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1

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

E-print Network

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  

SciTech Connect

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

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

2012-11-15

3

On kinetic description of electromagnetic processes in a quantum plasma  

SciTech Connect

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

Tyshetskiy, Yu.; Vladimirov, S. V.; Kompaneets, R. [School of Physics, University of Sydney, New South Wales 2006 (Australia)

2011-11-15

4

Kinetic description of rotating Tokamak plasmas with anisotropic temperatures in the collisionless regime  

NASA Astrophysics Data System (ADS)

A largely unsolved theoretical issue in controlled fusion research is the consistent kinetic treatment of slowly-time varying plasma states occurring in collisionless and magnetized axisymmetric plasmas. The phenomenology may include finite pressure anisotropies as well as strong toroidal and poloidal differential rotation, characteristic of Tokamak plasmas. Despite the fact that physical phenomena occurring in fusion plasmas depend fundamentally on the microscopic particle phase-space dynamics, their consistent kinetic treatment remains still essentially unchallenged to date. The goal of this paper is to address the problem within the framework of Vlasov-Maxwell description. The gyrokinetic treatment of charged particles dynamics is adopted for the construction of asymptotic solutions for the quasi-stationary species kinetic distribution functions. These are expressed in terms of the particle exact and adiabatic invariants. The theory relies on a perturbative approach, which permits to construct asymptotic analytical solutions of the Vlasov-Maxwell system. In this way, both diamagnetic and energy corrections are included consistently into the theory. In particular, by imposing suitable kinetic constraints, the existence of generalized bi-Maxwellian asymptotic kinetic equilibria is pointed out. The theory applies for toroidal rotation velocity of the order of the ion thermal speed. These solutions satisfy identically also the constraints imposed by the Maxwell equations, i.e., quasi-neutrality and Ampere's law. As a result, it is shown that, in the presence of nonuniform fluid and EM fields, these kinetic equilibria can sustain simultaneously toroidal differential rotation, quasi-stationary finite poloidal flows and temperature anisotropy.

Cremaschini, Claudio; Tessarotto, Massimo

2011-11-01

5

On description of quantum plasma  

E-print Network

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

2011-01-20

6

Fluid and drift-kinetic description of a magnetized plasma with low collisionality and slow dynamics orderings. I. Electron theory  

SciTech Connect

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

7

Kinetic description of avalanching systems.  

PubMed

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

8

Photon kinetic description of 1D relativistic EM pulse solitons  

Microsoft Academic Search

Photon kinetics provides a novel formalism to describe intense EM fields-plasma interactions, where the EM fields are described as a collection of quasi-particles (photons). Photon kinetics provides a better physical picture of the EM fields dynamics, is computionally less demanding, and allows for an easy description of broadband incoherent light pulses. We have developed a 1D photon kinetic code, where

R. Trines; R. Bingham; W. B. Mori; L. O. Silva

2003-01-01

9

Vibrational kinetics of diatomic molecules in parallel plate RF plasmas  

Microsoft Academic Search

In this paper, the history and state of the art of the theoretical modeling of the vibrational kinetics of diatomic molecules in nonequilibrium plasmas produced by parallel plate, capacitively coupled radio-frequency (RF) discharges are conceptually discussed. After introducing the physical framework and classical methods for the vibrational kinetics description in plasmas, the peculiarity and novelty of parallel plate RF discharges

S. Longo; P. Diomede; M. Capitelli

2008-01-01

10

Wave-particle-interaction in kinetic plasmas  

NASA Astrophysics Data System (ADS)

Resonant scattering of energetic protons off magnetic irregularities is the main process in cosmic ray diffusion. The typical theoretical description uses Alfvén waves in the low frequency limit. We demonstrate that the usage of Particle-in-Cell (PiC) simulations for particle scattering is feasible. The simulation of plasma waves is performed with the relativistic electromagnetic PiC code ACRONYM and the tracks of test particles are evaluated in order to study particle diffusion. Results for the low frequency limit are equivalent to those obtained with an MHD description, but only for high frequencies results can be obtained with reasonable effort. PiC codes have the potential to be a useful tool to study particle diffusion in kinetic turbulence.

Schreiner, Cedric; Spanier, Felix

2014-07-01

11

Photon kinetics for laser-plasma interactions  

Microsoft Academic Search

A photon kinetic formalism is employed to describe the propagation of short laser pulses in tenuous plasmas. The photon kinetic theory contains all of the ingredients necessary to describe the relativistic nonlinear optics of short laser pulses in plasmas, and the shortest time scale is determined by the local evolution of the index of refraction. We use this feature to

L. O. Silva; W. B. Mori; R. Bingham; J. M. Dawson; Thomas M. Antonsen; P. Mora

2000-01-01

12

Kinetic equation for spin-polarized plasmas  

SciTech Connect

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

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

1984-07-01

13

Computer models for kinetic equations of magnetically confined plasmas  

SciTech Connect

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

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

1987-01-01

14

Plasma kinetics in molecular plasmas and modeling of reentry plasmas  

NASA Astrophysics Data System (ADS)

State-to-state non-equilibrium plasma kinetics is widely used to characterize cold molecular and reentry plasmas. The approach requires a high level of dynamical information, and demands a large effort in the creation of complete databases of state-resolved cross sections and rate coefficients. Recent results, emphasizing the dependence of elementary process probability on both the vibrational and rotational energy content of the H2 molecule, are presented for those channels governing the microscopic collisional dynamics in non-equilibrium plasmas, i.e. electron-impact induced resonant processes, vibrational deactivation and dissociation in atom-diatom collisions and atomic recombination at the surface. Results for H2 plasmas, i.e. negative ion sources for neutral beam injection in fusion reactors, RF parallel-plate reactors for microelectronics, atmospheric discharges and the shock wave formed in the hypersonic entry of vehicles in planetary atmosphere for aerothermodynamics, are discussed.

Capitelli, M.; Celiberto, R.; Colonna, G.; D'Ammando, G.; De Pascale, O.; Diomede, P.; Esposito, F.; Gorse, C.; Laricchiuta, A.; Longo, S.; Pietanza, L. D.; Taccogna, F.

2011-12-01

15

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

16

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.

17

Kinetic description of quantum Brownian motion  

E-print Network

We stress the relevance of the two features of translational invariance and atomic nature of the gas in the quantum description of the motion of a massive test particle in a gas, corresponding to the original picture of Einstein used in the characterization of Brownian motion. The master equation describing the reduced dynamics of the test particle is of Lindblad form and complies with the requirement of covariance under translations.

Bassano Vacchini; Francesco Petruccione

2008-09-03

18

Hamiltonian kinetic theory of plasma ponderomotive processes  

SciTech Connect

The nonlinear nonresonant interaction of plasma waves and particles is formulated in a Hamiltonian kinetic theory which treats the wave-action and particle distributions on an equal footing, thereby displaying reciprocity relations. In the quasistatic limit, a nonlinear wave-kinetic equation is obtained. The generality of the formalism allows for applications to arbitrary geometry, with the nonlinear effects expressed in terms of the linear susceptibility.

McDonald, S.W.; Kaufman, A.N.

1981-12-01

19

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

Microsoft Academic Search

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

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

2006-01-01

20

Kinetic Simulation of Recombining Divertor Plasmas  

NASA Astrophysics Data System (ADS)

Fokker-Planck code ALLA can simulate coupled plasma (electrons and ions) and neutral atoms dynamics in the 1D2V approximation by taking into account non-linear Coulomb, and other elastic and inelastic binary collisions [1]. We discuss addition of 3-body recombination process, which is thought to be important for the deeply detached scrape-off layer plasmas. We present first kinetic model of recombining plasma in the tokamak divertor. We discuss observed kinetic phenomena, in particular, effect of non-Maxwellian electron distributions on the effective 3-b volume recombination rate for the realistic conditions of the divertor of Alcator C-Mod and other machines. [1] O.Batishchev, Proc. 16th Int. Conf. Num. Sim. Plasmas, Santa Barbara 155 (1998).

Batishcheva, A. A.; Batishchev, O. V.

1998-11-01

21

Inertial range turbulence in kinetic plasmas  

E-print Network

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

22

Kinetic Approach for Laser-Induced Plasmas  

SciTech Connect

Non-equilibrium distribution functions of electron gas and phonon gas excited with ultrashort intense laser pulses are calculated for laser-induced plasmas occurring in solids. The excitation during femtosecond irradiation and the subsequent thermalization of the free electrons, as well as the dynamics of phonons are described by kinetic equations. The microscopic collision processes, such as absorption by inverse bremsstrahlung, electron-electron collisions, and electron-phonon interactions are considered by complete Boltzmann collision integrals. We apply our kinetic approach for gold by taking s-band electron into account and compare it with the case of excitation of d-band electrons.

Omar, Banaz; Rethfeld, Baerbel [Technical University of Kaiserslautern, Department of Physics, Erwin Schroedinger Str. 46, D-67663 Kaiserslautern (Germany)

2008-10-22

23

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

24

On electromagnetic ballooning modes in fluid and kinetic descriptions  

SciTech Connect

A comparison between two-fluid, gyrofluid, and gyrokinetic descriptions of the collisionless ballooning mode in the toroidal limit is performed. The two-fluid model [A. Jarmen {ital et} {ital al}., Nucl. Fusion {bold 27}, 941 (1987)] is reactive and expanded in the finite-Larmor radius (FLR), in contrast to the gyrofluid model [R. E. Waltz {ital et} {ital al}., Phys. Fluids B {bold 4}, 3138 (1992)], which is dissipative and includes finite-Larmor-radius effects to all orders. The eigenmode differential equation is derived and solved numerically. It is shown that the fluid models are able to reproduce the gyrokinetic result, at least qualitatively. The role of the ion magnetic drift resonance and the ion FLR terms, in the fluid and kinetic descriptions, is discussed. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Froejdh, M.; Nordman, H.; Jhowry, B. [Institute for Electromagnetic Field Theory and EURATOM/NFR Association, Chalmers University of Technology, S-412 96 Goeteborg (Sweden)] [Institute for Electromagnetic Field Theory and EURATOM/NFR Association, Chalmers University of Technology, S-412 96 Goeteborg (Sweden)

1995-11-01

25

Fundamental Statistical Descriptions of Plasma Turbulence in Magnetic Fields  

SciTech Connect

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

John A. Krommes

2001-02-16

26

A kinetic description of electron beam ejection from spacecraft  

NASA Astrophysics Data System (ADS)

A model based on the Boltzmann kinetic equation describing electron beam ejection from spacecraft is presented. Results are shown for steady-state, beam-atmosphere interaction (BAI) and for beam-plasma interaction (BPI). The BPI considered is that of elastic scattering of beam electrons with strong, short-scale Langmuir turbulence. This mechanism has been suggested for prompt echoes of beam electrons observed in sounding rocket experiments. It is shown that the interaction is sufficiently strong to account for observations of back-scattered electrons at the beam accelerator energy. However, it is clear from observations that particles undergo diffusion in energy at a rate exceeding levels expected for BAI. Inelastic scattering in BPI must therefore also be important.

Khazanov, George V.; Neubert, Torsten; Gefan, Grigorii D.; Trukhan, Aleksander A.; Mishin, Evgeni V.

1993-09-01

27

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

SciTech Connect

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

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

2008-06-15

28

Fully implicit kinetic modelling of collisional plasmas  

SciTech Connect

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

Mousseau, V.A.

1996-05-01

29

Kinetic plasma modeling with quiet Monte Carlo direct simulation.  

SciTech Connect

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

30

Original article Compared kinetics of plasma creatine kinase activity  

E-print Network

Original article Compared kinetics of plasma creatine kinase activity in rabbits after intravenous 1993) Summary ― The purpose of this study was to compare the disposition parameters of creatine muscle damage. creatine kinase / kinetics / muscle damage / rabbit Résumé ― Cinétiques comparées

Boyer, Edmond

31

Plasma Kinetics in the Ethanol/Water/Air Mixture in "Tornado" Type Electrical Discharge  

E-print Network

This paper presents the results of a theoretical and experimental study of plasma-assisted reforming of ethanol into molecular hydrogen in a new modification of the "tornado" type electrical discharge. Numerical modeling clarifies the nature of the non-thermal conversion and explains the kinetic mechanism of nonequilibrium plasma-chemical transformations in the gas-liquid system and the evolution of hydrogen during the reforming as a function of discharge parameters and ethanol-to-water ratio in the mixture. We also propose a scheme of chemical reactions for plasma kinetics description. It is shown that some characteristics of the investigated reactor are at least not inferior to characteristics of other plasma chemical reactors.

Levko, D; Chernyak, V; Olszewski, S; Nedybaliuk, O

2011-01-01

32

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

33

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

34

Kinetic Theory of Plasma Sheaths Surrounding Electron-Emitting Surfaces  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

35

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

36

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

SciTech Connect

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

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

2012-08-29

37

Application of Nonlocalpp Electron Kinetics to Plasma  

E-print Network

Interest "Interest. · Report on Scientific Directions for Low Temperature Plasma sponsored by Department not captured in fluid models: · Explosive generation of cold electrons with power increase.Explosive generation and dc discharges for plasma processing and electric propulsion. 3 p p #12;Nonlocality is not just

Kaganovich, Igor

38

Photon Kinetic Theory and Simulations of Laser-Plasma Interactions  

Microsoft Academic Search

The propagation of electromagnetic waves in underdense plasmas can be described by a Vlasov-like transport equation for the Wigner distribution function of the e.m.field. We determine the temporal growth rates for Raman Scattering for all angles from the photon kinetic theory, and compare them with the standard growth rates, thus establishing the limits of validity of the theory. The kinetic

L. O. Silva; W. B. Mori; R. Bingham; J. M. Dawson; C. Ren; F. S. Tsung; T. M. Antonsen Jr.; P. Mora

1999-01-01

39

Fully kinetic simulations of megajoule-scale dense plasma focus  

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. Megajoule-scale DPFs can generate 1012 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.; Welch, D.; Meehan, B. T.; Tang, V.; Halvorson, C.; May, M.; Hagen, E. C.

2014-10-01

40

Dynamic and kinetic plasma processes at Saturn  

NASA Astrophysics Data System (ADS)

At Saturn is a complex, dynamic system where plasma processes are governed by the interactions between plasmas and the moons and neutral cloud that orbit the planet. Each of those bodies has a different interaction with their surroundings and affects the system in different ways. We study these interactions using data from the Cassini magnetometer. In this thesis, we examine these interactions in order to learn about both the bodies and the plasma with which they interact. Two of Saturn's icy moons on which we focus are Enceladus and Iapetus. The first orbits at a distance of 3.95 Saturn radii (R S ) and is in the densest part of the neutral cloud; the second is 60 R S from the planet and spends much of its orbit outside of the magnetosphere. The plume at Enceladus' southern pole is known to be a major source of neutral cloud orbiting Saturn and modeling suggests that lapetus may also be a neutral source. The plasma environments of these two moons are very different, so we use different approach es to study them. For Iapetus, we use magnetometer and plasma wave observations made during Cassini's single close flyby, made when the moon was in the solar wind. Both instruments find perturbations that do not resemble solar wind structures but are well-correlated with the moon. After examining the possibilities, we conclude that Iapetus is not a significant source of neutrals. To perturb the solar wind as observed, we believe that the most geophysically-probable conclusion is a conducting layer, such as an ocean, beneath the moon's surface. At Enceladus, we examine the moon's control of the neutral cloud structure and its effect on the magnetospheric plasma. To probe variation in the neutral cloud, we use ion cyclotron waves as a diagnostic of the local neutral density. We find that Enceladus strongly controls the cloud's azimuthal structure between 3.7 and 4.5 R S . To study the moon's effect on the plasma, we use downstream observations of the moon's wake. The interaction between Enceladus' plume and the magnetospheric plasma slows the bulk plasma flow and causes a perturbation in the magnetic field. This perturbation convects downstream to where Cassini observes it. We find that Enceladus' wake persists until at least 120 degrees downstream and the magnetic perturbation is strong enough to produce significant energy deposition into the ionosphere. We discuss these conclusions with respect to the null observation of auroral emissions associated with the moon.

Leisner, Jared Scott

41

Hamiltonian field description of two-dimensional vortex fluids and guiding center plasmas  

SciTech Connect

The equations that describe the motion of two-dimensional vortex fluids and guiding center plasmas are shown to possess underlying field Hamiltonian structure. A Poisson bracket which is given in terms of the vorticity, the physical although noncanonical dynamical variable, casts these equations into Heisenberg form. The Hamiltonian density is the kinetic energy density of the fluid. The well-known conserved quantities are seen to be in involution with respect to this Poisson bracket. Expanding the vorticity in terms of a Fourier-Dirac series transforms the field description given here into the usual canonical equations for discrete vortex motion. A Clebsch potential representation of the vorticity transforms the noncanonical field description into a canonical description.

Morrison, P.J.

1981-03-01

42

Kinetics of complex plasma with liquid droplets  

SciTech Connect

This paper provides a theoretical basis for the reduction of electron density by spray of water (or other liquids) in hot plasma. This phenomenon has been observed in a hypersonic flight experiment for relief of radio black out, caused by high ionization in the plasma sheath of a hypersonic vehicle, re-entering the atmosphere. The analysis incorporates a rather little known phenomenon for de-charging of the droplets, viz., evaporation of ions from the surface and includes the charge balance on the droplets and number cum energy balance of electrons, ions, and neutral molecules; the energy balance of the evaporating droplets has also been taken into account. The analysis has been applied to a realistic situation and the transient variations of the charge and radius of water droplets, and other plasma parameters have been obtained and discussed. The analysis through made in the context of water droplets is applicable to all liquids.

Misra, Shikha; 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); Mishra, S. K. [Institute for Plasma Research (IPR), Gandhinagar 382428 (India)] [Institute for Plasma Research (IPR), Gandhinagar 382428 (India)

2013-12-15

43

Decharging of complex plasmas: first kinetic observations.  

PubMed

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

44

PHYSICS 783 Plasma Kinetic Theory CLASS DETAILS  

E-print Network

says ­ PHYS 481 (Intro Plasma) & PHYS 631 (Graduate Classical Mechanics) & PHYS 634 (Graduate the industry standard) · Handouts will be provided as necessary. · Printed notes corresponding to the lecture not expect that attendance is sufficient or lectures are complete. Important topics will be left out

Cassak, Paul

45

Gas Kinetic Study of Magnetic Field Effects on Plasma Plumes  

E-print Network

continuum-based description and computation valid; ii) in the context of MHD framework, the generalized Ohm’s law must be used to capture all of the relevant physics. This work also continues the development of the Magneto Gas Kinetic Method (MGKM...

Ebersohn, Frans 1987-

2012-12-07

46

PLASMAKIN: A chemical kinetics library for plasma physics modeling  

Microsoft Academic Search

PLASMAKIN is a package to handle physical and chemical data used in plasma physics modeling and to compute kinetics data from the reactions taking place in the gas or at the surfaces: particle production and loss rates, photon spectra and energy exchange rates. It has no limits on the number of species and reactions that can be handled, is independent

Nuno Pinhao

2007-01-01

47

Emergence of Kinetic Behavior in Streaming Ultracold Neutral Plasmas  

E-print Network

We create streaming ultracold neutral plasmas by tailoring the photoionizing laser beam that creates the plasma. By varying the electron temperature, we control the relative velocity of the streaming populations, and, in conjunction with variation of the plasma density, this controls the ion collisionality of the colliding streams. Laser-induced fluorescence is used to map the spatially resolved density and velocity distribution function for the ions. We identify the lack of local thermal equilibrium and distinct populations of interpenetrating, counter-streaming ions as signatures of kinetic behavior. Experimental data is compared with results from a one-dimensional, two-fluid numerical simulation.

McQuillen, P; Bradshaw, S; Killian, T C

2014-01-01

48

Kinetic theory of nonlinear transport phenomena in complex plasmas  

SciTech Connect

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

49

Complexity reduction of collisional-radiative kinetics for atomic plasma  

SciTech Connect

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

50

Toward a Fully Kinetic Theory of Turbulence in Magnetized Plasmas  

SciTech Connect

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

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

2010-12-30

51

Hamiltonian and Lagrangian approaches to hybrid kinetic-fluid plasmas  

NASA Astrophysics Data System (ADS)

The development of multiscale multiphysics models is required in different contexts of plasma physics, from fusion theory to space plasmas. Indeed, plasmas are often found to consist of two different species: a cold (fluid) species and a hot (kinetic) component. Several modeling efforts over the last two decades culminated in the formulation of two main types of hybrid kinetic-fluid models: current-coupling schemes (CCS') and pressure-coupling schemes (PCS'). Although CCS' conserve energy exactly, PCS' (used in simulations) require certain approximations that break exact energy conservation. In this work, we formulate new PCS models, whose exact energy conservation is guaranteed by an appropriate Hamiltonian (and Lagrangian) structure. A comparison of Hamiltonian and non-Hamiltonian models is then presented, in terms of linear and non-linear stability.

Tronci, Cesare; Morrison, P. J.; Tassi, Emanuele

2012-10-01

52

Preliminary scaling laws for plasma current, ion kinetic temperature, and plasma number density in the NASA Lewis bumpy torus plasma  

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

53

ASCOT: Solving the kinetic equation of minority particle species in tokamak plasmas  

NASA Astrophysics Data System (ADS)

A comprehensive description of methods, suitable for solving the kinetic equation for fast ions and impurity species in tokamak plasmas using a Monte Carlo approach, is presented. The described methods include Hamiltonian orbit-following in particle and guiding center phase space, test particle or guiding center solution of the kinetic equation applying stochastic differential equations in the presence of Coulomb collisions, neoclassical tearing modes and Alfvén eigenmodes as electromagnetic perturbations relevant to fast ions, together with plasma flow and atomic reactions relevant to impurity studies. Applying the methods, a complete reimplementation of the well-established minority species code ASCOT is carried out as a response both to the increase in computing power during the last twenty years and to the weakly structured growth of the code, which has made implementation of additional models impractical. Also, a benchmark between the previous code and the reimplementation is accomplished, showing good agreement between the codes.

Hirvijoki, E.; Asunta, O.; Koskela, T.; Kurki-Suonio, T.; Miettunen, J.; Sipilä, S.; Snicker, A.; Äkäslompolo, S.

2014-04-01

54

Non Equilbrium Vibrational Kinetics in Expanding Plasma Flows  

SciTech Connect

The supersonic expansion of a plasma is a system of interest for aerospace applications, ranging from propulsion to hypersonic wind tunnels. Under these conditions the plasma shows significant departures from chemical and thermal equilibrium, similarly to post-discharge conditions. The multitemperature description is not adequate because the internal level distributions show tails overpopulated with respect to a Boltzmann distribution. The state-to-state approach has to be used, including the interaction with free electrons which follow non-maxwellian distributions.

Colonna, Gianpiero [CNR-IMIP, sede di Bari, Via Amendola 122/D, 70126, Bari (Italy)

2008-12-31

55

Kinetic Description of a Finite Temperature Meson Gas  

E-print Network

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

56

Kinetic models for the VASIMR thruster helicon plasma source  

NASA Astrophysics Data System (ADS)

Helicon gas discharge [1] is widely used by industry because of its remarkable efficiency [2]. High energy and fuel efficiencies make it very attractive for space electrical propulsion applications. For example, helicon plasma source is used in the high specific impulse VASIMR [3] plasma thruster, including experimental prototypes VX-3 and upgraded VX-10 [4] configurations, which operate with hydrogen (deuterium) and helium plasmas. We have developed a set of models for the VASIMR helicon discharge. Firstly, we use zero-dimensional energy and mass balance equations to characterize partially ionized gas condition/composition. Next, we couple it to one-dimensional hybrid model [6] for gas flow in the quartz tube of the helicon. We compare hybrid model results to a purely kinetic simulation of propellant flow in gas feed + helicon source subsystem. Some of the experimental data [3-4] are explained. Lastly, we discuss full-scale kinetic modeling of coupled gas and plasmas [5-6] in the helicon discharge. [1] M.A.Lieberman, A.J.Lihtenberg, 'Principles of ..', Wiley, 1994; [2] F.F.Chen, Plas. Phys. Contr. Fus. 33, 339, 1991; [3] F.Chang-Diaz et al, Bull. APS 45 (7) 129, 2000; [4] J.Squire et al., Bull. APS 45 (7) 130, 2000; [5] O.Batishchev et al, J. Plasma Phys. 61, part II, 347, 1999; [6] O.Batishchev, K.Molvig, AIAA technical paper 2000-3754, -14p, 2001.

Batishchev, Oleg; Molvig, Kim

2001-10-01

57

Kinetic ballooning/interchange instability in a bent plasma sheet  

NASA Astrophysics Data System (ADS)

We use Time History of Events and Macroscale Interactions during Substorms (THEMIS) and GOES observations to investigate the plasma sheet evolution on 28 February 2008 between 6:50 and 7:50 UT, when there developed strong magnetic field oscillations with periods of 100 s. Using multispacecraft analysis of the plasma sheet observations and an empirical plasma sheet model, we determine both the large-scale evolution of the plasma sheet and the properties of the oscillations. We found that the oscillations exhibited signatures of kinetic ballooning/interchange instability fingers that developed in a bent current sheet. The interchange oscillations had a sausage structure, propagated duskward at a velocity of about 100 km/s, and were associated with fast radial electron flows. We suggest that the observed negative gradient of the ZGSM magnetic field component (?BZ/?X) was a free energy source for the kinetic ballooning/interchange instability. Tens of minutes later a fast elongation of ballooning/interchange fingers was detected between 6 and 16 RE downtail with the length-to-width ratio exceeding 20. The finger elongation ended with signatures of reconnection in an embedded current sheet near the bending point. These observations suggest a complex interplay between the midtail and near-Earth plasma sheet dynamics, involving localized fluctuations in both cross-tail and radial directions before current sheet reconnection.

Panov, E. V.; Nakamura, R.; Baumjohann, W.; Kubyshkina, M. G.; Artemyev, A. V.; Sergeev, V. A.; Petrukovich, A. A.; Angelopoulos, V.; Glassmeier, K.-H.; McFadden, J. P.; Larson, D.

2012-06-01

58

Kinetic Ballooning/Interchange Instability in a Bent Plasma Sheet  

NASA Astrophysics Data System (ADS)

We use THEMIS and GOES observations to investigate the plasma sheet evolution on 28 February 2008 between 6:50 and 7:50 UT, when there developed strong magnetic field oscillations with period of 100 s. Using multi-spacecraft analysis of the plasma sheet observations and an empirical plasma sheet model, we determine both the large-scale evolution of the plasma sheet and the properties of the oscillations. We found that the oscillations exhibited signatures of kinetic ballooning/interchange instability fingers that developed in a bent current sheet. The interchange oscillations had a sausage structure, propagated duskward at a velocity of about 100 km/s, and were associated with periodical radial electron flows. We suggest that the observed negative gradient of the ZGSM magnetic field component (dBZ/dX) was a free energy source for the kinetic ballooning/interchange instability. Tens of minutes later a fast elongation of ballooning/interchange fingers was detected between 6 and 16 RE downtail with the legnth-to-width ratio exceeding 20. The finger elongation ended with signatures of reconnection in an embedded current sheet near the bending point. These observations suggest a complex interplay between the midtail and near-Earth plasma sheet dynamics, involving localized fluctuations both in cross-tail and radial directions before current sheet reconnection.

Panov, E. V.; Nakamura, R.; Baumjohann, W.; Kubyshkina, M. G.; Artemyev, A. V.; Sergeev, V. A.; Petrukovich, A. A.; Angelopoulos, V.; Glassmeier, K.-H.; McFadden, J. P.; Larson, D.

2012-04-01

59

Weakly Ionized Plasmas in Hypersonics: Fundamental Kinetics and Flight Applications  

SciTech Connect

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

Macheret, Sergey [Department of Mechanical and Aerospace Engineering, Princeton University, D-418 Engineering Quadrangle, Princeton, NJ 08544 (United States)

2005-05-16

60

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

61

STUDENT AWARD FINALIST: A Kinetic Theory of Planar Plasma Sheaths Surrounding Electron Emitting Surfaces  

NASA Astrophysics Data System (ADS)

It has long been known that electron emission from a surface significantly affects the sheath at that surface. Typical fluid theory of a planar sheath with emitted electrons assumes that the plasma electrons follow the Boltzmann relation and the emitted electrons are emitted with zero energy and predicts a potential drop of 1.03Te across the sheath at a floating boundary. By removing the assumption that all plasma electrons entering the sheath are reflected back into the bulk plasma (i.e. the Boltzmann relation) and considering electrons lost to the wall, we find that the predicted sheath potential is reduced to 0.91Te. Using a kinetic description of the emitted electrons, assuming a half Maxwellian distribution with temperature Tee, greatly affects the sheath potential. We show that kinetic theory predicts that the sheath potential significantly depends on the plasma to emitted electron temperature ratio. For example, we predict that an emissive probe (Tee= 0.2 eV) in a plasma with Te= 1eV will have a sheath potential of 0.51Te. Additionally, it is noted that the electron velocity distribution function in the sheath is unstable to the two-stream instability.

Sheehan, J. P.; Kaganovich, Igor; Hershkowitz, Noah; Raitses, Yevgeny

2012-10-01

62

Merging for Complex Particle Kinetic modeling of multiple plasma beams (inter-penetrating flows)  

NASA Astrophysics Data System (ADS)

We suggest a merging procedure for the Complex Particle Kinetic (CPK) model in case of inter-penetrating flow (multiple plasma beams). Each CPK macro-particle includes a Maxwellian distribution in velocity and Gaussian distribution in space with internal dynamics (see [Hewett, 2003], for details). It is assumed that an arbitrary distribution of real particles can be represented by such a superposition in phase space (moving--finite----element approach) at least as well as could be done with the standard particle in cell (PIC)/Monte Carlo (MC) delta functions and their associated ``shape factors". The CPK method allows us to provide a global simulation of the complex plasma objects on the Hall-MHD (fluid) scale (aggressive merging) with automatic incorporation of the kinetic/particle description of the particle-wave processes (aggressive fragmentation) where it is necessary. The CPK approximation works well for ions, electrons, dust grains and neutral components. This code was tested in the simulations for the study of the interaction of the plasma flow with comets and Io's atmosphere. In this report we examine the standard (PIC) and the CPK methods in the case of the particle acceleration by shock surfing. The plasma dynamics is described by a standard (particle-ion-- fluid- electron) hybrid model. While a particle-mesh method is well enough verified approach, the CPK model seems to be a good approach in case of multiscale simulation which includes multiple subdomains with various particle/fluid plasma behavior.

Lipatov, Alexander

2008-03-01

63

Transition of electron kinetics in weakly magnetized inductively coupled plasmas  

SciTech Connect

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

64

On bias of kinetic temperature measurements in complex plasmas  

NASA Astrophysics Data System (ADS)

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.; Moseev, D.; Salewski, M.

2014-02-01

65

Kinetic modeling of the Saturn ring-ionosphere plasma environment  

NASA Technical Reports Server (NTRS)

A time-independent kinetic plasma model was developed on the basis of the Li et al. (1988) semikinetic plasma model and was used to study the interaction of the Saturnian ionosphere and ring plasma. The model includes the gravitational magnetic mirror and centripetal and ambipolar electric forces, and the effect of the mixing of two plasma populations. The results obtained indicate that the density, temperature, and composition of plasma near the rings changing in the direction from the inner C ring to the outer A ring, due to the fact that the predominant source of plasma changes from the ionosphere to the rings. The model results also suggest that the outflow of hydrogen from the ionosphere to the rings may be shut off for field lines passing through the outer B and A ring, due to the ambipolar electric field set up by the warm ring plasma trapped near the ring plane by the centipetal force. In these regions, there will be a net flux of O(+) ions from the rings to the ionosphere.

Wilson, G. R.; Waite, J. H., Jr.

1989-01-01

66

Mixed particle-grid method for kinetic simulation of plasmas  

NASA Astrophysics Data System (ADS)

Latest development of a hybrid PIC-Vlasov method [1] for the kinetic modeling of collisionless plasmas is presented. Such plasma system is described by Poisson equation for self-consistent electric potential, and by set of Vlasov equations for electron and ionic plasma species. Traditional approach uses either PIC or Vlasov method. PIC suffers from high statistical noise, while Vlasov shows high numerical diffusion. New hybrid method combines best features of the two methods, while suppressing both numerical noise and diffusion. A comparison of various methods will be given for a few model problems raging from beam-plasma system [2] to plasma-wall interaction. First results of coupling new particle-mesh method with adaptive RRC method, which utilizes adaptive grid refinement and coarsening will be reported. [1] O.Batishchev , Proc. 17th Int. Conf. on Num. Sim. of Plasmas, Banff, Canada, May 2000, p.24; [2] O.Batishchev et al., Bull. Aps 45 (7) DPP/ICPP 2000 Meeting, Quebec City, Canada, Bull. APS 45 (7) 72, 2000; [3] A.Batishcheva and O.Batishchev, Proc. 17th Int. Conf. on Num. Sim. of Plasmas, p.29, 2000.

Batishchev, Oleg

2001-06-01

67

Plasma transport induced by kinetic Alfven wave turbulence  

SciTech Connect

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

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

2012-10-15

68

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

69

Microscopic Lagrangian description of warm plasmas. IV - Macroscopic approximation  

NASA Technical Reports Server (NTRS)

The averaged-Lagrangian method is applied to linear wave propagation and nonlinear three-wave interaction in a warm magnetoplasma, in the macroscopic approximation. The microscopic Lagrangian treated by Kim and Crawford (1977) and by Galloway and Crawford (1977) is first expanded to third order in perturbation. Velocity integration is then carried out, before applying Hamilton's principle to obtain a general description of wave propagation and coupling. The results are specialized to the case of interaction between two electron plasma waves and an Alfven wave. The method is shown to be more powerful than the alternative possibility of working from the beginning with a macroscopic Lagrangian density.

Kim, H.; Crawford, F. W.

1983-01-01

70

Phase Transition in Dusty Plasmas: A Microphysical Description  

NASA Technical Reports Server (NTRS)

Dust grains immersed in plasma discharges acquire a large negative charge and settle into a dust cloud at the edge of the sheath. In this region, the plasma ions stream toward the electrode at a velocity u approx. cs=(T(sub e)/m(sub i))(exp 1/2). Experimentally at sufficiently high gas pressure P, the random kinetic energy of the grains is damped by gas friction, and the grains are strongly coupled and self-organize into a crystalline configuration. For lower pressures despite the dissipation of grain kinetic energy to gas friction, the dust grains reach a steady-state kinetic temperature T(sub d) which is much larger than the temperature of any other component in the plasma. T(sub d) is so large that the dust acts like a fluid. We have used the dynamically shielded dust (DSD) model to simulate these physical processes. We find that the known experimental features are nicely reproduced in the simulations, and that additional features are revealed. In the figure we plot the variation of T(sub d) as P is continuously varied in a DSD code run. A marked difference is evident between the critical pressure P(sub m) for the melting transition as P is decreased, and the critical pressure P(sub c) for the condensation transition as P is increased. For P(sub m) is less than P is less than P(sub c), mixed phase states are seen. This hysteresis occurs because the instability which triggers melting is different from the instability that heats the dust in the fluid phase and inhibits freezing. At low pressure, the dust is subject to a two-stream instability with the ions. This instability is responsible for the high temperature of the dust at low pressure. The basic physics underlying the melting transition has been elucidated in a series of papers. We are developing a first-principles analytic approach to the melting transition, which embodies the same physics that is present in the DSD code.

Joyce, Glenn; Ganguli, Gurudas; Lampe, Martin

2002-01-01

71

Kinetics of low-temperature plasmas for plasma-assisted combustion and aerodynamics  

NASA Astrophysics Data System (ADS)

Kinetic processes in a weakly ionized non-equilibrium plasma are considered under conditions that are typical for plasma-assisted ignition/combustion and flow control. The focus is on the simulation of active species production that leads to ignition delay reduction, flame stabilization and expansion of the flammability limit of combustible mixtures. We discuss the lack of information on electron cross sections for hydrocarbons and the accuracy of widely used approaches to simulate kinetics of active species production in air and combustible mixtures. Fast gas heating after a high-voltage nanosecond discharge is studied for various gas mixtures and reduced electric fields. We analyze the effect of negative ions generated in the afterglow of a high-voltage discharge with regard to plasma-assisted ignition and plasma aerodynamics application.

Aleksandrov, N. L.; Kindysheva, S. V.; Kochetov, I. V.

2014-02-01

72

Invariant-embedding and cognate kinetic descriptions of particle reflection/emission from surfaces  

E-print Network

Invariant-embedding and cognate kinetic descriptions of particle reflection/emission from surfaces 19 January 2007 Abstract The invariant-embedding (IE) approach, originally developed by Ambartsumyan. Ã? 2007 Published by Elsevier B.V. PACS: 02.30.Rz; 05.60.Ã?k; 34.50.Dy; 68.49.Jk Keywords: Invariant

Pázsit, Imre

73

Analysis of Electromagnetic Wave Propagation in a Magnetized Re-Entry Plasma Sheath Via the Kinetic Equation  

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

74

Realistic Plasma Sheet Models: Kinetic Reconstructions Using Cluster  

NASA Astrophysics Data System (ADS)

The Harris model has served for many years as the de-facto standard kinetic model for the tail plasma sheet. However, the model only rarely agrees with detailed satellite observations beyond roughly fitting the current profile. We present a reconstruction technique which can be used to fit the generalized quasi-isotropic class of models (which includes the Harris model and many others) to Cluster data. The resulting time-stationary reconstructions are self-consistent, with kinetic ions and fluid-like electrons. We apply the reconstruction technique to 30 Cluster plasma sheet crossings when the scale size was comparable to the ion inertial length. The 30 reconstructions show 3 different typical cases. Most commonly, the current is carried by diamagnetic ion currents, with small embedded perturbations from electron currents. Less common are thin, bifurcated sheets driven by electron Hall currents. A few cases are supported by anisotropic electron currents. The reconstructions point out the essential properties of a realistic plasma sheet model, and give insight into the stable thin current sheets that provide the initial conditions for reconnection and/or current disruption

Cully, C. M.; Ergun, R. E.

2008-12-01

75

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

76

Kinetic phenomena in charged particle transport in gases and plasmas  

SciTech Connect

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

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

2012-05-25

77

Kinetic Effects in Tokamak Scrape-off Layer Plasmas  

NASA Astrophysics Data System (ADS)

Transport modeling for the tokamak scrape-off layer is typically done using fluid theory which assumes short Coulomb collisional mean-free paths along the magnetic field, ?, in comparison with the connection length, L. This assumption is often violated for typical discharge parameters, especially above the thermal energy where most of the heat flux is carried; here ? ? ?^2 with ? being the energy. Thus, the tail of the distribution function can strongly depart from Maxwellian owing to nonlocal effects, modifying plasma transport, impurity radiation, and plasma-neutral gas interactions. These nonlocal effects become particularly pronounced for detached plasma conditions which are characterized by sharp gradients of plasma parameters along the magnetic field. These problems are addressed by developing a 1D-2V fully kinetic collisional time-dependent PIC code, W1, and its parallel-computer version, PW1. Both are used here to study divertor plasma detachment. New developments are presented that include a cross-field spatial dimension to assess the competition between radial and parallel transport in determining the SOL particle distribution functions, as well as impurity radiation and volume recombination. Short time-scale transport effects for ELMs in the tokamak edge are modeled also, and incomplete equilibration of the electron distribution function is observed. A comparison is made with a Fokker-Planck code ALLA and with experimental results. Results on the influence of kinetic effects on probe measurement interpretation, impurity radiation and parallel heat conductivity due to non-Maxwellian features in the SOL plasmas are presented and compared with ad hoc heat flux-limit models. Additional topics discussed are the sheath potential increase caused by hot electrons and plasma flow stagnation in the recycling region due to strong plasma-neutral particle interaction. In collaboration with X.Q. Xu, J.A. Byers, T.D. Rognlien, R.H. Cohen, S.I. Krasheninnikov, A.A. Batishcheva, P.J. Catto, M.M. Shoucri, and D.J. Sigmar. Work supported by the U.S.A. DoE Grants DE-FG02-88-ER-53263 at Lodestar, DE-FG02-91-ER-54109 at MIT, and W-7405-ENG-48 at LLNL.

Batishchev, O. V.

1996-11-01

78

A drift kinetic approach to stationary collisionless magnetic reconnection in an open cusp plasma  

E-print Network

A drift kinetic approach to stationary collisionless magnetic reconnection in an open cusp plasma J- nection requires a kinetic approach. Such approaches are rarely used due to the difficulties involved

Egedal, Jan

79

A drift kinetic approach to stationary collisionless magnetic reconnection in an open cusp plasma  

E-print Network

A drift kinetic approach to stationary collisionless magnetic reconnection in an open cusp plasma J treatment of magnetic recon­ nection requires a kinetic approach. Such approaches are rarely used due

Egedal, Jan

80

Fluid description of ion dynamics in a toroidally confined plasma  

SciTech Connect

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. [Institute for Fusion Studies, University of Texas, Austin, Texas 78712 (United States)

2005-05-15

81

Hybrid electrodynamics and kinetics simulation for electromagnetic wave propagation in weakly ionized hydrogen plasmas.  

PubMed

In this paper, a hybrid electrodynamics and kinetics numerical model based on the finite-difference time-domain method and lattice Boltzmann method is presented for electromagnetic wave propagation in weakly ionized hydrogen plasmas. In this framework, the multicomponent Bhatnagar-Gross-Krook collision model considering both elastic and Coulomb collisions and the multicomponent force model based on the Guo model are introduced, which supply a hyperfine description on the interaction between electromagnetic wave and weakly ionized plasma. Cubic spline interpolation and mean filtering technique are separately introduced to solve the multiscalar problem and enhance the physical quantities, which are polluted by numerical noise. Several simulations have been implemented to validate our model. The numerical results are consistent with a simplified analytical model, which demonstrates that this model can obtain satisfying numerical solutions successfully. PMID:23214707

Chen, Qiang; Chen, Bin

2012-10-01

82

Hybrid electrodynamics and kinetics simulation for electromagnetic wave propagation in weakly ionized hydrogen plasmas  

NASA Astrophysics Data System (ADS)

In this paper, a hybrid electrodynamics and kinetics numerical model based on the finite-difference time-domain method and lattice Boltzmann method is presented for electromagnetic wave propagation in weakly ionized hydrogen plasmas. In this framework, the multicomponent Bhatnagar-Gross-Krook collision model considering both elastic and Coulomb collisions and the multicomponent force model based on the Guo model are introduced, which supply a hyperfine description on the interaction between electromagnetic wave and weakly ionized plasma. Cubic spline interpolation and mean filtering technique are separately introduced to solve the multiscalar problem and enhance the physical quantities, which are polluted by numerical noise. Several simulations have been implemented to validate our model. The numerical results are consistent with a simplified analytical model, which demonstrates that this model can obtain satisfying numerical solutions successfully.

Chen, Qiang; Chen, Bin

2012-10-01

83

Solitary kinetic Alfvén waves in bi-ion plasmas  

NASA Astrophysics Data System (ADS)

In the presence of heavy ions a Sagdeev equation is obtained for the solitary kinetic Alfvén waves SKAWs in a low- beta m e m i ll beta ll1 or m i m e gg alpha gg 1 cold plasma Then the numerical solution can be calculated from the analytical expression and the basic equations set The results show that the density humps of SKAWs can exist in the sub-Alfvénic region and the heavy ion density amplitude and the width of the SKAWs rise with the increase in the initial density of heavy ions n b0 in such bi-ion plasmas The wave phase velocity decreases in this case The perturbed electromagnetic fields E z E x and B y are also studied further to discuss the effects of heavy ions on them These numerical results have been plotted for several different parameters

Yang, Y.; Wu, W.

84

Auto-ionization Effects on NLTE Kinetics of Laser Plasmas  

NASA Astrophysics Data System (ADS)

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

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

1998-11-01

85

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

SciTech Connect

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

86

Plasma physics for physicists  

Microsoft Academic Search

The physics of high-temperature plasmas are presented as a division of contemporary physics for physicists dealing with plasma phenomena outside characteristic plasma physics. Plasmas not in the presence of a magnetic field are treated, with attention given to plasma oscillations, particle collisions, transport phenomena, plasmas in high-frequency fields, the propagation of electromagnetic waves in a plasma, kinetic and hydrodynamic descriptions,

L. A. Artsimovich; R. Z. Sagdeev

1979-01-01

87

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

SciTech Connect

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

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

2012-05-15

88

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

NASA Astrophysics Data System (ADS)

Plasma-surface interactions during plasma etching are important in that, in addition to determining the rate and quality of the etch, they can also influence the properties of the bulk plasma. To address this coupling of bulk and surface processes the surface kinetics model (SKM) was developed as a module in the two-dimensional hybrid plasma equipment model (HPEM) with the goal of combining plasma chemistry and surface chemistry in a self-consistent fashion. The SKM obtains reactive fluxes to the surface from the HPEM, and generates the surface species coverages and the returning fluxes to the plasma by implementing a user defined surface reaction mechanism. Although the SKM is basically a surface-site-balance model, extensions to those algorithms have been made to include an overlying passivation layer through which reactants and products diffuse. Etching of Si in an inductively coupled plasma sustained in Ar/C2F6 was investigated using the SKM. Results from parametric studies are used to demonstrate the sensitivity of etching rates and polymer thickness to the sticking coefficient of fluorocarbon radicals on the reactor walls, polymer erosion rates and F atom diffusion through the polymer layer.

Zhang, Da; Kushner, Mark J.

2000-02-01

89

Advances in petascale kinetic plasma simulation with VPIC and Roadrunner  

SciTech Connect

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

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

2009-01-01

90

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

91

Covariant formulation of spatially non-symmetric kinetic equilibria in magnetized astrophysical plasmas  

NASA Astrophysics Data System (ADS)

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; Tessarotto, Massimo; Stuchlík, Zden?k

2014-05-01

92

Diamagnetic boundary layers - A kinetic theory. [for collisionless magnetized plasmas  

NASA Technical Reports Server (NTRS)

A kinetic theory is presented for boundary layers associated with MHD tangential 'discontinuities' in a collisionless magnetized plasma, such as those observed in the solar wind. The theory consists of finding self-consistent solutions of Vlasov's equation and Maxwell's equation for stationary one-dimensional boundary layers separating two Maxwellian plasma states. Layers in which the current is carried by electrons are found to have a thickness of the order of a few electron gyroradii, but the drift speed of the current-carrying electrons is found to exceed the Alfven speed, and accordingly such layers are not stable. Several types of layers in which the current is carried by protons are discussed; in particular, cases are considered in which the magnetic-field intensity, direction, or both, changed across the layer. In every case, the thickness was of the order of a few proton gyroradii, and the field changed smoothly, although the characteristics depended somewhat on the boundary conditions. The drift speed was always less than the Alfven speed, consistent with stability of such structures. These results are consistent with observations of boundary layers in the solar wind near 1 AU.

Lemaire, J.; Burlaga, L. F.

1976-01-01

93

Kinetic Monte Carlo simulation of escaping core plasma particles to the scrape-off layer for accurate response of plasma-facing components  

E-print Network

Kinetic Monte Carlo simulation of escaping core plasma particles to the scrape-off layer.1088/0029-5515/53/7/073023 Kinetic Monte Carlo simulation of escaping core plasma particles to the scrape-off layer for accurate on plasma-facing and nearby components. An ab initio Monte Carlo-based kinetic model of the escaping core

Harilal, S. S.

94

Alternative description of stochastic processes in nonlinear systems. ``Kinetic form'' of master and Fokker-Planck equations  

Microsoft Academic Search

An alternative description of stochastic processes in nonlinear systems is considered. It is shown that among the possible forms of the Fokker-Planck and the Langevin equations (Ito, Stratonovich, and kinetic forms) the kinetic form is more natural from the point of view of the statistical theory. A new form of the master equation for one-step processes is proposed which is

Yu. L. Klimontovich

1992-01-01

95

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

SciTech Connect

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

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

2008-10-15

96

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

97

A consistent description of kinetics and hydrodynamics of systems of interacting particles by means of the nonequilibrium statistical operator method  

E-print Network

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

98

Plasma treatment of mammalian vascular cells: a quantitative description  

Microsoft Academic Search

For the first time, quantitative data was obtained on plasma treatment of living mammalian cells. The nonthermal atmospheric discharge produced by the plasma needle was used for treatment of mammalian endothelial and smooth muscle cells. The influence of several experimental parameters on cell detachment and necrosis was tested using cell viability assays. Interruption of cell adhesion (detachment) was the most

Ingrid E. Kieft; Delphine Darios; Anton J. M. Roks; Eva Stoffels

2005-01-01

99

PLASMAKIN: A chemical kinetics library for plasma physics modeling  

NASA Astrophysics Data System (ADS)

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

Pinhao, Nuno

2007-10-01

100

Simulating radiation and kinetic processes in relativistic plasmas  

E-print Network

Modelling the emission properties of compact high energy sources such as X-ray binaries, AGN or gamma-ray bursts represents a complex problem. Contributions of numerous processes participate non linearly to produce the observed spectra: particle-particle, particle-photon and particle-wave interactions. In the past decades, numerical simulations have been widely used to address the key properties of the high energy plasmas present in these sources. This article presents a code that has been designed to investigate these questions. It includes most of the relevant processes needed to simulate the emission of high energy sources. This code solves the time-dependent kinetic equations for homogeneous, isotropic distributions of photons, electrons and positrons. No assumption is made on the shape of these distributions. Have been included so far: syn- chrotron self-absorbed radiation, Compton scattering, pair production/annihilation, e-e and e-p Coulomb collisions and some prescriptions for additional particle heating and acceleration. We also present comparisons with earlier works and some examples to illustrate the code computational capacities. Previous results are reproduced qualitatively but some differences are often found in the details of the particle As a first application of the code, we investigate acceleration by second order Fermi-like processes and we find that the energy threshold for acceleration has a crucial influence on the particle distribution and the emitted spectrum.

R. Belmont; J. Malzac; A. Marcowith

2008-08-08

101

CURRENT SHEETS AND COLLISIONLESS DAMPING IN KINETIC PLASMA TURBULENCE  

SciTech Connect

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

102

Effect of antenna size on electron kinetics in inductively coupled plasmas  

SciTech Connect

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

103

Implicit Methods for the Magnetohydrodynamic Description of Magnetically Confined Plasmas  

SciTech Connect

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

104

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

E-print Network

Kinetic Ignition Enhancement of Diffusion Flames by Nonequilibrium Magnetic Gliding Arc Plasma efficiently for ignition enhancement. I. Introduction THE development of hypersonic airbreathing propulsion combustor. Therefore, the total heat release, thrust, and propulsive efficiency cannot fully be realized

Ju, Yiguang

105

Dory-Guest-Harris instability as a benchmark for continuum kinetic Vlasov-Poisson simulations of magnetized plasmas  

NASA Astrophysics Data System (ADS)

The Dory-Guest-Harris instability is demonstrated to be a well-suited benchmark for continuum kinetic Vlasov-Poisson algorithms. The instability is a special case of perpendicularly-propagating kinetic electrostatic waves in a warm uniformly magnetized plasma. A complete derivation of the closed-form linear theory dispersion relation for the instability is presented. The electric field growth rates and oscillation frequencies specified by the dispersion relation provide concrete measures against which simulation results can be quantitatively compared. A fourth-order continuum kinetic algorithm is benchmarked against the instability, and is demonstrated to have good convergence properties and close agreement with theoretical growth rate and oscillation frequency predictions. Second-order accurate simulations are also shown to be consistent with theoretical predictions, but require higher resolution for convergence. The Dory-Guest-Harris instability benchmark extends the scope of current standard test problems by providing a substantive means of validating continuum kinetic simulations of magnetized plasmas in higher-dimensional 3D (x,vx,vy) phase space. The linear theory analysis, initial conditions, algorithm description, and comparisons between theoretical predictions and simulation results are presented.

Vogman, G. V.; Colella, P.; Shumlak, U.

2014-11-01

106

Vlasov's kinetic theory of the collective charged particle beam transport through a magnetized plasma in the strongly nonlocal regime  

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

Electrical and Kinetic Model of an Atmospheric RF Device for Plasma Aerodynamics Applications  

E-print Network

The asymmetrically mounted flat plasma actuator is studied using a self-consistent 2-DIM fluid model at atmospheric pressure. The computational model use the drift-diffusion approximation and a simple plasma phenomenological kinetic model. It is investigated its electrical and kinetic properties, and calculated the charged species concentrations, surface charge density, electrohydrodynamic forces and gas speed. The present computational model contributes to understand the main physical mechanisms and methods to improve its performance.

Pinheiro, Mario J

2009-01-01

108

Effect of on-line conductivity plasma ultrafiltrate kinetic modeling on cardiovascular stability of hemodialysis patients  

Microsoft Academic Search

Effect of on-line conductivity plasma ultrafiltrate kinetic modeling on cardiovascular stability of hemodialysis patients. The aim of this multicenter, prospective, randomized cross-over study was to clarify whether on-line conductivity ultrafiltrate kinetic modeling (treatment B), as a substitute for sodium kinetic modeling, is capable of reducing intradialytic cardiovascular instability in comparison with standard treatment (treatment A), by reducing the sodium balance

Francesco Locatelli; Simeone Andrulli; Salvatore Di Filippo; Bruno Redaelli; Stefano Mangano; Carlo Navino; Rosario Ariano; Marco Tagliaferri; Tommaso Fidelio; Mauro Corti; Silvia Civardi; Ciro Tetta

1998-01-01

109

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

SciTech Connect

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

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

2012-07-15

110

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

SciTech Connect

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

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

2009-05-15

111

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

Microsoft Academic Search

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

112

Impact of kinetic processes on the macroscopic nonlinear evolution of the electromagnetic-beam-plasma instability  

PubMed

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

113

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

E-print Network

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

114

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

Microsoft Academic Search

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

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

115

Fully kinetic simulations of dense plasma focus Z-pinch devices.  

PubMed

Dense plasma focus 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 (~10(7)) and high-energy (MeV) beams for the first time. We compare our fluid, hybrid (kinetic ions and fluid electrons), and fully kinetic simulations. Fluid simulations predict no neutrons and do not allow for nonthermal ions, while hybrid simulations underpredict neutron yield by ~100x and exhibit an ion tail that does not exceed 200 keV. Only fully kinetic simulations predict MeV-energy ions and experimental neutron yields. A frequency analysis in a fully kinetic simulation shows plasma fluctuations near the lower hybrid frequency, possibly implicating lower hybrid drift instability as a contributor to anomalous resistivity in the plasma. PMID:23215497

Schmidt, A; Tang, V; Welch, D

2012-11-16

116

Chemical kinetics of low pressure high density hydrogen plasmas: application to negative ion sources for ITER  

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

117

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

NASA Astrophysics Data System (ADS)

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

Roark, Christine; Smithe, David; Stoltz, Peter

2011-11-01

118

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

SciTech Connect

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

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

1990-02-26

119

The 3H-leucine tracer: its use in kinetic studies of plasma lipoproteins.  

PubMed

3H-leucine administered as a bolus has been widely used as a tracer in kinetic investigations of protein synthesis and secretion. After intravenous injection, plasma specific radioactivity decays over several orders of magnitude during the first half-day, followed by a slow decay lasting a number of weeks that results from recycling of the leucine tracer as proteins are degraded and 3H-leucine reenters the plasma pool. In studies in which kinetic data are analyzed by mathematical compartmental modeling, plasma leucine activity is generally used as a forcing function to drive the input of 3H-leucine into the protein synthesis pathway. 3H-leucine is an excellent tracer during the initial hours of rapidly decreasing plasma activity; thereafter, reincorporation of recycled tracer into new protein synthesis obscures the tracer data from proteins with slower turnover rates. Thus, for proteins such as plasma albumin and apolipoprotein (apo) A-I, this tracer is unsatisfactory for measuring fractional catabolic (FCR) and turnover rates. By contrast, the kinetics of plasma very-low-density lipoprotein (VLDL)-apoB, a protein with a residence time of approximately 5 hours, are readily measured, since kinetic parameters of this protein can be determined by the time plasma leucine recycling becomes established. However, measurement of VLDL-apoB specific radioactivity extending up to 2 weeks provides further data on the kinetic tail of VLDL-apoB. Were plasma leucine a direct precursor for the leucine in VLDL-apoB, the kinetics of the plasma tracer should determine the kinetics of the protein. However, this is not the case, and the deviations from linearity are interpreted in terms of (1) the dilution of plasma leucine in the liver by unlabeled dietary leucine; (2) the recycling of hepatocellular leucine from proteins within the liver, where recycled cellular leucine does not equilibrate with plasma leucine; and (3) a "hump" in the kinetic data of VLDL-apoB, which we interpret to reflect recycling or retention of a portion of the apoB protein within the hepatocyte, with its subsequent secretion. Because hepatocellular tRNA is the immediate precursor for synthesis of these secretory proteins, its kinetics should be used as the forcing function to drive the modeling of this system. The VLDL-apoB tail contains the information needed to modify the plasma leucine data, to provide an appropriate forcing function when using 3H-leucine as a tracer of apolipoprotein metabolism. This correction is essential when using 3H-leucine as a tracer for measuring low-density lipoprotein (LDL)-apoB kinetics. The 3H-leucine tracer also highlights the importance of recognizing the difference between plasma and system residence times, the latter including the time the tracer resides within exchanging extravascular pools. The inability to determine these fractional exchange coefficients for apoA-I and albumin explains the failure of this tracer in kinetic studies of these proteins. For apoB-containing lipoproteins, plasma residence times are generally determined, and these measurements can be made satisfactorily with 3H-leucine. PMID:9054478

Fisher, W R; Venkatakrishnan, V; Fisher, E S; Stacpoole, P W; Zech, L A

1997-03-01

120

Theory of Underdense Laser-Plasma Interactions with Photon Kinetic Theory  

NASA Astrophysics Data System (ADS)

We review recent developments in the theory of laser-plasma interactions, with a focus on generalisations of the theory of parametric instabilities driven by lasers in underdense plasmas to include the effects of broadband or partially incoherent radiation via generalised photon kinetic theory. After an introduction addressing the fundamental concepts underlying parametric instabilities, the key concepts and techniques of photon kinetic theory are presented, along with the steps required to obtain the generalised dispersion relations for the different parametric instabilities. The main details of generalised photon kinetic theory are presented such that this chapter can also be used as reference for future work on generalised photon kinetic theory. As a particular example of the application of this theoretical approach, focus will be given to the derivation of the dispersion relation for stimulated Brillouin scattering (SBS). The main results for stimulated Raman scattering (SRS) by a broadband or partially coherent radiation pump field will also be reviewed.

Silva, Luis O.; Bingham, Robert

121

Nonstationary kinetic theory of ion transport in plasma with small perturbations  

SciTech Connect

A theory of charged particle transport for small potential perturbations in a fully ionized plasma is developed on the basis of solving a linearized kinetic equation with the Landau collision integral. This theory is free of any constraints on the characteristic time and spatial scales of perturbations. Ion fluxes appropriate for an arbitrary ion-ion collision frequency that can ensure nonlocal space-time transport in the plasma are calculated. The obtained ion transport coefficients are used to calculate the partial contribution of ions to the longitudinal permittivity of collisional plasma. The resulting expression for the plasma permittivity is applicable in the entire range of frequencies and wavenumbers.

Brantov, A. V., E-mail: brantov@sci.lebedev.ru; Bychenkov, V. Yu. [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation); Rozmus, W. [University of Alberta, Department of Physics (Canada)

2013-05-15

122

Fully kinetic numerical modeling of a plasma thruster  

E-print Network

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

123

Plasma membrane recovery kinetics of a microfluidic intracellular delivery platform  

E-print Network

Intracellular delivery of materials is a challenge in research and therapeutic applications. Physical methods of plasma membrane disruption have recently emerged as an approach to facilitate the delivery of a variety of ...

Poceviciute, Roberta

124

Quartz crystal microbalance for the cardiac markers/antibodies binding kinetic measurements in the plasma samples  

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

125

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

E-print Network

A fluid description for the discharge equilibrium of a divergent electron cyclotron resonance-field particle motion occurs only through a static EXB drift. Closure is obtained by neglecting third and the equilibrium neutral gas density, and (2) the absorbed microwave power and the equilibrium plasma density

Mauel, Michael E.

126

Kinetic dissipation and anisotropic heating in a turbulent collisionless plasma  

SciTech Connect

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

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

2009-03-15

127

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

SciTech Connect

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

128

Water bag model for kinetic Raman scattering in a nonuniform plasma  

NASA Astrophysics Data System (ADS)

Resonant wave interactions play a major role in plasmas and other nonlinear media. Resonantly driven waves may exhibit autoresonance, i.e. a continuous nonlinear phase-locking despite variation of system parameters [1]. Recently, we have presented a kinetic autoresonant plasma wave paradigm, where a driven BGK mode was excited in a uniform plasma by slow variation of the driving wave frequency [2]. Similarly, autoresonant BGK modes can be excited in nonuniform plasmas, driven by a constant frequency wave resulting from beating between two laser beams. We will suggest a water-bag model of a nonuniform plasma and formulate a Lagrangian theory of autoresonant three-wave interactions involving two laser waves and a BGK mode. The evolution of such a driven BGK mode will be illustrated in Liouville-type numerical simulations.[4pt] [1] L. Friedland, Scholarpedia 4, 5473 (2009).[0pt] [2] P. Khain and L. Friedland, Phys. Plasmas 17, 102308 (2010).

Friedland, Lazar; Khain, Pavel

2011-11-01

129

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

130

EXCITATION OF KINETIC ALFVEN WAVES BY DENSITY STRIATION IN MAGNETO-PLASMAS  

SciTech Connect

Field-aligned density striation is one of the most common inhomogeneity phenomena in magneto-plasmas, such as in the solar coronal plasma and terrestrial auroral plasma. Kinetic Alfven waves (KAWs) can play an important role in the inhomogeneous heating of coronal magneto-plasmas as well as in the local acceleration of auroral energetic electrons. In this paper, we study the dispersion and instability of KAWs in a magneto-plasma with density striation structures. Results show that KAWs become unstable in the presence of the density striation and the corresponding instability has a maximal growth rate at the perpendicular wavelength close to the spatial scale of the density gradient. Related experimental phenomena in both laboratory and space plasmas are discussed. It is suggested that the excitation of KAWs by the density striation of magneto-plasmas can be of potential importance in understanding the physics of the formation of magneto-plasma filaments and their heating mechanisms, which are often present in the terrestrial auroral plasma, the solar coronal plasma, and other astrophysical plasmas.

Wu, D. J.; Chen, L., E-mail: clvslc214@pmo.ac.cn [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

2013-07-01

131

Radar probing of ionospheric plasmas precisely confirms linear kinetic plasma theory (Hannes Alfvén Medal Lecture)  

NASA Astrophysics Data System (ADS)

In 1958 W. E. Gordon first suggested that huge radars could probe the ionosphere via scattering from independent electrons, even though the radar cross section of a single electron is only 10-28 m2. This suggestion quickly led to the construction of two enormous radars in the early 1960s, one near Lima, Peru, and one near Arecibo, Puerto Rico. It soon became apparent that the theory of this scatter was more complicated than originally envisaged by Gordon. Although the new theory was more complicated, it was much richer: by measuring the detailed shape of the Doppler frequency spectrum (or alternatively the signal autocorrelation function, the ACF), a radar researcher could determine many, if not most, of the parameters of interest of the plasma. There is now a substantial network of major radar facilities scattered from the magnetic equator (Peru) to the high arctic latitudes (Svalbard and Resolute Bay), all doing important ionospheric research. The history of what is now called Incoherent Scatter (even though it is not truly incoherent) is fascinating, and I will touch on a few highlights. The sophisticated radar and data processing techniques that have been developed are also impressive. In this talk, however, I want to focus mainly on the details of the theory and on how the radar observations have confirmed the predictions of classical linear plasma kinetic theory to an amazingly high degree of precision, far higher than has any other technique that I am aware of. The theory can be, and has been, developed from two very different points of view. One starts with 'dressed particles,' or Coulomb 'clouds' around ions and electrons moving with a Maxwellian velocity distribution; the second starts by considering all the charged particles to be made up of a spectrum of density plane waves and then invokes a generalized version of the Nyquist Noise Theorem to calculate the thermal amplitudes of the waves. Both approaches give exactly the same results, results that allow us to predict exactly the scattered power and Doppler spectrum for any given set of plasma parameters (e.g., electron and ion temperatures, ionic composition, mean drifts and currents, the geomagnetic field, and particle collisions). So far, these predictions have not failed, although in recent years we have had to resort to numerical simulations to do a proper calculation of electron Coulomb collisions when the radar beam is pointed very nearly perpendicular to the magnetic field. This is because no analytic way has yet been found to properly apply the Fokker-Planck Coulomb collision model to the scattering process. Of course the theory predicts the spectrum, given all the plasma parameters, when what we really want to do in ionospheric research is the inverse, namely find the parameters, given the radar data. This inverse process can be quite difficult to do optimally if there are too many unknown parameters. Statistical inverse theory can require enormous computing power, but progress is being made.

Farley, Donald

2010-05-01

132

Kinetics of low temperature plasma carburizing of austenitic stainless steels  

Microsoft Academic Search

A low temperature plasma carburizing technique has recently been developed to engineer the surfaces of austenitic stainless steels for combined improvement in wear and corrosion resistance. The resultant carburized layer is characterized by the supersaturation of carbon in austenite lattices, the much-increased hardness and wear resistance, and most importantly its superior corrosion resistance. This paper presents recent experimental results on

Y. Sun

2005-01-01

133

ON PLASMA KINETIC MODEL OF A 3D SOLAR CORONA AND SOLAR WIND AT HELIOSPHERIC SHEET  

Microsoft Academic Search

The dynamical solar corona in 3D consists of transient type magnetic island elements and radial type magnetic flux rope structures in a heliospheric sheet. During the formation and relaxation these elements produce inductive elec- tromagnetic fields where energetic particles are produced. We study the 3D corona formation in the kinetic approach and parameterize it like a hot current-carrying collisionless plasma

V. M. GUBCHENKO; M. L. KHODACHENKO; H. K. BIERNAT

134

American Institute of Aeronautics and Astronautics Kinetic Effects of Non-Equilibrium Plasma on Partially  

E-print Network

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

135

Comparisons of dense-plasma-focus kinetic simulations with experimental measurements  

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 and past optimization efforts of these devices have been largely empirical. Previously we reported on fully kinetic simulations of a DPF and compared them with hybrid and fluid simulations of the same device. Here we present detailed comparisons between fully kinetic simulations and experimental data on a 1.2 kJ DPF with two electrode geometries, including neutron yield and ion beam energy distributions. A more intensive third calculation is presented which examines the effects of a fully detailed pulsed power driver model. We also compare simulated electromagnetic fluctuations with direct measurement of radiofrequency electromagnetic fluctuations in a DPF plasma. These comparisons indicate that the fully kinetic model captures the essential physics of these plasmas with high fidelity, and provide further evidence that anomalous resistivity in the plasma arises due to a kinetic instability near the lower hybrid frequency.

Schmidt, A.; Link, A.; Welch, D.; Ellsworth, J.; Falabella, S.; Tang, V.

2014-06-01

136

Kinetic theory on the current-filamentation instability in collisional plasmas  

SciTech Connect

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 [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 100080 (China); Sheng, Z.-M.; Zhang, J. [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, Chinese Academy of Science, Beijing 100080 (China); Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China)

2008-08-15

137

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

NASA Astrophysics Data System (ADS)

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.; Scime, Earl E.; Dwivedi, N. K.

2014-04-01

138

Kinetic simulations of argon dusty plasma afterglow including metastable atom kinetics  

SciTech Connect

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

139

Major accidents scenarios used for LUP and off-site emergency planning : Importance of kinetic description  

E-print Network

Major accidents scenarios used for LUP and off-site emergency planning : Importance of kinetic in particular, faced with several industrial accidents, like one of the most serious one, the AZF explosion. Keywords : Land Use Planning ; off-site emergency planning ; chemical accident scenario ; kinetic 1

Paris-Sud XI, Université de

140

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

PubMed

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

Wang, Hui-juan; Chen, Xiao-yang

2011-02-28

141

Simulating radiation and kinetic processes in relativistic plasmas  

Microsoft Academic Search

Context: Modelling the emission properties of compact high energy sources such as X-ray binaries, AGN or gamma-ray bursts represents a complex problem. Contributions of numerous processes participate non linearly to produce the observed spectra: particle-particle, particle-photon and particle-wave interactions. Numerical simulations have been widely used to address the key properties of the high energy plasmas present in these sources. Aims:

R. Belmont; J. Malzac; A. Marcowith

2008-01-01

142

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

SciTech Connect

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

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

2012-11-15

143

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

NASA Astrophysics Data System (ADS)

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

144

Kinetic shear Alfvén instability in the presence of impurity ions in tokamak plasmas  

SciTech Connect

The effects of impurity ions on the kinetic shear Alfvén (KSA) instability in tokamak plasmas are investigated by numerically solving the integral equations for the KSA eigenmode in the toroidal geometry. The kinetic effects of hydrogen and impurity ions, including transit motion, finite ion Larmor radius, and finite-orbit-width, are taken into account. Toroidicity induced linear mode coupling is included through the ballooning-mode representation. Here, the effects of carbon, oxygen, and tungsten ions on the KSA instability in toroidal plasmas are investigated. It is found that, depending on the concentration and density profile of the impurity ions, the latter can be either stabilizing or destabilizing for the KSA modes. The results here confirm the importance of impurity ions in tokamak experiments and should be useful for analyzing experimental data as well as for understanding anomalous transport and control of tokamak plasmas.

Lu, Gaimin; Shen, Y.; Xie, T.; He, Zhixiong; He, Hongda [Southwestern Institute of Physics, P. O. Box 432, Chengdu 610041 (China)] [Southwestern Institute of Physics, P. O. Box 432, Chengdu 610041 (China); Qi, Longyu [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China)] [Institute for Fusion Theory and Simulation, Zhejiang University, Hangzhou 310027 (China); Cui, Shaoyan [School of Mathematics and Information, Ludong University, Yantai 264025 (China)] [School of Mathematics and Information, Ludong University, Yantai 264025 (China)

2013-10-15

145

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

146

The Fluid-Kinetic Particle-in-Cell method for plasma simulations  

NASA Astrophysics Data System (ADS)

A method that solves concurrently the multi-fluid and Maxwell's equations has been developed for plasma simulations. By calculating the stress tensor in the multi-fluid momentum equation by means of computational particles moving in a self-consistent electromagnetic field, the kinetic effects are retained while solving the multi-fluid equations. The Maxwell's and multi-fluid equations are discretized implicitly in time enabling kinetic simulations over time scales typical of the fluid simulations. The Fluid-Kinetic Particle-in-Cell method has been implemented in a three-dimensional electromagnetic code, and tested against the two-stream instability, the Weibel instability, the ion cyclotron resonance and magnetic reconnection problems. The method is a promising approach for coupling fluid and kinetic methods in a unified framework.

Markidis, Stefano; Henri, Pierre; Lapenta, Giovanni; Rönnmark, Kjell; Hamrin, Maria; Meliani, Zakaria; Laure, Erwin

2014-08-01

147

Kinetic theory of a two-dimensional magnetized plasma. II - Balescu-Lenard limit.  

NASA Technical Reports Server (NTRS)

The kinetic theory of a two-dimensional one-species plasma in a uniform dc magnetic field is investigated in the small plasma parameter limit. The plasma consists of charged rods interacting through the logarithmic Coulomb potential. Vahala and Montgomery earlier (1971) derived a Fokker-Planck equation for this system, but it contained a divergent integral, which had to be cut off on physical grounds. This cutoff is compared to the standard cutoff introduced in the two-dimensional unmagnetized Fokker-Planck equation. In the small plasma parameter limit, it is shown that the Balescu-Lenard collision term is zero in the long time average limit if only two-body interactions are considered. The energy transfer from a test particle to an equilibrium plasma is discussed and is also shown to be zero in the long time average limit. This supports the unexpected result of zero Balescu-Lenard collision term.

Vahala, G.

1972-01-01

148

0.374 Pflop\\/s trillion-particle kinetic modeling of laser plasma interaction on roadrunner  

Microsoft Academic Search

We demonstrate the outstanding performance and scalability of the VPIC kinetic plasma modeling code on the heterogeneous IBM Roadrunner supercomputer at Los Alamos National Laboratory. VPIC is a three-dimensional, relativistic, electromagnetic, particle-in-cell (PIC) code that self-consistently evolves a kinetic plasma. VPIC simulations of laser plasma interaction were conducted at unprecedented fidelity and scale-up to 1.0 times 1012 particles on as

K. J. Bowers; B. J. Albright; B. Bergen; L. Yin; K. J. Barker; D. J. Kerbyson

2008-01-01

149

Orszag Tang vortex - Kinetic study of a turbulent plasma  

SciTech Connect

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

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

2010-03-25

150

Observation of Kinetic Plasma Jets in a Coronal-Loop Simulation Experiment S. K. P. Tripathi,* P. M. Bellan, and G. S. Yun  

E-print Network

Observation of Kinetic Plasma Jets in a Coronal-Loop Simulation Experiment S. K. P. Tripathi,* P. M) Under certain conditions an intense kinetic plasma jet is observed to emerge from the apex of laboratory, labeled as ``kinetic plasma jet'' in Fig. 1, was discovered experimentally and then modeled. We first

Bellan, Paul M.

151

Growth kinetics of silicon dioxide on silicon in an inductively coupled rf plasma at constant anodization currents  

Microsoft Academic Search

The kinetics of plasma oxidation of silicon at constant anodization current have been investigated. Oxidation was performed in an inductively coupled rf plasma anodization setup. The oxidation model is based on the assumption that the oxidant from the plasma is neutral atomic oxygen which captures an electron inside the oxide and forms a negative oxygen ion (O?). The O? ion

A. J. Choksi; R. Lal; A. N. Chandorkar

1992-01-01

152

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

153

A Hybrid Fluid-Kinetic Theory for Plasma Physics  

E-print Network

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

154

Kinetic study of the secondary plasma created in the ITER neutraliser  

SciTech Connect

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

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

2009-03-12

155

Plasma surface functionalization and dyeing kinetics of Pan-Pmma copolymers  

NASA Astrophysics Data System (ADS)

Fiber surface modification with air corona plasma has been studied through dyeing kinetics under isothermal conditions at 30 °C on an acrylic-fiber fabric with a cationic dye (CI Basic Blue 3) analyzing the absorption, desorption and fixing on the surface of molecules having defined cationic character. The initial dyeing rate in the first 60 s indicates an increase of 58.3% in the dyeing rate due to the effect of corona plasma on the acrylic fiber surface. At the end of the dyeing process, the plasma-treated fabrics absorb 24.7% more dye, and the K/S value of the acrylic fabric increases by 8.8%. With selected dyestuff molecules, new techniques can be designed to amplify the knowledge about plasma-treated surface modifications of macromolecules.

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

2013-10-01

156

3D Kinetic Simulation of Plasma Jet Penetration in Magnetic Field  

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

157

Kinetics of complex plasmas having spherical dust particles with a size distribution  

SciTech Connect

This paper presents an analysis of the kinetics of an illuminated complex plasma having spherical dust particles with a size distribution. It has been pointed out that in the steady state, the electric potential on the surface of all the particles is the same; as a corollary, all particles carry a charge of the same sign. It is seen that in the steady state, the plasma parameters are determined by the number per unit volume and root mean square radius of the dust particles. This fact makes the analysis similar to that for a complex plasma with dust of uniform size. It is seen that it is essential to consider both the number and energy balance of the constituents of the complex plasma. A parametric analysis, a discussion of the numerical results thus obtained, and conclusions have also been given.

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

2010-11-15

158

Kinetic Alfvén wave instability driven by a field-aligned current in high-? plasmas.  

PubMed

Including the ion-gyroradius effect, a general low-frequency kinetic dispersion equation is presented, which simultaneously takes account of a field-aligned current and temperature anisotropy in plasmas. Based on this dispersion equation, kinetic Alfvén wave (KAW) instability driven by the field-aligned current, which is carried by the field-aligned drift of electrons relative to ions at a drift velocity V(D), is investigated in a high-? plasma, where ? is the kinetic-to-magnetic pressure ratio in the plasma. The numerical results show that the KAW instability driven by the field-aligned current has a nonzero growth rate in the parallel wave-number range 0plasma particles, the result shows that the instability conditions for these two driven mechanisms are both modified considerably, in which the growing parametric ranges of KAWs widen. The results have potential importance in understanding the physics of space and astrophysical plasma active phenomena since the field-aligned current, also called the Birkeland current, is one of the most active factors in plasma phenomena. PMID:22181282

Chen, L; Wu, D J; Hua, Y P

2011-10-01

159

On PIC-Fokker-Planck hybrid for kinetic modeling of plasmas  

NASA Astrophysics Data System (ADS)

Traditional approach to kinetic simulation of plasmas utilizes either PIC or Vlasov (Fokker-Planck) method. There are well known shortcomings for both of the approaches. For instance, PIC suffers from high statistical noise, while Vlasov shows high numerical diffusion. New hybrid method [1] combines best features of the two methods by suppressing both numerical noise and numerical diffusion. Relative effectiveness of PIC, Vlasov and hybrid methods is demonstrated for a classical problem of non-linear saturation of a strong beam-plasma instability [2]. Further development of the hybrid PIC-Vlasov method [4] for the kinetic modeling of mixed-collisional plasma is discussed. First results on coupling of our hybrid particle-mesh method with adaptive RRC method [3], which uses adaptive grid refinement and coarsening, are presented. [1] O.Batishchev, Proc. 17th Int. Conf. on Num. Sim. Plasmas, p.24, Banff, Canada, May 2000; [2] O.Batishchev et al., Bull. APS 45 (7) 72, APS DPP meeting, Quebec City, Canada, October 2000; [3] A.Batishcheva and O.Batishchev, Proc. 17th Int. Conf. on Num. Sim. Plasmas, p.29, 2000; [4] O.Batishchev, APS DcomP-2001 meeting, R1.025, Cambridge, June 2001.

Batishchev, Oleg

2001-10-01

160

Kinetics of ions during the development of parametric instability of intensive Langmuir waves in plasma  

E-print Network

Nonlinear regimes of one-dimensional parametric instabilities of long-wave plasma waves are considered for the cases when the average plasma field energy density is less (Zakharov's model) or greater (Silin's model) than the plasma thermal energy density. The hybrid models presented in this paper treat the electrons as a fluid by way of an equation for the high-frequency wave and treat the ions kinetically with a super-particle simulation. This makes possible consideration of non-resonant particles trapped by high-frequency oscillations and the influence of trajectory crossing on the development of the parametric instability. The evolution of ion energy distribution is studied. It is shown that after saturation of the instability, the ion kinetic energy density normalized to the initial field energy density is of the order of the ratio of linear growth rate to the plasma frequency, for the case when the initial field energy far exceeds the plasma thermal energy. In this case, the ion energy distribution is di...

Kirichok, A V; Pryjmak, A V; Zagorodny, A G

2014-01-01

161

Kinetics of intracellular transport and sorting of lysosomal membrane and plasma membrane proteins  

PubMed Central

We have used monospecific antisera to two lysosomal membrane glycoproteins, lgp120 and a similar protein, lgp110, to compare the biosynthesis and intracellular transport of lysosomal membrane components, plasma membrane proteins, and lysosomal enzymes. In J774 cells and NRK cells, newly synthesized lysosomal membrane and plasma membrane proteins (the IgG1/IgG2b Fc receptor or influenza virus hemagglutinin) were transported through the Golgi apparatus (defined by acquisition of resistance to endo-beta-N-acetylglucosaminidase H) with the same kinetics (t1/2 = 11-14 min). In addition, immunoelectron microscopy of normal rat kidney cells showed that lgp120 and vesicular stomatitis virus G-protein were present in the same Golgi cisternae demonstrating that lysosomal and plasma membrane proteins were not sorted either before or during transport through the Golgi apparatus. To define the site at which sorting occurred, we compared the kinetics of transport of lysosomal and plasma membrane proteins and a lysosomal enzyme to their respective destinations. Newly synthesized proteins were detected in dense lysosomes (lgp's and beta-glucuronidase) or on the cell surface (Fc receptor or hemagglutinin) after the same lag period (20-25 min), and accumulated at their final destinations with similar kinetics (t1/2 = 30-45 min), suggesting that these two lgp's are not transported to the plasma membrane before reaching lysosomes. This was further supported by measurements of the transport of membrane- bound endocytic markers from the cell surface to lysosomes, which exhibited additional lag periods of 5-15 min and half-times of 1.5-2 h. The time required for transport of newly synthesized plasma membrane proteins to the cell surface, and for the transport of plasma membrane markers from the cell surface to lysosomes would appear too long to account for the rapid transport of lgp's from the Golgi apparatus to lysosomes. Thus, the observed kinetics suggest that lysosomal membrane proteins are sorted from plasma membrane proteins at a post-Golgi intracellular site, possibly the trans Golgi network, before their delivery to lysosomes. PMID:2821012

1987-01-01

162

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

SciTech Connect

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

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

2010-07-23

163

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

SciTech Connect

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

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

2011-09-15

164

Fast electron energy deposition in a magnetized plasma: Kinetic theory and particle-in-cell simulation  

SciTech Connect

The collisional dynamics of a relativistic electron jet in a magnetized plasma are investigated within the framework of kinetic theory. The relativistic Fokker-Planck equation describing slowing down, pitch angle scattering, and cyclotron rotation is derived and solved. Based on the solution of this Fokker-Planck equation, an analytical formula for the root mean square spot size transverse to the magnetic field is derived and this result predicts a reduction in radial transport. Some comparisons with particle-in-cell simulation are made and confirm striking agreement between the theory and the simulation. For fast electron with 1 MeV typical kinetic energy interacting with a solid density hydrogen plasma, the energy deposition density in the transverse direction increases by a factor 2 for magnetic field of the order of 1 T. Along the magnetic field, the energy deposition profile is unaltered compared with the field-free case.

Robiche, J. [Centre de Physique Theorique, Ecole Polytechnique, Route de Saclay, 91 128 Palaiseau Cedex (France); Rax, J.-M. [Laboratoire de Physique et Technologie des Plasma, Ecole Polytechnique, Route de Saclay, 91 128 Palaiseau Cedex (France); Bonnaud, G. [Institut National des Sciences et Techniques Nucleaires, 91 191 Gif-sur-Yvette (France); Gremillet, L. [DAM, DIF, CEA, F-91297 Arpajon (France)

2010-03-15

165

From cold to fusion plasmas: spectroscopy, molecular dynamics and kinetic considerations  

NASA Astrophysics Data System (ADS)

Non-equilibrium effects in hydrogen plasmas have been investigated in different systems, ranging from RF plasmas to corona discharges. The existing measurements of vibrational and rotational temperatures, obtained by different spectroscopical techniques, are reported, rationalized by results calculated by kinetic models. Input data of these models are discussed with particular attention on the dependence of relevant cross sections on the vibrational quantum number. Moreover, the influence of the vibrational excitation of H2 molecules on the translational distribution of atoms in ground and excited levels is shown. Finally, a collisional radiative model for atomic hydrogen levels, based on the coupling of the Boltzmann equation for electron energy distribution function (EEDF) and the excited state kinetics, is presented, emphasizing the limits of quasi-stationary approximation. In the last case, large deviations of the EEDF and atomic level distributions from the equilibrium are observed.

Capitelli, M.; Celiberto, R.; Colonna, G.; D'Ammando, G.; De Pascale, O.; Diomede, P.; Esposito, F.; Gorse, C.; Laricchiuta, A.; Longo, S.; Pietanza, L. D.

2010-07-01

166

Fokker-Planck kinetic modeling of suprathermal ?-particles in a fusion plasma  

NASA Astrophysics Data System (ADS)

We present an ion kinetic model describing the transport of suprathermal ?-particles in inertial fusion targets. The analysis of the underlying physical model enables us to develop efficient numerical methods to simulate the creation, transport and collisional relaxation of fusion reaction products (?-particles) at a kinetic level. The model assumes spherical symmetry in configuration space and axial symmetry in velocity space around the mean flow velocity. A two-energy-scale approach leads to a self-consistent modeling of the coupling between suprathermal ?-particles and the thermal bulk of the imploding plasma. This method provides an accurate numerical treatment of energy deposition and transport processes involving suprathermal particles. The numerical tools presented here are then validated against known analytical results. This enables us to investigate the potential role of ion kinetic effects on the physics of ignition and thermonuclear burn in inertial confinement fusion schemes.

Peigney, B. E.; Larroche, O.; Tikhonchuk, V.

2014-12-01

167

Fokker Planck kinetic modeling of suprathermal alpha-particles in a fusion plasma  

E-print Network

We present an ion kinetic model describing the ignition and burn of the deuterium-tritium fuel of inertial fusion targets. The analysis of the underlying physical model enables us to develop efficient numerical methods to simulate the creation, transport and collisional relaxation of fusion reaction products (alpha-particles) at a kinetic level. A two-energy-scale approach leads to a self-consistent modeling of the coupling between suprathermal alpha-particles and the thermal bulk of the imploding plasma. This method provides an accurate numerical treatment of energy deposition and transport processes involving suprathermal particles. The numerical tools presented here are validated against known analytical results. This enables us to investigate the potential role of ion kinetic effects on the physics of ignition and thermonuclear burn in inertial confinement fusion schemes.

Peigney, Benjamin-Edouard; Tikhonchuk, Vladimir

2014-01-01

168

Remote plasma-enhanced CVD of silicon: Reaction kinetics as a function of growth parameters  

Microsoft Academic Search

The reaction kinetics in Remote Plasma-enhanced Chemical Vapor Deposition (RPCVD) have been studied for a chamber pressure\\u000a of 200 mTorr, rf powers between 4 and 8 W, diluted silane flow rates between 5 and 40 sccm, and temperatures between 190 and\\u000a 480 C. The observed temperature dependence of growth rate reveals a change in activation energy at 300–325 C, suggesting

B. Anthony; T. Hsu; L. Breaux; R. Qian; S. Banerjee; A. Tasch

1990-01-01

169

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

SciTech Connect

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

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

2008-01-18

170

Plasma deposition of thin film silicon: kinetics monitored by optical emission spectroscopy  

Microsoft Academic Search

The optical emission spectroscopy technique is used to characterise the temporal behaviour of a pure silane plasma in the first 90s after ignition of a static closed-chamber very high frequency glow discharge. Special interest is drawn to the formation of microcrystalline silicon (?c-Si:H) in absence of any hydrogen feedstock gas dilution. The kinetics of the emission lines of SiH? and

Luc Feitknecht; Johannes Meier; Pedro Torres; Jerôme Zürcher; Arvind Shah

2002-01-01

171

Kinetic simulation of a hot spot formation in high-Z plasma  

NASA Astrophysics Data System (ADS)

The so-called "hot spots" formed in a plasma heated by lasers having transverse spatial modulations give rise to steep temperature gradients with the scale comparable to the electron-ion mean free path. This indicates that the nonlocal transport effects can be important. Both the spatial transport and non-uniform heating of electrons by strong laser field may cause significant deviation of the electron distribution function (EDF) from the Maxwellian [1,2]. To study inhomogeneous hot spot formation we deploy 1D2V Fokker-Planck code ALLA [3], which includes e-e and e-i collisions, ambipolar electric field, and inverse bremsstrahlung plasma heating. Unlike particle methods it's free of statistical fluctuations and allows more accurate resolution of the EDF tail that is important to study the reduction of the electron plasma wave damping. We present results of the kinetic simulations with hot spots of various shapes and intensities, as well as a comparison with the results for homogeneous plasma heating and analytical models for EDF in high Z-plasmas. [1] A.B.Langdon, Phys.Rev.Lett. 44, 575 (1980); [2] E.Fourkal, V.Yu.Bychenkov, W.Rozmus et al., Phys. Plasmas 8 (2) 550 (2001); [3] O.Batishchev et al., J.Plasma Phys. 61 (3) 347 (1999).

Batishchev, Oleg; Bychenkov, Valery; Rozmus, Wojciech

2001-06-01

172

A new dynamic fluid-kinetic model for plasma transport within the plasmaspheric plume  

NASA Astrophysics Data System (ADS)

A new dynamic fluid-kinetic (DyFk) model is proposed and developed for investigating the plasma transport from the plasmasphere to the dayside magnetopause through the plasmaspheric plume. This model treats a closed flux tube in a local sense, in contrast to the global sense. The flux tube is allowed to move both radially from near the Earth to the magnetopause, which may result in expansion in its volume, and azimuthally around the Earth. Plasma may flow along the flux tube. The numerical simulation model couples a truncated version of the field line interhemispheric plasma (FLIP) model at altitudes below 800 km and a generalized semi-kinetic (GSK) model above it with an overlapped boundary region in each of the hemispheres. A self-consistently treatment of the ionospheric losses and production with possible heat sinks couples to a kinetic treatment of the multiple ion species (O+/ H+/ He+) and electrons in the plasmasphere. This model includes the effects of the convection of the plasmaspheric flux tube, parallel electric field, magnetic mirror force, centrifugal force, changing ionospheric conditions, Coulomb and ion-neutral collisions, and anisotropic temperatures, as well as the wave-particle interaction. The preliminary simulation results of the multi-species ion transport within a plasmaspheric plume will be presented.

Wang, Y.; Tu, J.; Song, P.

2011-12-01

173

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

SciTech Connect

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

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

2009-04-23

174

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

175

Energetic cooling below the BEC transition: a quantum kinetic description within the Bogoliubov approximation  

NASA Astrophysics Data System (ADS)

The dynamics of Bose–Einstein condensation in a three-dimensional harmonic trap is studied explicitly including the Bogoliubov approximation for temperatures below the critical one. To model the evolution towards equilibrium at each cooling step, we derive quantum kinetic equations that describe the dynamics of the gas for temperatures above and below the transition temperature. These equations, valid in the Born and Markov approximations, consider the essential role of the chemical potential as the main parameter that signals the transition. The kinetic equation that describes the growth of the condensate below the transition temperature is derived within the Bogoliubov approximation. To illustrate our results we propose an energetic cooling protocol and simulate the whole sequence of the formation of a condensate.

Camacho-Guardian, A.; Mendoza-López, M.; Romero-Rochín, V.; Paredes, R.

2014-11-01

176

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

SciTech Connect

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

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

2010-12-10

177

Nonlinear Interaction of 3D Kinetic Alfvén Waves and Ion Acoustic Waves in Solar Wind Plasmas  

NASA Astrophysics Data System (ADS)

We have investigated the nonlinear interaction between a 3D kinetic Alfvén wave (KAW) and an ion acoustic wave (IAW) in solar wind plasmas. A set of dimensionless equations was developed that describes the pump KAW perturbed by a low-frequency ion acoustic wave. The dependence of the growth rate of the modulational instability on the perturbation wave number was studied. We simulated numerically the dynamical equation of KAW with a pseudo-spectral method, taking ponderomotive nonlinearity into account. The 3D KAW itself propagates in the form of a vortex beam in a magnetised plasma, which manifests the presence of orbital angular momentum of the wave eigenmodes. We discuss the evolution of these vortex structures. Our results reveal that the Kolmogorov scaling is followed by a steeper scaling of power spectra, which is consistent with the solar wind observations by the Cluster spacecraft. We discuss the relevance of our investigation for solar wind plasmas.

Yadav, N.; Sharma, R. P.

2014-05-01

178

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

SciTech Connect

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

SIMAKOV, ANDERI N. [Los Alamos National Laboratory

2007-02-08

179

Eprinomectin in dairy zebu Gobra cattle (Bos indicus): plasma kinetics and excretion in milk.  

PubMed

The pharmacokinetics and mammary excretion of eprinomectin were determined in zebu Gobra following topical administration of 0.5 mg kg(-1). The kinetics of plasma and milk was analysed using a one-compartment model. The maximum plasma concentration of 8.83+/-2.15 ng ml(-1) occurred 1.30 days post-administration. The area under the plasma concentration-time curve was 30.63+/-5.56 ng day(-1) ml(-1) and the mean residence time was 3.38+/-0.60 days. Eprinomectin was detected in milk at the first sampling time and thereafter for at least 8 days. The systemic availability of eprinomectin was significantly lower than that for other breeds of cattle. Comparison of the milk and plasma data demonstrated the parallel disposition of the drug in the milk and plasma with a milk/plasma ratio of 0.094. The very low extent of mammary excretion supports the permitted use of eprinomectin in lactating zebu Gobra. PMID:16416124

Bengone-Ndong, T; Ba, M A; Kane, Y; Sané, I; Sutra, J F; Alvinerie, M

2006-05-01

180

Kinetic description of ionospheric dynamics in the three-fluid approximation  

NASA Technical Reports Server (NTRS)

Conservation equations are developed in the three-fluid approximation for general application problems of ionospheric dynamics in the altitude region 90 km to 800 km for all geographic locations. These equations are applied to a detailed study of auroral E region neutral winds and their relationship to ionospheric plasma motions.

Comfort, R. H.

1975-01-01

181

Kinetic description of optimal control problems and applications to opinion consensus  

E-print Network

In this paper an optimal control problem for a large system of interacting agents is considered using a kinetic perspective. As a prototype model we analyze a microscopic model of opinion formation under constraints. For this problem a Boltzmann-type equation based on a model predictive control formulation is introduced and discussed. In particular, the receding horizon strategy permits to embed the minimization of suitable cost functional into binary particle interactions. The corresponding Fokker-Planck asymptotic limit is also derived and explicit expressions of stationary solutions are given. Several numerical results showing the robustness of the present approach are finally reported.

Albi, Giacomo; Pareschi, Lorenzo

2014-01-01

182

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

SciTech Connect

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

Yu Lin; Xueyi Wang; Liu Chen; Zhihong Lin

2009-08-11

183

Plasma kinetics of an artificial emulsion resembling chylomicrons in patients with chronic lymphocytic leukemia.  

PubMed

Chylomicrons are the lipoproteins that transport dietary lipids in the blood. Although neoplastic diseases are often accompanied by alterations in lipid metabolism, chylomicrons are scarcely explored in cancer, despite their importance for the body's energy supply. Moreover, no data are available regarding chylomicron metabolism in chronic lymphocytic leukemia (CLL). Chylomicron metabolism in the bloodstream consists of lipolysis by lipoprotein lipase and uptake of remnants by the liver and is difficult to assess in the human body. Among the methods to evaluate this pathway, the determination of the plasma kinetics of triglyceride-rich emulsions that mimic chylomicrons is a practical and straightforward approach. A double-labeled chylomicron-resembling emulsion was injected into 10 patients with CLL and into 11 normolipidemic healthy subjects. The plasma kinetic curves of the emulsion 3H-triglyceride and 14Ccholesteryl ester were determined in plasma samples collected over 30 min. The fractional clearance rate (FCR) of triglycerides in CLL was not changed compared with controls. The FCR of cholesteryl esters was also no different from controls. These results indicate that chylomicron lipolysis and remnant removal are not affected in CLL. PMID:11195006

Sakashita, A M; Bydlowski, S P; Chamone, D A; Maranhão, R C

2000-12-01

184

Microstructural prototyping of ceramics by kinetic engineering: applications of spark plasma sintering.  

PubMed

The significance of kinetics on the development of microstructures in connection with sintering of ceramics is well recognized. In practice, however, it still remains a challenge to prepare designed microstructures via engineering the sintering kinetics because of an insufficient understanding of the different operative mechanisms that are in many cases overlapping. In this article the kinetic issues involved in sintering are described and discussed with respect to their potential for prototyping microstructures that yield desired properties. By exploiting and mastering the differences present in the kinetics of grain sliding, densification, chemical reactions, and grain growth, respectively, we have established processing principles for producing bulk ceramics with microstructures consisting of nano-sized grains, aligned grains, and/or non-equilibrium-phase constitutions, and for achieving radically improved superplasticity in brittle ceramics. Although the studies quoted in this article were mainly carried out by spark plasma sintering, more general implications of them are expected, including efficient particle sliding, deformation-induced dynamic ripening, superplastic deformation-induced dynamic ripening, and non-equilibrium integration. PMID:15889404

Shen, Zhijian; Nygren, Mats

2005-01-01

185

Regions of kinetic geodesic acoustic modes and streamers in JIPPT-IIU tokamak plasmas  

NASA Astrophysics Data System (ADS)

The radial extent of kinetic geodesic acoustic modes (KGAMs) and streamers is measured using a heavy ion beam probe. Intense KGAM oscillations are observed in the core region of a low-density ohmic (OH) plasma where Te ? Ti and outside this region, streamers characterized by steepening fronts are observed. The radial profile of plasma density stays flat in the region of the streamers, showing a rise in the plasma density in two regions, one at the scrape-off layer and the other in the core region during the radial scan of sample volumes. Intense (up to e?/kTe ˜ 0.1) and broad GAM oscillations (?f/f ˜ 0.5) are observed in the r < ap/2 region of tokamak plasmas. GAM oscillations and streamers are strongly reduced in the heated phase. In addition, the radial profile of the spectra of GAM in the heated phase is very different from that of a low-density OH plasma. The streamers and the two-step rise in the density radial profile disappear in the heated phase.

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

2012-06-01

186

Experimental observation of the transition from nonlocal to local electron kinetics in inductively coupled plasmas  

SciTech Connect

The transition from nonlocal to local kinetics was observed through the spatially resolved measurements of electron energy distribution functions in inductively coupled plasmas. As gas pressures increase, the spatial profiles of the effective electron temperatures (T{sub eff}) from the electron energy distribution functions changed dramatically from hollow shapes to flat shapes. With further increases in gas pressures, the T{sub eff} had saddle-shaped profiles with the highest T{sub eff} in the vicinity of an antenna coil. These changes in the radial profiles of the T{sub eff} show a transition of the electron kinetics from nonlocal to local regimes. This transition occurred when the electron energy relaxation lengths became smaller than the antenna half size.

Lee, Hyo-Chang; Lee, Min-Hyong; Chung, Chin-Wook [Department of Electrical Engineering, Hanyang University, 17 Haengdang-dong, Seongdong-gu, Seoul 133-791 (Korea, Republic of)

2010-01-25

187

Self-consistent nonlinear kinetic simulations of the anomalous Doppler instability of suprathermal electrons in plasmas  

SciTech Connect

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

188

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

SciTech Connect

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

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

1985-07-01

189

Stability of the kinetic Alfven wave in a current-less plasma  

NASA Astrophysics Data System (ADS)

The two potential theory of Hasegawa has been used to derive the dispersion relation for the kinetic Alfven wave (KAW) in a plasma composed of hydrogen, oxygen and electrons. All three components have been modeled by ring distributions (obtained by subtracting two Maxwellian distributions with different temperatures) with the hydrogen and electrons drifting, respectively, with velocities V_{dH} and V_{de}. For the most general case, the dispersion equation is a polynomial equation of order five; it reduces to a relation which supports only one mode when V_{dH}=0. For typical parameters at comet Halley, we find that both V_{dH} and V_{de} can drive the wave unstable; the KAW is thus driven unstable in a current-less plasma. Such an instability was found for the ion acoustic wave by Vranjes et al.

Abraham, Noble P.; C, Venugopal; Sebastian, Sijo; Renuka, G.; Balan, Nanan; Sreekala, G.

190

Kinetic solution to the Mach probe problem in transversely flowing strongly magnetized plasmas  

NASA Astrophysics Data System (ADS)

The kinetic equation governing a strongly magnetized transverse plasma flow past a convex ion-collecting object is solved numerically for arbitrary ion to electron temperature ratio ? . The approximation of isothermal ions adopted in a recent fluid treatment of the same plasma model [I. H. Hutchinson, Phys. Rev. Lett. 101, 035004 (2008)] is shown to have no more than a small quantitative effect on the solution. In particular, the ion flux density to an elementary portion of the object still only depends on the local surface orientation. We rigorously show that the solution can be condensed in a single “calibration factor” Mc , function of ? only, enabling Mach probe measurements of parallel and perpendicular flows by probing flux ratios at two different angles in the plane of flow and magnetic field.

Patacchini, Leonardo; Hutchinson, Ian H.

2009-09-01

191

The role of electron scattering with vibrationally excited nitrogen molecules on non-equilibrium plasma kinetics  

SciTech Connect

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

192

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

193

Predicting individual responses to pravastatin using a physiologically based kinetic model for plasma cholesterol concentrations.  

PubMed

We used a previously developed physiologically based kinetic (PBK) model to analyze the effect of individual variations in metabolism and transport of cholesterol on pravastatin response. The PBK model is based on kinetic expressions for 21 reactions that interconnect eight different body cholesterol pools including plasma HDL and non-HDL cholesterol. A pravastatin pharmacokinetic model was constructed and the simulated hepatic pravastatin concentration was used to modulate the reaction rate constant of hepatic free cholesterol synthesis in the PBK model. The integrated model was then used to predict plasma cholesterol concentrations as a function of pravastatin dose. Predicted versus observed values at 40 mg/d pravastatin were 15 versus 22 % reduction of total plasma cholesterol, and 10 versus 5.6 % increase of HDL cholesterol. A population of 7,609 virtual subjects was generated using a Monte Carlo approach, and the response to a 40 mg/d pravastatin dose was simulated for each subject. Linear regression analysis of the pravastatin response in this virtual population showed that hepatic and peripheral cholesterol synthesis had the largest regression coefficients for the non-HDL-C response. However, the modeling also showed that these processes alone did not suffice to predict non-HDL-C response to pravastatin, contradicting the hypothesis that people with high cholesterol synthesis rates are good statin responders. In conclusion, we have developed a PBK model that is able to accurately describe the effect of pravastatin treatment on plasma cholesterol concentrations and can be used to provide insight in the mechanisms behind individual variation in statin response. PMID:25106950

van de Pas, Niek C A; Rullmann, Johan A C; Woutersen, Ruud A; van Ommen, Ben; Rietjens, Ivonne M C M; de Graaf, Albert A

2014-08-01

194

Transmission spectroscopy and atomic kinetics of neon photoionized plasma experiments at Z  

NASA Astrophysics Data System (ADS)

We discuss a series of experiments performed at the Z facility in which photoionized plasmas were produced by driving a neon-filled gas cell with the intense x-ray flux emitted at the collapse of a z-pinch. The broad-band radiation flux from the z-pinch is used to both create the neon photoionised plasma and provide a source of backlighting photons to study the atomic kinetics through K-shell transmission spectroscopy. The plasma is contained in cm-scale gas cell and the filling pressure is carefully monitored in situ all the way to shot time since it is the particle number density diagnostic of the plasma. Time-integrated and gated transmission spectra are recorded with a TREX spectrometer equipped with two KAP elliptically-bent crystals and a set of slits to record up to six spatially-resolved spectra per crystal in the same shot. The transmission data shows line absorption transitions in several ionization stages of neon. Detailed modeling calculations are used to interpret the data.

Mancini, R.; Hall, I.; Durmaz, T.; Bailey, J.; Rochau, G.; Cohen, D.; Foord, M.; Heeter, R.

2010-11-01

195

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

196

Vlasov-Maxwell kinetic simulations of radio-frequency-driven ion flows in magnetized plasmas.  

PubMed

The generation of a coherent ion flow due to the injection in a plasma of a purely electrostatic wave of finite amplitude, propagating at right angle with the ambient uniform magnetic field, is investigated making use of a kinetic code which solves the fully nonlinear Vlasov equations for electrons and ions, coupled with the Maxwell equations, in one spatial and two velocity dimensions. A uniformly magnetized slab plasma is considered. The wave frequency is assumed in the range of the fourth harmonic of the ion cyclotron frequency, and the wave vector is chosen in order to model the propagation of an ion Bernstein wave. The computation of the first-order moment of the ion distribution function shows that indeed a quasistationary transverse average ion drift velocity is produced. The time evolution of the ion distribution function undergoes a "resonant" interaction of Cherenkov type, even if the plasma ions are magnetized (omega(ci)/omega(pi) approximately 0.5). During the wave-plasma interaction, the electron distribution function remains Gaussian-like, while increasing its energy content. PMID:12636820

Marchetto, Chiara; Califano, Francesco; Lontano, Maurizio

2003-02-01

197

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

E-print Network

The hybrid kinetic model supports comprehensive simulation of the interaction between different spatial and energetic elements of the Europa moon-magnetosphere system with respect a 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 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 backgr...

Lipatov, A S; Paterson, W R; Sittler, E C; Hartle, R E; Simpson, D G

2012-01-01

198

Loss Kinetics of Carbon Atoms in Diamond Deposition Employing Low-Pressure Inductively Coupled Plasma  

NASA Astrophysics Data System (ADS)

Nanocrystalline diamond has been successfully synthesized in low-pressure CO/H_2/CH4 inductively coupled plasmas (ICPs) in our previous study. For a better understanding of the mechanism of diamond film deposition, vacuum ultraviolet absorption spectroscopy with a carbon hollow cathode lamp was applied to the measurement of decay rate of C-atom and was employed to determine the diffusion constant in the afterglow of low-pressure CO and CO/H2 ICPs. The transition line used for the measurement was 2p3s ^3P_2-2p^2 ^3P2 at 165.7 nm for measurement. The dependence of the decay rate of C-atoms density on pressure revealed that C-atoms were dominantly lost at the surface rather than in gas phase in both CO and CO/H2 plasmas. However, in the case of CO/H2 plasma at higher pressures over 6 Pa, C-atoms were lost in the gas phase reaction as well as at the surface. The diffusion constants of C-atom in both CO and CO/H2 plasmas were estimated to be 3.1× 10^4 cm^2Pas-1 and 3.7× 10^4 cm^2Pas-1, respectively. These values are higher than that of the reported diffusion constant (8.7× 10^3 cm^2Pas-1) of CF2 in DC pulsed CF4 discharge plasma. The loss kinetics of C-atoms in plasmas are also discussed.

Ito, Haruhiko; Teii, Kungen; Funakoshi, Hikaru; Hori, Masaru; Goto, Toshio; Ito, Masafumi; Tekeo, Takashi

2000-10-01

199

A plasma concentration of ?-ketoglutarate influences the kinetic interaction of ligands with organic anion transporter 1.  

PubMed

The purpose of the present study was to determine whether a physiologic plasma concentration of ?-ketoglutarate (?KG) influences the kinetic interaction of ligands with organic anion transporter 1 (OAT1). The effect of extracellular ?KG on the kinetics of para-aminohippurate (PAH) and cidofovir transport was examined along with its effect on the potency of 10 drugs in five different classes (uricosuric, nonsteroidal anti-inflammatories, loop diuretics, angiotensin II receptor antagonists, and ?-lactam antibiotics) to inhibit OAT1 expressed in Chinese hamster ovary cells. Extracellular ?KG competitively inhibited PAH and cidofovir transport with Ki values (?5 ?M) approximating its unbound plasma concentration (determined by equilibrium dialysis). When PAH was the substrate, extracellular ?KG (5 ?M) significantly increased IC50 values for some inhibitors (up to 4-fold), such as probenecid, but not for others (an inhibitor-dependent effect). For some inhibitors, a significant increase in IC50 value was observed when cidofovir was the substrate, but not PAH (a substrate-dependent effect). A significant increase in IC50 value was also observed for inhibition of PAH transport by probenecid in renal basolateral membrane vesicles (5.2-fold). The substrate- and inhibitor-dependent effect of extracellular ?KG on ligand interactions with OAT1 highlights the complexity of the OAT1 ligand-binding surface. The effect of extracellular ?KG on the potency of OAT1 inhibition should be considered when assessing drug-drug interaction potential at the transporter. PMID:24770989

Ingraham, Leslie; Li, Mansong; Renfro, J Larry; Parker, Sonda; Vapurcuyan, Arpine; Hanna, Imad; Pelis, Ryan M

2014-07-01

200

Plasma Physics for Nuclear Fusion  

Microsoft Academic Search

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

K. Miyamoto; Robert L. Dewar

1980-01-01

201

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

202

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

203

One-to-one direct modeling of experiments and astrophysical scenarios: pushing the envelope on kinetic plasma simulations  

E-print Network

There are many astrophysical and laboratory scenarios where kinetic effects play an important role. These range from astrophysical shocks and plasma shell collisions, to high intensity laser-plasma interactions, with applications to fast ignition and particle acceleration. Further understanding of these scenarios requires detailed numerical modelling, but fully relativistic kinetic codes are computationally intensive, and the goal of one-to-one direct modelling of such scenarios and direct comparison with experimental results is still difficult to achieve. In this paper we discuss the issues involved in performing kinetic plasma simulations of experiments and astrophysical scenarios, focusing on what needs to be achieved for one-to-one direct modeling, and the computational requirements involved. We focus on code efficiency and new algorithms, specifically on parallel scalability issues, namely on dynamic load balancing, and on high-order interpolation and boosted frame simulations to optimize simulation perf...

Fonseca, R A; Silva, L O; Tonge, J W; Tsung, F S; Mori, W B

2008-01-01

204

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

205

Mean free paths, viscosity, and the limitations of perfect fluid hydrodynamics in the description of the quark-gluon plasma  

SciTech Connect

The author discusses the applicability of a hydrodynamic description of high energy hadronic collisions. The author reviews the results of recent computations of the mean free paths of quarks and gluons in a quark-gluon plasma, and the corresponding results for viscous coefficients. These quantities are employed to evaluate the limits to the application of perfect fluid hydrodynamics as a description of time evolution of matter produced in various hadronic collisions. 22 references.

McLerran, L.

1984-11-01

206

Velocity Fourier transform solution of a model collision operator. [to obtain kinetic equation for waves in magnetized plasmas  

NASA Technical Reports Server (NTRS)

A simpler technique than those introduced by Lenard and Bernstein (1958), and Dougherty (1964) is employed to obtain the perturbed species density from a specified kinetic equation for a plasma in a given uniform magnetic field. The technique is a generalization of the velocity-Fourier transform method employed by Karpman (1967) for B sub 0 identical to zero, and relies on the fact that in transform space the model collision operator, used to obtain the kinetic equation for waves in a magnetized plasma, contains only first derivatives. The technique is illustrated by evaluating the perturbed density of an arbitrary species.

Catto, P. J.

1979-01-01

207

Measurements of the gas-kinetic pressure in plasma flows emerging from a micropinch discharge by means of laser interferometry  

NASA Astrophysics Data System (ADS)

A new method for measuring the gas-kinetic pressure in pulsed plasma flows is developed in which an acoustic line in the form of a thin rod built in the optical scheme of a laser interferometer is used as a detector. The time evolution of the gas-kinetic pressure in particle flows emerging from a micropinch discharge (a low-inductance vacuum spark) was studied. Due to the wide dynamic range of the method (˜105), it can be applied in various plasma devices with a wide range of parameters.

Kuznetsov, A. P.; Byalkovskii, O. A.; Gubskii, K. L.; Kozin, G. I.; Protsenko, E. D.; Dodulad, E. I.; Savjolov, A. S.

2014-04-01

208

Comprehensive kinetic analysis of the plasma-wall transition layer in a strongly tilted magnetic field  

NASA Astrophysics Data System (ADS)

The magnetized plasma-wall transition (MPWT) layer at the presence of the obliquity of the magnetic field to the wall consists of three sub-layers: the Debye sheath (DS), the magnetic pre-sheath (MPS), and the collisional pre-sheath (CPS) with characteristic lengths ?D (electron Debye length), ?i (ion gyro-radius), and ? (the smallest relevant collision length), respectively. Tokamak plasmas are usually assumed to have the ordering ? D ? ? i ? ? , when the above-mentioned sub-layers can be distinctly distinguished. In the limits of ? D m ( ? D / ? i ) ? 0 and ? m c ( ? i / ? ) ? 0 ("asymptotic three-scale (A3S) limits"), these sub-layers are precisely defined. Using the smallness of the tilting angle of the magnetic field to the wall, the ion distribution functions are found for three sub-regions in the analytic form. The equations and characteristic length-scales governing the transition (intermediate) regions between the neighboring sub-layers (CPS - MPS and MPS - DS) are derived, allowing to avoid the singularities arising from the ? D m ? 0 and ? m c ? 0 approximations. The MPS entrance and the related kinetic form of the Bohm-Chodura condition are successfully defined for the first time. At the DS entrance, the Bohm condition maintains its usual form. The results encourage further study and understanding of physics of the MPWT layers in the modern plasma facilities.

Tskhakaya, D. D.; Kos, L.

2014-10-01

209

Nonlinear coupling of lower hybrid waves to the kinetic low-frequency plasma response in the auroral ionosphere  

NASA Astrophysics Data System (ADS)

A hybrid kinetic-fluid model is developed which is relevant to lower hybrid spikelets observed in the topside auroral ionosphere [Vago et al., 1992; Eriksson et al., 1994]. In contrast to previous fluid models [Shapiro et al., 1995; Tam and Chang, 1995; Seyler, 1994; Shapiro et al., 1993] our linear low frequency plasma response is magnetized and kinetic. Fluid theory is used to incorporate the nonlinear wave coupling. Performing a linear stability analysis, we calculate the growth rate for the modulational instability, driven by a lower hybrid wave pump. We find that both the magnetic and kinetic effects inhibit the modulational instability.

Sanbonmatsu, K. Y.; Goldman, M. V.; Newman, D. L.

210

Effects of He and Ar ion kinetic energies in protection of organosilicate glass from O{sub 2} plasma damage  

SciTech Connect

In-situ x-ray photoelectron spectroscopy (XPS) and ex-situ Fourier transform infrared studies of He plasma and Ar{sup +} ion bombardment pretreatments of organosilicate glass demonstrate that such pretreatments inhibit subsequent O{sub 2} plasma-induced carbon loss by forming a SiO{sub 2}-like damaged overlayer, and that the degree of protection correlates directly with increased ion kinetic energies, but not with the thickness of the SiO{sub 2} overlayer. This thickness is observed by XPS to be roughly constant and <1 nm regardless of ion energies involved. The data indicate that ion kinetic energies are an important parameter in protective noble gas plasma pretreatments to inhibit O{sub 2} plasma-induced carbon loss.

Lee, Joe; Graves, David B. [Department of Chemical Engineering, University of California-Berkeley, Berkeley, California 94720 (United States); Kazi, Haseeb; Gaddam, Sneha; Kelber, Jeffry A. [Department of Chemistry and Center for Electronic Materials Processing and Integration, University of North Texas, Denton, Texas 76203 (United States)

2013-07-15

211

Selfconsistent Description of the He Plasma in an Axially Symmetric Hollow Cathode  

NASA Astrophysics Data System (ADS)

The radial variations of the electron properties, the excited atom densities and the electric field of a cylindrical helium hollow cathode discharge at pressures of some Torr and discharge currents of some mA have been theoretically investigated. An axially symmetric arrangement consisting of a central hollow cathode and two, symmetrically arranged anodes is considered which recently has been experimentally investigated. The studies refer to the plasma around the axial center where the axial inhomogeneity can be neglected. The radial variations of the electron properties and the excited atom densities have been determined by a coupled solution of the radial-dependent electron Boltzmann equation and the particle balance equations of the excited atoms. Based on a tensorial expansion of the electron velocity distribution function a multiterm approach has been developed for the solution of the electron Boltzmann equation. The radial profile of the strongly varying radial electric field is determined from the Poisson equation which is selfconsistently coupled with the electron and excited state kinetics and the ion particle and momentum balance equations. The results evidence a distinct nonlocal behavior of the electrons in the transition from the kathode fall to the negative glow. The profiles of higher excited atoms partly show pronounced minima in the center and strongly change with the pressure.

Sigeneger, F.; Winkler, R.

2001-10-01

212

Kinetic studies of plasma free fatty acid and triglyceride metabolism in man  

PubMed Central

Plasma transport of free fatty acids (FFA) and triglyceride fatty acids (TGFA) was studied in seven subjects with normal lipid metabolism, one case of total lipodystrophy, and one case of familial hyperlipemia (Type V). Studies were carried out after intravenous injection of radioactive FFA, of lipoproteins previously labeled in vitro in the triglyceride moiety, or both. Computer techniques were used to evaluate a series of multicompartmental models, and a general model is proposed that yields optimum fitting of experimental data for both FFA and TGFA. The results show that as much as 20-30% of FFA leaving the plasma compartment in normal subjects is transported to an exchanging extravascular pool and quickly reenters the plasma pool as FFA. The rate of irreversible delivery of FFA from plasma to tissues averaged 358 ?Eq/min in normals. The lipodystrophy patient, despite the virtual absence of adipose tissue (confirmed at autopsy), had a plasma FFA concentration and a total FFA transport, both more than twice normal. Total TGFA transport ranged from 25 to 81 ?Eq/min in four normal controls. The rate constant for TGFA turnover in the patient with Type V hyperlipemia was so small that total transport could not be quantified from the data available; the TGFA half-life was over 500 min. In two normal subjects given injections of autologous lipoproteins labeled in vitro with triolein-14C and simultaneously given oleic acid-3H, it was shown that the time course for the disappearance of the TGFA in the in vitro labeled samples conformed almost exactly to that of the physiologically labeled lipoprotein TGFA synthesized from injected FFA (as evidenced by the simultaneous fitting of both sets of data using the same multicompartmental model and the same rate constants). Radioactivity appeared in the plasma FFA fraction at a significant rate after injection of plasma labeled in vitro with TGFA. It was estimated that as much as 50% of the total TGFA transported underwent rapid and rather direct conversion to FFA in the two normal subjects studied this way. The kinetic data suggest that such conversion of TGFA to FFA was not preceded by any extensive dilution, such as would result from complete mixing with tissue triglyceride stores. Images PMID:5796365

Eaton, R. Philip; Berman, Mones; Steinberg, Daniel

1969-01-01

213

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

214

Kinetics of plasma particles and electron transport in the current-carrying plasma adjacent to an evaporating and electron emitting wall  

Microsoft Academic Search

The paper reviews the vaporization phenomena at a target heated by heat flux from an adjacent plasma in vacuum and in low-pressure discharges. The kinetics of a nonequilibrium layer and the direct and returned mass fluxes formed in the vicinity of the target are described. The mechanism of cathode vaporization taking into account cathode electron emission in vacuum arcs is

Isak I. Beilis

2006-01-01

215

"Intelligent" descriptions of microbial kinetics in finitely dispersed bioreactors: neural and cybernetic models for PHB biosynthesis by Ralstonia eutropha  

PubMed Central

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

216

Slow drift mirror kinetic instability at a finite electron temperature in a nonmaxwellian space plasma  

NASA Astrophysics Data System (ADS)

A slow drift mirror (SDM) instability has been analyzed in the scope of kinetic approximation, with accounting for the electron pressure for different particle distribution functions. The dependence of the SDM instability increment growth rate on the parameters of the anisotropic ? distribution with the loss cone, which is used to model real space plasma particle distributions, has been studied. An analysis indicated that the appearance of the loss cone in the ion distribution function results in a decrease in the SDM mode frequency, and an enhancement of the suprathermal tail (a decrease in ?) increases the SDM mode frequency as compared to the Maxwellian distribution. In other words, particle redistribution from the region of low velocities into that of high velocities results in an increase in the SDM mode frequency.

Feygin, F. Z.; Khabazin, Yu. G.

2014-11-01

217

Nonlinear interaction of 3D kinetic Alfvén wave and whistler wave in solar wind plasmas  

NASA Astrophysics Data System (ADS)

the present work, the nonlinear evolution of 3D kinetic Alfvén wave (KAW) has been investigated in solar wind plasmas. By taking the adiabatic response of background density the nonlinearity arises because of ponderomotive effects. The dynamical equations governing the dynamics of 3D KAW and whistler are obtained. We have performed the numerical simulation using pseudospectral method to study the evolution of the nonlinear localized structures of KAW in the solar wind at 1 AU. The interaction between 3D KAW and the amplification of weak whistler signal propagating in the localized structures of KAW has also been studied semi-analytically to have an insight of the localization process. The relevance of the present work to the solar wind turbulence is discussed.

Sharma, R. P.; Gaur, Nidhi

2014-09-01

218

Kinetic simulations and reduced modeling of longitudinal sideband instabilities in non-linear electron plasma waves  

NASA Astrophysics Data System (ADS)

Kinetic Vlasov simulations of one-dimensional finite amplitude Electron Plasma Waves are performed in a multi-wavelength long system. A systematic study of the most unstable linear sideband mode, in particular its growth rate ? and quasi- wavenumber ?k, is carried out by scanning the amplitude and wavenumber of the initial wave. Simulation results are successfully compared against numerical and analytical solutions to the reduced model by Kruer et al. [Phys. Rev. Lett. 23, 838 (1969)] for the Trapped Particle Instability (TPI). A model recently suggested by Dodin et al. [Phys. Rev. Lett. 110, 215006 (2013)], which in addition to the TPI accounts for the so-called Negative Mass Instability because of a more detailed representation of the trapped particle dynamics, is also studied and compared with simulations.

Brunner, S.; Berger, R. L.; Cohen, B. I.; Hausammann, L.; Valeo, E. J.

2014-10-01

219

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

SciTech Connect

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

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

2010-06-11

220

The derivation of model kinetic equation for gases and for plasmas  

E-print Network

A new form of the model collision operator for a Boltzmann gas of hard spheres and Coulomb plasma is derived. One-component and many-component systems are considered. The collision operator proposed takes properly into account the relaxation of the first 13 hydrodynamic moments. An expression for the intensity of the Langevin source in the model kinetic equation is obtained in the same approximation. A technique for reconstruction of the model collision integral based on a known expression for the model linearized operator is proposed. It is shown that, within our model, the collision integral does not contain a complicated exponential, common for the ellipsoidal statistical type models. Boltzmann's H-theorem is proved for our model.

Belyi, Viacheslav V

2014-01-01

221

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

SciTech Connect

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

John E. Krommes

2010-09-27

222

Fully kinetic simulations of magnetic reconnction in semi-collisional plasmas  

SciTech Connect

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

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

2009-01-01

223

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

224

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

SciTech Connect

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{sup ?} is obtained, which is in good agreement with efficiencies computed via full-wave simulations.

Ali Asgarian, M. [Physics Department, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of) [Physics Department, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of); Department of Electrical and Computer Engineering, Michigan State University, Michigan 48824-1226 (United States); Verboncoeur, J. P. [Department of Electrical and Computer Engineering, Michigan State University, Michigan 48824-1226 (United States)] [Department of Electrical and Computer Engineering, Michigan State University, Michigan 48824-1226 (United States); Parvazian, A. [Physics Department, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of)] [Physics Department, Isfahan University of Technology, Isfahan (Iran, Islamic Republic of); Trines, R. [STFC Rutherford Appleton Laboratory, Didcot (United Kingdom)] [STFC Rutherford Appleton Laboratory, Didcot (United Kingdom)

2013-10-15

225

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

NASA Astrophysics Data System (ADS)

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

Shihab, Mohammed; Brinkmann, Ralf Peter

2012-10-01

226

On a plasma kinetic model of a 3D solar corona and solar wind at the heliospheric sheet  

Microsoft Academic Search

The dynamical solar corona in 3D consists of transient type magnetic island elements and radial type magnetic flux rope structures in a heliospheric sheet. During the formation and relaxation these elements produce inductive electromagnetic fields where energetic particles are produced. We study the 3D corona formation in the kinetic approach and parametrize it like a hot current-carrying collisionless plasma with

V. M. Gubchenko; M. L. Khodachenko; H. K. Biernat; V. V. Zaitsev; H. O. Rucker

2004-01-01

227

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

E-print Network

1 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. In the first case, diesel fuel reacts with air while in the second case it reacts with diesel engine exhaust

Boyer, Edmond

228

Electron kinetics and non-Joule heating in near-collisionless inductively coupled plasmas V. I. Kolobov  

E-print Network

Electron kinetics and non-Joule heating in near-collisionless inductively coupled plasmas V. I; colli- sional Joule heating predominates. Heating at low pres- sures is due to a combined effect of Joule heating and collisionless heating, there is an important regime of what we call ``hy

Economou, Demetre J.

229

Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas  

E-print Network

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...

Andreev, Pavel A

2014-01-01

230

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

231

Numerical simulations to study kinetic Alfvén wave and whistler wave spectra in solar wind plasma  

NASA Astrophysics Data System (ADS)

The numerical simulations of the model equation governing the nonlinear evolution of kinetic Alfvén wave (KAW) in solar wind plasmas are performed. The nonlinear dynamical equation of KAW satisfies the modified nonlinear Schrödinger MNLS equation when the ponderomotive nonlinearity is incorporated in the KAW dynamics. The effect of Landau damping is taken into account in the KAW dynamics. The coherent (in the absence of Landau damping) and damped (with Landau damping) localized structures of pump KAW as a consequence of ponderomotive nonlinearity have been studied in the solar wind at 1 AU. A weak whistler signal propagating in these localized structures is amplified which leads to the development of its own coherent and damped localized structures. Magnetic field (KAW) and electric field (whistler wave) power spectra and their spectral indices are calculated. Our results reveal the change in spectral index because of the damping effect which has good agreement with the observations. These damped structures and steeper spectra may be one of the reasons responsible for the plasma heating and particles acceleration in solar wind.

Dwivedi, Navin Kumar; Sharma, R. P.; Batra, Karuna

2013-01-01

232

Study of kinetic Alfvén wave and whistler wave spectra and their implication in solar wind plasma  

NASA Astrophysics Data System (ADS)

This work presents the numerical simulation of the nonlinear evolution of kinetic Alfvén wave (KAW), in a parametric regime consistent with the solar wind plasmas. The nonlinear dynamical equation of KAW satisfies the modified nonlinear Schrödinger equation when incident pump KAW has a small perturbation. Numerical simulation has been done to solve this model equation when the ponderomotive nonlinearity is incorporated in the KAW dynamics. The localization of pump KAW as a consequence of ponderomotive nonlinearity has been studied in the solar wind at 1 AU. A weak whistler signal propagating in these localized structures is amplified and leads to the development of its own localized structures. Magnetic power spectra and spectral indices for KAW at different times are calculated. The magnetic field power spectra and spectral indices of whistler wave at different times are also calculated. The relevance of steepened KAW and whistler spectra to recent solar wind observations is also pointed out. These localized structures and steeper spectra can be responsible for the plasma heating and particles acceleration in solar wind.

Dwivedi, Navin Kumar; Batra, Karuna; Sharma, R. P.

2012-07-01

233

Absolute number density and kinetic analysis of the CF radical in pulsed CF4 + H2 radio-frequency plasmas  

NASA Astrophysics Data System (ADS)

The infrared tunable diode laser absorption spectroscopy (IR-TDLAS) experimental technique was employed to study CF radical kinetics in pulsed capacitively coupled CF4/H2 rf plasmas. In particular, the special data acquisition approach (so-called ‘burst mode’) was adapted and applied to monitor the absolute number density of CF with a temporal resolution of better than 1 ms. This enabled a proper kinetic analysis of the radical during both ‘plasma on’ and ‘plasma off’ phases. Thus, during the ‘plasma off’ phase, the CF species was found to be rapidly consumed, mostly in the reactor volume. Possible surface losses (sticking) of CF were shown to be of minor importance, and became notable only at total pressures lower than 10 Pa. During the ‘plasma on’ phase the CF concentration was measured to increase rapidly, reach a maximum and then decrease to its steady-state value. The observed overshoot in the CF density trace was shown to correlate with the corresponding decay of the C2F4 species also measured in the ‘plasma on’ phase. The electron impact fragmentation of C2F4 was supposed to contribute significantly to the effective production of CF at the beginning of the ‘plasma on’ phase, which might have caused the observed overshoots.

Stepanov, S.; Meichsner, J.

2012-04-01

234

Lagrangian and Hamiltonian Formulation of Plasma Problems.  

National Technical Information Service (NTIS)

A systematic formulation of existing theories for classical plasma systems by use of Hamilton's variational principle is presented at the microscopic, kinetic and fluid-model levels of description. Both the Lagrangian and Hamiltonian functions are given f...

G. C. Georges

1969-01-01

235

Kinetic theory of current and density drift instabilities with weak charged-neutral collisions. [in space plasmas  

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

236

Phase mixing of shear Alfven waves as a new mechanism for electron acceleration in collisionless, kinetic plasmas  

E-print Network

Particle-In-Cell (kinetic) simulations of shear Alfv\\'en wave interaction with one dimensional, across the uniform magnetic field, density inhomogeneity (phase mixing) in collisionless plasma were performed for the first time. As a result a new electron acceleration mechanism is discovered. Progressive distortion of Alfv\\'en wave front, due to the differences in local Alfv\\'en speed, generates nearly parallel to the magnetic field electrostatic fields, which accelerate electrons via Landau damping. Surprisingly, amplitude decay law in the inhomogeneous regions, in the kinetic regime, is the same as in the MHD approximation described by Heyvaerts and Priest (1983).

David Tsiklauri; Jun-Ichi Sakai; Shinji Saito

2004-09-22

237

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

NASA Astrophysics Data System (ADS)

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.

2014-05-01

238

A non-Maxwellian kinetic approach for charging of dust particles in discharge plasmas  

NASA Astrophysics Data System (ADS)

Nanoparticle charging in a capacitively coupled radio frequency discharge in argon is studied using a particle in cell Monte Carlo collisions method. The plasma parameters and dust potential were calculated self-consistently for different unmovable dust profiles. A new method for definition of the dust floating potential is proposed, based on the information about electron and ion energy distribution functions, obtained during the kinetic simulations. This approach provides an accurate balance of the electron and ion currents on the dust particle surface and allows us to precisely calculate the dust floating potential. A comparison of the obtained floating potentials with the results of the traditional orbital motion limit (OML) theory shows that in the presence of the ion resonant charge exchange collisions, even when the OML approximation is valid, its results are correct only in the region of a weak electric field, where the ion drift velocity is much smaller than the thermal one. With increasing ion drift velocity, the absolute value of the calculated dust potential becomes significantly smaller than the theory predicts. This is explained by a non-Maxwellian shape of the ion energy distribution function for the case of fast ion drift.

Alexandrov, A. L.; Schweigert, I. V.; Peeters, F. M.

2008-09-01

239

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

240

Super-thermal particles in hot plasmas—Kinetic models, numerical solution strategies, and comparison to tokamak experiments  

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

241

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

SciTech Connect

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

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

2012-10-15

242

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

243

Kinetic and thermodynamic properties of a convecting plasma in a two-dimensional dipole field  

NASA Technical Reports Server (NTRS)

Charged particle guiding center motion is considered in the magnetic field of a two-dimensional ('line') dipole on which is superimposed a small, static, perpendicular electric field. The parallel equation of motion is that of a simple harmonic oscillator for cos theta, the cosine of magnetic colatitude theta. Equations for the perpendicular electric and magnetic drifts are derived as well as their bounce-averaged forms. The latter are solved to yield a bounce-averaged guiding center trajectory, which is the same as that obtained from conversation of magnetic moment mu, longitudinal invariant J, and total (kinetic plus electrostatic) energy K. The algebraic simplicity of the trajectory equations is also manifest in the forms of the invariants. An interesting result is that guiding centers drift in such a way that they preserve the values of their equatorial pitch angles and (equivalently) mirror latitudes. The most general Maxwellian form of the equilibrium one-particle distribution function f is constructed from the invariants, and spatially varying density and pressure moments, parallel and perpendicular to the magnetic field, are identified. Much of the paper deals with the more restricted problem in which f is specified as a bi-Maxwellian over a straight line of finite length in the equatorial plane of the dipole and perpendicular to field lines. This might be thought of as specifying a cross-tail ion injection source; our formalism then describes the subsequent spatial development. The distribution away from the source is a scaled bi-Maxwellian but one that is cut off at large and small kinetic energies, which depend on position. Density and pressure components are reduced from the values they would have if the total content of individual flux tubes convected intact. The equatorial and meridional variations of density and pressure components are examined and compared systematically for the isotropic and highly anisotropic situations. There appears to be little qualitative difference due to anisotropy. An anisotropy measure is defined, and its spatial variation determined as a signature of possible MHD instability. Extreme values are found, larger than at the source, but the plasma beta in such regions is probably so low as to render the effect inconsequential energetically. Finally, the possible consequence of 'nonadia- batic' pressure profiles on electrostatic interchanges is considered, and a boundary delineating stabilizing and destabilizing regions determined.

Huang, T. S.; Birmingham, T. J.

1994-01-01

244

Hydrodynamic and kinetic models for spin-1/2 electron-positron quantum plasmas: Annihilation interaction, helicity conservation, and wave dispersion in magnetized plasmas  

E-print Network

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

245

Kinetic description of electron-proton instability in high-intensity proton linacs and storage rings based on the Vlasov-Maxwell equations  

NASA Astrophysics Data System (ADS)

The present analysis makes use of the Vlasov-Maxwell equations to develop a fully kinetic description of the electrostatic, electron-ion two-stream instability driven by the directed axial motion of a high-intensity ion beam propagating in the z direction with average axial momentum ?bmb?bc through a stationary population of background electrons. The ion beam has characteristic radius rb and is treated as continuous in the z direction, and the applied transverse focusing force on the beam ions is modeled by Fbfoc=-?b mb?02?b x? in the smooth-focusing approximation. Here, ?0?b=const is the effective betatron frequency associated with the applied focusing field, x? is the transverse displacement from the beam axis, \\(?b-1\\)mbc2 is the ion kinetic energy, and Vb=?bc is the average axial velocity, where ?b=\\(1-?2b \\)-1/2. Furthermore, the ion motion in the beam frame is assumed to be nonrelativistic, and the electron motion in the laboratory frame is assumed to be nonrelativistic. The ion charge and number density are denoted by +Zbe and nb, and the electron charge and number density by -e and ne. For Zbnb>ne, the electrons are electrostatically confined in the transverse direction by the space-charge potential ? produced by the excess ion charge. The equilibrium and stability analysis retains the effects of finite radial geometry transverse to the beam propagation direction, including the presence of a perfectly conducting cylindrical wall located at radius r=rw. In addition, the analysis assumes perturbations with long axial wavelength, k2zr2b<<1, and sufficiently high frequency that \\|?/kz\\|>>vTez and \\|?/kz-Vb\\|>>vTbz, where vTez and vTbz are the characteristic axial thermal speeds of the background electrons and beam ions. In this regime, Landau damping (in axial velocity space vz) by resonant ions and electrons is negligibly small. We introduce the ion plasma frequency squared defined by ?^2pb =4?n^bZ2be2/?bmb, and the fractional charge neutralization defined by f=n^e/Zb n^b, where n^b and n^e are the characteristic ion and electron densities. The equilibrium and stability analysis is carried out for arbitrary normalized beam intensity ?^2pb /?02?b, and arbitrary fractional charge neutralization f, consistent with radial confinement of the beam particles. For the moderately high beam intensities envisioned in the proton linacs and storage rings for the Accelerator for Production of Tritium and the Spallation Neutron Source, the normalized beam intensity is typically ?^2pb /?02?b<~ 0.1. For heavy ion fusion applications, however, the transverse beam emittance is very small, and the space-charge-dominated beam intensity is much larger, with ?^2pb /?02?b<~ 2?2b. The stability analysis shows that the instability growth rate Im? increases with increasing normalized beam intensity ?^2pb /?02?b and increasing fractional charge neutralization f. In addition, the instability is strongest (largest growth rate) for perturbations with azimuthal mode number l=1, corresponding to a simple (dipole) transverse displacement of the beam ions and the background electrons. For the case of overlapping step-function density profiles for the beam ions and background electrons, corresponding to monoenergetic ions and electrons, a key result is that there is no threshold in beam intensity ?^2pb /?02?b or fractional charge neutralization f for the onset of instability. Finally, for the case of continuously varying density profiles with parabolic profile shape, a semiquantitative estimate is made of the effects of the corresponding spread in (depressed) betatron frequency on stability behavior, including an estimate of the instability threshold for the case of weak density nonuniformity.

Davidson, Ronald C.; Qin, Hong; Stoltz, Peter H.; Wang, Tai-Sen F.

1999-05-01

246

Kinetics of organic molecules in pulsed plasmas of nitrogen or N2/O2 mixtures at near atmospheric pressure  

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

247

Factors affecting ion kinetic temperature, number density, and containment time in the NASA Lewis bumpy-torus plasma  

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

248

A Kinetic-fluid Model  

SciTech Connect

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

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

1998-07-10

249

A new approach to the application of the classic methods of physicochemical kinetics in the analysis of the efficiency of plasma technology of coal gasification  

SciTech Connect

This work is devoted to the problem of improving the efficiency of new plasma technologies of coal combustion that have minimum negative environmental impact. In particular, the authors consider a general method of formulating and solving the inverse kinetic problem to elucidate advantages of plasma gasification.

Karpenko, E.I.; Devyatov, B.N. [Kutateladze Inst. of Thermal Physics, Novosibirsk (Russian Federation)

1995-07-01

250

New approach to application of classic methods of physical and chemical kinetics to analysis of efficiency of plasma technology of coal gasification  

SciTech Connect

This report is devoted to the problem of increase of the efficiency of new plasma technology of coal burning providing minimum negative influence to the environment. In particular, common method of statement and solution of inverse kinetic problem allowing to show plasma gasification advantages is represented here.

Carpenko, E.I.; Devaytov, B.N.; Zhukov, M.F. [Institute of Thermophysics, Novosibirsk (Russian Federation)

1995-07-01

251

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

E-print Network

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

252

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

253

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

254

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

SciTech Connect

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

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

2010-02-15

255

Kinetic Space Weather: Toward a Global Hybrid Model of the Polar Ionosphere-Lower Magnetosphere Plasma Transport  

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

256

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

E-print Network

of the laser-plasma interaction. Three-wave like codes are employed for modeling; incorpo- rating nonlinear water bag extension of the theory for application to autoresonant plasma waves in nonuniform plasmas is a resonant three-wave interaction in which the energy flux of an incident laser wave (pump) is transferred

Friedland, Lazar

257

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

E-print Network

Understanding how to harness the plasma is fundamental to developing new technology from the laser-plasma to the interaction of laser pulses with underdense plasma and the transfer of energy and momentum between the laser of magnitude stronger1 than those of conventional particle accelerators. This makes the interaction of intense

Strathclyde, University of

258

Von Karman similarity decay of energy and the heating of protons and electrons in a kinetic plasma  

NASA Astrophysics Data System (ADS)

Decay in time of fluid scale fluctuation energy in undriven weakly collisional kinetic plasma turbulence is a problem of broad interest in space physics. We study this in systems large compared to the ion kinetic scales 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 Karman hypothesis of similarity decay, in a formulation adapted to magnetohydrodyamics (MHD). Kinetic dissipation occurs at small scales, but the overall rate is apparently controlled by large scale dynamics, as it is in the hydrodynamic case. The mechanisms of kinetic dissipation are of particular interest: At small turbulence amplitude the electrons are preferentially heated. At larger amplitudes proton heating is the dominant effect. We suggest this is due to availability of more channels for proton dissipation when the gradients produced by turbulence are larger at proton scales. In the solar wind and corona the protons are typically hotter, suggesting that these natural systems are in large amplitude turbulence regime.

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

2013-12-01

259

A kinetic-MHD model for studying low frequency multiscale phenomena  

Microsoft Academic Search

A nonlinear kinetic-MHD model for studying low frequency multiscale phenomena has been developed by taking advantage of the single fluid MHD model`s simplicity and by properly accounting for core ion finite Larmor radius (FLR) effects and major kinetic effects of energetic particles. The kinetic-MHD model treats the low energy core plasma by a generalized MHD description and energetic particles kinetically;

C. Z. Cheng; J. R. Johnson

1996-01-01

260

Description of HiPIMS plasma regimes in terms of composition, spoke formation and deposition rate  

NASA Astrophysics Data System (ADS)

The behaviour of Cu and Cr HiPIMS (high power impulse magnetron sputtering) discharges was investigated by a combination of optical emission spectroscopy, energy-resolved mass spectrometry and optical imaging, for the complete current–voltage characteristic range achievable within our experimental conditions. Inflection points typical of HiPIMS current–voltage characteristics separate plasma regimes perfectly differentiated in terms of flux composition of species towards the substrate, deposition rate, and the nature of plasma self-organization. The reorganization of the HiPIMS plasma into spokes (areas of high ionization over the target) is associated to one regime of high plasma conductivity, where also deposition rate is limited. This spoke-dominated regime can be substituted by a homogeneous regime at higher powers, where there is an increase of deposition rate, which is driven mostly by an increase in the flux of metal neutrals and metal double-charged ions. The relevance of secondary electron emission mechanisms for the support of the spoke-dominated regime in reactive and non-reactive sputtering conditions is discussed.

de los Arcos, Teresa; Schröder, Raphael; Aranda Gonzalvo, Yolanda; Schulz-von der Gathen, Volker; Winter, Jörg

2014-10-01

261

LSENS, a general chemical kinetics and sensitivity analysis code for homogeneous gas-phase reactions. 2: Code description and usage  

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

262

Analytical evaluation of the Tsytovich-Angelis dust-dust collision functions arising from the kinetic theory of dusty plasmas  

SciTech Connect

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

263

Kinetic instability of the dust acoustic mode in inhomogeneous, partially magnetized plasma with both positively and negatively charged grains  

SciTech Connect

A purely kinetic instability of the dust acoustic mode in inhomogeneous plasmas is discussed. In the presence of a magnetic field, electrons and ions may be magnetized while at the same time dust grains may remain unmagnetized. Although the dynamics of the light species is strongly affected by the magnetic field, the dust acoustic mode may still propagate in practically any direction. The inhomogeneity implies a source of free energy for an instability that develops through the diamagnetic drift effects of the magnetized species. It is shown that this may be a powerful mechanism for the excitation of dust acoustic waves. The analysis presented in the work is also directly applicable to plasmas containing both positive and negative ions and electrons, provided that at least one of the two ion species is unmagnetized.

Vranjes, J.; Poedts, S. [Centre for Plasma Astrophysics, Celestijnenlaan 200B, 3001 Leuven (Belgium) and Leuven Mathematical Modeling and Computational Science Research Centre (LMCC), Celestijnenlaan 200B, 3001 Leuven (Belgium)

2010-08-15

264

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

PubMed

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

Ooguri, Hirosi; Park, Chang-Soon

2011-02-11

265

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

Microsoft Academic Search

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

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

2009-01-01

266

Drift wave instability analysis in pair-ion-electron plasmas using kinetic approach  

SciTech Connect

Drift wave is studied in pair-ion plasmas in the presence of electrons using the Vlasov-Poisson set of equations. The growth rate of this universal instability depends on the concentration of electrons. The real frequency and the growth rate are reduced as the number density of electrons decreases. If the laboratory produced pair-ion plasmas contain relatively small amount of electrons then very low frequency almost stable drift waves can be produced which will indicate that the plasma is not a pure pair-ion plasma. The present investigation can be useful for future experiments on pair-ion plasmas and low density low temperature industrial plasmas which contain negative ions.

Ali, S.; Saleem, H. [National Centre for Physics, Shahdra Valley Road, Quaid-i-Azam University Campus, Islamabad 44000 (Pakistan)

2010-09-15

267

Plasma heating by a relativistic electron beam. I - Wave kinetic equation and spectral function  

NASA Astrophysics Data System (ADS)

A new possibility for plasma heating is proposed and theoretical investigation is performed. Under a suitable experimental condition, the wave induced by the two-stream instability and Buneman/ion-acoustic wave induced by the return current can coexist and interact to yield a new contribution to plasma heating by the relativistic electron beam. The authors assume this is the case and develop the formulation necessary for the analysis of the spectral function of turbulent plasma.

Okazaki, T.; Kato, T.

1980-10-01

268

3D feature profile simulation based on realistic surface kinetic studies of silicon dioxide etch process in fluorocarbon plasmas  

NASA Astrophysics Data System (ADS)

Low pressure fluorocarbon plasmas are commonly used in microelectronics fabrication of plasma etching of dielectric materials. Recently, one of the critical issues in the etching processes of the nanoscale devices is to achieve ultrahigh deep contact hole without anomalous behaviors such as sidewall bowing and twisting profile. To achieve this goal, the fluorocarbon gases have been used to optimize the reactant fluxes and obtain the ideal etch profile. However, the semiconductor industries still suffer from the absence of the robust and predictable modeling tools due to the inherent complex plasma chemistry. As an effort to address this issue, we have developed a 3D topography simulator using the level set algorithm based on new memory saving technique, which is suitable in the contact hole etching. For this feature profile simulation, we performed a fluorocarbon plasma-surface kinetic modeling based on our experimental data, a polymer layer based this model was proposed as considering material balance of deposition and etching through steady-state FC layer. Finally, the modeling results showed good agreements with experimental data and could be used successfully for 3D etch profile simulations with consideration of polymer layer.

Chang, Won-Seok; Yu, Dong-Hun; Cho, Deog-Gyun; Yook, Yeong-Geun; Chun, Poo-Reum; Lee, Se-A.; Kwon, Deuk-Chul; Song, Mi-Young; Yoon, Jung-Sik; Im, Yeon-Ho

2012-10-01

269

Kinetic model of nucleation and growth in silicate melts: Implications for igneous textures and their quantitative description  

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

270

Kinetic modeling of intense, short laser pulses propagating in tenuous plasmas  

E-print Network

through a tenuous plasma. Based on these averaged equations, a new particle code is designed which calculates the particle trajectories on the plasma period time scale. The regime of total cavitation time averaged equations are derived for the motion of particles and the generation of electromagnetic

Hassam, Adil

271

hal-00185109,version1-5Nov2007 KINETIC THEORY OF PLASMAS: TRANSLATIONAL ENERGY  

E-print Network

a unified fluid model for multicomponent plasmas by accounting for the electromagnetic field influence. We of a multiscale perturbation parameter on the collisional operator, the streaming operator, and the collisional to a well defined structure. 1. Introduction Plasmas are ionized gas mixtures, either magnetized or not

Paris-Sud XI, Université de

272

Fluorocarbon polymer deposition kinetics in a low-pressure, high-density, inductively coupled plasma reactor  

Microsoft Academic Search

Maintaining dimensional control and adequate throughput during the etching of submicron features requires plasma etch tools that operate at low pressures and high densities, such as inductively coupled plasmas (ICPs). Unfortunately, in this regime, it has proven difficult to achieve a stable, reproducible chemistry for selective oxide etching of contacts and vias. In particular, it is difficult to control the

M. J. Sowa; M. E. Littau; V. Pohray; J. L. Cecchi

2000-01-01

273

Integrated magnetic and kinetic control of advanced tokamak plasmas on DIII-D based on data-driven models  

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

274

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

E-print Network

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

275

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

E-print Network

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

276

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

NASA Astrophysics Data System (ADS)

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.; Chen, L.; Zonca, F.

2014-02-01

277

Effect of an inductively coupled plasma mass spectrometry sampler interface on electron temperature, electron number density, gas-kinetic temperature and analyte emission intensity upstream in the plasma  

NASA Astrophysics Data System (ADS)

Thomson scattering, Rayleigh scattering and line-of-sight emission intensities of Ca ion and Sr ion from the inductively coupled plasma were measured in the presence and in the absence of an inductively coupled plasma mass spectrometry sampler interface. When present, the sampler interface was located 13 mm above the load coil (ALC); optical measurements were made 6, 7 and 8 mm ALC. The experimental results suggest that both the electron temperature ( Te) and gas-kinetic temperature ( Tg) dropped in the presence of the sampler interface, with the change in Tg seemingly greater than that in Te, suggesting a faster cooling process for the heavy particles. In contrast, electron number density ( ne) seemed to be generally increased in the outer regions of the discharge but went down in the central channel, a reflection that ne is possibly dominated by ambipolar diffusion which becomes less efficient as Te drops. Assuming these results, the plasma decays more gradually ALC and deviates from local thermodynamic equilibrium even more significantly in the presence of the sampler interface. Analyte line emission intensity was either depressed or enhanced in the presence of the interface, depending on the element being observed and the operating conditions. In addition, the change in emission intensity caused by the sampler interface became much more dramatic when a matrix element, such as Li or Zn, was introduced.

Lehn, Scott A.; Warner, Kelly A.; Huang, Mao; Hieftje, Gary M.

2002-11-01

278

Asymptotic description of finite lifetime effects on the photon emission from a quark-gluon plasma  

NASA Astrophysics Data System (ADS)

Direct photons play an important role as electromagnetic probes from the quark-gluon plasma (QGP) which occurs during ultrarelativistic heavy-ion collisions. In this context, it is of particular interest how the finite lifetime of the QGP affects the resulting photon production. Earlier investigations on this question were accompanied by a divergent contribution from the vacuum polarization and by the remaining contributions not being integrable in the ultraviolet (UV) domain. In this work, we provide a different approach in which we do not consider the photon number density at finite times, but for free asymptotic states obtained by switching the electromagnetic interaction according to the Gell-Mann and Low theorem. This procedure eliminates a possible unphysical contribution from the vacuum polarization and, moreover, renders the photon number density UV integrable. It is emphasized that the consideration of free asymptotic states is, indeed, crucial to obtain such physically reasonable results.

Michler, Frank; van Hees, Hendrik; Dietrich, Dennis D.; Greiner, Carsten

2014-06-01

279

Asymptotic description of finite lifetime effects on the photon emission from a quark-gluon plasma  

E-print Network

Direct photons play an important role as electromagnetic probes from the quark-gluon plasma (QGP) which occurs during ultrarelativistic heavy-ion collisions. In this context, it is of particular interest how the finite lifetime of the QGP affects the resulting photon production. Earlier investigations on this question were accompanied by a divergent contribution from the vacuum polarization and by the remaining contributions not being integrable in the ultraviolet (UV) domain. In this work, we provide a different approach in which we do not consider the photon number density at finite times, but for free asymptotic states obtained by switching the electromagnetic interaction according to the Gell-Mann and Low theorem. This procedure eliminates a possible unphysical contribution from the vacuum polarization and, moreover, renders the photon number density UV integrable. It is emphasized that the consideration of free asymptotic states is, indeed, crucial to obtain such physically reasonable results.

Frank Michler; Hendrik van Hees; Dennis D. Dietrich; Carsten Greiner

2013-10-18

280

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

E-print Network

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.

Volkov, Vadim

2012-01-01

281

Kinetic theory of cnoidal dust hole propagation in dusty pair plasmas  

SciTech Connect

The complex pattern and propagation characteristics of cnoidal dust holes in dusty pair plasmas are analyzed in the weak amplitude limit. Dependent on the collective trapping conditions of the charged dust species and of other physically relevant parameters, a new class of electrostatic waves is presented, which supplements the known class of small amplitude waves. As the latter is typically based, in the lowest order, on a linearization of the governing Vlasov-Poisson system, this class of intrinsically nonlinear structures is claimed to be of paramount importance for the completion or at least correction of the theory of plasma turbulence and anomalous transport in electrostatically driven, collisionless, or weakly collisional plasmas.

Schamel, Hans [Physikalisches Institut, Universitaet Bayreuth, D-95466 Bayreuth (Germany)

2009-11-15

282

Kinetic difference of berberine between hippocampus and plasma in rat after intravenous administration of Coptidis rhizoma extract.  

PubMed

In order to investigate the pharmacokinetics of berberine in Coptidis rhizoma extract in rat hippocampus and plasma, a simple and accurate high-performance liquid chromatography method was employed in this study. Berberine was determined using a Hypersil C(18) column with an isocratic mobile phase of acetonitrile-0.05 M potassium dihydrogen phosphate (containing 0.5% triethylamine, pH 3.0) and with UV detection at 236 nm. The lower limit of quantification for berberine in both hippocampus and plasma was 24 ng/ml, and the lowest concentrations of berberine determined in rat hippocampus and plasma samples were 30.7 ng/ml at 48 h and 38.5 ng/ml at 4 h, respectively. The calibration curve for berberine was linear over the concentration range 24--6000 ng/ml. At this concentration range, the overall recoveries (90.6--94.2%) for berberine were determined and the accuracy of intra- and inter-day assays from rat samples were less than 7% RSD. Following intravenous administration of C. rhizoma extract at a dose of 10.2 mg/kg containing 3 mg/kg berberine, berberine in the plasma eliminated rapidly (t(1/2 beta)=1.13 h). However, berberine in the hippocampus increased rapidly (t(1/2 alpha)=0.215 h), peaked at 3.67 h with a concentration of 272 ng/g, and had a slow elimination rate (t(1/2 beta)=12.0 h), which suggests that berberine could have a direct action on neuron and accumulate in the hippocampus. This study first showed the pharmacokinetic characteristics of berberine in rat hippocampus and the kinetic characteristics of berberine are dissimilar in the hippocampus and plasma. PMID:15996686

Wang, Xueli; Wang, Rufeng; Xing, Dongming; Su, Hui; Ma, Chao; Ding, Yi; Du, Lijun

2005-10-28

283

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

E-print Network

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

284

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

E-print Network

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

285

Etching kinetics and surface roughening of polysilicon and dielectric materials in inductively coupled plasma beams  

E-print Network

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

286

Modeling of neutral plasma in a divertor in the fluid-kinetic transition1  

E-print Network

Edge Theory in Fusion Devices, Oxford, England, September 15­16, 1997. 1 Link: http://charles equations). In the case of neutral deuterium, for example, the kinetic neutrals are described by fDkin (x, v, t) and fluid neutrals by nDfl (x, t), vDfl (x, t), and TDfl (x, t). The total neutral deuterium

Karney, Charles

287

The complete relativistic kinetic model of symmetry violation in isotopic expanding plasma. III. Specific entropy calculation  

E-print Network

A complete model of baryon production in an expanding, primordially symmetric hot Universe is constructed in the framework of general-relativistic kinetic theory. In this model specific model for a baryon is calculated and graphs of the value dependence are constructed.

Yu. G. Ignatyev; K. Alsmadi

2010-12-27

288

Kinetic parameters and intraindividual fluctuations of ochratoxin A plasma levels in humans  

Microsoft Academic Search

The mycotoxin ochratoxin A (OTA) is a rodent carcinogen produced by species of the ubiquitous fungal genera Aspergillus and Penicillium. OTA is found in a variety of food items and as a consequence is also found in human plasma (average concentrations found in this study: 0.1-1 ng OTA\\/ml plasma). To improve the scientific basis for cancer risk assessment the toxicokinetic

Irène Studer-Rohr; Josef Schlatter; Daniel R. Dietrich

2000-01-01

289

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

290

Plasma and milk kinetic of eprinomectin and moxidectin in lactating water buffaloes (Bubalus bubalis).  

PubMed

The pharmacokinetics and mammary excretion of moxidectin and eprinomectin were determined in water buffaloes (Bubalus bubalis) following topical administration of 0.5mgkg(-1). Following administration of moxidectin, plasma and milk concentrations of moxidectin increased to reach maximal concentrations (C(max)) of 5.46+/-3.50 and 23.76+/-16.63ngml(-1) at T(max) of 1.20+/-0.33 and 1.87+/-0.77 days in plasma and milk, respectively. The mean residence time (MRT) were similar for plasma and milk (5.27+/-0.45 and 5.87+/-0.80 days, respectively). The AUC value was 5-fold higher in milk (109.68+/-65.01ngdayml(-1)) than in plasma (23.66+/-12.26ngdayml(-1)). The ratio of AUC milk/plasma for moxidectin was 5.04+/-2.13. The moxidectin systemic availability (expressed as plasma AUC values) obtained in buffaloes was in the same range than those reported in cattle. The faster absorption and elimination processes of moxidectin were probably due to a lower storage in fat associated with the fact that animals were in lactation. Nevertheless, due to its high excretion in milk and its high detected maximum concentration in milk which is equivalent or higher to the Maximal Residue Level value (MRL) (40ngml(-1)), its use should be prohibited in lactating buffaloes. Concerning eprinomectin, the C(max) were of 2.74+/-0.89 and 3.40+/-1.68ngml(-1) at T(max) of 1.44+/-0.20 and 1.33+/-0.0.41 days in plasma and milk, respectively. The MRT and the AUC were similar for plasma (3.17+/-0.41 days and 11.43+/-4.01ngdayml(-1)) and milk (2.70+/-0.44 days and 8.49+/-3.33ngdayml(-1)). The ratio of AUC milk/plasma for eprinomectin was 0.76+/-0.16. The AUC value is 20 times lower than that reported in dairy cattle. The very low extent of mammary excretion and the milk levels reported lower than the MRL (20ngml(-1)) supports the permitted use of eprinomectin in lactating water buffaloes. PMID:18774650

Dupuy, Jacques; Sutra, Jean-François; Alvinerie, Michel; Rinaldi, Laura; Veneziano, Vincenzo; Mezzino, Laura; Pennacchio, Saverio; Cringoli, Giuseppe

2008-11-01

291

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

NASA Astrophysics Data System (ADS)

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

Lapenta, Giovanni

2006-04-01

292

5-D Kinetic Modeling of ECH Plasmas in the HSX Stellarator  

NASA Astrophysics Data System (ADS)

The HSX electron cyclotron heating (ECH) system is being upgraded to two 200 kW, 28 GHz gyrotron sources. This new system will allow increased total available ECH power as well as increased heating flexibility with a poloidally steerable launch assembly. Kinetic simulations using the global transport code GNET will model the evolution of the perturbed electron distribution function and radial electron transport due to ECH. GNET solves a linearized drift kinetic equation in five-dimensional phase space, allowing simulations of quasihelically symmetric (QHS) as well as asymmetric magnetic configurations. GNET will be used to determine ECH-driven electron fluxes and estimate modifications to the ambipolar radial electric field obtained from neoclassical theory. GNET calculations will be presented for 2nd-harmonic X-mode at 0.5 Tesla and 1st-harmonic O--mode at 1.0 Tesla operations. Implications for ECE and X-ray diagnostics will also be presented.

Radder, J. W.; Likin, K. M.; Talmadge, J. N.; Anderson, D. T.; Murakami, S.

2008-11-01

293

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

SciTech Connect

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

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

2007-01-15

294

Plasma kinetics of an LDL-like nanoemulsion and lipid transfer to HDL in subjects with glucose intolerance  

PubMed Central

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; Maranhao, Raul C

2012-01-01

295

Plasma electron kinetics in a weak high-frequency field and magnetic field amplification.  

PubMed

We describe the linear stage of Weibel instability in a plasma heated via inverse bremsstrahlung absorption of a high-frequency, moderate intensity radiation field under conditions in which the plasma electron velocity distribution function is weakly anisotropic. We report on the possibility of a significant amplification of spontaneous magnetic fields both in the case of an electron distribution function slightly departing from a Maxwellian in the region of subthermal velocities, and in the case where the Langdon nonequilibrium distribution is formed. We show that the direct influence of collisions on the Weibel instability growth rate may be traced back to subthermal electrons, for which the effective collision frequency is large. PMID:11690157

Ferrante, G; Zarcone, M; Uryupin, S A

2001-10-01

296

Topical Area: MFE Title: Burning Plasma Experimental Options______________________________ Description The options for a Next Step Burning Plasma Experiment are defined by the overall strategic  

E-print Network

of developing and integrating burning plasma physics, long pulse physics and technology, and fusion technologies and confinement program will interact closely with the burning plasma experiment. Enabling technology developmentPage 1 Topical Area: MFE Title: Burning Plasma Experimental Options

297

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

Microsoft Academic Search

In plasma physics, linear instability calculations can be implemented either as initial value calculations or as eigenvalue calculations. Here, comparisons between comprehensive linear gyrokinetic calculations employing the ballooning formalism for high-n (toroidal mode number) toroidal instabilities are described. One code implements an initial value calculation on a grid using a Lorentz collision operator and the other implements an eigenvalue calculation

Mike Kotschenreuther; G. Rewoldt; W. M. Tang

1995-01-01

298

On the kinetics of plasma nitriding a martensitic stainless steel type AISI 420  

Microsoft Academic Search

Plasma nitriding was employed to treat martensitic stainless steel type AISI 420. The ability to remove the passive film from the surface is an important advantage in this process in order to guarantee a homogeneous surface treatment. The resulting nitrided surface shows the presence of a compound layer and a diffusion zone. The interface between the diffusion zone and the

Carlos E. Pinedo; Waldemar A. Monteiro

2004-01-01

299

Kinetics of inhibition of the plasma membrane calcium pump by vanadate in intact human red cells  

Microsoft Academic Search

The lack of specific inhibitors of the plasma membrane Ca2+ pump (PMCA) has made vanadate (VO-3), a non-specific inhibitor, an invaluable tool in the study of PMCA function. However, three important properties of vanadate as an inhibitor of the PMCA in intact cells, namely its speed of action in different experimental conditions, the reversibility of its inhibitory effects at different

T. Tiffert; V. L. Lew

2001-01-01

300

Topical Area MFE Title: Burning Plasma Science_____________________________________________ Description Fusion energy is released by burning light elements using nuclear reactions which consume mass and  

E-print Network

_____________________________________________ · Description Fusion energy is released by burning light elements using nuclear reactions which consume mass to be economically attractive. With Lawson product only ~20% higher, "ignition" is obtained, where the plasma is self-sustained required for optimal stability, transport, and steady-state (long pulse high duty cycle) sustainment

301

von Karman Energy Decay and Heating of Protons and Electrons in a Kinetic Turbulent Plasma P. Wu,1,* M. Wan,1  

E-print Network

von Ka´rma´n Energy Decay and Heating of Protons and Electrons in a Kinetic Turbulent Plasma P. Wu 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

Shay, Michael

302

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

SciTech Connect

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

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

2003-02-26

303

Arbitrary amplitude double layers in warm dust kinetic Alfven wave plasmas  

SciTech Connect

Large amplitude electrostatic structures associated with low-frequency dust kinetic Alfvenic waves are investigated under the pressure (temperature) gradient indicative of dust dynamics. The set of equations governing the dust dynamics, Boltzmann electrons, ions and Maxwell's equation have been reduced to a single equation known as the Sagdeev potential equation. Parameter ranges for the existence of arbitrary amplitude double layers are observed. Exact analytical expressions for the energy integral is obtained and computed numerically through which sub-Alfvenic arbitrary amplitude rarefactive double layers are found to exist.

Gogoi, Runmoni; Devi, Nirupama [Department of Mathematics, Cotton College, Guwahati-781001, Assam (India)

2008-07-15

304

Hybrid-Kinetic Modelling of Space Plasma with Application to Mercury  

NASA Astrophysics Data System (ADS)

A planet's magnetosphere is often very dynamic, undergoing large topological changes in response to high speed (˜400km/s) solar wind intervals, coronal mass ejections, and naturally excited plasma wave modes. Plasma waves are very effective at transporting energy throughout the magnetosphere, and are therefore of interest in the context of the coupling between solar wind and magnetosphere. Of relevance to this thesis is Kelvin-Helmholtz macro-instability. Kelvin-Helmholtz instability (KHI) is excited by shear of the flows. KHI is commonly observed at equatorial regions of the magnetopause where fast flowing magnetosheath plasma may interact with slow bulk velocities of magnetospheric plasma. The instability is responsible for exciting shear Alfven waves which (at Earth) may be detected using the ground based magnetometers located at latitude of excited field lines. This thesis uses numerical modelling to understand and to explain the generation and propagation of the KHI in Mercury's magnetosphere. The instability is initiated close to the planet and convectively grows while being transported along the tail. When the wave amplitude reaches a nonlinear stage, the structure of the wave becomes complex due to the wrapping of the plasma into the vortex. A vortex structure is typical for KHI and it is used for identifying the wave in the data from satellites. The instability commonly occurs at the dawn or dusk flank magnetopause (MP) of Earth with approximately the same probability. But the data from NASA's MESSENGER spacecraft, currently in the orbit of the planet Mercury, suggest a strong asymmetry in the observations of KHI. It is shown that the KHI initiated near the subsolar point evolves into large-scale vortices propagating anti-sunward along the dusk-side MP. The simulations are in agreement with the third flyby of the MESSENGER spacecraft, where saw-tooth oscillations in the plasma density, flow, and magnetic field were observed. The observed asymmetry in the KHI between dawn and dusk is found to be controlled by the finite gyro-radius of ions, and by MP pressure gradients and the large-scale solar wind convection electric field.

Paral, Jan

305

Nonlinear Phenomena of Plasma Waves in a Kinetic Regime: Frequency Shifts, Packets, and Transverse Localization  

NASA Astrophysics Data System (ADS)

The generation and propagation of nonlinear plasma waves is studied using particle-in-cell (PIC) simulations. We concentrate on regimes of interest to inertial fusion and space physics in which wave-particle interactions are important. Experiments soon to be performed at the National Ignition Facility require the understanding and control of stimulated Raman scattering (SRS) for their success. The SRS instability occurs when an incident laser decays into a backscattered light wave and an electron plasma wave. Recent computer simulations of SRS indicate that the daughter plasma waves have finite longitudinal and transverse extent and that they reach large amplitudes. The nonlinear behavior of such waves determines the growth, saturation, and recurrence of SRS. However, little attention has been paid to the behavior of plasma waves having these properties, and their study in SRS simulations is complicated by the large-amplitude light waves associated with the instability. Most theory and simulation work on SRS and its daughter plasma waves has been limited to infinite plane waves, often in the one-dimension limit. This thesis therefore studies isolated electron plasma waves over a wide range of parameters in one and multiple dimensions using PIC simulations. The simulations are performed with the goal of understanding the wave's behavior for parameters relevant to SRS, but the normalized parameters have general applicability to a range of densities and temperatures. Accordingly, an external ponderomotive driver generates traveling waves, driving them either continuously to study their peak amplitude and saturation mechanisms, or impulsively to study their propagation. Several novel effects are identified and characterized, including nonlinear resonance for driven waves, wave packet etching for finite-length waves, and localization and local damping for finite-width waves. Finite-length wave packets are found to erode away at a constant rate due to particle trapping at the rear edge, and a simple physical model is presented that accurately predicts the rate over a wide range of amplitudes and wavelengths. In multiple dimensions, finite width waves are shown to damp along their sides as resonant particles enter from outside the wave and trap. This local damping leads to the localization of a wave around its center. These effects, among others, are related to SRS saturation and behavior when appropriate.

Fahlen, Jay Edward

306

Kinetic transverse dispersion relation for relativistic magnetized electron-positron plasmas with Maxwell-Jüttner velocity distribution functions  

NASA Astrophysics Data System (ADS)

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 < 0). We find that in the anomalous zone of the Alfvén branch, the electromagnetic waves are damped, and there is a maximum wave number for which the Alfvén branch is suppressed. We also study the dependence of the Alfvén velocity and effective 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.; Moya, Pablo S.; Muñoz, Víctor; Viñas, Adolfo F.; Valdivia, J. Alejandro

2014-09-01

307

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

E-print Network

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

308

Kinetics of inflow of matter from electrodes in a radiating cluster of arc discharge plasma  

Microsoft Academic Search

The spectrum of the radiation of a gas-discharge plasma cluster is linked with the inflow of the material of the electrodes into the interelectrode space. Therefore the characteristics of the emission of matter from the electrodes can have a significant effect on the results of spectral analysis. It is known [1-3] that in a variable-current arc the disintegration of the

I. G. Nekrashevich; V. M. Tkachenko

1969-01-01

309

Kinetic Model of Electric Potentials in Localized Collisionless Plasma Structures under Steady Quasi-gyrotropic Conditions  

NASA Technical Reports Server (NTRS)

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.; Birn, J.; Hesse, M.

2012-01-01

310

5-D Kinetic Modeling of ECRH Plasmas in the HSX Stellarator  

NASA Astrophysics Data System (ADS)

The global transport code GNET is used to model the evolution of the perturbed electron distribution function and radial electron transport due to electron cyclotron heating (ECRH) in the HSX stellarator. GNET solves a linearized drift kinetic equation in 5-D phase space, allowing simulation of 3-D HSX magnetic configurations. ECRH is modeled in GNET via a quasi-linear source term calculated with a separate 3-D ray tracing routine for 2nd-harmonic X-mode at 0.5 Tesla operations and 1st-harmonic O--mode at 1.0 Tesla operations. First low input power simulations (< 50kW) show a slight difference between radial transport in quasihelically symmetric and mirror magnetic configurations. GNET predictions of ECRH driven flux, power deposition profiles, and implications for ECE and X-ray diagnostics will be presented.

Radder, J. W.; Talmadge, J. N.; Likin, K. M.; Anderson, D. T.; Murakami, S.

2007-11-01

311

PLASMA EFFECTS ON FAST PAIR BEAMS. II. REACTIVE VERSUS KINETIC INSTABILITY OF PARALLEL ELECTROSTATIC WAVES  

SciTech Connect

The interaction of TeV gamma-rays from distant blazars with the extragalactic background light produces relativistic electron-positron pair beams by the photon-photon annihilation process. Using the linear instability analysis in the kinetic limit, which properly accounts for the longitudinal and the small but finite perpendicular momentum spread in the pair momentum distribution function, the growth rate of parallel propagating electrostatic oscillations in the intergalactic medium is calculated. Contrary to the claims of Miniati and Elyiv, we find that neither the longitudinal nor the perpendicular spread in the relativistic pair distribution function significantly affect the electrostatic growth rates. The maximum kinetic growth rate for no perpendicular spread is even about an order of magnitude greater than the corresponding reactive maximum growth rate. The reduction factors in the maximum growth rate due to the finite perpendicular spread in the pair distribution function are tiny and always less than 10{sup –4}. We confirm earlier conclusions by Broderick et al. and our group that the created pair beam distribution function is quickly unstable in the unmagnetized intergalactic medium. Therefore, there is no need to require the existence of small intergalactic magnetic fields to scatter the produced pairs, so that the explanation (made by several authors) for the Fermi non-detection of the inverse Compton scattered GeV gamma-rays by a finite deflecting intergalactic magnetic field is not necessary. In particular, the various derived lower bounds for the intergalactic magnetic fields are invalid due to the pair beam instability argument.

Schlickeiser, R.; Krakau, S.; Supsar, M., E-mail: rsch@tp4.rub.de, E-mail: steffen.krakau@rub.de, E-mail: markus.supsar@rub.de [Institut für Theoretische Physik, Lehrstuhl IV: Weltraum- und Astrophysik, Ruhr-Universität Bochum, D-44780 Bochum (Germany)

2013-11-01

312

What is a plasma?  

SciTech Connect

This introduction will define the plasma fourth state of matter, where we find plasmas on earth and beyond, and why they are useful. There are applications to many consumer items, fusion energy, scientific devices, satellite communications, semiconductor processing, spacecraft propulsion, and more. Since 99% of our observable universe is ionized gas, plasma physics determines many important features of astrophysics, space physics, and magnetosphere physics in our solar system. We describe some plasma characteristics, examples in nature, some useful applications, how to create plasmas. A brief introduction to the theoretical framework includes the connection between kinetic and fluid descriptions, quasi neutrality, Debye shielding, ambipolar electric fields, some plasma waves. Hands-on demonstrations follow. More complete explanations will follow next week.

Intrator, Thomas P. [Los Alamos National Laboratory

2012-08-30

313

Plasma reactivity in high-power impulse magnetron sputtering through oxygen kinetics  

SciTech Connect

The atomic oxygen metastable dynamics in a Reactive High-Power Impulse Magnetron Sputtering (R-HiPIMS) discharge has been characterized using time-resolved diode laser absorption in an Ar/O{sub 2} gas mixture with a Ti target. Two plasma regions are identified: the ionization region (IR) close to the target and further out the diffusion region (DR), separated by a transition region. The ?s temporal resolution allows identifying the main atomic oxygen production and destruction routes, which are found to be very different during the pulse as compared to the afterglow as deduced from their evolution in space and time.

Vitelaru, Catalin [Laboratoire the Physique de Gaz et Plasmas, UMR 8578 CNRS, Université Paris-Sud, Orsay Cedex 91405 (France) [Laboratoire the Physique de Gaz et Plasmas, UMR 8578 CNRS, Université Paris-Sud, Orsay Cedex 91405 (France); National Institute for Optoelectronics, Magurele-Bucharest, RO 077125 (Romania); Lundin, Daniel [Laboratoire the Physique de Gaz et Plasmas, UMR 8578 CNRS, Université Paris-Sud, Orsay Cedex 91405 (France) [Laboratoire the Physique de Gaz et Plasmas, UMR 8578 CNRS, Université Paris-Sud, Orsay Cedex 91405 (France); Division of Space and Plasma Physics, School of Electrical Engineering, Royal Institute of Technology, Stockholm, SE-100 44 (Sweden); Brenning, Nils [Division of Space and Plasma Physics, School of Electrical Engineering, Royal Institute of Technology, Stockholm, SE-100 44 (Sweden)] [Division of Space and Plasma Physics, School of Electrical Engineering, Royal Institute of Technology, Stockholm, SE-100 44 (Sweden); Minea, Tiberiu [Laboratoire the Physique de Gaz et Plasmas, UMR 8578 CNRS, Université Paris-Sud, Orsay Cedex 91405 (France)] [Laboratoire the Physique de Gaz et Plasmas, UMR 8578 CNRS, Université Paris-Sud, Orsay Cedex 91405 (France)

2013-09-02

314

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

SciTech Connect

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

315

Nonlinear kinetic simulations of ion cyclotron emission from fusion products in large tokamak plasmas  

NASA Astrophysics Data System (ADS)

Ion cyclotron emission (ICE) was the only collective radiative instability, driven by fusion-born ions, observed from deuterium-tritium plasmas in both JET and TFTR (R O Dendy et al., Nucl. Fusion 35, 1733 (1995)). Suprathermal emission, peaked at sequential ion cyclotron harmonics at the outer mid-plane edge, was detected using heating antennas as receivers on JET and using probes in TFTR. The intensity of ICE spectral peaks scaled linearly with fusion reactivity. The underlying emission mechanism appears to be the magnetoacoustic cyclotron instability (MCI), which involves resonance between: the fast Alfv'en wave; cyclotron harmonic waves supported by the energetic ions and by the background thermal plasma; and a set of centrally born fusion products, lying on barely trapped orbits, which undergo large drift excursions. Analytical studies show that the linear growth rate of the MCI corresponds well with certain observational features of ICE, including ones where a nonlinear treatment might be thought essential. To help explain this, we have carried out direct numerical simulations using a particle-in-cell (PIC) code. We focus on the results of extending MCI theory from the linear into the nonlinear regime for large tokamak parameters.

Dendy, Richard; Cook, James; Chapman, Sandra

2012-10-01

316

Kinetics and mechanical study of plasma electrolytic carburizing for pure iron  

NASA Astrophysics Data System (ADS)

In this work, plasma electrolytic surface carburizing of pure iron in aqueous solution consisting of water, glycerin and NH 4Cl was investigated. Surface carburizing was carried out in 20% glycerin solution treated at 750 °C, 800 °C, 900 °C and 950 °C temperatures for 5, 10 and 30 min. The formation of hard carbon-rich layer on the surface of pure iron was confirmed by XRD analysis. Metallographic and SEM studies revealed a rough and dense carburized layer on the surface of the pure iron. Experimental results showed that the thickness of the carburized layers changes with the time and temperature. The average thickness of the carburized layer ranged from 20 to 160 ?m. The hardness of the carburized samples decreased with the distance from the surface to the interior of the test material. The average hardness values of the carburized layers on the substrate ranged 550-850 HV, while the hardness of the substrate ranged from 110 HV to 170 HV. The dominant phases formed on the pure iron were found to be a mixture of cementite (Fe 3C), martensite (Fe + C) and austenite (FCC iron) confirmed by XRD. Wear resistance in all plasma electrolytic carburized samples is considerably improved in relation to the untreated specimen. After carburizing, surface roughness of the samples was increased. Friction coefficients were also increased because of high surface roughness.

Çavu?lu, F.; Usta, M.

2011-02-01

317

Book review: Modern Plasma Physics, Vol. I: Physical Kinetics of Turbulent Plasmas, by Patrick H. Diamond, Sanae-I. Itoh and Kimitaka Itoh, Cambridge University Press, Cambridge (UK), 2010, IX, 417 p., ISBN 978-0-521-86920-1 (Hardback)  

NASA Astrophysics Data System (ADS)

If you want to learn not only the most fundamental things about the physics of turbulent plasmas but also the current state of the problem including the most recent results in theoretical and experimental investigations - and certainly many physicists and astrophysicists do - this series of three excellent monographs is just for you. The first volume "Physical Kinetics of Turbulent Plasmas" develops the kinetic theory of turbulence through a focus on quasi-particle models and dynamics. It discusses the concepts and theoretical methods for describing weak and strong fluid and phase space turbulence in plasma systems far from equilibrium. The core material includes fluctuation theory, self-similar cascades and transport, mean field theory, resonance broadening and nonlinear wave-particle interaction, wave-wave interaction and wave turbulence, strong turbulence theory and renormalization. The book gives readers a deep understanding of the fields under consideration and builds a foundation for future applications to multi-scale processes of self-organization in tokamaks and other confined plasmas. In spite of a short pedagogical introduction, the book is addressed mainly to well prepared readers with a serious background in plasma physics, to researchers and advanced graduate students in nonlinear plasma physics, controlled fusions and related fields such as cosmic plasma physics

Somov, B. V.

318

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

SciTech Connect

A discussion is given of test particle transport in the presence of specified stochastic magnetic fields, with particular emphasis on the collisional limit. Certain paradoxes and inconsistencies in the literature regarding the form of the scaling laws are resolved by carefully distinguishing a number of physically distinct correlation lengths, and thus by identifying several collisional subregimes. The common procedure of averaging the conventional fluid equations over the statistics of a random field is shown to fail in some important cases because of breakdown of the Chapman-Enskog ordering in the presence of a stochastic field component with short autocorrelation length. A modified perturbation theory is introduced which leads to a Kubo-like formula valid in all collisionality regimes. The direct-interaction approximation is shown to fail in the interesting limit in which the orbit exponentiation length L/sub K/ appears explicitly. A higher order renormalized kinetic theory in which L/sub K/ appears naturally is discussed and used to rederive more systematically the results of the heuristic scaling arguments.

Krommes, J.A.; Oberman, C.; Kleva, R.G.

1982-07-01

319

Degradation kinetics of leucine5-enkephalin by plasma samples from healthy controls and various patient populations: in vitro drug effects.  

PubMed

Incubation of [3H]tyrosine leucine5-enkephalin with platelet-poor human plasma (final concentration 1 x 10(-8) M; 1:9 ratio to Trizma base buffer, pH 7.4) resulted in rapid and complete peptide degradation in each of the subjects studied, with more than 95% of the initial labeled tyrosine consistently recovered as the free amino acid (< or =30 minutes). Essentially, and irrespective of the incubation time (1-180 minutes), tyrosine was the only Leu metabolite formed; we were unable to identify significant amounts (> or =3%) of any other possible labeled or nonlabeled Leu degradation fragments. Neither gender (64 men and 20 women; samples tested individually), age (men, 23-70; women, 25-65 years), nor the subjects' medical condition appeared to make a significant difference in either the t1/2 of Leu elimination, the initial velocity of this reaction (x +/- SD, median, minimum and maximum of 12.0 +/- 0.9, 12.0, and 10.6-13.7 minutes; 1.2 +/- 0.3, 1.1, and 0.6-2.0 pg/min, respectively), or in the Km and Vmax values for aminopeptidase Leu degradation (x +/- SD; 0.81 +/- 0.01 mM and 14.30 +/- 1.17 micromol/L/min, respectively). Subjects were diagnosed as chronic schizophrenics (n = 15), polydrug abusers including alcohol (n = 9) and polydrug abusers excluding alcohol (n = 8), chronic alcoholics (n = 12), and migraineurs (n = 10) during or outside an acute migraine episode; for comparison we used a group of gender-matched (20 men and 10 women), age-comparable, drug-free, healthy volunteers. Differences in plasma storage time or repeated sample freezing and thawing failed to alter significantly any of these kinetic parameters of Leu metabolism or to change the identity and/or relative ratio of the products formed. The Leu degradation rate was pH and temperature dependent (optimum, 7.4 and 37 degrees C, respectively). Leu degradation was strongly and similarly inhibited by puromycin, bacitracin, and bestatin (IC50 [+/- SD] of 1.4 +/- 0.2 micromol/L) and to a lesser extent by various L-tyrosine-containing Leu fragments. The kinetics of this reaction was not significantly affected by either thiorphan, N-carboxyphenylmethyl leucine, or any other of a number of monoamine neurotransmitters, substances of abuse, nonsteroidal anti-inflammatory agents, and miscellaneous compounds tested (concentration up to 10(-4) mol/L). PMID:11317167

Mosnaim, A D; Wolf, M E; Nguyen, T D; Puente, J; Freitag, F; Diamond, S

2000-05-01

320

Self-consistent kinetic PIC simulations of collisionless supercritical shocks in astrophysical plasmas with multiple ion species  

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

321

Theoretical description based on general and exact nonextensive dispersion relations of plasma oscillation data and verification of new acoustic plasma waves  

NASA Astrophysics Data System (ADS)

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.

2014-09-01

322

Kinetics of inhibition of the plasma membrane calcium pump by vanadate in intact human red cells.  

PubMed

The lack of specific inhibitors of the plasma membrane Ca2+ pump (PMCA) has made vanadate (VO3-), a non-specific inhibitor, an invaluable tool in the study of PMCA function. However, three important properties of vanadate as an inhibitor of the PMCA in intact cells, namely its speed of action in different experimental conditions, the reversibility of its inhibitory effects at different doses, and its dose-response, had never been characterized, despite extensive use. We report here the speed, reversibility and dose-response of PMCA inhibition by vanadate in intact human red cells. Near maximal inhibitory concentrations (1mM) in the red cell suspension blocked almost instantly the uphill Ca2+ extrusion by the PMCA, regardless of the intracellular Ca2+ concentration, cation composition of the external media, membrane potential or volume-stability of the cell. PMCA inhibition by vanadate, at concentrations of 10mM and 1mM, was not reversed by washing, resuspending, and incubating the cells for up to 2h in vanadate-free media. Vanadate inhibited PMCA-mediated Ca2+ efflux in intact red cells with a K1/2 of approximately 3 microM, a value similar to that described for the Ca2+-ATPase in isolated red cell membranes. PMID:11733940

Tiffert, T; Lew, V L

2001-11-01

323

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

324

Observation of nonlinear couplings between coexisting kinetic geodesic acoustic modes in the edge plasmas of the HT-7 tokamak  

NASA Astrophysics Data System (ADS)

Coexisting multi-geodesic acoustic modes (GAMs), especially coexisting dual GAMs, are observed and studied through Langmuir probe arrays at the edge plasmas of the HT-7 tokamak with lithium-coated walls. The dual GAMs are named a low-frequency GAM (LFGAM) and a high-frequency GAM (HFGAM), and it is found that within the measuring range, the HFGAM propagates outwards while the LFGAM propagates both inwards and outwards with their central frequencies nearly unchanged, and both modes have maximum amplitudes at positions with radial wavenumbers close to zero; meanwhile, the two positions happen to be where the continuum GAM frequency is closest to the central frequencies of the LFGAM and the HFGAM. These characteristics are consistent with those of a kinetic GAM converted from a continuum GAM. The nonlinear couplings between the LFGAM and the HFGAM are also analysed. In this study, we observed not only the interaction between the LFGAM and the HFGAM, but also the self-coupling of the GAM with the beat frequency between them, as well as the coupling between the LFGAM and an unknown mode at ?50 kHz. These nonlinear interactions may play important roles during the saturation process of GAMs. Additionally, amplitude correlation analyses of multi-GAMs indicate that second harmonic GAMs are probably generated from the self-interaction of fundamental GAMs.

Kong, D. F.; Liu, A. D.; Lan, T.; Qiu, Z. Y.; Zhao, H. L.; Sheng, H. G.; Yu, C. X.; Chen, L.; Xu, G. S.; Zhang, W.; Wan, B. N.; Chen, R.; Ding, W. X.; Sun, X.; Xie, J. L.; Li, H.; Liu, W. D.

2013-11-01

325

Higher-order growth rate of instability of obliquely propagating kinetic Alfvén and ion-acoustic solitons in a magnetized non-thermal plasma  

Microsoft Academic Search

The higher-order growth rate of instability for obliquely propagating kinetic Alfvén and ion-acoustic solitons in a magnetized non-thermal plasma have been obtained by the multiple-scale perturbation expansion method developed by Allen and Rowlands (1993). The growth rate of instability is obtained correct to order k2, where k is the wave number of a long-wavelength plane-wave perturbation. The corresponding lowest-order stability

Anup Bandyopadhyay; K. P. Das

2001-01-01

326

Differences in plasma and abomasal kinetics of albendazole and its metabolites in calves grazed on pasture or fed a grain-based diet  

Microsoft Academic Search

We evaluated the comparative plasma and abomasal fluid disposition kinetics of albendazole (ABZ) and its metabolites in calves either grazing on pasture or fed a grain-based concentrate diet. Six male Holstein calves (weight 180 to 200 kg) were allowed to graze on lush pasture for three weeks before intraruminal administration of ABZ at 10 mg kg–1(pasture group). After a three-week

S SÁNCHEZ; L ALVAREZ; A PIS; C LANUSSE

1999-01-01

327

Electromagnetic properties of hot collisionless plasma in magnetic reconnection regions  

Microsoft Academic Search

Investigation of magnetic reconnection processes in a hot collisionless space plasma requires development of new methods for a self-consistent description of plasma dynamics in the region of an X-type magnetic fieldB(r),where kinetic effects of resonant and nonresonant interaction of particles and fields are important and the conventional MHD description is inadequate. Inside the reconnection regions, there is a very strong

V. M. Gubchenko; M. L. Khodachenko

1996-01-01

328

Electromagnetic properties of hot collisionless plasma in magnetic reconnection regions  

Microsoft Academic Search

Investigation of magnetic reconnection processes in a hot collisionless space plasma requires development of new methods for a self-consistent description of plasma dynamics in the region of an X-type magnetic field B(r), where kinetic effects of resonant and nonresonant interaction of particles and fields are important and the conventional MHD description is inadequate. Inside the reconnection regions, there is a

V. M. Gubchenko; M. L. Khodachenko

1996-01-01

329

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

330

Pure rotational CARS thermometry studies of low-temperature oxidation kinetics in air and ethene-air nanosecond pulse discharge plasmas  

NASA Astrophysics Data System (ADS)

Pure rotational CARS thermometry is used to study low-temperature plasma assisted fuel oxidation kinetics in a repetitive nanosecond pulse discharge in ethene-air at stoichiometric and fuel lean conditions at 40 Torr pressure. Air and fuel-air mixtures are excited by a burst of high-voltage nanosecond pulses (peak voltage, 20 kV; pulse duration, ~ 25 ns) at a 40 kHz pulse repetition rate and a burst repetition rate of 10 Hz. The number of pulses in the burst is varied from a few pulses to a few hundred pulses. The results are compared with the previously developed hydrocarbon-air plasma chemistry model, modified to incorporate non-empirical scaling of the nanosecond discharge pulse energy coupled to the plasma with number density, as well as one-dimensional conduction heat transfer. Experimental time-resolved temperature, determined as a function of the number of pulses in the burst, is found to agree well with the model predictions. The results demonstrate that the heating rate in fuel-air plasmas is much faster compared with air plasmas, primarily due to energy release in exothermic reactions of fuel with O atoms generated by the plasma. It is found that the initial heating rate in fuel-air plasmas is controlled by the rate of radical (primarily O atoms) generation and is nearly independent of the equivalence ratio. At long burst durations, the heating rate in lean fuel air-mixtures is significantly reduced when all fuel is oxidized.

Zuzeek, Yvette; Choi, Inchul; Uddi, Mruthunjaya; Adamovich, Igor V.; Lempert, Walter R.

2010-03-01

331

Self-consistent description of the core and boundary plasma in the high-field ignition experiment  

NASA Astrophysics Data System (ADS)

A model has been developed which is capable to describe in a self-consistent way plasma dynamics in the center and edge region of fusion reactor. The core plasma is treated in the frame of 1D radial transport model whereas a 1D analytical model along magnetic field lines for plasma and impurity transport outside the last closed magnetic surface (LCMS) is applied. The model has been used to investigate operation regimes of the high-field IGNITOR experiment.

Stankiewicz, R.; Zagórski, R.

2000-03-01

332

Exact relativistic kinetic theory of an electron beam-plasma system: hierarchy of the competing modes in the system parameter space  

E-print Network

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

333

Global magnetosphere-like 3D structure formation in kinetics by hot magnetized plasma flow characterized by shape of the particle distribution function  

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

334

Self-consistent description of the core and boundary plasma in the high-field ignition experiment  

NASA Astrophysics Data System (ADS)

A model has been developed which is capable to describe in a self-consistent way plasma dynamics in the center and edge regions of fusion reactor. The core plasma is treated in the frame of 1-D radial transport model whereas a 1-D analytical model along magnetic field lines for plasma and impurity transport outside the last closed magnetic surface (LCMS) is applied. The model is suitable to fast scans of the parameter space of the tokamak type reactor and has been used to investigate operation regimes of the high-field IGNITOR experiment.

Stankiewicz, R.; Zagórski, R.

2001-03-01

335

ION\\/PLASMA CARBURIZING; THEORY AND PRACTICE  

Microsoft Academic Search

The manuscript describes plasma carburizing process with an emphasis on process parameters rather than structure-property relationships. Following a brief description of the glow-discharge plasma the results on several steels are presented to show the effect of process parameters on the kinetics of carburizing.A diffusion model, utilizing forward finite difference numerical technique, is also given as an aid in estimating process

N. Y. Pehlivanturk; O. T. Inal

1988-01-01

336

Advanced oxidation processes. description of a kinetic model for the oxidation of hazardous materials in aqueous media with ozone and hydrogen peroxide in a semibatch reactor  

Microsoft Academic Search

A model is presented that describes the kinetics of the oxidation of micropollutants in water with the combination of ozone and hydrogen peroxide in a sparged, semibatch reactor. The model is based on known reactions of the Oâ\\/HâOâ system plus mass-transfer characteristics of the reactor. The principal kinetic species for micropollutant oxidation is assumed to be the hydroxyl radical. The

William H. Glaze; Joon Wun Kang

1989-01-01

337

Advances in electron kinetics and theory of gas discharges  

NASA Astrophysics Data System (ADS)

"Electrons, like people, are fertile and infertile: high-energy electrons are fertile and able to reproduce."—Lev Tsendin Modern physics of gas discharges increasingly uses physical kinetics for analysis of non-equilibrium plasmas. The description of underlying physics at the kinetic level appears to be important for plasma applications in modern technologies. In this paper, we attempt to grasp the legacy of Professor Lev Tsendin, who advocated the use of the kinetic approach for understanding fundamental problems of gas discharges. We outline the fundamentals of electron kinetics in low-temperature plasmas, describe elements of the modern kinetic theory of gas discharges, and show examples of the theoretical approach to gas discharge problems used by Lev Tsendin. Important connections between electron kinetics in gas discharges and semiconductors are also discussed. Using several examples, we illustrate how Tsendin's ideas and methods are currently being developed for the implementation of next generation computational tools for adaptive kinetic-fluid simulations of gas discharges used in modern technologies.

Kolobov, Vladimir I.

2013-10-01

338

Impact of etching kinetics on the roughening of thermal SiO{sub 2} and low-k dielectric coral films in fluorocarbon plasmas  

SciTech Connect

The impact of etching kinetics and etching chemistries on surface roughening was investigated by etching thermal silicon dioxide and low-k dielectric coral materials in C{sub 4}F{sub 8}/Ar plasma beams in an inductive coupled plasma beam reactor. The etching kinetics, especially the angular etching yield curves, were measured by changing the plasma pressure and the feed gas composition which influence the effective neutral-to-ion flux ratio during etching. At low neutral-to-ion flux ratios, the angular etching yield curves are sputteringlike, with a peak around 60 deg. -70 deg. off-normal angles; the surface at grazing ion incidence angles becomes roughened due to ion scattering related ion-channeling effects. At high neutral-to-ion flux ratios, ion enhanced etching dominates and surface roughening at grazing angles is mainly caused by the local fluorocarbon deposition induced micromasking mechanism. Interestingly, the etched surfaces at grazing angles remain smooth for both films at intermediate neutral-to-ion flux ratio regime. Furthermore, the oxygen addition broadens the region over which the etching without roughening can be performed.

Yin Yunpeng; Sawin, Herbert H. [Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2007-07-15

339

Description of the Plasma Potential Control (PPC) System on the Tandem Mirror Experiment-Upgrade (TMX-U)  

SciTech Connect

A set of 18 separately controlled plates have been added to each end of the Tandem Mirror Experiment Upgrade (TMX-U) vessel to allow measurement of end-wall currents and to provide a means of plasma potential control (PPC). These plates are shaped to form elliptical rings separated into quadrants. Each plate can be individually grounded, float at plasma potentials, or be actively biased to control the plasma. Voltage and current monitoring are provided for each of the plates, and the control and monitoring functions are controlled by the PPC system computer. The details of the field line mapping and the plate shapes are discussed, and the control architecture and performance are presented. 1 ref., 5 figs.

Surrena, P.S.; Underwood, R.H.

1985-11-11

340

Transient and stable species kinetics in pulsed cc-rf CF4/H2 plasmas and their relation to surface processes  

NASA Astrophysics Data System (ADS)

Fluorocarbon plasmas are widely used in applications and as model systems for fundamental investigations of complex plasmas. In recent years pulsing of the rf discharge has been used as an additional parameter for process control, because many plasma parameters, e.g. densities and temperatures, become time dependent when the rf power is modulated. In this work tunable diode laser absorption spectroscopy in the mid-IR (IR-TDLAS) was applied to measure time-resolved densities of the transient species CF and CF2 and that of the stable product C2F4 in pulsed CF4/H2 asymmetrical capacitively coupled radio-frequency plasmas at 13.56 MHz. Simultaneously, the thickness of amorphous thin fluorocarbon films (a-C:F) on the powered electrode was determined by means of in situ ellipsometry. Therefore, it was possible to study the correlation between gas phase species and thin film formation. The decay curves of the CF and CF2 densities in the off-phase of the pulsed rf plasma were fitted with a combination of first and second order processes involving the loss processes of these radicals in the gas phase and at the surfaces. Particularly, in the plasma off-phase, the loss of CF2 radicals forming C2F4 was found to be dominant in the CF2 kinetics, but of minor importance for C2F4 production. Plasma process parameters such as total pressure, gas composition, power and power modulation were varied to investigate the interaction between gas phase species and surfaces.

Gabriel, O.; Stepanov, S.; Meichsner, J.

2007-12-01

341

Plasma and memory B-cell kinetics in infants following a primary schedule of CRM 197-conjugated serogroup C meningococcal polysaccharide vaccine.  

PubMed

The induction of persistent protective levels of pathogen-specific antibody is an important goal of immunization against childhood infections. However, antibody persistence is poor after immunization in infancy versus later in life. Serogroup C meningococci (MenC) are an important cause of bacteraemia and meningitis in children. The use of protein-polysaccharide conjugate vaccines against MenC has been associated with a significant decline in the incidence of invasive disease. However, vaccine effectiveness is negligible by more than 1 year after a three-dose priming series in infancy and corresponds to a rapid decline in antibody following an initial immune response. The cellular mechanisms underlying the generation of persistent antibody in this age group are unclear. An essential prelude to larger studies of peripheral blood B cells is an understanding of B-cell kinetics following immunization. We measured MenC- and diphtheria-specific plasma and memory B-cell kinetics in infants receiving a CRM(197) (cross-reactive material; mutant diphtheria toxoid)-conjugated MenC vaccine at 2, 3 and 4 months of age. Plasma cell responses were more delayed after the first dose when compared with the rapid appearance of plasma cells after the third dose. Memory B cells were detectable at all time-points following the third dose as opposed to the low frequency seen following a first dose. This study provides data on B-cell kinetics following a primary schedule of immunization in young infants upon which to base further studies of the underlying cellular mechanism of humoral immunity. PMID:19175802

Kelly, Dominic F; Snape, Matthew D; Perrett, Kirsten P; Clutterbuck, Elizabeth A; Lewis, Susan; Blanchard Rohner, Geraldine; Jones, Meryl; Yu, Ly-Mee; Pollard, Andrew J

2009-05-01

342

Plasma and memory B-cell kinetics in infants following a primary schedule of CRM197-conjugated serogroup C meningococcal polysaccharide vaccine  

PubMed Central

The induction of persistent protective levels of pathogen-specific antibody is an important goal of immunization against childhood infections. However, antibody persistence is poor after immunization in infancy versus later in life. Serogroup C meningococci (MenC) are an important cause of bacteraemia and meningitis in children. The use of protein–polysaccharide conjugate vaccines against MenC has been associated with a significant decline in the incidence of invasive disease. However, vaccine effectiveness is negligible by more than 1 year after a three-dose priming series in infancy and corresponds to a rapid decline in antibody following an initial immune response. The cellular mechanisms underlying the generation of persistent antibody in this age group are unclear. An essential prelude to larger studies of peripheral blood B cells is an understanding of B-cell kinetics following immunization. We measured MenC- and diphtheria-specific plasma and memory B-cell kinetics in infants receiving a CRM197 (cross-reactive material; mutant diphtheria toxoid)-conjugated MenC vaccine at 2, 3 and 4 months of age. Plasma cell responses were more delayed after the first dose when compared with the rapid appearance of plasma cells after the third dose. Memory B cells were detectable at all time-points following the third dose as opposed to the low frequency seen following a first dose. This study provides data on B-cell kinetics following a primary schedule of immunization in young infants upon which to base further studies of the underlying cellular mechanism of humoral immunity. PMID:19175802

Kelly, Dominic F; Snape, Matthew D; Perrett, Kirsten P; Clutterbuck, Elizabeth A; Lewis, Susan; Rohner, Geraldine Blanchard; Jones, Meryl; Yu, Ly-Mee; Pollard, Andrew J

2009-01-01

343

Generalized approach to the description of recombination kinetics in bulk heterojunction solar cells—extending from fully organic to hybrid solar cells  

NASA Astrophysics Data System (ADS)

Lately, research efforts in photovoltaics towards hybrid solar cells based on nanostructured metal oxides and conjugated polymers have been intensifying. However, very limited effort has been spent so far to investigate their recombination kinetics in comparison with their fully organic counterpart. In this work, impedance spectroscopy under different illumination intensities is used to probe the recombination kinetics of hybrid solar cells based on ZnO nanorod arrays and poly(3-hexylthiophene). A recombination-based model developed for fully organic solar cells is effectively applied in our hybrid solar cells, demonstrating their similarity in device physics and establishing the nanorod array/polymer compound as true bulk heterojunction.

Conings, Bert; Baeten, Linny; Boyen, Hans-Gerd; Spoltore, Donato; D'Haen, Jan; Van Bael, Marlies K.; Manca, Jean V.

2012-05-01

344

Exact relativistic kinetic theory of the full unstable spectrum of an electron-beam-plasma system with Maxwell-Jüttner distribution functions  

NASA Astrophysics Data System (ADS)

Following a recent Letter by Bret [Phys. Rev. Lett. 100, 205008 (2008)], we present a detailed report of the entire unstable k spectrum of a relativistic collisionless beam-plasma system within a fully kinetic framework. In contrast to a number of previously published studies, our linear analysis makes use of smooth momentum distribution functions of the Maxwell-Jüttner form. The three competing classes of instabilities, namely, two-stream, filamentation, and oblique modes, are dealt with in a unified manner, no approximation being made regarding the beam-plasma densities, temperatures, and drift energies. We investigate the hierarchy between the competing modes, paying particular attention to the relatively poorly known quasielectrostatic oblique modes in the regime where they govern the system. The properties of the fastest growing oblique modes are examined in terms of the system parameters and compared to those of the dominant two-stream and filamentation modes.

Bret, A.; Gremillet, L.; Bénisti, D.

2010-03-01

345

Exact relativistic kinetic theory of the full unstable spectrum of an electron-beam-plasma system with Maxwell-Jüttner distribution functions.  

PubMed

Following a recent Letter by Bret [Phys. Rev. Lett. 100, 205008 (2008)], we present a detailed report of the entire unstable k spectrum of a relativistic collisionless beam-plasma system within a fully kinetic framework. In contrast to a number of previously published studies, our linear analysis makes use of smooth momentum distribution functions of the Maxwell-Jüttner form. The three competing classes of instabilities, namely, two-stream, filamentation, and oblique modes, are dealt with in a unified manner, no approximation being made regarding the beam-plasma densities, temperatures, and drift energies. We investigate the hierarchy between the competing modes, paying particular attention to the relatively poorly known quasielectrostatic oblique modes in the regime where they govern the system. The properties of the fastest growing oblique modes are examined in terms of the system parameters and compared to those of the dominant two-stream and filamentation modes. PMID:20365877

Bret, A; Gremillet, L; Bénisti, D

2010-03-01

346

Exact relativistic kinetic theory of the full unstable spectrum of an electron-beam-plasma system with Maxwell-Juttner distribution functions  

NASA Astrophysics Data System (ADS)

We present a detailed report of the entire unstable k spectrum of a relativistic collisionless beam-plasma system within a fully Maxwell-Juttner kinetic framework. The three competing classes of instabilities, namely, two-stream, filamentation, and oblique modes, are dealt with in a unified manner, no approximation being made regarding the beam-plasma densities, temperatures, and drift energies. We investigate the hierarchy between the competing modes [1], paying particular attention to the relatively poorly known quasielectrostatic oblique modes in the regime where they govern the system. The properties of the fastest growing oblique modes are examined in terms of the system parameters and compared to those of the dominant two-stream and filamentation modes [2]. [4pt] [1] Bret A., Gremillet L., Bénisti D. and Lefebvre E., Phys. Rev. Lett, 100, 205008, (2008)[0pt] [2] Bret A., Gremillet L. and Bénisti D, Phys. Rev. E, 81, 036402, (2010)

Bret, Antoine; Gremillet, Laurent; Benisti, Didier

2010-11-01

347

An automated liquid chromatographic plasma analysis of amino acids used in combination with positron emission tomography (PET) for determination of in vivo plasma kinetics  

Microsoft Academic Search

Quantification of physiological processes measured with positron emission tomography (PET) requires an “input” function which can be the concentration of administered radio-tracer in plasma. Radioactive nuclides used in PET have short half lives (2–20 min) and a limited time is available for the PET investigation including analysis of the composition of the radioactive signal in plasma. Therefore, an automated method

Karl-Johan Lindner; Per Hartvig; Niklas Tyrefors; Camilla Hedlund; Bengt Långström

1995-01-01

348

The Nonlinear Wave-Wave Interaction of the Kinetic Alfvén Wave and Its Application in the Solar-Terrestrial Space Plasmas  

NASA Astrophysics Data System (ADS)

Kinetic Alfvén waves (KAWs) are dispersive Alfvén waves with perpendicular wavelengths comparable to the ion gyroradius or the electron inertial length. The KAWs can play an important role in plasma heating, particle acceleration, and anomalous particle transport, and have been extensively applied to various active phenomena of plasma. Therefore, the wave characters for the KAWs in various astrophysical and space plasmas have been an interesting subject with extensive attentions. In this thesis we study in depth nonlinear wave-wave interaction processes of the KAWs in various plasma environments, and focus on the nonlinear growth rates of the KAWs caused by these wave-wave coupling processes. In this thesis, we first study the local nonlinear wave-wave coupling among three KAWs in different plasma beta conditions, where Q? m_{e}/m_{i} is the electron-ion mass ratio and ? is the kinetic-magnetic pressure ratio of the plasma. Our results show that: (1) in the inertial region, the reverse decay, where the pump wave decays into two reversely propagating KAWs, is stronger than the parallel decay, where the pump wave decays into two KAWs propagating in the same direction; (2) in the aspect of the wavelength change, the decay rate of the pump wave into the shorter-wavelength daughter waves is higher than that into the longer-wavelength daughter waves, implying that the decay process develops mainly towards exciting small-scale waves; (3) in the kinetic region (Q? ? ? 1) and the high-? region, the nonlinear growth rate decreases with ?, but increases with the ion-electron temperature ratio T_{i}/T_{e}. Secondly, we study the non-local coupling of small-scale KAWs with large-scale Alfvén waves (AWs) and convective cell. The results show that: (1) in the inertial region of ?kinetic region of ?>Q, the coupling occurs in the way of ``AW + KAW1 ? KAW2''; (2) the modulation instability of KAWs can excite the electrostatic convective cell in the inertial region of ?? Q and the magnetostatic convective cell in the kinetic region of Q??ll 1. We finally discuss the coupling between KAWs and high-frequency whistler waves (WWs) and the three-wave coupling among WWs. The results show that: (1) the decay process of ``WW ? WW + KAW'' can effectively excite KAWs, and the excited KAW can propagate parallel or antiparallel to the pump WW; (2) the three-wave coupling process of WWs occurs in the way that the long-wavelength pump wave decays into the short-wavelength waves, and it is dominated by the reverse decay. The results of this thesis show that our results can explain the excitation of two reversely-propagating electron fluxes in the Earth's auroral zone, the generation of KAWs in the solar atmosphere, and the production of WWs propagating towards the Sun in the interplanetary space.

Zhao, J. S.

2012-09-01

349

Deuterium enrichment of plasma determined by nuclear magnetic resonance spectroscopy: Dilution kinetics of sup 2 H sub 2 O and estimation of total body water  

SciTech Connect

We demonstrate the feasibility of quantifying the abundance of {sup 2}H in plasma by nuclear magnetic resonance (NMR) spectroscopy. After adding internal standard (tert-butyl-d9 alcohol) to deproteinized plasma samples containing {sup 2}H{sub 2}O, we determined the ratio of NMR peak areas for {sup 2}H{sub 2}O and tert-butyl-d9 alcohol. This peak-area ratio was directly proportional to the exogenous {sup 2}H enrichment of plasma (difference between measured and naturally occurring {sup 2}H) between 0 and 0.272 atom % (r = 0.999). The coefficient of variation was 1.34% at an exogenous enrichment of 0.136 atom %. We applied this method to a study of the dilution kinetics of {sup 2}H{sub 2}O to determine the optimal time and method of blood sampling for estimation of total body water content. The {sup 2}H enrichment of plasma stabilized by 4 h after intravenous injection of {sup 2}H{sub 2}O, 1 g/kg of body weight, and fluctuated within 2-4% of the 4- to 8-h mean thereafter.

Brans, Y.W.; Schwartz, C.A.; Hood, R.J.; Ksebati, M.B.; Konduri, G.G. (Wayne State Univ., Detroit, MI (USA))

1990-10-01

350

Evaluation of transporter-mediated hepatic uptake in a non-radioactive high-throughput assay: a study of kinetics, species difference and plasma protein effect.  

PubMed

1.?In this manuscript we describe a non-radioactive, high-throughput method to evaluate hepatic uptake using cryopreserved hepatocytes. We have validated the uptake of pravastatin with different amounts of hepatocytes and the impact of the oil layer used in separation. The time- and concentration-dependent uptake profiles of several anionic and cationic charged drugs were evaluated. The results with our method compare favourably with the literature for pravastatin, atorvastatin and estrone 3-sulfate. 2.?Two approaches for kinetic determination (temperature difference and fitting the linear and non-saturable passive diffusion rate in the equation, i.e. V = (V(max) × S)/(K(m) + S) + P(dif) × S) have been evaluated. Kinetic studies indicate that the different approaches for determining passive diffusion can affect K(m) and V(max), but not the clearance of active uptake (V(max)/K(m)). 3.?Using pravastatin as a probe substrate, species differences were observed in the organic anion-transporting polypeptide (OATP) 1B1 and 1B3 activities. Plasma protein significantly reduced the uptake of atorvastatin, but not pravastatin. 4.?Our data suggests that evaluation of the role of active uptake in hepatic clearance in humans should consider the relative ratio of active uptake to passive diffusion, species differences and plasma protein binding when applying in vitro uptake data. PMID:22928802

Li, Ling; Nouraldeen, Amr; Wilson, Alan G E

2013-03-01

351

LSENS, A General Chemical Kinetics and Sensitivity Analysis Code for Homogeneous Gas-Phase Reactions. Part 2; Code Description and Usage  

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

352

Comparative kinetics of damage to the plasma and mitochondrial membranes by intra-cellularly synthesized and externally-provided photosensitizers using multi-color FACS.  

PubMed

Photodynamic therapy (PDT) of cancer involves inflicting lethal damage to the cells of malignant tumors, primarily by singlet oxygen that is generated following light-absorption in a photosensitizer molecule. Dysfunction of cells is manifested in many ways, including peroxidation of cellular components, membrane rupture, depolarization of electric potentials, termination of mitochondrial activity, onset of apoptosis and necrosis and eventually cell lysis. These events do not necessarily occur in linear fashion and different types of damage to cell components occur, most probably, in parallel. In this report we measured the relative rates of damage to two cellular membranes: the plasma membrane and the mitochondrial membrane. We employed photosensitizers of diverse hydrophobicities and used different incubation procedures, which lead to their different intra-cellular localizations. We monitored the damage that was inflicted on these membranes, by employing optical probes of membrane integrity, in a multi-color FACS experiment. The potentiometric indicator JC-1 monitored the electric cross-membrane potential of the mitochondria and the fluorometric indicator Draq7 monitored the rupture of the plasma membrane. We show that the electric depolarization of the mitochondrial membrane and the damage to the enveloping plasma membrane proceed with different kinetics that reflect the molecular character and intracellular location of the sensitizer: PpIX that is synthesized in the cells from ALA causes rapid mitochondrial damage and very slow damage to the plasma membrane, while externally added PpIX has an opposite effect. The hydrophilic sensitizer HypS4 can be taken up by the cells by different incubation conditions, and these affect its intracellular location, and as a consequence either the plasma membrane or the mitochondria is damaged first. A similar correlation was found for additional extracellularly-provided photosensitizers HP and PpIX. PMID:24173598

Haupt, Sara; Malik, Zvi; Ehrenberg, Benjamin

2014-01-01

353

Kinetic analysis of intravirion reverse transcription in the blood plasma of human immunodeficiency virus type 1-infected individuals: direct assessment of resistance to reverse transcriptase inhibitors in vivo.  

PubMed Central

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

354

Integrated Kinetic Simulation of Laser-Plasma Interactions, Fast-electron Generation and Transport in Fast Ignition  

Microsoft Academic Search

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 so the displacement current can be neglected; and an Ohm's law with electron

Andreas Kemp; B Cohen; L Divol

2009-01-01

355

Integrated kinetic simulation of laser-plasma interactions, fast-electron generation, and transport in fast ignition  

Microsoft Academic Search

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.

A. J. Kemp; B. I. Cohen; L. Divol

2010-01-01

356

Kinetics of human soluble and membrane-bound catechol O-methyltransferase: a revised mechanism and description of the thermolabile variant of the enzyme.  

PubMed

Human soluble (S) and membrane-bound (MB) catechol O-methyltransferase (COMT, EC 2.1.1.6) enzymes have been expressed at sufficiently high levels in Escherichia coli and in baculovirus-infected insect cells to allow kinetic characterization of the enzyme forms. The use of tight-binding inhibitors such as entacapone enabled the estimation of actual enzyme concentrations and, thereby, comparison of velocity parameters, substrate selectivity, and regioselectivity of the methylation of both enzyme forms. Kinetics of the methylation reaction of dopamine, (-)-noradrenaline, L-dopa, and 3,4-dihydroxybenzoic acid was studied in detail. Here, the catalytic number (Vmax) of S-COMT was somewhat higher than that of MB-COMT for all four substrates. The Km values varied considerably, depending on both substrate and enzyme form. S-COMT showed about 15 times higher Km values for catecholamines than MB-COMT. The distinctive difference between the enzyme forms was also the higher affinity of MB-COMT for the coenzyme S-adenosyl-L-methionine (AdoMet). The average dissociation constants Ks were 3.4 and 20.2 microM for MB-COMT and S-COMT, respectively. Comparison between the kinetic results and the atomic structure of S-COMT is presented, and a revised mechanism for the reaction cycle is discussed. Two recently published human COMT cDNA sequences differed in the position of S-COMT amino acid 108, the residue being either Val-108 [Lundström et al. (1991) DNA Cell. Biol. 10, 181-189] or Met-108 [Bertocci et al. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 1416-1420].(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7703232

Lotta, T; Vidgren, J; Tilgmann, C; Ulmanen, I; Melén, K; Julkunen, I; Taskinen, J

1995-04-01

357

Landau Diamagnetism of Degenerate Collisional Plasma  

E-print Network

For the first time the kinetic description of Landau diamagnetism for degenerate collisional plasma is given. The correct expression for transverse electric conductivity of the quantum plasma, found by authors (see arXiv:1002.1017 [math-ph] 4 Feb 2010) is used. In work S. Dattagupta, A.M. Jayannavar and N. Kumar [Current science, V. 80, No. 7, 10 April, 2001] was discussed the important problem of dissipation (collisions) influence on Landau diamagnetism. The analysis of this problem is given with the use of exact expression for transverse conductivity of quantum plasma.

A. V. Latyshev; A. A. Yushkanov

2010-07-05

358

Nonlinear evolution of a single coherent mode in a turbulent plasma  

NASA Astrophysics Data System (ADS)

We consider the excitation, nonlinear evolution and saturation of a single coherent mode in a turbulent plasma background. We adopt a generic wave-kinetic description of plasma turbulence, based on a Wigner-Moyal equation, which stays valid well beyond the geometric optics approximation. We illustrate our model by considering the case of a geodesic acoustic mode in a tokamak plasma, in the presence of a broad spectrum of drift wave turbulence.

Mendonça, J. T.; Galvão, R. M. O.; Smolyakov, A. I.

2014-05-01

359

Towards First-principles Control-oriented Modeling of the Magnetic and Kinetic Plasma Profile Evolutions in ITER  

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

360

Kinetics and Energetics of Mg 2+ ,ATP-Dependent Ca 2+ Transport in the Plasma Membrane of Smooth Muscle Cells  

Microsoft Academic Search

Calcium ions play a crucial role in the excitation\\/contraction coupling in smooth muscles. I would like to interpret the biochemical mechanisms underlying Ca2+ exchange and dynamics of such an exchange in the smooth muscles. Particular emphasis is laid on the examination of kinetic, energetic, and catalytic properties of the membrane-linked energy-dependent Ca2+-transporting systems involved in regulation of the intracellular Ca2+

S. O. Kosterin

2003-01-01

361

Mechanism of calmodulin recognition of the binding domain of isoform 1b of the plasma membrane Ca2+-ATPase: kinetic pathway and effects of methionine oxidation  

PubMed Central

Calmodulin (CaM) binds to a domain near the C-terminus of the plasma-membrane Ca2+-ATPase (PMCA), causing the release of this domain and relief of its autoinhibitory function. We investigated the kinetics of dissociation and binding of Ca2+-CaM with a 28-residue peptide (C28W(1b)) corresponding to the CaM binding domain of isoform 1b of PMCA. CaM was labeled with a fluorescent probe on either the N-terminal domain at residue 34 or on the C-terminal domain at residue 110. Formation of complexes of CaM with C28W(1b) results in a decrease in the fluorescence yield of the fluorophore, allowing the kinetics of dissociation or binding to be detected. Using a maximum entropy method, we determined the minimum number and magnitudes of rate constants required to fit the data. Comparison of the fluorescence changes for CaM labeled on the C-terminal or N-terminal domain suggests sequential and ordered binding of the C-terminal and N-terminal domains of CaM with C28W(1b). For dissociation of C28W(1b) from CaM labeled on the N-terminal domain, we observed three time constants, indicating the presence of two intermediate states in the dissociation pathway. However, for CaM labeled on the C-terminal domain, we observed only two time constants, suggesting that the fluorescence label on the C-terminal domain was not sensitive to one of the kinetic steps. The results were modeled by a kinetic mechanism where an initial complex forms upon binding of the C-terminal domain of CaM to C28W(1b), followed by binding of the N-terminal domain, and then formation of a tight binding complex. Oxidation of methionine residues in CaM resulted in significant perturbations to the binding kinetics. The rate of formation of a tight binding complex was reduced, consistent with the lower effectiveness of oxidized CaM in activating the Ca2+ pump. PMID:17343368

Slaughter, Brian D.; Bieber Urbauer, Ramona J.; Urbauer, Jeffrey L.; Johnson, Carey K.

2008-01-01

362

Dynamics of pickup ion velocity distribution function in Titan's plasma environment (TA encounter): 3D hybrid kinetic modeling and comparison with CAPS observations  

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

363

Magnetic susceptibility and Landau diamagnetism of quantum collisional degenerate plasmas  

E-print Network

With the use of correct expression of the electric conductivity of quantum collisional degenerate plasmas (A. V. Latyshev and A. A. Yushkanov, Transverse electrical conductivity of a quantum collisional plasma in the Mermin approach, - Theor. and Math. Phys., {\\bf 175}(1): 559-569 (2013)) the kinetic description of a magnetic susceptibility is obtained and the formula for calculation of Landau diamagnetism is deduced.

Latyshev, A V

2013-01-01

364

Magnetic susceptibility and Landau diamagnetism of quantum collisional degenerate plasmas  

E-print Network

With the use of correct expression of the electric conductivity of quantum collisional degenerate plasmas (A. V. Latyshev and A. A. Yushkanov, Transverse electrical conductivity of a quantum collisional plasma in the Mermin approach, - Theor. and Math. Phys., {\\bf 175}(1): 559-569 (2013)) the kinetic description of a magnetic susceptibility is obtained and the formula for calculation of Landau diamagnetism is deduced.

A. V. Latyshev; A. A. Yushkanov

2013-05-21

365

Magnetic Susceptibility and Landau Diamagnetism of Quantum Collisional Maxwellian Plasmas  

E-print Network

With the use of correct expression of the electric conductivity of quantum collisional plasmas (A. V. Latyshev and A. A. Yushkanov, {\\it Transverse electrical conductivity of a quantum collisional plasma in the Mermin approach}. - Theor. and Math. Phys., {\\bf 175}(1): 559-569 (2013)) the kinetic description of a magnetic susceptibility is obtained and the formula for calculation of Landau diamagnetism is deduced.

A. V. Latyshev; A. A. Yushkanov

2013-06-03

366

Magnetic Susceptibility and Landau Diamagnetism of Quantum Collisional Maxwellian Plasmas  

E-print Network

With the use of correct expression of the electric conductivity of quantum collisional plasmas (A. V. Latyshev and A. A. Yushkanov, {\\it Transverse electrical conductivity of a quantum collisional plasma in the Mermin approach}. - Theor. and Math. Phys., {\\bf 175}(1): 559-569 (2013)) the kinetic description of a magnetic susceptibility is obtained and the formula for calculation of Landau diamagnetism is deduced.

Latyshev, A V

2013-01-01

367

Kinetics of ion and prompt electron emission from laser-produced plasma N. Farid,1,2  

E-print Network

study of plasma properties employing fast photography, time, and space resolved optical emission application. The most important parameters that influence LA properties include laser wavelength, pulse width, laser pulse duration,18 wavelength,19 and power density20 of the laser and as well as physical

Harilal, S. S.

368

Integrated kinetic simulation of laser-plasma interactions, fast-electron generation, and transport in fast ignition  

SciTech Connect

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

369

Integrated Kinetic Simulation of Laser-Plasma Interactions, Fast-Electron Generation and Transport in Fast Ignition  

SciTech Connect

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

370

Brain concentrations of tricyclic antidepressants: Single-dose kinetics and relationship to plasma concentrations in chronically dosed rats  

Microsoft Academic Search

A previously reported method of measuring tricyclic antidepressant concentrations in brain tissue and plasma was used to measure amitriptyline (AMI) in rats following drug administration using different routes, doses, and time intervals. In rats given AMI intraperitoneally (IP), brain concentrations increased during the first 30 min after drug adminstration and then declined. Brain concentrations increased linearly with changes in IP

Robin K. Glotzbach; Sheldon H. Preskorn

1982-01-01

371

Synthesis of ?-TiAl by Reactive Spark Plasma Sintering of Cryomilled Ti and Al Powder Blend: Part II: Effects of Electric Field and Microstructure on Sintering Kinetics  

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

Comparison of BES measurements of ion-scale turbulence with direct gyro-kinetic simulations of MAST L-mode plasmas  

NASA Astrophysics Data System (ADS)

Observations of ion-scale (ky?i ? 1) density turbulence of relative amplitude ?0.2% are available on the Mega Amp Spherical Tokamak (MAST) using a 2D (8 radial × 4 poloidal channel) imaging beam emission spectroscopy diagnostic. Spatial and temporal characteristics of this turbulence, i.e., amplitudes, correlation times, radial and perpendicular correlation lengths and apparent phase velocities of the density contours, are determined by means of correlation analysis. For a low-density, L-mode discharge with strong equilibrium flow shear exhibiting an internal transport barrier in the ion channel, the observed turbulence characteristics are compared with synthetic density turbulence data generated from global, non-linear, gyro-kinetic simulations using the particle-in-cell code NEMORB. This validation exercise highlights the need to include increasingly sophisticated physics, e.g., kinetic treatment of trapped electrons, equilibrium flow shear and collisions, to reproduce most of the characteristics of the observed turbulence. Even so, significant discrepancies remain: an underprediction by the simulations of the turbulence amplitude and heat flux at plasma periphery and the finding that the correlation times of the numerically simulated turbulence are typically two orders of magnitude longer than those measured in MAST. Comparison of these correlation times with various linear timescales suggests that, while the measured turbulence is strong and may be ‘critically balanced’, the simulated turbulence is weak.

Field, A. R.; Dunai, D.; Ghim, Y.-c.; Hill, P.; McMillan, B.; Roach, C. M.; Saarelma, S.; Schekochihin, A. A.; Zoletnik, S.; the MAST Team

2014-02-01

373

Kinetic theory of spatially homogeneous systems with long-range interactions: III. Application to power law potentials, plasmas, stellar systems, and to the HMF model  

NASA Astrophysics Data System (ADS)

We apply the general results of the kinetic theory of systems with long-range interactions to particular systems of physical interest. We consider repulsive and attractive power law potentials of interaction with in a space of dimension d . For , strong collisions must be taken into account and the evolution of the system is governed by the Boltzmann equation or by a modified Landau equation; for , strong collisions are negligible and the evolution of the system is governed by the Lenard-Balescu equation. In the marginal case , we can use the Landau equation (with appropriately justified cut-offs) as a relevant approximation of the Boltzmann and Lenard-Balescu equations. The divergence at small scales that appears in the original Landau equation is regularized by the effect of strong collisions. In the case of repulsive interactions with a neutralizing background ( e.g. plasmas), the divergence at large scales that appears in the original Landau equation is regularized by collective effects accounting for Debye shielding. In the case of attractive interactions ( e.g. gravity), it is regularized by the spatial inhomogeneity of the system and its finite extent. We provide explicit analytical expressions of the diffusion and friction coefficients, and of the relaxation time, depending on the value of the exponent and on the dimension of space d . We treat in a unified framework the case of Coulombian plasmas and stellar systems in various dimensions of space, and the case of the attractive and repulsive HMF models.

Chavanis, Pierre-Henri

2013-10-01

374

REVIEWS OF TOPICAL PROBLEMS: Particle kinetics in highly turbulent plasmas (renormalization and self-consistent field methods)  

NASA Astrophysics Data System (ADS)

This review presents methods available for calculating transport coefficients for impurity particles in plasmas with strong long-wave MHD-type velocity and magnetic-field fluctuations, and random ensembles of strong shock fronts. The renormalization of the coefficients of the mean-field equation of turbulent dynamo theory is also considered. Particular attention is devoted to the renormalization method developed by the authors in which the renormalized transport coefficients are calculated from a nonlinear transcendental equation (or a set of such equations) and are expressed in the form of explicit functions of pair correlation tensors describing turbulence. Numerical calculations are reproduced for different turbulence spectra. Spatial transport in a magnetic field and particle acceleration by strong turbulence are investigated. The theory can be used in a wide range of practical problems in plasma physics, atmospheric physics, ocean physics, astrophysics, cosmic-ray physics, and so on.

Bykov, Andrei M.; Toptygin, Igor'N.

1993-11-01

375

Kinetic difference of berberine between hippocampus and plasma in rat after intravenous administration of Coptidis rhizoma extract  

Microsoft Academic Search

In order to investigate the pharmacokinetics of berberine in Coptidis rhizoma extract in rat hippocampus and plasma, a simple and accurate high-performance liquid chromatography method was employed in this study. Berberine was determined using a Hypersil C18 column with an isocratic mobile phase of acetonitrile–0.05 M potassium dihydrogen phosphate (containing 0.5% triethylamine, pH 3.0) and with UV detection at 236

Xueli Wang; Rufeng Wang; Dongming Xing; Hui Su; Chao Ma; Yi Ding; Lijun Du

2005-01-01

376

A two-compartment description and kinetic procedure for measuring regional cerebral ( sup 11 C)nomifensine uptake using positron emission tomography  

SciTech Connect

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

377

Magnetospheric space plasma investigations  

NASA Astrophysics Data System (ADS)

Topics and investigations covering this period of this semiannual report period (August 1994 - January 1995) are as follows: (1) Generalized SemiKinetic (GSK) modeling of the synergistic interaction of transverse heating of ionospheric ions and magnetospheric plasma-driven electric potentials on the auroral plasma transport. Also, presentations of GSK modeling of auroral electron precipitation effects on ionospheric plasma outflows, of ExB effects on such outflow, and on warm plasma thermalization and other effects during refilling with pre-existing warm plasmas; (2) Referees' reports received on the statistical study of the latitudinal distributions of core plasmas along the L = 4.6 field line using DE-1/RIMS data. Other work is concerned in the same field, field-aligned flows and trapped ion distributions; and (3) A short study has been carried out on heating processes in low density flux tubes in the outer plasmasphere. The purpose was to determine whether the high ion temperatures observed in these flux tubes were due to heat sources operating through the thermal electrons or directly to the ions. Other investigations center along the same area of plasmasphere-ionosphere coupling. The empirical techniques and model, the listing of hardware calibrated, and/or tested, and a description of notable meetings attended is included in this report, along with a list of all present publication in submission or accepted and those reference papers that have resulted from this work thus far.

Comfort, Richard H.; Horwitz, James L.

1995-02-01

378

Magnetospheric space plasma investigations  

NASA Technical Reports Server (NTRS)

Topics and investigations covering this period of this semiannual report period (August 1994 - January 1995) are as follows: (1) Generalized SemiKinetic (GSK) modeling of the synergistic interaction of transverse heating of ionospheric ions and magnetospheric plasma-driven electric potentials on the auroral plasma transport. Also, presentations of GSK modeling of auroral electron precipitation effects on ionospheric plasma outflows, of ExB effects on such outflow, and on warm plasma thermalization and other effects during refilling with pre-existing warm plasmas; (2) Referees' reports received on the statistical study of the latitudinal distributions of core plasmas along the L = 4.6 field line using DE-1/RIMS data. Other work is concerned in the same field, field-aligned flows and trapped ion distributions; and (3) A short study has been carried out on heating processes in low density flux tubes in the outer plasmasphere. The purpose was to determine whether the high ion temperatures observed in these flux tubes were due to heat sources operating through the thermal electrons or directly to the ions. Other investigations center along the same area of plasmasphere-ionosphere coupling. The empirical techniques and model, the listing of hardware calibrated, and/or tested, and a description of notable meetings attended is included in this report, along with a list of all present publication in submission or accepted and those reference papers that have resulted from this work thus far.

Comfort, Richard H.; Horwitz, James L.

1995-01-01

379

Futile Na+ cycling at the root plasma membrane in rice (Oryza sativa L.): kinetics, energetics, and relationship to salinity tolerance  

PubMed Central

Globally, over one-third of irrigated land is affected by salinity, including much of the land under lowland rice cultivation in the tropics, seriously compromising yields of this most important of crop species. However, there remains an insufficient understanding of the cellular basis of salt tolerance in rice. Here, three methods of 24Na+ tracer analysis were used to investigate primary Na+ transport at the root plasma membrane in a salt-tolerant rice cultivar (Pokkali) and a salt-sensitive cultivar (IR29). Futile cycling of Na+ at the plasma membrane of intact roots occurred at both low and elevated levels of steady-state Na+ supply ([Na+]ext=1?mM and 25?mM) in both cultivars. At 25?mM [Na+]ext, a toxic condition for IR29, unidirectional influx and efflux of Na+ in this cultivar, but not in Pokkali, became very high [>100??mol g (root FW)?1 h?1], demonstrating an inability to restrict sodium fluxes. Current models of sodium transport energetics across the plasma membrane in root cells predict that, if the sodium efflux were mediated by Na+/H+ antiport, this toxic scenario would impose a substantial respiratory cost in IR29. This cost is calculated here, and compared with root respiration, which, however, comprised only ?50% of what would be required to sustain efflux by the antiporter. This suggests that either the conventional ‘leak-pump’ model of Na+ transport or the energetic model of proton-linked Na+ transport may require some revision. In addition, the lack of suppression of Na+ influx by both K+ and Ca2+, and by the application of the channel inhibitors Cs+, TEA+, and Ba2+, questions the participation of potassium channels and non-selective cation channels in the observed Na+ fluxes. PMID:18854575

Malagoli, Philippe; Britto, Dev T.; Schulze, Lasse M.; Kronzucker, Herbert J.

2008-01-01

380

Magnetic susceptibility and Landau diamagnetism of a quantum collisional Plasmas with arbitrary degree of degeneration of electronic gas  

E-print Network

The kinetic description of magnetic susceptibility and Landau diamagnetism of quantum collisional plasmas with any degeration of electronic gas is given. The correct expression of electric conductivity of quantum collisional plasmas with any degeration of electronic gas (see A. V. Latyshev and A. A. Yushkanov, Transverse electrical conductivity of a quantum collisional plasma in the Mermin approach. - Theor. and Math. Phys., V. 175(1):559-569 (2013)) is used.

Latyshev, A V

2013-01-01

381

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

382

Augmented-reality visualization of brain structures with stereo and kinetic depth cues: system description and initial evaluation with head phantom  

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

383

Plasma Physics  

Microsoft Academic Search

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

384

Surface response of tungsten to helium and hydrogen plasma flux as a function of temperature and incident kinetic energy  

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

385

Space plasma education at moscow state university  

NASA Astrophysics Data System (ADS)

The beginning of energetic particles and space plasma research with the launching of the first satellites brought the necessity of educating specialists in this field. In Moscow State University such specialists are educated in the Cosmic Rays and Space Physics Group. For students who intend to participate in satellite experiments this education includes a Space Plasma lecture course. This course includes the of main space plasma problems such as theoretical approaches to plasma description (single particle, fluid and kinetic approximations, plasma waves and instabilities, weak and strong turbulence, solitons and shock waves, etc.) and the main aspects of solar atmosphere physics, solar wind, magnetosphere and ionosphere of the Earth. The main goal of the education process is to prepare a student for independent scientific research which generally begins in the sixth semester. In most cases the student's diploma work is followed by a publication in one of the space journals. The main problems of increasing the quality of the education are analyzed.

Antonova, E. E.

386

Kinetic Equation with Electromagnetic Interactions.  

National Technical Information Service (NTIS)

A kinetic equation for a plasma with electromagnetic interactions is derived in the shielding approximation. The equation is the analog of the Landau equation and has the same structure as the Landau equation but with a velocity dependent interaction repl...

J. T. Hogan, M. B. Lewis

1967-01-01

387

Drought description  

USGS Publications Warehouse

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

388

Kinetic description of hadron-hadron collisions  

E-print Network

A transport model based on the mean free path approach to describe pp collisions is proposed. We assume that hadrons can be treated as bags of partons similarly to the MIT bag model. When the energy density in the collision is higher than a critical value, the bags break and partons are liberated. The partons expand and can make coalescence to form new hadrons. The results obtained compare very well with available data and some prediction for higher energies collisions are discussed. Based on the model we suggest that a QGP could already be formed in the pp collisions at high energies.

Zhi Guang Tan; S. Terranova; A. Bonasera

2007-07-05

389

Wave kinetics and photon acceleration  

Microsoft Academic Search

We review recent theoretical work on photon kinetics and wave kinetics in a plasma, where resonant interactions of waves with photons, and with quasi-particles such as plasmons, is considered. A Wigner function, or quasi-distribution function, for photons and quasi-particles, is introduced. The resulting wave kinetic equation is able to describe the evolution of a broad photon spectrum, or more generally,

J T Mendonça

2006-01-01

390

BOOK REVIEW: Physics of Strongly Coupled Plasma  

NASA Astrophysics Data System (ADS)

Strongly coupled plasmas (or non-ideal plasmas) are multi-component charged many-particle systems, in which the mean value of the potential energy of the system is of the same order as or even higher than the mean value of the kinetic energy. The constituents are electrons, ions, atoms and molecules. Dusty (or complex) plasmas contain still mesoscopic (multiply charged) particles. In such systems, the effects of strong coupling (non-ideality) lead to considerable deviations of physical properties from the corresponding properties of ideal plasmas, i.e., of plasmas in which the mean kinetic energy is essentially larger than the mean potential energy. For instance, bound state energies become density dependent and vanish at higher densities (Mott effect) due to the interaction of the pair with the surrounding particles. Non-ideal plasmas are of interest both for general scientific reasons (including, for example, astrophysical questions), and for technical applications such as inertially confined fusion. In spite of great efforts both experimentally and theoretically, satisfactory information on the physical properties of strongly coupled plasmas is not at hand for any temperature and density. For example, the theoretical description of non-ideal plasmas is possible only at low densities/high temperatures and at extremely high densities (high degeneracy). For intermediate degeneracy, however, numerical experiments have to fill the gap. Experiments are difficult in the region of `warm dense matter'. The monograph tries to present the state of the art concerning both theoretical and experimental attempts. It mainly includes results of the work perfomed in famous Russian laboratories in recent decades. After outlining basic concepts (chapter 1), the generation of plasmas is considered (chapter 2, chapter 3). Questions of partial (chapter 4) and full ionization (chapter 5) are discussed including Mott transition and Wigner crystallization. Electrical and optical properties are the topics of chapters 6 to 8, followed by problems of metallization (chapter 9), non-neutral and dusty plasmas (chapter 10, chapter 11). References follow after each chapter. The book is of interest for obtaining an overview of the field, and is recommended reading. However, for more detailed information on special (theoretical) topics, one should go into the literature. Little is said with respect to kinetic theory, to the theory of ionization kinetics, to stopping power, effective potentials, and to spectral lines in dense plasmas. The interaction between laser or particle beams and plasmas and the evaluation of the results discussing Hugoniots is only touched on briefly. Astrophysics is not dealt with at all. Some misprints concerning names and years in the references may cause difficulties.

Kraeft, Wolf-Dietrich

2007-07-01

391

Kinetic Atom.  

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

392

Michigan Institute for Plasma Sci-  

E-print Network

kinetics and plasma elec- trodynamics, plasma diagnostics, light source science and technology, plasmaMichigan Institute for Plasma Sci- ence and Engi- neering Seminar Physics of Low Pressure Inductive Discharges Dr. Valery Godyak RF Plasma Consulting & University of Michigan Wednesday, 1 December 2010 - 4

Shyy, Wei

393

PLASMA PHYSICS PPPL UC Davis  

E-print Network

PRINCETON PLASMA PHYSICS LABORATORY PPPL UC Davis PRINCETON PLASMA PHYSICS LABORATORY PPPL UC Davis. Domier and N.C. Luhmann, Jr. UC at Davis at Workshop on Long Time Simulations of Kinetic Plasmas April 21, 2006 Hyatt Regency, Dallas, TX #12;PRINCETON PLASMA PHYSICS LABORATORY PPPL UC Davis PRINCETON PLASMA

394

Alfven waves in dusty plasmas with plasma particles described by anisotropic kappa distributions  

SciTech Connect

We utilize a kinetic description to study the dispersion relation of Alfven waves propagating parallelly to the ambient magnetic field in a dusty plasma, taking into account the fluctuation of the charge of the dust particles, which is due to inelastic collisions with electrons and ions. We consider a plasma in which the velocity distribution functions of the plasma particles are modelled as anisotropic kappa distributions, study the dispersion relation for several combinations of the parameters {kappa}{sub Parallel-To} and {kappa}{sub Up-Tack }, and emphasize the effect of the anisotropy of the distributions on the mode coupling which occurs in a dusty plasma, between waves in the branch of circularly polarized waves and waves in the whistler branch.

Galvao, R. A.; Ziebell, L. F. [Instituto de Fisica, Universidade Federal do Rio Grande do Sul, Caixa Postal 15051, CEP: 91501-970, Porto Alegre, Rio Grande do Sul (Brazil); Gaelzer, R. [Instituto de Fisica e Matematica, Universidade Federal de Pelotas, Caixa Postal 354-Campus UFPel, CEP: 96010-900 Pelotas, Rio Grande do Sul (Brazil); Juli, M. C. de [Centro de Radio-Astronomia e Astrofisica Mackenzie-CRAAM, Universidade Presbiteriana Mackenzie, Rua da Consolacao 896, CEP: 01302-907 Sao Paulo, Sao Paulo (Brazil)

2012-12-15

395

Use of model-based compartmental analysis to study vitamin A kinetics and metabolism.  

PubMed

We discuss the use of mathematical modeling, and specifically model-based compartmental analysis, to analyze vitamin A kinetic data obtained in rat and human studies over the past 25 years. Following an overview of whole-body vitamin A metabolism, a review of early kinetic studies, and an introduction to the approach and terminology of compartmental analysis, we summarize studies done in this laboratory to develop models of whole-body vitamin A metabolism in rats at varying levels of vitamin A status. Highlights of the results of these studies include the extensive recycling of vitamin A among plasma and tissues before irreversible utilization and the existence of significant extrahepatic pools of the vitamin. Our studies also document important differences in vitamin A kinetics as a function of vitamin A status and the importance of plasma retinol pool size in vitamin A utilization rate. Later we describe vitamin A kinetics and models developed for specific organs including the liver, eyes, kidneys, small intestine, lungs, testes, adrenals, and remaining carcass, and we discuss the effects of various exogenous factors (e.g., 4-HPR, dioxin, iron deficiency, dietary retinoic acid, and inflammation) on vitamin A dynamics. We also briefly review the retrospective application of model-based compartmental analysis to human vitamin A kinetic data. Overall, we conclude that the application of model-based compartmental analysis to vitamin A kinetic data provides unique insights into both quantitative and descriptive aspects of vitamin A metabolism and homeostasis in the intact animal. PMID:17368316

Cifelli, Christopher J; Green, Joanne Balmer; Green, Michael H

2007-01-01

396

Descriptive Epidemiology  

Cancer.gov

Descriptive epidemiology studies characterize cancer incidence and mortality temporal trends, age-specific rates, geographic distribution of cancer, race and ethnic differences in cancer rates, and birth cohort effects.

397

Descriptive statistics.  

PubMed

In this article, we introduced basic concepts of statistics, type of distributions, and descriptive statistics. A few examples were also provided. The basic concepts presented herein are only a fraction of the concepts related to descriptive statistics. Also, there are many commonly used distributions not presented herein, such as Poisson distributions for rare events and exponential distributions, F distributions, and logistic distributions. More information can be found in many statistics books and publications. PMID:19891281

Shi, Runhua; McLarty, Jerry W

2009-10-01

398

The complete relativistic kinetic model of violation of symmetry in isotopic expanding plasma and production of baryons in hot Universe. II. Numerical model: X-boson distribution function  

E-print Network

In terms of proposed by authors general-relativistic kinetic model of baryon production in expanding primordially symmetrical hot Universe calculates distribution function of extra-massive bosons and concerned with it variables.

Yu. G. Ignatyev; K. Alsmadi

2010-12-27

399

Dusty plasmas  

SciTech Connect

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

400

Dusty Plasma Laboratory  

NSDL National Science Digital Library

The DPL studies micron size solid objects immersed in a plasma consisting of electrons, ions, and neutrals. A description of experiments and applications is provided in addition to a list of online plasma research resources.

Spann, James

2003-10-10

401

Thermal plasma processing  

Microsoft Academic Search

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

402

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

403

Fluid modeling for ion scale space plasmas  

NASA Astrophysics Data System (ADS)

Fluid models with first-order finite Larmor radius (FLR) corrections have been known since