tromsø, Tromsø (Norway); Dendy, R. O. [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom) [Centre for Fusion, Space and Astrophysics, Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom)

2013-10-15

201

The quantum-classical hybrid-description of rare-gas clusters interacting with intense light pulses which we have developed is described in detail. Much emphasis is put on the treatment of screening electrons in the cluster which set the time scale for the evolution of the system and form the link between electrons strongly bound to ions and quasi-free plasma electrons in the cluster. As an example we discuss the dynamics of an Ar147 cluster exposed to a short VUV laser pulse of 20eV photon energy.

Georgescu, Ionut; Rost, Jan M

2007-01-01

202

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

203

Noradrenaline plasma kinetics were assessed in 17 male patients, who had been treated with metoprolol 100-200 mg daily (n = 8) or placebo for 3 years after an acute myocardial infarction, before and 1 week after gradual withdrawal (during 1 week) of the study treatment. Endogenous noradrenaline concentrations in plasma were measured by high performance liquid chromatography. Noradrenaline spillover rate, plasma clearance and the t1/2 for the rapid removal from plasma were determined by radio-tracer methodology. During treatment the plasma noradrenaline concentrations and noradrenaline plasma kinetic variables were similar in the two groups. Venous plasma noradrenaline concentrations were more closely correlated to the spillover rates of noradrenaline to plasma than to the clearance of noradrenaline from plasma, but the spillover rates were correlated to the clearance rates. Following the withdrawal of metoprolol noradrenaline clearance from plasma increased slightly (by 18 +/- 5%, P less than 0.05), but the plasma concentrations and spillover rates of noradrenaline were unchanged. In the placebo group withdrawal did not result in any significant changes. Our results indicate that a generalised increase in sympathetic nerve activity is not the cause of so-called rebound phenomena following withdrawal of chronic beta-adrenoceptor blockade. PMID:6487497

Olsson, G; Daleskog, M; Hjemdahl, P; Rehnqvist, N

1984-01-01

204

A global model has been developed for low-pressure, inductively coupled plasma (ICP) SF{sub 6}/O{sub 2}/Ar mixtures. This model is based on a set of mass balance equations for all the considered species, coupled with the discharge power balance equation and the charge neutrality condition. The present study is an extension of the kinetic global model previously developed for SF{sub 6}/Ar ICP plasma discharges [Lallement et al., Plasma Sources Sci. Technol. 18, 025001 (2009)]. It is focused on the study of the impact of the O{sub 2} addition to the SF{sub 6}/Ar gas mixture on the plasma kinetic properties. The simulation results show that the electron density increases with the %O{sub 2}, which is due to the decrease of the plasma electronegativity, while the electron temperature is almost constant in our pressure range. The density evolutions of atomic fluorine and oxygen versus %O{sub 2} have been analyzed. Those atomic radicals play an important role in the silicon etching process. The atomic fluorine density increases from 0 up to 40% O{sub 2} where it reaches a maximum. This is due to the enhancement of the SF{sub 6} dissociation processes and the production of fluorine through the reactions between SF{sub x} and O. This trend is experimentally confirmed. On the other hand, the simulation results show that O(3p) is the preponderant atomic oxygen. Its density increases with %O{sub 2} until reaching a maximum at almost 40% O{sub 2}. Over this value, its diminution with O{sub 2}% can be justified by the high increase in the loss frequency of O(3p) by electronic impact in comparison to its production frequency by electronic impact with O{sub 2}.

Pateau, Amand [Institut des Matériaux Jean Rouxel, Université de Nantes, 2 rue de la Houssiniére 44322 Nantes, France and ST Microelectronics, 10 rue Thals de Milet, 37071 Tours (France); Rhallabi, Ahmed, E-mail: ahmed.rhallabi@univ-nantes.fr; Fernandez, Marie-Claude [Institut des Matériaux Jean Rouxel, Université de Nantes, 2 rue de la Houssiniére 44322 Nantes (France); Boufnichel, Mohamed; Roqueta, Fabrice [ST Microelectronics, 10 rue Thales de Milet, 37071 Tours (France)

2014-03-15

205

Kinetic simulation of capacitively coupled plasmas driven by trapezoidal asymmetric voltage pulses

A kinetic Particle-In-Cell simulation with Monte Carlo Collisions was performed of a geometrically symmetric capacitively coupled, parallel-plate discharge in argon, driven by trapezoidal asymmetric voltage pulses with a period of 200?ns. The discharge was electrically asymmetric, making the ion energy distributions at the two electrodes different from one another. The fraction of the period (?), during which the voltage was kept at a constant (top-flat) positive value, was a critical control parameter. For the parameter range investigated, as ? increased, the mean ion energy on the grounded electrode increased and the ions became more directional, whereas the opposite was found for the ions striking the powered electrode. The absolute value of the DC self-bias voltage decreased as ? increased. Plasma instabilities, promoted by local double layers and electric field reversals during the time of the positive voltage excursion, were characterized by electron plasma waves launched from the sheath edge.

Diomede, Paola, E-mail: padiomede@gmail.com; Economou, Demetre J., E-mail: economou@uh.edu [Plasma Processing Laboratory, Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004 (United States)

2014-06-21

206

Electron energy distribution functions have been calculated by a self-consistent model which couples the electron Boltzmann equation with vibrationally and electronically excited state kinetics and plasma chemistry. Moderate pressure nitrogen gas discharges in the E/N range from 30 to 60 Townsend are investigated comparing an electron-impact cross section set considering transitions starting from all the vibrational states, with reduced models, taking into account only collisions involving the ground vibrational level. The results, while confirming the important role of second kind collisions in affecting the eedf, show a large dependence of the eedf on the set of inelastic processes involving vibrationally and electronically excited molecules, pointing out the need of using a cross section database including processes linking excited states in non-equilibrium plasma discharge models.

Capitelli, Mario [Dipartimento di Chimica, Universitá di Bari, Via Orabona 4, 70125 Bari (Italy) [Dipartimento di Chimica, Universitá di Bari, Via Orabona 4, 70125 Bari (Italy); CNR-IMIP, Via Amendola 122/D, 70126 Bari (Italy); Colonna, Gianpiero; D'Ammando, Giuliano; Laricchiuta, Annarita [CNR-IMIP, Via Amendola 122/D, 70126 Bari (Italy)] [CNR-IMIP, Via Amendola 122/D, 70126 Bari (Italy); Laporta, Vincenzo [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom)] [Department of Physics and Astronomy, University College London, London WC1E 6BT (United Kingdom)

2013-10-15

207

Plasma heating at collisionless shocks due to the kinetic cross-field streaming instability

NASA Technical Reports Server (NTRS)

Heating at collisionless shocks due to the kinetic cross-field streaming instability, which is the finite beta (ratio of plasma to magnetic pressure) extension of the modified two stream instability, is studied. Heating rates are derived from quasi-linear theory and compared with results from particle simulations to show that electron heating relative to ion heating and heating parallel to the magnetic field relative to perpendicular heating for both the electrons and ions increase with beta. The simulations suggest that electron dynamics determine the saturation level of the instability, which is manifested by the formation of a flattop electron distribution parallel to the magnetic field. As a result, both the saturation levels of the fluctuations and the heating rates decrease sharply with beta. Applications of these results to plasma heating in simulations of shocks and the earth's bow shock are described.

Winske, D.; Quest, K. B.; Tanaka, M.; Wu, C. S.

1985-01-01

208

Kinetic simulation of capacitively coupled plasmas driven by trapezoidal asymmetric voltage pulses

NASA Astrophysics Data System (ADS)

A kinetic Particle-In-Cell simulation with Monte Carlo Collisions was performed of a geometrically symmetric capacitively coupled, parallel-plate discharge in argon, driven by trapezoidal asymmetric voltage pulses with a period of 200 ns. The discharge was electrically asymmetric, making the ion energy distributions at the two electrodes different from one another. The fraction of the period (?), during which the voltage was kept at a constant (top-flat) positive value, was a critical control parameter. For the parameter range investigated, as ? increased, the mean ion energy on the grounded electrode increased and the ions became more directional, whereas the opposite was found for the ions striking the powered electrode. The absolute value of the DC self-bias voltage decreased as ? increased. Plasma instabilities, promoted by local double layers and electric field reversals during the time of the positive voltage excursion, were characterized by electron plasma waves launched from the sheath edge.

Diomede, Paola; Economou, Demetre J.

2014-06-01

209

Excited-state kinetics and radiation transport in low-temperature plasmas

NASA Astrophysics Data System (ADS)

An advanced self-consistent plasma physics model including non-equilibrium vibrational kinetics, a collisional radiative model for atomic species, a Boltzmann solver for the electron energy distribution function, a radiation transport module coupled to a steady inviscid flow solver and, has been applied to study non-equilibrium in high enthalpy flows for Jupiter’s atmosphere. Two systems have been considered, a hypersonic shock tube and nozzle expansion, emphasizing the role of radiation reabsorption on macroscopic and microscopic flow properties. Large differences are found between thin and thick plasma conditions not only for the distributions, but also for the macroscopic quantities. In particular, in the nozzle expansion case, the electron energy distribution functions are characterized by a rich structure induced by superelastic collisions between excited species and cold electrons.

Colonna, G.; D’Ammando, G.; Pietanza, L. D.; Capitelli, M.

2015-01-01

210

NASA Technical Reports Server (NTRS)

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 Oþ þ and Sþ þ 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, David G.

2013-01-01

211

Merging for Particle-Mesh Complex Particle Kinetic Modeling of the Multiple Plasma Beams

NASA Technical Reports Server (NTRS)

We suggest a merging procedure for the Particle-Mesh Complex Particle Kinetic (PMCPK) method in case of inter-penetrating flow (multiple plasma beams). We examine the standard particle-in-cell (PIC) and the PMCPK methods in the case of particle acceleration by shock surfing for a wide range of the control numerical parameters. The plasma dynamics is described by a hybrid (particle-ion-fluid-electron) model. Note that one may need a mesh if modeling with the computation of an electromagnetic field. Our calculations use specified, time-independent electromagnetic fields for the shock, rather than self-consistently generated fields. While a particle-mesh method is a well-verified approach, the CPK method seems to be a good approach for multiscale modeling that includes multiple regions with various particle/fluid plasma behavior. However, the CPK method is still in need of a verification for studying the basic plasma phenomena: particle heating and acceleration by collisionless shocks, magnetic field reconnection, beam dynamics, etc.

Lipatov, Alexander S.

2011-01-01

212

Kinetic theory of acoustic-like modes in nonextensive pair plasmas

NASA Astrophysics Data System (ADS)

The low-frequency acoustic-like modes in a pair plasma (electron-positron or pair-ion) is studied by employing a kinetic theory model based on the Vlasov and Poisson's equations with emphasizing the Tsallis's nonextensive statistics. The possibility of the acoustic-like modes and their properties in both fully symmetric and temperature-asymmetric cases are examined by studying the dispersion relation, Landau damping and instability of modes. The resultant dispersion relation in this study is compatible with the acoustic branch of the experimental data (Oohara et al. in Phys. Rev. Lett. 95:175003, 2005) in which the electrostatic waves have been examined in a pure pair-ion plasma. Particularly, our study reveals that the occurrence of growing or damped acoustic-like modes depends strongly on the nonextensivity of the system as a measure for describing the long-range Coulombic interactions and correlations in the plasma. The mechanism that leads to the unstable modes lies in the heart of the nonextensive formalism yet, the mechanism of damping is the same developed by Landau. Furthermore, the solutions of acoustic-like waves in an equilibrium Maxwellian pair plasma are recovered in the extensive limit ( q?1), where the acoustic modes have only the Landau damping and no growth.

Saberian, E.; Esfandyari-Kalejahi, A.

2014-02-01

213

Anomalous kinetic energy of a system of dust particles in a gas discharge plasma

The system of equations of motion of dust particles in a near-electrode layer of a gas discharge has been formulated taking into account fluctuations of the charge of a dust particle and the features of the nearelectrode layer of the discharge. The molecular dynamics simulation of the system of dust particles has been carried out. Performing a theoretical analysis of the simulation results, a mechanism of increasing the average kinetic energy of dust particles in the gas discharge plasma has been proposed. According to this mechanism, the heating of the vertical oscillations of dust particles is initiated by induced oscillations generated by fluctuations of the charge of dust particles, and the energy transfer from vertical to horizontal oscillations can be based on the parametric resonance phenomenon. The combination of the parametric and induced resonances makes it possible to explain an anomalously high kinetic energy of dust particles. The estimate of the frequency, amplitude, and kinetic energy of dust particles are close to the respective experimental values.

Norman, G. E., E-mail: norman@ihed.ras.ru; Stegailov, V. V., E-mail: stegailov@gmail.com; Timofeev, A. V., E-mail: timofeevalvl@gmail.com [Russian Academy of Sciences, Joint Institute for High Temperatures (Russian Federation)

2011-11-15

214

Concanavalin A-mediated agglutination reactions of hepatoma cells [AH-130F(N)] and isolated liver cells, as well as of plasma membranes prepared from the liver and hepatoma, were investigated kinetically together with the effect of colchicine upon them. Concanavalin A-mediated agglutination of hepatoma cells at 25 degrees proceeded with biphasic kinetics (first and second stages of agglutination), while no appreciable agglutination of liver cells was observed in the presence of concanavalin A. The plasma membranes from the liver and hepatoma cells were similarly agglutinated with concanavalin A at 25 degrees but not at 0 degrees. The concanavalin A-mediated membrane agglutination proceeded with monophasic kinetics and was incomplete. Colchicine inhibited preferentially the second stage of concanavalin A-mediated agglutination of hepatoma cells, but it did not affect the concanavalin A-mediated agglutination of plasma membranes of both types of cells. Images PMID:164656

Nakamura, J; Terayama, H

1975-01-01

215

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

216

Nitric oxide kinetics in the afterglow of a diffuse plasma filament

NASA Astrophysics Data System (ADS)

A suite of laser diagnostics is used to study kinetics of vibrational energy transfer and plasma chemical reactions in a nanosecond pulse, diffuse filament electric discharge and afterglow in N2 and dry air at 100 Torr. Laser-induced fluorescence of NO and two-photon absorption laser-induced fluorescence of O and N atoms are used to measure absolute, time-resolved number densities of these species after the discharge pulse, and picosecond coherent anti-Stokes Raman spectroscopy is used to measure time-resolved rotational temperature and ground electronic state N2(v = 0-4) vibrational level populations. The plasma filament diameter, determined from plasma emission and NO planar laser-induced fluorescence images, remains nearly constant after the discharge pulse, over a few hundred microseconds, and does not exhibit expansion on microsecond time scale. Peak temperature in the discharge and the afterglow is low, T ? 370 K, in spite of significant vibrational nonequilibrium, with peak N2 vibrational temperature of Tv ? 2000 K. Significant vibrational temperature rise in the afterglow is likely caused by the downward N2-N2 vibration-vibration (V-V) energy transfer. Simple kinetic modeling of time-resolved N, O, and NO number densities in the afterglow, on the time scale longer compared to relaxation and quenching time of excited species generated in the plasma, is in good agreement with the data. In nitrogen, the N atom density after the discharge pulse is controlled by three-body recombination and radial diffusion. In air, N, NO and O concentrations are dominated by the reverse Zel'dovich reaction, N + NO ? N2 + O, and ozone formation reaction, O + O2 + M ? O3 + M, respectively. The effect of vibrationally excited nitrogen molecules and excited N atoms on NO formation kinetics is estimated to be negligible. The results suggest that NO formation in the nanosecond pulse discharge is dominated by reactions of excited electronic states of nitrogen, occurring on microsecond time scale.

Burnette, D.; Montello, A.; Adamovich, I. V.; Lempert, W. R.

2014-08-01

217

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.

218

Comparison of hydrodynamic and semi-kinetic treatments for plasma flow along closed field lines

NASA Technical Reports Server (NTRS)

Hydrodynamic and semi-kinetic treatments of plasma flow along closed geomagnetic field lines are compared. The hydrodynamic treatment is based on a simplified 16-moment set of transport equations as the equations for the heat flows are not solved; the heat flows are treated heuristically. The semi-kinetic treatment is based on a particle code. The comparison deals with the distributions of the plasma density, flow velocity, and parallel and perpendicular temperatures as obtained from the two treatments during the various stages of the flow. In the kinetic treatment, the appropriate boundary condition is the prescription of the velocity distribution functions for the particles entering the flux tubes at the ionospheric boundaries; those particles leaving the system are determined by the processes occurring in the flux tube. The prescribed distributions are half-Maxwellian with temperature T(sub 0) and density n(sub 0). In the hydrodynamic model, the prescribed boundary conditions are on density (n(sub 0)), flow velocity (V(sub 0)) and temperature (T(sub 0). It was found that results from the hydrodynamic treatment critically depend on V(sub 0); for early stages of the flow this treatment yields results in good agreement with those from the kinetic treatment, when V(sub 0) = square root of (kT(sub 0)/2 (pi)m), which is the average velocity of particles moving in a given direction for a Maxwellian distribution. During this early stage, the flows developing form the conjugate ionospheres show some distinct transitions. For the first hour or so, the flows are highly supersonic and penetrate deep into the opposite hemispheres, and both hydrodynamics and kinetic treatments yield almost similar features. It is found that during this period heatflow effects are negligibly small. When a flow penetrates deep into the opposite hemisphere, the kinetic treatment predicts reflection and setting up of counterstreaming. In contrast, the hydrodynamic treatment yields a shock in the flow. The reasons for this difference in the two treatments is discussed, showing that in view of the relatively warm ions, the coupling of ion beams and the consequent shock formation in the offequatorial region are not likely due to the enhancements in the beam temperatures. The counterstreaming in the kinetic treatment and the shock in the hydrodynamic treatment first advance upward to the equator and then downward to the ionospheric boundary from where the flow originated. The transit time for this advancement is found to be about 1 hour for the respective models. After 2 hours or so, both models predict that the flows from the ionospheric boundaries are generally subsonic with respect to the local ion-sound speed. At late stages of the flow, when a substantial fraction of ions entering the flux tube begin to return back in the kinetic treatment, the hydrodynamic treatment with the boundary condition V(sub 0) = square root of (kT(sub 0)/2(pi)m) yields an over-refilling, and the choice of V(sub 0) becomes uncertain.

Singh, Nagendra; Wilson, G. R.; Horwitz, J. L.

1993-01-01

219

A Continuum Description of Rarefied Gas Dynamics (I)--- Derivation From Kinetic Theory

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 formulae 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.

Xinzhong Chen; Hongling Rao; Edward A. Spiegel

2001-05-20

220

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

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

2009-06-01

221

Kinetic effects and nonlinear heating in intense x-ray-laser-produced carbon plasmas.

The x-ray laser-matter interaction for a low-Z material, carbon, is studied with a particle-in-cell code that solves the photoionization and x-ray transport self-consistently. Photoionization is the dominant absorption mechanism and nonthermal photoelectrons are produced with energy near the x-ray photon energy. The photoelectrons ionize the target rapidly via collisional impact ionization and field ionization, producing a hot plasma column behind the laser pulse. The radial size of the heated region becomes larger than the laser spot size due to the kinetic nature of the photoelectrons. The plasma can have a temperature of more than 10 000 K (>1eV), an energy density greater than 10^{4} J/cm^{3}, an ion-ion Coulomb coupling parameter ??1, and electron degeneracy ??1, i.e., strongly coupled warm dense matter. By increasing the laser intensity, the plasma temperature rises nonlinearly from tens of eV to hundreds of eV, bringing it into the high energy density matter regime. The heating depth and temperature are also controllable by changing the photon energy of the incident laser light. PMID:25493733

Sentoku, Y; Paraschiv, I; Royle, R; Mancini, R C; Johzaki, T

2014-11-01

222

Kinetic effects and nonlinear heating in intense x-ray-laser-produced carbon plasmas

NASA Astrophysics Data System (ADS)

The x-ray laser-matter interaction for a low-Z material, carbon, is studied with a particle-in-cell code that solves the photoionization and x-ray transport self-consistently. Photoionization is the dominant absorption mechanism and nonthermal photoelectrons are produced with energy near the x-ray photon energy. The photoelectrons ionize the target rapidly via collisional impact ionization and field ionization, producing a hot plasma column behind the laser pulse. The radial size of the heated region becomes larger than the laser spot size due to the kinetic nature of the photoelectrons. The plasma can have a temperature of more than 10 000 K (>1 eV ), an energy density greater than 104 J /cm3 , an ion-ion Coulomb coupling parameter ? ?1 , and electron degeneracy ? ?1 , i.e., strongly coupled warm dense matter. By increasing the laser intensity, the plasma temperature rises nonlinearly from tens of eV to hundreds of eV, bringing it into the high energy density matter regime. The heating depth and temperature are also controllable by changing the photon energy of the incident laser light.

Sentoku, Y.; Paraschiv, I.; Royle, R.; Mancini, R. C.; Johzaki, T.

2014-11-01

223

Jovian Plasma Torus Interaction with Europa: 3D Hybrid Kinetic Simulation. First results

NASA Technical Reports Server (NTRS)

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 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 etal.,2007;Shematovichetal.,2005). In contrast to previous approaches with MHD simulations, the hybrid model allows us to fully take into account the finite gyro radius 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).Non-thermal distributions of upstream plasma will be addressed in future work. Photoionization,electron-impact ionization, charge exchange and collisions between the ions and neutrals are also included in our model. We consider two models for background plasma:(a) with O(++) ions; (b) with O(++) and S(++) ions. The majority of O2 atmosphere is thermal with an extended cold population (Cassidyetal.,2007). A few first simulations already include an induced magnetic dipole; however, several important effects of induced magnetic fields arising from oceanic shell conductivity will be addressed in later work.

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

2010-01-01

224

Theoretical Modeling of Radiation-driven Atomic Kinetics of a Neon Photoionized Plasma

NASA Astrophysics Data System (ADS)

We report on a theoretical study on atomic kinetics modeling of a photoionized neon plasma at conditions relevant to laboratory experiments performed at the Z-machine in Sandia National Laboratories. We describe an atomic kinetics model and code, ATOKIN, that was developed and used to compute the atomic level population distribution. The study includes atomic level sensitivity with respect to energy level structure, radiation and transient effects, electron temperature and x-ray drive sensitivity and an idea for electron temperature extraction from a level population ratio. The neon atomic model considers several ionization stages of highly-charged neon ions as well as a detailed structure of non-autoionizing and autoionizing energy levels in each ion. In the energy level sensitivity study, the atomic model was changed by adding certain types of energy levels such as singly-excited, auto-ionizing doubly-excited states. Furthermore, these levels were added ion by ion for the most populated ions. Atomic processes populating and de-populating the energy levels consider photoexcitation and photoionization due to the external radiation flux, and spontaneous and collisional atomic processes including plasma radiation trapping. Relevant atomic cross sections and rates were computed with the atomic structure and scattering FAC code. The calculations were performed at constant particle number density and driven by the time-histories of temperature and external radiation flux. These conditions were selected in order to resemble those achieved in photoionized plasma experiments at the Z facility of Sandia National Laboratories. For the same set of time histories, calculations were done in a full time-dependent mode and also as a sequence of instantaneous, steady states. Differences between both calculations are useful to identify transient effects in the ionization and atomic kinetics of the photoionized plasma, and its dependence on the atomic model and plasma environmental conditions. We also calculated transmission spectra in an effort to identify time-dependent effects in observed spectral features. Furthermore, all the steady state and time-dependent calculations were performed for different electron temperature histories to investigate electron temperature effects in the same way transient effects were examined. The idea for electron temperature extraction based on the population ratio of two energy levels close in energy was investigated after preliminary estimations revealed evidence of dominant electron collisional excitation and de-excitation over photo-excitation and spontaneous radiative decay between the ground state, 1s22 s, and the first excited state, 1s22 p, levels of Li-like Ne. Since the populations of these levels were determined from the analysis of transmission spectra, it was then possible to estimate the temperature via a Boltzmann factor. Further studies were performed for various plasma conditions such as temperature and density in order to confirm the reliability of the method. Calculations were performed for a sequence of steady states and in a full time-dependent mode. Finally, the instantaneous spectra was integrated over several time intervals in order to test the method on conditions similar to those of laboratory experiments.

Durmaz, Tunay

225

Properties of solitary kinetic Alfvén wave in a plasma with non-extensive electrons

NASA Astrophysics Data System (ADS)

The properties of solitary kinetic Alfvén waves (SKAWs) in a finite ? plasma with three dimensional non-extensive electrons are investigated. Numerical results show that there only exists sub-Alfvénic hump type SKAW. The down limit of the Alfvén Mach number Mz for the existence of SKAW increases with the increase of ?. Whereas, it varies non-monotonously with respect to electron nonextensive parameter q for a given ?. In the range of Mz where SKAWs exist for different values of q, a bigger q results in a denser soliton structure, making the magnitude of the static electric field along the background magnetic field enhanced. However, the dependence of the amplitudes of the perpendicular magnetic and electric field on q is non-monotonous.

Liu, Y.; Shi, Z. F.; Han, Y.; Dai, B.

2015-03-01

226

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

227

Description of time-varying desorption kinetics. Release of naphthalene from contaminated soils

Release rates of naphthalene from suspensions of freshly contaminated (days to weeks) and aged (approximately 30 years) soil samples were obtained using a gas purge method. A continuously increasing resistance to desorption was observed with increasing purge time. Initial desorption rates were similar to those estimated using available empirical relationships, but subsequent desorption rates were lower by more than 1 order of magnitude. A model incorporating a continuum of compartments with a gamma ([Gamma]) distribution of rate coefficients was postulated to describe the experimental data. An analytical equation with two adjustable parameters was obtained for the mass fraction desorbed. Release profiles with this [open quotes][Gamma] model[close quotes] were able to describe the experimental release profiles for long term desorption experiments. An implication of the gamma model is that increased incubation time will allow organic compounds to be sorbed to compartments or regions in the sorbent that exhibit slow adsorption/desorption kinetics. This has important implications for the fate and remediation of sites that have been contaminated with hydrophobic organic compounds for extended time periods. 31 refs., 6 figs., 3 tabs.

Connaughton, D.F.; Stedinger, J.R.; Lion, L.W.; Shuler, M.L. (Cornell Univ., Ithaca, NY (United States))

1993-11-01

228

Kinetic simulation of the O-X conversion process in dense magnetized plasmas

NASA Astrophysics Data System (ADS)

One scheme for heating a dense magnetized plasma core, such as in a tokamak, involves launching an ordinary (O) electromagnetic wave at the low density edge. It is converted to a reflected extraordinary (X) electromagnetic wave under certain conditions, and then transformed into an electron Bernstein wave able to reach high density regions inaccessible to most other waves. The O-X mode conversion is important in heating and diagnostic processes in different devices such as tokamaks, stellarators, and some types of pinches. The goal of this study has been to demonstrate that the kinetic particle-in-cell (PIC) scheme is suitable for modeling the O-X conversion process as the first step toward a more complete simulation of O-X-B heating. The O-X process is considered and simulated with a kinetic particle model for parameters of the TJ-II stellarator using the PIC code, XOOPIC. This code is able to model the non-monotonic density and the magnetic profile of the TJ-II stellarator. It can also statistically represent the self-consistent distribution function of the plasma, which has not been possible in previous fluid models. By considering the electric and magnetic components of launched and reflected waves, the O-mode and X-mode waves can be detected, and the O-X conversion can be demonstrated. In this work, the optimum angle for conversion efficiency, as predicted by the previous theory and experimentally confirmed, is used. Via considering the power of the launched O-mode wave and the converted X-mode wave, the efficiency of 63% for O-X conversion for the optimum theoretical launch angle of 47? is obtained, which is in good agreement with efficiencies computed via full-wave simulations.

Ali Asgarian, M.; Verboncoeur, J. P.; Parvazian, A.; Trines, R.

2013-10-01

229

in Gas Discharges Vladimir I. Kolobov, Senior Member, IEEE, and Robert R. Arslanbekov Abstract--We review the state-of-the-art for the simulation of electron kinetics in gas discharges based on the numerical simulation of the electron distribution function in collisional gas discharge plasmas. We illustrate

Kaganovich, Igor

230

2D Axisymmetric Coupled CFD-kinetics Modeling of a Nonthermal Arc Plasma Torch for Diesel Fuel

. In the first case, diesel fuel reacts with air while in the second case it reacts with diesel engine exhaust1 2D Axisymmetric Coupled CFD-kinetics Modeling of a Nonthermal Arc Plasma Torch for Diesel Fuel-assisted diesel fuel reformer developed for two different applications: (i) onboard H2 production for fuel cell

Boyer, Edmond

231

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

232

KINETIC PLASMA TURBULENCE IN THE FAST SOLAR WIND MEASURED BY CLUSTER

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{sub sc}, wave polarization property is analyzed in the plane perpendicular to k. Magnetic fluctuations have {delta}B > {delta}B{sub Parallel-To} (here the Parallel-To and refer to the background magnetic field B{sub 0}). The wave magnetic field has right-handed polarization at propagation angles {theta}{sub kB} < 90 Degree-Sign and >90 Degree-Sign . The magnetic field in the plane perpendicular to B{sub 0}, however, has no clear sense of a dominant polarization but local rotations. We discuss the merits and limitations of linear kinetic Alfven waves (KAWs) and coherent Alfven 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 Alfven vortices at ion kinetic scales.

Roberts, O. W.; Li, X. [Institute of Mathematics and Physics, Aberystwyth University, Aberystwyth, Ceredigion SY23 3BZ (United Kingdom); Li, B., E-mail: xxl@aber.ac.uk [School of Space Science and Physics, Shandong University, Weihai 246209 (China)

2013-05-20

233

Implementation of the Kinetic Plasma Code with Locally Recursive non-Locally Asynchronous Algorithms

NASA Astrophysics Data System (ADS)

Numerical simulation is presently considered impractical for several relevant plasma kinetics problems due to limitations of computer hardware even with the use of supercomputers. To overcome the existing limitations it is suggested to develop algorithms which would effectively utilize the computer memory subsystem hierarchy to optimize the dependency graph traversal rules. The ideas for general cases of numerical simulation and implementation of such algorithms to particle-in-cell code is discussed in the paper. This approach enables the simulation of previously unaccessible for modeling problems and the execution of series of numerical experiments in reasonable time. The latter is demonstrated on a multiscale problem of the development of filamentation instability in laser interaction with overdense plasma. One variant of the simulation with parameters typical for simulations on supercomputers is performed with the use of one cluster node. The series of such experiments revealed the dependency of energy loss on incoming laser pulse amplitude to be nonmonotonic and reach over 4%, an interesting result for research of fast ignition concept.

Perepelkina, A. Yu; Levchenko, V. D.; Goryachev, I. A.

2014-05-01

234

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

235

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

236

NASA Astrophysics Data System (ADS)

During normal and disruptive operations in tokamak devices the escaped core plasma particles are a potential threat to the divertor and nearby component lifetime as well as plasma contamination. Comprehensive enhanced physical and numerical models are developed and implemented in the upgraded High Energy Interaction with General Heterogeneous Target Systems (HEIGHTS) package to accurately predict the impact of the escaped particles on plasma-facing and nearby components. An ab initio Monte Carlo-based kinetic model of the escaping core particles is developed for integration with the magnetohydrodynamic (MHD) models of the initiated edge plasma where the escaping particles are used as an input volume source. The paper describes details of the 3D Monte Carlo kinetic model, validation and benchmarking and simulation results for both National Spherical Torus Experiment and ITER devices using actual reactor design and magnetic configurations. The simulation results are being implemented self-consistently with various HEIGHTS models that include surface erosion, divertor plasma generation, plasma MHD evolution, heat conduction and detailed photon transport of line and continuum radiation.

Sizyuk, V.; Hassanein, A.

2013-07-01

237

NASA Astrophysics Data System (ADS)

The influence of current-aligned instabilities on magnetic reconnection is investigated using state-of-the-art fully kinetic simulations with boundary conditions mimicking Magnetic Reconnection eXperiment (MRX). MRX is a controlled, well-diagnosed reconnection experiment that provides a unique opportunity to perform detailed comparison between simulations and observations in ways that are not as easily possible with spacecraft data. At the same time, simulations help extrapolate the experimental results to the parameter regimes (e.g. collisionless regimes) not accessible in the real device. We present the first results from 3D simulations that have been recently carried out as a part of the open science campaign on Roadrunner, the world’s first petascale computer. The simulations were performed using a high-performance Particle-In-Cell code VPIC, which utilizes a Monte-Carlo model for Coulomb collisions thus allowing regimes with arbitrary collisionality to be studied [4]. Simulations in MRX geometry are compared to those performed in large-scale collisionless systems with open boundary conditions. Fluctuations with characteristic frequency and wavenumbers in the lower-hybrid range are observed in both geometries and in case of MRX simulations compare well with the ones detected in MRX. The possible role of these fluctuations in global reconnection dynamics is discussed. [1] T. Carter, et al., Phys. Plasmas, 9, 3272, 2002 [2] H. Ji, et al., Phys. Rev. Letters 92, 115001, 2004 [3] S. Dorfman, et al., Phys. of Plasmas 15, 102107, 2008 [4] W. Daughton et al. Phys. Plasmas 16, 072117, 2009

Roytershteyn, V.; Daughton, W. S.; Yin, L.; Albright, B. J.; Bowers, K.; Dorfman, S.; Ji, H.; Yamada, M.; Karimabadi, H.

2009-12-01

238

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

NASA Astrophysics Data System (ADS)

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 and experimental techniques are developed utilizing the Lagrangian point of view with the ultimate goal of a deeper understanding of flow dynamics. In this tutorial review we report on recent progress made in the analysis of compressible, more or less perfect flows such as plasmas and dilute gases. The equations of motion are exploited to get further insight into the formation and evolution of coherent structures, which often exhibit a singular or collapse type behavior occurring in finite time. It is argued that this technique of solution has a broad applicability due to the simplicity and generality of equations used. The focus is on four different topics, the physics of which being governed by simple fluid equations subject to initial and/or boundary conditions. Whenever possible also experimental results are mentioned. In the expansion of a semi-infinite plasma into a vacuum the energetic ion peak propagating supersonically towards the vacuum-as seen in laboratory experiments-is interpreted by means of the Lagrangian fluid description as a relic of a wave breaking scenario of the corresponding inviscid ion dynamics. The inclusion of viscosity is shown numerically to stabilize the associated density collapse giving rise to a well defined fast ion peak reminiscent of adhesive matter. In purely convection driven flows the Lagrangian flow velocity is given by its initial value and hence the Lagrangian velocity gradient tensor can be evaluated accurately to find out the appearance of singularities in density and vorticity and the emergence of new structures such as wavelets in one-dimension (1D). In cosmology referring to the pancake model of Zel'dovich and the adhesion model of Gurbatov and Saichev, both assuming a clumping of matter at the intersection points of fluid particle trajectories (i.e. at the caustics), the foam-like large-scale structure of our Universe observed recently by Chandra X-ray observatory may be explained by the 3D convection of weakly interacting dark matter. Recent developments in plasma and nanotechnology-the miniaturization and fabrication of nanoelectronic devices being one example-have reinforced the interest in the quasi-ballistic electron transport in diodes and triodes, a field which turns out to be best treated by the Lagrangian fluid description. It is shown that the well-known space-charge-limited flow given by Child-Langmuir turns out to be incorrect in cases of finite electron injection velocities at the emitting electrode. In that case it is an intrinsic bifurcation scenario which is responsible for current limitation rather than electron reflection at the virtual cathode as intuitively assumed by Langmuir. The inclusion of a Drude friction term in the electron momentum equation can be handled solely by the Lagrangian fluid description. Exploiting the formula in case of field emission it is possible to bridge ballistic and drift-dominated transport. Furthermore, the transient processes in the electron transport triggered by the switching of the anode potential are shown to be perfectly accounted for by means of the Lagrangian fluid description. Finally, by use of the Lagrangian ion fluid equations in case of a two component, current driven plasma we derive a system of two coupled scalar wave equations which involve the specific volume of ions and electrons, respectively. It has a small amplitude strange soliton solution with unusual scaling properties. In case of charge neutrality the existence of two types of collapses are predicted, one being associated with a density excavation, the other one with a density clumping as in the laser induced ion expansion problem and in the cosmic sticking matter problem. Howev

Schamel, Hans

2004-03-01

239

NASA Technical Reports Server (NTRS)

Laser wave mixing is presented as an effective technique for spatially resolved kinetic temperature measurements in an atmospheric-pressure radio-frequency inductively-coupled plasma. Measurements are performed in a 1 kW, 27 MHz RF plasma using a continuous-wave, tunable 811.5-nm diode laser to excite the 4s(sup 3)P2 approaches 4p(sup 3)D3 argon transition. Kinetic temperature measurements are made at five radial steps from the center of the torch and at four different torch heights. The kinetic temperature is determined by measuring simultaneously the line shape of the sub-Doppler backward phase-conjugate degenerate four-wave mixing and the Doppler-broadened forward-scattering degenerate four-wave mixing. The temperature measurements result in a range of 3,500 to 14,000 K+/-150 K. Electron densities measured range from 6.1 (+/-0.3) x 10(exp 15)/cu cm to 10.1 (+/-0.3) x 10(exp 15)/cu cm. The experimental spectra are analyzed using a perturbative treatment of the backward phase-conjugate and forward-geometry wave-mixing theory. Stark width is determined from the collisional broadening measured in the phase-conjugate geometry. Electron density measurements are made based on the Stark width. The kinetic temperature of the plasma was found to be more than halved by adding deionized water through the nebulizer.

Schafer, Julia; Lyons, Wendy; Tong, WIlliam G.; Danehy, Paul M.

2008-01-01

240

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

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

241

Background For many microbial processes, the complexity of the metabolisms and the responses to transient and realistic conditions are difficult to capture in mechanistic models. The cells seem to have an innate intelligence that enables them to respond optimally to environmental changes. Some "intelligent" models have therefore been proposed and compared with a mechanistic model for fed-batch cultures of Ralstonia eutropha. Results Two kinds of models have been proposed to describe such cellular behavior. Cybernetic models are derived through postulates of cellular intelligence and memory, and neural models use artificial intelligence through neural networks. Some competing models of both kinds have been compared for their ability to portray and optimize the synthesis of poly-?-hydroxybutyrate by Ralstonia eutropha in fed-batch cultures with finite dispersion. Neural models enabled the formation of more of the polymer than cybernetic models, with lesser utilization of the carbon and nitrogen substrates. Both types of models were decidedly superior to a mechanistic model used as a reference, thus supporting the value of intelligent descriptions of microbial kinetics in incompletely dispersed bioreactors. Conclusion Neural and cybernetic models describe and optimize unsteady state fed-batch microbial reactors with finite dispersion more effectively than mechanistic models. However, these "intelligent" models too have weaknesses, and hence a hybrid approach combining such models with some mechanistic features is suggested. PMID:17686143

Patnaik, Pratap R

2007-01-01

242

Kinetics of plasma membrane and mitochondrial alterations in cells undergoing apoptosis

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

243

NASA Technical Reports Server (NTRS)

This paper describes the linear kinetic theory of electrostatic instabilities driven by a density gradient drift and a magnetic-field-aligned current in a plasma with weak charged neutral collisions. The configuration is that of a uniform magnetic field B, a weak, uniform density gradient in the x direction and a weak, uniform electric field in the z direction. Collisions are represented by the BGK model. The transition from the (kinetic) universal density drift instability to the (fluidlike) current convective instability is studied in detail, and the short wavelength properties of the latter mode are investigated.

Gary, S. P.

1984-01-01

244

Plasma disposition kinetics of moxidectin after subcutaneous administration to pregnant sheep.

The plasma kinetic profile of moxidectin (MXD) in ewes during the last third of pregnancy was studied after the subcutaneous dose of 0.2 mg/kg of body weight (bw). Two groups of sheep (n = 7) that were equally balanced in body weight were used. Group I (control) was maintained unmated, while Group II (pregnant) was estrous-synchronized and mated with fertile rams. Both groups were maintained under similar conditions regarding management and feeding. When the ewes from Group II fulfilled 120 days of pregnancy, both groups were treated with a subcutaneous injection of 0.2 mg of MXD/kg bw. Blood samples were collected at different set times between 1 h and 40 days post-treatment. After plasma extraction and derivatization, the samples were analyzed using high-performance liquid chromatography with fluorescence detection. A noncompartmental pharmacokinetic analysis was performed, and the data were compared using Student's t-test. The mean pharmacokinetic parameters, including Cmax , Tmax , and the area under the concentration-time curve (AUC), were similar for both groups of sheep. The average of elimination half-life was significantly lower (P = 0.0023) in the pregnant (11.49 ± 2.2 days) vs. the control (17.89 ± 4.84 days) sheep. Similarly, the mean residence time (MRT) for the pregnant group (20.6 ± 3.8 days) was lower (P = 0.037) than that observed in the control group (27.4 ± 9.1 days). It is concluded that pregnancy produces a significant decrease in mean values of half-life of elimination of MXD, indicating that pregnancy can increase the rate of elimination of the drug reducing their permanence in the body. PMID:24731163

Pérez, R; Núñez, M J; Palma, C; Riquelme, J; Arboix, M

2014-12-01

245

NASA Astrophysics Data System (ADS)

The excitation of collective instabilities by super-thermal particles in hot plasmas and the related transport processes attract increasing interest due to their fundamental challenges for theoretical models and their practical importance for burning fusion plasmas. In fact, the physics of a self-heated thermonuclear plasma due to fusion-born 3.5 MeV ?-particles is one of the most important outstanding fundamental research topics on the way to a fusion power plant with magnetic confinement. Within the last 10 years significant advances on both the theoretical and the experimental sides have been made leading to a more detailed and quantitative understanding of fast-particle-driven instabilities. On the theoretical side, the crucial step was to move from fluid models for the plasma background with a hybrid kinetic expression for the energetic particles to a fully kinetic model for all the plasma species, i.e. background ions, background electrons, and fast ions. This improvement allows one to describe consistently the resonant interaction between global plasma waves such as shear Alfvén and Alfvén-acoustic waves, and the particles via Landau damping, i.e. the dynamics parallel to the magnetic background field. Also, mode conversion mechanisms require the inclusion of background ion scales in a kinetic, non-perturbative way. This accurate treatment of the plasma background leads not only to changes in the linear mode properties such as frequency, growth/damping rate, and mode structure but also influences the non-linear dynamics. Due to major advances, innovations and installation of diagnostics in present day experiments, this comparison can be carried out in a more detailed and comprehensive way than a few years ago. For example, the measurement of damping rates via active external antennas, the imaging of 2D mode structures via electron-cyclotron-emission spectroscopy, and the direct detection of escaping fast ions allow to diagnose various kinetic features of the plasma modes that are responsible for the transport of energetic particles. Furthermore, the fast particle distribution function itself can also be measured with much greater confidence. Therefore, the new physics accessible due to a more comprehensive model and numerical implementation can be directly verified and validated with experimental data.

Lauber, Philipp

2013-12-01

246

Pegasus: A new hybrid-kinetic particle-in-cell code for astrophysical plasma dynamics

NASA Astrophysics Data System (ADS)

We describe Pegasus, a new hybrid-kinetic particle-in-cell code tailored for the study of astrophysical plasma dynamics. The code incorporates an energy-conserving particle integrator into a stable, second-order-accurate, three-stage predictor-predictor-corrector integration algorithm. The constrained transport method is used to enforce the divergence-free constraint on the magnetic field. A ?f scheme is included to facilitate a reduced-noise study of systems in which only small departures from an initial distribution function are anticipated. The effects of rotation and shear are implemented through the shearing-sheet formalism with orbital advection. These algorithms are embedded within an architecture similar to that used in the popular astrophysical magnetohydrodynamics code Athena, one that is modular, well-documented, easy to use, and efficiently parallelized for use on thousands of processors. We present a series of tests in one, two, and three spatial dimensions that demonstrate the fidelity and versatility of the code.

Kunz, Matthew W.; Stone, James M.; Bai, Xue-Ning

2014-02-01

247

In vitro kinetics of nerve agent degradation by fresh frozen plasma (FFP).

Great efforts have been undertaken in the last decades to develop new oximes to reactivate acetylcholinesterase inhibited by organophosphorus compounds (OP). So far, a broad-spectrum oxime effective against structurally diverse OP is still missing, and alternative approaches, e.g. stoichiometric and catalytic scavengers, are under investigation. Fresh frozen plasma (FFP) has been used in human OP pesticide poisoning which prompted us to investigate the in vitro kinetics of OP nerve agent degradation by FFP. Degradation was rapid and calcium-dependent with the G-type nerve agents tabun, sarin, soman and cyclosarin with half-lives from 5 to 28 min. Substantially longer and calcium-independent degradation half-lives of 23-33 h were determined with the V-type nerve agents CVX, VR and VX. However, at all the tested conditions, the degradation of V-type nerve agents was several-fold faster than spontaneous hydrolysis. Albumin did not accelerate the degradation of nerve agents. In conclusion, the fast degradation of G-type nerve agents by FFP might be a promising tool, but would require transfusion shortly after poisoning. FFP does not seem to be suitable for detoxifying relevant agent concentrations in case of human poisoning by V-type nerve agents. PMID:24057572

Wille, Timo; Thiermann, Horst; Worek, Franz

2014-02-01

248

Shear viscosity of the quark-gluon plasma in a kinetic theory approach

One of the main results of heavy ions collision (HIC) at relativistic energy experiments is the very small shear viscosity to entropy density ratio of the Quark-Gluon Plasma, close to the conjectured lower bound ?/s=1/4? for systems in the infinite coupling limit. Transport coefficients like shear viscosity are responsible of non-equilibrium properties of a system: Green-Kubo relations give us an exact expression to compute these coefficients. We compute shear viscosity numerically using Green-Kubo relation in the framework of Kinetic Theory solving the relativistic transport Boltzmann equation in a finite box with periodic boundary conditions. We investigate a system of particles interacting via anisotropic and energy dependent cross-section in the range of temperature of interest for HIC. Green-Kubo results are in agreement with Chapman-Enskog approximation while Relaxation Time approximation can underestimates the viscosity of a factor 2. The correct analytic formula for shear viscosity can be used to develop a transport theory with a fixed ?/s and have a comparison with physical observables like elliptic flow.

Puglisi, A.; Plumari, S.; Scardina, F.; Greco, V. [Department of Physics and Astronomy, University of Catania, Via S. Sofia 64, I-95125 Catania, Italy and Laboratorio Nazionale del Sud, INFN-LNS, Via S. Sofia 63, I-95125 Catania (Italy)

2014-05-09

249

In this paper we show that identical collision terms are known by different names in gaseous plasmas and solids. Method used by plasma physicists and the one used by solid state physicists to solve Kinetic equation are also exactly same but they are also known by different names. In fact the physical explanation of damping of plasma Waves given by plasma physicists is quite similar to that given by solid state physicists to explain the absorption of acoustic waves in solids.

Sharma, S. K. [Department of Physics, Dilla University, P.O.Box 419, Dilla (Ethiopia)

2010-11-23

250

Kinetic Study of the Solid-State Transformation of Vacuum-Plasma-Sprayed Ti-6Al-4V Alloy

NASA Astrophysics Data System (ADS)

Because of the nature of the plasma spraying process, the physical and mechanical properties of vacuum-plasma-sprayed structures of Ti-6Al-4V alloy are completely different from those of conventionally manufactured alloys such as bulk materials from casting and forging. To obtain desired mechanical and physical properties, vacancy and internal defects must be reduced, splat boundaries must be eliminated, and optimal phase compositions should be obtained through postdeposition heat treatments. To determine appropriate heat treatment processes, one needs to study the kinetic behavior of the as-sprayed microstructure at elevated temperatures. In the current study, the kinetics of the solid transformations found in Ti-6Al-4V alloys produced during the vacuum plasma spraying process was studied based on the Johnson-Mehl-Avrami theory. For the kinetic behavior of this alloy, the nonconstant temperature dependence of the transformation rate constant exhibits an irregularity at 900 °C, marking a change in the transformation mechanism. For the lower-temperature (<900 °C) curves, the constant gradient indicates a lack of change in the transformation mechanism, including homogeneous nucleation, with growth of ? phase. For higher temperatures (>900 °C), a gradient change indicates a change in the transformation mechanism. The first mechanism was the formation of ?-phase grain boundary, and the second mechanism was ?-plate nucleation and growth from grain boundaries. The value of the transformation rate constant in the kinetics study of as-sprayed Ti-6Al-4V alloy was much higher than for material produced by the casting method. Using the results obtained from the kinetics of the phase transformation at different constant temperatures, a time-temperature-transformation (TTT) diagram for as-sprayed Ti-6Al-4V alloy was developed.

Salimijazi, H. R.; Mousavi, Z. A.; Golozar, M. A.; Mostaghimi, J.; Coyle, T.

2014-01-01

251

Large amplitude kinetic Alfv'en waves (deltaB\\/B ˜1% > k\\/k) are generated in the Large Plasma Device (LAPD) at UCLA using loop antennas. Substantial electron heating is observed, localized to the wave current channels. The Poynting flux associated with the Alfv'en waves is substantial and the observed heating may be at least in part due to collisional and Landau damping of

T. A. Carter; D. W. Auerbach; B. T. Brugman

2007-01-01

252

NASA Astrophysics Data System (ADS)

In terms of the Vlasov-Maxwell kinetic approach we consider analytically the global Chapman- Ferraro problem (CFP) of inductive generation by the solar wind plasma flow of 3D magnetotail/solar streamer (M/S) structures in the process of electromagnetic (e.m.) interaction of the flow with the magnetized region. The input undisturbed flow is a hot collisionless plasma with an isotropic velocity distribution function (VDF) of any form, characterized by the introduced dimensionless kinetic parameter G. The 3D analytical stationary solution and set of new CFP parameters are a result of the classical simplification method based on separation of plasma particles in the velocity phase space into "trapped" and "flyby" groups that interact electromagnetically. The "flyby" particles form the "flowing media" with large scale kinetic inductive e.m. plasma eigenmodes disturbing the plasma VDF. The trapped particles in the magnetic dipole field form the prescribed "magnetic quasiparticle". The quasiparticle is described as stationary 3D spatial magnetization formed by the superposition of dipole like magnetization with N and S poles and toroidal circular magnetization without the poles. The spatial scale of the "quasiparticle", the ratio of the integral currents in the dipole and the toroidal components, and angle of mutual orientation of the components are the "quasiparticle" parameters. The "quasiparticle" models magnetic loop, sigma and helmet magnetoactive structures for the Sun and models circular and partial ring currents in the internal magnetosphere. The "quasiparticle" induces downflow the elongated quasicylindrical "dipole"-like and "toroidal"-like 3D M/S structures with fine multyrope and multicurrent sheets forming magnetic reconnection topology inside described by the package of inductive modes. Currents in the structures have resistive and diamagnetic components, which are related with "thin" structures inside "thick" current systems, respectively. Current scales are related with two different e.m. plasma kinetic spatial dispersion scales induced by the flow. They are defined by two dimensionless parameters of the plasma flow anisotropy. The anomalous skin scale defined via the "flow pulse" anisotropy stipulated by "resonant" particles which, in turn, provide resistivity in the flow. The magnetic Debye skin scale defined via the "flow energy" anisotropy formed by "nonresonant" particles which provide the diamagnetizm. We obtain these effects only in the subthermal (with respect to electrons) regime of the flow velocity. Squared ratio of two scales defines "quality" G equal to cotangent of the "losses angle" which measures the flow reactivity also and G can be a new characteristic for space weather. The value of G depends only on the form factor of the VDF and determines topology of the M/S states. We obtain the asymmetric "the resistive elongated state" for M/S when G is small with possibility of adiabatic transition to symmetric "the diamagnetic dipolized state" when G is large. Nonadiabatic transitions can be considered as substorm/CME relaxation substructure in the M/S structures.

Gubchenko, Vladimir

253

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

254

Studies of ion kinetic effects during the shock-convergence phase of inertial confinement fusion (ICF) implosions and magnetic reconnection in strongly-driven, laser-produced plasmas have been facilitated by the use of ...

Rosenberg, Michael Jonathan

2014-01-01

255

We discuss complete theory of spin-1/2 electron-positron quantum plasmas, when electrons and positrons move with velocities mach smaller than the speed of light. We derive a set of two fluid quantum hydrodynamic equations consisting of the continuity, Euler, spin (magnetic moment) evolution equations for each species. We explicitly include the Coulomb, spin-spin, Darwin and annihilation interactions. The annihilation interaction is the main topic of the paper. We consider contribution of the annihilation interaction in the quantum hydrodynamic equations and in spectrum of waves in magnetized electron-positron plasmas. We consider propagation of waves parallel and perpendicular to an external magnetic field. We also consider oblique propagation of longitudinal waves. We derive set of quantum kinetic equations for electron-positron plasmas with the Darwin and annihilation interactions. We apply the kinetic theory for the linear wave behavior in absence of external fields. We calculate contribution of the Darwin and annihilation interactions in the Landau damping of the Langmuir waves. We should mention that the annihilation interaction does not change number of particles in the system. It does not related to annihilation itself, but it exists as a result of interaction of an electron-positron pair via conversion of the pair into virtual photon. A pair of the non-linear Schrodinger equations for electron-positron plasmas including the Darwin and annihilation interactions. Existence of conserving helicity in electron-positron quantum plasmas of spinning particles with the Darwin and annihilation interactions is demonstrated. We show that annihilation interaction plays an important role in quantum electron-positron plasmas giving contribution of the same magnitude as the spin-spin interaction.

Pavel A. Andreev

2014-04-18

256

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

257

NASA Astrophysics Data System (ADS)

In plasmas of atmospheric gases, the kinetics of some aliphatic organic molecules belonging to the hydrocarbons (propene, propane), aldehydes (acetaldehyde) and ketones (acetone) families were studied using a photo-triggered discharge (homogeneous plasma). It was shown that quenchings of N2 metastable states, A\\,^{3}\\Sigma_{u}^{+} and the group of singlets a'\\,^{1}\\Sigma_{u}^{-} , a 1?g and w 1?u, are important processes for the decomposition of such molecules. It plays a fundamental role in the nitrogen plasma, but it is also present in air. At low temperature, the oxidation reactions by the oxygen atom or by the hydroxyl radical are not always sufficiently effective to induce an increase of the molecule decomposition when oxygen is added to the nitrogen/organic mixture. For most cases, quenching processes appear purely dissociative. However, recent results obtained for propene lead to the conclusion that a non-dissociative exit route could exist. The quenching of the singlet states induces a break of the double bound C = O for the acetaldehyde and acetone molecules. Some kinetic analogies appear between filamentary and homogeneous plasmas, which could be very useful to get a comprehensive understanding of the physico-chemical processes in dielectric barriers or corona discharges used for various applications.

Pasquiers, S.; Blin-Simiand, N.; Magne, L.

2013-12-01

258

NASA Technical Reports Server (NTRS)

The degree of toroidal symmetry of the plasma, the number of midplane electrode rings, the configuration of electrode rings, and the location of the diagnostic instruments with respect to the electrode rings used to generate the plasma are discussed. Impurities were deliberately introduced into the plasma, and the effects of the impurity fraction on ion kinetic temperature and electron number density were observed. It is concluded that, if necessary precautions are taken, the plasma communicates extremely well along the magnetic field lines and displays a high degree of symmetry from sector to sector for a wide range of electrode ring configurations and operating conditions. Finally, some characteristic data taken under nonoptimized conditions are presented, which include the highest electron number density and the longest particle containment time (1.9 msec) observed. Also, evidence from a paired comparison test is presented which shows that the electric field acting along the minor radius of the toroidal plasma improves the plasma density and the calculated containment time more than an order of magnitude if the electric field points inward, relative to the values observed when it points (and pushes ions) radially outward.

Roth, J. R.

1977-01-01

259

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

260

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

261

Kinetic simulation of radio-frequency driven plasmas in He/O2 mixtures at atmospheric pressure

NASA Astrophysics Data System (ADS)

Over the past years microplasma research gained a lot of attention both from an experimental and theoretical perspective. One particular type of microplasma sources that shows a variety of interesting physics and applications are radio-frequency plasma jets. This contribution investigates radio-frequency driven plasmas with an electrode gap of below 1 mm. The discharge is operated in a mixture of He and O2 (0.5 percent) at atmospheric pressure. A typical simulation of this kind of discharges is based on the hydrodynamic approximation of the relevant species. Sometimes this approach is extended by a quasi-kinetic treatment of the fast electron component (hybrid codes). Still certain kinetic effects are neglected in both of these methods. In this work a 1d self-consistent Particle-in-Cell model of the discharge is developed, to investigate kinetic effects and to verify the validity of the corresponding fluid model. All the relevant species and reactions regarding the underlying chemistry are taken into account by means of a Monte Carlo Collision model.

Eremin, Denis; Hemke, Torben; Brinkmann, Ralf Peter; Mussenbrock, Thomas

2011-11-01

262

Complete Spectrum of Kinetic Eigenmodes for Plasma Oscillations ... http://www.aps.org/meet/DPP03 Southeast Exhibit Hall, ACC [FP1.121] Complete Spectrum of Kinetic Eigenmodes for Plasma Oscillations are smooth and comprise a complete discrete spectrum, play the same role for weakly collisional plasmas

Ng, Chung-Sang

263

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

264

A fluid description for the discharge equilibrium of a divergent electron cyclotron resonance, Yorktown Heights, New York IO598 (Received 18 March 1992; accepted 2 September 1992) A fluid description source. The fluid equations are moments of the time-independent Boltzman equation when cross

Mauel, Michael E.

265

Vlasov simulations of kinetic enhancement of Raman backscatter in laser fusion plasmas

Stimulated Raman scattering (SRS) is studied in plasmas relevant to inertial confinement fusion (ICF). The Eulerian Vlasov-Maxwell code ELVIS was developed and run for this purpose. Plasma waves are heavily Landau damped ...

Strozzi, D. J. (David J.)

2006-01-01

266

NASA Technical Reports Server (NTRS)

During the indicated period of performance, we had a number of publications concerned with kinetic polar ionosphere-lower magnetosphere plasma transport. For the IUGG 1991-4 Quadrennial Report, we reviewed aspects of U.S. accomplishments concerned with polar plasma transport, among other issues. In another review, we examined the computer simulations of multiple-scale processes in space plasmas, including polar plasma outflow and transport. We also examined specifically multiscale processes in ionospheric outflows. We developed a Generalized Semi-Kinetic(GSK) model for the topside-lower magnetosphere which explored the synergistic action of wave heating and electric potentials in the formation of auroral Ion conics, in particular the "pressure cooker" mechanism. We extended the GSK model all the way down to 120 km and applied this code to illustrate the response of the ionosphere- magnetosphere to soft-electron precipitation and convection-driven frictional ion heating, respectively. Later, the convection-driven heating work was extended to a paper for the Journal of Geophysical Research. In addition to the above full published papers, we also presented the first developments of the coupled fluid-semikinetic model for polar plasma transport during this period. The results from a steady-state treatment were presented, with the second presentation being concerned with the effects of photo-electrons on the polar wind, and the first garnering an outstanding student paper award from the American Geophysical Union. We presented the first results from a time-dependent version of this coupled fluid-semikinetic model.

Horwitz, James L.

1996-01-01

267

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

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

2011-11-01

268

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

269

Kinetic Simulation of Inhomogeneous Plasma with a Variable Sized Grid System

NASA Technical Reports Server (NTRS)

Space plasmas are usually inhomogeneous and irregular. Particle in cell (PIC) plasma simulations, however, often consider the plasma to be homogeneous and periodic. Here non-periodic PIC simulations with inhomogeneities in the density, temperature and background magnetic field are considered. Boundary conditions and a variable sized grid system are discussed, along with an application to a magnetospheric plasma physics problem in the auroral zone.

Schriver, David

2003-01-01

270

DEMOCRITUS code: A kinetic approach to the simulation of complex plasmas

The DEMOCRITUS code is a particle-based code for plasma-material interaction simulation. The code makes use of particle in cell (PIC) methods to simulate each plasma species, the material, and their interaction. In this study, we concentrate on a dust particle immersed in a plasma. We start with the simplest case, in which the dust particle is not allowed to emit.

Nimlan Arinaminpat; Chris Fichtl; Leonardo Patacchini; Giovanni Lapenta; Gian Luca Delzanno

2006-01-01

271

Determination of kinetic and dynamic parameters of an expanding permeable plasma piston

Summary form only given. One of the peculiarities of pulsed phenomena in compressible media is the presence of moving boundaries plasma-liquid, gas-liquid in continuum. It is necessary to take this peculiarity into account when studying plasma of electrical discharges and laser pulses in liquid, under investigation of wave phenomena including near zone, and expanding boundary of plasma cavity which in

V. S. Krutikov

1998-01-01

272

Numerical simulation of laser fusion plasmas using a reduced description formalism

A computational study of laser fusion plasmas with a new numerical model is undertaken. The plasma is described by fluid equations and the fields by the time dependent Maxwell's equations. Problems of stimulated Brillouin scattering, self-steepening of the critical surface, wave trapping near the critical surface, and competition of inverse bremsstrahlung absorption with Brillouin scattering are treated to demonstrate the

R. J. Faehl

1976-01-01

273

This work characterized the Cl2/HBr ion enhanced plasma-surface interactions with poly-silicon as a function of the gas composition, ion energy, ion incident angle and other important process parameters. A realistic ...

Jin, Weidong, 1975-

2004-01-01

274

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

275

An efficient analytical calculation approach is presented for the Tsytovich-Angelis dust-dust collision functions consisting of the kinetic theory of dusty plasmas. This method is based on the use of binomial expansion theorem for the analytical representation of the dust-dust collision functions. The analytical calculation offers the advantage that leads to a mathematical expression, which allows the direct calculation of the dust-dust collision functions. The proposed algorithm is implemented numerically using a computer program, and its convergence properties are investigated.

Mamedov, B. A. [Department of Physics, Faculty of Arts and Sciences, Gaziosmanpasa University, Tokat 60100 (Turkey)

2010-11-15

276

This study investigates the feasibility of applications of the plasma surface modification of photocatalysts and the removal of toluene from indoor environments. N-doped TiO2 is prepared by precipitation methods and calcined using a muffle furnace (MF) and modified by radio frequency plasma (RF) at different temperatures with light sources from a visible light lamp (VLL), a white light-emitting diode (WLED) and an ultraviolet light-emitting diode (UVLED). The operation parameters and influential factors are addressed and prepared for characteristic analysis and photo-decomposition examination. Furthermore, related kinetic models are established and used to simulate the experimental data. The characteristic analysis results show that the RF plasma-calcination method enhanced the Brunauer Emmett Teller surface area of the modified photocatalysts effectively. For the elemental analysis, the mass percentages of N for the RF-modified photocatalyst are larger than those of MF by six times. The aerodynamic diameters of the RF-modifiedphotocatalyst are all smaller than those of MF. Photocatalytic decompositions of toluene are elucidated according to the Langmuir-Hinshelwood model. Decomposition efficiencies (eta) of toluene for RF-calcined methods are all higher than those of commercial TiO2 (P25). Reaction kinetics ofphoto-decomposition reactions using RF-calcined methods with WLED are proposed. A comparison of the simulation results with experimental data is also made and indicates good agreement. All the results provide useful information and design specifications. Thus, this study shows the feasibility and potential use of plasma modification via LED in photocatalysis. PMID:24645445

Shie, Je-Lueng; Lee, Chiu-Hsuan; Chiou, Chyow-San; Chen, Yi-Hung; Chang, Ching-Yuan

2014-01-01

277

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

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

278

Plasma kinetics of VLDL and HDL apoC-I in normolipidemic and hypertriglyceridemic subjects

ApoC-I has several different lipid-regulating functions including, inhibition of receptor-mediated uptake of plasma triglyceride-rich lipoproteins, inhibition of cho- lesteryl ester transfer activity, and mediation of tissue fatty acid uptake. Since little is known about the rate of produc- tion and catabolism of plasma apoC-I in humans, the present study was undertaken to determine the plasma ki- netics of VLDL and

Jeffrey S. Cohn; Michel Tremblay; Rami Batal; Hélène Jacques; Lyne Veilleux; Claudia Rodriguez; Lise Bernier; Orval Mamer; Jean Davignon

2002-01-01

279

NASA Astrophysics Data System (ADS)

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 ? 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-, e+ and ?) 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?Ec. In the ?-ray region ??m the required number of laser photons is small and the production rate of photons from the one-photon annihilation process becomes accessible to observations for subcritical fields E?Ec. In the infrared region the photon distribution has a 1/k spectrum typical for flicker noise.

Blaschke, D. B.; Dmitriev, V. V.; Röpke, G.; Smolyansky, S. A.

2011-10-01

280

NASA Astrophysics Data System (ADS)

The first real-time profile control experiments integrating magnetic and kinetic variables were performed on DIII-D in view of regulating and extrapolating advanced tokamak scenarios to steady-state devices and burning plasma experiments. Device-specific, control-oriented models were obtained from experimental data using a generic two-time-scale method that was validated on JET, JT-60U and DIII-D under the framework of the International Tokamak Physics Activity for Integrated Operation Scenarios (Moreau et al 2011 Nucl. Fusion 51 063009). On DIII-D, these data-driven models were used to synthesize integrated magnetic and kinetic profile controllers. The neutral beam injection (NBI), electron cyclotron current drive (ECCD) systems and ohmic coil provided the heating and current drive (H&CD) sources. The first control actuator was the plasma surface loop voltage (i.e. the ohmic coil), and the available beamlines and gyrotrons were grouped to form five additional H&CD actuators: co-current on-axis NBI, co-current off-axis NBI, counter-current NBI, balanced NBI and total ECCD power from all gyrotrons (with off-axis current deposition). Successful closed-loop experiments showing the control of (a) the poloidal flux profile, ?(x), (b) the poloidal flux profile together with the normalized pressure parameter, ?N, and (c) the inverse of the safety factor profile, \\bar{\\iota}(x)=1/q(x) , are described.

Moreau, D.; Walker, M. L.; Ferron, J. R.; Liu, F.; Schuster, E.; Barton, J. E.; Boyer, M. D.; Burrell, K. H.; Flanagan, S. M.; Gohil, P.; Groebner, R. J.; Holcomb, C. T.; Humphreys, D. A.; Hyatt, A. W.; Johnson, R. D.; La Haye, R. J.; Lohr, J.; Luce, T. C.; Park, J. M.; Penaflor, B. G.; Shi, W.; Turco, F.; Wehner, W.; the ITPA-IOS Group members; experts

2013-06-01

281

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 [Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon OX14 3DB (United Kingdom); Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3NP (United Kingdom); Schekochihin, Alexander A. [Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3NP (United Kingdom)

2011-10-15

282

Vlasov simulations of kinetic Alfvén waves at proton kinetic scales

NASA Astrophysics Data System (ADS)

Kinetic Alfvén waves represent an important subject in space plasma physics, since they are thought to play a crucial role in the development of the turbulent energy cascade in the solar wind plasma at short wavelengths (of the order of the proton gyro radius ?p and/or inertial length dp and beyond). A full understanding of the physical mechanisms which govern the kinetic plasma dynamics at these scales can provide important clues on the problem of the turbulent dissipation and heating in collisionless systems. In this paper, hybrid Vlasov-Maxwell simulations are employed to analyze in detail the features of the kinetic Alfvén waves at proton kinetic scales, in typical conditions of the solar wind environment (proton plasma beta ?p = 1). In particular, linear and nonlinear regimes of propagation of these fluctuations have been investigated in a single-wave situation, focusing on the physical processes of collisionless Landau damping and wave-particle resonant interaction. Interestingly, since for wavelengths close to dp and ?p ? 1 (for which ?p ? dp) the kinetic Alfvén waves have small phase speed compared to the proton thermal velocity, wave-particle interaction processes produce significant deformations in the core of the particle velocity distribution, appearing as phase space vortices and resulting in flat-top velocity profiles. Moreover, as the Eulerian hybrid Vlasov-Maxwell algorithm allows for a clean almost noise-free description of the velocity space, three-dimensional plots of the proton velocity distribution help to emphasize how the plasma departs from the Maxwellian configuration of thermodynamic equilibrium due to nonlinear kinetic effects.

Vásconez, C. L.; Valentini, F.; Camporeale, E.; Veltri, P.

2014-11-01

283

Excitation of kinetic geodesic acoustic modes by drift waves in nonuniform plasmas

Effects of system nonuniformities and kinetic dispersiveness on the spontaneous excitation of Geodesic Acoustic Mode (GAM) by Drift Wave (DW) turbulence are investigated based on nonlinear gyrokinetic theory. The coupled nonlinear equations describing parametric decay of DW into GAM and DW lower sideband are derived and then solved both analytically and numerically to investigate the effects on the parametric decay process due to system nonuniformities, such as nonuniform diamagnetic frequency, finite radial envelope of DW pump, and kinetic dispersiveness. It is found that the parametric decay process is a convective instability for typical tokamak parameters when finite group velocities of DW and GAM associated with kinetic dispersiveness and finite radial envelope are taken into account. When, however, nonuniformity of diamagnetic frequency is taken into account, the parametric decay process becomes, time asymptotically, a quasi-exponentially growing absolute instability.

Qiu, Z. [Inst. Fusion Theory and Simulation, Zhejiang Univ., Hangzhou 310027 (China)] [Inst. Fusion Theory and Simulation, Zhejiang Univ., Hangzhou 310027 (China); Chen, L. [Inst. Fusion Theory and Simulation, Zhejiang Univ., Hangzhou 310027 (China) [Inst. Fusion Theory and Simulation, Zhejiang Univ., Hangzhou 310027 (China); Dept. Physics and Astronomy, Univ. of California, Irvine, California 92697-4575 (United States); Zonca, F. [Inst. Fusion Theory and Simulation, Zhejiang Univ., Hangzhou 310027 (China) [Inst. Fusion Theory and Simulation, Zhejiang Univ., Hangzhou 310027 (China); Associazione Euratom-ENEA sulla Fusione, C.P. 65 - I-00044 - Frascati (Italy)

2014-02-15

284

NASA Astrophysics Data System (ADS)

We present the investigation of the sheath potential in an expanding plasma. The properties of the expanding plasma are measured by means of a Langmuir probe. The obtained data is used to calculate the sheath potential and the electron distribution function. We show that the sheath voltage is typically about 40% lower than in a case that neglects supersonic ions and assumes a Maxwellian electron distribution. We explain the magnitude of the measured sheath potential by balancing the ion flux density calculated with an analytical model for the expanding plasma and the electron flux density calculated with the electron distribution function.

Schröder, Benjamin; Brinkmann, Ralf Peter; Harhausen, Jens; Foest, Rüdiger; Ohl, Andreas

2015-04-01

285

Missing bits of the solar jigsaw puzzle: small-scale, kinetic effects in coronal studies

The solar corona, anomalously hot outer atmosphere of the Sun, is traditionally described by magnetohydrodynamic, fluid-like approach. Here we review some recent developments when, instead, a full kinetic description is used. It is shown that some of the main unsolved problems of solar physics, such as coronal heating and solar flare particle acceleration can be viewed in a new light when the small-scale, kinetic plasma description methods are used.

Tsiklauri, David

2009-01-01

286

Plasma etching processes often roughen the feature sidewalls forming anisotropic striations. A clear understanding of the origin and control of sidewall roughening is extremely desirable, particularly at the gate level ...

Yin, Yunpeng, Ph. D. Massachusetts Institute of Technology

2007-01-01

287

Kinetics modeling and 3-dimensional simulation of surface roughness during plasma etching

The control of feature profiles in directional plasma etching processes is crucial as critical dimension, line-edge roughening, and other artifacts affect device performance and process yields. A profile simulator is ...

Guo, Wei, Ph. D. Massachusetts Institute of Technology

2009-01-01

288

Study of surface kinetics in PECVD chamber cleaning using remote plasma source

The scope of this research work is to characterize the Transformer Coupled Toroidal Plasma (TCTP); to understand gas phase reactions and surface reactions of neutrals in the cleaning chamber by analyzing the concentration ...

An, Ju Jin

2008-01-01

289

We present numerical kinetic modeling of generation and evolution of the plasma produced as a result of resonance enhanced multiphoton ionization (REMPI) in Argon gas. The particle-in-cell/Monte Carlo collision (PIC/MCC) simulations capture non-equilibrium effects in REMPI plasma expansion by considering the major collisional processes at the microscopic level: elastic scattering, electron impact ionization, ion charge exchange, and recombination and quenching for metastable excited atoms. The conditions in one-dimensional (1D) and two-dimensional (2D) formulations correspond to known experiments in Argon at a pressure of 5?Torr. The 1D PIC/MCC calculations are compared with the published results of local drift-diffusion model, obtained for the same conditions. It is shown that the PIC/MCC and diffusion-drift models are in qualitative and in reasonable quantitative agreement during the ambipolar expansion stage, whereas significant non-equilibrium exists during the first few 10?s of nanoseconds. 2D effects are important in the REMPI plasma expansion. The 2D PIC/MCC calculations produce significantly lower peak electron densities as compared to 1D and show a better agreement with experimentally measured microwave radiation scattering.

Tholeti, Siva Sashank; Alexeenko, Alina A., E-mail: alexeenk@purdue.edu [School of Aeronautics and Astronautics, Purdue University, West Lafayette, Indiana 47907 (United States); Shneider, Mikhail N. [Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544 (United States)

2014-06-15

290

NASA Technical Reports Server (NTRS)

LSENS, the Lewis General Chemical Kinetics Analysis Code, has been developed for solving complex, homogeneous, gas-phase chemical kinetics problems and contains sensitivity analysis for a variety of problems, including nonisothermal situations. This report is part 2 of a series of three reference publications that describe LSENS, provide a detailed guide to its usage, and present many example problems. Part 2 describes the code, how to modify it, and its usage, including preparation of the problem data file required to execute LSENS. Code usage is illustrated by several example problems, which further explain preparation of the problem data file and show how to obtain desired accuracy in the computed results. LSENS is a flexible, convenient, accurate, and efficient solver for chemical reaction problems such as static system; steady, one-dimensional, inviscid flow; reaction behind incident shock wave, including boundary layer correction; and perfectly stirred (highly backmixed) reactor. In addition, the chemical equilibrium state can be computed for the following assigned states: temperature and pressure, enthalpy and pressure, temperature and volume, and internal energy and volume. For static problems the code computes the sensitivity coefficients of the dependent variables and their temporal derivatives with respect to the initial values of the dependent variables and/or the three rate coefficient parameters of the chemical reactions. Part 1 (NASA RP-1328) derives the governing equations describes the numerical solution procedures for the types of problems that can be solved by lSENS. Part 3 (NASA RP-1330) explains the kinetics and kinetics-plus-sensitivity-analysis problems supplied with LSENS and presents sample results.

Radhakrishnan, Krishnan; Bittker, David A.

1994-01-01

291

SELENIUM METABOLISM IN HUMANS: RESPONSE OF KINETIC POOLS IN PLASMA TO 2 YR SUPPLEMENTATION

Technology Transfer Automated Retrieval System (TEKTRAN)

Selenium (Se) is a particularly promising cancer chemopreventive agent. We have been investigating the effects of oral Se supplementation on the metabolism of two forms of Se, selenomethionine (SeMet) and selenite (Sel), by comparing kinetics for 4-mo before (PK1) and after (PK2) 2 yrs of supplemen...

292

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

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

293

Spatially Modulated Phase in the Holographic Description of Quark-Gluon Plasma

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-Nordstroem 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 0.8N{sub f} fm{sup -3} at temperature 150 MeV.

Ooguri, Hirosi [California Institute of Technology, 452-48, Pasadena, California 91125 (United States); Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, University of Tokyo, Kashiwa, Chiba 277-8586 (Japan); Park, Chang-Soon [Santa Cruz Institute for Particle Physics and Department of Physics, University of California, Santa Cruz, California 95064 (United States)

2011-02-11

294

PHELA is a herbal mixture of four African traditional medicinal plants that is under development by the Medical Research Council (MRC) for use as an immune stimulant in immune compromised individuals. Before major in vivo investigations could be conducted, there was a need to establish a plasma marker for concentration monitoring of PHELA. Chromatographic separation was achieved using a C18 RP column (250 mm × 4.6 mm × 5 µm), 70% acetonitrile in water and fluorescent detection. Three groups of rats (n=5) were administered with PHELA (15.4 mg/kg) and one rat from each group was sacrificed at 1, 2, 4, 6 and 8 hours. Surprisingly, on the HPLC analysis, none of the marker peaks of spiked plasma were detectable in the plasma of treated animals. Instead, a new peak was observed at 9.2 minutes, which implied that it was a metabolite of PHELA. Using peak area per unit plasma volume (PK-area/L), the relevant pharmacokinetic parameters were derived. The metabolite's half-life was 3.47±0.35 hours and reached maximum concentration at 4.67 ± 1.15 hrs. It was estimated that with once daily dosing of PHELA, the concentration at steady state (Css) would be 47.52 ± 5.94 PK-area/L with no drug accumulation (Acc index =.009 ± 0.004). In conclusion, the use of peak area per unit volume to derive pharmacokinetics of unknown compounds (Peak-kinetics) and to confirm ingestion of PHELA were demonstrated with a hope that they may appeal to those experiencing similar problems with monitoring of herbal products of which little is known. PMID:23983357

Lekhooa, Makhotso; Walubo, Andrew; Du Plessis, Jan J B; Matsabisa, Motlalepula G

2012-01-01

295

OBJECTIVE: Glucose intolerance is frequently associated with an altered plasma lipid profile and increased cardiovascular disease risk. Nonetheless, lipid metabolism is scarcely studied in normolipidemic glucose-intolerant patients. The aim of this study was to investigate whether important lipid metabolic parameters, such as the kinetics of LDL free and esterified cholesterol and the transfer of lipids to HDL, are altered in glucose-intolerant patients with normal plasma lipids. METHODS: Fourteen glucose-intolerant patients and 15 control patients were studied; none of the patients had cardiovascular disease manifestations, and they were paired for age, sex, race and co-morbidities. A nanoemulsion resembling a LDL lipid composition (LDE) labeled with 14C-cholesteryl ester and 3H-free cholesterol was intravenously injected, and blood samples were collected over a 24-h period to determine the fractional clearance rate of the labels by compartmental analysis. The transfer of free and esterified cholesterol, triglycerides and phospholipids from the LDE to HDL was measured by the incubation of the LDE with plasma and radioactivity counting of the supernatant after chemical precipitation of non-HDL fractions. RESULTS: The levels of LDL, non-HDL and HDL cholesterol, triglycerides, apo A1 and apo B were equal in both groups. The 14C-esterified cholesterol fractional clearance rate was not different between glucose-intolerant and control patients, but the 3H-free- cholesterol fractional clearance rate was greater in glucose-intolerant patients than in control patients. The lipid transfer to HDL was equal in both groups. CONCLUSION: In these glucose-intolerant patients with normal plasma lipids, a faster removal of LDE free cholesterol was the only lipid metabolic alteration detected in our study. This finding suggests that the dissociation of free cholesterol from lipoprotein particles occurs in normolipidemic glucose intolerance and may participate in atherogenic signaling. PMID:22522760

Bertato, Marina P; Oliveira, Carolina P; Wajchenberg, Bernardo L; Lerario, Antonio C; Maranhão, Raul C

2012-01-01

296

Electron-ion interactions are central to numerous phenomena in the warm dense matter (WDM) regime and at higher temperature. The electron-ion collisions induced friction at high temperature is introduced in the procedure of ab initio molecular dynamics using the Langevin equation based on density functional theory. In this framework, as a test for Fe and H up to 1000 eV, the equation of state and the transition of electronic structures of the materials with very wide density and temperature can be described, which covers a full range of WDM up to high energy density physics. A unified first principles description from condensed matter to ideal ionized gas plasma is constructed. PMID:20867307

Dai, Jiayu; Hou, Yong; Yuan, Jianmin

2010-06-18

297

A kinetic equation for linear stable fractional motion with applications to space plasma physics

Levy flights and fractional Brownian motion have become exemplars of the heavy-tailed jumps and long-ranged memory widely seen in physics. Natural time series frequently combine both effects, and linear fractional stable motion (lfsm) is a model process of this type, combining {alpha}-stable jumps with a memory kernel. In contrast complex physical spatiotemporal diffusion processes where both the above effects compete have for many years been modeled using the fully fractional kinetic equation for the continuous-time random walk (CTRW), with power laws in the probability density functions of both jump size and waiting time. We derive the analogous kinetic equation for lfsm and show that it has a diffusion coefficient with a power law in time rather than having a fractional time derivative like the CTRW. We discuss some preliminary results on the scaling of burst 'sizes' and 'durations' in lfsm time series, with applications to modeling existing observations in space physics and elsewhere.

Watkins, Nicholas W [British Antarctic Survey, Cambridge, UK; Credgington, Daniel [British Antarctic Survey, Cambridge, UK; Sanchez, Raul [ORNL; Rosenberg, SJ [British Antarctic Survey, Cambridge, UK; Chapman, Sandra C [University of Warwick, UK

2009-01-01

298

DEMOCRITUS code: A kinetic approach to the simulation of complex plasmas

NASA Astrophysics Data System (ADS)

The DEMOCRITUS code is a particle-based code for plasma-material interaction simulation. The code makes use of particle in cell (PIC) methods to simulate each plasma species, the material, and their interaction. In this study, we concentrate on a dust particle immersed in a plasma. We start with the simplest case, in which the dust particle is not allowed to emit. From here, we expand the DEMOCRITUS code to include thermionic and photo emission algorithms and obtain our data. Next we expand the physics processes present to include the presence of magnetic fields and collisional processes with a neutral gas. Finally we describe new improvements of the code including a new mover that allows for particle subcycling and a new grid adaptation approach.

Arinaminpat, Nimlan; Fichtl, Chris; Patacchini, Leonardo; Lapenta, Giovanni; Delzanno, Gian Luca

2006-10-01

299

The influence of current-aligned instabilities on magnetic reconnection is investigated using state-of-the-art fully kinetic simulations with boundary conditions mimicking Magnetic Reconnection eXperiment (MRX). MRX is a controlled, well-diagnosed reconnection experiment that provides a unique opportunity to perform detailed comparison between simulations and observations in ways that are not as easily possible with spacecraft data. At the same time, simulations help

V. Roytershteyn; W. S. Daughton; L. Yin; B. J. Albright; K. Bowers; S. Dorfman; H. Ji; M. Yamada; H. Karimabadi

2009-01-01

300

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

301

A steady-state kinetic model of butyrylcholinesterase from horse plasma

The steady-state kinetics of the butyrylcholinesterase-catalysed hydrolysis of butyrylthiocholine and thiophenyl acetate were shown to deviate from Michaelis–Menten kinetics. The `best' empirical rate law was selected by fitting different rate equations to the experimental data by non-linear regression methods. The results were analysed in view of two alternative interpretations: (1) the reaction is catalysed by a mixture of enzymes, or (2) the activity is due to a single enzyme displaying deviations from Michaelis–Menten kinetics. It was concluded that the second alternative applies, and this conclusion was further supported by experiments involving simultaneous hydrolysis of alternative thiol ester substrates (butyrylthiocholine/thiophenyl acetate) as well as alternative thiol ester and oxygen ester substrates (butyrylthiocholine/phenyl acetate; thiophenyl acetate/butyrylcholine; acetylthiocholine/phenyl acetate). On the basis of the conclusion that a single enzyme is responsible for the activity, a molecular model is proposed. This model involves an acylated enzyme, and implies binding to the enzyme of one acyl group and one ester molecule, but not two ester molecules at the same time. Thus butyrylcholinesterase, which is structurally a tetramer, behaves functionally as a co-operative dimer, an interpretation in accordance with available data from active-site titrations. PMID:4463963

Augustinsson, Klas-Bertil; Bartfai, Tamas; Mannervik, Bengt

1974-01-01

302

Optimization of kinetic parameters for the degradation of plasmid DNA in rat plasma

NASA Astrophysics Data System (ADS)

Biotechnology is a rapidly growing area of research work in the field of pharmaceutical sciences. The study of pharmacokinetics of plasmid DNA (pDNA) is an important area of research work. It has been observed that the process of gene delivery faces many troubles on the transport of pDNA towards their target sites. The topoforms of pDNA has been termed as super coiled (S-C), open circular (O-C) and linear (L), the kinetic model of which will be presented in this paper. The kinetic model gives rise to system of ordinary differential equations (ODEs), the exact solution of which has been found. The kinetic parameters, which are responsible for the degradation of super coiled, and the formation of open circular and linear topoforms have a great significance not only in vitro but for modeling of further processes as well, therefore need to be addressed in great detail. For this purpose, global optimization techniques have been adopted, thus finding the optimal results for the said model. The results of the model, while using the optimal parameters, were compared against the measured data, which gives a nice agreement.

Chaudhry, Q. A.

2014-12-01

303

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

304

It has been suggested that Rydberg gas atoms are involved in conducting electricity through a steady state flowing afterglow (FAG) discharge plasma (R. S. Mason, D. J. Mitchell and P. M. Dickinson, Phys. Chem. Chem. Phys., 2010, DOI: ). From known properties of Rydberg atoms, a statistical model is developed here to find the distribution of levels (principal quantum number n) occupied in such a hypothetical Rydberg gas. It behaves non-ideally at positive column plasma densities, predicting 30 < n < 150, peaking at n approximately = 85. These values depend on assumptions concerning the power of n dependency of 'pressure ionization' and the free charge density. The occupied states are very long-lived and almost completely separated from the low n states by the low probability of intermediate levels. The effects of Rydberg gas (N(R)) and free charge densities are examined. The gas can exist in a deep free energy well (> 120 kJ mol(-1) below ionisation level when 10(10) < or = N(R) < or = 10(11) atoms cm(-3)) but this is approximately 11 kJ mol(-1) higher than that of the equivalent free ion-electron gas; therefore if it exists in preference to the classical form of the plasma, it is controlled by kinetic factors. A mechanism is suggested by which this could occur. Thus, whilst ionization by high energy electron impact occurs at the Cathode Fall-Negative Glow (NG) boundary as usual, excitation of Rydberg atoms becomes more probable, by electrons slowed by collision and deceleration at the opposite NG-Positive Column (PC) plasma boundary. The atoms become stabilized after passing into the PC, by collisionally induced (nlm) mixing of states and the removal of free charge by charge transfer (and hence the passage of electric current through the Rydberg gas). The coupling of Rydberg states with the ionization continuum is poor; therefore, if the rate of their charge transfer is greater than that of their ionization, the Rydberg gas will remain relatively charge free and hence stable when it is conducting a current. When applied to the FAG plasma, the model provides a self-consistent interpretive framework for all its electrical, mass spectrometric and chemical behaviour. The effect on the optical spectroscopy of these plasmas is considered briefly. PMID:20358067

Mason, Rod S; Douglas, Peter

2010-04-21

305

Macroscopic Lagrangian description of warm plasmas. I Formulation of the Lagrangian

NASA Technical Reports Server (NTRS)

A macroscopic Lagrangian is derived which includes a pressure tensor, heat conduction, and elastic collisions. Its Euler-Lagrange equations are shown to be the Maxwell equations and the macroscopic force law. The corresponding Hamiltonian is derived, and Hamilton's canonical equations are also demonstrated to lead to the Maxwell equations and the macroscopic force law. The treatment is facilitated by working in a mixture of Eulerian coordinates (for the fields) and Lagrangian coordinates (for the particle motions), and the introduction of a macroscopic potential expressed in terms of the plasma thermal energy and the energy losses by heat conduction.

Peng, Y.-K. M.; Crawford, F. W.

1983-01-01

306

NASA Astrophysics Data System (ADS)

We present a new high-resolution numerical model for the simulation of crystallization and texture evolution using arbitrary rates of crystal nucleation and growth. The algorithm models single or multiphase solidification in a three-dimensional domain and 17 simulations using constant, linearly increasing, exponential, and Gaussian functions for the rates of nucleation and growth yield equigranular to seriate textures. Conventional crystal size distributions of all textures are nearly linear to concave-down (previously interpreted as formed by equilibration coarsening), and identical distribution patterns can result from multiple non-unique combinations of nucleation and growth rates. The clustering index is always a non-monotonous function, which initially increases then decreases with increasing crystal fraction. For texture from random homogeneous nucleation the index is substantially lower than previous predictions based on a random sphere distribution line, hence, natural samples interpreted as clustered now have greater degrees of randomness or ordering. The average number of contact neighbors and the average neighbor distance of a crystal depend linearly on crystal size, but one of the two remains insensitive to nucleation and growth kinetics and represents potential indicator of other crystallization processes than random nucleation and crystal growth. Simultaneous comparison of size, spatial and clustering patterns and of their departures from expected values are suggested to allow for separation of effects of crystallization kinetics, melt-mineral mechanical interactions, suspension mixing, or postcrystallization re-equilibration and coarsening on natural igneous rocks.

Špillar, Václav; Dolejš, David

2014-04-01

307

Kinetics of plasma membrane and mitochondrial alterations in cells undergoing apoptosis

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

Gérard Lizard; Sylvie Fournel; Laurent Genestier; Nathalie Dhedin; Christophe Chaput; Monique Flacher; Mireille Mutin; Geneviève Panaye; Jean-Pierre Revillard

1995-01-01

308

Modulation of plasma lipid levels and cholesterol kinetics by phytosterol versus phytostanol esters

It has been suggested that phytosterol and phy- tostanol esters possess similar cholesterol-lowering proper- ties, however, whether mechanisms responsible are identi- cal has not been addressed. To address this question, cholesterol plasma levels, absorption, biosynthesis, and turnover were measured in 15 hypercholesterolemic sub- jects consuming prepared diets each over 21 d using a cross- over design. Diets contained either i

Peter J. Jones; Mahmoud Raeini-Sarjaz; Fady Y. Ntanios; Catherine A. Vanstone; Jian Y. Feng; William E. Parsons

309

Kinetic model of titanium laser induced plasma expansion in nitrogen environment

NASA Astrophysics Data System (ADS)

A theoretical model to investigate the laser induced plasma (LIP) produced by a nanosecond laser pulse interacting with a metallic titanium target in a nitrogen environment is presented. In this work the influence of chemical processes on the plume expansion has been investigated, applying a 2D fluid dynamic code under local thermodynamic equilibrium or chemical non-equilibrium approximations.

Casavola, A. R.; Colonna, G.; Capitelli, M.

2009-05-01

310

Kinetic model of titanium laser induced plasma expansion in nitrogen environment

A theoretical model to investigate the laser induced plasma (LIP) produced by a nanosecond laser pulse interacting with a metallic titanium target in a nitrogen environment is presented. In this work the influence of chemical processes on the plume expansion has been investigated, applying a 2D fluid dynamic code under local thermodynamic equilibrium or chemical non-equilibrium approximations.

A. R. Casavola; G. Colonna; M. Capitelli

2009-01-01

311

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

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

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

2009-01-01

312

Influence of Lactobionic accid on the kinetics of Thrombin in human plasma

In clotting plasma, it has been demonstrated that heparin can act via antithrombin III (AT III) directly on the thrombin generated in situ or indirectly on the enzymatic complex, prothrombinase (or on one of its components), responsjble for the conversion of pro- thrombin to thrombin. r These two properties, antithrom- bin activity and antiprothrombinase activity, can be differentiated by mathematical

Suzette S. Beguin; Frederic Dol; H. Coenraad Hemker

1991-01-01

313

A collisional radiative model was developed in order to investigate the influence of dissociative recombination on the Saha–Boltzmann plasma equilibrium. As the dissociative recombination products are not well known, their relative importance was tested through comparison with the distribution of line intensities obtained in a microwave argon discharge produced at atmospheric pressure by a surface wave. It was found that

A. Sa´inz; J. Margot; M. C. Garci´a; M. D. Calzada

2005-01-01

314

A collisional radiative model was developed in order to investigate the influence of dissociative recombination on the Saha-Boltzmann plasma equilibrium. As the dissociative recombination products are not well known, their relative importance was tested through comparison with the distribution of line intensities obtained in a microwave argon discharge produced at atmospheric pressure by a surface wave. It was found that

A. Sáinz; J. Margot; M. C. García; M. D. Calzada

2005-01-01

315

Decharging of Complex Plasmas: First Kinetic Observations A.V. Ivlev,1

with an ellipsoidal void in the center of the chamber, as shown in Fig. 1(a). The shape of the cloud is close switching off the rf power, in the afterglow plasma, ions and electrons rapidly recombine and leave a cloud chamber for a sufficiently long time, allowing precise measurements of the rest particle charge. A simple

Goree, John

316

Comparison of initial value and eigenvalue codes for kinetic toroidal plasma instabilities

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

317

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.

Lieou, Charles K C; Carlson, Jean M

2013-01-01

318

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.

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

2013-01-25

319

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 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.

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

2013-07-01

320

We use a kinetic treatment to study the linear transverse dispersion relation for a magnetized isotropic relativistic electron-positron plasma with finite relativistic temperature. The explicit linear dispersion relation for electromagnetic waves propagating along a constant background magnetic field is presented, including an analytical continuation to the whole complex frequency plane for the case of Maxwell-Jüttner velocity distribution functions. This dispersion relation is studied numerically for various temperatures. For left-handed solutions, the system presents two branches, the electromagnetic ordinary mode and the Alfvén mode. In the low frequency regime, the Alfvén branch has two dispersive zones, the normal zone (where ??/?k?>?0) and an anomalous zone (where ??/?k?plasma frequency with the temperature. We complemented the analytical and numerical approaches with relativistic full particle simulations, which consistently agree with the analytical results.

López, Rodrigo A. [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Concepción, Concepción (Chile); Moya, Pablo S. [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, Maryland 20771 (United States); Department of Physics, Catholic University of America, Washington DC, DC 20064 (United States); Muñoz, Víctor [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Viñas, Adolfo F. [NASA Goddard Space Flight Center, Heliophysics Science Division, Geospace Physics Laboratory, Mail Code 673, Greenbelt, Maryland 20771 (United States); Valdivia, J. Alejandro [Departamento de Física, Facultad de Ciencias, Universidad de Chile, Casilla 653, Santiago (Chile); Centro para el Desarrollo de la Nanociencia y la Nanotecnología, CEDENNA, Santiago (Chile)

2014-09-15

321

Arbitrary amplitude double layers in warm dust kinetic Alfven wave plasmas

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

322

Kinetic processes in the plasma formed in combustion of hydrocarbon fuels

NASA Astrophysics Data System (ADS)

An analysis of the basic kinetic processes responsible for the formation of ions, electrons, charged and neutral carbon clusters and particles of nanometer size in the combustion of hydrocarbon fuels has been made. It has been shown that the formation of a polydisperse ensemble of positively and negatively charged particles is mainly caused by the ion adhesion to primary particles and secondarily formed particles and also by particle coagulation. Account must be taken not only of the Coulomb interaction but also of the van der Waals and polarization interaction between particles. The distinstice features of the deposition of polar molecules on charged particles have been considered.

Starik, A. M.; Savel'Ev, A. M.; Titova, N. S.

2011-01-01

323

Quantitative description of ion transport via plasma membrane of yeast and small cells

Modelling of ion transport via plasma membrane needs identification and quantitative understanding of the involved processes. Brief characterisation of ion transport systems of a yeast cell (Pma1, Ena1, TOK1, Nha1, Trk1, Trk2, non-selective cation conductance) and estimates concerning the number of molecules of each transporter per a cell allow predicting the corresponding ion flows. Comparison of ion transport in small yeast cell and several animal cell types is provided and importance of cell volume to surface ratio is stressed. Role of cell wall and lipid rafts is discussed in aspect of required increase in spatial and temporary resolution of measurements. Conclusions are formulated to describe specific features of ion transport in a yeast cell. Potential directions of future research are outlined based on the assumptions.

Vadim Volkov

2012-12-18

324

The Dynamics of Flux Tubes in a High- beta Plasma. I. A General Description

NASA Astrophysics Data System (ADS)

We suggest a new model for the structure of a magnetic field embedded in a plasma whose average turbulent and magnetic energy densities are both much less than the gas pressure. This model is based on the popular notion that the magnetic field will tend to separate into individual flux tubes. We point out that interactions between the flux tubes will be dominated by coherent effects stemming from the turbulent wakes created as the fluid streams by the flux tubes. Balancing the attraction caused by shielding effects with turbulent diffusion we find that flux tubes have typical radii comparable to the local Mach number squared times the large-scale eddy length, are arranged in a one-dimensional fractal pattern, have a radius of curvature comparable to the largest scale eddies in the turbulence, and have an internal magnetic pressure comparable to the ambient pressure. When the average magnetic energy density is much less than the turbulent energy density, the radius and curvature scale of the flux tubes will be smaller than these estimates. Allowing for resistivity changes these properties but does not alter the macroscopic properties of the fluid or the large-scale magnetic field. In either case we show that the Sweet-Parker reconnection rate is at least as fast as an eddy turnover time. Realistic stellar plasmas are expected to either be in the ideal limit (e.g., the solar photosphere) or the resistive limit (the bulk of the solar convection zone). Allowing for significant viscosity drastically changes the macroscopic properties of the magnetic field. We find that all current numerical simulations of three-dimensional MHD turbulence are in the viscous regime and are inapplicable to stars or accretion disks. However, these simulations are in good quantitative agreement with our model in the viscous limit.

Vishniac, Ethan T.

1995-06-01

325

Kinetics of electron-positron pair plasmas using an adaptive Monte Carlo method

A new algorithm for implementing the adaptive Monte Carlo method is given. It is used to solve the relativistic Boltzmann equations that describe the time evolution of a nonequilibrium electron-positron pair plasma containing high-energy photons and pairs. The collision kernels for the photons as well as pairs are constructed for Compton scattering, pair annihilation and creation, bremsstrahlung, and Bhabha & Moller scattering. For a homogeneous and isotropic plasma, analytical equilibrium solutions are obtained in terms of the initial conditions. For two non-equilibrium models, the time evolution of the photon and pair spectra is determined using the new method. The asymptotic numerical solutions are found to be in a good agreement with the analytical equilibrium states. Astrophysical applications of this scheme are discussed.

Ravi P. Pilla; Jacob Shaham

1997-02-21

326

Two-stage densification process of nanosized 3 mol% yttria-stabilized zirconia (3Y-SZ) polycrystalline compacts during consolidation via microwave and spark-plasma sintering have been observed. The values of activation energies obtained for microwave and spark-plasma sintering 260-275 kJ x mol(-1) are quite similar to that of conventional sintering of zirconia, suggesting that densification during initial stage is controlled by the grain-boundary diffusion mechanism. The sintering behavior during microwave sintering was significantly affected by preliminary pressing conditions, as the surface diffusion mechanism (230 kJ x mol(-1)) is active in case of cold-isostatic pressing procedure was applied. PMID:22905503

Vasylkiv, Oleg; Demirskyi, Dmytro; Sakka, Yoshio; Ragulya, Andrey; Borodianska, Hanna

2012-06-01

327

Kinetic Simulations of the Self-Focusing and Dissipation of Finite-Width Electron Plasma Waves

NASA Astrophysics Data System (ADS)

Two-dimensional simulations, both Vlasov and particle-in-cell, are presented that show the evolution of the field and electron distribution of finite-width, nonlinear electron plasma waves. The intrinsically intertwined effects of self-focusing and dissipation of field energy caused by electron trapping are studied in simulated systems that are hundreds of wavelengths long in the transverse direction but only one wavelength long and periodic in the propagation direction. From various initial wave states, both the width at focus ?m relative to the initial width ?0 and the maximum field amplitude at focus are shown to be a function of the growth rate of the transverse modulational instability ?TPMI divided by the loss rate of field energy ?E to electrons escaping the trapping region. With dissipation included, an amplitude threshold for self-focusing ?TPMI/?E˜1 is found that supports the analysis of Rose [Phys. Plasmas 12, 012318 (2005)].

Winjum, B. J.; Berger, R. L.; Chapman, T.; Banks, J. W.; Brunner, S.

2013-09-01

328

A kinetic equation for linear fractional stable motion with applications to space plasma physics

Levy flights and fractional Brownian motion (fBm) have become exemplars of the heavy tailed jumps and long-ranged memory seen in space physics and elsewhere. Natural time series frequently combine both effects, and Linear Fractional Stable Motion (LFSM) is a model process of this type, combining alpha-stable jumps with a memory kernel. In contrast complex physical spatiotemporal diffusion processes where both the above effects compete-dubbed "ambivalent" by Brockmann et al (2006}-have for many years been modelled using the fully fractional (FF) kinetic equation for the continuous time random walk (CTRW), with power laws in the pdfs of both jump size and waiting time. We derive the analogous kinetic equation for LFSM and show that it has a diffusion coefficient with a power law in time rather than having a fractional time derivative like the CTRW. We develop earlier comments by Lutz (2001) on how fBm differs from its fractional time process counterpart. We go on to argue more physically why LFSM and the FFCTRW might indeed be expected to differ, and discuss some preliminary results on the scaling of burst "sizes" and "durations" in LFSM time series, with applications to modelling existing observations in space physics.

Nicholas W. Watkins; Daniel Credgington; Raul Sanchez; Sandra C. Chapman

2008-03-19

329

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

330

Temporal description of aluminum laser-induced plasmas by means of a collisional-radiative model

NASA Astrophysics Data System (ADS)

A 0D numerical approach including a Collisional-Radiative model is elaborated in the purpose of describing the behavior of the nascent plasma resulting from the interaction between a laser pulse (? = 532 nm, ? = 4 ns and F = 6.5 J cm-2) with an aluminum sample. The species considered are Al, Al+, Al2+ and Al3+ on their different excited states and free electrons. Both groups of particles are characterized by their translation temperature in thermal non-equilibrium state. Besides, each population density is assumed to be in chemical non-equilibrium and behaves freely through the seven involved elementary processes (electron impact induced excitation and ionization, elastic collisions, multi-photon ionization, inverse laser Bremsstrahlung, direct electron Bremsstrahlung and spontaneous emission). Atoms passing from sample to gas phase are described by considering classical vaporization phenomena so that the surface temperature is limited to values less than the critical point. The relative role of the elementary processes is discussed and the time-evolution of the excitation of the species is analyzed.

Morel, Vincent; Bultel, Arnaud; Chéron, Bruno G.

2014-05-01

331

New aspects of plasma sheet dynamics Â± MHD and kinetic theory H. Wiechen Institut fuÃ? r Astronomie reconnection is a process of funda- mental importance for the dynamics of the Earth's plasma sheet. In this context, the development of thin current sheets in the near-Earth plasma sheet is a topic of special

Boyer, Edmond

332

Transition form collisional to kinetic reconnection in large-scale plasmas

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

333

Convective Raman amplification of light pulses causing kinetic inflation in inertial fusion plasmas

We perform 1D particle-in-cell (PIC) simulations using OSIRIS, which model a short-duration ({approx}500{omega}{sub 0}{sup -1} FWHM) scattered light seed pulse in the presence of a constant counter-propagating pump laser with an intensity far below the absolute instability threshold. The seed undergoes linear convective Raman amplification and dominates over fluctuations due to particle discreteness. Our simulation results are in good agreement with results from a coupled-mode solver when we take into account special relativity and the use of finite size PIC simulation particles. We present linear gain spectra including both effects. Extending the PIC simulations past when the seed exits the simulation domain reveals bursts of large-amplitude scattering in many cases, which does not occur in simulations without the seed pulse. These bursts can have amplitudes several times greater than the amplified seed pulse, and we demonstrate that this large-amplitude scattering is the result of kinetic inflation by examining trapped particle orbits. This large-amplitude scattering is caused by the seed modifying the distribution function earlier in the simulation. We perform some simulations with longer duration seeds, which lead to parts of the seeds undergoing kinetic inflation and reaching amplitudes several times more than the steady-state linear theory results. Simulations with continuous seeds demonstrate that the onset of inflation depends on seed wavelength and incident intensity, and we observe oscillations in the reflectivity at a frequency equal to the difference between the seed frequency and the frequency at which the inflationary stimulated Raman scattering grows.

Ellis, I. N. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); University of California, Los Angeles, California 90095 (United States); Strozzi, D. J.; Williams, E. A. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Winjum, B. J.; Tsung, F. S.; Mori, W. B.; Fahlen, J. E. [University of California, Los Angeles, California 90095 (United States); Grismayer, T. [University of California, Los Angeles, California 90095 (United States); Grupo de Lasers e Plasmas, Instituto Superior Tecnico, 1049-001 Lisboa (Portugal)

2012-11-15

334

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

335

Modeling the chemical kinetics of atmospheric plasma for cell treatment in a liquid solution

Low temperature atmospheric pressure plasmas have been known to be effective for living cell inactivation in a liquid solution but it is not clear yet which species are key factors for the cell treatment. Using a global model, we elucidate the processes through which pH level in the solution is changed from neutral to acidic after plasma exposure and key components with pH and air variation. First, pH level in a liquid solution is changed by He{sup +} and He(2{sup 1}S) radicals. Second, O{sub 3} density decreases as pH level in the solution decreases and air concentration decreases. It can be a method of removing O{sub 3} that causes chest pain and damages lung tissue when the density is very high. H{sub 2}O{sub 2}, HO{sub 2}, and NO radicals are found to be key factors for cell inactivation in the solution with pH and air variation.

Kim, H. Y.; Kang, S. K.; Lee, H. Wk. [Department of Electrical Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Lee, H. W. [Medipl Corporation, Pohang 790-834 (Korea, Republic of); Kim, G. C. [Medipl Corporation, Pohang 790-834 (Korea, Republic of); Department of Oral Anatomy and Cell Biology, School of Dentistry, Pusan National University, Pusan 602-739 (Korea, Republic of); Lee, J. K. [Department of Electrical Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Medipl Corporation, Pohang 790-834 (Korea, Republic of)

2012-07-15

336

A model is constructed to describe the behavior of isolated chromaffin granules (secretory vesicles of the adrenal medulla) when they are induced to release their contents by incubation with MgATP and Cl-. The model is based on the assumption that the release event is osmotic lysis due to the ATPase dependent influx of protons and osmotically active Cl- ions. The consequences of this influx of osmotically active particles are predicted from osmotic fragility curves determined by suspending granules in hypotonic media. Turbidity measurements on granule suspensions undergoing the ATP and Cl- dependent release reaction are used to fit the parameters of the model. The model then successfully described the time course, Cl- dependence, ATP dependence, and osmotic strength suppression of the release event as monitored either by measurement of turbidity changes or of epinephrine release. The degree of suppression of release predicted in hypertonic media is also in agreement with published data on hypertonic suppression of exocytosis from several cell types: chromaffin cells, blood platelets, and parathyroid cells. Therefore, the model may also provide an accurate description of some of the events occurring during exocytosis. PMID:6455169

Creutz, C E; Pollard, H B

1980-01-01

337

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). PMID:12232379

Buckhout, T. J.

1994-01-01

338

Plasma transport in stochastic magnetic fields. III. Kinetics of test-particle diffusion

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

339

NASA Astrophysics Data System (ADS)

Supernova remnant and heliopause termination shock plasmas may contain significant populations of minority heavy ions such as alpha-particles, with relative number densities n?/ni up to 50%. Fully self-consistent kinetic simulations of quasi-perpendicular, supercritical shocks can show non-steady, reforming solutions with consequences for ion acceleration local to the shock. We present the first set of particle-in-cell simulations that span the entire range of values of n?/ni from zero to one, where the two ion species and electrons are all treated fully self-consistently. These '1.5D' simulations evolve the full three dimensional particle trajectories and electromagnetic vector fields as a function of one space co-ordinate and time. The simulated supercritical (Mach number ~ 8) shocks have perpendicular geometry, plasma ? = 0.15, upstream magnetic field B1 = 10-7T and particle density n ? 107m-3. Crucial to the time evolving phenomenology of the shocks and particles at different n?/ni are the interplay between the differing characteristic gyroscales of the two ion species. Ions can gain energy both directly by acceleration in the electromagnetic foot-ramp region of the shock, and in the strongly fluctuating fields downstream. The downstream field fluctuations are driven by the free energy that both ion species gain in their initial interaction with the shock. The details of all these processes, and their efficiency for energization, are found to depend on n?/ni. Disclaimer: This work was partly funded by the UK Engineering and Physics Sciences Research Council under grant EP/G003955 and by The European Communities under the contract of association between Euratom and CCFE. The views and opinions expressed herein do not necessarily represent those of the European Communities.

Rekaa, Vegard L.; Chapman, Sandra C.; Dendy, Richard O.

2014-05-01

340

A series of numerical simulations based on a recurrence-free Vlasov kinetic algorithm presented earlier [Abbasi et al., Phys. Rev. E 84, 036702 (2011)] are reported. Electron-ion plasmas and three-component (electron-ion-dust) dusty, or complex, plasmas are considered, via independent simulations. Considering all plasma components modeled through a kinetic approach, the nonlinear behavior of ionic scale acoustic excitations is investigated. The focus is on Bernstein–Greene–Kruskal (BGK) modes generated during the simulations. In particular, we aim at investigating the parametric dependence of the characteristics of BGK structures, namely of their time periodicity (?{sub trap}) and their amplitude, on the electron-to-ion temperature ratio and on the dust concentration. In electron-ion plasma, an exponential relation between ?{sub trap} and the amplitude of BGK modes and the electron-to-ion temperature ratio is observed. It is argued that both characteristics, namely, the periodicity ?{sub trap} and amplitude, are also related to the size of the phase-space vortex which is associated with BGK mode creation. In dusty plasmas, BGK modes characteristics appear to depend on the dust particle density linearly.

Hosseini Jenab, S. M., E-mail: mehdi.jenab@yahoo.com [Department of Physics, South Tehran Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Kourakis, I., E-mail: IoannisKourakisSci@gmail.com [Center for Plasma Physics, Department of Physics and Astronomy, Queen's University Belfast, Belfast BT7 1NN, Northern Ireland (United Kingdom)

2014-04-15

341

Plasma kinetic of ingested essential amino acids in healthy elderly people.

The purpose of this study was to investigate whether the documented difficulties of physiological amounts of essential amino acids (EAAs) (7 g) to induce protein synthesis could be reflected in a simple method adaptable to a clinical setting. Sixteen healthy individuals, nine elderly (75.3 ± 3.5 years), and seven young (28 ± 2.5 years) were enrolled in the study. Five minutes before EAA ingestion (baseline) and 20, 40, 60, 90, 120, 180 min after EAA ingestion, venous blood samples were taken from the ante-cubital vein to determine the concentrations of EAAs (?mol/L). The results show that plasma EAA increases were significantly higher in old than in young persons at the considered time points (from p < 0.004 to p < 0.001) (unpaired Student t test). However, the velocity rate of the increasing was slower in old subjects than in young group. The study shows that EAAs ingestion by old subject is associated with reduced muscle EAA uptake. PMID:23934784

Condino, Anna Maria; Aquilani, Roberto; Pasini, Evasio; Iadarola, Paolo; Viglio, Simona; Verri, Manuela; D'Agostino, Luca; Boschi, Federica

2013-12-01

342

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

343

Kinetic theory of electromagnetic plane wave obliquely incident on bounded plasma slab

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}<

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

344

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

345

Human muscle sympathetic nerve activity and plasma noradrenaline kinetics in space

NASA Technical Reports Server (NTRS)

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 Jr; 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

346

A Landau fluid model for electromagnetic plasma microturbulence P.B. Snyder

A Landau fluid model for electromagnetic plasma microturbulence P.B. Snyder General Atomics, P that is being submitted to Physics of Plasmas. A fluid model is developed for the description of microturbulence fluctuations, as well as finite Larmor radius and kinetic effects. Multi-species Landau fluid equations

Hammett, Greg

347

In this paper, first we represent the differences between spatial and temporal dispersions and their dependence on the measurement techniques for electrostatic waves in unmagnetized collisionless plasma. Then, three different experimental data are compared to the solutions of exact nonextensive dispersion relations for electron-ion and pair plasma. The results confirm the existence of new acoustic plasma waves. Furthermore, these comparisons yield a Maxwellian and a nonextensive plasma with nonextensive parameter q larger than one, and a Maxwellian plasma with some abnormal dispersion properties.

Ebrahimi, V.; Esfandyari-Kalejahi, A. [Department of Physics, Faculty of Sciences, Azarbaijan Shahid Madani University, 53714-161 Tabriz (Iran, Islamic Republic of)

2014-09-15

348

Besides being one of the most fundamental basic issues of plasma physics, the stability analysis of an electron beam-plasma system is of critical relevance in many areas of physics. Surprisingly, decades of extensive investigation had not yet resulted in a realistic unified picture of the multidimensional unstable spectrum within a fully relativistic and kinetic framework. All attempts made so far in this direction were indeed restricted to simplistic distribution functions and/or did not aim at a complete mapping of the beam-plasma parameter space. The present paper comprehensively tackles this problem by implementing an exact linear model. We show that three kinds of modes compete in the linear phase, which can be classified according to the direction of their wavenumber with respect to the beam. We then determine their respective domain of preponderance in a three-dimensional parameter space. All these results are supported by multidimensional particle-in-cell simulations.

A. Bret; L. Gremillet; D. Benisti; E. Lefebvre

2008-05-07

349

NASA Astrophysics Data System (ADS)

The task was to provide an analytical elementary magnetosphere-like model in kinetics for verification of the 3D EM PIC codes created for space/aerospace and HED plasmas applications. Kinetic approach versus cold MHD approach takes into account different behavior in the EM fields of resonant and non resonant particles in the velocity phase space, which appears via shape characteristics of the particle velocity distribution function (PVDF) and via the spatial dispersion effect forming the collisionless dissipation in the EM fields. The external flow is a hot collisionless plasma characterized by the particle velocity distribution function (PVDF) with different shapes: Maxwellian, kappa, etc. The flow is in a “hot regime”: it can be supersonic but its velocity remains less the thermal velocity of the electrons. The “internal” part of the magnetosphere formed by trapped particles is the prescribed 3D stationary magnetization considered as a spherical “quasiparticle” with internal magnetodipole and toroidal moments represented as a broadband EM driver. We obtain after the linearization of Vlasov/Maxwell equations a self-consistent 3D large scale kinetic solution of the classic problem. Namely, we: model the “outer” part of the magnetosphere formed by external hot plasma flow of the flyby particles. Solution of the Vlasov equation expressed via a tensor of dielectric permittivity of nonmagnetized and magnetized flowing plasma. Here, we obtain the direct kinetic dissipative effect of the magnetotail formation and the opposite diamagnetic effect of the magnetosphere “dipolization”. We get MHD wave cone in flow magnetized by external guiding magnetic (GM) field. Magnetosphere in our consideration is a 3D dissipative “wave” package structure of the skinned EM fields formed by the “waves” excited at frequency bands where we obtain negative values and singularities (resonances) of squared EM refractive index of the cold plasma. The hot regime provides kinetic effects near singularities depending from reshaping of the PVDF. Flow behaves as metal with generation of inductive conductive currents or as dielectric with diamagnetic polarization currents. The basic high beta flow regime is equivalent to the absence of the GM field, nonmagnetized plasma flow particles, and operation with a diagonal tensor, that is, the Chapman approach to magnetosphere modeling considered often as “minimagnetosphere” modeling. The magnetosphere formation is the wide band Cerenkov resonance effect of interaction of the magnetization with “resonant” and “nonresonant” plasma flow particles. We also obtain the resistive (“thin”) scale of anomalous skin which is related with process of resonant particle acceleration by inductive fields providing EM dissipation and the effect of magnetic reconnection. We get also the diamagnetic (“thick”) scale which is related to the magnetic field action on the plasma flow particles. The ratio of the diamagnetic to resistive current densities in the 3D magnetosphere forms the flow quality parameter G. The EM value G depends on the shape of the PDF of the incoming flow only. The parameter G characterizes the EM part of the “space weather”. For the Maxwellian PDF G is much less then 1 - metal-like flow and the formation of the magnetotail state, reshaping PDF to G more then 1 - diamagnetic flow, which provides a transition to the dipolized state. Note that the acoustic Mach number characterizes the SW compressibility and the shock wave formation effect only. The low-beta hot-flow regime is equivalent to the magnetized by the GM field plasma flow (Dangey approach). Here, the tensor is non diagonal, and by the GM field action plasma became MHD transparent in the nontransparent band, which provides MHD radiation in the Alvenic cone. Negative values of the squared refractive index are at the cyclotron and at the modified Cerenkov EM narrow band frequency resonances for the EM fields with ordinary and non ordinary polarizations. This takes place for the packages with the “waves”

Gubchenko, Vladimir

350

This study was designed to compare the kinetics of sperm survival in different types of bull semen. Fresh ejaculates from four bulls were pooled, diluted in Tris-citric acid-egg yolk-glycerol extender, cooled to 4°C, frozen in LN2 and thawed at 37°C. Fresh, diluted, cooled and frozen-thawed semen were incubated at 37°C, and evaluated at 0, 2, 4, 6, 12 and 24h after the beginning of incubation. In Experiment 1, progressive sperm motility, normal acrosomes and plasma membrane integrity and asymmetry were determined. In Experiment 2, generation of superoxide anion (O2•) along with plasma membrane permeability and generation of hydrogen peroxide (H2O2) along with plasma membrane integrity were assessed. In Experiment 1, frozen-thawed semen had shorter survival times for progressive sperm motility, and spermatozoa with intact plasma membranes and acrosomes (IPM-IACR) as compared with other types of semen (P2•- generation and increased plasma membrane permeability, and became necrotic without H2O2 generation during incubation (P2•-, which increased the permeability and compromised the integrity of the plasma membrane. PMID:24576435

Ahmad, Mushtaq; Ahmad, Nasim; Riaz, Amjad; Anzar, Muhammad

2014-02-28

351

Energetic particle physics with applications in fusion and space plasmas

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

352

The energy transport by radiation is one of the most important effects in an electrothermal-chemical (ETC) accelerator. At the beginning of the ETC round, after the initiation of the plasma e.g. by an exploding wire, the plasma radiation is responsible for the ignition of the propellant and the observed enhancement of mass production. This could be validated by different closed

Klaus Kappen; Uwe H. Bauder

2001-01-01

353

NASA Astrophysics Data System (ADS)

A minimum model of plasma turbulence in a kinetic framework is presented. It is based on trapped ion turbulence, gyro and bounce averaged, and implemented in the versatile and efficient code TERESA. Zonal flow - streamer interplay are readily shown to be key players that govern the confinement properties of the model. The parameter space of the model is explored with brute force numerics. A generic result is either a streamer dominated pattern with large transport, or a staircase temperature profile with very marked corrugations and quenched transport. A case with off-axis heating is found to exhibit quasiperiodic relaxation events relevant to investigate dynamical turbulence self-organisation.

Cartier-Michaud, T.; Ghendrih, P.; Sarazin, Y.; Dif-Pradalier, G.; Drouot, T.; Estève, D.; Garbet, X.; Grandgirard, V.; Latu, G.; Norscini, C.; Passeron, C.

2014-11-01

354

NASA Astrophysics Data System (ADS)

Electron Cyclotron Resonance (ECR) ion Sources are the most performing machines for the production of intense beams of multi-charged ions in fundamental science, applied physics and industry. Investigation of plasma dynamics in ECRIS still remains a challenge. A better comprehension of electron heating, ionization and diffusion processes, ion confinement and ion beam formation is mandatory in order to increase ECRIS performances both in terms of output beams currents, charge states, beam quality (emittance minimization, beam halos suppression, etc.). Numerical solution of Vlasov equation via kinetic codes coupled to FEM solvers is ongoing at INFN-LNS, based on a PIC strategy. Preliminary results of the modeling will be shown about wave-plasma interaction and electron-ion confinement: the obtained results are very helpful to better understand the influence of the different parameters (especially RF frequency and power) on the ion beam formation mechanism.

Mascali, David; Torrisi, Giuseppe; Neri, Lorenzo; Sorbello, Gino; Castro, Giuseppe; Celona, Luigi; Gammino, Santo

2015-01-01

355

Coupled electron and ion nonlinear oscillations in a collisionless plasma

Dynamics of coupled electrostatic electron and ion nonlinear oscillations in a collisionless plasma is studied with reference to a kinetic description. Proceeding from the exact solution of Vlasov-Maxwell equations written as a function of linear functions in the electron and ion velocities, we arrive at the two coupled nonlinear equations which describe the evolution of the system.

Karimov, A. R. [Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya 13/19, Moscow 127412, Russia and Department of Electrophysical Facilities, National Research Nuclear University MEPhI, Kashirskoye shosse 31, Moscow 115409 (Russian Federation)] [Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya 13/19, Moscow 127412, Russia and Department of Electrophysical Facilities, National Research Nuclear University MEPhI, Kashirskoye shosse 31, Moscow 115409 (Russian Federation)

2013-05-15

356

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

2013-03-01

357

To explore the effect of type of dietary fat, cholesterol and chenodeoxycholic acid on gallstone formation, bile formation, bile composition, bile acid kinetics and plasma lipids in squirrel monkeys, 39 monkeys were studied using seven different diets. Safflower oil, a highly unsaturated fat, added to a diet with cholesterol resulted in at least as high an incidence of cholesterol gallstones as butter added to the same diet. On the other hand, diets with high levels of saturated or unsaturated fat without cholesterol did not result in gallstone formation. Dietary chenodeoxycholic acid (0.1%) did not reduce the incidence of cholesterol gallstones, although the proportion of bile acids as chenodeoxycholic acid increased. Gallbladder biles from monkeys fed semipurified diets with cholesterol had a significantly higher lithogenic index than the comparable groups without cholesterol. Pool sizes of bile acids in all semipurified diet groups were reduced and the lithogenic indices were increased compared with the group fed a commercial feed. Dietary chenodeoxycholic acid caused a decrease in plasma cholesterol in butter groups and an increase in triglyceride concentrations in safflower groups. Diet infuences bile composition and bile acid kinetics, as well as the incidence of gallstones, in squirrel monkeys. PMID:820839

Tanaka, N; Portman, O W; Osuga, T

1976-08-01

358

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

359

1 Treatment of methyl t-butyl ether contaminated water using a dense medium plasma reactor-7369 Email: david.dandy@colostate.edu Abstract Plasma treatment of contaminated water appears reactor configurations and two pin array spin rates. The oxidation products from the treatment of MTBE

Dandy, David

360

NASA Technical Reports Server (NTRS)

The objectives, equipment, and techniques for the plasma diagnostics package (PDP) carried by the OSS-1 instrument payload of the STS-4 and scheduled for the Spacelab-2 mission are described. The goals of the first flight were to examine the Orbiter-magnetoplasma interactions by measuring the electric and magnetic field strengths, the ionized particle wakes, and the generated waves. The RMS was employed to lift the unit out of the bay in order to allow characterization of the fields, EM interference, and plasma contamination within 15 m of the Orbiter. The PDP will also be used to examine plasma depletion, chemical reaction rates, waves, and energized plasma produced by firing of the Orbiter thrusters. Operation of the PDP was carried out in the NASA Space Environment Simulation Laboratory test chamber, where the PDP was used to assay the fields, fluxes, wave amplitudes, and particle energy spectra. The PDP instrumentation is also capable of detecting thermal ions, thermal electrons suprathermal particles, VHF/UHF EMI levels, and the S-band field strength.

Shawhan, S. D.

1982-01-01

361

Intravirion reverse transcripts have been identified in the blood plasma of human immunodeficiency virus type 1 (HIV-1)-infected individuals. In the present studies, the kinetic processes of intravirion HIV-1 reverse transcription, in the blood plasma of HIV-1-infected persons treated with nevirapine, were investigated. Nevirapine is a nonnucleoside inhibitor of reverse transcriptase (RT) which decreases the level of HIV-1 viral particles in the blood plasma of infected individuals. By analyzing HIV-1 virions at different time points prior to and after initiation of nevirapine therapy in vivo, the levels of intravirion reverse transcripts have been demonstrated to be dramatically susceptible to this anti-RT agent, out of proportion to effects on plasma virion load. The intravirion reverse transcripts were also documented to rebound to the pretreatment levels, concomitant with the development of resistant viral mutants. In addition, the infectivity of HIV-1 virions dramatically decreased after nevirapine treatment, further indicating that the effects of this anti-RT agent begin within the cell-free virions. Since the levels of intravirion reverse transcripts were altered according to the susceptibility or resistance of the HIV-1 RT enzyme to this inhibitor, these data demonstrate that the formation of intravirion reverse transcripts is a dynamic process in vivo. Moreover, because the alteration in ratios between intravirion HIV-1 reverse transcripts and viral genomic RNA directly reflects the efficiency of reverse transcription, we propose that the determination of these ratios in the blood plasma of HIV-1-positive patients may be a useful and, most importantly, a direct assay to monitor the efficacy of anti-RT agents in vivo. PMID:8523584

Zhang, H; Dornadula, G; Wu, Y; Havlir, D; Richman, D D; Pomerantz, R J

1996-01-01

362

A Multi Water Bag model of drift kinetic electron plasmaa

NASA Astrophysics Data System (ADS)

A Multi Water Bag model is proposed for describing drift kinetic plasmas in a magnetized cylindrical geometry, relevant for various experimental devices, solar wind modeling... The Multi Water Bag (MWB) model is adapted to the description of a plasma with kinetic electrons as well as an arbitrary number of kinetic ions. This allows to describe the kinetic dynamics of the electrons, making possible the study of electron temperature gradient (ETG) modes, in addition to the effects of non adiabatic electrons on the ion temperature gradient (ITG) modes, that are of prime importance in the magnetized plasmas micro-turbulence [X. Garbet, Y. Idomura, L. Villard, T.H. Watanabe, Nucl. Fusion 50, 043002 (2010); J.A. Krommes, Ann. Rev. Fluid Mech. 44, 175 (2012)]. The MWB model is shown to link kinetic and fluid descriptions, depending on the number of bags considered. Linear stability of the ETG modes is presented and compared to the existing results regarding cylindrical ITG modes [P. Morel, E. Gravier, N. Besse, R. Klein, A. Ghizzo, P. Bertrand, W. Garbet, Ph. Ghendrih, V. Grandgirard, Y. Sarazin, Phys. Plasmas 14, 112109 (2007)].

Morel, Pierre; Ghiro, Florent Dreydemy; Berionni, Vincent; Coulette, David; Besse, Nicolas; Gürcan, Özgür D.

2014-08-01

363

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...

364

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 the Tokamak Fusion Test Reactor (TFTR) [D. J. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)], with reversed magnetic shear regions in the plasma interior. The high-n toroidal drift modes destabilized by the combined

G. Rewoldt; M. A. Beer; M. S. Chance; T. S. Hahm; Z. Lin; W. M. Tang

1998-01-01

365

NASA Astrophysics Data System (ADS)

We unravel the complex chemistry in both the neutral and ionic systems of a radio-frequency-driven atmospheric-pressure plasma in a helium-oxygen mixture (He-0.5% O2) with air impurity levels from 0 to 500 ppm of relative humidity from 0% to 100% using a zero-dimensional, time-dependent global model. Effects of humid air impurity on absolute densities and the dominant production and destruction pathways of biologically relevant reactive neutral species are clarified. A few hundred ppm of air impurity crucially changes the plasma from a simple oxygen-dependent plasma to a complex oxygen-nitrogen-hydrogen plasma. The density of reactive oxygen species decreases from 1016 to 1015 cm-3, which in turn results in a decrease in the overall chemical reactivity. Reactive nitrogen species (1013 cm-3), atomic hydrogen and hydroxyl radicals (1011-1014 cm-3) are generated in the plasma. With 500 ppm of humid air impurity, the densities of positively charged ions and negatively charged ions slightly increase and the electron density slightly decreases (to the order of 1011 cm-3). The electronegativity increases up to 2.3 compared with 1.5 without air admixture. Atomic hydrogen, hydroxyl radicals and oxygen ions significantly contribute to the production and destruction of reactive oxygen and reactive nitrogen species.

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

2013-08-01

366

NASA Astrophysics Data System (ADS)

The ``hybrid'' and ``steady-state'' advanced scenarios are characterized by q profiles higher or equal to one to mitigate plasma instabilities and improve confinement, which are key for ITER to achieve its operational objectives. To achieve these scenarios, active model-based control of the current profile and thermal state of the plasma is required. Towards this goal, two control-oriented, plasma-response models are proposed. First, the poloidal flux diffusion equation is combined with empirical models of the electron density and temperature profiles, plasma resistivity, and non-inductive current drives to obtain a physics-based model of the poloidal flux and stored energy evolutions. Second, the empirical electron temperature model is replaced by the electron heat transport equation, which is combined with empirical models of the electron heat conductivity and heat sources to obtain a physics-based model of the poloidal flux and electron temperature evolutions. Simulation results comparing the evolution of the plasma parameters predicted by the control-oriented, physic-based models and the DINA-CH+CRONOS simulation code are presented for ITER, and the control objectives and challenges are discussed.

Barton, Justin E.; Schuster, Eugenio; Besseghir, Karim; Lister, Jonathan

2012-10-01

367

NASA Astrophysics Data System (ADS)

The linearized dispersion relation describing waves in a plasma having a uniform magnetic field, uniform density, and shear in parallel (to the field) flow [G. Ganguli, M.J. Keskinen, H. Romero, R. Heelis, T. Moore, and C. Pollock, J. Geophys. Res., 99, 8873, 1994.] is generalized to include thermal anisotropy, a key feature existing in many space and laboratory plasmas. The effects of thermal anisotropy on the ion acoustic mode and the ion cyclotron mode are examined. The growth rate of the ion acoustic mode is shown to increase with T_i/T_i, and the real frequency at which the maximum growth rate occurs is shown to upshift significantly. The angle that an ion acoustic wave propagates is also shown to depend onT_i/T_i. The growth rate for the ion cyclotron mode is shown to increase with T_i/T_iin the presence of inhomogeneous flow, and the real frequency is not significantly affected. Also presented is a generalized calculation of perturbed distribution functions [Sarfaty, M., S. DeSouza Machado, F. Skiff, Phys. Plasmas, 3, 4316, (1996); Skiff, F., IEEE Transactions of Plasma Science, 20, 701 (1992)] to include shear in field-aligned flow. Without shear, the first order perturbed distribution as a function of ? is independent of the orientation of the wavevector in the plane perpendicular to the background magnetic field. A method of determining the wavevector components present in a plasma with shear in the parallel flow is presented.

Spangler, Robert S.; Scime, E. E.; Ganguli, G.

2001-10-01

368

NASA Astrophysics Data System (ADS)

Wave-particle interactions play a very important role in the plasma dynamics near Titan: mass loading, excitation of the low-frequency waves and the formation of the particle velocity distribution function, e.g. ring/shell-like distributions, etc. The kinetic approach is important for estimation of the collision processes e.g. a charge exchange. The particle velocity distribution function also plays a key role for understanding the observed particle fluxes. In this report we discuss the ion velocity distribution function dynamics from 3D hybrid modeling. The modeling is based on recent analysis of the Cassini Plasma Spectrometer (CAPS) ion measurements during the TA flyby. In our model the background ions, all pickup ions, and ionospheric ions are considered as particles, whereas the electrons are described as a fluid. Inhomogeneous photoionization, electron-impact ionization and charge exchange are included in our model. The temperatures of the background electrons and pickup electrons were also included into the generalized Ohm's law. We also take into account the collisions between the ions and neutrals. We use Chamberlain profiles for the exosphere's components and include a simple ionosphere model with M=28 ions that were generated inside the ionosphere. The moon is considered as a weakly conducting body. Our modeling shows that interaction between background plasma and pickup ions H+, H2+, CH4+ and N2+ has a more complicated structure than was observed in the T9 flyby and modeling due to the large gyroradius of the background O+ ions [1,2,3,4]. Special attention will be paid to comparing the simulated pickup ion velocity distribution with CAPS TA observations. We also compare our kinetic modeling with other hybrid and MHD modeling of Titan's environment. References [1] Sittler, E.C., et al., Energy Deposition Processes in Titan's Upper Atmosphere and Its Induced Magnetosphere. In: Titan from Cassini-Huygens, Brown, R.H., Lebreton J.P., Waite, J.H., Eds., Springer, (Dordrecht, Heidelberg, London, New York, pp. 393-455, 2009). [2] Sittler, E.C., et al., Saturn's Magnetospheric Interaction with Titan as Defined by Cassini Encounters T9 and T18: New Results, Planet. Space Sci., doi.10.1016/j.pss.2009.09.017. [3] Coates, A.J., Interaction of Titan's ionosphere with Saturn's magnetosphere. Phil. Trans. R. Soc. A (2009) 367, 773-788, doi: 10.1098/rsta.2008.0248. [4] Lipatov, A.S., et al., Background and pickup ion velocity distribution dynamics in Titan's plasma environment: 3D hybrid simulation and comparison with CAPS T9 observations. Adv. Space Res. 48, 1114-1125, 2011.

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

2013-12-01

369

NASA Astrophysics Data System (ADS)

We report the interplay between In incorporation and strain relaxation kinetics in high-In-content InxGa1-xN (x = 0.3) layers grown by plasma-assisted molecular-beam epitaxy. For In mole fractions x = 0.13-0.48, best structural and morphological qualities are obtained under In excess conditions, at In accumulation limit, and at a growth temperature where InGaN decomposition is active. Under such conditions, in situ and ex situ analyses of the evolution of the crystalline structure with the layer thickness point to an onset of misfit relaxation after the growth of 40 nm, and a gradual relaxation during more than 200 nm, which results in an inhomogeneous strain distribution along the growth axis. This process is associated with a compositional pulling effect, i.e., indium incorporation is partially inhibited in presence of compressive strain, resulting in a compositional gradient with increasing In mole fraction towards the surface.

Valdueza-Felip, S.; Bellet-Amalric, E.; Núñez-Cascajero, A.; Wang, Y.; Chauvat, M.-P.; Ruterana, P.; Pouget, S.; Lorenz, K.; Alves, E.; Monroy, E.

2014-12-01

370

A kinetic model of the processes occurring in the plasma of a high-power low-pressure gas-discharge lamp is presented, and the output characteristics of the lamp are described. The lamp is excited by a longitudinal glow discharge and emits the I{sub 2}(D Prime -A Prime ) 342-nm and XeI(B-X) 253-nm bands and the 206.2-nm spectral line of atomic iodine. When the emitter operates in a sealed-off mode on the p(He): p(Xe): p(I{sub 2}) = 400: 120: (100-200) Pa mixture, the fractions of the UV radiation power of iodine atoms, exciplex molecules of xenon iodide, and iodine molecules comprise 55, 10, and 35%, respectively. At the optimal partial pressure, the maximum total radiation power of the lamp reaches 37 W, the energy efficiency being about 15%.

Shuaibov, A. K.; Grabovaya, I. A.; Minya, A. I.; Homoki, Z. T. [Uzhgorod National University (Ukraine); Kalyuzhnaya, A. G.; Shchedrin, A. I. [National Academy of Sciences of Ukraine, Institute of Physics (Ukraine)

2011-03-15

371

NASA Astrophysics Data System (ADS)

The current study shows the dramatic effect of an electric field (EF) and use of nanosized cryomilled grains on accelerating sintering kinetics during spark plasma sintering of blended elemental powder compacts of Ti53Al47 targeted to produce ?-TiAl intermetallic compounds. The EF had the dominating effect since it reduced the activation barrier for diffusion through Al3Ti leading to faster growth of Al3Ti; the precursor to ?-TiAl. The Avrami exponent ( n) determined for the micrograin compact lies between 1.0 and 1.5, which indicates that reaction sintering is controlled by bulk diffusion in these compacts, while for cryomilled compacts this is between 0.7 and 1.0 suggesting the important role of dislocations and grain boundaries on the transformation during reaction sintering. The activation energies were found to be in increasing order as: cryomilled compacts with EF (182 kJ/mol); micrograin compacts with EF (290 kJ/mol); cryomilled compacts without EF (331 kJ/mol); and micrograin compacts without EF (379 kJ/mol). The cryomilled microstructure also enhanced the sintering kinetics because of the availability of faster diffusing paths in Al and Ti including larger grain boundary area and dislocation density.

Sun, Yu; Kulkarni, Kaustubh; Sachdev, Anil K.; Lavernia, Enrique J.

2014-06-01

372

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

G. Rewoldt; M. S. Chance; T. S. Hahm; W. M. Tang

1997-01-01

373

Esters of the cytostatic bendamustine (1), previously demonstrated to be much more potent than the parent compound as antiproliferative agents in vitro, were investigated for stability in buffer and plasma, as well as against porcine liver esterase in the presence of different amounts of albumin using a validated RP-HPLC method with fluorescence detection. The hydrolysis of the nitrogen mustard moiety was retarded (for 1: approximately 130 vs. 11 min) in the presence of plasma proteins. For the derivatives, both cleavage of ester and nitrogen mustard moieties were analyzed. Enzymatic hydrolysis was very fast in the case of 2-pyrrolidino-, 2-piperidino- and 2-(4-methylpiperazino)-ethyl esters, whereas methyl, ethyl, morpholinoethyl and branched 2-pyrrolidinoethyl esters were considerably more stable (half-lives between 41 and 116 min, compared to <5 min). Inhibition by physostigmine indicated unspecific cholinesterases to be involved in the rapid ester cleavage. Due to lower protein content and higher enzymatic activity in murine compared to human plasma, reduced stability of all investigated esters in mouse plasma (t½<2 min) has to be taken into account with respect to the design of animal studies. PMID:25499654

Huber, S; Antoni, F; Schickaneder, C; Schickaneder, H; Bernhardt, G; Buschauer, A

2015-02-01

374

We present new results on the physics of short-pulse laser-matter interaction of kilojoule-picosecond pulses at full spatial and temporal scale, using a new approach that combines a 3D collisional electromagnetic Particle-in-Cell code with an MHD-hybrid model of high-density plasma. In the latter, collisions damp out plasma waves, and an Ohm's law with electron inertia effects neglected determines the electric field. In addition to yielding orders of magnitude in speed-up while avoiding numerical instabilities, this allows us to model the whole problem in a single unified framework: the laser-plasma interaction at sub-critical densities, energy deposition at relativistic critical densities, and fast-electron transport in solid densities. Key questions such as the multi-picosecond temporal evolution of the laser energy conversion into hot electrons, the impact of return currents on the laser-plasma interaction, and the effect of self-generated electric and magnetic fields on electron transport will be addressed. We will report applications to current experiments.

Kemp, A; Cohen, B; Divol, L

2009-11-16

375

NASA Astrophysics Data System (ADS)

Transient Reflected Microwave Conductivity (TRMC) measurements after laser pulse excitation have been performed during processing of thin film semiconductors. In particular PECVD-deposition of hydrogenated amorphous silicon (a-Si:H) and etching of the a-Si:H films in a hydrogen plasma has been studied by this non-invasive technique for the determination of excess charge carrier concentrations, mobilities, and lifetimes. During the growth of two intrinsic amorphous silicon layers deposited under different plasma conditions on top of each other, the comparison of the photoconducting properties of these layers already during deposition is shown and compared to conventional ex-situ characterization. By analyzing the interference fringes seen in the TRMC-amplitude during amorphous silicon growth and etching on crystalline silicon wafers covered by a dielectric layer an in-situ thickness control of the a-Si:H film has been achieved. Interface characterization in double layer structures with amorphous silicon deposited on top of crystalline silicon gave an estimation of the interface recombination rate and its change during the a-Si:H growth. An evaluation of the plasma induced damage in the initial stage of the silane plasma process is demonstrated. It has been found that already a very thin layer of a-Si:H inhibits the further defect creation at the surface of the crystalline silicon.

Neitzert, Heinz-Christoph

1993-11-01

376

Technology Transfer Automated Retrieval System (TEKTRAN)

Background: The search for a reliable, convenient indicator of Zn status has been the focus of research for several decades. Plasma Zn concentration is still the most widely used clinical measurement, despite the known problems of interpretation. More recently, it has been sugggested that isotopi...

377

We present new results on the physics of short-pulse laser-matter interaction of kilojoule-picosecond pulses at full spatial and temporal scale using a new approach that combines a three-dimensional collisional electromagnetic particle-in-cell code with a magnetohydrodynamic-hybrid model of high-density plasma. In the latter, collisions damp out plasma waves, and an Ohm's law with electron inertia effects neglected determines the electric field. In addition to yielding orders of magnitude in speed-up while avoiding numerical instabilities, this allows us to model the whole problem in a single unified framework: the laser-plasma interaction at subcritical densities, energy deposition at relativistic critical densities, and fast- electron transport in solid densities. Key questions such as the multipicosecond temporal evolution of the laser energy conversion into hot electrons, the impact of return currents on the laser-plasma interaction, and the effect of self-generated electric and magnetic fields on electron transport will be addressed. We will report applications to current experiments.

Kemp, A. J.; Cohen, B. I.; Divol, L. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2010-05-15

378

NASA Astrophysics Data System (ADS)

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.; Zhuravlev, I. A.

2012-10-01

379

NASA Astrophysics Data System (ADS)

As-deposited HfO2 films were modified by CHF3, C4F8, and mixed C4F8/O2 plasmas in a dual-frequency capacitively coupled plasma chamber driven by radio frequency generators of 60 MHz as the high frequency (HF) source and 2 MHz as the low frequency source (60/2 MHz). The influences of various surface plasma treatments under CHF3, C4F8, and C4F8/O2 were investigated in order to understand the chemical and structural changes in thin-film systems, as well as their influence on the electrical properties. Fluorine atoms were incorporated into the HfO2 films by either CHF3 or C4F8 plasma treatment; meanwhile, the C/F films were formed on the surface of the HfO2 films. The formation of C/F layers decreased the k value of the gate stacks because of its low dielectric constant. However, the addition of O2 gas in the discharge gases suppressed the formation of C/F layers. After thermal annealing, tetragonal HfO2 phase was investigated in both samples treated with CHF3 and C4F8 plasmas. However, the samples treated with O-rich plasmas showed monoclinic phase, which indicated that the addition of O plasmas could influence the Hf/O ratio of the HfO2 films. The mechanism of the t-HfO2 formation was attributed to oxygen insufficiency generated by the incorporation of F atoms. The capacitors treated with C4F8/O2 plasmas displayed the highest k value, which ascribed that the C/F layers were suppressed and the tetragonal phase of HfO2 was formed. Good electrical properties, especially on the hysteresis voltage and frequency dispersion, were obtained because the bulk traps were passivated by the incorporation of F atoms. However, the H-related traps were generated during the CHF3 plasma treatments, which caused the performance degradation. All the treated samples showed lower leakage current density than the as-deposited HfO2 films at negative bias due to the reduced trap-assisted tunneling by the incorporation of F to block the electrons transferring from metal electrode to the trap level.

Zhang, H. Y.; Jin, C. G.; Yang, Y.; Ye, C.; Zhuge, L. J.; Wu, X. M.

2014-12-01

380

NASA Astrophysics Data System (ADS)

The linearized dispersion relation describing waves in a plasma having a uniform magnetic field, uniform density, and shear in parallel (to the field) flow [G. Ganguli, M.J. Keskinen, H. Romero, R. Heelis, T. Moore, and C. Pollock, J. Geophys. Res., 99, 8873, 1994.] is generalized to include thermal anisotropy, a key feature existing in many space and laboratory plasmas. The effects of thermal anisotropy on the ion acoustic mode and the ion cyclotron mode are examined. The growth rate of the ion acoustic mode is shown to increase with the ion perpendicular to parallel temperature ratio, and the real frequency at which the maximum growth rate occurs is shown to upshift significantly. The angle that an ion acoustic wave propagates is also shown to depend on the temperature ratio. The growth rate for the ion cyclotron mode is shown to increase with the perpendicular to parallel ion temperature ratio in the presence of inhomogeneous flow, and the real frequency is not significantly affected. Also presented is a generalized calculation of perturbed distribution functions [Sarfaty, M., S. DeSouza Machado, F. Skiff, Phys. Plasmas, 3, 4316, (1996); Skiff, F., IEEE Transactions of Plasma Science, 20, 701 (1992)] to include shear in field-aligned flow. Without shear, the first order perturbed distribution as a function of is independent of the orientation of the wavevector in the plane perpendicular to the background magnetic field. A method of determining the wavevector components present in a plasma with shear in the parallel flow is presented. The new results are applicable to the FAST mission.

Spangler, R. S.; Scime, E. E.; Ganguli, G. I.

2001-12-01

381

Steady-state plasma levels of ketamine and its metabolites norketamine and dehydronorketamine were determined in 4 different groups of a total of 27 patients with ketamine long-term analgosedation (1.1 - 1.3 mg/kg/h). In 9 of the patients who had normal liver and kidney function (group 1), steady-state levels after 3 days of continuous infusion were 1.2 +/- 0.3 micrograms/ml ketamine, 1.0 +/- 0.6 micrograms/ml norketamine, and 2.6 +/- 1.0 micrograms/ml dehydronorketamine. The measured ketamine levels in group 1 were in agreement with the expected value, which may be calculated from published pharmacokinetic data after bolus injection. In 8 patients with acute renal failure (group 2), a tendency to about 20% higher ketamine steady-state plasma levels compared to group 1 was observed, but this difference was not significant. However, dehydronorketamine plasma levels were significantly higher in this group. Only a minor fraction of the ketamine dose (10% and 4%) was eliminated during hemodialysis or hemofiltration treatment, respectively. Steady-state plasma levels in 5 patients with cardiogenic shock (group 3) did not differ significantly from those of group 1. In 5 patients with long-term use of barbiturates (group 4), steady-state plasma levels of ketamine were significantly lower compared to groups 1 and 3, most likely due to barbiturate-induced enzyme induction. Hyperdynamic circulatory reactions were not observed in any of the patients. Psychomimetic effects could be excluded in 16 of the patients and were unlikely in 6 patients. In 5 further patients, psychomimetic effects could not definitely be excluded due to difficulties in non-verbal communication. PMID:2253657

Köppel, C; Arndt, I; Ibe, K

1990-01-01

382

NASA Technical Reports Server (NTRS)

LSENS, the Lewis General Chemical Kinetics and Sensitivity Analysis Code, has been developed for solving complex, homogeneous, gas-phase chemical kinetics problems and contains sensitivity analysis for a variety of problems, including nonisothermal situations. This report is part II of a series of three reference publications that describe LSENS, provide a detailed guide to its usage, and present many example problems. Part II describes the code, how to modify it, and its usage, including preparation of the problem data file required to execute LSENS. Code usage is illustrated by several example problems, which further explain preparation of the problem data file and show how to obtain desired accuracy in the computed results. LSENS is a flexible, convenient, accurate, and efficient solver for chemical reaction problems such as static system; steady, one-dimensional, inviscid flow; reaction behind incident shock wave, including boundary layer correction; and perfectly stirred (highly backmixed) reactor. In addition, the chemical equilibrium state can be computed for the following assigned states: temperature and pressure, enthalpy and pressure, temperature and volume, and internal energy and volume. For static problems the code computes the sensitivity coefficients of the dependent variables and their temporal derivatives with respect to the initial values of the dependent variables and/or the three rate coefficient parameters of the chemical reactions. Part I (NASA RP-1328) derives the governing equations and describes the numerical solution procedures for the types of problems that can be solved by LSENS. Part III (NASA RP-1330) explains the kinetics and kinetics-plus-sensitivity-analysis problems supplied with LSENS and presents sample results.

Radhakrishnan, Krishnan; Bittker, David A.

1994-01-01

383

Polarization and Compressibility of Oblique Kinetic Alfven Waves

NASA Technical Reports Server (NTRS)

Even though solar wind, as a collisionless plasma, is properly described by the kineticMaxwell-Vlasov description, it can be argued that much of our understanding of solar wind observational data comes from an interpretation and numerical modeling which is based on a fluid description of magnetohydrodynamics. In recent years, there has been a significant interest in better understanding the importance of kinetic effects, i.e. the differences between the kinetic and usual fluid descriptions. Here we concentrate on physical properties of oblique kinetic Alfvn waves (KAWs), which are often recognized as one of the key ingredients in the solar wind turbulence cascade. We use three different fluid models with various degrees of complexity and calculate polarization and magnetic compressibility of oblique KAWs (propagation angle q = 88), which we compare to solutions derived from linear kinetic theory. We explore a wide range of possible proton plasma b = [0.1,10.0] and a wide range of length scales krL = [0.001,10.0]. It is shown that the classical isotropic two-fluid model is very compressible in comparison with kinetic theory and that the largest discrepancy occurs at scales larger than the proton gyroscale. We also show that the two-fluid model contains a large error in the polarization of electric field, even at scales krL 1. Furthermore, to understand these discrepancies between the two-fluid model and the kinetic theory, we employ two versions of the Landau fluid model that incorporate linear low-frequency kinetic effects such as Landau damping and finite Larmor radius (FLR) corrections into the fluid description. It is shown that Landau damping significantly reduces the magnetic compressibility and that FLR corrections (i.e. nongyrotropic contributions) are required to correctly capture the polarization.We also show that, in addition to Landau damping, FLR corrections are necessary to accurately describe the damping rate of KAWs. We conclude that kinetic effects are important even at scales which are significantly larger than the proton gyroscale krL 1.

Hunana, Peter; Goldstein, M. L.; Passot, T.; Sulem, P. L.; Laveder, D.; Zank, G. P.

2012-01-01

384

Beginning at an introductory level, this text presents a thorough treatment of plasma physics, including an extensive discussion of its applications in thermonuclear fusion research. A novel feature of this book is its comprehensive description of the various concepts and formulas widely used in fusion theory based on the fundamental equations of the plasma fluid. The physics of fusion plasmas

Kyoji Nishikawa; Masashiro Wakatani

1990-01-01

385

A steady state chemical kinetic model is developed to describe the conduction of electrical current between two probes, of relatively large surface area, immersed in a fast flowing plasma by the mechanism of charge transfer through a gas of Rydberg atoms. It correctly predicts the shape of current-voltage profiles which are similar to those of Langmuir, or floating double probe measurements. The difference is that the plateau current at the probe reflects the transport limited ion current at the cathodic electrode, even when the probe is being scanned in the anodic region. The sharp gradient leading up to the plateau of the I-V curve is associated with the field dependence of the efficiency of Rydberg atom ionisation, not the electron temperature. This approach gives a good qualitative explanation of experimental behaviour over a wide range of probe bias voltages and includes the occurrence of electron impact ionisation at the anode. It also gives a value for the thermal rate coefficient of symmetrical charge transfer between Rydberg atoms of Ar (8.2 x 10(-7) molecule(-1) cm(3) s(-1), at 313 K; plasma density approximately = 10(10) atoms cm(-3), total pressure = 2.7 mbar). PMID:20358036

Mason, Rod S

2010-04-21

386

Quasineutrality and parallel force balance in kinetic magnetohydrodynamics

NASA Astrophysics Data System (ADS)

Kinetic magnetohydrodynamics refers usually to the hybrid fluid and kinetic description of a zero-Larmor-radius collisionless plasma, originally formulated in the classic papers of Kruskal and Oberman (1958) (Kruskal, M. D. and Oberman, C. R. 1958 Phys. Fluids 1, 275), Rosenbluth and Rostoker (1959) (Rosenbluth, M. N. and Rostoker, N. 1959 Phys. Fluids 2, 23), and Kulsrud (1962) (Kulsrud, R. 1962 Phys. Fluids 5, 192). Such a theory is revisited here, as a special limit of the more general description put forward in Ramos (2010, 2011) (Ramos, J. J. 2010 Phys. Plasmas, 17, 082502; Ramos, J. J. 2011 Phys. Plasmas, 18, 102506). The present approach has the advantage of fulfilling the quasineutrality condition and avoiding the redundancy between the fluid and kinetic parallel force balance conditions with a built-in, rigorous account of the parallel electric field, thus affording a clear-cut handling of these issues. At zero-frequency marginal stability, the Rosenbluth-Rostoker fluid closures for the parallel and perpendicular pressures are obtained, in a solution with vanishing parallel electric field and non-zero parallel fluid displacement that satisfies exactly the desired quasineutrality and parallel force balance.

Ramos, J. J.; Ramos

2015-01-01

387

Sheared rotation dynamics are widely believed to have signficant influence on experimentally observed confinement transitions in advanced operating modes in major tokamak experiments, such as the Tokamak Fusion Test Reactor (TFTR) [D.J. Grove and D.M. Meade, Nuclear Fusion 25, 1167 (1985)], with reversed magnetic shear regions in the plasma interior. The high-n toroidal drift modes 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. Here, 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 used for a proper self-consistent treatment of this key problem. Relevant advanced operating mode cases for TFTR are presented. In addition, the complementary problem of the dynamics of fluctuation-driven E x B flow is investigated by an integrated program of gyrokinetic simulation in annulus geometry and gyrofluid simulation in flux tube geometry.

Beer, M.A.; Chance, M.S.; Hahm, T.S.; Lin, Z.; Rewoldt, G.; Tang, W.M.

1997-11-01

388

This report documents the physical models and the numerical methods employed in the BWR systems code RAMONA-3B. The RAMONA-3B code simulates three-dimensional neutron kinetics and multichannel core hydraulics of nonhomogeneous, nonequilibrium two-phase flows. RAMONA-3B is programmed to calculate the steady and transient conditions in the main steam supply system for normal and abnormal operational transients, including the performances of plant control and protection systems. Presented are code capabilities and limitations, models and solution techniques, the results of development code assessment and suggestions for improving the code in the future.

Wulff, W; Cheng, H S; Diamond, D J; Khatib-Rahbar, M

1984-01-01

389

A Landau fluid model for electromagnetic plasma microturbulence P. B. Snydera)

A Landau fluid model for electromagnetic plasma microturbulence P. B. Snydera) General Atomics, P A fluid model is developed for the description of microturbulence and transport in magnetized, long mean radius and kinetic effects. Multispecies Landau fluid equations are derived from moments

Hammett, Greg

390

A kinetic-MHD model for low frequency phenomena

A hybrid kinetic-MHD model for describing low-frequency phenomena in high beta anisotropic plasmas that consist of two components: a low energy core component and an energetic component with low density. The kinetic-MHD model treats the low energy core component by magnetohydrodynamic (MHD) description, the energetic component by kinetic approach such as the gyrokinetic equation, and the coupling between the dynamics of these two components through plasma pressure in the momentum equation. The kinetic-MHD model optimizes both the physics contents and the theoretical efforts in studying low frequency MHD waves and transport phenomena in general magnetic field geometries, and can be easily modified to include the core plasma kinetic effects if necessary. It is applicable to any magnetized collisionless plasma system where the parallel electric field effects are negligibly small. In the linearized limit two coupled eigenmode equations for describing the coupling between the transverse Alfven type and the compressional Alfven type waves are derived. The eigenmode equations are identical to those derived from the full gyrokinetic equation in the low frequency limit and were previously analyzed both analytically nd numerically to obtain the eigenmode structure of the drift mirror instability which explains successfully the multi-satellite observation of antisymmetric field-aligned structure of the compressional magnetic field of Pc 5 waves in the magnetospheric ring current plasma. Finally, a quadratic form is derived to demonstrate the stability of the low-frequency transverse and compressional Alfven type instabilities in terms of the pressure anisotropy parameter {tau} and the magnetic field curvature-pressure gradient parameter. A procedure for determining the stability of a marginally stable MHD wave due to wave-particle resonances is also presented.

Cheng, C.Z.

1991-07-01

391

Studies of particle wake potentials in plasmas

NASA Astrophysics Data System (ADS)

A detailed understanding of electron stopping and scattering in plasmas with variable values for the number of particles within a Debye sphere is still not at hand. Presently, there is some disagreement in the literature concerning the proper description of these processes. Theoretical models assume electrostatic (Coulomb force) interactions between particles and neglect magnetic effects. Developing and validating proper descriptions requires studying the processes using first-principle plasma simulations. We are using the particle-particle particle-mesh (PPPM) code ddcMD and the particle-in-cell (PIC) code BEPS to perform these simulations. As a starting point in our study, we examine the wake of a particle passing through a plasma in 3D electrostatic simulations performed with ddcMD and BEPS. In this paper, we compare the wakes observed in these simulations with each other and predictions from collisionless kinetic theory. The relevance of the work to Fast Ignition is discussed.

2011-09-01

392

NASA Astrophysics Data System (ADS)

Tungsten is a leading candidate material for the diverter in future nuclear fusion reactors. Previous experiments have demonstrated that surface defects and bubbles form in tungsten when ex- posed to helium and hydrogen plasmas, even at modest ion energies. In some regimes, between 1000K and 2000K, and for He energies below 100eV, "fuzz" like features form. The mechanisms leading to these surfaces comprised of nanometer sized tungsten tendrils which include visible helium bubbles are not currently known. The role of helium bubble formation in tendril morphology could very likely be the starting point of these mechanisms. Using Molecular dynamics (MD) simulations, the role of helium and hydrogen exposure in the initial formation mechanisms of tungsten "fuzz" are investigated. Molecular dynamics simulations are well suited to describe the time and length scales associated with initial formation of helium clusters that eventually grow to nano-meter sized helium bubbles. MD simulations also easily enable the modeling of a variety of surfaces such as single crystals, grain boundaries or "tendrils". While the sputtering yield of tungsten is generally low, previous observations of surface modification due to plasma exposure raise questions about the effects of surface morphology and sub-surface helium bubble populations on the sputtering behavior. Results of computational molecular dynamics are reported that investigate the influence of sub-surface helium bubble distributions on the sputtering yield of tungsten (100) and (110) surfaces induced by helium ion exposure in the range of 300 eV to 1 keV. The calculated sputtering yields are in reasonable agreement with a wide range of experimental data; but do not show any significant variation as a result of the pre-existing helium bubbles. Molecular dynamics simulations reveal a number of sub-surface mechanisms leading to nanometer- sized "fuzz" in tungsten exposed to low-energy helium plasmas. We find that during the bubble formation process, helium clusters create self-interstitial defect clusters in tungsten by a trap mutation process, followed by the migration of these defects to the surface that leads to the formation of layers of adatom islands on the tungsten surface. As the helium clusters grow into nanometer sized bubbles, their proximity to the surface and extremely high gas pressures can cause them to rupture the surface thus enabling helium release. Helium bubble bursting induces additional surface damage and tungsten mass loss which varies depending on the nature of the surface. We then show tendril-like geometries have surfaces that are more resilient to helium clustering and bubble formation and rupture. Finally, the study includes hydrogen to reveal the effect of a mixed 90%H-10%He plasma mix on the tungsten surface. We find that hydrogen greatly affects the tungsten surface, with a near surface hydrogen saturation layer, and that helium clusters still form and are attractive trapping sites for hydrogen. Molecular dynamics simulations have also investigated the effect of sub-surface helium bubble evolution on tungsten surface morphology. The helium bubble/tungsten surface interaction has been systematically studied to determine how parameters such as bubble shape and size, temperature, tungsten surface orientation and ligament thickness above the bubble impact bubble stability and surface evolution. The tungsten surface is roughened by a combination of adatom islands, craters and pinholes. The study provides insight into the mechanisms and conditions leading to various tungsten topology changes, most notably the formation of nanoscale fuzz. An atomistic study of the mechanisms behind initial phases of tungsten nano-fuzz growth has determined that tungsten surfaces are affected by sub-displacement energy helium and hydrogen fluxes through a series of mechanisms. Sub-surface helium atom clustering, bubble nucleation, growth and rupture lead to tungsten surface deformation. Helium clustering processes vary near grain boundaries o

Sukumar, Harikrishnan

393

NASA Technical Reports Server (NTRS)

Theoretical considerations relevant to the rate of thermal relaxation of a two-dimensional plasma in a strong uniform dc magnetic field are developed. The Vahala-Montgomery (1971) kinetic description is completed by providing a cut-off time for the time of interaction of two particles contributing to the collision term. The kinetic equation is shown to predict that thermal relaxation varies as a function of defined dimensionless time.

Hsu, J.-Y.; Joyce, G.; Montgomery, D.

1974-01-01

394

NASA Astrophysics Data System (ADS)

Measured in situ, the particle velocity distributions in the solar wind plasma reveal two distinct components: a Maxwellian (thermal) core, and a less dense but hotter suprathermal halo with a power-law distribution described by Lorentzian/Kappa distribution function. Despite this evidence, the existing attempts to parametrize anisotropic distributions and the resulting wave instabilities are limited to idealized models, which either ignore the suprathermal populations, or minimize the core, assuming it is cold. Here, a more realistic approach is identified, combining an isotropic Maxwellian core and an anisotropic bi-Kappa halo. This model is relevant at large heliocentric distances and for the slow winds, when the field-aligned strahl is less pronounced and kinetic energy densities in the core and halo are comparable. A comparative study with the cold-core-based model is performed on the electron whistler-cyclotron instability driven by the anisotropic halo. Derived exactly numerically, the instability thresholds and growth rates confirm the expectation that cyclotron instabilities are inhibited by the core thermal spread. This effect is enhanced by the increase of the halo-core relative density with heliocentric distance, suggesting that local conditions for this instability to develop at large radial distances in the solar wind are less favourable than predicted before.

Lazar, M.; Poedts, S.; Schlickeiser, R.; Dumitrache, C.

2015-01-01

395

Freeze-fracturing of Funaria hygrometrica caulonema cells leads to a cleavage within the plasma membrane. The extraplasmatic and the plasmatic fracture faces differ in their particle density. The plasmatic fracture face in caulonema tip cells or in tip cells of side branches, but never in other caulonema cells, is further characterized by the occurrence of particle rosettes. The highest density of rosettes is found at the cell apex but decreases steeply toward the cell base. The shape of the rosettes varies remarkably; 20% of them are found in an incomplete, presumably disintegrating or aggregating state. The complete rosette has a diameter of about 25 nm and consists of five to six particles. The size of the single particles varies between 4 nm to 10 nm. The rosettes are thought to posses cellulose-synthase activity. It is assumed that one rosette produces one elementary fibril; rough calculations, considering the number of rosettes and the estimated amount of cellulose produced in the tip region, indicate that an elementary fibrillar length of 900 nm is formed in 1 min by one rosette. The consequence of the kinetics on the life-time of the rosettes and the cellulose-synthase activity are discussed. PMID:24258670

Reiss, H D; Schnepf, E; Herth, W

1984-04-01

396

S-(11C)Nomifensine (S-(11C)NMF) is a positron-emitting tracer suitable for positron emission tomography, which binds to both dopaminergic and noradrenergic reuptake sites in the striatum and the thalamus. Modelling of the cerebral distribution of this drug has been hampered by the rapid appearance of glucuronide metabolites in the plasma, which do not cross the blood--brain barrier. To date, (11C)NMF uptake has simply been expressed as regional versus nonspecific cerebellar activity ratios. We have calculated a free NMF input curve from red cell activity curves, using the fact that the free drug rapidly equilibrates between red cells and plasma, while glucuronides do not enter red cells. With this free (11C)NMF input function, all regional cerebral uptake curves could be fitted to a conventional two-compartment model, defining tracer distribution in terms of (11C)NMF regional volume of distribution. Assuming that the cerebellar volume of distribution of (11C)NMF represents the nonspecific volume of distribution of the tracer in striatum and thalamus, we have calculated an equilibrium partition coefficient for (11C)NMF between freely exchanging specific and nonspecific compartments in these regions, representing its binding potential to dopaminergic or noradrenergic uptake sites (or complexes). This partition coefficient was lower in the striatum when the racemate rather than the active S-enantiomer of (11C)NMF was administered. In the striatum of patients suffering from Parkinson's disease and multiple-system atrophy, the specific compartmentation of S-(11C)NMF was significantly decreased compared with that of age-matched volunteers.

Salmon, E.; Brooks, D.J.; Leenders, K.L.; Turton, D.R.; Hume, S.P.; Cremer, J.E.; Jones, T.; Frackowiak, R.S. (Hammersmith Hospital, London (England))

1990-05-01

397

Self-consistent Equilibrium Model of Low-aspect-ratio Toroidal Plasma with Energetic Beam Ions

A theoretical model is developed which allows the self-consistent inclusion of the effects of energetic beam ions in equilibrium calculations of low-aspect-ratio toroidal devices. A two-component plasma is considered, where the energetic ions are treated using a kinetic Vlasov description, while a one-fluid magnetohydrodynamic description is used to represent the thermal plasma. The model allows for an anisotropic distribution function and a large Larmor radius of the beam ions. Numerical results are obtained for neutral-beam-heated plasmas in the National Spherical Torus Experiment (NSTX). Self-consistent equilibria with an anisotropic fast-ion distribution have been calculated for NSTX. It is shown for typical experimental parameters that the contribution of the energetic neutral-beam ions to the total current can be comparable to that of the background plasma, and that the kinetic modifications of the equilibrium can be significant. The range of validity of the finite-Larmor-radius expansion and of the reduced kinetic descriptions for the beam ions in NSTX is discussed. The calculated kinetic equilibria can be used for self-consistent numerical studies of beam-ion-driven instabilities in NSTX.

E.V. Belova; N.N. Gorelenkov; C.Z. Cheng

2003-04-09

398

NASA Astrophysics Data System (ADS)

We are developing a video see-through head-mounted display (HMD) augmented reality (AR) system for image-guided neurosurgical planning and navigation. The surgeon wears a HMD that presents him with the augmented stereo view. The HMD is custom fitted with two miniature color video cameras that capture a stereo view of the real-world scene. We are concentrating specifically at this point on cranial neurosurgery, so the images will be of the patient's head. A third video camera, operating in the near infrared, is also attached to the HMD and is used for head tracking. The pose (i.e., position and orientation) of the HMD is used to determine where to overlay anatomic structures segmented from preoperative tomographic images (e.g., CT, MR) on the intraoperative video images. Two SGI 540 Visual Workstation computers process the three video streams and render the augmented stereo views for display on the HMD. The AR system operates in real time at 30 frames/sec with a temporal latency of about three frames (100 ms) and zero relative lag between the virtual objects and the real-world scene. For an initial evaluation of the system, we created AR images using a head phantom with actual internal anatomic structures (segmented from CT and MR scans of a patient) realistically positioned inside the phantom. When using shaded renderings, many users had difficulty appreciating overlaid brain structures as being inside the head. When using wire frames, and texture-mapped dot patterns, most users correctly visualized brain anatomy as being internal and could generally appreciate spatial relationships among various objects. The 3D perception of these structures is based on both stereoscopic depth cues and kinetic depth cues, with the user looking at the head phantom from varying positions. The perception of the augmented visualization is natural and convincing. The brain structures appear rigidly anchored in the head, manifesting little or no apparent swimming or jitter. The initial evaluation of the system is encouraging, and we believe that AR visualization might become an important tool for image-guided neurosurgical planning and navigation.

Maurer, Calvin R., Jr.; Sauer, Frank; Hu, Bo; Bascle, Benedicte; Geiger, Bernhard; Wenzel, Fabian; Recchi, Filippo; Rohlfing, Torsten; Brown, Christopher R.; Bakos, Robert J.; Maciunas, Robert J.; Bani-Hashemi, Ali R.

2001-05-01

399

Weakly Turbulent Magnetohydrodynamic Waves in Compressible Low-{beta} Plasmas

In this Letter, weak-turbulence theory is used to investigate interactions among Alfven waves and fast and slow magnetosonic waves in collisionless low-{beta} plasmas. The wave kinetic equations are derived from the equations of magnetohydrodynamics, and extra terms are then added to model collisionless damping. These equations are used to provide a quantitative description of a variety of nonlinear processes, including parallel and perpendicular energy cascade, energy transfer between wave types, 'phase mixing', and the generation of backscattered Alfven waves.

Chandran, Benjamin D. G. [Department of Physics, University of New Hampshire, Durham, New Hampshire 03824 (United States)

2008-12-05

400

A review is given of the fundamental aspects involved in material processing using thermal plasma technology. The description of plasma generating devices covers DC plasma torches, DC transferred arcs, RF inductively coupled plasma torches and hybrid combinations of them. Emphasis is given to the identification of the basic energy coupling mechanism in each case and the principal characteristics of the

Maher I. Boulos

1991-01-01

401

Ion temperature in plasmas with intrinsic Alfven waves

NASA Astrophysics Data System (ADS)

This Brief Communication clarifies the physics of non-resonant heating of protons by low-frequency Alfvenic turbulence. On the basis of general definition for wave energy density in plasmas, it is shown that the wave magnetic field energy is equivalent to the kinetic energy density of the ions, whose motion is induced by the wave magnetic field, thus providing a self-consistent description of the non-resonant heating by Alfvenic turbulence. Although the study is motivated by the research on the solar corona, the present discussion is only concerned with the plasma physics of the heating process.

Wu, C. S.; Yoon, P. H.; Wang, C. B.

2014-10-01

402

Ion temperature in plasmas with intrinsic Alfven waves

This Brief Communication clarifies the physics of non-resonant heating of protons by low-frequency Alfvenic turbulence. On the basis of general definition for wave energy density in plasmas, it is shown that the wave magnetic field energy is equivalent to the kinetic energy density of the ions, whose motion is induced by the wave magnetic field, thus providing a self-consistent description of the non-resonant heating by Alfvenic turbulence. Although the study is motivated by the research on the solar corona, the present discussion is only concerned with the plasma physics of the heating process.

Wu, C. S. [CAS Key Laboratory of Geospace Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei (China); Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); Yoon, P. H. [Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742 (United States); School of Space Research, Kyung Hee University, Yongin, Gyeonggi 446-701 (Korea, Republic of); Wang, C. B. [CAS Key Laboratory of Geospace Environment, School of Earth and Space Sciences, University of Science and Technology of China, Hefei (China)

2014-10-15

403

This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this project has been to develop a fundamental understanding of dusty plasmas at the Laboratory. While dusty plasmas are found in space in galactic clouds, planetary rings, and cometary tails, and as contaminants in plasma enhanced fabrication of microelectronics, many of their properties are only partially understood. Our work has involved both theoretical analysis and self-consistent plasma simulations to understand basic properties of dusty plasmas related to equilibrium, stability, and transport. Such an understanding can improve the control and elimination of plasma dust in industrial applications and may be important in the study of planetary rings and comet dust tails. We have applied our techniques to the study of charging, dynamics, and coagulation of contaminants in plasma processing reactors for industrial etching and deposition processes and to instabilities in planetary rings and other space plasma environments. The work performed in this project has application to plasma kinetics, transport, and other classical elementary processes in plasmas as well as to plasma waves, oscillations, and instabilities.

Jones, M.E.; Winske, D.; Keinigs, R.; Lemons, D.

1996-05-01

404

Antibiotic Attack (Kinetic City)

NSDL National Science Digital Library

This game is a part of the Tau Pack of the Kinetic City site (see description below). In this simulation, the patient's bodies are filled with bacteria. The object is to cure as many patients as possible. Learning concepts enforced here are that antibiotics are specific for the type of bacteria they treat, their strength, and that the bacteria may also become resistant to the bacteria by mutations.KINETIC CITY DESCRIPTION: "Kinetic City" (www.kineticcity.com) is a fun, Web-based after-school science club for kids, ages 8 through 11. It combines exciting online animations and activities with boxes of hands-on science experiments. Children earn "Kinetic City" power points and collect stickers as they complete missions and learn standards-based science content. Here's how it works: The "Kinetic City" super crew (Keisha, Curtis, Megan and Max) needs the help of Earth kids to save their planet Vearth, from the science-distorting computer virus Deep Delete. Each of Deep Delete's 60 hideous strains attacks a different area of science with disastrous consequences. After each attack, teams of Earth kids fight back by viewing a short online animation describing the situation on Vearth; performing a series of activities to re-learn the lost science and going on a mission to Vearth during which they answer science questions and gobble up Deep Delete viruses. Their scores appear on their own Kinetic City Club Web page. "Kinetic City" is produced by the American Association for the Advancement of Science (AAAS), with a grant from the National Science Foundation. AAAS writes the "Project 2061 Benchmarks for Science Literacy," which forms the basis of most state science standards.

American Association for the Advancement of Science (; )

2005-01-01

405

Kinetic Damping of Toroidal Alfven Eigenmodes

The damping of Toroidal Alfven Eigenmodes in JET plasmas is investigated by using a reduced kinetic model. Typically no significant damping is found to occur near the center of the plasma due to mode conversion to kinetic Alfven waves. In contrast, continuum damping from resonance near the plasma edge may be significant, and when it is, it gives rise to damping rates that are compatible with the experimental observations.

G.Y. Fu; H.L. Berk; A. Pletzer

2005-05-03

406

ERIC Educational Resources Information Center

Presents a unit on chemical reaction kinetics that consists of a predemonstration activity, the demonstration, and a set of postdemonstration activities that help students transfer the concepts to actual chemical reactions. Simulates various aspects of chemical reaction kinetics. (JRH)

Burgardt, Erik D.; Ryan, Hank

1996-01-01

407

ERIC Educational Resources Information Center

Surveys the research of scientists like Joule, Kelvin, Maxwell, Clausius, and Boltzmann as it comments on the basic conceptual issues involved in the development of a more precise kinetic theory and the idea of a kinetic atom. (Author/SK)

Wilson, David B.

1981-01-01

408

What constitutes a comprehensive description of drought, a description forming a basis for answering why a drought occurred is outlined. The description entails two aspects that are "naturally" coupled, named physical and economic, and treats the set of hydrologic measures of droughts in terms of their multivariate distribution, rather than in terms of a collection of the marginal distributions. ?? 1991 Springer-Verlag.

Matalas, N.C.

1991-01-01

409

ERIC Educational Resources Information Center

Conveys an appreciation of enzyme kinetic analysis by using a practical and intuitive approach. Discusses enzyme assays, kinetic models and rate laws, the kinetic constants (V, velocity, and Km, Michaels constant), evaluation of V and Km from experimental data, and enzyme inhibition. (CW)

Moe, Owen; Cornelius, Richard

1988-01-01

410

NASA Astrophysics Data System (ADS)

Much effort has been recently devoted to the experimental determination of absolute partial and total electron impact ionization cross sections of molecules and radicals due to the ever increasing importance of these cross sections in many applications such as low- and high-temperature plasma physics and chemistry, atmospheric physics and mass spectrometry. In addition supporting calculations have been recently developed in order to allow the analytic quantitative description of these cross section functions for modeling codes. This review summarizes recent experimental and theoretical progress in this area of electron impact ionization including also a short description of (i) recent advances in the field of electron/ion collisions (i.e., kinetic energy release distributions in dissociative excitation reactions of molecular ions) and (ii) a novel approach to the determination of electron induced appearance energies. .

Matt, S.; Fiegele, T.; Hanel, G.; Muigg, D.; Denifl, G.; Becker, K.; Deutsch, H.; Echt, O.; Mason, N.; Stamatovic, A.; Scheier, P.; Märk, T. D.

2000-11-01

411

NASA Astrophysics Data System (ADS)

Additions of the low occurrence stable isotopes 61Ni, 65Cu, and 68Zn were used as tracers to determine the exchange kinetics of metals between dissolved and particulate forms in laboratory studies of natural water and suspended sediments from South San Francisco Bay, CA. Dissolved metal isotope additions were made so that the isotope ratios (rather than total metal partitioning) were significantly altered from initial ambient conditions. Dissolved metal concentrations were determined using an organic ligand sequential extraction technique followed by analysis with high-resolution inductively coupled plasma mass spectrometry (HR-ICPMS). Exchangeable particulate concentrations were extracted using a 20% acetic acid leach followed by determination using HR-ICPMS. Equilibrium and kinetic sorption parameters were quantified according to a general model for trace metal partitioning assuming pseudo-first-order kinetics. Partition coefficients (K D) were tracked as a function of time over the fortnight experiment. For Ni, Cu, and Zn the initial ambient K D values were found to be 10 3.65, 10 3.88, and 10 4.52 L kg -1, respectively. As a result of the dissolved metal isotope additions, the partition coefficients for all three metals dropped and then increased back to near ambient K D values after 14 days. Curve-fitting concentration versus time profiles from both dissolved and exchangeable particulate data sets allowed determination of kinetic rate constants. The best estimates of forward and backward kinetic rate constants for Ni, Cu, and Zn respectively are k' f = 0.03, 0.07, 0.12 d -1 and k b = 0.13, 0.12, 0.15 d -1. These results predict that sorption equilibria in South Bay should be reached on the order of a month for Ni, on the order of 3 weeks for Cu, and on the order of 2 weeks for Zn. Together, the dissolved and exchangeable particulate data indicate more sluggish sorption kinetics for Ni than for Cu and Zn and suggest that different chemical forms control the speciation of these three metals in South Bay. Order of magnitude metal sorption exchange rates were estimated using these kinetic results. These calculations indicate that sorption exchange between dissolved and suspended particulate phases can cause dynamic internal cycling of these metals in South San Francisco Bay.

Gee, Alison K.; Bruland, Kenneth W.

2002-09-01

412

Hybrid MHD-kinetic electron simulations of global standing modes (Invited)

NASA Astrophysics Data System (ADS)

Geomagnetic Field Line Resonances (FLRs) are an example of large scale global structures that can directly couple energy from large perpendicular scale lengths to small scale kinetic Alfven wave (KAW) and inertial Alfven wave (IAW) scale lengths and ultimately in to the acceleration of particles to carry the field aligned currents. In this presentation, we will summarize the methodology and results of a hybrid MHD-kinetic electron model of FLRs which self consistently couples the cold plasma MHD equations to a system of kinetic guiding center electrons in a dipolar geometry. Results will highlight the cascade of energy evident in these simulations from large to small scale and will demonstrate that the deposition of this wave energy into electron acceleration is a significant sink of wave energy. The calculated wave spectra evident in this cascade will also be compared with observations and advances to the model using a gyrokinetic description of ion dynamics will be discussed.

Damiano, P. A.; Johnson, J.; Kim, E.

2010-12-01

413

A kinetic model of the plasma-etching process has been developed to describe the etching of Si and SiO/sub 2/ in C/sub n/F/sub m//O/sub 2/ and C/sub n/F/sub m//H/sub 2/ plasmas (C/sub n/F/sub m/ equivalentCF/sub 4/, C/sub 2/F/sub 6/). The model has obtained good agreement with experiment for demonstrating the selective etching of SiO/sub 2/ in C/sub n/F/sub m//H/sub 2/ plasmas, and the enhancement of the etch rate of Si in C/sub n/F/sub m//O/sub 2/ plasmas. Good agreement is also obtained with mass spectroscopic measurements of neutral species from a CF/sub 4//H/sub 2/ plasma. Results from the model indicate that the adsorption of atomic hydrogen on silicon surfaces from C/sub n/F/sub m//H/sub 2/ plasmas, which then reacts with adsorbed fluorine, can significantly effect the selectivity of etching SiO/sub 2/ with respect to Si. Similarly, the adsorption of atomic oxygen, which then reacts with adsorbed carbon thereby cleansing the surface, may be responsible for the large etch rates of Si seen in C/sub n/F/sub m//O/sub 2/ plasmas. The selectivity of etching SiO/sub 2/ in C/sub n/F/sub m//H/sub 2/ plasmas has been found to be a sensitive function of the C/F ratio of the carbon-bearing molecules which desorb from the surface, and a C/F ratio of 0.5 shows best agreement with experiment. Results from the model favor ion drift as a dominant mechanism by which radicals are transported to the surface.

Kushner, M.J.

1982-04-01

414