Electromagnetic nonlinear gyrokinetics with polarization drift
International Nuclear Information System (INIS)
Duthoit, F.-X.; Hahm, T. S.; Wang, Lu
2014-01-01
A set of new nonlinear electromagnetic gyrokinetic Vlasov equation with polarization drift and gyrokinetic Maxwell equations is systematically derived by using the Lie-transform perturbation method in toroidal geometry. For the first time, we recover the drift-kinetic expression for parallel acceleration [R. M. Kulsrud, in Basic Plasma Physics, edited by A. A. Galeev and R. N. Sudan (North-Holland, Amsterdam, 1983)] from the nonlinear gyrokinetic equations, thereby bridging a gap between the two formulations. This formalism should be useful in addressing nonlinear ion Compton scattering of intermediate-mode-number toroidal Alfvén eigenmodes for which the polarization current nonlinearity [T. S. Hahm and L. Chen, Phys. Rev. Lett. 74, 266 (1995)] and the usual finite Larmor radius effects should compete
Nonlinear electromagnetic gyrokinetic equations for rotating axisymmetric plasmas
International Nuclear Information System (INIS)
Artun, M.; Tang, W.M.
1994-03-01
The influence of sheared equilibrium flows on the confinement properties of tokamak plasmas is a topic of much current interest. A proper theoretical foundation for the systematic kinetic analysis of this important problem has been provided here by presented the derivation of a set of nonlinear electromagnetic gyrokinetic equations applicable to low frequency microinstabilities in a rotating axisymmetric plasma. The subsonic rotation velocity considered is in the direction of symmetry with the angular rotation frequency being a function of the equilibrium magnetic flux surface. In accordance with experimental observations, the rotation profile is chosen to scale with the ion temperature. The results obtained represent the shear flow generalization of the earlier analysis by Frieman and Chen where such flows were not taken into account. In order to make it readily applicable to gyrokinetic particle simulations, this set of equations is cast in a phase-space-conserving continuity equation form
Fully Electromagnetic Nonlinear Gyrokinetic Equations for Tokamak Edge Turbulence
International Nuclear Information System (INIS)
Hahm, T.S.; Wang, Lu; Madsen, J.
2008-01-01
An energy conserving set of the fully electromagnetic nonlinear gyrokinetic Vlasov equation and Maxwell's equations, which is applicable to both L-mode turbulence with large amplitude and H-mode turbulence in the presence of high E x B shear has been derived. The phase-space action variational Lie perturbation method ensures the preservation of the conservation laws of the underlying Vlasov-Maxwell system. Our generalized ordering takes ρ i θi ∼ L E ∼ L p i is the thermal ion Larmor radius and ρ θi = B/B θ ρ i ), as typically observed in the tokamak H-mode edge, with L E and L p being the radial electric field and pressure gradient lengths. We take k # perpendicular# ρ i ∼ 1 for generality, and keep the relative fluctuation amplitudes e(delta)φ/T i ∼ (delta)B/B up to the second order. Extending the electrostatic theory in the presence of high E x B shear [Hahm, Phys. Plasmas 3, 4658 (1996)], contributions of electromagnetic fluctuations to the particle charge density and current are explicitly evaluated via pull-back transformation from the gyrocenter distribution function in the gyrokinetic Maxwell's equation
Nonlinear gyrokinetic equations for low-frequency electromagnetic waves in general plasma equilibria
International Nuclear Information System (INIS)
Frieman, E.A.; Chen, L.
1981-10-01
A nonlinear gyrokinetic formalism for low-frequency (less than the cyclotron frequency) microscopic electromagnetic perturbations in general magnetic field configurations is developed. The nonlinear equations thus derived are valid in the strong-turbulence regime and contain effects due to finite Larmor radius, plasma inhomogeneities, and magentic field geometries. The specific case of axisymmetric tokamaks is then considered, and a model nonlinear equation is derived for electrostatic drift waves. Also, applying the formalism to the shear Alfven wave heating sceme, it is found that nonlinear ion Landau damping of kinetic shear-Alfven waves is modified, both qualitatively and quantitatively, by the diamagnetic drift effects. In particular, wave energy is found to cascade in wavenumber instead of frequency
Nonlinear gyrokinetic Maxwell-Vlasov equations using magnetic coordinates
International Nuclear Information System (INIS)
Brizard, A.
1988-09-01
A gyrokinetic formalism using magnetic coordinates is used to derive self-consistent, nonlinear Maxwell-Vlasov equations that are suitable for particle simulation studies of finite-β tokamak microturbulence and its associated anomalous transport. The use of magnetic coordinates is an important feature of this work as it introduces the toroidal geometry naturally into our gyrokinetic formalism. The gyrokinetic formalism itself is based on the use of the Action-variational Lie perturbation method of Cary and Littlejohn, and preserves the Hamiltonian structure of the original Maxwell-Vlasov system. Previous nonlinear gyrokinetic sets of equations suitable for particle simulation analysis have considered either electrostatic and shear-Alfven perturbations in slab geometry, or electrostatic perturbations in toroidal geometry. In this present work, fully electromagnetic perturbations in toroidal geometry are considered. 26 refs
Variational principle for nonlinear gyrokinetic Vlasov--Maxwell equations
International Nuclear Information System (INIS)
Brizard, Alain J.
2000-01-01
A new variational principle for the nonlinear gyrokinetic Vlasov--Maxwell equations is presented. This Eulerian variational principle uses constrained variations for the gyrocenter Vlasov distribution in eight-dimensional extended phase space and turns out to be simpler than the Lagrangian variational principle recently presented by H. Sugama [Phys. Plasmas 7, 466 (2000)]. A local energy conservation law is then derived explicitly by the Noether method. In future work, this new variational principle will be used to derive self-consistent, nonlinear, low-frequency Vlasov--Maxwell bounce-gyrokinetic equations, in which the fast gyromotion and bounce-motion time scales have been eliminated
Linear and nonlinear verification of gyrokinetic microstability codes
Bravenec, R. V.; Candy, J.; Barnes, M.; Holland, C.
2011-12-01
Verification of nonlinear microstability codes is a necessary step before comparisons or predictions of turbulent transport in toroidal devices can be justified. By verification we mean demonstrating that a code correctly solves the mathematical model upon which it is based. Some degree of verification can be accomplished indirectly from analytical instability threshold conditions, nonlinear saturation estimates, etc., for relatively simple plasmas. However, verification for experimentally relevant plasma conditions and physics is beyond the realm of analytical treatment and must rely on code-to-code comparisons, i.e., benchmarking. The premise is that the codes are verified for a given problem or set of parameters if they all agree within a specified tolerance. True verification requires comparisons for a number of plasma conditions, e.g., different devices, discharges, times, and radii. Running the codes and keeping track of linear and nonlinear inputs and results for all conditions could be prohibitive unless there was some degree of automation. We have written software to do just this and have formulated a metric for assessing agreement of nonlinear simulations. We present comparisons, both linear and nonlinear, between the gyrokinetic codes GYRO [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] and GS2 [W. Dorland, F. Jenko, M. Kotschenreuther, and B. N. Rogers, Phys. Rev. Lett. 85, 5579 (2000)]. We do so at the mid-radius for the same discharge as in earlier work [C. Holland, A. E. White, G. R. McKee, M. W. Shafer, J. Candy, R. E. Waltz, L. Schmitz, and G. R. Tynan, Phys. Plasmas 16, 052301 (2009)]. The comparisons include electromagnetic fluctuations, passing and trapped electrons, plasma shaping, one kinetic impurity, and finite Debye-length effects. Results neglecting and including electron collisions (Lorentz model) are presented. We find that the linear frequencies with or without collisions agree well between codes, as do the time averages of
Nonlinear Gyrokinetic Theory With Polarization Drift
International Nuclear Information System (INIS)
Wang, L.; Hahm, T.S.
2010-01-01
A set of the electrostatic toroidal gyrokinetic Vlasov equation and the Poisson equation, which explicitly includes the polarization drift, is derived systematically by using Lie-transform method. The polarization drift is introduced in the gyrocenter equations of motion, and the corresponding polarization density is derived. Contrary to the wide-spread expectation, the inclusion of the polarization drift in the gyrocenter equations of motion does not affect the expression for the polarization density significantly. This is due to modification of the gyrocenter phase-space volume caused by the electrostatic potential [T. S. Hahm, Phys. Plasmas 3, 4658 (1996)].
International Nuclear Information System (INIS)
Sugama, H.
1999-08-01
The Lagrangian formulation of the gyrokinetic theory is generalized in order to describe the particles' dynamics as well as the self-consistent behavior of the electromagnetic fields. The gyrokinetic equation for the particle distribution function and the gyrokinetic Maxwell's equations for the electromagnetic fields are both derived from the variational principle for the Lagrangian consisting of the parts of particles, fields, and their interaction. In this generalized Lagrangian formulation, the energy conservation property for the total nonlinear gyrokinetic system of equations is directly shown from the Noether's theorem. This formulation can be utilized in order to derive the nonlinear gyrokinetic system of equations and the rigorously conserved total energy for fluctuations with arbitrary frequency. (author)
Effects of Plasma Shaping on Nonlinear Gyrokinetic Turbulence
Energy Technology Data Exchange (ETDEWEB)
Belli, E. A. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Hammett, G. W. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Dorland, W. [Univ. of Maryland, College Park, MD (United States)
2008-08-01
The effects of flux surface shape on the gyrokinetic stability and transport of tokamak plasmas are studied using the GS2 code [M. Kotschenreuther, G. Rewoldt, and W.M. Tang, Comput. Phys. Commun. 88, 128 (1995); W. Dorland, F. Jenko, M. Kotschenreuther, and B.N. Rogers, Phys. Rev. Lett. 85, 5579 (2000)]. Studies of the scaling of nonlinear turbulence with shaping parameters are performed using analytic equilibria based on interpolations of representative shapes of the Joint European Torus (JET) [P.H. Rebut and B.E. Keen, Fusion Technol. 11, 13 (1987)]. High shaping is found to be a stabilizing influence on both the linear ion-temperature-gradient (ITG) instability and the nonlinear ITG turbulence. For the parameter regime studied here, a scaling of the heat flux with elongation of χ ~ κ^{-1.5} or κ^{-2.0}, depending on the triangularity, is observed at fixed average temperature gradient. While this is not as strong as empirical elongation scalings, it is also found that high shaping results in a larger Dimits upshift of the nonlinear critical temperature gradient due to an enhancement of the Rosenbluth-Hinton residual zonal flows.
Effects of Plasma Shaping on Nonlinear Gyrokinetic Turbulence
International Nuclear Information System (INIS)
E.A. Belli, G.W. Hammett and W. Dorland
2008-01-01
The effects of flux surface shape on the gyrokinetic stability and transport of tokamak plasmas are studied using the GS2 code [M. Kotschenreuther, G. Rewoldt, and W.M. Tang, Comput. Phys. Commun. 88, 128 (1995); W. Dorland, F. Jenko, M. Kotschenreuther, and B.N. Rogers, Phys. Rev. Lett. 85, 5579 (2000)]. Studies of the scaling of nonlinear turbulence with shaping parameters are performed using analytic equilibria based on interpolations of representative shapes of the Joint European Torus (JET) [P.H. Rebut and B.E. Keen, Fusion Technol. 11, 13 (1987)]. High shaping is found to be a stabilizing influence on both the linear ion-temperature-gradient (ITG) instability and the nonlinear ITG turbulence. For the parameter regime studied here, a scaling of the heat flux with elongation of χ ∼ κ -1.5 or κ -2.0 , depending on the triangularity, is observed at fixed average temperature gradient. While this is not as strong as empirical elongation scalings, it is also found that high shaping results in a larger Dimits upshift of the nonlinear critical temperature gradient due to an enhancement of the Rosenbluth-Hinton residual zonal flows
Nonlinear surface electromagnetic phenomena
Ponath, H-E
1991-01-01
In recent years the physics of electromagnetic surface phenomena has developed rapidly, evolving into technologies for communications and industry, such as fiber and integrated optics. The variety of phenomena based on electromagnetism at surfaces is rich and this book was written with the aim of summarizing the available knowledge in selected areas of the field. The book contains reviews written by solid state and optical physicists on the nonlinear interaction of electromagnetic waves at and with surfaces and films. Both the physical phenomena and some potential applications are
Energy Technology Data Exchange (ETDEWEB)
Weir, G. M.; Faber, B. J.; Likin, K. M.; Talmadge, J. N.; Anderson, D. T.; Anderson, F. S. B. [HSX Plasma Laboratory, University of Wisconsin–Madison, Madison, Wisconsin 53706 (United States)
2015-05-15
Stiffness measurements are presented in the quasi-helically symmetric experiment (HSX), in which the neoclassical transport is comparable to that in a tokamak and turbulent transport dominates throughout the plasma. Electron cyclotron emission is used to measure the local electron temperature response to modulated electron cyclotron resonant heating. The amplitude and phase of the heat wave through the steep electron temperature gradient (ETG) region of the plasma are used to determine a transient electron thermal diffusivity that is close to the steady-state diffusivity. The low stiffness in the region between 0.2 ≤ r/a ≤ 0.4 agrees with the scaling of the steady-state heat flux with temperature gradient in this region. These experimental results are compared to gyrokinetic calculations in a flux-tube geometry using the gyrokinetic electromagnetic numerical experiment code with two kinetic species. Linear simulations show that the ETG mode may be experimentally relevant within r/a ≤ 0.2, while the Trapped Electron Mode (TEM) is the dominant long-wavelength microturbulence instability across most of the plasma. The TEM is primarily driven by the density gradient. Non-linear calculations of the saturated heat flux driven by the TEM and ETG bracket the experimental heat flux.
Nonlinear Gyrokinetics: A Powerful Tool for the Description of Microturbulence in Magnetized Plasmas
International Nuclear Information System (INIS)
Krommes, John E.
2010-01-01
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.
Nonlinear gyrokinetics: a powerful tool for the description of microturbulence in magnetized plasmas
International Nuclear Information System (INIS)
Krommes, John A
2010-01-01
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 difficulties) of deriving nonlinear gyrofluid 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.
Gyrokinetic energy conservation and Poisson-bracket formulation
International Nuclear Information System (INIS)
Brizard, A.
1989-01-01
An integral expression for the gyrokinetic total energy of a magnetized plasma, with general magnetic field configuration perturbed by fully electromagnetic fields, was recently derived through the use of a gyrocenter Lie transformation. It is shown that the gyrokinetic energy is conserved by the gyrokinetic Hamiltonian flow to all orders in perturbed fields. An explicit demonstration that a gyrokinetic Hamiltonian containing quadratic nonlinearities preserves the gyrokinetic energy up to third order is given. The Poisson-bracket formulation greatly facilitates this demonstration with the help of the Jacobi identity and other properties of the Poisson brackets
International Nuclear Information System (INIS)
Villard, L.; Allfrey, S.J.; Bottino, A.
2003-01-01
The aim of this paper is to report on recent advances made on global gyrokinetic simulations of Ion Temperature Gradient modes (ITG) and other microinstabilities. The nonlinear development and saturation of ITG modes and the role of E x B zonal flows are studied with a global nonlinear δ f formulation that retains parallel nonlinearity and thus allows for a check of the energy conservation property as a means to verify the quality of the numerical simulation. Due to an optimised loading technique the conservation property is satisfied with an unprecedented quality well into the nonlinear stage. The zonal component of the perturbation establishes a quasi-steady state with regions of ITG suppression, strongly reduced radial energy flux and steepened effective temperature profile alternating with regions of higher ITG mode amplitudes, larger radial energy flux and flattened effective temperature profile. A semi-Lagrangian approach free of statistical noise is proposed as an alternative to the nonlinear δf formulation. An ASDEX-Upgrade experiment with an Internal Transport Barrier (ITB) is analysed with a global gyrokinetic code that includes trapped electron dynamics. The weakly destabilizing effect of trapped electron dynamics on ITG modes in an axisymmetric bumpy configuration modelling W7-X is shown in global linear simulations that retain the full electron dynamics. Finite β effects on microinstabilities are investigated with a linear global spectral electromagnetic gyrokinetic formulation. The radial global structure of electromagnetic modes shows a resonant behaviour with rational q values. (author)
Energy Technology Data Exchange (ETDEWEB)
White, A. E., E-mail: whitea@mit.edu; Howard, N. T.; Creely, A. J.; Chilenski, M. A.; Greenwald, M.; Hubbard, A. E.; Hughes, J. W.; Marmar, E.; Rice, J. E.; Sierchio, J. M.; Sung, C.; Walk, J. R.; Whyte, D. G. [MIT Plasma Science and Fusion Center, Cambridge, Massachusetts 02139 (United States); Mikkelsen, D. R.; Edlund, E. M.; Kung, C. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08540 (United States); Holland, C. [University of California, San Diego (UCSD) San Diego, California 92093 (United States); Candy, J.; Petty, C. C. [General Atomics, P.O. Box 85608, San Diego, California 92186 (United States); Reinke, M. L. [York University, Heslington, York YO10 5DD (United Kingdom); and others
2015-05-15
For the first time, nonlinear gyrokinetic simulations of I-mode plasmas are performed and compared with experiment. I-mode is a high confinement regime, featuring energy confinement similar to H-mode, but without enhanced particle and impurity particle confinement [D. G. Whyte et al., Nucl. Fusion 50, 105005 (2010)]. As a consequence of the separation between heat and particle transport, I-mode exhibits several favorable characteristics compared to H-mode. The nonlinear gyrokinetic code GYRO [J. Candy and R. E. Waltz, J Comput. Phys. 186, 545 (2003)] is used to explore the effects of E × B shear and profile stiffness in I-mode and compare with L-mode. The nonlinear GYRO simulations show that I-mode core ion temperature and electron temperature profiles are more stiff than L-mode core plasmas. Scans of the input E × B shear in GYRO simulations show that E × B shearing of turbulence is a stronger effect in the core of I-mode than L-mode. The nonlinear simulations match the observed reductions in long wavelength density fluctuation levels across the L-I transition but underestimate the reduction of long wavelength electron temperature fluctuation levels. The comparisons between experiment and gyrokinetic simulations for I-mode suggest that increased E × B shearing of turbulence combined with increased profile stiffness are responsible for the reductions in core turbulence observed in the experiment, and that I-mode resembles H-mode plasmas more than L-mode plasmas with regards to marginal stability and temperature profile stiffness.
Nonlinear classical theory of electromagnetism
International Nuclear Information System (INIS)
Pisello, D.
1977-01-01
A topological theory of electric charge is given. Einstein's criteria for the completion of classical electromagnetic theory are summarized and their relation to quantum theory and the principle of complementarity is indicated. The inhibiting effect that this principle has had on the development of physical thought is discussed. Developments in the theory of functions on nonlinear spaces provide the conceptual framework required for the completion of electromagnetism. The theory is based on an underlying field which is a continuous mapping of space-time into points on the two-sphere. (author)
Nonlinear Electromagnetic Stabilization of Plasma Microturbulence
Whelan, G. G.; Pueschel, M. J.; Terry, P. W.
2018-04-01
The physical causes for the strong stabilizing effect of finite plasma β on ion-temperature-gradient-driven turbulence, which far exceeds quasilinear estimates, are identified from nonlinear gyrokinetic simulations. The primary contribution stems from a resonance of frequencies in the dominant nonlinear interaction between the unstable mode, the stable mode, and zonal flows, which maximizes the triplet correlation time and therefore the energy transfer efficiency. A modification to mixing-length transport estimates is constructed, which reproduces nonlinear heat fluxes throughout the examined β range.
Gyrokinetic simulation of finite-β plasmas on parallel architectures
International Nuclear Information System (INIS)
Reynders, J.V.W.
1993-01-01
Much research exists on the linear and non-linear properties of plasma microinstabilities induced by density and temperature gradients. There has been an interest in the electromagnetic or finite-β effects on these microinstabilities. This thesis focuses on the finite-β modification of an ion temperature gradient (ITG) driven microinstability in a two-dimensional shearless and sheared-slab geometries. A gyrokinetic model is employed in the numerical and analytic studies of this instability. Chapter 1 introduces the electromagnetic gyrokinetic model employed in the numerical and analytic studies of the ITG instability. Some discussion of the Klimontovich particle representation of the gyrokinetic Vlasov equation and a multiple scale model of the background plasma gradient is presented. Chapter 2 details the computational issues facing an electromagnetic gyrokinetic particle simulation of the ITG mode. An electromagnetic extension of the partially linearized algorithm is presented with a comparison of quiet particle initialization routines. Chapter 3 presents and compares algorithms for the gyrokinetic particle simulation technique on SIMD and MIMD computing platforms. Chapter 4 discusses electromagnetic gyrokinetic fluctuation theory and provides a comparison of analytic and numerical results. Chapter 5 contains a linear and a non-linear three-wave coupling analysis of the finite-β modified ITG mode in a shearless slab geometry. Comparisons are made with linear and partially linearized gyrokinetic simulation results. Chapter 6 presents results from a finite-β modified ITG mode in a sheared slab geometry. The linear dispersion relation is derived and results from an integral eigenvalue code are presented. Comparisons are made with the gyrokinetic particle code in a variety of limits with both adiabatic and non-adiabatic electrons. Evidence of ITG driven microtearing is presented
Non-linear gyrokinetic simulations of microturbulence in TCV electron internal transport barriers
Energy Technology Data Exchange (ETDEWEB)
Lapillonne, X; Brunner, S; Sauter, O; Villard, L [Centre de Recherches en Physique des Plasmas, Association EURATOM-Confederation Suisse, Ecole Polytechnique Federale de Lausanne, CH-1015 Lausanne (Switzerland); Fable, E; Goerler, T; Jenko, F; Merz, F, E-mail: stephan.brunner@epfl.ch [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstrasse 2, D-85748 Garching (Germany)
2011-05-15
Using the local (flux-tube) version of the Eulerian code GENE (Jenko et al 2000 Phys. Plasmas 7 1904), gyrokinetic simulations of microturbulence were carried out considering parameters relevant to electron-internal transport barriers (e-ITBs) in the TCV tokamak (Sauter et al 2005 Phys. Rev. Lett. 94 105002), generated under conditions of low or negative shear. For typical density and temperature gradients measured in such barriers, the corresponding simulated fluctuation spectra appears to simultaneously contain longer wavelength trapped electron modes (TEMs, for typically k{sub p}erpendicular{rho}{sub i} < 0.5, k{sub p}erpendicular being the characteristic perpendicular wavenumber and {rho}{sub i} the ion Larmor radius) and shorter wavelength ion temperature gradient modes (ITG, k{sub p}erpendicular{rho}{sub i} > 0.5). The contributions to the electron particle flux from these two types of modes are, respectively, outward/inward and may cancel each other for experimentally realistic gradients. This mechanism may partly explain the feasibility of e-ITBs. The non-linear simulation results confirm the predictions of a previously developed quasi-linear model (Fable et al 2010 Plasma Phys. Control. Fusion 52 015007), namely that the stationary condition of zero particle flux is obtained through the competitive contributions of ITG and TEM. A quantitative comparison of the electron heat flux with experimental estimates is presented as well.
Non-linear gyrokinetic simulations of microturbulence in TCV electron internal transport barriers
Lapillonne, X.; Brunner, S.; Sauter, O.; Villard, L.; Fable, E.; Görler, T.; Jenko, F.; Merz, F.
2011-05-01
Using the local (flux-tube) version of the Eulerian code GENE (Jenko et al 2000 Phys. Plasmas 7 1904), gyrokinetic simulations of microturbulence were carried out considering parameters relevant to electron-internal transport barriers (e-ITBs) in the TCV tokamak (Sauter et al 2005 Phys. Rev. Lett. 94 105002), generated under conditions of low or negative shear. For typical density and temperature gradients measured in such barriers, the corresponding simulated fluctuation spectra appears to simultaneously contain longer wavelength trapped electron modes (TEMs, for typically k⊥ρi 0.5). The contributions to the electron particle flux from these two types of modes are, respectively, outward/inward and may cancel each other for experimentally realistic gradients. This mechanism may partly explain the feasibility of e-ITBs. The non-linear simulation results confirm the predictions of a previously developed quasi-linear model (Fable et al 2010 Plasma Phys. Control. Fusion 52 015007), namely that the stationary condition of zero particle flux is obtained through the competitive contributions of ITG and TEM. A quantitative comparison of the electron heat flux with experimental estimates is presented as well.
Nonlinear electromagnetic susceptibilities of unmagnetized plasmas
International Nuclear Information System (INIS)
Yoon, Peter H.
2005-01-01
Fully electromagnetic nonlinear susceptibilities of unmagnetized plasmas are analyzed in detail. Concrete expressions of the second-order nonlinear susceptibility are found in various forms in the literature, usually in connection with the discussions of various three-wave decay processes, but the third-order susceptibilities are rarely discussed. The second-order susceptibility is pertinent to nonlinear wave-wave interactions (i.e., the decay/coalescence), whereas the third-order susceptibilities affect nonlinear wave-particle interactions (i.e., the induced scattering). In the present article useful approximate analytical expressions of these nonlinear susceptibilities that can be readily utilized in various situations are derived
Energy Technology Data Exchange (ETDEWEB)
Hager, Robert, E-mail: rhager@pppl.gov; Chang, C. S., E-mail: cschang@pppl.gov [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States)
2016-04-15
As a follow-up on the drift-kinetic study of the non-local bootstrap current in the steep edge pedestal of tokamak plasma by Koh et al. [Phys. Plasmas 19, 072505 (2012)], a gyrokinetic neoclassical study is performed with gyrokinetic ions and drift-kinetic electrons. Besides the gyrokinetic improvement of ion physics from the drift-kinetic treatment, a fully non-linear Fokker-Planck collision operator—that conserves mass, momentum, and energy—is used instead of Koh et al.'s linearized collision operator in consideration of the possibility that the ion distribution function is non-Maxwellian in the steep pedestal. An inaccuracy in Koh et al.'s result is found in the steep edge pedestal that originated from a small error in the collisional momentum conservation. The present study concludes that (1) the bootstrap current in the steep edge pedestal is generally smaller than what has been predicted from the small banana-width (local) approximation [e.g., Sauter et al., Phys. Plasmas 6, 2834 (1999) and Belli et al., Plasma Phys. Controlled Fusion 50, 095010 (2008)], (2) the plasma flow evaluated from the local approximation can significantly deviate from the non-local results, and (3) the bootstrap current in the edge pedestal, where the passing particle region is small, can be dominantly carried by the trapped particles in a broad trapped boundary layer. A new analytic formula based on numerous gyrokinetic simulations using various magnetic equilibria and plasma profiles with self-consistent Grad-Shafranov solutions is constructed.
SPARSE ELECTROMAGNETIC IMAGING USING NONLINEAR LANDWEBER ITERATIONS
Desmal, Abdulla
2015-07-29
A scheme for efficiently solving the nonlinear electromagnetic inverse scattering problem on sparse investigation domains is described. The proposed scheme reconstructs the (complex) dielectric permittivity of an investigation domain from fields measured away from the domain itself. Least-squares data misfit between the computed scattered fields, which are expressed as a nonlinear function of the permittivity, and the measured fields is constrained by the L0/L1-norm of the solution. The resulting minimization problem is solved using nonlinear Landweber iterations, where at each iteration a thresholding function is applied to enforce the sparseness-promoting L0/L1-norm constraint. The thresholded nonlinear Landweber iterations are applied to several two-dimensional problems, where the ``measured\\'\\' fields are synthetically generated or obtained from actual experiments. These numerical experiments demonstrate the accuracy, efficiency, and applicability of the proposed scheme in reconstructing sparse profiles with high permittivity values.
White, A E; Schmitz, L; Peebles, W A; Carter, T A; Rhodes, T L; Doyle, E J; Gourdain, P A; Hillesheim, J C; Wang, G; Holland, C; Tynan, G R; Austin, M E; McKee, G R; Shafer, M W; Burrell, K H; Candy, J; DeBoo, J C; Prater, R; Staebler, G M; Waltz, R E; Makowski, M A
2008-10-01
A correlation electron cyclotron emission (CECE) diagnostic has been used to measure local, turbulent fluctuations of the electron temperature in the core of DIII-D plasmas. This paper describes the hardware and testing of the CECE diagnostic and highlights the importance of measurements of multifield fluctuation profiles for the testing and validation of nonlinear gyrokinetic codes. The process of testing and validating such codes is critical for extrapolation to next-step fusion devices. For the first time, the radial profiles of electron temperature and density fluctuations are compared to nonlinear gyrokinetic simulations. The CECE diagnostic at DIII-D uses correlation radiometry to measure the rms amplitude and spectrum of the electron temperature fluctuations. Gaussian optics are used to produce a poloidal spot size with w(o) approximately 1.75 cm in the plasma. The intermediate frequency filters and the natural linewidth of the EC emission determine the radial resolution of the CECE diagnostic, which can be less than 1 cm. Wavenumbers resolved by the CECE diagnostic are k(theta) < or = 1.8 cm(-1) and k(r) < or = 4 cm(-1), relevant for studies of long-wavelength turbulence associated with the trapped electron mode and the ion temperature gradient mode. In neutral beam heated L-mode plasmas, core electron temperature fluctuations in the region 0.5 < r/a < 0.9, increase with radius from approximately 0.5% to approximately 2%, similar to density fluctuations that are measured simultaneously with beam emission spectroscopy. After incorporating "synthetic diagnostics" to effectively filter the code output, the simulations reproduce the characteristics of the turbulence and transport at one radial location r/a = 0.5, but not at a second location, r/a = 0.75. These results illustrate that measurements of the profiles of multiple fluctuating fields can provide a significant constraint on the turbulence models employed by the code.
Sparse Reconstruction Schemes for Nonlinear Electromagnetic Imaging
Desmal, Abdulla
2016-03-01
Electromagnetic imaging is the problem of determining material properties from scattered fields measured away from the domain under investigation. Solving this inverse problem is a challenging task because (i) it is ill-posed due to the presence of (smoothing) integral operators used in the representation of scattered fields in terms of material properties, and scattered fields are obtained at a finite set of points through noisy measurements; and (ii) it is nonlinear simply due the fact that scattered fields are nonlinear functions of the material properties. The work described in this thesis tackles the ill-posedness of the electromagnetic imaging problem using sparsity-based regularization techniques, which assume that the scatterer(s) occupy only a small fraction of the investigation domain. More specifically, four novel imaging methods are formulated and implemented. (i) Sparsity-regularized Born iterative method iteratively linearizes the nonlinear inverse scattering problem and each linear problem is regularized using an improved iterative shrinkage algorithm enforcing the sparsity constraint. (ii) Sparsity-regularized nonlinear inexact Newton method calls for the solution of a linear system involving the Frechet derivative matrix of the forward scattering operator at every iteration step. For faster convergence, the solution of this matrix system is regularized under the sparsity constraint and preconditioned by leveling the matrix singular values. (iii) Sparsity-regularized nonlinear Tikhonov method directly solves the nonlinear minimization problem using Landweber iterations, where a thresholding function is applied at every iteration step to enforce the sparsity constraint. (iv) This last scheme is accelerated using a projected steepest descent method when it is applied to three-dimensional investigation domains. Projection replaces the thresholding operation and enforces the sparsity constraint. Numerical experiments, which are carried out using
Energy Technology Data Exchange (ETDEWEB)
Sung, C., E-mail: csung@physics.ucla.edu [University of California, Los Angeles, Los Angeles, California 90095 (United States); White, A. E.; Greenwald, M.; Howard, N. T. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Mikkelsen, D. R.; Churchill, R. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States); Holland, C. [University of California, San Diego, La Jolla, California 92093 (United States); Theiler, C. [Ecole Polytechnique Fédérale de Lausanne, SPC, Lausanne 1015 (Switzerland)
2016-04-15
Long wavelength turbulent electron temperature fluctuations (k{sub y}ρ{sub s} < 0.3) are measured in the outer core region (r/a > 0.8) of Ohmic L-mode plasmas at Alcator C-Mod [E. S. Marmar et al., Nucl. Fusion 49, 104014 (2009)] with a correlation electron cyclotron emission diagnostic. The relative amplitude and frequency spectrum of the fluctuations are compared quantitatively with nonlinear gyrokinetic simulations using the GYRO code [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] in two different confinement regimes: linear Ohmic confinement (LOC) regime and saturated Ohmic confinement (SOC) regime. When comparing experiment with nonlinear simulations, it is found that local, electrostatic ion-scale simulations (k{sub y}ρ{sub s} ≲ 1.7) performed at r/a ∼ 0.85 reproduce the experimental ion heat flux levels, electron temperature fluctuation levels, and frequency spectra within experimental error bars. In contrast, the electron heat flux is robustly under-predicted and cannot be recovered by using scans of the simulation inputs within error bars or by using global simulations. If both the ion heat flux and the measured temperature fluctuations are attributed predominantly to long-wavelength turbulence, then under-prediction of electron heat flux strongly suggests that electron scale turbulence is important for transport in C-Mod Ohmic L-mode discharges. In addition, no evidence is found from linear or nonlinear simulations for a clear transition from trapped electron mode to ion temperature gradient turbulence across the LOC/SOC transition, and also there is no evidence in these Ohmic L-mode plasmas of the “Transport Shortfall” [C. Holland et al., Phys. Plasmas 16, 052301 (2009)].
Spatiotemporal electromagnetic soliton and spatial ring formation in nonlinear metamaterials
International Nuclear Information System (INIS)
Zhang Jinggui; Wen Shuangchun; Xiang Yuanjiang; Wang Youwen; Luo Hailu
2010-01-01
We present a systematic investigation of ultrashort electromagnetic pulse propagation in metamaterials (MMs) with simultaneous cubic electric and magnetic nonlinearity. We predict that spatiotemporal electromagnetic solitons may exist in the positive-index region of a MM with focusing nonlinearity and anomalous group velocity dispersion (GVD), as well as in the negative-index region of the MM with defocusing nonlinearity and normal GVD. The experimental circumstances for generating and manipulating spatiotemporal electromagnetic solitons can be created by elaborating appropriate MMs. In addition, we find that, in the negative-index region of a MM, a spatial ring may be formed as the electromagnetic pulse propagates for focusing nonlinearity and anomalous GVD; while the phenomenon of temporal splitting of the electromagnetic pulse may appear for the same case except for the defocusing nonlinearity. Finally, we demonstrate that the nonlinear magnetization makes the sign of effective electric nonlinear effect switchable due to the combined action of electric and magnetic nonlinearity, exerting a significant influence on the propagation of electromagnetic pulses.
PLASMA EMISSION BY NONLINEAR ELECTROMAGNETIC PROCESSES
Energy Technology Data Exchange (ETDEWEB)
Ziebell, L. F.; Petruzzellis, L. T.; Gaelzer, R. [Instituto de Física, UFRGS, Porto Alegre, RS (Brazil); Yoon, P. H. [Institute for Physical Science and Technology, University of Maryland, College Park (United States); Pavan, J., E-mail: luiz.ziebell@ufrgs.br, E-mail: laripetruzzellis@yahoo.com.br, E-mail: rudi.gaelzer@ufrgs.br, E-mail: yoonp@umd.edu, E-mail: joel.pavan@ufpel.edu.br [Instituto de Física e Matemática, UFPel, Pelotas, RS (Brazil)
2015-06-20
The plasma emission, or electromagnetic (EM) radiation at the plasma frequency and/or its harmonic(s), is generally accepted as the radiation mechanism responsible for solar type II and III radio bursts. Identification and characterization of these solar radio burst phenomena were done in the 1950s. Despite many decades of theoretical research since then, a rigorous demonstration of the plasma emission process based upon first principles was not available until recently, when, in a recent Letter, Ziebell et al. reported the first complete numerical solution of EM weak turbulence equations; thus, quantitatively analyzing the plasma emission process starting from the initial electron beam and the associated beam-plasma (or Langmuir wave) instability, as well as the subsequent nonlinear conversion of electrostatic Langmuir turbulence into EM radiation. In the present paper, the same problem is revisited in order to elucidate the detailed physical mechanisms that could not be reported in the brief Letter format. Findings from the present paper may be useful for interpreting observations and full-particle numerical simulations.
Analytic descriptions of cylindrical electromagnetic waves in a nonlinear medium
Xiong, Hao; Si, Liu-Gang; Yang, Xiaoxue; Wu, Ying
2015-01-01
A simple but highly efficient approach for dealing with the problem of cylindrical electromagnetic waves propagation in a nonlinear medium is proposed based on an exact solution proposed recently. We derive an analytical explicit formula, which exhibiting rich interesting nonlinear effects, to describe the propagation of any amount of cylindrical electromagnetic waves in a nonlinear medium. The results obtained by using the present method are accurately concordant with the results of using traditional coupled-wave equations. As an example of application, we discuss how a third wave affects the sum- and difference-frequency generation of two waves propagation in the nonlinear medium. PMID:26073066
Electromagnetic pulses at the boundary of a nonlinear plasma
International Nuclear Information System (INIS)
Satorius, E.H.
1975-01-01
An investigation was made of the behavior of strong electromagnetic pulses at the boundary of a nonlinear, cold, collisionless, and uniform plasma. The nonlinearity considered here is due to the nonlinear terms in the fluid equation which is used to describe the plasma. Two cases are studied. First, the case where there is a voltage pulse applied across the plane boundary of a semi-infinite, nonlinear plasma. Two different voltage pulses are considered, i.e., a delta function pulse and a suddenly turned-on sinusoidal pulse. The resulting electromagnetic fields propagating in the nonlinear plasma are found in this case. In the second case, the reflection of incident E-polarized and H-polarized, electromagnetic pulses at various angles of incidence from a nonlinear, semi-infinite plasma are considered. Again, two forms of incident pulses are considered: a delta function pulse and a suddenly turned-on sinusoidal pulse. In case two, the reflected electromagnetic fields are found. In both cases, the method used for finding the fields is to first solve the fluid equation (which describes the plasma) for the nonlinear conduction current in terms of the electric field using a perturbation method (since the nonlinear effects are assumed to be small). Next, this current is substituted into Maxwell's equations, and finally the electromagnetic fields which satisfy the boundary conditions are found. (U.S.)
SPARSE ELECTROMAGNETIC IMAGING USING NONLINEAR LANDWEBER ITERATIONS
Desmal, Abdulla; Bagci, Hakan
2015-01-01
minimization problem is solved using nonlinear Landweber iterations, where at each iteration a thresholding function is applied to enforce the sparseness-promoting L0/L1-norm constraint. The thresholded nonlinear Landweber iterations are applied to several two
International Nuclear Information System (INIS)
Lin, Z; Rewoldt, G; Ethier, S; Hahm, T S; Lee, W W; Lewandowski, J L V; Nishimura, Y; Wang, W X
2005-01-01
Recent progress in gyrokinetic particle-in-cell simulations of turbulent plasmas using the gyrokinetic toroidal code (GTC) is surveyed. In particular, recent results for electron temperature gradient (ETG) modes and their resulting transport are presented. Also, turbulence spreading, and the effects of the parallel nonlinearity, are described. The GTC code has also been generalized for non-circular plasma cross-section, and initial results are presented. In addition, two distinct methods of generalizing the GTC code to be electromagnetic are described, along with preliminary results. Finally, a related code, GTC-Neo, for calculating neoclassical fluxes, electric fields, and velocities, are described
Detection of electromagnetic radiation using nonlinear materials
Hwang, Harold Y.; Liu, Mengkun; Averitt, Richard D.; Nelson, Keith A.; Sternbach, Aaron; Fan, Kebin
2016-06-14
An apparatus for detecting electromagnetic radiation within a target frequency range is provided. The apparatus includes a substrate and one or more resonator structures disposed on the substrate. The substrate can be a dielectric or semiconductor material. Each of the one or more resonator structures has at least one dimension that is less than the wavelength of target electromagnetic radiation within the target frequency range, and each of the resonator structures includes at least two conductive structures separated by a spacing. Charge carriers are induced in the substrate near the spacing when the resonator structures are exposed to the target electromagnetic radiation. A measure of the change in conductivity of the substrate due to the induced charge carriers provides an indication of the presence of the target electromagnetic radiation.
Sparse electromagnetic imaging using nonlinear iterative shrinkage thresholding
Desmal, Abdulla; Bagci, Hakan
2015-01-01
A sparse nonlinear electromagnetic imaging scheme is proposed for reconstructing dielectric contrast of investigation domains from measured fields. The proposed approach constructs the optimization problem by introducing the sparsity constraint to the data misfit between the scattered fields expressed as a nonlinear function of the contrast and the measured fields and solves it using the nonlinear iterative shrinkage thresholding algorithm. The thresholding is applied to the result of every nonlinear Landweber iteration to enforce the sparsity constraint. Numerical results demonstrate the accuracy and efficiency of the proposed method in reconstructing sparse dielectric profiles.
Sparse electromagnetic imaging using nonlinear iterative shrinkage thresholding
Desmal, Abdulla
2015-04-13
A sparse nonlinear electromagnetic imaging scheme is proposed for reconstructing dielectric contrast of investigation domains from measured fields. The proposed approach constructs the optimization problem by introducing the sparsity constraint to the data misfit between the scattered fields expressed as a nonlinear function of the contrast and the measured fields and solves it using the nonlinear iterative shrinkage thresholding algorithm. The thresholding is applied to the result of every nonlinear Landweber iteration to enforce the sparsity constraint. Numerical results demonstrate the accuracy and efficiency of the proposed method in reconstructing sparse dielectric profiles.
Nonlinear dynamics of electromagnetic pulses in cold relativistic plasmas
Energy Technology Data Exchange (ETDEWEB)
Bonatto, A.; Pakter, R.; Rizzato, F.B. [Universidade Federal do Rio Grande do Sul, Instituto de Fisica, Rio Grande do Sul (Brazil)
2004-07-01
The propagation of intense electromagnetic pulses in plasmas is a subject of current interest particularly for particle acceleration and laser fusion.In the present analysis we study the self consistent propagation of nonlinear electromagnetic pulses in a one dimensional relativistic electron-ion plasma, from the perspective of nonlinear dynamics. We show how a series of Hamiltonian bifurcations give rise to the electric fields which are of relevance in the subject of particle acceleration. Connections between these bifurcated solutions and results of earlier analysis are made. (authors)
Non-linear electromagnetic interactions in thermal QED
International Nuclear Information System (INIS)
Brandt, F.T.; Frenkel, J.
1994-08-01
The behavior of the non-linear interactions between electromagnetic fields at high temperature is examined. It is shown that, in general, the log(T) dependence on the temperature of the Green functions is simply related to their UV behavior at zero-temperature. It is argued that the effective action describing the nonlinear thermal electromagnetic interactions has a finite limit as T -> ∞. This thermal action approaches, in the long wavelength limit, the negative of the corresponding zero-temperature action. (author). 12 refs, 1 fig
Nonlinear dynamics of electromagnetic pulses in cold relativistic plasmas
International Nuclear Information System (INIS)
Bonatto, A.; Pakter, R.; Rizzato, F.B.
2004-01-01
The propagation of intense electromagnetic pulses in plasmas is a subject of current interest particularly for particle acceleration and laser fusion.In the present analysis we study the self consistent propagation of nonlinear electromagnetic pulses in a one dimensional relativistic electron-ion plasma, from the perspective of nonlinear dynamics. We show how a series of Hamiltonian bifurcations give rise to the electric fields which are of relevance in the subject of particle acceleration. Connections between these bifurcated solutions and results of earlier analysis are made. (authors)
Nonlinear simulation of electromagnetic current diffusive interchange mode turbulence
International Nuclear Information System (INIS)
Yagi, M.; Itoh, S.I.; Fukuyama, A.
1998-01-01
The anomalous transport in toroidal plasmas has been investigated extensively. It is pointed out that the nonlinear instability is important in driving the microturbulence[1], i.e., the self-sustained plasma turbulence. This concept is explained as follows; when the electron motion along the magnetic field line is resisted by the background turbulence, it gives rise to the effective resistivity and enhances the level of the turbulence. The nonlinear simulation of the electrostatic current diffusive interchange mode (CDIM) in the two dimensional sheared slab geometry has been performed as an example. The occurrence of the nonlinear instability and the self-sustainment of the plasma turbulence were confirmed by this simulation[2]. On the other hand, the electromagnetic turbulence is sustained in the high pressure limit. The possibility of the self-organization with more variety has been pointed out[3]. It is important to study the electromagnetic turbulence based on the nonlinear simulation. In this paper, the model equation for the electrostatic CDIM turbulence[2] is extended for both electrostatic and electromagnetic turbulence. (1) Not only E x B convective nonlinearity but also the electromagnetic nonlinearity which is related to the parallel flow are incorporated into the model equation. (2) The electron and ion pressure evolution equations are solved separately, making it possible to distinguish the electron and ion thermal diffusivities. The two dimensional nonlinear simulation of the electromagnetic CDIM is performed based on the extended fluid model. This paper is organized as follows. The model equation is explained in section II. The result of simulation is shown in section III. The conclusion and discussion are given in section IV. (author)
Theoretical models for ultrashort electromagnetic pulse propagation in nonlinear metamaterials
International Nuclear Information System (INIS)
Wen, Shuangchun; Xiang, Yuanjiang; Dai, Xiaoyu; Tang, Zhixiang; Su, Wenhua; Fan, Dianyuan
2007-01-01
A metamaterial (MM) differs from an ordinary optical material mainly in that it has a dispersive magnetic permeability and offers greatly enhanced design freedom to alter the linear and nonlinear properties. This makes it possible for us to control the propagation of ultrashort electromagnetic pulses at will. Here we report on generic features of ultrashort electromagnetic pulse propagation and demonstrate the controllability of both the linear and nonlinear parameters of models for pulse propagation in MMs. First, we derive a generalized system of coupled three-dimensional nonlinear Schroedinger equations (NLSEs) suitable for few-cycle pulse propagation in a MM with both nonlinear electric polarization and nonlinear magnetization. The coupled equations recover previous models for pulse propagation in both ordinary material and a MM under the same conditions. Second, by using the coupled NLSEs in the Drude dispersive model as an example, we identify the respective roles of the dispersive electric permittivity and magnetic permeability in ultrashort pulse propagation and disclose some additional features of pulse propagation in MMs. It is shown that, for linear propagation, the sign and magnitude of space-time focusing can be controlled through adjusting the linear dispersive permittivity and permeability. For nonlinear propagation, the linear dispersive permittivity and permeability are incorporated into the nonlinear magnetization and nonlinear polarization, respectively, resulting in controllable magnetic and electric self-steepening effects and higher-order dispersively nonlinear terms in the propagation models
International Nuclear Information System (INIS)
Parra, Felix I; Catto, Peter J
2009-01-01
We compare two different derivations of the gyrokinetic equation: the Hamiltonian approach in Dubin D H E et al (1983 Phys. Fluids 26 3524) and the recursive methodology in Parra F I and Catto P J (2008 Plasma Phys. Control. Fusion 50 065014). We prove that both approaches yield the same result at least to second order in a Larmor radius over macroscopic length expansion. There are subtle differences in the definitions of some of the functions that need to be taken into account to prove the equivalence.
Global gyrokinetic and fluid hybrid simulations of tokamaks and stellarators
Energy Technology Data Exchange (ETDEWEB)
Cole, Michael David John
2016-07-15
Achieving commercial production of electricity by magnetic confinement fusion requires improvements in energy and particle confinement. In order to better understand and optimise confinement, numerical simulations of plasma phenomena are useful. One particularly challenging regime is that in which long wavelength MHD phenomena interact with kinetic phenomena. In such a regime, global electromagnetic gyrokinetic simulations are necessary. In this regime, computational requirements have been excessive for Eulerian methods, while Particle-in-Cell (PIC) methods have been particularly badly affected by the 'cancellation problem', a numerical problem resulting from the structure of the electromagnetic gyrokinetic equations. A number of researchers have been working on mitigating this problem with some significant successes. Another alternative to mitigating the problem is to move to a hybrid system of fluid and gyrokinetic equations. At the expense of reducing the physical content of the numerical model, particularly electron kinetic physics, it is possible in this way to perform global electromagnetic PIC simulations retaining ion gyrokinetic effects but eliminating the cancellation problem. The focus of this work has been the implementation of two such hybrid models into the gyrokinetic code EUTERPE. The two models treat electrons and the entire bulk plasma respectively as a fluid. Both models are additionally capable of considering the self-consistent interaction of an energetic ion species, described gyrokinetically, with the perturbed fields. These two models have been successfully benchmarked in linear growth rate and frequency against other codes for a Toroidal Alfven Eigenmode (TAE) case in both the linear and non-linear regimes. The m=1 internal kink mode, which is particularly challenging in terms of the fully gyrokinetic cancellation problem, has also been successfully benchmarked using the hybrid models with the MHD eigenvalue code CKA. Non-linear
Global gyrokinetic and fluid hybrid simulations of tokamaks and stellarators
International Nuclear Information System (INIS)
Cole, Michael David John
2016-01-01
Achieving commercial production of electricity by magnetic confinement fusion requires improvements in energy and particle confinement. In order to better understand and optimise confinement, numerical simulations of plasma phenomena are useful. One particularly challenging regime is that in which long wavelength MHD phenomena interact with kinetic phenomena. In such a regime, global electromagnetic gyrokinetic simulations are necessary. In this regime, computational requirements have been excessive for Eulerian methods, while Particle-in-Cell (PIC) methods have been particularly badly affected by the 'cancellation problem', a numerical problem resulting from the structure of the electromagnetic gyrokinetic equations. A number of researchers have been working on mitigating this problem with some significant successes. Another alternative to mitigating the problem is to move to a hybrid system of fluid and gyrokinetic equations. At the expense of reducing the physical content of the numerical model, particularly electron kinetic physics, it is possible in this way to perform global electromagnetic PIC simulations retaining ion gyrokinetic effects but eliminating the cancellation problem. The focus of this work has been the implementation of two such hybrid models into the gyrokinetic code EUTERPE. The two models treat electrons and the entire bulk plasma respectively as a fluid. Both models are additionally capable of considering the self-consistent interaction of an energetic ion species, described gyrokinetically, with the perturbed fields. These two models have been successfully benchmarked in linear growth rate and frequency against other codes for a Toroidal Alfven Eigenmode (TAE) case in both the linear and non-linear regimes. The m=1 internal kink mode, which is particularly challenging in terms of the fully gyrokinetic cancellation problem, has also been successfully benchmarked using the hybrid models with the MHD eigenvalue code CKA. Non-linear simulations
Testing Gyrokinetics on C-Mod and NSTX
International Nuclear Information System (INIS)
Redi, M.H.; Dorland, W.; Fiore, C.L.; Stutman, D.; Baumgaertel, J.A.; Davis, B.; Kaye, S.M.; McCune, D.C.; Menard, J.; Rewoldt, G.
2005-01-01
Quantitative benchmarks of computational physics codes against experiment are essential for the credible application of such codes. Fluctuation measurements can provide necessary critical tests of nonlinear gyrokinetic simulations, but such require extraordinary computational resources. Linear micro-stability calculations with the GS2 [1] gyrokinetic code have been carried out for tokamak and ST experiments which exhibit internal transport barriers (ITB) and good plasma confinement. Qualitative correlation is found for improved confinement before and during ITB plasmas on Alcator C-Mod [2] and NSTX [3], with weaker long wavelength micro-instabilities in the plasma core regions. Mixing length transport models are discussed. The NSTX L-mode is found to be near marginal stability for kinetic ballooning modes. Fully electromagnetic, linear, gyrokinetic calculations of the Alcator C-Mod ITB during off-axis rf heating, following four plasma species and including the complete electron response show ITG/TEM microturbulence is suppressed in the plasma core and in the barrier region before barrier formation, without recourse to the usual requirements of velocity shear or reversed magnetic shear [4-5]. No strongly growing long or short wavelength drift modes are found in the plasma core but strong ITG/TEM and ETG drift wave turbulence is found outside the barrier region. Linear microstability analysis is qualitatively consistent with the experimental transport analysis, showing low transport inside and high transport outside the ITB region before barrier formation, without consideration of ExB shear stabilization
Electromagnetic Transport From Microtearing Mode Turbulence
International Nuclear Information System (INIS)
Guttenfelder, W.; Candy, J.; Kaye, S.M.; Nevins, W.M.; Wang, E.; Bell, R.E.; Hammett, G.W.; LeBlanc, B.P.; Mikkelsen, D.R.; Yuh, H.
2011-01-01
This Letter presents non-linear gyrokinetic simulations of microtearing mode turbulence. The simulations include collisional and electromagnetic effects and use experimental parameters from a high beta discharge in the National Spherical Torus Experiment (NSTX). The predicted electron thermal transport is comparable to that given by experimental analysis, and it is dominated by the electromagnetic contribution of electrons free streaming along the resulting stochastic magnetic field line trajectories. Experimental values of flow shear can significantly reduce the predicted transport.
Hager, Robert; Yoon, E. S.; Ku, S.; D'Azevedo, E. F.; Worley, P. H.; Chang, C. S.
2015-11-01
We describe the implementation, and application of a time-dependent, fully nonlinear multi-species Fokker-Planck-Landau collision operator based on the single-species work of Yoon and Chang [Phys. Plasmas 21, 032503 (2014)] in the full-function gyrokinetic particle-in-cell codes XGC1 [Ku et al., Nucl. Fusion 49, 115021 (2009)] and XGCa. XGC simulations include the pedestal and scrape-off layer, where significant deviations of the particle distribution function from a Maxwellian can occur. Thus, in order to describe collisional effects on neoclassical and turbulence physics accurately, the use of a non-linear collision operator is a necessity. Our collision operator is based on a finite volume method using the velocity-space distribution functions sampled from the marker particles. Since the same fine configuration space mesh is used for collisions and the Poisson solver, the workload due to collisions can be comparable to or larger than the workload due to particle motion. We demonstrate that computing time spent on collisions can be kept affordable by applying advanced parallelization strategies while conserving mass, momentum, and energy to reasonable accuracy. We also show results of production scale XGCa simulations in the H-mode pedestal and compare to conventional theory. Work supported by US DOE OFES and OASCR.
Iterative Nonlinear Tikhonov Algorithm with Constraints for Electromagnetic Tomography
Xu, Feng; Deshpande, Manohar
2012-01-01
Low frequency electromagnetic tomography such as the capacitance tomography (ECT) has been proposed for monitoring and mass-gauging of gas-liquid two-phase system under microgravity condition in NASA's future long-term space missions. Due to the ill-posed inverse problem of ECT, images reconstructed using conventional linear algorithms often suffer from limitations such as low resolution and blurred edges. Hence, new efficient high resolution nonlinear imaging algorithms are needed for accurate two-phase imaging. The proposed Iterative Nonlinear Tikhonov Regularized Algorithm with Constraints (INTAC) is based on an efficient finite element method (FEM) forward model of quasi-static electromagnetic problem. It iteratively minimizes the discrepancy between FEM simulated and actual measured capacitances by adjusting the reconstructed image using the Tikhonov regularized method. More importantly, it enforces the known permittivity of two phases to the unknown pixels which exceed the reasonable range of permittivity in each iteration. This strategy does not only stabilize the converging process, but also produces sharper images. Simulations show that resolution improvement of over 2 times can be achieved by INTAC with respect to conventional approaches. Strategies to further improve spatial imaging resolution are suggested, as well as techniques to accelerate nonlinear forward model and thus increase the temporal resolution.
Sparse Nonlinear Electromagnetic Imaging Accelerated With Projected Steepest Descent Algorithm
Desmal, Abdulla
2017-04-03
An efficient electromagnetic inversion scheme for imaging sparse 3-D domains is proposed. The scheme achieves its efficiency and accuracy by integrating two concepts. First, the nonlinear optimization problem is constrained using L₀ or L₁-norm of the solution as the penalty term to alleviate the ill-posedness of the inverse problem. The resulting Tikhonov minimization problem is solved using nonlinear Landweber iterations (NLW). Second, the efficiency of the NLW is significantly increased using a steepest descent algorithm. The algorithm uses a projection operator to enforce the sparsity constraint by thresholding the solution at every iteration. Thresholding level and iteration step are selected carefully to increase the efficiency without sacrificing the convergence of the algorithm. Numerical results demonstrate the efficiency and accuracy of the proposed imaging scheme in reconstructing sparse 3-D dielectric profiles.
Nonlinear metamaterials for electromagnetic energy harvesting (Conference Presentation)
Oumbe Tekam, Gabin Thibaut; Ginis, Vincent; Seetharamdoo, Divitha; Danckaert, Jan
2016-09-01
Surrounded by electromagnetic radiation coming from wireless power transfer to consumer devices such as mobile phones, computers and television, our society is facing the scientific and technological challenge to recover energy that is otherwise lost to the environment. Energy harvesting is an emerging field of research focused on this largely unsolved problem, especially in the microwave regime. Metamaterials provide a very promising platform to meet this purpose. These artificial materials are made from subwavelength building blocks, and can be designed by resonate at particular frequencies, depending on their shape, geometry, size, and orientation. In this work, we show that an efficient electromagnetic energy harvester can be design by inserting a nonlinear element directly within the metamaterial unit cell, leading to the conversion of RF input power to DC charge accumulation. The electromagnetic energy harvester operating at microwave frequencies is built from a cut-wire metasurface, which operates as a quasistatic electric dipole resonator. Using the equivalent electrical circuit, we design the parameters to tune the resonance frequency of the harvester at the desired frequency, and we compare these results with numerical simulations. Finally, we discuss the efficiency of our metamaterial energy harvesters. This work potentially offers a variety of applications, for example in the telecommunications industry to charge phones, in robotics to power microrobots, and also in medicine to advance pacemakers or health monitoring sensors.
Nonlinear electromagnetic waves in a degenerate electron-positron plasma
Energy Technology Data Exchange (ETDEWEB)
El-Labany, S.K., E-mail: skellabany@hotmail.com [Department of Physics, Faculty of Science, Damietta University, New Damietta (Egypt); El-Taibany, W.F., E-mail: eltaibany@hotmail.com [Department of Physics, College of Science for Girls in Abha, King Khalid University, Abha (Saudi Arabia); El-Samahy, A.E.; Hafez, A.M.; Atteya, A., E-mail: ahmedsamahy@yahoo.com, E-mail: am.hafez@sci.alex.edu.eg, E-mail: ahmed_ateya2002@yahoo.com [Department of Physics, Faculty of Science, Alexandria University, Alexandria (Egypt)
2015-08-15
Using the reductive perturbation technique (RPT), the nonlinear propagation of magnetosonic solitary waves in an ultracold, degenerate (extremely dense) electron-positron (EP) plasma (containing ultracold, degenerate electron, and positron fluids) is investigated. The set of basic equations is reduced to a Korteweg-de Vries (KdV) equation for the lowest-order perturbed magnetic field and to a KdV type equation for the higher-order perturbed magnetic field. The solutions of these evolution equations are obtained. For better accuracy and searching on new features, the new solutions are analyzed numerically based on compact objects (white dwarf) parameters. It is found that including the higher-order corrections results as a reduction (increment) of the fast (slow) electromagnetic wave amplitude but the wave width is increased in both cases. The ranges where the RPT can describe adequately the total magnetic field including different conditions are discussed. (author)
A sparse electromagnetic imaging scheme using nonlinear landweber iterations
Desmal, Abdulla
2015-10-26
Development and use of electromagnetic inverse scattering techniques for imagining sparse domains have been on the rise following the recent advancements in solving sparse optimization problems. Existing techniques rely on iteratively converting the nonlinear forward scattering operator into a sequence of linear ill-posed operations (for example using the Born iterative method) and applying sparsity constraints to the linear minimization problem of each iteration through the use of L0/L1-norm penalty term (A. Desmal and H. Bagci, IEEE Trans. Antennas Propag, 7, 3878–3884, 2014, and IEEE Trans. Geosci. Remote Sens., 3, 532–536, 2015). It has been shown that these techniques produce more accurate and sharper images than their counterparts which solve a minimization problem constrained with smoothness promoting L2-norm penalty term. But these existing techniques are only applicable to investigation domains involving weak scatterers because the linearization process breaks down for high values of dielectric permittivity.
Burby, Joshua; Brizard, Alain
2017-10-01
Test-particle gyrocenter equations of motion play an essential role in the diagnosis of turbulent strongly-magnetized plasmas, and are playing an increasingly-important role in the formulation of kinetic-gyrokinetic hybrid models. Previous gyrocenter models required the knowledge of the perturbed electromagnetic potentials, which are not directly observable quantities (since they are gauge-dependent). A new gauge-free formulation of gyrocenter motion is presented, which enables gyrocenter trajectories to be determined using only measured values of the directly-observable electromagnetic field. Our gauge-free gyrokinetic theory is general enough to allow for gyroradius-scale fluctuations in both the electric and magnetic field. In addition, we provide gauge-free expressions for the charge and current densities produced by a distribution of gyrocenters, which explicitly include guiding-center and gyrocenter polarization and magnetization effects. This research was supported by the U.S. DOE Contract Nos. DE-SC0014032 (AB) and DE-AC05-06OR23100 (JB).
Homogeneous and isotropic cosmologies with nonlinear electromagnetic radiation
International Nuclear Information System (INIS)
Vollick, Dan N.
2008-01-01
In this paper I examine cosmological models that contain a stochastic background of nonlinear electromagnetic radiation. I show that for Born-Infeld electrodynamics the equation of state parameter, w=P/ρ, remains close to 1/3 throughout the evolution of the universe if E 2 =B 2 in the late universe to a high degree of accuracy. Theories with electromagnetic Lagrangians of the form L=-(1/4)F 2 +αF 4 have recently been studied in magnetic universes, where the electric field vanishes. It was shown that the F 4 term can produce a bounce in the early universe, avoiding an initial singularity. Here I show that the inclusion of an electric field, with E 2 ≅B 2 in the late universe, eliminates the bounce and the universe begins with an initial singularity. I also examine theories with Lagrangians of the form L=-(1/4)F 2 -μ 8 /F 2 , which have been shown to produce a period of late time accelerated expansion in magnetic universes. I show that, if an electric field is introduced, the accelerated phase will only occur if E 2 2 .
A preconditioned inexact newton method for nonlinear sparse electromagnetic imaging
Desmal, Abdulla
2015-03-01
A nonlinear inversion scheme for the electromagnetic microwave imaging of domains with sparse content is proposed. Scattering equations are constructed using a contrast-source (CS) formulation. The proposed method uses an inexact Newton (IN) scheme to tackle the nonlinearity of these equations. At every IN iteration, a system of equations, which involves the Frechet derivative (FD) matrix of the CS operator, is solved for the IN step. A sparsity constraint is enforced on the solution via thresholded Landweber iterations, and the convergence is significantly increased using a preconditioner that levels the FD matrix\\'s singular values associated with contrast and equivalent currents. To increase the accuracy, the weight of the regularization\\'s penalty term is reduced during the IN iterations consistently with the scheme\\'s quadratic convergence. At the end of each IN iteration, an additional thresholding, which removes small \\'ripples\\' that are produced by the IN step, is applied to maintain the solution\\'s sparsity. Numerical results demonstrate the applicability of the proposed method in recovering sparse and discontinuous dielectric profiles with high contrast values.
Relativistic harmonic content of nonlinear electromagnetic waves in underdense plasmas
International Nuclear Information System (INIS)
Mori, W.B.; Decker, C.D.; Leemans, W.P.
1993-01-01
The relativistic harmonic content of large amplitude electromagnetic waves propagating in underdense plasmas is investigated. The steady state harmonic content of nonlinear linearly polarized waves is calculated for both the very underdense (w p /w o ) much-lt 1 and critical density (w p /w o ) ≅ 1 limits. For weak nonlinearities, eE o /mcw o p /w o . Arguments are given for extending these results for arbitrary wave amplitudes. The authors also show that the use of the variable x-ct and the quasi-static approximation leads to errors in both magnitude and sign when calculating the third harmonic. In the absence of damping or density gradients the third harmonic's amplitude is found to oscillate between zero and twice the steady state value. Preliminary PIC simulation results are presented. The simulation results are in basic agreement with the uniform plasma predictions for the third harmonic amplitude. However, the higher harmonics are orders of magnitude larger than expected and the presence of density ramps significantly modifies the results
Nonlinear propagation of intense electromagnetic waves in weakly-ionized plasmas
International Nuclear Information System (INIS)
Shukla, P.K.
1993-01-01
The nonlinear propagation of intense electromagnetic waves in weakly-ionized plasmas is considered. Stimulated scattering mechanisms involving electromagnetic and acoustic waves in an unmagnetized plasma are investigated. The growth rate and threshold for three-wave decay interactions as well as modulational and filamentation instabilities are presented. Furthermore, the electromagnetic wave modulation theory is generalized for weakly ionized collisional magnetoplasmas. Here, the radiation envelope is generally governed by a nonlinear Schroedinger equation. Accounting for the dependence of the attachment frequency on the radiation intensity, ponderomotive force, as well as the differential Joule heating nonlinearity, the authors derive the equations for the nonthermal electron density and temperature perturbations. The various nonlinear terms in the electron motion are compared. The problems of self-focusing and wave localization are discussed. The relevance of the investigation to ionospheric modification by powerful electromagnetic waves is pointed out
International Nuclear Information System (INIS)
Abe, H.; Okuda, H.
1994-06-01
We study linear and nonlinear properties of a new computer simulation model developed to study the propagation of electromagnetic waves in a dielectric medium in the linear and nonlinear regimes. The model is constructed by combining a microscopic model used in the semi-classical approximation for the dielectric media and the particle model developed for the plasma simulations. It is shown that the model may be useful for studying linear and nonlinear wave propagation in the dielectric media
Directory of Open Access Journals (Sweden)
Ren He
2015-01-01
Full Text Available Since theoretical guidance is lacking in the design and control of the integrated system of electromagnetic brake and frictional brake, this paper aims to solve this problem and explores the nonlinear coupling characteristics and dynamic characteristics of the integrated system of electromagnetic brake and frictional brake. This paper uses the power bond graph method to establish nonlinear coupling mathematical model of the integrated system of electromagnetic brake and frictional brake and conducts the contrastive analysis on the dynamic characteristics based on this mathematical model. Meanwhile, the accuracy of the nonlinear coupling mathematical model proposed above is verified on the hardware in the loop simulation platform, and nonlinear coupling characteristics of the integrated system are also analyzed through experiments.
Gyrokinetic Simulations of Solar Wind Turbulence from Ion to Electron Scales
International Nuclear Information System (INIS)
Howes, G. G.; TenBarge, J. M.; Dorland, W.; Numata, R.; Quataert, E.; Schekochihin, A. A.; Tatsuno, T.
2011-01-01
A three-dimensional, nonlinear gyrokinetic simulation of plasma turbulence resolving scales from the ion to electron gyroradius with a realistic mass ratio is presented, where all damping is provided by resolved physical mechanisms. The resulting energy spectra are quantitatively consistent with a magnetic power spectrum scaling of k -2.8 as observed in in situ spacecraft measurements of the 'dissipation range' of solar wind turbulence. Despite the strongly nonlinear nature of the turbulence, the linear kinetic Alfven wave mode quantitatively describes the polarization of the turbulent fluctuations. The collisional ion heating is measured at subion-Larmor radius scales, which provides evidence of the ion entropy cascade in an electromagnetic turbulence simulation.
Knotted solutions for linear and nonlinear theories: Electromagnetism and fluid dynamics
Directory of Open Access Journals (Sweden)
Daniel W.F. Alves
2017-10-01
Full Text Available We examine knotted solutions, the most simple of which is the “Hopfion”, from the point of view of relations between electromagnetism and ideal fluid dynamics. A map between fluid dynamics and electromagnetism works for initial conditions or for linear perturbations, allowing us to find new knotted fluid solutions. Knotted solutions are also found to be solutions of nonlinear generalizations of electromagnetism, and of quantum-corrected actions for electromagnetism coupled to other modes. For null configurations, electromagnetism can be described as a null pressureless fluid, for which we can find solutions from the knotted solutions of electromagnetism. We also map them to solutions of Euler's equations, obtained from a type of nonrelativistic reduction of the relativistic fluid equations.
A sparse electromagnetic imaging scheme using nonlinear landweber iterations
Desmal, Abdulla; Bagci, Hakan
2015-01-01
Development and use of electromagnetic inverse scattering techniques for imagining sparse domains have been on the rise following the recent advancements in solving sparse optimization problems. Existing techniques rely on iteratively converting
Nonlinear interaction of powerful short electromagnetic pulses with an electron plasma
International Nuclear Information System (INIS)
Rao, N.N.; Yu, M.Y.; Shukla, P.K.
1990-01-01
The nonlinear interaction of powerful short electromagnetic pulses with a plasma consisting of two groups of electrons and immobile ions has been studied. It is shown that the interaction is governed by a nonlinear equation for the electromagnetic wave envelope and a driven nonlinear equation for the low-frequency electron fluctuations. The driver for the latter depends explicitly on the spatio-temporal evolution of the electromagnetic wave flux. It is found that, depending on the cold-to-hot electron density ratio, the localized pulse can propagate with sub- as well as supersonic velocities accompanied by compressional or rarefactional density perturbations. The conditions of existence for the different types of solitary pulses are obtained. The present investigation may be relevant to the study of wave-plasma interaction devices such as inertial fusion confinement as well as to ionospheric modification experiments. (author)
International Nuclear Information System (INIS)
Sugaya, R.; Ue, A.; Maehara, T.; Sugawa, M.
1996-01-01
Acceleration and heating of a relativistic electron beam by cascading nonlinear Landau damping involving three or four intense electromagnetic waves in a plasma are studied theoretically based on kinetic wave equations and transport equations derived from relativistic Vlasov endash Maxwell equations. Three or four electromagnetic waves excite successively two or three nonresonant beat-wave-driven relativistic electron plasma waves with a phase velocity near the speed of light [v p =c(1-γ -2 p ) 1/2 , γ p =ω/ω pe ]. Three beat waves interact nonlinearly with the electron beam and accelerate it to a highly relativistic energy γ p m e c 2 more effectively than by the usual nonlinear Landau damping of two electromagnetic waves. It is proved that the electron beam can be accelerated to more highly relativistic energy in the plasma whose electron density decreases temporally with an appropriate rate because of the temporal increase of γ p . copyright 1996 American Institute of Physics
Transients of the electromagnetically-induced-transparency-enhanced refractive Kerr nonlinearity
International Nuclear Information System (INIS)
Pack, M. V.; Camacho, R. M.; Howell, J. C.
2007-01-01
We report observations of the dynamics of electromagnetically induced transparency (EIT) in a Λ system when the ground states are Stark shifted. Interactions of this type exhibit large optical nonlinearities called Kerr nonlinearities, and have numerous applications. The EIT Kerr nonlinearity is relatively slow, which is a limiting factor that may make many potential applications impossible. Using rubidium atoms, we observe the dynamics of the EIT Kerr nonlinearity using a Mach-Zehnder interferometer to measure phase modulation of the EIT fields resulting from a pulsed signal beam Stark shifting the ground state energy levels. The rise times and transients agree well with theory
International Nuclear Information System (INIS)
Denisov, V.I.; Krivchenkov, I.V.; Denisov, I.P.
2002-01-01
The study on the electromagnetic waves propagation in the neutron star magnetic dipole and gravitation fields, taking place according to the vacuum nonlinear electrodynamics laws, is carried out. It is shown that depending on the polarization the electromagnetic signals in this field propagate by different beams and with various velocities. The law on these signals motion by beams is established. The calculation of differences in the times of the electromagnetic signals propagation, having the same source up to the detector, is presented. It is shown that this difference in some cases may reach enough measurable value of 1 μs [ru
Nonlinear properties of gated graphene in a strong electromagnetic field
Energy Technology Data Exchange (ETDEWEB)
Avetisyan, A. A., E-mail: artakav@ysu.am; Djotyan, A. P., E-mail: adjotyan@ysu.am [Yerevan State University, Department of Physics (Armenia); Moulopoulos, K., E-mail: cos@ucy.ac.cy [University of Cyprus, Department of Physics (Cyprus)
2017-03-15
We develop a microscopic theory of a strong electromagnetic field interaction with gated bilayer graphene. Quantum kinetic equations for density matrix are obtained using a tight binding approach within second quantized Hamiltonian in an intense laser field. We show that adiabatically changing the gate potentials with time may produce (at resonant photon energy) a full inversion of the electron population with high density between valence and conduction bands. In the linear regime, excitonic absorption of an electromagnetic radiation in a graphene monolayer with opened energy gap is also studied.
Ulku, Huseyin Arda
2015-02-01
An explicit marching on-in-time (MOT) based time domain electric field volume integral equation (TDVIE) solver for characterizing electromagnetic wave interactions on scatterers with nonlinear material properties is proposed. Discretization of the unknown electric field intensity and flux density is carried out by half and full Schaubert-Wilton-Glisson basis functions, respectively. Coupled system of spatially discretized TDVIE and the nonlinear constitutive relation between the field intensity and the flux density is integrated in time to compute the samples of the unknowns. An explicit PE(CE)m scheme is used for this purpose. Explicitness allows for \\'easy\\' incorporation of the nonlinearity as a function only to be evaluated on the right hand side of the coupled system of equations. A numerical example that demonstrates the applicability of the proposed MOT scheme to analyzing electromagnetic interactions on Kerr-nonlinear scatterers is presented. © 2015 IEEE.
Application of the descriptive function on non-linear electromagnetic phenomena
International Nuclear Information System (INIS)
Silva, H.T.
1982-01-01
This paper presents the solution of the nonlinear plan wave equation in non-equilibrium dielectric medium. The descriptive function appears as a useful tool to describe the medium response when it is possible to consider intensive electromagnetic response. Despite it has been considered an ideal situation of a limitless nonlinear medium, the results constitute a solid basis to mold more complex processes, such as those which take place in the plasma physics
International Nuclear Information System (INIS)
Han, Jeong Sam
2010-01-01
In this paper, the design and nonlinear simulation of a multistable electromagnetic microactuator, which provides four stable equilibrium positions within its operating range, have been discussed. Quadstable actuator motion has been made possible by using both X- and Y-directional bistable structures with snapping curved beams. Two pairs of the curved beams are attached to an inner frame in both X- and Y-directions to realize independent bistable behavior in each direction. For the actuation of the actuator at the micrometer scale, an electromagnetic actuation method in which Lorentz force is taken into consideration was used. By using this method, micrometer-stroke quadstability in a plane parallel to a substrate was possible. The feasibility of designing an actuator that can realize quadstable motion by using the electromagnetic actuation method has been thoroughly clarified by performing nonlinear static and dynamic analyses and electrothermal coupled-field analysis of the multistable microactuator
Nonlinear propagation of electromagnetic waves in negative-refraction-index composite materials.
Kourakis, I; Shukla, P K
2005-07-01
We investigate the nonlinear propagation of electromagnetic waves in left-handed materials. For this purpose, we consider a set of coupled nonlinear Schrödinger (CNLS) equations, which govern the dynamics of coupled electric and magnetic field envelopes. The CNLS equations are used to obtain a nonlinear dispersion, which depicts the modulational stability profile of the coupled plane-wave solutions in left-handed materials. An exact (in)stability criterion for modulational interactions is derived, and analytical expressions for the instability growth rate are obtained.
Kuang-Leman; Wu Yong Shi
2003-01-01
We study linear and nonlinear optical properties of an electromagnetically induced transparency (EIT) medium interacting with two quantized laser fields in the adiabatic EIT case. We show that the EIT medium exhibits normal dispersion. Kerr and higher-order nonlinear refractive index coefficients are also calculated in a completely analytical form. It is indicated that the EIT medium exhibits giant resonantly enhanced nonlinearities. We discuss the response of the EIT medium to nonclassical light fields and find that the polarization vanishes when the probe laser is initially in a nonclassical state of no single-photon coherence.
A preconditioned inexact newton method for nonlinear sparse electromagnetic imaging
Desmal, Abdulla; Bagci, Hakan
2015-01-01
to tackle the nonlinearity of these equations. At every IN iteration, a system of equations, which involves the Frechet derivative (FD) matrix of the CS operator, is solved for the IN step. A sparsity constraint is enforced on the solution via thresholded
Directory of Open Access Journals (Sweden)
Jun Yin
2015-01-01
Full Text Available Electromagnetic actuated active suspension benefits active control and energy harvesting from vibration at the same time. However, the rotary type electromagnetic actuated active suspension introduces a significant extra mass on the unsprung mass due to the inertia of the rotating components of the actuator. The magnitude of the introduced unsprung mass is studied based on a gearbox type actuator and a ball screw type actuator. The geometry of the suspension and the actuator also influence the equivalent unsprung mass significantly. The suspension performance simulation or control logic derived should take this equivalent unsprung mass into account. Besides, an extra force should be compensated due to the nonlinear features of the suspension structure and it is studied. The active force of the actuator should compensate this extra force. The discovery of this paper provides a fundamental for evaluating the rotary type electromagnetic actuated active suspension performance and control strategy derived as well as controlling the electromagnetic actuated active suspension more precisely.
Kim, Kihong; Phung, D K; Rotermund, F; Lim, H
2008-01-21
We develop a generalized version of the invariant imbedding method, which allows us to solve the electromagnetic wave equations in arbitrarily inhomogeneous stratified media where both the dielectric permittivity and magnetic permeability depend on the strengths of the electric and magnetic fields, in a numerically accurate and efficient manner. We apply our method to a uniform nonlinear slab and find that in the presence of strong external radiation, an initially uniform medium of positive refractive index can spontaneously change into a highly inhomogeneous medium where regions of positive or negative refractive index as well as metallic regions appear. We also study the wave transmission properties of periodic nonlinear media and the influence of nonlinearity on the mode conversion phenomena in inhomogeneous plasmas. We argue that our theory is very useful in the study of the optical properties of a variety of nonlinear media including nonlinear negative index media fabricated using wires and split-ring resonators.
Energy Technology Data Exchange (ETDEWEB)
Chowdhury, J.; Wan, Weigang; Chen, Yang; Parker, Scott E. [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States); Groebner, Richard J. [General Atomics, Post Office Box 85068, San Diego, California 92186 (United States); Holland, C. [University of California at San Diego, La Jolla, California 92093 (United States); Howard, N. T. [Oak Ridge Institute for Science and Education (ORISE), Oak Ridge, Tennessee 37831 (United States)
2014-11-15
The δ f particle-in-cell code GEM is used to study the transport “shortfall” problem of gyrokinetic simulations. In local simulations, the GEM results confirm the previously reported simulation results of DIII-D [Holland et al., Phys. Plasmas 16, 052301 (2009)] and Alcator C-Mod [Howard et al., Nucl. Fusion 53, 123011 (2013)] tokamaks with the continuum code GYRO. Namely, for DIII-D the simulations closely predict the ion heat flux at the core, while substantially underpredict transport towards the edge; while for Alcator C-Mod, the simulations show agreement with the experimental values of ion heat flux, at least within the range of experimental error. Global simulations are carried out for DIII-D L-mode plasmas to study the effect of edge turbulence on the outer core ion heat transport. The edge turbulence enhances the outer core ion heat transport through turbulence spreading. However, this edge turbulence spreading effect is not enough to explain the transport underprediction.
Gyrokinetic simulation of microtearing turbulence
International Nuclear Information System (INIS)
Doerk, Hauke
2013-01-01
In modern fusion experiments, plasma turbulence is responsible for the radial heat transport and thus determines the plasma confinement within the magnetic field of tokamak devices. Deeper theoretical understanding is needed to explain today's and future fusion experiments. The goal of fusion research is to establish nuclear fusion as a safe and sustainable energy source. In future fusion power plants, and also in large fusion experiments like the presently constructed ITER, plasma heating predominantly affects the electron species. The reason is of fundamental nature: the collisional cross section of fast ions that are produced by the heating systems is larger for thermal electrons than for thermal ions. It is thus essential to correctly predict electron thermal transport, but the overall picture still continues to evolve. Besides microinstabilities on the electron gyroradius scales, also a stochastized magnetic field can contribute to enhanced electron transport. Already since the 1970's, the so-called microtearing instability is discussed as a source of stochastic fields. This microinstability deserves its name for breaking up the magnetic field structure by forming small-scale magnetic islands. The linear microtearing instability and its nonlinear, turbulent behavior is investigated in this thesis by means of numerical simulations with the gyrokinetic turbulence code Gene. The underlying gyrokinetic equations are not only appropriate to predict turbulent transport, but also describe neoclassical transport that is drift-kinetic in nature. Besides revealing interesting physics on long time scales, solving the neoclassical equation serves as an excellent test for the numerical implementation of the collision operator in Gene. Focusing on the local limit, it is found that a modification of this implementation that considers certain symmetries is necessary to obtain a satisfactory agreement with the well-established drift-kinetic neoclassical code Neo. Also the
Gyrokinetic simulation of internal kink modes
International Nuclear Information System (INIS)
Naitou, Hiroshi; Tsuda, Kenji; Lee, W.W.; Sydora, R.D.
1995-05-01
Internal disruption in a tokamak has been simulated using a three-dimensional magneto-inductive gyrokinetic particle code. The code operates in both the standard gyrokinetic mode (total-f code) and the fully nonlinear characteristic mode (δf code). The latter, a recent addition, is a quiet low noise algorithm. The computational model represents a straight tokamak with periodic boundary conditions in the toroidal direction. The plasma is initially uniformly distributed in a square cross section with perfectly conducting walls. The linear mode structure of an unstable m = 1 (poloidal) and n = 1 (toroidal) kinetic internal kink mode is clearly observed, especially in the δf code. The width of the current layer around the x-point, where magnetic reconnection occurs, is found to be close to the collisionless electron skin depth. This is consistent with the theory in which electron inertia has a dominant role. The nonlinear behavior of the mode is found to be quite similar for both codes. Full reconnection in the Alfven time scale is observed along with the electrostatic potential structures created during the full reconnection phase. The E x B drift due to this electrostatic potential dominates the nonlinear phase of the development after the full reconnection
International Nuclear Information System (INIS)
Rao, N.N.
1998-01-01
A systematic analysis of the stationary propagation of nonlinearly coupled electromagnetic and ion-acoustic waves in an unmagnetized plasma via the ponderomotive force is carried out. For small but finite amplitudes, the governing equations have a Hamiltonian structure, but with a kinetic energy term that is not positive definite. The Hamiltonian is similar to the well-known Hacute enon endash Heiles Hamiltonian of nonlinear dynamics, and is completely integrable in three regimes of the allowed parameter space. The corresponding second invariants of motion are also explicitly obtained. The integrable parameter regimes correspond to supersonic values of the Mach number, which characterizes the propagation speed of the coupled waves. On the other hand, in the sub- as well as near-sonic regimes, the coupled mode equations admit different types of exact analytical solutions, which represent nonlinear localized eigenstates of the electromagnetic field trapped in the density cavity due to the ponderomotive potential. While the density cavity has always a single-dip structure, for larger amplitudes it can support higher-order modes having a larger number of nodes in the electromagnetic field. In particular, we show the existence of a new type of localized electromagnetic wave whose field intensity has a triple-hump structure. For typical parameter values, the triple-hump solitons propagate with larger Mach numbers that are closer to the sonic limit than the single- as well as the double-hump solitons, but carry a lesser amount of the electromagnetic field energy. A comparison between the different types of solutions is carried out. The possibility of the existence of trapped electromagnetic modes having a larger number of humps is also discussed. copyright 1998 American Institute of Physics
Alfven Waves in Gyrokinetic Plasmas
International Nuclear Information System (INIS)
Lee, W.W.; Qin, H.
2003-01-01
A brief comparison of the properties of Alfven waves that are based on the gyrokinetic description with those derived from the MHD equations is presented. The critical differences between these two approaches are the treatment of the ion polarization effects. As such, the compressional Alfven waves in a gyrokinetic plasma can be eliminated through frequency ordering, whereas geometric simplifications are needed to decouple the shear Alfven waves from the compressional Alfven waves within the context of MHD. Theoretical and numerical procedures of using gyrokinetic particle simulation for studying microturbulence and kinetic-MHD physics including finite Larmor radius effects are also presented
Preconditioned Inexact Newton for Nonlinear Sparse Electromagnetic Imaging
Desmal, Abdulla; Bagci, Hakan
2014-01-01
Newton-type algorithms have been extensively studied in nonlinear microwave imaging due to their quadratic convergence rate and ability to recover images with high contrast values. In the past, Newton methods have been implemented in conjunction with smoothness promoting optimization/regularization schemes. However, this type of regularization schemes are known to perform poorly when applied in imagining domains with sparse content or sharp variations. In this work, an inexact Newton algorithm is formulated and implemented in conjunction with a linear sparse optimization scheme. A novel preconditioning technique is proposed to increase the convergence rate of the optimization problem. Numerical results demonstrate that the proposed framework produces sharper and more accurate images when applied in sparse/sparsified domains.
Preconditioned Inexact Newton for Nonlinear Sparse Electromagnetic Imaging
Desmal, Abdulla
2014-05-04
Newton-type algorithms have been extensively studied in nonlinear microwave imaging due to their quadratic convergence rate and ability to recover images with high contrast values. In the past, Newton methods have been implemented in conjunction with smoothness promoting optimization/regularization schemes. However, this type of regularization schemes are known to perform poorly when applied in imagining domains with sparse content or sharp variations. In this work, an inexact Newton algorithm is formulated and implemented in conjunction with a linear sparse optimization scheme. A novel preconditioning technique is proposed to increase the convergence rate of the optimization problem. Numerical results demonstrate that the proposed framework produces sharper and more accurate images when applied in sparse/sparsified domains.
Preconditioned Inexact Newton for Nonlinear Sparse Electromagnetic Imaging
Desmal, Abdulla
2014-01-06
Newton-type algorithms have been extensively studied in nonlinear microwave imaging due to their quadratic convergence rate and ability to recover images with high contrast values. In the past, Newton methods have been implemented in conjunction with smoothness promoting optimization/regularization schemes. However, this type of regularization schemes are known to perform poorly when applied in imagining domains with sparse content or sharp variations. In this work, an inexact Newton algorithm is formulated and implemented in conjunction with a linear sparse optimization scheme. A novel preconditioning technique is proposed to increase the convergence rate of the optimization problem. Numerical results demonstrate that the proposed framework produces sharper and more accurate images when applied in sparse/sparsified domains.
Nonlinear interactions of electromagnetic waves with the auroral ionosphere
Wong, Alfred Y.
1999-09-01
The ionosphere provides us with an opportunity to perform plasma experiments in an environment with long confinement times, very large-scale lengths, and no confining walls. The auroral ionosphere with its nearly vertical magnetic field geometry is uniquely endowed with large amount of free energy from electron and ion precipitation along the magnetic field and mega-ampere current across the magnetic field. To take advantage of this giant outdoor laboratory, two facilities HAARP and HIPAS, with frequencies ranging from the radio to optical bands, are now available for active probing of and interaction with this interesting region. The ponderomotive pressures from the self-consistent wave fields have produced significant local perturbations of density and particle distributions at heights where the incident EM frequency matches a plasma resonance. This paper will review theory and experiments covering the nonlinear phenomena of parametric decay instability to wave collapse processes. At HF frequencies plasma lenses can be created by preconditioning pulses to focus what is a normally divergent beam into a high-intensity spot to further enhance nonlinear phenomena. At optical wavelengths a large rotating liquid metal mirror is used to focus laser pulses up to a given height. Such laser pulses are tuned to the same wavelengths of selected atomic and molecular resonances, with resulting large scattering cross sections. Ongoing experiments on dual-site experiments and excitation of ELF waves will be presented. The connection of such basic studies to environmental applications will be discussed. Such applications include the global communication using ELF waves, the ozone depletion and remediation and the control of atmospheric CO2 through the use of ion cyclotron resonant heating.
Excitation of plasma waves by nonlinear currents induced by a high-frequency electromagnetic pulse
Energy Technology Data Exchange (ETDEWEB)
Grishkov, V. E.; Uryupin, S. A., E-mail: uryupin@sci.lebedev.ru [Russian Academy of Sciences, Lebedev Physical Institute (Russian Federation)
2017-03-15
Excitation of plasma waves by nonlinear currents induced by a high-frequency electromagnetic pulse is analyzed within the kinetic approach. It is shown that the most efficient source of plasma waves is the nonlinear current arising due to the gradient of the energy density of the high-frequency field. Generation of plasma waves by the drag current is usually less efficient but not negligibly small at relatively high frequencies of electron–ion collisions. The influence of electron collisions on the excitation of plasma waves by pulses of different duration is described quantitatively.
Nonlinear oscillation regime of electromagnetic disturbances in the equatorial F region
International Nuclear Information System (INIS)
Sazonov, S.V.
1990-01-01
Nonlinear oscillation regime of electromagnetic dicturbances within equatorial ionosphere F-region resulted from Rayleigh-Taylor instability, gradient-drift instability and recombination processes is investigated on the basis of two-liquid quasihydrodynamics equations. It is shown, that at positive linear increment the oscillations are developing in regime with aggregation and are terminated by increment the effect of threshold destabilization, when under certain initial conditions underlgoes oscillation nonlinear swinging, resulting, as well, in bubble formation in contrast to small damping oscillations, is detected
Some models of propagation of extremely short electromagnetic pulses in a nonlinear medium
International Nuclear Information System (INIS)
Maimistov, Andrei I
2000-01-01
Some cases of model media considered in this paper allow analytical solutions to nonlinear wave equations to be found and the time dependence of the electric field strength to be determined in the explicit form for arbitrarily short electromagnetic pulses. Our analysis does not employ any assumptions concerning a harmonic carrier wave or the variation rate of the field in such pulses. The class of models considered includes two-level resonance and quasi-resonance systems. Nonresonance media are analysed in terms of models of anharmonic oscillators - the Duffing and Lorentz models. In most cases, only particular solutions describing the stationary propagation of a video pulse (a unipolar transient of the electric field or a pulse including a small number of oscillations of the electric field around zero) can be found. These solutions correspond to sufficiently strong electromagnetic fields when the dispersion inherent in the medium is suppressed by nonlinear processes. (invited paper)
Shoji, Masafumi; Miyoshi, Yoshizumi; Katoh, Yuto; Keika, Kunihiro; Angelopoulos, Vassilis; Kasahara, Satoshi; Asamura, Kazushi; Nakamura, Satoko; Omura, Yoshiharu
2017-09-01
Electromagnetic plasma waves are thought to be responsible for energy exchange between charged particles in space plasmas. Such an energy exchange process is evidenced by phase space holes identified in the ion distribution function and measurements of the dot product of the plasma wave electric field and the ion velocity. We develop a method to identify ion hole formation, taking into consideration the phase differences between the gyromotion of ions and the electromagnetic ion cyclotron (EMIC) waves. Using this method, we identify ion holes in the distribution function and the resulting nonlinear EMIC wave evolution from Time History of Events and Macroscale Interactions during Substorms (THEMIS) observations. These ion holes are key to wave growth and frequency drift by the ion currents through nonlinear wave-particle interactions, which are identified by a computer simulation in this study.
Electromagnetic effects on the self-modulation of nonlinear lower hybrid waves
International Nuclear Information System (INIS)
Hsu, P.; Kuehl, H.H.
1983-01-01
Electromagnetic effects on the self-modulation of nonlinear lower hybrid waves in an inhomogeneous plasma are studied for both broad and narrow spectrum excitations. For broad spectrum excitation, the complex modified Korteweg--de Vries equation is modified by two additional terms due to the electromagnetic correction and inhomogeneity. Numerical solutions of this equation for typical tokamak parameters show that these terms suppress soliton formation. For narrow spectrum excitation, the electromagnetic correction produces an additional dispersive term in the differential equation governing the wave envelope. This term opposes thermal dispersion, resulting in significant self-modulation. Numerical solutions show constriction and splitting of the envelope as well as spreading of the Fourier spectrum
Energy Technology Data Exchange (ETDEWEB)
T.S. Hahm; Z. Lin; P.H. Diamond; G. Rewoldt; W.X. Wang; S. Ethier; O. Gurcan; W.W. Lee; W.M. Tang
2004-12-21
An integrated program of gyrokinetic particle simulation and theory has been developed to investigate several outstanding issues in both turbulence and neoclassical physics. Gyrokinetic particle simulations of toroidal ion temperature gradient (ITG) turbulence spreading using the GTC code and its related dynamical model have been extended to the case with radially increasing ion temperature gradient, to study the inward spreading of edge turbulence toward the core. Due to turbulence spreading from the edge, the turbulence intensity in the core region is significantly enhanced over the value obtained from simulations of the core region only. Even when the core gradient is within the Dimits shift regime (i.e., self-generated zonal flows reduce the transport to a negligible value), a significant level of turbulence and transport is observed in the core due to spreading from the edge. The scaling of the turbulent front propagation speed is closer to the prediction from our nonlinear diffusion model than one based on linear toroidal coupling. A calculation of ion poloidal rotation in the presence of sharp density and toroidal angular rotation frequency gradients from the GTC-Neo particle simulation code shows that the results are significantly different from the conventional neoclassical theory predictions. An energy conserving set of a fully electromagnetic nonlinear gyrokinetic Vlasov equation and Maxwell's equations, which is applicable to edge turbulence, is being derived via the phase-space action variational Lie perturbation method. Our generalized ordering takes the ion poloidal gyroradius to be on the order of the radial electric field gradient length.
International Nuclear Information System (INIS)
Hahm, T.S.; Lin, Z.; Diamond, P.H.; Gurcan, O.; Rewoldt, G.; Wang, W.X.; Ethier, S.; Lee, W.W.; Lewandowski, J.L.V.; Tang, W.M.
2005-01-01
An integrated program of gyrokinetic particle simulation and theory has been developed to investigate several outstanding issues in both turbulence and neoclassical physics. Gyrokinetic particle simulations of toroidal ion temperature gradient (ITG) turbulence spreading using the GTC code and its related dynamical model have been extended to the case with radially increasing ion temperature gradient, to study the inward spreading of edge turbulence toward the core. Due to turbulence spreading from the edge, the turbulence intensity in the core region is significantly enhanced over the value obtained from simulations of the core region only. Even when the core gradient is within the Dimits shift regime (i.e., self-generated zonal flows reduce the transport to a negligible value), a significant level of turbulence and transport is observed in the core due to spreading from the edge. The scaling of the turbulent front propagation speed is closer to the prediction from our nonlinear diffusion model than one based on linear toroidal coupling. A calculation of ion poloidal rotation in the presence of sharp density and toroidal angular rotation frequency gradients from the GTC-Neo particle simulation code shows that the results are significantly different from the conventional neoclassical theory predictions. An energy conserving set of a fully electromagnetic nonlinear gyrokinetic Vlasov equation and Maxwell's equations, which is applicable to edge turbulence, is being derived via the phase-space action variational Lie perturbation method. Our generalized ordering takes the ion poloidal gyroradius to be on the order of the radial electric field gradient length. (author)
Linear relativistic gyrokinetic equation in general magnetically confined plasmas
International Nuclear Information System (INIS)
Tsai, S.T.; Van Dam, J.W.; Chen, L.
1983-08-01
The gyrokinetic formalism for linear electromagnetic waves of arbitrary frequency in general magnetic-field configurations is extended to include full relativistic effects. The derivation employs the small adiabaticity parameter rho/L 0 where rho is the Larmor radius and L 0 the equilibrium scale length. The effects of the plasma and magnetic field inhomogeneities and finite Larmor-radii effects are also contained
Harmonic balance finite element method applications in nonlinear electromagnetics and power systems
Lu, Junwei; Yamada, Sotoshi
2016-01-01
The first book applying HBFEM to practical electronic nonlinear field and circuit problems * Examines and solves wide aspects of practical electrical and electronic nonlinear field and circuit problems presented by HBFEM * Combines the latest research work with essential background knowledge, providing an all-encompassing reference for researchers, power engineers and students of applied electromagnetics analysis * There are very few books dealing with the solution of nonlinear electric- power-related problems * The contents are based on the authors' many years' research and industry experience; they approach the subject in a well-designed and logical way * It is expected that HBFEM will become a more useful and practical technique over the next 5 years due to the HVDC power system, renewable energy system and Smart Grid, HF magnetic used in DC/DC converter, and Multi-pulse transformer for HVDC power supply * HBFEM can provide effective and economic solutions to R&D product development * Includes Matlab e...
Nonlinear electromagnetic fields in 0.5 MHz inductively coupled plasmas
DEFF Research Database (Denmark)
Ostrikov, K.N.; Tsakadze, E.L.; Xu, S.
2003-01-01
Radial profiles of magnetic fields in the electrostatic (E) and electromagnetic (H) modes of low-frequency (similar to500 kHz) inductively coupled plasmas have been measured using miniature magnetic probes. In the low-power (similar to170 W) E-mode, the magnetic field pattern is purely linear......, with the fundamental frequency harmonics only. After transition to higher-power (similar to1130 W) H-mode, the second-harmonic nonlinear azimuthal magnetic field B-phi(2omega) that is in 4-6 times larger than the fundamental frequency component B-phi(omega), has been observed. A simplified plasma fluid model...... explaining the generation of the second harmonics of the azimuthal magnetic field in the plasma source is proposed. The nonlinear second harmonic poloidal (r-z) rf current generating the azimuthal magnetic field B-phi(2omega) is attributed to nonlinear interactions between the fundamental frequency radial...
Gyrokinetic simulations of turbulent transport: size scaling and chaotic behaviour
International Nuclear Information System (INIS)
Villard, L; Brunner, S; Casati, A; Aghdam, S Khosh; Lapillonne, X; McMillan, B F; Bottino, A; Dannert, T; Goerler, T; Hatzky, R; Jenko, F; Merz, F; Chowdhury, J; Ganesh, R; Garbet, X; Grandgirard, V; Latu, G; Sarazin, Y; Idomura, Y; Jolliet, S
2010-01-01
Important steps towards the understanding of turbulent transport have been made with the development of the gyrokinetic framework for describing turbulence and with the emergence of numerical codes able to solve the set of gyrokinetic equations. This paper presents some of the main recent advances in gyrokinetic theory and computing of turbulence. Solving 5D gyrokinetic equations for each species requires state-of-the-art high performance computing techniques involving massively parallel computers and parallel scalable algorithms. The various numerical schemes that have been explored until now, Lagrangian, Eulerian and semi-Lagrangian, each have their advantages and drawbacks. A past controversy regarding the finite size effect (finite ρ * ) in ITG turbulence has now been resolved. It has triggered an intensive benchmarking effort and careful examination of the convergence properties of the different numerical approaches. Now, both Eulerian and Lagrangian global codes are shown to agree and to converge to the flux-tube result in the ρ * → 0 limit. It is found, however, that an appropriate treatment of geometrical terms is necessary: inconsistent approximations that are sometimes used can lead to important discrepancies. Turbulent processes are characterized by a chaotic behaviour, often accompanied by bursts and avalanches. Performing ensemble averages of statistically independent simulations, starting from different initial conditions, is presented as a way to assess the intrinsic variability of turbulent fluxes and obtain reliable estimates of the standard deviation. Further developments concerning non-adiabatic electron dynamics around mode-rational surfaces and electromagnetic effects are discussed.
Ganguli, G.; Crabtree, C. E.; Rudakov, L.; Mithaiwala, M.
2014-12-01
Velocity ring instabilities are a common naturally occuring magnetospheric phenomenon that can also be generated by man made ionospheric experiments. These instabilities are known to generate lower-hybrid waves, which generally cannot propagte out of the source region. However, nonlinear wave physics can convert these linearly driven electrostatic lower-hybrid waves into electromagnetic waves that can escape the source region. These nonlinearly generated waves can be an important source of VLF turbulence that controls the trapped electron lifetime in the radiation belts. We develop numerical solutions to the wave-kinetic equation in a periodic box including the effects of nonlinear (NL) scattering (nonlinear Landau damping) of Lower-hybrid waves giving the evolution of the wave-spectra in wavenumber space. Simultaneously we solve the particle diffusion equation of both the background plasma particles and the ring ions, due to both linear and nonlinear Landau resonances. At initial times for cold ring ions, an electrostatic beam mode is excited, while the kinetic mode is stable. As the instability progresses the ring ions heat, the beam mode is stabilized, and the kinetic mode destabilizes. When the amplitude of the waves becomes sufficient the lower-hybrid waves are scattered (by either nearly unmagnetized ions or magnetized electrons) into electromagnetic magnetosonic waves [Ganguli et al 2010]. The effect of NL scattering is to limit the amplitude of the waves, slowing down the quasilinear relaxation time and ultimately allowing more energy from the ring to be liberated into waves [Mithaiwala et al. 2011]. The effects of convection out of the instability region are modeled, additionally limiting the amplitude of the waves, allowing further energy to be liberated from the ring [Scales et al., 2012]. Results are compared to recent 3D PIC simulations [Winske and Duaghton 2012].
Ulku, Huseyin Arda
2014-07-06
Effects of material nonlinearities on electromagnetic field interactions become dominant as field amplitudes increase. A typical example is observed in plasmonics, where highly localized fields “activate” Kerr nonlinearities. Naturally, time domain solvers are the method of choice when it comes simulating these nonlinear effects. Oftentimes, finite difference time domain (FDTD) method is used for this purpose. This is simply due to the fact that explicitness of the FDTD renders the implementation easier and the material nonlinearity can be easily accounted for using an auxiliary differential equation (J.H. Green and A. Taflove, Opt. Express, 14(18), 8305-8310, 2006). On the other hand, explicit marching on-in-time (MOT)-based time domain integral equation (TDIE) solvers have never been used for the same purpose even though they offer several advantages over FDTD (E. Michielssen, et al., ECCOMAS CFD, The Netherlands, Sep. 5-8, 2006). This is because explicit MOT solvers have never been stabilized until not so long ago. Recently an explicit but stable MOT scheme has been proposed for solving the time domain surface magnetic field integral equation (H.A. Ulku, et al., IEEE Trans. Antennas Propag., 61(8), 4120-4131, 2013) and later it has been extended for the time domain volume electric field integral equation (TDVEFIE) (S. B. Sayed, et al., Pr. Electromagn. Res. S., 378, Stockholm, 2013). This explicit MOT scheme uses predictor-corrector updates together with successive over relaxation during time marching to stabilize the solution even when time step is as large as in the implicit counterpart. In this work, an explicit MOT-TDVEFIE solver is proposed for analyzing electromagnetic wave interactions on scatterers exhibiting Kerr nonlinearity. Nonlinearity is accounted for using the constitutive relation between the electric field intensity and flux density. Then, this relation and the TDVEFIE are discretized together by expanding the intensity and flux - sing half
Hamiltonian reductions in plasma physics about intrinsic gyrokinetic
International Nuclear Information System (INIS)
Guillebon de Resnes, L. de
2013-01-01
Gyrokinetic is a key model for plasma micro-turbulence, commonly used for fusion plasmas or small-scale astrophysical turbulence, for instance. The model still suffers from several issues, which could imply to reconsider the equations. This thesis dissertation clarifies three of them. First, one of the coordinates caused questions, both from a physical and from a mathematical point of view; a suitable constrained coordinate is introduced, which removes the issues from the theory and explains the intrinsic structures underlying the questions. Second, the perturbative coordinate transformation for gyrokinetic was computed only at lowest orders; explicit induction relations are obtained to go arbitrary order in the expansion. Third, the introduction of the coupling between the plasma and the electromagnetic field was not completely satisfactory; using the Hamiltonian structure of the dynamics, it is implemented in a more appropriate way, with strong consequences on the gyrokinetic equations, especially about their Hamiltonian structure. In order to address these three main points, several other results are obtained, for instance about the origin of the guiding-center adiabatic invariant, about a very efficient minimal guiding center transformation, or about an intermediate Hamiltonian model between Vlasov-Maxwell and gyrokinetic, where the characteristics include both the slow guiding-center dynamics and the fast gyro-angle dynamics. In addition, various reduction methods are used, introduced or developed, e.g. a Lie-transform of the equations of motion, a lifting method to transfer particle reductions to the corresponding Hamiltonian field dynamics, or a truncation method related both to Dirac's theory of constraints and to a projection onto a Lie-subalgebra. Besides gyrokinetic, this is useful to clarify other Hamiltonian reductions in plasma physics, for instance for incompressible or electrostatic dynamics, for magnetohydrodynamics, or for fluid closures including
Momentum transport in gyrokinetic turbulence
Energy Technology Data Exchange (ETDEWEB)
Buchholz, Rico
2016-07-01
In this thesis, the gyrokinetic-Vlasov code GKW is used to study turbulent transport, with a focus on radial transport of toroidal momentum. To support the studies on turbulent transport an eigenvalue solver has been implemented into GKW. This allows to find, not only the most unstable mode, but also subdominant modes. Furthermore it is possible to follow the modes in parameter scans. Furthermore, two fundamental mechanisms that can generate an intrinsic rotation have been investigated: profile shearing and the velocity nonlinearity. The study of toroidal momentum transport in a tokamak due to profile shearing reveals that the momentum flux can not be accurately described by the gradient in the turbulent intensity. Consequently, a description using the profile variation is used. A linear model has been developed that is able to reproduce the variations in the momentum flux as the profiles of density and temperature vary, reasonably well. It uses, not only the gradient length of density and temperature profile, but also their derivative, i.e. the second derivative of the logarithm of the temperature and the density profile. It is shown that both first as well as second derivatives contribute to the generation of a momentum flux. A difference between the linear and nonlinear simulations has been found with respect to the behaviour of the momentum flux. In linear simulations the momentum flux is independent of the normalized Larmor radius ρ{sub *}, whereas it is linear in ρ{sub *} for nonlinear simulations, provided ρ{sub *} is small enough (≤4.10{sup -3}). Nonlinear simulations reveal that the profile shearing can generate an intrinsic rotation comparable to that of current experiments. Under reactor conditions, however, the intrinsic rotation from the profile shearing is expected to be small due to the small normalized Larmor radius ρ{sub *}
Comparisons of 'Identical' Simulations by the Eulerian Gyrokinetic Codes GS2 and GYRO
Bravenec, R. V.; Ross, D. W.; Candy, J.; Dorland, W.; McKee, G. R.
2003-10-01
A major goal of the fusion program is to be able to predict tokamak transport from first-principles theory. To this end, the Eulerian gyrokinetic code GS2 was developed years ago and continues to be improved [1]. Recently, the Eulerian code GYRO was developed [2]. These codes are not subject to the statistical noise inherent to particle-in-cell (PIC) codes, and have been very successful in treating electromagnetic fluctuations. GS2 is fully spectral in the radial coordinate while GYRO uses finite-differences and ``banded" spectral schemes. To gain confidence in nonlinear simulations of experiment with these codes, ``apples-to-apples" comparisons (identical profile inputs, flux-tube geometry, two species, etc.) are first performed. We report on a series of linear and nonlinear comparisons (with overall agreement) including kinetic electrons, collisions, and shaped flux surfaces. We also compare nonlinear simulations of a DIII-D discharge to measurements of not only the fluxes but also the turbulence parameters. [1] F. Jenko, et al., Phys. Plasmas 7, 1904 (2000) and refs. therein. [2] J. Candy, J. Comput. Phys. 186, 545 (2003).
Weakly nonlinear electromagnetic waves in an electron-ion positron plasma
International Nuclear Information System (INIS)
Rizzato, F.B.; Schneider, R.S.; Dillenburg, D.
1987-01-01
The modulation of a high-frequency electromagnetic wave which is circulary polarized and propagates in a plasma made up of electrons, ions and positrons is investigated. The coefficient of the cubic nonlinear term in the Schroedinger equation may change sign as the relative particle concentrations vary, and consequently a marginal state of modulation instability may exist. To described the system in the neighbourhood of this state an appropriate equation is derived. Particular stationary solutions of this equation are envelope solitary waves, envelope Kinks and envelope hole solitary waves. The dependence of the amplitude of the solutions on the propagation velocity and the particle concentrations is discussed. (author) [pt
Intrinsic rotation with gyrokinetic models
International Nuclear Information System (INIS)
Parra, Felix I.; Barnes, Michael; Catto, Peter J.; Calvo, Iván
2012-01-01
The generation of intrinsic rotation by turbulence and neoclassical effects in tokamaks is considered. To obtain the complex dependences observed in experiments, it is necessary to have a model of the radial flux of momentum that redistributes the momentum within the tokamak in the absence of a preexisting velocity. When the lowest order gyrokinetic formulation is used, a symmetry of the model precludes this possibility, making small effects in the gyroradius over scale length expansion necessary. These effects that are usually small become important for momentum transport because the symmetry of the lowest order gyrokinetic formulation leads to the cancellation of the lowest order momentum flux. The accuracy to which the gyrokinetic equation needs to be obtained to retain all the physically relevant effects is discussed.
Gyrokinetic linearized Landau collision operator
DEFF Research Database (Denmark)
Madsen, Jens
2013-01-01
, which is important in multiple ion-species plasmas. Second, the equilibrium operator describes drag and diffusion of the magnetic field aligned component of the vorticity associated with the E×B drift. Therefore, a correct description of collisional effects in turbulent plasmas requires the equilibrium......The full gyrokinetic electrostatic linearized Landau collision operator is calculated including the equilibrium operator, which represents the effect of collisions between gyrokinetic Maxwellian particles. First, the equilibrium operator describes energy exchange between different plasma species...... operator, even for like-particle collisions....
Gyrokinetic magnetohydrodynamics and the associated equilibria
Lee, W. W.; Hudson, S. R.; Ma, C. H.
2017-12-01
The gyrokinetic magnetohydrodynamic (MHD) equations, related to the recent paper by W. W. Lee ["Magnetohydrodynamics for collisionless plasmas from the gyrokinetic perspective," Phys. Plasmas 23, 070705 (2016)], and their associated equilibria properties are discussed. This set of equations consists of the time-dependent gyrokinetic vorticity equation, the gyrokinetic parallel Ohm's law, and the gyrokinetic Ampere's law as well as the equations of state, which are expressed in terms of the electrostatic potential, ϕ, and the vector potential, A , and support both spatially varying perpendicular and parallel pressure gradients and the associated currents. The corresponding gyrokinetic MHD equilibria can be reached when ϕ→0 and A becomes constant in time, which, in turn, gives ∇.(J∥+J⊥)=0 and the associated magnetic islands, if they exist. Examples of simple cylindrical geometry are given. These gyrokinetic MHD equations look quite different from the conventional MHD equations, and their comparisons will be an interesting topic in the future.
Pullback Transformations in Gyrokinetic Theory
International Nuclear Information System (INIS)
Qin, H.; Tang, W.M.
2003-01-01
The Pullback transformation of the distribution function is a key component of the gyrokinetic theory. In this paper, a systematic treatment of this subject is presented, and results from applications of the uniform framework developed are reviewed. The focus is on providing a clear exposition of the basic formalism which arises from the existence of three distinct coordinate systems in gyrokinetic theory. The familiar gyrocenter coordinate system, where the gyromotion is decoupled from the rest of particle's dynamics, is non-canonical and non-fabric. On the other hand, Maxwell's equations, which are needed to complete a kinetic system, are initially only defined in the fabric laboratory phase space coordinate system. The pullback transformations provide a rigorous connection between the distribution functions in gyrocenter coordinates and Maxwell's equations in laboratory phase space coordinates. This involves the generalization of the usual moment integrals originally defined on the cotangent fiber of the phase space to the moment integrals on a general 6D symplectic manifold, is shown to be an important step in the proper formulation of gyrokinetic theory. The resultant systematic treatment of the moment integrals enabled by the pullback transformation. Without this vital element, a number of prominent physics features, such as the presence of the compressional Alfven wave and a proper description of the gyrokinetic equilibrium, cannot be readily recovered
SciDAC GSEP: Gyrokinetic Simulation of Energetic Particle Turbulence and Transport
Energy Technology Data Exchange (ETDEWEB)
Lin, Zhihong [Univ. of California, Irvine, CA (United States)
2017-12-30
Energetic particle (EP) confinement is a key physics issue for burning plasma experiment ITER, the crucial next step in the quest for clean and abundant energy, since ignition relies on self-heating by energetic fusion products (α-particles). Due to the strong coupling of EP with burning thermal plasmas, plasma confinement property in the ignition regime is one of the most uncertain factors when extrapolating from existing fusion devices to the ITER tokamak. EP population in current tokamaks are mostly produced by auxiliary heating such as neutral beam injection (NBI) and radio frequency (RF) heating. Remarkable progress in developing comprehensive EP simulation codes and understanding basic EP physics has been made by two concurrent SciDAC EP projects GSEP funded by the Department of Energy (DOE) Office of Fusion Energy Science (OFES), which have successfully established gyrokinetic turbulence simulation as a necessary paradigm shift for studying the EP confinement in burning plasmas. Verification and validation have rapidly advanced through close collaborations between simulation, theory, and experiment. Furthermore, productive collaborations with computational scientists have enabled EP simulation codes to effectively utilize current petascale computers and emerging exascale computers. We review here key physics progress in the GSEP projects regarding verification and validation of gyrokinetic simulations, nonlinear EP physics, EP coupling with thermal plasmas, and reduced EP transport models. Advances in high performance computing through collaborations with computational scientists that enable these large scale electromagnetic simulations are also highlighted. These results have been widely disseminated in numerous peer-reviewed publications including many Phys. Rev. Lett. papers and many invited presentations at prominent fusion conferences such as the biennial International Atomic Energy Agency (IAEA) Fusion Energy Conference and the annual meeting of the
Efficient Eulerian gyrokinetic simulations with block-structured grids
International Nuclear Information System (INIS)
Jarema, Denis
2017-01-01
Gaining a deep understanding of plasma microturbulence is of paramount importance for the development of future nuclear fusion reactors, because it causes a strong outward transport of heat and particles. Gyrokinetics has proven itself as a valid mathematical model to simulate such plasma microturbulence effects. In spite of the advantages of this model, nonlinear radially extended (or global) gyrokinetic simulations are still extremely computationally expensive, involving a very large number of computational grid points. Hence, methods that reduce the number of grid points without a significant loss of accuracy are a prerequisite to be able to run high-fidelity simulations. At the level of the mathematical model, the gyrokinetic approach achieves a reduction from six to five coordinates in comparison to the fully kinetic models. This reduction leads to an important decrease in the total number of computational grid points. However, the velocity space mixed with the radial direction still requires a very fine resolution in grid based codes, due to the disparities in the thermal speed, which are caused by a strong temperature variation along the radial direction. An attempt to address this problem by modifying the underlying gyrokinetic set of equations leads to additional nonlinear terms, which are the most expensive parts to simulate. Furthermore, because of these modifications, well-established and computationally efficient implementations developed for the original set of equations can no longer be used. To tackle such issues, in this thesis we introduce an alternative approach of blockstructured grids. This approach reduces the number of grid points significantly, but without changing the underlying mathematical model. Furthermore, our technique is minimally invasive and allows the reuse of a large amount of already existing code using rectilinear grids, modifications being necessary only on the block boundaries. Moreover, the block-structured grid can be
Efficient Eulerian gyrokinetic simulations with block-structured grids
Energy Technology Data Exchange (ETDEWEB)
Jarema, Denis
2017-01-20
Gaining a deep understanding of plasma microturbulence is of paramount importance for the development of future nuclear fusion reactors, because it causes a strong outward transport of heat and particles. Gyrokinetics has proven itself as a valid mathematical model to simulate such plasma microturbulence effects. In spite of the advantages of this model, nonlinear radially extended (or global) gyrokinetic simulations are still extremely computationally expensive, involving a very large number of computational grid points. Hence, methods that reduce the number of grid points without a significant loss of accuracy are a prerequisite to be able to run high-fidelity simulations. At the level of the mathematical model, the gyrokinetic approach achieves a reduction from six to five coordinates in comparison to the fully kinetic models. This reduction leads to an important decrease in the total number of computational grid points. However, the velocity space mixed with the radial direction still requires a very fine resolution in grid based codes, due to the disparities in the thermal speed, which are caused by a strong temperature variation along the radial direction. An attempt to address this problem by modifying the underlying gyrokinetic set of equations leads to additional nonlinear terms, which are the most expensive parts to simulate. Furthermore, because of these modifications, well-established and computationally efficient implementations developed for the original set of equations can no longer be used. To tackle such issues, in this thesis we introduce an alternative approach of blockstructured grids. This approach reduces the number of grid points significantly, but without changing the underlying mathematical model. Furthermore, our technique is minimally invasive and allows the reuse of a large amount of already existing code using rectilinear grids, modifications being necessary only on the block boundaries. Moreover, the block-structured grid can be
International Nuclear Information System (INIS)
Li Liang; Huang Guoxiang
2010-01-01
We present a systematic theoretical study to deal with linear and nonlinear light propagations in a Doppler-broadened three-level Λ system via electromagnetically induced transparency (EIT), with incoherent population exchange between two lower energy levels taken into account. Through a careful analysis of base state and linear excitation, we show that the EIT condition of the system is given by |Ω c | 2 γ 31 >>2γ 21 Δω D 2 , where Ω c is half the Rabi frequency of the control field, Δω D is the Doppler width, and γ jl is the decay rate of the coherence between states |j> and |l>. Under this condition, the effect of incoherent population exchange is insignificant, while dephasing dominates the decoherence of the system. This condition also ensures the validity of the weak nonlinear perturbation theory used in this work for solving the Maxwell-Bloch equations with inhomogeneous broadening. We then investigate the nonlinear propagation of the probe field and show that it is possible to form temporal optical solitons in the Doppler-broadened medium. Such solitons have ultraslow propagating velocity and can be generated in very low light power. The possibility of realizing (1+1)-dimensional and (2+1)-dimensional spatial optical solitons in the adiabatic regime of the system is also discussed.
Controlling the stability of nonlinear optical modes via electromagnetically induced transparency
Zhang, Kun; Liang, Yi-zeng; Lin, Ji; Li, Hui-jun
2018-02-01
We propose a scheme to generate and stabilize the high-dimensional spatial solitons via electromagnetically induced transparency (EIT). The system we consider is a resonant atomic ensemble having Λ configuration. We illustrate that under EIT conditions the equation satisfied by the probe field envelope is reduced to a saturable nonlinear Schrödinger equation with the trapping potential, provided by a far-detuned laser field and a random magnetic field. We present high-dimensional soliton solutions exhibiting many interesting characteristics, including diversity (i.e., many different types of soliton solutions can be found, including bright, ring multipole bright, ring multipole defect mode, multiring bright, multiring defect mode, and vortices solitons), the phase transition between bright soliton and higher-order defect modes (i.e., the phase transition can be realized by controlling the nonlinear coefficient or the intensity of the trapping potential), and stability (i.e., various solitons can be stabilized by the Gaussian potential provided by the far detuned laser field, or the random potential provided by the magnetic field). We also find that some solitons are the extension of the linear eigenmode, whereas others entirely derive from the role of nonlinearity. Compared with previous studies, we not only show the diverse soliton solutions in the same system but also find the boundary of the phase transition for the type of solitons. In addition, we present the possibility of using the random potential to stabilize various solitons and vortices.
Controlling fluctuations in an ITB and comparison with gyrokinetic simulations
Ernst, D. R.; Fiore, C. L.; Dominguez, A.; Podpaly, Y.; Reinke, M. L.; Terry, J. L.; Tsujii, N.; Bespamyatnov, I.; Churchill, M.; Greenwald, M.; Hubbard, A.; Hughes, J. W.; Lee, J.; Ma, Y.; Wolfe, S.; Wukitch, S.
2011-10-01
We have modulated on-axis ICRF minority heating to trigger fluctuations and core electron transport in Alcator C-Mod Internal Transport Barriers (ITB's). Temperature swings of 50% produced strong bursts of density fluctuations, measured by phase contrast imaging (PCI), while edge fluctuations from reflectometry, Mirnov coils, and gas puff imaging (GPI) simultaneously diminished. The PCI fluctuations are in phase with sawteeth, further evidence that they originate within the ITB foot. Linear gyrokinetic analysis with GS2 shows TEMs are driven unstable in the ITB by the on-axis heating, as in Refs.,. Nonlinear gyrokinetic simulations of turbulence in the ITB are compared with fluctuation data using a synthetic diagnostic. Strong ITB's were produced with high quality ion and electron profile data. Supported by U.S. DoE awards DE-FC02-99ER54512, DE-FG02-91ER54109, DE-FC02-08ER54966.
Partially linearized algorithms in gyrokinetic particle simulation
Energy Technology Data Exchange (ETDEWEB)
Dimits, A.M.; Lee, W.W.
1990-10-01
In this paper, particle simulation algorithms with time-varying weights for the gyrokinetic Vlasov-Poisson system have been developed. The primary purpose is to use them for the removal of the selected nonlinearities in the simulation of gradient-driven microturbulence so that the relative importance of the various nonlinear effects can be assessed. It is hoped that the use of these procedures will result in a better understanding of the transport mechanisms and scaling in tokamaks. Another application of these algorithms is for the improvement of the numerical properties of the simulation plasma. For instance, implementations of such algorithms (1) enable us to suppress the intrinsic numerical noise in the simulation, and (2) also make it possible to regulate the weights of the fast-moving particles and, in turn, to eliminate the associated high frequency oscillations. Examples of their application to drift-type instabilities in slab geometry are given. We note that the work reported here represents the first successful use of the weighted algorithms in particle codes for the nonlinear simulation of plasmas.
Partially linearized algorithms in gyrokinetic particle simulation
International Nuclear Information System (INIS)
Dimits, A.M.; Lee, W.W.
1990-10-01
In this paper, particle simulation algorithms with time-varying weights for the gyrokinetic Vlasov-Poisson system have been developed. The primary purpose is to use them for the removal of the selected nonlinearities in the simulation of gradient-driven microturbulence so that the relative importance of the various nonlinear effects can be assessed. It is hoped that the use of these procedures will result in a better understanding of the transport mechanisms and scaling in tokamaks. Another application of these algorithms is for the improvement of the numerical properties of the simulation plasma. For instance, implementations of such algorithms (1) enable us to suppress the intrinsic numerical noise in the simulation, and (2) also make it possible to regulate the weights of the fast-moving particles and, in turn, to eliminate the associated high frequency oscillations. Examples of their application to drift-type instabilities in slab geometry are given. We note that the work reported here represents the first successful use of the weighted algorithms in particle codes for the nonlinear simulation of plasmas
Global gyrokinetic simulations of TEM microturbulence
Vernay, T.; Brunner, S.; Villard, L.; McMillan, B. F.; Jolliet, S.; Bottino, A.; Görler, T.; Jenko, F.
2013-07-01
Global gyrokinetic simulations of electrostatic temperature-gradient-driven trapped-electron-mode (TEM) turbulence using the δf particle-in-cell code ORB5 are presented. The electron response is either fully kinetic or hybrid, i.e. considering kinetic trapped and adiabatic passing electrons. A linear benchmark in the TEM regime against the Eulerian-based code GENE is presented. Two different methods for controlling the numerical noise, based, respectively, on a Krook operator and a so-called coarse-graining approach, are discussed and successfully compared. Both linear and non-linear studies are carried out for addressing the issue of finite-ρ*-effects and finite electron collisionality on TEM turbulence. Electron collisions are found to damp TEMs through the detrapping process, while finite-ρ*-effects turn out to be important in the non-linear regime but very small in the linear regime. Finally, the effects of zonal flows on TEM turbulence are briefly considered as well and shown to be unimportant in the temperature-gradient-driven TEM regime. Consistently, basically no difference is found between linear and non-linear critical electron temperature gradients in the TEM regime.
Effects of collisions on conservation laws in gyrokinetic field theory
Energy Technology Data Exchange (ETDEWEB)
Sugama, H.; Nunami, M. [National Institute for Fusion Science, Toki 509-5292 (Japan); Department of Fusion Science, SOKENDAI (The Graduate University for Advanced Studies), Toki 509-5292 (Japan); Watanabe, T.-H. [Department of Physics, Nagoya University, Nagoya 464-8602 (Japan)
2015-08-15
Effects of collisions on conservation laws for toroidal plasmas are investigated based on the gyrokinetic field theory. Associating the collisional system with a corresponding collisionless system at a given time such that the two systems have the same distribution functions and electromagnetic fields instantaneously, it is shown how the collisionless conservation laws derived from Noether's theorem are modified by the collision term. Effects of the external source term added into the gyrokinetic equation can be formulated similarly with the collisional effects. Particle, energy, and toroidal momentum balance equations including collisional and turbulent transport fluxes are systematically derived using a novel gyrokinetic collision operator, by which the collisional change rates of energy and canonical toroidal angular momentum per unit volume in the gyrocenter space can be given in the conservative forms. The ensemble-averaged transport equations of particles, energy, and toroidal momentum given in the present work are shown to include classical, neoclassical, and turbulent transport fluxes which agree with those derived from conventional recursive formulations.
Toshmatov, Bobir; Stuchlík, Zdeněk; Schee, Jan; Ahmedov, Bobomurat
2018-04-01
The electromagnetic (EM) perturbations of the black hole solutions in general relativity coupled to nonlinear electrodynamics (NED) are studied for both electrically and magnetically charged black holes, assuming that the EM perturbations do not alter the spacetime geometry. It is shown that the effective potentials of the electrically and magnetically charged black holes related to test perturbative NED EM fields are related to the effective metric governing the photon motion, contrary to the effective potential of the linear electrodynamic (Maxwell) field that is related to the spacetime metric. Consequently, corresponding quasinormal (QN) frequencies differ as well. As a special case, we study new family of the NED black hole solutions which tend in the weak field limit to the Maxwell field, giving the Reissner-Nordström (RN) black hole solution. We compare the NED Maxwellian black hole QN spectra with the RN black hole QN spectra.
International Nuclear Information System (INIS)
Cheng Guangling; Hu Xiangming; Zhong Wenxue
2009-01-01
We show that Einstein-Podolsky-Rosen (EPR) light entanglement is obtainable via the resonant nonlinear interactions enhanced by electromagnetically induced transparency. A three-level system is used as a unified model, where two metastable states are coupled to each other via microwave, or Raman, or two-photon transition, and the upper metastable state is coupled to the excited state. A pair of inner sidebands is amplified as optical cavity modes via the transition from the excited state to the other metastable state. The analysis is presented by using the dressed-atom squeezed-transformed-mode approach. For a proper ratio of the amplitudes of the applied fields, the sum of the variances for two EPR-like operators approaches zero, which corresponds to EPR entanglement.
International Nuclear Information System (INIS)
Holm, D.D.; Kupershmidt, B.A.
1987-01-01
Four levels of nonlinear hydrodynamic description are presented for a nondissipative multicondensate solution of superfluids with vorticity. First, the multivelocity superfluid (MVSF) theory is extended to the case of a multivelocity superfluid plasma (MVSP), in which some of the superfluid condensates (protons, say) are charged and coupled electromagnetically to an additional, normal, charged fluid (electrons). The resulting drag-current density is derived due to the electromagnetic coupling of the condensates with the normal fluids. For the case of one charged condensate, the MVSP equations simplify to what we call superfluid Hall magnetohydrodynamics (SHMHD) in the approximation that displacement current and electron inertia are negligible, and local charge neutrality is imposed. The contribution of the charged condensate to the Hall drift force is determined. In turn, neglecting the Hall effect in SHMHD gives the equations of superfluid magnetohydrodynamics (SMHD). Each set of equations (MVSF, MVSP, SHMHD, and SMHD) is shown to be Hamiltonian and to possess a Poisson bracket associated with the dual space of a corresponding semidirect-product Lie algebra with a generalized two-cocycle defined on it. Topological conservation laws (helicities) associated with the kernels of these Lie algebras are also discussed as well as those associated physically with generalized Kelvin theorems for conservation of superfluid circulation around closed loops moving with the normal fluid
Global gyrokinetic simulation of Tokamak edge pedestal instabilities.
Wan, Weigang; Parker, Scott E; Chen, Yang; Yan, Zheng; Groebner, Richard J; Snyder, Philip B
2012-11-02
Global electromagnetic gyrokinetic simulations show the existence of near threshold conditions for both a high-n kinetic ballooning mode (KBM) and an intermediate-n kinetic version of peeling-ballooning mode (KPBM) in the edge pedestal of two DIII-D H-mode discharges. When the magnetic shear is reduced in a narrow region of steep pressure gradient, the KPBM is significantly stabilized, while the KBM is weakly destabilized and hence becomes the most-unstable mode. Collisions decrease the KBM's critical β and increase the growth rate.
A generalized gyrokinetic Poisson solver
International Nuclear Information System (INIS)
Lin, Z.; Lee, W.W.
1995-03-01
A generalized gyrokinetic Poisson solver has been developed, which employs local operations in the configuration space to compute the polarization density response. The new technique is based on the actual physical process of gyrophase-averaging. It is useful for nonlocal simulations using general geometry equilibrium. Since it utilizes local operations rather than the global ones such as FFT, the new method is most amenable to massively parallel algorithms
A non-linear 3D printed electromagnetic vibration energy harvester
International Nuclear Information System (INIS)
Constantinou, P; Roy, S
2015-01-01
This paper describes a novel electromagnetic energy harvester that exploits the low flexural modulus of ABS and comprises of a nonlinear mechanism to enhance the generated power and bandwidth. The device is printed using desktop additive manufacturing techniques (3D printing) that use thermoplastics. It has a ‘V’ spring topology and exhibits a softening spring non-linearity introduced through the magnetic arrangement, which introduces a monostable potential well. A model is presented and measurements correspond favourably. The produced prototype generates a peak power of approximately 2.5mW at a frame acceleration of 1g and has a power bandwidth of approximately 1.2→1.5Hz and 3.5→3.9Hz during up and down sweeps respectively. The device has a power density of 0.4mW/cm 3 at a frame acceleration of 1g and a density of 0.04mW/cm 3 from a generated power of 25μW at 0.1g. (paper)
Non-Maxwellian fast particle effects in gyrokinetic GENE simulations
Di Siena, A.; Görler, T.; Doerk, H.; Bilato, R.; Citrin, J.; Johnson, T.; Schneider, M.; Poli, E.; JET Contributors
2018-04-01
Fast ions have recently been found to significantly impact and partially suppress plasma turbulence both in experimental and numerical studies in a number of scenarios. Understanding the underlying physics and identifying the range of their beneficial effect is an essential task for future fusion reactors, where highly energetic ions are generated through fusion reactions and external heating schemes. However, in many of the gyrokinetic codes fast ions are, for simplicity, treated as equivalent-Maxwellian-distributed particle species, although it is well known that to rigorously model highly non-thermalised particles, a non-Maxwellian background distribution function is needed. To study the impact of this assumption, the gyrokinetic code GENE has recently been extended to support arbitrary background distribution functions which might be either analytical, e.g., slowing down and bi-Maxwellian, or obtained from numerical fast ion models. A particular JET plasma with strong fast-ion related turbulence suppression is revised with these new code capabilities both with linear and nonlinear gyrokinetic simulations. It appears that the fast ion stabilization tends to be less strong but still substantial with more realistic distributions, and this improves the quantitative power balance agreement with experiments.
Considering fluctuation energy as a measure of gyrokinetic turbulence
International Nuclear Information System (INIS)
Plunk, G G; Tatsuno, T; Dorland, W
2012-01-01
In gyrokinetic theory, there are two quadratic measures of fluctuation energy, left invariant under nonlinear interactions, that constrain turbulence. In a recent work (Plunk and Tatsuno 2011 Phys. Rev. Lett. 106 165003) we reported on the novel consequences that this constraint has for the direction and locality of spectral energy transfer. This paper builds on that previous work. We provide a detailed analysis in support of the results of Plunk and Tatsuno (2011 Phys. Rev. Lett. 106 165003), but significantly broaden the scope and use additional methods to address the problem of energy transfer. The perspective taken here is that the fluctuation energies are not merely formal invariants of an idealized model (two-dimensional gyrokinetics (Plunk et al 2010 J. Fluid Mech. 664 407–35)) but also general measures of gyrokinetic turbulence, i.e. quantities that can be used to predict the behavior of turbulence. Although many questions remain open, this paper collects evidence in favor of this perspective by demonstrating in several contexts that constrained spectral energy transfer governs the dynamics. (paper)
Fluid and gyrokinetic simulations of impurity transport at JET
DEFF Research Database (Denmark)
Nordman, H; Skyman, A; Strand, P
2011-01-01
Impurity transport coefficients due to ion-temperature-gradient (ITG) mode and trapped-electron mode turbulence are calculated using profile data from dedicated impurity injection experiments at JET. Results obtained with a multi-fluid model are compared with quasi-linear and nonlinear gyrokinetic...... simulation results obtained with the code GENE. The sign of the impurity convective velocity (pinch) and its various contributions are discussed. The dependence of the impurity transport coefficients and impurity peaking factor −∇nZ/nZ on plasma parameters such as impurity charge number Z, ion logarithmic...
Progress in gyrokinetic simulations of toroidal ITG turbulence
International Nuclear Information System (INIS)
Nevins, W.M.; Dimits, A.M.; Cohen, B.I.; Shumaker, D.E.
2001-01-01
The 3-D nonlinear toroidal gyrokinetic simulation code PG3EQ is used to study toroidal ion temperature gradient (ITG) driven turbulence - a key cause of the anomalous transport that limits tokamak plasma performance. Systematic studies of the dependence of ion thermal transport on various parameters and effects are presented, including dependence on E-vectorxB-vector and toroidal velocity shear, sensitivity to the force balance in simulations with radial temperature gradient variation, and the dependences on magnetic shear and ion temperature gradient. (author)
International Nuclear Information System (INIS)
Wen, Shulai; Liu, Ying; Zhao, Xiuchen; Cheng, Jingwei; Li, Hong
2014-01-01
Hcp-cobalt particles were successfully prepared by a liquid phase reduction method, and the microstructure, static magnetic properties, electromagnetic and microwave absorption properties of the cobalt particles with irregular shape were investigated in detail. The measured results indicate that the saturation magnetization was less than that of hcp-Co single crystals, and the coercivity was larger than that of bulk cobalt crystal. The permittivity presents multi-nonlinear dielectric resonance, which may result from the irregular shape containing parts of cutting angle of dodecahedron of cobalt particles. The real part of permeability decreases with the frequency, and the imaginary part has a wide resonant peak. The paraffin-based composite containing 70 wt% cobalt particles possessed strong absorption characteristics with a minimum RL of −38.97 dB at 10.81 GHz and an absorption band with RL under −10 dB from 8.72 to 13.26 GHz when the thickness is 1.8 mm, which exhibits excellent microwave absorption in middle and high frequency. The architectural design of material morphologies is important for improving microwave absorption properties toward future application. - Highlights: • Hcp-cobalt particles were prepared by a liquid phase reduction method. • The saturation magnetization was less than that of hcp-Co single crystals. • The permittivity presents multi-nonlinear dielectric resonance. • The real part of permeability decreases with frequency, and the imaginary part presents a wide resonant peak. • The paraffin-based composite possessed a minimum RL of −38.97 dB at 10.81 GHz
International Nuclear Information System (INIS)
Sugaya, Reiji
1989-01-01
General expressions of the matrix elements for nonlinear wave-particle scattering (nonlinear Landau and cyclotron damping) of electromagnetic and electrostatic waves in a homogeneous magnetized plasma are derived from the Vlasov-Maxwell equations. The kinetic wave equations obtained for electromagnetic waves are expressed by four-order tensors in the rotating and cartesian coordinates. No restrictions are imposed on the propagation angle to a uniform magnetic field, the Larmor radius, the frequencies, or the wave numbers. By electrostatic approximation of the dielectric tensor and the matrix elements the kinetic wave equations can be applied to the case in which two scattering waves are electrostatic or they are partially electrostatic. Further, the matrix elements in the limit of parallel or perpendicular propagation to the magnetic field are given. (author)
GYSELA, a full-f global gyrokinetic Semi-Lagrangian code for ITG turbulence simulations
International Nuclear Information System (INIS)
Grandgirard, V.; Sarazin, Y.; Garbet, X.; Dif-Pradalier, G.; Ghendrih, Ph.; Crouseilles, N.; Latu, G.; Sonnendruecker, E.; Besse, N.; Bertrand, P.
2006-01-01
This work addresses non-linear global gyrokinetic simulations of ion temperature gradient (ITG) driven turbulence with the GYSELA code. The particularity of GYSELA code is to use a fixed grid with a Semi-Lagrangian (SL) scheme and this for the entire distribution function. The 4D non-linear drift-kinetic version of the code already showns the interest of such a SL method which exhibits good properties of energy conservation in non-linear regime as well as an accurate description of fine spatial scales. The code has been upgrated to run 5D simulations of toroidal ITG turbulence. Linear benchmarks and non-linear first results prove that semi-lagrangian codes can be a credible alternative for gyrokinetic simulations
Ruuskanen, J.; Stenvall, A.; Lahtinen, V.; Pardo, E.
2017-02-01
Superconducting magnets are the most expensive series of components produced in the Large Hadron Collider (LHC) at the European Organization for Nuclear Research (CERN). When developing such magnets beyond state-of-the-art technology, one possible option is to use high-temperature superconductors (HTS) that are capable of tolerating much higher magnetic fields than low-temperature superconductors (LTS), carrying simultaneously high current densities. Significant cost reductions due to decreased prototype construction needs can be achieved by careful modelling of the magnets. Simulations are used, e.g. for designing magnets fulfilling the field quality requirements of the beampipe, and adequate protection by studying the losses occurring during charging and discharging. We model the hysteresis losses and the magnetic field nonlinearity in the beampipe as a function of the magnet’s current. These simulations rely on the minimum magnetic energy variation principle, with optimization algorithms provided by the open-source optimization library interior point optimizer. We utilize this methodology to investigate a research and development accelerator magnet prototype made of REBCO Roebel cable. The applicability of this approach, when the magnetic field dependence of the superconductor’s critical current density is considered, is discussed. We also scrutinize the influence of the necessary modelling decisions one needs to make with this approach. The results show that different decisions can lead to notably different results, and experiments are required to study the electromagnetic behaviour of such magnets further.
International Nuclear Information System (INIS)
Pack, M. V.; Camacho, R. M.; Howell, J. C.
2006-01-01
We present a theory describing the transients and rise times of the refractive Kerr nonlinearity which is enhanced using electromagnetically induced transparency (EIT). We restrict our analysis to the case of a pulsed signal field with continuous-wave EIT fields, and all fields are well below saturation. These restrictions enable the reduction of an EIT Kerr, four-level, density-matrix equation to a two-level Bloch-vector equation which has a simple and physically intuitive algebraic solution. The physically intuitive picture of a two-level Bloch vector provides insights that are easily generalized to more complex and experimentally realistic models. We consider generalization to the cases of Doppler broadening, many-level EIT systems (we consider the D1 line of 87 Rb), and optically thick media. For the case of optically thick media we find that the rise time of the refractive EIT Kerr effect is proportional to the optical thickness. The rise time of the refractive EIT Kerr effect sets important limitations for potential few-photon applications
Energy Technology Data Exchange (ETDEWEB)
Choubani, M., E-mail: mohsenchoubani3@yahoo.fr; Ben Mahrsia, R.; Bouzaiene, L.; Maaref, H.
2013-12-15
In this paper we explore the effects of the structural dimensions, applied electromagnetic fields, hydrostatic pressure and temperature on the nonlinear optical rectification (NOR) in Vertically Coupled InAs/GaAs Quantum Dots (VCQDs). The analytical expression of the NOR is analyzed by using the density matrix formalism, the effective mass and the Finite Difference Method (FDM). Obtained results show that the NOR obtained with this coupled system is not a monotonic function of the barrier width, electromagnetic fields, pressure and temperature. Also, calculated results reveal that the resonant peaks of the NOR can be blue-shifted or red-shifted energies depending on the energy of the lowest confined states in the VCQDs structure. In addition, this condition can be controlled by changes in the structural dimensions and the external proofs mentioned above. -- Highlights: • In this paper we explore the effects of the barrier width, applied electromagnetic fields, hydrostatic pressure and temperature on the nonlinear optical rectification (NOR) in Vertically Coupled InAs/GaAs Quantum Dots (VCQDs). • The calculated results reveal that the resonant peaks of the NOR can be blue-shifted to large photon energies or red-shifted to lower photon energies. • In this paper, all parameters: electromagnetic fields, pressure and temperature effects are introduced and investigated. • The resonant energy and the magnitude of the NOR are controlled and adjusted.
Limitations, insights and improvements to gyrokinetics
International Nuclear Information System (INIS)
Catto, Peter J.; Parra, Felix I.; Kagan, Grigory; Simakov, Andrei N.
2009-01-01
We first consider gyrokinetic quasineutrality limitations when evaluating the axisymmetric radial electric field in a non-turbulent tokamak by an improved examination of intrinsic ambipolarity. We next prove that the background ions in a pedestal of poloidal ion gyroradius scale must be Maxwellian and nearly isothermal in Pfirsch-Schlueter and banana regime tokamak plasmas, and then consider zonal flow behaviour in a pedestal. Finally, we focus on a simplifying procedure for our transport time scale hybrid gyrokinetic-fluid treatment that removes the limitations of gyrokinetic quasineutrality and remains valid in the pedestal.
A quasi-linear gyrokinetic transport model for tokamak plasmas
International Nuclear Information System (INIS)
Casati, A.
2009-10-01
After a presentation of some basics around nuclear fusion, this research thesis introduces the framework of the tokamak strategy to deal with confinement, hence the main plasma instabilities which are responsible for turbulent transport of energy and matter in such a system. The author also briefly introduces the two principal plasma representations, the fluid and the kinetic ones. He explains why the gyro-kinetic approach has been preferred. A tokamak relevant case is presented in order to highlight the relevance of a correct accounting of the kinetic wave-particle resonance. He discusses the issue of the quasi-linear response. Firstly, the derivation of the model, called QuaLiKiz, and its underlying hypotheses to get the energy and the particle turbulent flux are presented. Secondly, the validity of the quasi-linear response is verified against the nonlinear gyro-kinetic simulations. The saturation model that is assumed in QuaLiKiz, is presented and discussed. Then, the author qualifies the global outcomes of QuaLiKiz. Both the quasi-linear energy and the particle flux are compared to the expectations from the nonlinear simulations, across a wide scan of tokamak relevant parameters. Therefore, the coupling of QuaLiKiz within the integrated transport solver CRONOS is presented: this procedure allows the time-dependent transport problem to be solved, hence the direct application of the model to the experiment. The first preliminary results regarding the experimental analysis are finally discussed
A hybrid gyrokinetic ion and isothermal electron fluid code for astrophysical plasma
Kawazura, Y.; Barnes, M.
2018-05-01
This paper describes a new code for simulating astrophysical plasmas that solves a hybrid model composed of gyrokinetic ions (GKI) and an isothermal electron fluid (ITEF) Schekochihin et al. (2009) [9]. This model captures ion kinetic effects that are important near the ion gyro-radius scale while electron kinetic effects are ordered out by an electron-ion mass ratio expansion. The code is developed by incorporating the ITEF approximation into AstroGK, an Eulerian δf gyrokinetics code specialized to a slab geometry Numata et al. (2010) [41]. The new code treats the linear terms in the ITEF equations implicitly while the nonlinear terms are treated explicitly. We show linear and nonlinear benchmark tests to prove the validity and applicability of the simulation code. Since the fast electron timescale is eliminated by the mass ratio expansion, the Courant-Friedrichs-Lewy condition is much less restrictive than in full gyrokinetic codes; the present hybrid code runs ∼ 2√{mi /me } ∼ 100 times faster than AstroGK with a single ion species and kinetic electrons where mi /me is the ion-electron mass ratio. The improvement of the computational time makes it feasible to execute ion scale gyrokinetic simulations with a high velocity space resolution and to run multiple simulations to determine the dependence of turbulent dynamics on parameters such as electron-ion temperature ratio and plasma beta.
Equilibrium fluctuation energy of gyrokinetic plasma
International Nuclear Information System (INIS)
Krommes, J.A.; Lee, W.W.; Oberman, C.
1985-11-01
The thermal equilibrium electric field fluctuation energy of the gyrokinetic model of magnetized plasma is computed, and found to be smaller than the well-known result (k)/8π = 1/2T/[1 + (klambda/sub D/) 2 ] valid for arbitrarily magnetized plasmas. It is shown that, in a certain sense, the equilibrium electric field energy is minimum in the gyrokinetic regime. 13 refs., 2 figs
Grant, Ian S
1990-01-01
The Manchester Physics Series General Editors: D. J. Sandiford; F. Mandl; A. C. Phillips Department of Physics and Astronomy, University of Manchester Properties of Matter B. H. Flowers and E. Mendoza Optics Second Edition F. G. Smith and J. H. Thomson Statistical Physics Second Edition F. Mandl Electromagnetism Second Edition I. S. Grant and W. R. Phillips Statistics R. J. Barlow Solid State Physics Second Edition J. R. Hook and H. E. Hall Quantum Mechanics F. Mandl Particle Physics Second Edition B. R. Martin and G. Shaw the Physics of Stars Second Edition A. C. Phillips Computing for Scient
Neoclassical equilibrium in gyrokinetic simulations
International Nuclear Information System (INIS)
Garbet, X.; Dif-Pradalier, G.; Nguyen, C.; Sarazin, Y.; Grandgirard, V.; Ghendrih, Ph.
2009-01-01
This paper presents a set of model collision operators, which reproduce the neoclassical equilibrium and comply with the constraints of a full-f global gyrokinetic code. The assessment of these operators is based on an entropy variational principle, which allows one to perform a fast calculation of the neoclassical diffusivity and poloidal velocity. It is shown that the force balance equation is recovered at lowest order in the expansion parameter, the normalized gyroradius, hence allowing one to calculate correctly the radial electric field. Also, the conventional neoclassical transport and the poloidal velocity are reproduced in the plateau and banana regimes. The advantages and drawbacks of the various model operators are discussed in view of the requirements for neoclassical and turbulent transport.
Gyrokinetic Simulation of Global Turbulent Transport Properties in Tokamak Experiments
Energy Technology Data Exchange (ETDEWEB)
Wang, W.X.; Lin, Z.; Tang, W.M.; Lee, W.W.; Ethier, S.; Lewandowski, J.L.V.; Rewoldt, G.; Hahm, T.S.; Manickam, J.
2006-01-01
A general geometry gyro-kinetic model for particle simulation of plasma turbulence in tokamak experiments is described. It incorporates the comprehensive influence of noncircular cross section, realistic plasma profiles, plasma rotation, neoclassical (equilibrium) electric fields, and Coulomb collisions. An interesting result of global turbulence development in a shaped tokamak plasma is presented with regard to nonlinear turbulence spreading into the linearly stable region. The mutual interaction between turbulence and zonal flows in collisionless plasmas is studied with a focus on identifying possible nonlinear saturation mechanisms for zonal flows. A bursting temporal behavior with a period longer than the geodesic acoustic oscillation period is observed even in a collisionless system. Our simulation results suggest that the zonal flows can drive turbulence. However, this process is too weak to be an effective zonal flow saturation mechanism.
Transport modelling and gyrokinetic analysis of advanced high performance discharges
International Nuclear Information System (INIS)
Kinsey, J.E.; Imbeaux, F.; Staebler, G.M.; Budny, R.; Bourdelle, C.; Fukuyama, A.; Garbet, X.; Tala, T.; Parail, V.
2005-01-01
Predictive transport modelling and gyrokinetic stability analyses of demonstration hybrid (HYBRID) and advanced tokamak (AT) discharges from the International Tokamak Physics Activity (ITPA) profile database are presented. Both regimes have exhibited enhanced core confinement (above the conventional ITER reference H-mode scenario) but differ in their current density profiles. Recent contributions to the ITPA database have facilitated an effort to study the underlying physics governing confinement in these advanced scenarios. In this paper, we assess the level of commonality of the turbulent transport physics and the relative roles of the transport suppression mechanisms (i.e. E x B shear and Shafranov shift (α) stabilization) using data for select HYBRID and AT discharges from the DIII-D, JET and AUG tokamaks. GLF23 transport modelling and gyrokinetic stability analysis indicate that E x B shear and Shafranov shift stabilization play essential roles in producing the improved core confinement in both HYBRID and AT discharges. Shafranov shift stabilization is found to be more important in AT discharges than in HYBRID discharges. We have also examined the competition between the stabilizing effects of E x B shear and Shafranov shift stabilization and the destabilizing effects of higher safety factors and parallel velocity shear. Linear and nonlinear gyrokinetic simulations of idealized low and high safety factor cases reveal some interesting consequences. A low safety factor (i.e. HYBRID relevant) is directly beneficial in reducing the transport, and E x B shear stabilization can dominate parallel velocity shear destabilization allowing the turbulence to be quenched. However, at low-q/high current, Shafranov shift stabilization plays less of a role. Higher safety factors (as found in AT discharges), on the other hand, have larger amounts of Shafranov shift stabilization, but parallel velocity shear destabilization can prevent E x B shear quenching of the turbulent
Transport modeling and gyrokinetic analysis of advanced high performance discharges
International Nuclear Information System (INIS)
Kinsey, J.; Imbeaux, F.; Bourdelle, C.; Garbet, X.; Staebler, G.; Budny, R.; Fukuyama, A.; Tala, T.; Parail, V.
2005-01-01
Predictive transport modeling and gyrokinetic stability analyses of demonstration hybrid (HYBRID) and Advanced Tokamak (AT) discharges from the International Tokamak Physics Activity (ITPA) profile database are presented. Both regimes have exhibited enhanced core confinement (above the conventional ITER reference H-mode scenario) but differ in their current density profiles. Recent contributions to the ITPA database have facilitated an effort to study the underlying physics governing confinement in these advanced scenarios. In this paper, we assess the level of commonality of the turbulent transport physics and the relative roles of the transport suppression mechanisms (i.e. ExB shear and Shafranov shift (α) stabilization) using data for select HYBRID and AT discharges from the DIII-D, JET, and AUG tokamaks. GLF23 transport modeling and gyrokinetic stability analysis indicates that ExB shear and Shafranov shift stabilization play essential roles in producing the improved core confinement in both HYBRID and AT discharges. Shafranov shift stabilization is found to be more important in AT discharges than in HYBRID discharges. We have also examined the competition between the stabilizing effects of ExB shear and Shafranov shift stabilization and the destabilizing effects of higher safety factors and parallel velocity shear. Linear and nonlinear gyrokinetic simulations of idealized low and high safety factor cases reveals some interesting consequences. A low safety factor (i.e. HYBRID relevant) is directly beneficial in reducing the transport, and ExB shear stabilization can win out over parallel velocity shear destabilization allowing the turbulence to be quenched. However, at low-q/high current, Shafranov shift stabilization plays less of a role. Higher safety factors (as found in AT discharges), on the other hand, have larger amounts of Shafranov shift stabilization, but parallel velocity shear destabilization can prevent ExB shear quenching of the turbulent
Bakunov, M I; Maslov, A V; Bodrov, S B
2007-11-16
We show that the usual Fresnel formulas for a free-propagating pulse are not applicable for a forced terahertz electromagnetic pulse supported by an optical pulse at the end of a nonlinear crystal. The correct linear reflection and transmission coefficients that we derive show that such pulses can experience a gain or loss at the boundary. This energy change depends on linear dielectric constants only. We also predict a regime where a complete disappearance of the forced pulse under oblique incidence occurs, an effect that has no counterpart for free-propagating pulses.
Electromagnetic radiation and nonlinear energy flow in an electron beam-plasma system
Whelan, D. A.; Stenzel, R. L.
1985-01-01
It is shown that the unstable electron-plasma waves of a beam-plasma system can generate electromagnetic radiation in a uniform plasma. The generation mechanism is a scattering of the unstable electron plasma waves off ion-acoustic waves, producing electromagnetic waves whose frequency is near the local plasma frequency. The wave vector and frequency matching conditions of the three-wave mode coupling are experimentally verified. The electromagnetic radiation is observed to be polarized with the electric field parallel to the beam direction, and its source region is shown to be localized to the unstable plasma wave region. The frequency spectrum shows negligible intensity near the second harmonic of the plasma frequency. These results suggest that the observed electromagnetic radiation of type III solar bursts may be generated near the local plasma frequency and observed downstream where the wave frequency is near the harmonic of the plasma frequency.
Direct identification of predator-prey dynamics in gyrokinetic simulations
Energy Technology Data Exchange (ETDEWEB)
Kobayashi, Sumire, E-mail: sumire.kobayashi@lpp.polytechnique.fr; Gürcan, Özgür D [Laboratoire de Physique des Plasmas, CNRS, Paris-Sud, Ecole Polytechnique, UMR7648, F-91128 Palaiseau (France); Diamond, Patrick H. [University of California, San Diego, La Jolla, California 92093-0319 (United States)
2015-09-15
The interaction between spontaneously formed zonal flows and small-scale turbulence in nonlinear gyrokinetic simulations is explored in a shearless closed field line geometry. It is found that when clear limit cycle oscillations prevail, the observed turbulent dynamics can be quantitatively captured by a simple Lotka-Volterra type predator-prey model. Fitting the time traces of full gyrokinetic simulations by such a reduced model allows extraction of the model coefficients. Scanning physical plasma parameters, such as collisionality and density gradient, it was observed that the effective growth rates of turbulence (i.e., the prey) remain roughly constant, in spite of the higher and varying level of primary mode linear growth rates. The effective growth rate that was extracted corresponds roughly to the zonal-flow-modified primary mode growth rate. It was also observed that the effective damping of zonal flows (i.e., the predator) in the parameter range, where clear predator-prey dynamics is observed, (i.e., near marginal stability) agrees with the collisional damping expected in these simulations. This implies that the Kelvin-Helmholtz-like instability may be negligible in this range. The results imply that when the tertiary instability plays a role, the dynamics becomes more complex than a simple Lotka-Volterra predator prey.
International Nuclear Information System (INIS)
Bhattacharyya, B.; Chakraborty, B.
1979-01-01
Nonlinear corrections of a left and a right circularly polarized electromagnetic wave of the same frequency, propagating in the direction of a static and uniform magnetic field in a cold and collisionally damped two-component plasma, have been evaluated. The nonlinearly correct dispersion relation, self-generating nonlinear precessional rotation of the polarization ellipse of the wave and the shift in a wave parameter depend on linear combinations of products of the amplitude components taken two at a time and hence on the energies of the waves. Both in the low frequency resonance (that is when the ion cyclotron frequency equals the wave frequency) and in the high frequency resonance (that is when the electron cyclotron frequency equals the wave frequency), the self-precessional rate and wavenumber shift are found to be large and so have the possibility of detection in laboratory experiments. Moreover, for the limit leading to Alfven waves, these nonlinear effects have been found to have some interesting and significant properties. (Auth.)
Kunz, Paul; Meyer, David; Quraishi, Qudsia
2015-05-01
Within the class of nonlinear optical effects that exhibit sub-natural linewidth features, electromagnetically induced transparency (EIT) and nonlinear magneto-optical rotation (NMOR) stand out as having made dramatic impacts on various applications including atomic clocks, magnetometry, and single photon storage. A related effect, known as electromagnetically induced absorption (EIA), has received less attention in the literature. Here, we report on the first observation of EIA in cold atoms using the Hanle configuration, where a single laser beam is used to both pump and probe the atoms while sweeping a magnetic field through zero along the beam direction. We find that, associated with the EIA peak, a ``twist'' appears in the corresponding NMOR signal. A similar twist has been previously noted by Budker et al., in the context of warm vapor optical magnetometry, and was ascribed to optical pumping through nearby hyperfine levels. By studying this feature through numerical simulations and cold atom experiments, thus rendering the hyperfine levels well resolved, we enhance the understanding of the optical pumping mechanism behind it, and elucidate its relation to EIA. Finally, we demonstrate a useful application of these studies through a simple and rapid method for nulling background magnetic fields within our atom chip apparatus.
Gyrokinetic Magnetohydrodynamics and the Associated Equilibrium
Lee, W. W.; Hudson, S. R.; Ma, C. H.
2017-10-01
A proposed scheme for the calculations of gyrokinetic MHD and its associated equilibrium is discussed related a recent paper on the subject. The scheme is based on the time-dependent gyrokinetic vorticity equation and parallel Ohm's law, as well as the associated gyrokinetic Ampere's law. This set of equations, in terms of the electrostatic potential, ϕ, and the vector potential, ϕ , supports both spatially varying perpendicular and parallel pressure gradients and their associated currents. The MHD equilibrium can be reached when ϕ -> 0 and A becomes constant in time, which, in turn, gives ∇ . (J|| +J⊥) = 0 and the associated magnetic islands. Examples in simple cylindrical geometry will be given. The present work is partially supported by US DoE Grant DE-AC02-09CH11466.
1982-03-01
NUMB9ER 00 AU THOR(s) 8. CON7RACT OR GRANT .%Uv3ERHj) Frederick Bloom AFOSR-81-0171 PERFORMING ORGANIZATION NAME AND ADDRESS 10. PrOGRAK ELEMAE:NT...material coff -iceret which may be associated with a particular nonlinear dielectric substance. For most common nonlinear dielectric substance, e
Nonlinear response of the quantum Hall system to a strong electromagnetic radiation
International Nuclear Information System (INIS)
Avetissian, H.K.; Mkrtchian, G.F.
2016-01-01
We study nonlinear response of a quantum Hall system in semiconductor-hetero-structures via third harmonic generation process and nonlinear Faraday effect. We demonstrate that Faraday rotation angle and third harmonic radiation intensity have a characteristic Hall plateaus feature. These nonlinear effects remain robust against the significant broadening of Landau levels. We predict realization of an experiment through the observation of the third harmonic signal and Faraday rotation angle, which are within the experimental feasibility. - Highlights: • Nonlinear optical response of a quantum Hall system has specific plateaus feature. • This effect remains robust against the significant broadening of Landau levels. • It can be observed via the third harmonic signal and the nonlinear Faraday effect.
Global gyrokinetic simulation of tokamak transport
International Nuclear Information System (INIS)
Furnish, G.; Horton, W.; Kishimoto, Y.; LeBrun, M.J.; Tajima, T.
1998-10-01
A kinetic simulation code based on the gyrokinetic ion dynamics in global general metric (including a tokamak with circular or noncircular cross-section) has been developed. This gyrokinetic simulation is capable of examining the global and semi-global driftwave structures and their associated transport in a tokamak plasma. The authors investigate the property of the ion temperature gradient (ITG) or η i (η i ≡ ∂ ell nT i /∂ ell n n i ) driven drift waves in a tokamak plasma. The emergent semi-global drift wave modes give rise to thermal transport characterized by the Bohm scaling
Global full-f gyrokinetic simulations of plasma turbulence
Energy Technology Data Exchange (ETDEWEB)
Grandgirard, V [CEA/DSM/DRFC, Association Euratom-CEA, Cadarache, 13108 St Paul-lez-Durance (France); Sarazin, Y [CEA/DSM/DRFC, Association Euratom-CEA, Cadarache, 13108 St Paul-lez-Durance (France); Angelino, P [CEA/DSM/DRFC, Association Euratom-CEA, Cadarache, 13108 St Paul-lez-Durance (France); Bottino, A [Max Plank Institut fr Plasmaphysik, IPP-EURATOM AssociationGarching (Germany); Crouseilles, N [IRMA, Universite Louis Pasteur, 7, rue Rene Descartes, 67084 Strasbourg Cedex (France); Darmet, G [CEA/DSM/DRFC, Association Euratom-CEA, Cadarache, 13108 St Paul-lez-Durance (France); Dif-Pradalier, G [CEA/DSM/DRFC, Association Euratom-CEA, Cadarache, 13108 St Paul-lez-Durance (France); Garbet, X [CEA/DSM/DRFC, Association Euratom-CEA, Cadarache, 13108 St Paul-lez-Durance (France); Ghendrih, Ph [CEA/DSM/DRFC, Association Euratom-CEA, Cadarache, 13108 St Paul-lez-Durance (France); Jolliet, S [CRPP, Association Euratom-Confederation Suisse, EPFL, 1015 Lausanne (Switzerland); Latu, G [LaBRI, 341 Cours Liberation, 33405 Talence Cedex (France); Sonnendruecker, E [IRMA, Universite Louis Pasteur, 7, rue Rene Descartes, 67084 Strasbourg Cedex (France); Villard, L [CRPP, Association Euratom-Confederation Suisse, EPFL, 1015 Lausanne (Switzerland)
2007-12-15
Critical physical issues can be specifically tackled with the global full-f gyrokinetic code GYSELA. Three main results are presented. First, the self-consistent treatment of equilibrium and fluctuations highlights the competition between two compensation mechanisms for the curvature driven vertical charge separation, namely, parallel flow and polarization. The impact of the latter on the turbulent transport is discussed. In the non-linear regime, the benchmark with the Particle-In-Cell code ORB5 looks satisfactory. Second, the transport scaling with {rho}{sub *} is found to depend both on {rho}{sub *} itself and on the distance to the linear threshold. Finally, a statistical steady-state turbulent regime is achieved in a reduced version of GYSELA by prescribing a constant heat source.
Global full-f gyrokinetic simulations of plasma turbulence
International Nuclear Information System (INIS)
Grandgirard, V; Sarazin, Y; Angelino, P; Bottino, A; Crouseilles, N; Darmet, G; Dif-Pradalier, G; Garbet, X; Ghendrih, Ph; Jolliet, S; Latu, G; Sonnendruecker, E; Villard, L
2007-01-01
Critical physical issues can be specifically tackled with the global full-f gyrokinetic code GYSELA. Three main results are presented. First, the self-consistent treatment of equilibrium and fluctuations highlights the competition between two compensation mechanisms for the curvature driven vertical charge separation, namely, parallel flow and polarization. The impact of the latter on the turbulent transport is discussed. In the non-linear regime, the benchmark with the Particle-In-Cell code ORB5 looks satisfactory. Second, the transport scaling with ρ * is found to depend both on ρ * itself and on the distance to the linear threshold. Finally, a statistical steady-state turbulent regime is achieved in a reduced version of GYSELA by prescribing a constant heat source
Ulku, Huseyin Arda; Sayed, Sadeed Bin; Bagci, Hakan
2014-01-01
solvers are the method of choice when it comes simulating these nonlinear effects. Oftentimes, finite difference time domain (FDTD) method is used for this purpose. This is simply due to the fact that explicitness of the FDTD renders the implementation
Beyond scale separation in gyrokinetic turbulence
International Nuclear Information System (INIS)
Garbet, X.; Sarazin, Y.; Grandgirard, V.; Dif-Pradalier, G.; Darmet, G.; Ghendrih, Ph.; Angelino, P.; Bertrand, P.; Besse, N.; Gravier, E.; Morel, P.; Sonnendruecker, E.; Crouseilles, N.; Dischler, J.-M.; Latu, G.; Violard, E.; Brunetti, M.; Brunner, S.; Lapillonne, X.; Tran, T.-M.; Villard, L.; Boulet, M.
2007-01-01
This paper presents the results obtained with a set of gyrokinetic codes based on a semi-Lagrangian scheme. Several physics issues are addressed, namely, the comparison between fluid and kinetic descriptions, the intermittent behaviour of flux driven turbulence and the role of large scale flows in toroidal ITG turbulence. The question of the initialization of full-F simulations is also discussed
Bubble shape and electromagnetic field in the nonlinear regime for laser wakefield acceleration
International Nuclear Information System (INIS)
Li, X. F.; Yu, Q.; Huang, S.; Kong, Q.; Gu, Y. J.; Kawata, S.
2015-01-01
The electromagnetic field in the electron “bubble” regime for ultra-intense laser wakefield acceleration was solved using the d'Alembert equations. Ignoring the residual electrons, we assume an ellipsoidal bubble forms under ideal conditions, with bubble velocity equal to the speed of light in vacuum. The general solution for bubble shape and electromagnetic field were obtained. The results were confirmed in 2.5D PIC (particle-in-cell) simulations. Moreover, slopes for the longitudinal electric field of larger than 0.5 were found in these simulations. With spherical bubbles, this slope is always smaller than or equal to 0.5. This behavior validates the ellipsoid assumption
Non-linear diffusion of charged particles due to stochastic electromagnetic fields
International Nuclear Information System (INIS)
Martins, A.M.; Balescu, R.; Mendonca, J.T.
1989-01-01
It is well known that the energy confinement times observed in tokamak cannot be explained by the classical or neo-classical transport theory. The alternative explanations are based on the existence of various kinds of micro-instabilities, or on the stochastic destruction of the magnetic surfaces, due to the interaction of magnetic islands of different helicities. In the absence of a well established theory of anomalous transport it is perhaps important to study in some detail the diffusion coefficient of single charged particles in the presence of electromagnetic fluctuation, because it can provide the physical grounds for more complete and self-consistent calculations. In the present work we derive a general expression for the transverse diffusion coefficient of electrons and ions in a constant magnetic field and in the presence of space and time dependent electromagnetic fluctuation. We neglect macroscopic drifts due to inhomogeneity and field curvatures, but retain finite Larmor radius effects. (author) 3 refs
International Nuclear Information System (INIS)
Hamedi, H R; Ruseckas, J; Juzeliūnas, G
2017-01-01
We consider propagation of a probe pulse in an atomic medium characterized by a combined tripod and Lambda (Λ) atom-light coupling scheme. The scheme involves three atomic ground states coupled to two excited states by five light fields. It is demonstrated that dark states can be formed for such an atom-light coupling. This is essential for formation of the electromagnetically induced transparency (EIT) and slow light. In the limiting cases the scheme reduces to conventional Λ- or N -type atom-light couplings providing the EIT or absorption, respectively. Thus, the atomic system can experience a transition from the EIT to the absorption by changing the amplitudes or phases of control lasers. Subsequently the scheme is employed to analyze the nonlinear pulse propagation using the coupled Maxwell–Bloch equations. It is shown that a generation of stable slow light optical solitons is possible in such a five-level combined tripod and Λ atomic system. (paper)
Control of Nonlinear Coupled Electromagnetic Actuators for Active Drag Reduction in Turbulent Flow
Seidler, Florian; Trabert, Julius; Dück, Marcel; van Waasen, Stefan; Schiek, Michael; Abel, Dirk; Castelan, E. B.
2016-01-01
The research group FOR1779 “active drag reduction via wavy surface oscillations” develops robust methods for reduction of turbulent friction drag by flow control. The planned concentration on unsteady flow conditions requires a control of the electromagnetic actuator system for generation of transversal surface waves. The bars are positioned in parallel and coupled with an aluminum surface to generate a travelling wave perpendicular to the flow field. The actuator system can be approximately ...
Neoclassical simulation of tokamak plasmas using the continuum gyrokinetic code TEMPEST.
Xu, X Q
2008-07-01
We present gyrokinetic neoclassical simulations of tokamak plasmas with a self-consistent electric field using a fully nonlinear (full- f ) continuum code TEMPEST in a circular geometry. A set of gyrokinetic equations are discretized on a five-dimensional computational grid in phase space. The present implementation is a method of lines approach where the phase-space derivatives are discretized with finite differences, and implicit backward differencing formulas are used to advance the system in time. The fully nonlinear Boltzmann model is used for electrons. The neoclassical electric field is obtained by solving the gyrokinetic Poisson equation with self-consistent poloidal variation. With a four-dimensional (psi,theta,micro) version of the TEMPEST code, we compute the radial particle and heat fluxes, the geodesic-acoustic mode, and the development of the neoclassical electric field, which we compare with neoclassical theory using a Lorentz collision model. The present work provides a numerical scheme for self-consistently studying important dynamical aspects of neoclassical transport and electric field in toroidal magnetic fusion devices.
The role of zonal flows in the saturation of multi-scale gyrokinetic turbulence
Energy Technology Data Exchange (ETDEWEB)
Staebler, G. M.; Candy, J. [General Atomics, San Diego, California 92186 (United States); Howard, N. T. [Oak Ridge Institute for Science Education (ORISE), Oak Ridge, Tennessee 37831 (United States); Holland, C. [University of California San Diego, San Diego, California 92093 (United States)
2016-06-15
The 2D spectrum of the saturated electric potential from gyrokinetic turbulence simulations that include both ion and electron scales (multi-scale) in axisymmetric tokamak geometry is analyzed. The paradigm that the turbulence is saturated when the zonal (axisymmetic) ExB flow shearing rate competes with linear growth is shown to not apply to the electron scale turbulence. Instead, it is the mixing rate by the zonal ExB velocity spectrum with the turbulent distribution function that competes with linear growth. A model of this mechanism is shown to be able to capture the suppression of electron-scale turbulence by ion-scale turbulence and the threshold for the increase in electron scale turbulence when the ion-scale turbulence is reduced. The model computes the strength of the zonal flow velocity and the saturated potential spectrum from the linear growth rate spectrum. The model for the saturated electric potential spectrum is applied to a quasilinear transport model and shown to accurately reproduce the electron and ion energy fluxes of the non-linear gyrokinetic multi-scale simulations. The zonal flow mixing saturation model is also shown to reproduce the non-linear upshift in the critical temperature gradient caused by zonal flows in ion-scale gyrokinetic simulations.
Gyrokinetic simulations of ETG Turbulence*
Nevins, William
2005-10-01
Recent gyrokinetic simulations of electron temperature gradient (ETG) turbulence [1,2] produced different results despite similar plasma parameters. Ref.[1] differs from Ref.[2] in that [1] eliminates magnetically trapped particles ( r/R=0 ), while [2] retains magnetically trapped particles ( r/R 0.18 ). Differences between [1] and [2] have been attributed to insufficient phase-space resolution and novel physics associated with toroidicity and/or global simulations[2]. We have reproduced the results reported in [2] using a flux-tube, particle-in-cell (PIC) code, PG3EQ[3], thereby eliminating global effects as the cause of the discrepancy. We observe late-time decay of ETG turbulence and the steady-state heat transport in agreement with [2], and show this results from discrete particle noise. Discrete particle noise is a numerical artifact, so both the PG3EQ simulations reported here and those reported in Ref.[2] have little to say about steady-state ETG turbulence and the associated anomalous electron heat transport. Our attempts to benchmark PIC and continuum[4] codes at the plasma parameters used in Ref.[2] produced very large, intermittent transport. We will present an alternate benchmark point for ETG turbulence, where several codes reproduce the same transport levels. Parameter scans about this new benchmark point will be used to investigate the parameter dependence of ETG transport and to elucidate saturation mechanisms proposed in Refs.[1,2] and elsewhere[5-7].*In collaboration with A. Dimits (LLNL), J. Candy, C. Estrada-Mila (GA), W. Dorland (U of MD), F. Jenko, T. Dannert (Max-Planck Institut), and G. Hammett (PPPL). Work at LLNL performed for US DOE under Contract W7405-ENG-48.[1] F. Jenko and W. Dorland, PRL 89, 225001 (2002).[2] Z. Lin et al, 2004 Sherwood Mtg.; 2004 TTF Mtg.; Fusion Energy 2004 (IAEA, Vienna, 2005); Bull. Am. Phys. Soc. (November, 2004); 2005 TTF Mtg.; 2005 Sherwood Mtg.; Z. Lin, et al, Phys. Plasmas 12, 056125 (2005). [3] A.M. Dimits
International Nuclear Information System (INIS)
Lapillonne, X.
2010-04-01
In magnetically confined fusion devices, the energy and particle transport is significantly larger than expected from purely collisional processes. This degraded confinement mostly results from small-scale turbulence and prevents from reaching self-sustained burning plasma conditions in present day experiments. A better understanding of these nonlinear phenomena is therefore of key importance on the way towards controlled fusion. The small-scale microinstabilities and associated turbulence are investigated for Tokamak plasmas by means of numerical simulations in the frame of the gyrokinetic theory. This model describes the evolution of the particle distribution functions in phase space together with self-consistent electromagnetic fields, while neglecting the fast motion associated with the Larmor orbit of particles around the magnetic field lines. In the course of this thesis work, substantial modifications to the existing Eulerian gyrokinetic code GENE have been carried out in collaboration with the Max-Planck- Institute f¨ur Plasmaphysik in Garching, Germany. The code has been extended from a local approximation, which only considers a reduced volume of a fusion plasma, to a global version which fully includes radial temperature and density profiles as well as radial magnetic equilibrium variations. To this end, the gyrokinetic equations have been formulated for general magnetic geometry, keeping radial variations of equilibrium quantities, and considering field aligned coordinates, suitable for their numerical implementation. The numerical treatment of the radial direction has been modified from a Fourier representation in the local approach to real space in the global code. This has in particular required to adapt the radial derivatives, the field solver, and to implement a real space dealiasing scheme for the treatment of the nonlinearity. A heat source was in addition introduced to allow for steady state global nonlinear simulations. An important part of
Nonlinear Electromagnetic Waves and Spherical Arc-Polarized Waves in Space Plasmas
Tsurutani, B.; Ho, Christian M.; Arballo, John K.; Lakhina, Gurbax S.; Glassmeier, Karl-Heinz; Neubauer, Fritz M.
1997-01-01
We review observations of nonlinear plasma waves detected by interplanetary spacecraft. For this paper we will focus primarily on the phase-steepened properties of such waves. Plasma waves at comet Giacobini-Zinner measured by the International Cometary Explorer (ICE), at comets Halley and Grigg-Skjellerup measured by Giotto, and interplanetary Alfven waves measured by Ulysses, will be discussed and intercompared.
Gyrokinetic particle-in-cell simulations of plasma microturbulence on advanced computing platforms
International Nuclear Information System (INIS)
Ethier, S; Tang, W M; Lin, Z
2005-01-01
Since its introduction in the early 1980s, the gyrokinetic particle-in-cell (PIC) method has been very successfully applied to the exploration of many important kinetic stability issues in magnetically confined plasmas. Its self-consistent treatment of charged particles and the associated electromagnetic fluctuations makes this method appropriate for studying enhanced transport driven by plasma turbulence. Advances in algorithms and computer hardware have led to the development of a parallel, global, gyrokinetic code in full toroidal geometry, the gyrokinetic toroidal code (GTC), developed at the Princeton Plasma Physics Laboratory. It has proven to be an invaluable tool to study key effects of low-frequency microturbulence in fusion plasmas. As a high-performance computing applications code, its flexible mixed-model parallel algorithm has allowed GTC to scale to over a thousand processors, which is routinely used for simulations. Improvements are continuously being made. As the US ramps up its support for the International Tokamak Experimental Reactor (ITER), the need for understanding the impact of turbulent transport in burning plasma fusion devices is of utmost importance. Accordingly, the GTC code is at the forefront of the set of numerical tools being used to assess and predict the performance of ITER on critical issues such as the efficiency of energy confinement in reactors
International Nuclear Information System (INIS)
Khalil, Sh.M.; El-Sherif, N.; El-Siragy, N.M.; Tanta Univ.; El-Naggar, I.A.; Alexandria Univ.
1985-01-01
Investigation is made for nonlinear interaction between incident radiation and a surface wave in a magnetized plasma layer. Both interacting waves are of P polarization. The generated currents and fields at combination frequencies are obtained analytically. Unlike the S-polarized interacting waves, the magnetic field affects the fundamental waves and leads to an amplification of generated waves when their frequencies approach the cyclotron frequency. (author)
Directory of Open Access Journals (Sweden)
Irwin Yousept
2010-07-01
Full Text Available An optimal control problem arising in the context of 3D electromagnetic induction heating is investigated. The state equation is given by a quasilinear stationary heat equation coupled with a semilinear time harmonic eddy current equation. The temperature-dependent electrical conductivity and the presence of pointwise inequality state-constraints represent the main challenge of the paper. In the first part of the paper, the existence and regularity of the state are addressed. The second part of the paper deals with the analysis of the corresponding linearized equation. Some suffcient conditions are presented which guarantee thesolvability of the linearized system. The final part of the paper is concerned with the optimal control. The aim of the optimization is to find the optimal voltage such that a desired temperature can be achieved optimally. The corresponding first-order necessary optimality condition is presented.
Transport of momentum in full f gyrokinetics
International Nuclear Information System (INIS)
Parra, Felix I.; Catto, Peter J.
2010-01-01
Full f electrostatic gyrokinetic formulations employ two gyrokinetic equations, one for ions and the other for electrons, and quasineutrality to obtain the ion and electron distribution functions and the electrostatic potential. We demonstrate with several examples that the long wavelength radial electric field obtained with full f approaches is extremely sensitive to errors in the ion and electron density since small deviations in density give rise to large, nonphysical deviations in the conservation of toroidal angular momentum. For typical tokamak values, a relative error of 10 -7 in the ion or electron densities is enough to obtain the incorrect toroidal rotation. Based on the insights gained with the examples considered, three simple tests to check transport of toroidal angular momentum in full f simulations are proposed.
Parallel magnetic field perturbations in gyrokinetic simulations
International Nuclear Information System (INIS)
Joiner, N.; Hirose, A.; Dorland, W.
2010-01-01
At low β it is common to neglect parallel magnetic field perturbations on the basis that they are of order β 2 . This is only true if effects of order β are canceled by a term in the ∇B drift also of order β[H. L. Berk and R. R. Dominguez, J. Plasma Phys. 18, 31 (1977)]. To our knowledge this has not been rigorously tested with modern gyrokinetic codes. In this work we use the gyrokinetic code GS2[Kotschenreuther et al., Comput. Phys. Commun. 88, 128 (1995)] to investigate whether the compressional magnetic field perturbation B || is required for accurate gyrokinetic simulations at low β for microinstabilities commonly found in tokamaks. The kinetic ballooning mode (KBM) demonstrates the principle described by Berk and Dominguez strongly, as does the trapped electron mode, in a less dramatic way. The ion and electron temperature gradient (ETG) driven modes do not typically exhibit this behavior; the effects of B || are found to depend on the pressure gradients. The terms which are seen to cancel at long wavelength in KBM calculations can be cumulative in the ion temperature gradient case and increase with η e . The effect of B || on the ETG instability is shown to depend on the normalized pressure gradient β ' at constant β.
Gyrokinetic statistical absolute equilibrium and turbulence
International Nuclear Information System (INIS)
Zhu Jianzhou; Hammett, Gregory W.
2010-01-01
A paradigm based on the absolute equilibrium of Galerkin-truncated inviscid systems to aid in understanding turbulence [T.-D. Lee, Q. Appl. Math. 10, 69 (1952)] is taken to study gyrokinetic plasma turbulence: a finite set of Fourier modes of the collisionless gyrokinetic equations are kept and the statistical equilibria are calculated; possible implications for plasma turbulence in various situations are discussed. For the case of two spatial and one velocity dimension, in the calculation with discretization also of velocity v with N grid points (where N+1 quantities are conserved, corresponding to an energy invariant and N entropy-related invariants), the negative temperature states, corresponding to the condensation of the generalized energy into the lowest modes, are found. This indicates a generic feature of inverse energy cascade. Comparisons are made with some classical results, such as those of Charney-Hasegawa-Mima in the cold-ion limit. There is a universal shape for statistical equilibrium of gyrokinetics in three spatial and two velocity dimensions with just one conserved quantity. Possible physical relevance to turbulence, such as ITG zonal flows, and to a critical balance hypothesis are also discussed.
Gyrokinetic Statistical Absolute Equilibrium and Turbulence
International Nuclear Information System (INIS)
Zhu, Jian-Zhou; Hammett, Gregory W.
2011-01-01
A paradigm based on the absolute equilibrium of Galerkin-truncated inviscid systems to aid in understanding turbulence (T.-D. Lee, 'On some statistical properties of hydrodynamical and magnetohydrodynamical fields,' Q. Appl. Math. 10, 69 (1952)) is taken to study gyrokinetic plasma turbulence: A finite set of Fourier modes of the collisionless gyrokinetic equations are kept and the statistical equilibria are calculated; possible implications for plasma turbulence in various situations are discussed. For the case of two spatial and one velocity dimension, in the calculation with discretization also of velocity v with N grid points (where N + 1 quantities are conserved, corresponding to an energy invariant and N entropy-related invariants), the negative temperature states, corresponding to the condensation of the generalized energy into the lowest modes, are found. This indicates a generic feature of inverse energy cascade. Comparisons are made with some classical results, such as those of Charney-Hasegawa-Mima in the cold-ion limit. There is a universal shape for statistical equilibrium of gyrokinetics in three spatial and two velocity dimensions with just one conserved quantity. Possible physical relevance to turbulence, such as ITG zonal flows, and to a critical balance hypothesis are also discussed.
Non-physical momentum sources in slab geometry gyrokinetics
International Nuclear Information System (INIS)
Parra, Felix I; Catto, Peter J
2010-01-01
We investigate momentum transport in the Hamiltonian electrostatic gyrokinetic formulation of Dubin et al (1983 Phys. Fluids 26 3524). We prove that the long wavelength electric field obtained from the gyrokinetic quasineutrality introduces a non-physical momentum source in the low flow ordering.
Flux tube gyrokinetic simulations of the edge pedestal
Parker, Scott; Wan, Weigang; Chen, Yang
2011-10-01
The linear instabilities of DIII-D H-mode pedestal are studied with gyrokinetic micro-turbulence simulations. The simulation code GEM is an electromagnetic δf code with global tokamak geometry in the form of Miller equilibrium. Local flux tube simulations are carried out for multiple positions of two DIII-D profiles: shot #98889 and shot #131997. Near the top of the pedestal, the instability is clearly ITG. The dominant instability of the pedestal appears at the steep gradient region, and it is identified as a low frequency mode mostly driven by electron temperature gradient. The mode propagates along the electron diamagnetic direction for low n and may propagate along the ion direction for high n. At some positions near the steep gradient region, an ion instability is found which shows some characteristics of kinetic ballooning mode (KBM). These results will be compared to the results of E. Wang et al. and D. Fulton et al. in the same session. We thank R. Groebner and P. Snyder for providing experimental profiles and helpful discussions.
Study of no-man's land physics in the total-f gyrokinetic code XGC1
Ku, Seung Hoe; Chang, C. S.; Lang, J.
2014-10-01
While the ``transport shortfall'' in the ``no-man's land'' has been observed often in delta-f codes, it has not yet been observed in the global total-f gyrokinetic particle code XGC1. Since understanding the interaction between the edge and core transport appears to be a critical element in the prediction for ITER performance, understanding the no-man's land issue is an important physics research topic. Simulation results using the Holland case will be presented and the physics causing the shortfall phenomenon will be discussed. Nonlinear nonlocal interaction of turbulence, secondary flows, and transport appears to be the key.
International Nuclear Information System (INIS)
Parra, Felix I.; Catto, Peter J.
2009-01-01
A recent publication [F. I. Parra and P. J. Catto, Plasma Phys. Controlled Fusion 50, 065014 (2008)] warned against the use of the lower order gyrokinetic Poisson equation at long wavelengths because the long wavelength, radial electric field must remain undetermined to the order the equation is obtained. Another reference [W. W. Lee and R. A. Kolesnikov, Phys. Plasmas 16, 044506 (2009)] criticizes these results by arguing that the higher order terms neglected in the most common gyrokinetic Poisson equation are formally smaller than the terms that are retained. This argument is flawed and ignores that the lower order terms, although formally larger, must cancel without determining the long wavelength, radial electric field. The reason for this cancellation is discussed. In addition, the origin of a nonlinear term present in the gyrokinetic Poisson equation [F. I. Parra and P. J. Catto, Plasma Phys. Controlled Fusion 50, 065014 (2008)] is explained.
International Nuclear Information System (INIS)
Lee, W.W.; Kolesnikov, R.A.
2009-01-01
We show in this Response that the nonlinear Poisson's equation in our original paper derived from the drift kinetic approach can be verified by using the nonlinear gyrokinetic Poisson's equation of Dubin et al. (Phys. Fluids 26, 3524 (1983)). This nonlinear contribution in φ 2 is indeed of the order of k # perpendicular# 4 in the long wavelength limit and remains finite for zero ion temperature, in contrast to the nonlinear term by Parra and Catto (Plasma Phys. Control. Fusion 50, 065014 (2008)), which is of the order of k # perpendicular# 2 and diverges for T i → 0. For comparison, the leading term for the gyrokinetic Poisson's equation in this limit is of the order of k # perpendicular# 2 φ.
Directory of Open Access Journals (Sweden)
G. Wollenberg
2004-01-01
Full Text Available An interconnection system whose loads protected by a voltage suppressor and a low-pass filter against overvoltages caused by coupling pulse-shaped electromagnetic waves is analyzed. The external wave influencing the system is assumed as a plane wave with HPM form. The computation is provided by a full-wave PEEC model for the interconnection structure incorporated in the SPICE code. Thus, nonlinear elements of the protection circuit can be included in the calculation. The analysis shows intermodulation distortions and penetrations of low frequency interferences caused by intermodulations through the protection circuits. The example examined shows the necessity of using full-wave models for interconnections together with non-linear circuit solvers for simulation of noise immunity in systems protected by nonlinear devices.
Visualizing Gyrokinetic Turbulence in a Tokamak
Stantchev, George
2005-10-01
Multi-dimensional data output from gyrokinetic microturbulence codes are often difficult to visualize, in part due to the non-trivial geometry of the underlying grids, in part due to high irregularity of the relevant scalar field structures in turbulent regions. For instance, traditional isosurface extraction methods are likely to fail for the electrostatic potential field whose level sets may exhibit various geometric pathologies. To address these issues we develop an advanced interactive 3D gyrokinetic turbulence visualization framework which we apply in the study of microtearing instabilities calculated with GS2 in the MAST and NSTX geometries. In these simulations GS2 uses field-line-following coordinates such that the computational domain maps in physical space to a long, twisting flux tube with strong cross-sectional shear. Using statistical wavelet analysis we create a sparse multiple-scale volumetric representation of the relevant scalar fields, which we visualize via a variation of the so called splatting technique. To handle the problem of highly anisotropic flux tube configurations we adapt a geometry-driven surface illumination algorithm that places local light sources for effective feature-enhanced visualization.
De Conti, Alberto; Silveira, Fernando H.; Visacro, Silvério
2014-05-01
This paper investigates the influence of corona on currents and electromagnetic fields predicted by a return-stroke model that represents the lightning channel as a nonuniform transmission line with time-varying (nonlinear) resistance. The corona model used in this paper allows the calculation of corona currents as a function of the radial electric field in the vicinity of the channel. A parametric study is presented to investigate the influence of corona parameters, such as the breakdown electric field and the critical electric field for the stable propagation of streamers, on predicted currents and electromagnetic fields. The results show that, regardless of the assumed corona parameters, the incorporation of corona into the nonuniform and nonlinear transmission line model under investigation modifies the model predictions so that they consistently reproduce most of the typical features of experimentally observed lightning electromagnetic fields and return-stroke speed profiles. In particular, it is shown that the proposed model leads to close vertical electric fields presenting waveforms, amplitudes, and decay with distance in good agreement with dart leader electric field changes measured in triggered lightning experiments. A comparison with popular engineering return-stroke models further confirms the model's ability to predict consistent electric field waveforms in the close vicinity of the channel. Some differences observed in the field amplitudes calculated with the different models can be related to the fact that current distortion, while present in the proposed model, is ultimately neglected in the considered engineering return-stroke models.
Citrin, J.; Bourdelle, C.; Casson, F. J.; Angioni, C.; Bonanomi, N.; Camenen, Y.; Garbet, X.; Garzotti, L.; Görler, T.; Gürcan, O.; Koechl, F.; Imbeaux, F.; Linder, O.; van de Plassche, K.; Strand, P.; Szepesi, G.; Contributors, JET
2017-12-01
Quasilinear turbulent transport models are a successful tool for prediction of core tokamak plasma profiles in many regimes. Their success hinges on the reproduction of local nonlinear gyrokinetic fluxes. We focus on significant progress in the quasilinear gyrokinetic transport model QuaLiKiz (Bourdelle et al 2016 Plasma Phys. Control. Fusion 58 014036), which employs an approximated solution of the mode structures to significantly speed up computation time compared to full linear gyrokinetic solvers. Optimisation of the dispersion relation solution algorithm within integrated modelling applications leads to flux calculations × {10}6-7 faster than local nonlinear simulations. This allows tractable simulation of flux-driven dynamic profile evolution including all transport channels: ion and electron heat, main particles, impurities, and momentum. Furthermore, QuaLiKiz now includes the impact of rotation and temperature anisotropy induced poloidal asymmetry on heavy impurity transport, important for W-transport applications. Application within the JETTO integrated modelling code results in 1 s of JET plasma simulation within 10 h using 10 CPUs. Simultaneous predictions of core density, temperature, and toroidal rotation profiles for both JET hybrid and baseline experiments are presented, covering both ion and electron turbulence scales. The simulations are successfully compared to measured profiles, with agreement mostly in the 5%-25% range according to standard figures of merit. QuaLiKiz is now open source and available at www.qualikiz.com.
International Nuclear Information System (INIS)
Jolliet, S.
2009-02-01
The goal of thermonuclear fusion research is to provide power plants, that will be able to produce one gigawatt of electricity. Among the different ways to achieve fusion, the tokamak, based on magnetic confinement, is the most promising one. A gas is heated up to hundreds of millions of degrees and becomes a plasma, which is maintained - or confined - in a toroidal vessel by helical magnetic field lines. Then, deuterium and tritium are injected and fuse to create an α particle and an energetic neutron. In order to have a favorable power balance, the power produced by fusion reactions must exceed the power needed to heat the plasma and the power losses. This can be cast in a very simple expression which stipulates that the product of the density, the temperature and the energy confinement time must exceed some given value. Unfortunately, present-days tokamaks are not able to reach this condition, mostly due to plasma turbulence. The latter phenomenon enhances the heat losses and degrades the energy confinement time, which cannot be predicted by analytical theories such as the so-called neoclassical theory in which the heat losses are caused by Coulomb collisions. Therefore, numerical simulations are being developed to model plasma turbulence, mainly caused by the Ion and Electron Temperature-Gradient and the Trapped-Electron-Mode (TEM) instabilities. The plasma is described by a distribution function which evolves according to the Vlasov equation. The electromagnetic fields created by the particles are self-consistently obtained through Maxwell’s equations. The resulting Vlasov-Maxwell system is greatly simplified by using the gyrokinetic theory, which consists, through an appropriate ordering, of eliminating the fast gyromotion (compared to the typical frequency of instabilities). Nevertheless, it is still extremely difficult to solve this system numerically due to the large range of time and spatial scales to be resolved. In this thesis, the Vlasov
Verification of Gyrokinetic Particle of Turbulent Simulation of Device Size Scaling Transport
Institute of Scientific and Technical Information of China (English)
LIN Zhihong; S. ETHIER; T. S. HAHM; W. M. TANG
2012-01-01
Verification and historical perspective are presented on the gyrokinetic particle simulations that discovered the device size scaling of turbulent transport and indentified the geometry model as the source of the long-standing disagreement between gyrokinetic particle and continuum simulations.
Freethy, S. J.; Görler, T.; Creely, A. J.; Conway, G. D.; Denk, S. S.; Happel, T.; Koenen, C.; Hennequin, P.; White, A. E.; ASDEX Upgrade Team
2018-05-01
Measurements of turbulent electron temperature fluctuation amplitudes, δTe ⊥/Te , frequency spectra, and radial correlation lengths, Lr(Te ⊥) , have been performed at ASDEX Upgrade using a newly upgraded Correlation ECE diagnostic in the range of scales k⊥scale non-linear gyrokinetic turbulence simulations of the outer core (ρtor = 0.75) of a low density, electron heated L-mode plasma, performed using the gyrokinetic simulation code, GENE. The ion and electron temperature gradients were scanned within uncertainties. It is found that gyrokinetic simulations are able to match simultaneously the electron and ion heat flux at this radius within the experimental uncertainties. The simulations were performed based on a reference discharge for which δTe ⊥/Te measurements were available, and Lr(Te ⊥) and αnT were then predicted using synthetic diagnostics prior to measurements in a repeat discharge. While temperature fluctuation amplitudes are overestimated by >50% for all simulations within the sensitivity scans performed, good quantitative agreement is found for Lr(Te ⊥) and αnT. A validation metric is used to quantify the level of agreement of individual simulations with experimental measurements, and the best agreement is found close to the experimental gradient values.
Interaction between the neoclassical equilibrium and microturbulence in gyrokinetic simulations
Energy Technology Data Exchange (ETDEWEB)
Oberparleiter, Michael
2015-07-10
For the application of the nuclear fusion of hydrogen as a heat source for electricity generation understanding of the magnetic fuel confinement is crucial. Most of the cross-field transport in modern-day tokamaks is carried by turbulence driven by steep pressure gradients. Background neoclassical transport, however, provides a steady level of cross-field flux even in cases when turbulence becomes weak or suppressed. The goal of this work is to quantify how neoclassical (NC) effects and turbulence can influence each other. For this purpose the nonlinear gyrokinetic turbulence code GENE is employed. Firstly, its ability to self-consistently calculate the NC radial electric field is successfully benchmarked against the radial force balance equation and NC transport in the plasma region close to the center of a tokamak is studied. In the next step a model system where a long-wavelength external potential is imposed on ion temperature gradient-driven (ITG) turbulence is investigated. It is found that the self-generated shear flow pattern of the turbulence adapts to the imposed pattern and a small external shear is sufficient to notably reduce turbulent transport. Motivated by this global ITG simulations with fixed pressure gradient profiles are performed with and without inclusion of NC effects. Their comparison reveals that the NC field enhances turbulent transport by 20-30 % for a ratio of ion gyroradius and device radius larger than 1/300. An explanation is that the NC field aligns a region of low shear with the maximum of the gradient profile where the turbulent drive is strongest. Further investigation reveals that NC effects also change the dependence of the system on collisionality or safety factor. Finally, in physically more comprehensive simulations with fixed power input and a self-consistently evolving temperature profile, the additional NC transport channel is found to reduce the frequency and amplitude of intermittent turbulent transport bursts.
International Nuclear Information System (INIS)
Krommes, John A.
2007-01-01
The present state of the theory of fluctuations in gyrokinetic (GK) plasmas and especially its application to sampling noise in GK particle-in-cell (PIC) simulations is reviewed. Topics addressed include the Δf method, the fluctuation-dissipation theorem for both classical and GK many-body plasmas, the Klimontovich formalism, sampling noise in PIC simulations, statistical closure for partial differential equations, the theoretical foundations of spectral balance in the presence of arbitrary noise sources, and the derivation of Kadomtsev-type equations from the general formalism
Energy Technology Data Exchange (ETDEWEB)
John A. Krommes
2007-10-09
The present state of the theory of fluctuations in gyrokinetic GK plasmas and especially its application to sampling noise in GK particle-in-cell PIC simulations is reviewed. Topics addressed include the Δf method, the fluctuation-dissipation theorem for both classical and GK many-body plasmas, the Klimontovich formalism, sampling noise in PIC simulations, statistical closure for partial differential equations, the theoretical foundations of spectral balance in the presence of arbitrary noise sources, and the derivation of Kadomtsev-type equations from the general formalism.
Self-consistent gyrokinetic modeling of neoclassical and turbulent impurity transport
Estève, D.; Sarazin, Y.; Garbet, X.; Grandgirard, V.; Breton, S.; Donnel, P.; Asahi, Y.; Bourdelle, C.; Dif-Pradalier, G.; Ehrlacher, C.; Emeriau, C.; Ghendrih, Ph.; Gillot, C.; Latu, G.; Passeron, C.
2018-03-01
Trace impurity transport is studied with the flux-driven gyrokinetic GYSELA code (Grandgirard et al 2016 Comput. Phys. Commun. 207 35). A reduced and linearized multi-species collision operator has been recently implemented, so that both neoclassical and turbulent transport channels can be treated self-consistently on an equal footing. In the Pfirsch-Schlüter regime that is probably relevant for tungsten, the standard expression for the neoclassical impurity flux is shown to be recovered from gyrokinetics with the employed collision operator. Purely neoclassical simulations of deuterium plasma with trace impurities of helium, carbon and tungsten lead to impurity diffusion coefficients, inward pinch velocities due to density peaking, and thermo-diffusion terms which quantitatively agree with neoclassical predictions and NEO simulations (Belli et al 2012 Plasma Phys. Control. Fusion 54 015015). The thermal screening factor appears to be less than predicted analytically in the Pfirsch-Schlüter regime, which can be detrimental to fusion performance. Finally, self-consistent nonlinear simulations have revealed that the tungsten impurity flux is not the sum of turbulent and neoclassical fluxes computed separately, as is usually assumed. The synergy partly results from the turbulence-driven in-out poloidal asymmetry of tungsten density. This result suggests the need for self-consistent simulations of impurity transport, i.e. including both turbulence and neoclassical physics, in view of quantitative predictions for ITER.
Waltz, R. E.; Waelbroeck, F. L.
2012-03-01
Static external resonant magnetic perturbations (RMPs) have been added to the δf gyrokinetic code GYRO. This allows nonlinear gyrokinetic simulations of the nonambipolar radial current flow jr and the corresponding plasma torque (density) R[jrBθ/c], induced by islands that break the toroidal symmetry of a tokamak. This extends previous GYRO simulations for the transport of toroidal angular momentum (TAM) [1,2]. The focus is on full torus radial slice electrostatic simulations of induced q=m/n=6/3 islands with widths 5% of the minor radius. The island torque scales with the radial electric field Er the island width w, and the intensity I of the high-n micro-turbulence, as wErI^1/2. The net island torque is null at zero Er rather than at zero toroidal rotation. This means that there is a small co-directed magnetic acceleration to the small diamagnetic co-rotation corresponding to the zero Er which can be called the residual stress [2] from an externally induced island. Finite-beta GYRO simulations of a core radial slice demonstrate island unlocking and the RMP screening. 6pt[1] R.E. Waltz, et al., Phys. Plasmas 14, 122507 (2007). [2] R.E. Waltz, et al., Phys. Plasmas 18, 042504 (2011).
International Nuclear Information System (INIS)
Cottier, Pierre
2013-01-01
The magnetic confinement in tokamaks is for now the most advanced way towards energy production by nuclear fusion. Both theoretical and experimental studies showed that rotation generation can increase its performance by reducing the turbulent transport in tokamak plasmas. The rotation influence on the heat and particle fluxes is studied along with the angular momentum transport with the quasi-linear gyro-kinetic eigenvalue code QuaLiKiz. For this purpose, the QuaLiKiz code is modified in order to take the plasma rotation into account and compute the angular momentum flux. It is shown that QuaLiKiz framework is able to correctly predict the angular momentum flux including the E*B shear induced residual stress as well as the influence of rotation on the heat and particle fluxes. The major approximations of QuaLiKiz formalisms are reviewed, in particular the ballooning representation at its lowest order and the eigenfunctions calculated in the hydrodynamic limit. The construction of the quasi-linear fluxes is also reviewed in details and the quasi-linear angular momentum flux is derived. The different contributions to the turbulent momentum flux are studied and successfully compared both against non-linear gyro-kinetic simulations and experimental data. (author) [fr
Fluid and gyrokinetic modelling of particle transport in plasmas with hollow density profiles
International Nuclear Information System (INIS)
Tegnered, D; Oberparleiter, M; Nordman, H; Strand, P
2016-01-01
Hollow density profiles occur in connection with pellet fuelling and L to H transitions. A positive density gradient could potentially stabilize the turbulence or change the relation between convective and diffusive fluxes, thereby reducing the turbulent transport of particles towards the center, making the fuelling scheme inefficient. In the present work, the particle transport driven by ITG/TE mode turbulence in regions of hollow density profiles is studied by fluid as well as gyrokinetic simulations. The fluid model used, an extended version of the Weiland transport model, Extended Drift Wave Model (EDWM), incorporates an arbitrary number of ion species in a multi-fluid description, and an extended wavelength spectrum. The fluid model, which is fast and hence suitable for use in predictive simulations, is compared to gyrokinetic simulations using the code GENE. Typical tokamak parameters are used based on the Cyclone Base Case. Parameter scans in key plasma parameters like plasma β, R/L T , and magnetic shear are investigated. It is found that β in particular has a stabilizing effect in the negative R/L n region, both nonlinear GENE and EDWM show a decrease in inward flux for negative R/L n and a change of direction from inward to outward for positive R/L n . This might have serious consequences for pellet fuelling of high β plasmas. (paper)
Energy Technology Data Exchange (ETDEWEB)
Fahey, Mark R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Candy, Jeff [General Atomics, San Diego, CA (United States)
2013-11-07
This project initiated the development of TGYRO - a steady-state Gyrokinetic transport code (SSGKT) that integrates micro-scale GYRO turbulence simulations into a framework for practical multi-scale simulation of conventional tokamaks as well as future reactors. Using a lightweight master transport code, multiple independent (each massively parallel) gyrokinetic simulations are coordinated. The capability to evolve profiles using the TGLF model was also added to TGYRO and represents a more typical use-case for TGYRO. The goal of the project was to develop a steady-state Gyrokinetic transport code (SSGKT) that integrates micro-scale gyrokinetic turbulence simulations into a framework for practical multi-scale simulation of a burning plasma core ? the International Thermonuclear Experimental Reactor (ITER) in particular. This multi-scale simulation capability will be used to predict the performance (the fusion energy gain, Q) given the H-mode pedestal temperature and density. At present, projections of this type rely on transport models like GLF23, which are based on rather approximate fits to the results of linear and nonlinear simulations. Our goal is to make these performance projections with precise nonlinear gyrokinetic simulations. The method of approach is to use a lightweight master transport code to coordinate multiple independent (each massively parallel) gyrokinetic simulations using the GYRO code. This project targets the practical multi-scale simulation of a reactor core plasma in order to predict the core temperature and density profiles given the H-mode pedestal temperature and density. A master transport code will provide feedback to O(16) independent gyrokinetic simulations (each massively parallel). A successful feedback scheme offers a novel approach to predictive modeling of an important national and international problem. Success in this area of fusion simulations will allow US scientists to direct the research path of ITER over the next two
Gyrokinetic particle simulation of neoclassical transport
International Nuclear Information System (INIS)
Lin, Z.; Tang, W.M.; Lee, W.W.
1995-01-01
A time varying weighting (δf ) scheme for gyrokinetic particle simulation is applied to a steady-state, multispecies simulation of neoclassical transport. Accurate collision operators conserving momentum and energy are developed and implemented. Simulation results using these operators are found to agree very well with neoclassical theory. For example, it is dynamically demonstrated that like-particle collisions produce no particle flux and that the neoclassical fluxes are ambipolar for an ion--electron plasma. An important physics feature of the present scheme is the introduction of toroidal flow to the simulations. Simulation results are in agreement with the existing analytical neoclassical theory. The poloidal electric field associated with toroidal mass flow is found to enhance density gradient-driven electron particle flux and the bootstrap current while reducing temperature gradient-driven flux and current. Finally, neoclassical theory in steep gradient profile relevant to the edge regime is examined by taking into account finite banana width effects. In general, in the present work a valuable new capability for studying important aspects of neoclassical transport inaccessible by conventional analytical calculation processes is demonstrated. copyright 1995 American Institute of Physics
Visual interrogation of gyrokinetic particle simulations
International Nuclear Information System (INIS)
Jones, Chad; Ma, K-L; Sanderson, Allen; Myers, Lee Roy Jr
2007-01-01
Gyrokinetic particle simulations are critical to the study of anomalous energy transport associated with plasma microturbulence in magnetic confinement fusion experiments. The simulations are conducted on massively parallel computers and produce large quantities of particles, variables, and time steps, thus presenting a formidable challenge to data analysis tasks. We present two new visualization techniques for scientists to improve their understanding of the time-varying, multivariate particle data. One technique allows scientists to examine correlations in multivariate particle data with tightly coupled views of the data in both physical space and variable space, and to visually identify and track features of interest. The second technique, built into SCIRun, allows scientists to perform range-based queries over a series of time slices and visualize the resulting particles using glyphs. The ability to navigate the multiple dimensions of the particle data, as well as query individual or a collection of particles, enables scientists to not only validate their simulations but also discover new phenomena in their data
Conservation Laws for Gyrokinetic Equations for Large Perturbations and Flows
Dimits, Andris
2017-10-01
Gyrokinetic theory has proved to be very useful for the understanding of magnetized plasmas, both to simplify analytical treatments and as a basis for efficient numerical simulations. Gyrokinetic theories were previously developed in two extended orderings that are applicable to large fluctuations and flows as may arise in the tokamak edge and scrapeoff layer. In the present work, we cast the resulting equations in a field-theoretical variational form, and derive, up to second order in the respective orderings, the associated global and local energy and (linear and toroidal) momentum conservation relations that result from Noether's theorem. The consequences of these for the various possible choices of numerical discretization used in gyrokinetic simulations are considered. Prepared for US DOE by LLNL under Contract DE-AC52-07NA27344 and supported by the U.S. DOE, OFES.
The implementation of a toroidal limiter model into the gyrokinetic code ELMFIRE
Energy Technology Data Exchange (ETDEWEB)
Leerink, S.; Janhunen, S.J.; Kiviniemi, T.P.; Nora, M. [Euratom-Tekes Association, Helsinki University of Technology (Finland); Heikkinen, J.A. [Euratom-Tekes Association, VTT, P.O. Box 1000, FI-02044 VTT (Finland); Ogando, F. [Universidad Nacional de Educacion a Distancia, Madrid (Spain)
2008-03-15
The ELMFIRE full nonlinear gyrokinetic simulation code has been developed for calculations of plasma evolution and dynamics of turbulence in tokamak geometry. The code is applicable for calculations of strong perturbations in particle distribution function, rapid transients and steep gradients in plasma. Benchmarking against experimental reflectometry data from the FT2 tokamak is being discussed and in this paper a model for comparison and studying poloidal velocity is presented. To make the ELMFIRE code suitable for scrape-off layer simulations a simplified toroidal limiter model has been implemented. The model is be discussed and first results are presented. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
First-principle description of collisional gyrokinetic turbulence in tokamak plasmas
Energy Technology Data Exchange (ETDEWEB)
Dif-Pradalier, G
2008-10-15
This dissertation starts in chapter 1 with a comprehensive introduction to nuclear fusion, its basic physics, goals and means. It especially defines the concept of a fusion plasma and some of its essential physical properties. The following chapter 2 discusses some fundamental concepts of statistical physics. It introduces the kinetic and the fluid frameworks, compares them and highlights their respective strengths and limitations. The end of the chapter is dedicated to the fluid theory. It presents two new sets of closure relations for fluid equations which retain important pieces of physics, relevant in the weakly collisional tokamak regimes: collective resonances which lead to Landau damping and entropy production. Nonetheless, since the evolution of the turbulence is intrinsically nonlinear and deeply influenced by velocity space effects, a kinetic collisional description is most relevant. First focusing on the kinetic aspect, chapter 3 introduces the so-called gyrokinetic framework along with the numerical solver - the GYSELA code - which will be used throughout this dissertation. Very generically, code solving is an initial value problem. The impact on turbulent nonlinear evolution of out of equilibrium initial conditions is discussed while studying transient flows, self-organizing dynamics and memory effects due to initial conditions. This dissertation introduces an operational definition, now of routine use in the GYSELA code, for the initial state and concludes on the special importance of the accurate calculation of the radial electric field. The GYSELA framework is further extended in chapter 4 to describe Coulomb collisions. The implementation of a collision operator acting on the full distribution function is presented. Its successful confrontation to collisional theory (neoclassical theory) is also shown. GYSELA is now part of the few gyrokinetic codes which can self-consistently address the interplay between turbulence and collisions. While
First-principle description of collisional gyrokinetic turbulence in tokamak plasmas
International Nuclear Information System (INIS)
Dif-Pradalier, G.
2008-10-01
This dissertation starts in chapter 1 with a comprehensive introduction to nuclear fusion, its basic physics, goals and means. It especially defines the concept of a fusion plasma and some of its essential physical properties. The following chapter 2 discusses some fundamental concepts of statistical physics. It introduces the kinetic and the fluid frameworks, compares them and highlights their respective strengths and limitations. The end of the chapter is dedicated to the fluid theory. It presents two new sets of closure relations for fluid equations which retain important pieces of physics, relevant in the weakly collisional tokamak regimes: collective resonances which lead to Landau damping and entropy production. Nonetheless, since the evolution of the turbulence is intrinsically nonlinear and deeply influenced by velocity space effects, a kinetic collisional description is most relevant. First focusing on the kinetic aspect, chapter 3 introduces the so-called gyrokinetic framework along with the numerical solver - the GYSELA code - which will be used throughout this dissertation. Very generically, code solving is an initial value problem. The impact on turbulent nonlinear evolution of out of equilibrium initial conditions is discussed while studying transient flows, self-organizing dynamics and memory effects due to initial conditions. This dissertation introduces an operational definition, now of routine use in the GYSELA code, for the initial state and concludes on the special importance of the accurate calculation of the radial electric field. The GYSELA framework is further extended in chapter 4 to describe Coulomb collisions. The implementation of a collision operator acting on the full distribution function is presented. Its successful confrontation to collisional theory (neoclassical theory) is also shown. GYSELA is now part of the few gyrokinetic codes which can self-consistently address the interplay between turbulence and collisions. While
Metriplectic Gyrokinetics and Discretization Methods for the Landau Collision Integral
Hirvijoki, Eero; Burby, Joshua W.; Kraus, Michael
2017-10-01
We present two important results for the kinetic theory and numerical simulation of warm plasmas: 1) We provide a metriplectic formulation of collisional electrostatic gyrokinetics that is fully consistent with the First and Second Laws of Thermodynamics. 2) We provide a metriplectic temporal and velocity-space discretization for the particle phase-space Landau collision integral that satisfies the conservation of energy, momentum, and particle densities to machine precision, as well as guarantees the existence of numerical H-theorem. The properties are demonstrated algebraically. These two result have important implications: 1) Numerical methods addressing the Vlasov-Maxwell-Landau system of equations, or its reduced gyrokinetic versions, should start from a metriplectic formulation to preserve the fundamental physical principles also at the discrete level. 2) The plasma physics community should search for a metriplectic reduction theory that would serve a similar purpose as the existing Lagrangian and Hamiltonian reduction theories do in gyrokinetics. The discovery of metriplectic formulation of collisional electrostatic gyrokinetics is strong evidence in favor of such theory and, if uncovered, the theory would be invaluable in constructing reduced plasma models. Supported by U.S. DOE Contract Nos. DE-AC02-09-CH11466 (EH) and DE-AC05-06OR23100 (JWB) and by European Union's Horizon 2020 research and innovation Grant No. 708124 (MK).
Turbulent transport of toroidal angular momentum in low flow gyrokinetics
International Nuclear Information System (INIS)
Parra, Felix I; Catto, Peter J
2010-01-01
We derive a self-consistent equation for the turbulent transport of toroidal angular momentum in tokamaks in the low flow ordering that only requires solving gyrokinetic Fokker-Planck and quasineutrality equations correct to second order in an expansion on the gyroradius over scale length. We also show that according to our orderings the long wavelength toroidal rotation and the long wavelength radial electric field satisfy the neoclassical relation that gives the toroidal rotation as a function of the radial electric field and the radial gradients of pressure and temperature. Thus, the radial electric field can be solved for once the toroidal rotation is calculated from the transport of toroidal angular momentum. Unfortunately, even though this methodology only requires a gyrokinetic model correct to second order in gyroradius over scale length, current gyrokinetic simulations are only valid to first order. To overcome this difficulty, we exploit the smallish ratio B p /B, where B is the total magnetic field and B p is its poloidal component. When B p /B is small, the usual first order gyrokinetic equation provides solutions that are accurate enough to employ for our expression for the transport of toroidal angular momentum. We show that current δf and full f simulations only need small corrections to achieve this accuracy. Full f simulations, however, are still unable to determine the long wavelength, radial electric field from the quasineutrality equation.
Gyrokinetic global analysis of ion temperature gradient driven mode in reversed shear tokamaks
International Nuclear Information System (INIS)
Idomura, Y.; Tokuda, S.; Kishimoto, Y.
2003-01-01
A new toroidal gyrokinetic particle code has been developed to study the ion temperature gradient driven (ITG) turbulence in reactor relevant tokamak parameters. We use a new method based on a canonical Maxwellian distribution F CM (P φ , ε, μ), which is defined by three constants of motion in the axisymmetric toroidal system, the canonical angular momentum P φ , the energy ε, and the magnetic moment μ. A quasi-ballooning representation enables linear and nonlinear high-m,n global calculations with a good numerical convergence. Conservation properties are improved by using the optimized loading method. From comprehensive linear global analyses over a wide range of an unstable toroidal mode number spectrum (n=0∼100) in large tokamak parameters (a/ρ ti =320∼460), properties of the ITG modes in reversed shear tokamaks are discussed. In the nonlinear simulation, it is found that a new method based on F CM can simulate a zonal flow damping correctly, and spurious zonal flow oscillations, which are observed in a conventional method based on a local Maxwellian distribution F LM (ψ, ε, μ), do not appear in the nonlinear regime. (author)
Nonlinear saturation of the slab ITG instability and zonal flow generation with fully kinetic ions
Miecnikowski, Matthew T.; Sturdevant, Benjamin J.; Chen, Yang; Parker, Scott E.
2018-05-01
Fully kinetic turbulence models are of interest for their potential to validate or replace gyrokinetic models in plasma regimes where the gyrokinetic expansion parameters are marginal. Here, we demonstrate fully kinetic ion capability by simulating the growth and nonlinear saturation of the ion-temperature-gradient instability in shearless slab geometry assuming adiabatic electrons and including zonal flow dynamics. The ion trajectories are integrated using the Lorentz force, and the cyclotron motion is fully resolved. Linear growth and nonlinear saturation characteristics show excellent agreement with analogous gyrokinetic simulations across a wide range of parameters. The fully kinetic simulation accurately reproduces the nonlinearly generated zonal flow. This work demonstrates nonlinear capability, resolution of weak gradient drive, and zonal flow physics, which are critical aspects of modeling plasma turbulence with full ion dynamics.
International Nuclear Information System (INIS)
Ungan, F.; Yesilgul, U.; Kasapoglu, E.; Sari, H.; Sökmen, I.
2012-01-01
In this present work, we have investigated theoretically the effects of applied electric and magnetic fields on the linear and nonlinear optical properties in a GaAs/Al x Ga 1−x As inverse parabolic quantum well for different Al concentrations at the well center. The Al concentration at the barriers was always x max =0.3. The energy levels and wave functions are calculated within the effective mass approximation and the envelope function approach. The analytical expressions of optical properties are obtained by using the compact density-matrix approach. The linear, third-order nonlinear and total absorption and refractive index changes depending on the Al concentration at the well center are investigated as a function of the incident photon energy for the different values of the applied electric and magnetic fields. The results show that the applied electric and magnetic fields have a great effect on these optical quantities. - Highlights: ► The x c concentration has a great effect on the optical characteristics of these structures. ► The EM fields have a great effect on the optical properties of these structures. ► The total absorption coefficients increased as the electric and magnetic field increases. ► The RICs reduced as the electric and magnetic field increases.
Biancalani, A.; Bottino, A.; Ehrlacher, C.; Grandgirard, V.; Merlo, G.; Novikau, I.; Qiu, Z.; Sonnendrücker, E.; Garbet, X.; Görler, T.; Leerink, S.; Palermo, F.; Zarzoso, D.
2017-06-01
The linear properties of the geodesic acoustic modes (GAMs) in tokamaks are investigated by means of the comparison of analytical theory and gyrokinetic numerical simulations. The dependence on the value of the safety factor, finite-orbit-width of the ions in relation to the radial mode width, magnetic-flux-surface shaping, and electron/ion mass ratio are considered. Nonuniformities in the plasma profiles (such as density, temperature, and safety factor), electro-magnetic effects, collisions, and the presence of minority species are neglected. Also, only linear simulations are considered, focusing on the local dynamics. We use three different gyrokinetic codes: the Lagrangian (particle-in-cell) code ORB5, the Eulerian code GENE, and semi-Lagrangian code GYSELA. One of the main aims of this paper is to provide a detailed comparison of the numerical results and analytical theory, in the regimes where this is possible. This helps understanding better the behavior of the linear GAM dynamics in these different regimes, the behavior of the codes, which is crucial in the view of a future work where more physics is present, and the regimes of validity of each specific analytical dispersion relation.
Electromagnetic drift modes in an inhomogeneous electron gas
DEFF Research Database (Denmark)
Shukla, P. K.; Pecseli, H. L.; Juul Rasmussen, Jens
1986-01-01
A pair of nonlinear equations is derived which describes the dynamics of the electromagnetic drift oscillations in a nonuniform magnetized electron gas. It is shown that the nonlinear electromagnetic drift modes can propagate in the form of dipole vortices...
Gyrokinetic theory for particle and energy transport in fusion plasmas
Falessi, Matteo Valerio; Zonca, Fulvio
2018-03-01
A set of equations is derived describing the macroscopic transport of particles and energy in a thermonuclear plasma on the energy confinement time. The equations thus derived allow studying collisional and turbulent transport self-consistently, retaining the effect of magnetic field geometry without postulating any scale separation between the reference state and fluctuations. Previously, assuming scale separation, transport equations have been derived from kinetic equations by means of multiple-scale perturbation analysis and spatio-temporal averaging. In this work, the evolution equations for the moments of the distribution function are obtained following the standard approach; meanwhile, gyrokinetic theory has been used to explicitly express the fluctuation induced fluxes. In this way, equations for the transport of particles and energy up to the transport time scale can be derived using standard first order gyrokinetics.
A Numerical Instability in an ADI Algorithm for Gyrokinetics
International Nuclear Information System (INIS)
Belli, E.A.; Hammett, G.W.
2004-01-01
We explore the implementation of an Alternating Direction Implicit (ADI) algorithm for a gyrokinetic plasma problem and its resulting numerical stability properties. This algorithm, which uses a standard ADI scheme to divide the field solve from the particle distribution function advance, has previously been found to work well for certain plasma kinetic problems involving one spatial and two velocity dimensions, including collisions and an electric field. However, for the gyrokinetic problem we find a severe stability restriction on the time step. Furthermore, we find that this numerical instability limitation also affects some other algorithms, such as a partially implicit Adams-Bashforth algorithm, where the parallel motion operator v parallel ∂/∂z is treated implicitly and the field terms are treated with an Adams-Bashforth explicit scheme. Fully explicit algorithms applied to all terms can be better at long wavelengths than these ADI or partially implicit algorithms
International Nuclear Information System (INIS)
Ernst, D.R.; Basse, N.; Bonoli, P.T.; Catto, P.J.; Fiore, C.L.; Greenwald, M.; Hubbard, A.E.; Marmar, E.S.; Porkolab, M.; Rice, J.E.; Zeller, K.; Zhurovich, K.; Dorland, W.
2005-01-01
Internal particle and thermal energy transport barriers are produced in Alcator C-Mod with off-axis ICRF heating, with core densities exceeding 10 21 m -3 , without core fueling, and with little change in the temperature profile. Applying on-axis ICRF heating controls the core density gradient and rate of rise. The present study employs linear and nonlinear gyrokinetic simulations of trapped electron mode (TEM) turbulence to explore mechanisms for ITB formation and control in Alcator C-Mod ITB experiments. Anomalous pinches are found to be negligible in our simulations; further, the collisional Ware pinch is sufficient to account for the slow density rise, lasting many energy confinement times. The simulations have revealed new nonlinear physics of TEM turbulence. The critical density gradient for onset of TEM turbulent transport is nonlinearly up-shifted by zonal flows. As the density profile peaks, during ITB formation, this nonlinear critical gradient is eventually exceeded, and the turbulent particle diffusivity from GS2 gyrokinetic simulations matches the particle diffusivity from transport analysis, within experimental errors. A stable equilibrium is then established when the TEM turbulent diffusion balances the Ware pinch in the ITB. This equilibrium is sensitive to temperature through gyroBohm scaling of the TEM turbulent transport, and the collisionality dependence of the neoclassical pinch, providing for control of the density rate of rise with on-axis RF heating. With no core particle fueling, and ∼1 mm between density spatial channels, the C-Mod experiments provide a nearly ideal test bed for particle transport studies. The pure TEM is the only unstable drift mode in the ITB, producing particle transport driven by the density gradient. (author)
Hachay, O. A.; Khachay, O. Y.; Klimko, V. K.; Shipeev, O. V.
2012-04-01
Geological medium is an open dynamical system, which is influenced on different scales by natural and man-made impacts, which change the medium state and lead as a result to a complicated many ranked hierarchic evolution. That is the subject of geo synergetics. Paradigm of physical mesomechanics, which was advanced by academician Panin V.E. and his scientific school, which includes the synergetic approach is a constructive method for research and changing the state of heterogenic materials [1]. That result had been obtained on specimens of different materials. In our results of research of no stationary geological medium in a frame of natural experiments in real rock massifs, which are under high man-made influence it was shown, that the state dynamics can be revealed with use synergetics in hierarchic medium. Active and passive geophysical monitoring plays a very important role for research of the state of dynamical geological systems. It can be achieved by use electromagnetic and seismic fields. Our experience of that research showed the changing of the system state reveals on the space scales and times in the parameters, which are linked with the peculiarities of the medium of the second or higher ranks [2-5]. Results of seismological and electromagnetic information showed the mutual additional information on different space-time levels of rock massive state, which are energetic influenced by explosions, used in mining technology. It is revealed a change of nonlinearity degree in time of the massive state by active influence on it. The description of massive movement in a frame of linear dynamical system does not satisfy the practical situation. The received results are of great significance because for the first time we could find the coincidences with the mathematical theory of open systems and experimental natural results with very complicated structure. On that base we developed a new processing method for the seismological information which can be used in
Gyrokinetic simulations of neoclassical transport using a minimal collision operator
International Nuclear Information System (INIS)
Dif-Pradalier, G.; Grandgirard, V.; Sarazin, Y.; Garbet, X.; Ghendrih, Ph.; Angelino, P.
2008-01-01
Conventional neoclassical predictions are successfully recovered within a gyrokinetic framework using a minimal Fokker-Planck collision operator. This operator is shown to accurately describe some essential features of neoclassical theory, namely the neoclassical transport, the poloidal rotation and the linear damping of axisymmetric flows while interestingly preserving a high numerical efficiency. Its form makes it especially adapted to Eulerian or Semi-Lagrangian schemes.
COMPREHENSIVE GYROKINETIC SIMULATION OF TOKAMAK TURBULENCE AT FINITE RELATIVE GYRORADIUS
International Nuclear Information System (INIS)
WALTZ, R.E.; CANDY, J.; ROSENBLUTH, M.N.
2002-01-01
OAK B202 COMPREHENSIVE GYROKINETIC SIMULATION OF TOKAMAK TURBULENCE AT FINITE RELATIVE GYRORADIUS. A continuum global gyrokinetic code GYRO has been developed to comprehensively simulate turbulent transport in actual experimental profiles and allow direct quantitative comparisons to the experimental transport flows. GYRO not only treats the now standard ion temperature gradient (ITG) mode turbulence, but also treats trapped and passing electrons with collisions and finite beta, and all in real tokamak geometry. Most importantly the code operates at finite relative gyroradius (ρ*) so as to treat the profile shear stabilization effects which break gyroBohm scaling. The code operates in a cyclic flux tube limit which allows only gyroBohm scaling and a noncyclic radial annulus with physical profile variation. The later requires an adaptive source to maintain equilibrium profiles. Simple ITG simulations demonstrate the broken gyroBohm scaling depends on the actual rotational velocity shear rates competing with mode growth rates, direct comprehensive simulations of the DIII-D ρ*-scaled L-mode experiments are presented as a quantitative test of gyrokinetics and the paradigm
On push-forward representations in the standard gyrokinetic model
International Nuclear Information System (INIS)
Miyato, N.; Yagi, M.; Scott, B. D.
2015-01-01
Two representations of fluid moments in terms of a gyro-center distribution function and gyro-center coordinates, which are called push-forward representations, are compared in the standard electrostatic gyrokinetic model. In the representation conventionally used to derive the gyrokinetic Poisson equation, the pull-back transformation of the gyro-center distribution function contains effects of the gyro-center transformation and therefore electrostatic potential fluctuations, which is described by the Poisson brackets between the distribution function and scalar functions generating the gyro-center transformation. Usually, only the lowest order solution of the generating function at first order is considered to explicitly derive the gyrokinetic Poisson equation. This is true in explicitly deriving representations of scalar fluid moments with polarization terms. One also recovers the particle diamagnetic flux at this order because it is associated with the guiding-center transformation. However, higher-order solutions are needed to derive finite Larmor radius terms of particle flux including the polarization drift flux from the conventional representation. On the other hand, the lowest order solution is sufficient for the other representation, in which the gyro-center transformation part is combined with the guiding-center one and the pull-back transformation of the distribution function does not appear
On push-forward representations in the standard gyrokinetic model
Energy Technology Data Exchange (ETDEWEB)
Miyato, N., E-mail: miyato.naoaki@jaea.go.jp; Yagi, M. [Japan Atomic Energy Agency, 2-116 Omotedate, Obuchi, Rokkasho, Aomori 039-3212 (Japan); Scott, B. D. [Max-Planck-Institut für Plasmaphysik, D-85748 Garching (Germany)
2015-01-15
Two representations of fluid moments in terms of a gyro-center distribution function and gyro-center coordinates, which are called push-forward representations, are compared in the standard electrostatic gyrokinetic model. In the representation conventionally used to derive the gyrokinetic Poisson equation, the pull-back transformation of the gyro-center distribution function contains effects of the gyro-center transformation and therefore electrostatic potential fluctuations, which is described by the Poisson brackets between the distribution function and scalar functions generating the gyro-center transformation. Usually, only the lowest order solution of the generating function at first order is considered to explicitly derive the gyrokinetic Poisson equation. This is true in explicitly deriving representations of scalar fluid moments with polarization terms. One also recovers the particle diamagnetic flux at this order because it is associated with the guiding-center transformation. However, higher-order solutions are needed to derive finite Larmor radius terms of particle flux including the polarization drift flux from the conventional representation. On the other hand, the lowest order solution is sufficient for the other representation, in which the gyro-center transformation part is combined with the guiding-center one and the pull-back transformation of the distribution function does not appear.
Verification of gyrokinetic microstability codes with an LHD configuration
Energy Technology Data Exchange (ETDEWEB)
Mikkelsen, D. R. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Nunami, M. [National Inst. for Fusion Science (Japan); Watanabe, T. -H. [Nagoya Univ. (Japan); Sugama, H. [National Inst. for Fusion Science (Japan); Tanaka, K. [National Inst. for Fusion Science (Japan)
2014-11-01
We extend previous benchmarks of the GS2 and GKV-X codes to verify their algorithms for solving the gyrokinetic Vlasov-Poisson equations for plasma microturbulence. Code benchmarks are the most complete way of verifying the correctness of implementations for the solution of mathematical models for complex physical processes such as those studied here. The linear stability calculations reported here are based on the plasma conditions of an ion-ITB plasma in the LHD configuration. The plasma parameters and the magnetic geometry differ from previous benchmarks involving these codes. We find excellent agreement between the independently written pre-processors that calculate the geometrical coefficients used in the gyrokinetic equations. Grid convergence tests are used to establish the resolution and domain size needed to obtain converged linear stability results. The agreement of the frequencies, growth rates and eigenfunctions in the benchmarks reported here provides additional verification that the algorithms used by the GS2 and GKV-X codes are correctly finding the linear eigenvalues and eigenfunctions of the gyrokinetic Vlasov-Poisson equations.
Electromagnetic Gowdy universe
International Nuclear Information System (INIS)
Charach, C.
1979-01-01
Following Gowdy and Berger we construct an inhomogeneous closed electromagnetic universe with three-torus topology. This model is obtained as a result of the homogeneity breaking in the electromagnetic Bianchi type-I universe and contains interacting gravitational and electromagnetic waves. This cosmological solution provides an exactly solvable model for the study of the nonlinear fully relativistic regime of coupled electromagnetic and gravitational fields in the early universe. The asymptotic behavior is considered (i) in the vicinity of the initial singularity and (ii) in the high-frequency limit. It is shown that the effects of coupling between electromagnetic and gravitational waves cause an evolution which is significantly different from that of the vacuum model. The influence of the primordial homogeneous electromagnetic field on the dynamics of the model is also discussed
Seo, Janghoon; Chang, C. S.; Ku, S.; Kwon, J. M.; Yoon, E. S.
2013-10-01
The Full-f gyrokinetic code XGC1 is used to study the details of toroidal momentum generation in H-mode plasma. Diverted DIII-D geometry is used, with Monte Carlo neutral particles that are recycled at the limiter wall. Nonlinear Coulomb collisions conserve particle, momentum, and energy. Gyrokinetic ions and adiabatic electrons are used in the present simulation to include the effects from ion gyrokinetic turbulence and neoclassical physics, under self-consistent radial electric field generation. Ion orbit loss physics is automatically included. Simulations show a strong co-Ip flow in the H-mode layer at outside midplane, similarly to the experimental observation from DIII-D and ASDEX-U. The co-Ip flow in the edge propagates inward into core. It is found that the strong co-Ip flow generation is mostly from neoclassical physics. On the other hand, the inward momentum transport is from turbulence physics, consistently with the theory of residual stress from symmetry breaking. Therefore, interaction between the neoclassical and turbulence physics is a key factor in the spontaneous momentum generation.
Experimental and gyrokinetic investigation of core impurity transport in Alcator C-mod
Howard, N.; Greenwald, M.; Podpaly, Y.; Reinke, M. L.; Rice, J. E.; White, A. E.; Mikkelsen, D. R.; Puetterich, T.
2010-11-01
A new multiple pulse laser blow-off system coupled with an upgraded high resolution x-ray spectrometer with spatial resolution allow for the most detailed studies of impurity transport on Alcator C-mod to date. Trace impurity injections created by the laser blow-off technique were introduced into plasmas with a wide range of parameters and time evolving profiles of He-like calcium were measured. The unique measurement of a single charge state profile and line integrated emission measurements from spectroscopic diagnostics were compared with the simulated emission from the impurity transport code STRAHL. A nonlinear least squares fitting routine was coupled with STRAHL, allowing for core impurity transport coefficients with errors to be determined. With this method, experimental data from trace calcium injections were analyzed and radially dependent, core values (< r/a ˜.6) of the diffusive and convective components of the impurity flux were obtained. The STRAHL results are compared with linear and global, nonlinear simulations from the gyrokinetic code GYRO. Results of this comparison and an investigation of the underlying physics associated with turbulent impurity transport will be presented.
International Nuclear Information System (INIS)
Heikkinen, J.A.; Henriksson, S.; Janhunen, S.; Kiviniemi, T.P.; Ogando, F.
2006-01-01
A full f nonlinear 5D gyrokinetic electrostatic particle-in-cell code ELMFIRE using an implicit direct solution method for ion polarization drift and electron parallel velocity response to electric field and its validation are described. The developed code is applied for transport analysis in a tokamak plasma at steep pressure gradient. The role of turbulence and neoclassical equilibrium in determining the flux surface averaged radial electric field component are investigated, as well as the role of the latter in affecting the saturation level of the turbulence. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Astrophysical gyrokinetics: turbulence in pressure-anisotropic plasmas at ion scales and beyond
Kunz, M. W.; Abel, I. G.; Klein, K. G.
2018-04-01
We present a theoretical framework for describing electromagnetic kinetic turbulence in a multi-species, magnetized, pressure-anisotropic plasma. The turbulent fluctuations are assumed to be small compared to the mean field, to be spatially anisotropic with respect to it and to have frequencies small compared to the ion cyclotron frequency. At scales above the ion-Larmor radius, the theory reduces to the pressure-anisotropic generalization of kinetic reduced magnetohydrodynamics (KRMHD) formulated by Kunz et al. (J. Plasma Phys., vol. 81, 2015, 325810501). At scales at and below the ion-Larmor radius, three main objectives are achieved. First, we analyse the linear response of the pressure-anisotropic gyrokinetic system, and show it to be a generalization of previously explored limits. The effects of pressure anisotropy on the stability and collisionless damping of Alfvénic and compressive fluctuations are highlighted, with attention paid to the spectral location and width of the frequency jump that occurs as Alfvén waves transition into kinetic Alfvén waves. Secondly, we derive and discuss a very general gyrokinetic free-energy conservation law, which captures both the KRMHD free-energy conservation at long wavelengths and dual cascades of kinetic Alfvén waves and ion entropy at sub-ion-Larmor scales. We show that non-Maxwellian features in the distribution function change the amount of phase mixing and the efficiency of magnetic stresses, and thus influence the partitioning of free energy amongst the cascade channels. Thirdly, a simple model is used to show that pressure anisotropy, even within the bounds imposed on it by firehose and mirror instabilities, can cause order-of-magnitude variations in the ion-to-electron heating ratio due to the dissipation of Alfvénic turbulence. Our theory provides a foundation for determining how pressure anisotropy affects turbulent fluctuation spectra, the differential heating of particle species and the ratio of parallel
Optimized Loading for Particle-in-cell Gyrokinetic Simulations
International Nuclear Information System (INIS)
Lewandowski, J.L.V.
2004-01-01
The problem of particle loading in particle-in-cell gyrokinetic simulations is addressed using a quadratic optimization algorithm. Optimized loading in configuration space dramatically reduces the short wavelength modes in the electrostatic potential that are partly responsible for the non-conservation of total energy; further, the long wavelength modes are resolved with good accuracy. As a result, the conservation of energy for the optimized loading is much better that the conservation of energy for the random loading. The method is valid for any geometry and can be coupled to optimization algorithms in velocity space
A study of self organized criticality in ion temperature gradient mode driven gyrokinetic turbulence
Mavridis, M.; Isliker, H.; Vlahos, L.; Görler, T.; Jenko, F.; Told, D.
2014-10-01
An investigation on the characteristics of self organized criticality (Soc) in ITG mode driven turbulence is made, with the use of various statistical tools (histograms, power spectra, Hurst exponents estimated with the rescaled range analysis, and the structure function method). For this purpose, local non-linear gyrokinetic simulations of the cyclone base case scenario are performed with the GENE software package. Although most authors concentrate on global simulations, which seem to be a better choice for such an investigation, we use local simulations in an attempt to study the locally underlying mechanisms of Soc. We also study the structural properties of radially extended structures, with several tools (fractal dimension estimate, cluster analysis, and two dimensional autocorrelation function), in order to explore whether they can be characterized as avalanches. We find that, for large enough driving temperature gradients, the local simulations exhibit most of the features of Soc, with the exception of the probability distribution of observables, which show a tail, yet they are not of power-law form. The radial structures have the same radial extent at all temperature gradients examined; radial motion (transport) though appears only at large temperature gradients, in which case the radial structures can be interpreted as avalanches.
A study of self organized criticality in ion temperature gradient mode driven gyrokinetic turbulence
International Nuclear Information System (INIS)
Mavridis, M.; Isliker, H.; Vlahos, L.; Görler, T.; Jenko, F.; Told, D.
2014-01-01
An investigation on the characteristics of self organized criticality (Soc) in ITG mode driven turbulence is made, with the use of various statistical tools (histograms, power spectra, Hurst exponents estimated with the rescaled range analysis, and the structure function method). For this purpose, local non-linear gyrokinetic simulations of the cyclone base case scenario are performed with the GENE software package. Although most authors concentrate on global simulations, which seem to be a better choice for such an investigation, we use local simulations in an attempt to study the locally underlying mechanisms of Soc. We also study the structural properties of radially extended structures, with several tools (fractal dimension estimate, cluster analysis, and two dimensional autocorrelation function), in order to explore whether they can be characterized as avalanches. We find that, for large enough driving temperature gradients, the local simulations exhibit most of the features of Soc, with the exception of the probability distribution of observables, which show a tail, yet they are not of power-law form. The radial structures have the same radial extent at all temperature gradients examined; radial motion (transport) though appears only at large temperature gradients, in which case the radial structures can be interpreted as avalanches
A study of self organized criticality in ion temperature gradient mode driven gyrokinetic turbulence
Energy Technology Data Exchange (ETDEWEB)
Mavridis, M.; Isliker, H.; Vlahos, L. [Section of Astrophysics, Astronomy and Mechanics, Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Görler, T.; Jenko, F.; Told, D. [Max Planck Institute for Plasma Physics, Boltzmannstr. 2, 85748 Garching (Germany)
2014-10-15
An investigation on the characteristics of self organized criticality (Soc) in ITG mode driven turbulence is made, with the use of various statistical tools (histograms, power spectra, Hurst exponents estimated with the rescaled range analysis, and the structure function method). For this purpose, local non-linear gyrokinetic simulations of the cyclone base case scenario are performed with the GENE software package. Although most authors concentrate on global simulations, which seem to be a better choice for such an investigation, we use local simulations in an attempt to study the locally underlying mechanisms of Soc. We also study the structural properties of radially extended structures, with several tools (fractal dimension estimate, cluster analysis, and two dimensional autocorrelation function), in order to explore whether they can be characterized as avalanches. We find that, for large enough driving temperature gradients, the local simulations exhibit most of the features of Soc, with the exception of the probability distribution of observables, which show a tail, yet they are not of power-law form. The radial structures have the same radial extent at all temperature gradients examined; radial motion (transport) though appears only at large temperature gradients, in which case the radial structures can be interpreted as avalanches.
Gyrokinetic Calculations of Microinstabilities and Transport During RF H-Modes on Alcator C-Mod
International Nuclear Information System (INIS)
Redi, M.H.; Fiore, C.; Bonoli, P.; Bourdelle, C.; Budny, R.; Dorland, W.D.; Ernst, D.; Hammett, G.; Mikkelsen, D.; Rice, J.; Wukitch, S.
2002-01-01
Physics understanding for the experimental improvement of particle and energy confinement is being advanced through massively parallel calculations of microturbulence for simulated plasma conditions. The ultimate goal, an experimentally validated, global, non-local, fully nonlinear calculation of plasma microturbulence is still not within reach, but extraordinary progress has been achieved in understanding microturbulence, driving forces and the plasma response in recent years. In this paper we discuss gyrokinetic simulations of plasma turbulence being carried out to examine a reproducible, H-mode, RF heated experiment on the Alcator CMOD tokamak3, which exhibits an internal transport barrier (ITB). This off axis RF case represents the early phase of a very interesting dual frequency RF experiment, which shows density control with central RF heating later in the discharge. The ITB exhibits steep, spontaneous density peaking: a reduction in particle transport occurring without a central particle source. Since the central temperature is maintained while the central density is increasing, this also suggests a thermal transport barrier exists. TRANSP analysis shows that ceff drops inside the ITB. Sawtooth heat pulse analysis also shows a localized thermal transport barrier. For this ICRF EDA H-mode, the minority resonance is at r/a * 0.5 on the high field side. There is a normal shear profile, with q monotonic
International Nuclear Information System (INIS)
Narita, Emi; Fukuda, Takeshi; Honda, Mitsuru; Hayashi, Nobuhiko; Urano, Hajime; Ide, Shunsuke
2015-01-01
Tokamak plasmas with an internal transport barrier (ITB) are capable of maintaining improved confinement performance. The ITBs formed in plasmas with the weak magnetic shear and the weak radial electric field shear are often observed to be modest. In these ITB plasmas, it has been found that the electron temperature ITB is steeper when toroidal rotation is in a co-direction with respect to the plasma current than when toroidal rotation is in a counter-direction. To clarify the relationship between the direction of toroidal rotation and heat transport in the ITB region, we examine dominant instabilities using the flux-tube gyrokinetic code GS2. The linear calculations show a difference in the real frequencies; the counter-rotation case has a more trapped electron mode than the co-rotation case. In addition, the nonlinear calculations show that with this difference, the ratio of the electron heat diffusivity χ_e to the ion's χ_i is higher for the counter-rotation case than for the co-rotation case. The difference in χ_e /χ_i agrees with the experiment. We also find that the effect of the difference in the flow shear between the two cases due to the toroidal rotation direction on the linear growth rate is not significant. (author)
Global gyrokinetic simulations of the H-mode tokamak edge pedestal
Energy Technology Data Exchange (ETDEWEB)
Wan, Weigang; Parker, Scott E.; Chen, Yang [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States); Groebner, Richard J. [General Atomics, Post Office Box 85068, San Diego, California 92186 (United States); Yan, Zheng [University of Wisconsin-Madison, Madison, Wisconsin 53706 (United States); Pankin, Alexei Y.; Kruger, Scott E. [Tech-X Corporation, 5621 Arapahoe Ave., Boulder, Colorado 80305 (United States)
2013-05-15
Global gyrokinetic simulations of DIII-D H-mode edge pedestal show two types of instabilities may exist approaching the onset of edge localized modes: an intermediate-n, high frequency mode which we identify as the “kinetic peeling ballooning mode (KPBM),” and a high-n, low frequency mode. Our previous study [W. Wan et al., Phys. Rev. Lett. 109, 185004 (2012)] has shown that when the safety factor profile is flattened around the steep pressure gradient region, the high-n mode is clearly kinetic ballooning mode and becomes the dominant instability. Otherwise, the KPBM dominates. Here, the properties of the two instabilities are studied by varying the density and temperature profiles. It is found that the KPBM is destabilized by density and ion temperature gradient, and the high-n mode is mostly destabilized by electron temperature gradient. Nonlinear simulations with the KPBM saturate at high levels. The equilibrium radial electric field (E{sub r}) reduces the transport. The effect of the parallel equilibrium current is found to be weak.
Comprehensive gyrokinetic simulation of tokamak turbulence at finite relative gyroradius
International Nuclear Information System (INIS)
Waltz, R.E.; Candy, J.; Rosenbluth, M.N.
2003-01-01
A continuum global gyrokinetic code GYRO has been developed to comprehensively simulate turbulent transport in actual experimental profiles and allow direct quantitative comparisons to the experimental transport flows. GYRO not only treats the now standard ion temperature gradient (ITG) mode turbulence, but also treats trapped and passing electrons with collisions and finite beta, and all in real tokamak geometry. Most importantly the code operates at finite relative gyroradius (ρ*) so as to treat the profile shear stabilization effects which break gyro Bohm scaling. The code operates in a cyclic flux tube limit which allows only gyro Bohm scaling and a noncylic radial annulus with physical profile variation. The later requires an adaptive source to maintain equilibrium profiles. Simple ITG simulations demonstrate the broken gyro Bohm scaling paradigm of Garbet and Waltz [Phys. Plasmas 3, 1898 (1996)]. Since broken gyro Bohm scaling depends on the actual rotational velocity shear rates competing with mode growth rates, direct comprehensive simulations of the DIII-D ρ*-scaled L-mode experiments are presented as a quantitative test of gyrokinetics and the paradigm. (author)
Waltz, R. E.; Waelbroeck, F. L.
2012-03-01
Static external resonant magnetic field perturbations (RMPs) have been added to the gyrokinetic code GYRO [J. Candy and R. E. Waltz, J. Comp. Phys. 186, 545 (2003)]. This allows nonlinear gyrokinetic simulations of the nonambipolar radial current flow jr, and the corresponding j→×B→ plasma torque (density) R[jrBp/c], induced by magnetic islands that break the toroidal symmetry of a tokamak. This extends the previous GYRO formulation for the transport of toroidal angular momentum (TAM) [R. E. Waltz, G. M. Staebler, J. Candy, and F. L. Hinton, Phys. Plasmas 14, 122507 (2007); errata 16, 079902 (2009)]. The focus is on electrostatic full torus radial slice simulations of externally induced q =m/n=6/3 islands with widths 5% of the minor radius or about 20 ion gyroradii. Up to moderately strong E ×B rotation, the island torque scales with the radial electric field at the resonant surface Er, the island width w, and the intensity I of the high-n micro-turbulence, as Erw√I . The radial current inside the island is carried (entirely in the n =3 component) and almost entirely by the ion E ×B flux, since the electron E ×B and magnetic flutter particle fluxes are cancelled. The net island torque is null at zero Er rather than at zero toroidal rotation. This means that while the expected magnetic braking of the toroidal plasma rotation occurs at strong co- and counter-current rotation, at null toroidal rotation, there is a small co-directed magnetic acceleration up to the small diamagnetic (ion pressure gradient driven) co-rotation corresponding to the zero Er and null torque. This could be called the residual stress from an externally induced island. At zero Er, the only effect is the expected partial flattening of the electron temperature gradient within the island. Finite-beta GYRO simulations demonstrate almost complete RMP field screening and n =3 mode unlocking at strong Er.
International Nuclear Information System (INIS)
Chen, Yang
2012-01-01
At Colorado University-Boulder the primary task is to extend our gyrokinetic Particle-in-Cell simulation of tokamak micro-turbulence and transport to the area of energetic particle physics. We have implemented a gyrokinetic ion/massless fluid electron hybrid model in the global δf-PIC code GEM, and benchmarked the code with analytic results on the thermal ion radiative damping rate of Toroidal Alfven Eigenmodes (TAE) and with mode frequency and spatial structure from eigenmode analysis. We also performed nonlinear simulations of both a single-n mode (n is the toroidal mode number) and multiple-n modes, and in the case of single-n, benchmarked the code on the saturation amplitude vs. particle collision rate with analytical theory. Most simulations use the f method for both ions species, but we have explored the full-f method for energetic particles in cases where the burst amplitude of the excited instabilities is large as to cause significant re-distribution or loss of the energetic particles. We used the hybrid model to study the stability of high-n TAEs in ITER. Our simulations show that the most unstable modes in ITER lie in the rage of 10 α (0) = 0.7% for the fully shaped ITER equilibrium. We also carried nonlinear simulations of the most unstable n = 15 mode and found that the saturation amplitude for the nominal ITER discharge is too low to cause large redistribution or loss of alpha particles. To include kinetic electron effects in the hybrid model we have studied a kinetic electron closure scheme for the fluid electron model. The most important element of the closure scheme is a complete Ohm's law for the parallel electric field E || , derived by combining the quasi-neutrality condition, the Ampere's equation and the v || moment of the gyrokinetic equations. A discretization method for the closure scheme is studied in detail for a three-dimensional shear-less slab plasma. It is found that for long-wavelength shear Alfven waves the kinetic closure scheme
International Nuclear Information System (INIS)
Kim, Se Yun
2009-01-01
This book deals with engineering electromagnetics. It contains seven chapters, which treats understanding of engineering electromagnetics such as magnet and electron spin, current and a magnetic field and an electromagnetic wave, Essential tool for engineering electromagnetics on rector and scalar, rectangular coordinate system and curl vector, electrostatic field with coulomb rule and method of electric images, Biot-Savart law, Ampere law and magnetic force, Maxwell equation and an electromagnetic wave and reflection and penetration of electromagnetic plane wave.
International Nuclear Information System (INIS)
Lapillonne, X.; Brunner, S.; Dannert, T.; Jolliet, S.; Marinoni, A.; Villard, L.; Goerler, T.; Jenko, F.; Merz, F.
2009-01-01
In the context of gyrokinetic flux-tube simulations of microturbulence in magnetized toroidal plasmas, different treatments of the magnetic equilibrium are examined. Considering the Cyclone DIII-D base case parameter set [Dimits et al., Phys. Plasmas 7, 969 (2000)], significant differences in the linear growth rates, the linear and nonlinear critical temperature gradients, and the nonlinear ion heat diffusivities are observed between results obtained using either an s-α or a magnetohydrodynamic (MHD) equilibrium. Similar disagreements have been reported previously [Redd et al., Phys. Plasmas 6, 1162 (1999)]. In this paper it is shown that these differences result primarily from the approximation made in the standard implementation of the s-α model, in which the straight field line angle is identified to the poloidal angle, leading to inconsistencies of order ε (ε=a/R is the inverse aspect ratio, a the minor radius and R the major radius). An equilibrium model with concentric, circular flux surfaces and a correct treatment of the straight field line angle gives results very close to those using a finite ε, low β MHD equilibrium. Such detailed investigation of the equilibrium implementation is of particular interest when comparing flux tube and global codes. It is indeed shown here that previously reported agreements between local and global simulations in fact result from the order ε inconsistencies in the s-α model, coincidentally compensating finite ρ * effects in the global calculations, where ρ * =ρ s /a with ρ s the ion sound Larmor radius. True convergence between local and global simulations is finally obtained by correct treatment of the geometry in both cases, and considering the appropriate ρ * →0 limit in the latter case.
ADVANCES IN COMPREHENSIVE GYROKINETIC SIMULATIONS OF TRANSPORT IN TOKAMAKS
International Nuclear Information System (INIS)
WALTZ, R. E; CANDY, J; HINTON, F. L; ESTRADA-MILA, C; KINSEY, J.E
2004-01-01
A continuum global gyrokinetic code GYRO has been developed to comprehensively simulate core turbulent transport in actual experimental profiles and enable direct quantitative comparisons to the experimental transport flows. GYRO not only treats the now standard ion temperature gradient (ITG) mode turbulence, but also treats trapped and passing electrons with collisions and finite β, equilibrium ExB shear stabilization, and all in real tokamak geometry. Most importantly the code operates at finite relative gyroradius (ρ * ) so as to treat the profile shear stabilization and nonlocal effects which can break gyroBohm scaling. The code operates in either a cyclic flux-tube limit (which allows only gyroBohm scaling) or globally with physical profile variation. Bohm scaling of DIII-D L-mode has been simulated with power flows matching experiment within error bars on the ion temperature gradient. Mechanisms for broken gyroBohm scaling, neoclassical ion flows embedded in turbulence, turbulent dynamos and profile corrugations, are illustrated
DEFF Research Database (Denmark)
This book is dedicated to various aspects of electromagnetic wave theory and its applications in science and technology. The covered topics include the fundamental physics of electromagnetic waves, theory of electromagnetic wave propagation and scattering, methods of computational analysis......, material characterization, electromagnetic properties of plasma, analysis and applications of periodic structures and waveguide components, etc....
Aspects of turbulence in nonlinear systems. Year one final report, February 1-October 31, 1985
International Nuclear Information System (INIS)
Frieman, E.A.; Hagan, W.K.
1985-07-01
Gyrokinetic theory was developed from a pragmatic point of view. Since our interest in gyrokinetic theory is to ultimately shed some light on drift wave turbulence and anomalous transport, we have tried from the outset to incorporate into our theory some of the characteristics of these phenomena as measured in experiments. This approach has led to a theory in which two time and two space scales naturally emerge. We were also led to express the full nonlinear distribution function as an equilibrium part and pertubation part, with the equilibrium being driven by the higher order interactions of the rapid fluctuations
Energy Technology Data Exchange (ETDEWEB)
Mikkelsen, D. R., E-mail: dmikkelsen@pppl.gov; Bitter, M.; Delgado-Aparicio, L.; Hill, K. W. [Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, New Jersey 08543 (United States); Greenwald, M.; Howard, N. T.; Hughes, J. W.; Rice, J. E. [MIT Plasma Science and Fusion Center, 175 Albany St., Cambridge, Massachusetts 02139 (United States); Reinke, M. L. [MIT Plasma Science and Fusion Center, 175 Albany St., Cambridge, Massachusetts 02139 (United States); York Plasma Institute, Department of Physics, University of York, Heslington, York YO10 5DD (United Kingdom); Podpaly, Y. [MIT Plasma Science and Fusion Center, 175 Albany St., Cambridge, Massachusetts 02139 (United States); AAAS S and T Fellow placed in the Directorate for Engineering, NSF, 4201 Wilson Blvd., Arlington, Virginia 22230 (United States); Ma, Y. [MIT Plasma Science and Fusion Center, 175 Albany St., Cambridge, Massachusetts 02139 (United States); ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, 13067 St Paul Lez Durance Cedex (France); Candy, J.; Waltz, R. E. [General Atomics, P.O. Box 85608, San Diego, California 92186-5608 (United States)
2015-06-15
Peaked density profiles in low-collisionality AUG and JET H-mode plasmas are probably caused by a turbulently driven particle pinch, and Alcator C-Mod experiments confirmed that collisionality is a critical parameter. Density peaking in reactors could produce a number of important effects, some beneficial, such as enhanced fusion power and transport of fuel ions from the edge to the core, while others are undesirable, such as lower beta limits, reduced radiation from the plasma edge, and consequently higher divertor heat loads. Fundamental understanding of the pinch will enable planning to optimize these impacts. We show that density peaking is predicted by nonlinear gyrokinetic turbulence simulations based on measured profile data from low collisionality H-mode plasma in Alcator C-Mod. Multiple ion species are included to determine whether hydrogenic density peaking has an isotope dependence or is influenced by typical levels of low-Z impurities, and whether impurity density peaking depends on the species. We find that the deuterium density profile is slightly more peaked than that of hydrogen, and that experimentally relevant levels of boron have no appreciable effect on hydrogenic density peaking. The ratio of density at r/a = 0.44 to that at r/a = 0.74 is 1.2 for the majority D and minority H ions (and for electrons), and increases with impurity Z: 1.1 for helium, 1.15 for boron, 1.3 for neon, 1.4 for argon, and 1.5 for molybdenum. The ion temperature profile is varied to match better the predicted heat flux with the experimental transport analysis, but the resulting factor of two change in heat transport has only a weak effect on the predicted density peaking.
Gyrokinetic approach to the propagation of electromagnetic waves in nonuniform bounded plasma slabs
International Nuclear Information System (INIS)
Sauter, O.; Vaclavik, J.
1994-05-01
A new code, SEMAL, has been developed which solves the linearized Vlasov-Maxwell wave equations to all orders in Larmor radii. Arbitrary density and temperature profiles as well as nonuniform magnetic fields are considered in slab geometry. The vacuum regions adjacent to the plasma slab are limited by perfect conducting walls and contain an antenna as an excitation source. The linear response is obtained by solving the system of one first-order and two second-order integro-differential equations using a non-polluting finite element discretization. The general equations in the Fourier space, derived in a new comprehensive way, and their inverse transform, using k y =0, are described as well as the convergence and non-polluting properties of the method. We present the results concerning the influence of alpha particles on ICRF heating schemes for ITER, where we show that small alphas concentration can alter the steady-state operation envisaged with ICRF fast wave current-drive. (author) 7 figs., 3 tabs., 28 refs
Full-f gyrokinetic simulation over a confinement time
Energy Technology Data Exchange (ETDEWEB)
Idomura, Yasuhiro, E-mail: idomura.yasuhiro@jaea.go.jp [Japan Atomic Energy Agency, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8587 (Japan)
2014-02-15
A long time ion temperature gradient driven turbulence simulation over a confinement time is performed using the full-f gyrokinetic Eulerian code GT5D. The convergence of steady temperature and rotation profiles is examined, and it is shown that the profile relaxation can be significantly accelerated when the simulation is initialized with linearly unstable temperature profiles. In the steady state, the temperature profile and the ion heat diffusivity are self-consistently determined by the power balance condition, while the intrinsic rotation profile is sustained by complicated momentum transport processes without momentum input. The steady turbulent momentum transport is characterized by bursty non-diffusive fluxes, and the resulting turbulent residual stress is consistent with the profile shear stress theory [Y. Camenen et al., “Consequences of profile shearing on toroidal momentum transport,” Nucl. Fusion 51, 073039 (2011)] in which the residual stress depends not only on the profile shear and the radial electric field shear but also on the radial electric field itself. Based on the toroidal angular momentum conservation, it is found that in the steady null momentum transport state, the turbulent residual stress is cancelled by the neoclassical counterpart, which is greatly enhanced in the presence of turbulent fluctuations.
An Efficient Method for Verifying Gyrokinetic Microstability Codes
Bravenec, R.; Candy, J.; Dorland, W.; Holland, C.
2009-11-01
Benchmarks for gyrokinetic microstability codes can be developed through successful ``apples-to-apples'' comparisons among them. Unlike previous efforts, we perform the comparisons for actual discharges, rendering the verification efforts relevant to existing experiments and future devices (ITER). The process requires i) assembling the experimental analyses at multiple times, radii, discharges, and devices, ii) creating the input files ensuring that the input parameters are faithfully translated code-to-code, iii) running the codes, and iv) comparing the results, all in an organized fashion. The purpose of this work is to automate this process as much as possible: At present, a python routine is used to generate and organize GYRO input files from TRANSP or ONETWO analyses. Another routine translates the GYRO input files into GS2 input files. (Translation software for other codes has not yet been written.) Other python codes submit the multiple GYRO and GS2 jobs, organize the results, and collect them into a table suitable for plotting. (These separate python routines could easily be consolidated.) An example of the process -- a linear comparison between GYRO and GS2 for a DIII-D discharge at multiple radii -- will be presented.
Gyrokinetic theory and dynamics of the tokamak edge
Energy Technology Data Exchange (ETDEWEB)
Scott, B. [Max-Planck-Institut fuer Plasmaphysik, Garching (Germany)
2016-08-15
The validity of modern gyrokinetic field theory is assessed for the tokamak edge. The basic structure of the Lagrangian and resulting equations and their conservation laws is reviewed. The conventional microturbulence ordering for expansion is small potential/arbitrary wavelength. The equilibrium ordering for expansion is long wavelength/arbitrary amplitude. The long-wavelength form of the conventional Lagrangian is derived in detail. The two Lagrangians are shown to match at long wavelength if the E x B Mach number is small enough for its corrections to the gyroaveraging to be neglected. Therefore, the conventional derivation and its Lagrangian can be used at all wavelengths if these conditions are satisfied. Additionally, dynamical compressibility of the magnetic field can be neglected if the plasma beta is small. This allows general use of a shear-Alfven Lagrangian for edge turbulence and self consistent equilibrium-scale phenomena for flows, currents, and heat fluxes for conventional tokamaks without further modification by higher-order terms. Corrections in polarisation and toroidal angular momentum transport due to these higher-order terms for global edge turbulence computations are shown to be small. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Local gyrokinetic study of electrostatic microinstabilities in dipole plasmas
Xie, Hua-sheng; Zhang, Yi; Huang, Zi-cong; Ou, Wei-ke; Li, Bo
2017-12-01
A linear gyrokinetic particle-in-cell scheme, which is valid for an arbitrary perpendicular wavelength k⊥ρi and includes the parallel dynamic along the field line, is developed to study the local electrostatic drift modes in point and ring dipole plasmas. We find that the most unstable mode in this system can be either the electron mode or the ion mode. The properties and relations of these modes are studied in detail as a function of k⊥ρi , the density gradient κn, the temperature gradient κT, electron to ion temperature ratio τ=Te/Ti , and mass ratio mi/me . For conventional weak gradient parameters, the mode is on the ground state (with eigenstate number l = 0) and especially k∥˜0 for small k⊥ρi . Thus, the bounce averaged dispersion relation is also derived for comparison. For strong gradient and large k⊥ρi , most interestingly, higher order eigenstate modes with even (e.g., l = 2, 4) or odd (e.g., l = 1) parity can be most unstable, which is not expected in the previous studies. High order eigenstate can also easily be most unstable at weak gradient when τ>10 . This work can be particularly important to understand the turbulent transport in laboratory and space magnetosphere.
Gyrokinetic continuum simulations of turbulence in the Texas Helimak
Bernard, T. N.; Shi, E. L.; Hammett, G. W.; Hakim, A.; Taylor, E. I.
2017-10-01
We have used the Gkeyll code to perform 3x-2v full-f gyrokinetic continuum simulations of electrostatic plasma turbulence in the Texas Helimak. The Helimak is an open field-line experiment with magnetic curvature and shear. It is useful for validating numerical codes due to its extensive diagnostics and simple, helical geometry, which is similar to the scrape-off layer region of tokamaks. Interchange and drift-wave modes are the main turbulence mechanisms in the device, and potential biasing is applied to study the effect of velocity shear on turbulence reduction. With Gkeyll, we varied field-line pitch angle and simulated biased and unbiased cases to study different turbulent regimes and turbulence reduction. These are the first kinetic simulations of the Helimak and resulting plasma profiles agree fairly well with experimental data. This research demonstrates Gkeyll's progress towards 5D simulations of the SOL region of fusion devices. Supported by the U.S. DOE SCGSR program under contract DE-SC0014664, the Max-Planck/Princeton Center for Plasma Physics, the SciDAC Center for the Study of Plasma Microturbulence, and DOE contract DE-AC02-09CH11466.
Database-driven web interface automating gyrokinetic simulations for validation
Ernst, D. R.
2010-11-01
We are developing a web interface to connect plasma microturbulence simulation codes with experimental data. The website automates the preparation of gyrokinetic simulations utilizing plasma profile and magnetic equilibrium data from TRANSP analysis of experiments, read from MDSPLUS over the internet. This database-driven tool saves user sessions, allowing searches of previous simulations, which can be restored to repeat the same analysis for a new discharge. The website includes a multi-tab, multi-frame, publication quality java plotter Webgraph, developed as part of this project. Input files can be uploaded as templates and edited with context-sensitive help. The website creates inputs for GS2 and GYRO using a well-tested and verified back-end, in use for several years for the GS2 code [D. R. Ernst et al., Phys. Plasmas 11(5) 2637 (2004)]. A centralized web site has the advantage that users receive bug fixes instantaneously, while avoiding the duplicated effort of local compilations. Possible extensions to the database to manage run outputs, toward prototyping for the Fusion Simulation Project, are envisioned. Much of the web development utilized support from the DoE National Undergraduate Fellowship program [e.g., A. Suarez and D. R. Ernst, http://meetings.aps.org/link/BAPS.2005.DPP.GP1.57.
Advances in comprehensive gyrokinetic simulations of transport in tokamaks
International Nuclear Information System (INIS)
Waltz, R.E.; Candy, J.; Hinton, F.L.; Estrada-Mila, C.; Kinsey, J.E.
2005-01-01
A continuum global gyrokinetic code GYRO has been developed to comprehensively simulate core turbulent transport in actual experimental profiles and enable direct quantitative comparisons to the experimental transport flows. GYRO not only treats the now standard ion temperature gradient (ITG) mode turbulence, but also treats trapped and passing electrons with collisions and finite β, equilibrium ExB shear stabilization, and all in real tokamak geometry. Most importantly the code operates at finite relative gyroradius (ρ*) so as to treat the profile shear stabilization and nonlocal effects which can break gyroBohm scaling. The code operates in either a cyclic flux-tube limit (which allows only gyroBohm scaling) or globally with physical profile variation. Bohm scaling of DIII-D L-mode has been simulated with power flows matching experiment within error bars on the ion temperature gradient. Mechanisms for broken gyroBohm scaling, neoclassical ion flows embedded in turbulence, turbulent dynamos and profile corrugations, are illustrated. (author)
ADVANCES IN COMPREHENSIVE GYROKINETIC SIMULATIONS OF TRANSPORT IN TOKAMAKS
International Nuclear Information System (INIS)
WALTZ, RE; CANDY, J; HINTON, FL; ESTRADA-MILA, C; KINSEY, JE.
2004-01-01
A continuum global gyrokinetic code GYRO has been developed to comprehensively simulate core turbulent transport in actual experimental profiles and enable direct quantitative comparisons to the experimental transport flows. GYRO not only treats the now standard ion temperature gradient (ITG) mode turbulence, but also treats trapped and passing electrons with collisions and finite β, equilibrium ExB shear stabilization, and all in real tokamak geometry. Most importantly the code operates at finite relative gyroradius (ρ * ) so as to treat the profile shear stabilization and nonlocal effects which can break gyroBohm scaling. The code operates in either a cyclic flux-tube limit (which allows only gyroBohm scaling) or a globally with physical profile variation. Rohm scaling of DIII-D L-mode has been simulated with power flows matching experiment within error bars on the ion temperature gradient. Mechanisms for broken gyroBohm scaling, neoclassical ion flows embedded in turbulence, turbulent dynamos and profile corrugations, plasma pinches and impurity flow, and simulations at fixed flow rather than fixed gradient are illustrated and discussed
International Nuclear Information System (INIS)
Sato, T; Masuda, A; Sanada, T
2015-01-01
This paper presents an experimental verification of a self-excitation control of a resonance- type vibration energy harvester with a Duffing-type nonlinearity which is designed to perform effectively in a wide frequency range. For the conventional linear vibration energy harvester, the performance of the power generation at the resonance frequency and the bandwidth of the resonance peak are trade-off. The resonance frequency band can be expanded by introducing a Duffing-type nonlinear oscillator in order to enable the harvester to generate larger electric power in a wider frequency range. However, since such nonlinear oscillator can have multiple stable steady-state solutions in the resonance band, it is difficult for the nonlinear harvester to maintain the high performance of the power generation constantly. The principle of self-excitation and entrainment has been utilized to provide the global stability to the highest-energy solution by destabilizing other unexpected lower-energy solutions by introducing a switching circuit of the load resistance between positive and the negative values depending on the response amplitude of the oscillator. It has been experimentally validated that this control law imparts the self-excitation capability to the oscillator to show an entrainment into the highest-energy solution. (paper)
A 3D gyrokinetic particle-in-cell simulation of fusion plasma microturbulence on parallel computers
Williams, T. J.
1992-12-01
One of the grand challenge problems now supported by HPCC is the Numerical Tokamak Project. A goal of this project is the study of low-frequency micro-instabilities in tokamak plasmas, which are believed to cause energy loss via turbulent thermal transport across the magnetic field lines. An important tool in this study is gyrokinetic particle-in-cell (PIC) simulation. Gyrokinetic, as opposed to fully-kinetic, methods are particularly well suited to the task because they are optimized to study the frequency and wavelength domain of the microinstabilities. Furthermore, many researchers now employ low-noise delta(f) methods to greatly reduce statistical noise by modelling only the perturbation of the gyrokinetic distribution function from a fixed background, not the entire distribution function. In spite of the increased efficiency of these improved algorithms over conventional PIC algorithms, gyrokinetic PIC simulations of tokamak micro-turbulence are still highly demanding of computer power--even fully-vectorized codes on vector supercomputers. For this reason, we have worked for several years to redevelop these codes on massively parallel computers. We have developed 3D gyrokinetic PIC simulation codes for SIMD and MIMD parallel processors, using control-parallel, data-parallel, and domain-decomposition message-passing (DDMP) programming paradigms. This poster summarizes our earlier work on codes for the Connection Machine and BBN TC2000 and our development of a generic DDMP code for distributed-memory parallel machines. We discuss the memory-access issues which are of key importance in writing parallel PIC codes, with special emphasis on issues peculiar to gyrokinetic PIC. We outline the domain decompositions in our new DDMP code and discuss the interplay of different domain decompositions suited for the particle-pushing and field-solution components of the PIC algorithm.
Parker, Jeffrey B.; LoDestro, Lynda L.; Told, Daniel; Merlo, Gabriele; Ricketson, Lee F.; Campos, Alejandro; Jenko, Frank; Hittinger, Jeffrey A. F.
2018-05-01
The vast separation dividing the characteristic times of energy confinement and turbulence in the core of toroidal plasmas makes first-principles prediction on long timescales extremely challenging. Here we report the demonstration of a multiple-timescale method that enables coupling global gyrokinetic simulations with a transport solver to calculate the evolution of the self-consistent temperature profile. This method, which exhibits resiliency to the intrinsic fluctuations arising in turbulence simulations, holds potential for integrating nonlocal gyrokinetic turbulence simulations into predictive, whole-device models.
Including collisions in gyrokinetic tokamak and stellarator simulations
International Nuclear Information System (INIS)
Kauffmann, Karla
2012-01-01
Particle and heat transport in fusion devices often exceed the neoclassical prediction. This anomalous transport is thought to be produced by turbulence caused by microinstabilities such as ion and electron-temperature-gradient (ITG/ETG) and trapped-electron-mode (TEM) instabilities, the latter ones known for being strongly influenced by collisions. Additionally, in stellarators, the neoclassical transport can be important in the core, and therefore investigation of the effects of collisions is an important field of study. Prior to this thesis, however, no gyrokinetic simulations retaining collisions had been performed in stellarator geometry. In this work, collisional effects were added to EUTERPE, a previously collisionless gyrokinetic code which utilizes the δf method. To simulate the collisions, a pitch-angle scattering operator was employed, and its implementation was carried out following the methods proposed in [Takizuka and Abe 1977, Vernay Master's thesis 2008]. To test this implementation, the evolution of the distribution function in a homogeneous plasma was first simulated, where Legendre polynomials constitute eigenfunctions of the collision operator. Also, the solution of the Spitzer problem was reproduced for a cylinder and a tokamak. Both these tests showed that collisions were correctly implemented and that the code is suited for more complex simulations. As a next step, the code was used to calculate the neoclassical radial particle flux by neglecting any turbulent fluctuations in the distribution function and the electric field. Particle fluxes in the neoclassical analytical regimes were simulated for tokamak and stellarator (LHD) configurations. In addition to the comparison with analytical fluxes, a successful benchmark with the DKES code was presented for the tokamak case, which further validates the code for neoclassical simulations. In the final part of the work, the effects of collisions were investigated for slab and toroidal ITGs and
Including collisions in gyrokinetic tokamak and stellarator simulations
Energy Technology Data Exchange (ETDEWEB)
Kauffmann, Karla
2012-04-10
Particle and heat transport in fusion devices often exceed the neoclassical prediction. This anomalous transport is thought to be produced by turbulence caused by microinstabilities such as ion and electron-temperature-gradient (ITG/ETG) and trapped-electron-mode (TEM) instabilities, the latter ones known for being strongly influenced by collisions. Additionally, in stellarators, the neoclassical transport can be important in the core, and therefore investigation of the effects of collisions is an important field of study. Prior to this thesis, however, no gyrokinetic simulations retaining collisions had been performed in stellarator geometry. In this work, collisional effects were added to EUTERPE, a previously collisionless gyrokinetic code which utilizes the {delta}f method. To simulate the collisions, a pitch-angle scattering operator was employed, and its implementation was carried out following the methods proposed in [Takizuka and Abe 1977, Vernay Master's thesis 2008]. To test this implementation, the evolution of the distribution function in a homogeneous plasma was first simulated, where Legendre polynomials constitute eigenfunctions of the collision operator. Also, the solution of the Spitzer problem was reproduced for a cylinder and a tokamak. Both these tests showed that collisions were correctly implemented and that the code is suited for more complex simulations. As a next step, the code was used to calculate the neoclassical radial particle flux by neglecting any turbulent fluctuations in the distribution function and the electric field. Particle fluxes in the neoclassical analytical regimes were simulated for tokamak and stellarator (LHD) configurations. In addition to the comparison with analytical fluxes, a successful benchmark with the DKES code was presented for the tokamak case, which further validates the code for neoclassical simulations. In the final part of the work, the effects of collisions were investigated for slab and toroidal
HPC parallel programming model for gyrokinetic MHD simulation
International Nuclear Information System (INIS)
Naitou, Hiroshi; Yamada, Yusuke; Tokuda, Shinji; Ishii, Yasutomo; Yagi, Masatoshi
2011-01-01
The 3-dimensional gyrokinetic PIC (particle-in-cell) code for MHD simulation, Gpic-MHD, was installed on SR16000 (“Plasma Simulator”), which is a scalar cluster system consisting of 8,192 logical cores. The Gpic-MHD code advances particle and field quantities in time. In order to distribute calculations over large number of logical cores, the total simulation domain in cylindrical geometry was broken up into N DD-r × N DD-z (number of radial decomposition times number of axial decomposition) small domains including approximately the same number of particles. The axial direction was uniformly decomposed, while the radial direction was non-uniformly decomposed. N RP replicas (copies) of each decomposed domain were used (“particle decomposition”). The hybrid parallelization model of multi-threads and multi-processes was employed: threads were parallelized by the auto-parallelization and N DD-r × N DD-z × N RP processes were parallelized by MPI (message-passing interface). The parallelization performance of Gpic-MHD was investigated for the medium size system of N r × N θ × N z = 1025 × 128 × 128 mesh with 4.196 or 8.192 billion particles. The highest speed for the fixed number of logical cores was obtained for two threads, the maximum number of N DD-z , and optimum combination of N DD-r and N RP . The observed optimum speeds demonstrated good scaling up to 8,192 logical cores. (author)
Electromagnetic microinstabilities in tokamak plasmas using a global spectral approach
Energy Technology Data Exchange (ETDEWEB)
Falchetto, G. L
2002-03-01
Electromagnetic microinstabilities in tokamak plasmas are studied by means of a linear global eigenvalue numerical code. The code is the electromagnetic extension of an existing electrostatic global gyrokinetic spectral toroidal code, called GLOGYSTO. Ion dynamics is described by the gyrokinetic equation, so that ion finite Larmor radius effects are taken into account to all orders. Non adiabatic electrons are included in the model, with passing particles described by the drift-kinetic equation and trapped particles through the bounce averaged drift-kinetic equation. A low frequency electromagnetic perturbation is applied to a low -but finite- {beta}plasma (where the parameter {beta} identifies the ratio of plasma pressure to magnetic pressure); thus, the parallel perturbations of the magnetic field are neglected. The system is closed by the quasi-neutrality equation and the parallel component of Ampere's law. The formulation is applied to a large aspect ratio toroidal configuration, with circular shifted surfaces. Such a simple configuration enables one to derive analytically the gyrocenter trajectories. The system is solved in Fourier space, taking advantage of a decomposition adapted to the toroidal geometry. The major contributions of this thesis are as follows. The electromagnetic effects on toroidal Ion Temperature Gradient driven (ITG) modes are studied. The stabilization of these modes with increasing {beta}, as predicted in previous work, is confirmed. The inclusion of trapped electron dynamics enables the study of its coupling to the ITG modes and of Trapped Electron Modes (TEM) .The effects of finite {beta} are considered together with those of different magnetic shear profiles and of the Shafranov shift. The threshold for the destabilization of an electromagnetic mode is identified. Moreover, the global formulation yields for the first time the radial structure of this so-called Alfvenic Ion Temperature Gradient (AITG) mode. The stability of the
Interacting electromagnetic waves in general relativity
International Nuclear Information System (INIS)
Griffiths, J.B.
1976-01-01
The problem is considered of finding exact solutions of the Einstein-Maxwell equations which describe the physical situation of two colliding and subsequently interacting electromagnetic waves. The general theory of relativity predicts a nonlinear interaction between electromagnetic waves. The situation is described using an approximate geometrical method, and a new exact solution describing two interacting electromagnetic waves is given. This describes waves emitted from two sources mutually focusing each other on the opposite source. (author)
Electromagnetic wave analogue of electronic diode
Shadrivov, Ilya V.; Powell, David A.; Kivshar, Yuri S.; Fedotov, Vassili A.; Zheludev, Nikolay I.
2010-01-01
An electronic diode is a nonlinear semiconductor circuit component that allows conduction of electrical current in one direction only. A component with similar functionality for electromagnetic waves, an electromagnetic isolator, is based on the Faraday effect of the polarization state rotation and is also a key component of optical and microwave systems. Here we demonstrate a chiral electromagnetic diode, which is a direct analogue of an electronic diode: its functionality is underpinned by ...
Merlo, G.; Brunner, S.; Huang, Z.; Coda, S.; Görler, T.; Villard, L.; Bañón Navarro, A.; Dominski, J.; Fontana, M.; Jenko, F.; Porte, L.; Told, D.
2018-03-01
Axisymmetric (n = 0) density fluctuations measured in the TCV tokamak are observed to possess a frequency f 0 which is either varying (radially dispersive oscillations) or a constant over a large fraction of the plasma minor radius (radially global oscillations) as reported in a companion paper (Z Huang et al, this issue). Given that f 0 scales with the sound speed and given the poloidal structure of density fluctuations, these oscillations were interpreted as Geodesic Acoustic Modes, even though f 0 is in fact smaller than the local linear GAM frequency {f}{GAM}. In this work we employ the Eulerian gyrokinetic code GENE to simulate TCV relevant conditions and investigate the nature and properties of these oscillations, in particular their relation to the safety factor profile. Local and global simulations are carried out and a good qualitative agreement is observed between experiments and simulations. By varying also the plasma temperature and density profiles, we conclude that a variation of the edge safety factor alone is not sufficient to induce a transition from global to radially inhomogeneous oscillations, as was initially suggested by experimental results. This transition appears instead to be the combined result of variations in the different plasma profiles, collisionality and finite machine size effects. Simulations also show that radially global GAM-like oscillations can be observed in all fluxes and fluctuation fields, suggesting that they are the result of a complex nonlinear process involving also finite toroidal mode numbers and not just linear global GAM eigenmodes.
A minimal collision operator for implementing neoclassical transport in gyrokinetic simulations
International Nuclear Information System (INIS)
Garbet, X.; Dif-Pradalier, G.; Nguyen, C.; Angelino, P.; Sarazin, Y.; Grandgirard, V.; Ghendrih, P.; Samain, A.
2008-01-01
This paper presents a class of collision operators, which reproduce neoclassical transport and comply with the constraints of a full-f global gyrokinetic code. The assessment of these operators is based on a variational entropy method, which allows a fast calculation of the neoclassical diffusivity and poloidal velocity.
International Nuclear Information System (INIS)
Lee, W.W.
2003-01-01
Particle simulation has played an important role for the recent investigations on turbulence in magnetically confined plasmas. In this paper, theoretical and numerical properties of a gyrokinetic plasma as well as its relationship with magnetohydrodynamics (MHD) are discussed with the ultimate aim of simulating microturbulence in transport time scale using massively parallel computers
Mantica, Paola
2016-10-01
Heat transport experiments in JET, based on ICRH heat flux scans and temperature modulation, have confirmed the importance of two transport mechanisms that are often neglected in modeling experimental results, but are crucial to reach agreement between theory and experiment and may be significant in ITER. The first mechanism is the stabilizing effect of the total pressure gradient (including fast ions) on ITG driven ion heat transport. Such stabilization is found in non-linear gyro-kinetic electro-magnetic simulations using GENE and GYRO, and is the explanation for the observed loss of ion stiffness in the core of high NBI-power JET plasmas. The effect was recently observed also in JET plasmas with dominant ICRH heating and small rotation, due to ICRH fast ions, which is promising for ITER. Such mechanism dominates over ExB flow shear in the core and needs to be included in quasi-linear models to increase their ability to capture the relevant physics. The second mechanism is the capability of small- scale ETG instabilities to carry a significant fraction of electron heat. A decrease in Te peaking is observed when decreasing Zeff Te/Ti, which cannot be ascribed to TEMs but is in line with ETGs. Non-linear GENE single-scale simulations of ETGs and ITG/TEMs show that the ITG/TEM electron heat flux is not enough to match experiment. TEM stiffness is also much lower than measured. In the ETG single scale simulations the external flow shear is used to saturate the ETG streamers. Multi-scale simulations are ongoing, in which the ion zonal flows are the main saturating mechanism for ETGs. These costly simulations should provide the final answer on the importance of ETG-driven electron heat flux in JET. with JET contributors [F.Romanelli, Proc.25thIAEA FEC]. Supported by EUROfusion Grant 633053.
Linear and nonlinear kinetic-stability studies in tokamaks
International Nuclear Information System (INIS)
Tang, W.M.; Chance, M.S.; Chen, L.; Krommes, J.A.; Lee, W.W.; Rewoldt, G.
1982-09-01
This paper presents results of theoretical investigations on important linear kinetic properties of low frequency instabilities in toroidal systems and on nonlinear processes which could significantly influence their impact on anomalous transport. Analytical and numerical methods and also particle simulations have been employed to carry out these studies. In particular, the following subjects are considered: (1) linear stability analysis of kinetic instabilities for realistic tokamak equilibria and the application of such calculations to the PDX and PLT tokamak experiments including the influence of a hot beam-ion component; (2) determination of nonlinearly saturated, statistically steady states of three interacting drift modes; and (3) gyrokinetic particle simulation of drift instabilities
Nonlinear hybrid simulation of toroidicity-induced alfven eigenmode
International Nuclear Information System (INIS)
Fu, G.Y.; Park, W.
1994-11-01
Gyrokinetic/Magnetohydrodynamics hybrid simulations have been carried out using MH3D-K code to study the nonlinear saturation of the toroidicity-induced Alfven eigenmode driven by energetic particles in a tokamak plasma. It is shown that the wave particle trapping is the nonlinear saturation mechanism for the parameters considered. The corresponding density profile flattening of hot particles is observed. The saturation amplitude is proportional to the square of linear growth rate. In addition to TAE modes, a new n = 1, m = 0 global Alfven eigenmode is shown to be excited by the energetic particles
Energy Technology Data Exchange (ETDEWEB)
Yamashita, H; Marinova, I; Cingoski, V [eds.
2002-07-01
These proceedings contain papers relating to the 3rd Japanese-Bulgarian-Macedonian Joint Seminar on Applied Electromagnetics. Included are the following groups: Numerical Methods I; Electrical and Mechanical System Analysis and Simulations; Inverse Problems and Optimizations; Software Methodology; Numerical Methods II; Applied Electromagnetics.
International Nuclear Information System (INIS)
Yamashita, H.; Marinova, I.; Cingoski, V.
2002-01-01
These proceedings contain papers relating to the 3rd Japanese-Bulgarian-Macedonian Joint Seminar on Applied Electromagnetics. Included are the following groups: Numerical Methods I; Electrical and Mechanical System Analysis and Simulations; Inverse Problems and Optimizations; Software Methodology; Numerical Methods II; Applied Electromagnetics
International Nuclear Information System (INIS)
Bosanac, Slobodan Danko
2016-01-01
This book is devoted to theoretical methods used in the extreme circumstances of very strong electromagnetic fields. The development of high power lasers, ultrafast processes, manipulation of electromagnetic fields and the use of very fast charged particles interacting with other charges requires an adequate theoretical description. Because of the very strong electromagnetic field, traditional theoretical approaches, which have primarily a perturbative character, have to be replaced by descriptions going beyond them. In the book an extension of the semi-classical radiation theory and classical dynamics for particles is performed to analyze single charged atoms and dipoles submitted to electromagnetic pulses. Special attention is given to the important problem of field reaction and controlling dynamics of charges by an electromagnetic field.
Improvements on nonlinear gyrokinetic particle simulations based on δf-discretization scheme
International Nuclear Information System (INIS)
Zorat, R.; Tessarotto, M.
1998-01-01
In this work various issues regarding the definition of improved theoretical models appropriate to describe the dynamics of confined magnetoplasmas by particle simulation methods are proposed. These concern in particular an improved non linear δf discretization scheme and the treatment of binary, i.e. Coulomb, and collective interactions. (orig.)
Comment on 'Nonlinear gyrokinetic theory with polarization drift' [Phys. Plasmas 17, 082304 (2010)
International Nuclear Information System (INIS)
Leerink, S.; Parra, F. I.; Heikkinen, J. A.
2010-01-01
In this comment, we show that by using the discrete particle distribution function the changes of the phase-space volume of gyrocenter coordinates due to the fluctuating ExB velocity do not explicitly appear in the Poisson equation and the [Sosenko et al., Phys. Scr. 64, 264 (2001)] result is recovered. It is demonstrated that there is no contradiction between the work presented by Sosenko et al. and the work presented by [Wang et al., Phys. Plasmas 17, 082304 (2010)].
International Nuclear Information System (INIS)
Waltz, R. E.; Candy, J.; Fahey, M.
2007-01-01
Electron temperature gradient (ETG) transport is conventionally defined as the electron energy transport at high wave number (high-k) where ions are adiabatic and there can be no ion energy or plasma transport. Previous gyrokinetic simulations have assumed adiabatic ions (ETG-ai) and work on the small electron gyroradius scale. However such ETG-ai simulations with trapped electrons often do not have well behaved nonlinear saturation unless fully kinetic ions (ki) and proper ion scale zonal flow modes are included. Electron energy transport is separated into ETG-ki at high-k and ion temperature gradient-trapped electron mode (ITG/TEM) at low-k. Expensive (more computer-intensive), high-resolution, large-ion-scale flux-tube simulations coupling ITG/TEM and ETG-ki turbulence are presented. These require a high effective Reynolds number R≡[k(max)/k(min)] 2 =μ 2 , where μ=[ρ si /ρ si ] is the ratio of ion to electron gyroradii. Compute times scale faster than μ 3 . By comparing the coupled expensive simulations with (1) much cheaper (less compute-intensive), uncoupled, high-resolution, small, flux-tube ETG-ki and with (2) uncoupled low-resolution, large, flux-tube ITG/TEM simulations, and also by artificially turning ''off'' the low-k or high-k drives, it appears that ITG/TEM and ETG-ki transport are not strongly coupled so long as ETG-ki can access some nonadiabatic ion scale zonal flows and both high-k and low-k are linearly unstable. However expensive coupled simulations are required for physically accurate k-spectra of the transport and turbulence. Simulations with μ≥30 appear to represent the physical range μ>40. ETG-ki transport measured in ion gyro-Bohm units is weakly dependent on μ. For the mid-radius core tokamak plasma parameters studied, ETG-ki is about 10% of the electron energy transport, which in turn is about 30% of the total energy transport (with negligible ExB shear). However at large ExB shear sufficient to quench the low-k ITG
Moving Manifolds in Electromagnetic Fields
Directory of Open Access Journals (Sweden)
David V. Svintradze
2017-08-01
Full Text Available We propose dynamic non-linear equations for moving surfaces in an electromagnetic field. The field is induced by a material body with a boundary of the surface. Correspondingly the potential energy, set by the field at the boundary can be written as an addition of four-potential times four-current to a contraction of the electromagnetic tensor. Proper application of the minimal action principle to the system Lagrangian yields dynamic non-linear equations for moving three dimensional manifolds in electromagnetic fields. The equations in different conditions simplify to Maxwell equations for massless three surfaces, to Euler equations for a dynamic fluid, to magneto-hydrodynamic equations and to the Poisson-Boltzmann equation.
Collinear light scattering using electromagnetically induced transparency
International Nuclear Information System (INIS)
Harris, S.E.; Sokolov, A.V.; Walker, D.R.; Yavuz, D.D.; Yin, G.Y.
2001-01-01
The paper describes two types of nonlinear optical processes which are based on electromagnetically induced transparency. These are: (1) Collinear generation of FM-like Raman sidebands and (2) a type of pondermotive light scattering which is inherent to the interaction of slow light with cold atoms. Connections to other areas of EIT-based nonlinear optics are also described
International Nuclear Information System (INIS)
Leerink, S.; Heikkinen, J. A.; Janhunen, S. J.; Kiviniemi, T. P.; Nora, M.; Ogando, F.
2008-01-01
The ELMFIRE gyrokinetic simulation code has been used to perform full f simulations of the FT-2 tokamak. The dynamics of the radial electric field and the creation of poloidal velocity in the presence of turbulence are presented.
Electromagnetic wave analogue of an electronic diode
International Nuclear Information System (INIS)
Shadrivov, Ilya V; Powell, David A; Kivshar, Yuri S; Fedotov, Vassili A; Zheludev, Nikolay I
2011-01-01
An electronic diode is a nonlinear semiconductor circuit component that allows conduction of electrical current in one direction only. A component with similar functionality for electromagnetic waves, an electromagnetic isolator, is based on the Faraday effect of rotation of the polarization state and is also a key component in optical and microwave systems. Here we demonstrate a chiral electromagnetic diode, which is a direct analogue of an electronic diode: its functionality is underpinned by an extraordinarily strong nonlinear wave propagation effect in the same way as the electronic diode function is provided by the nonlinear current characteristic of a semiconductor junction. The effect exploited in this new electromagnetic diode is an intensity-dependent polarization change in an artificial chiral metamolecule. This microwave effect exceeds a similar optical effect previously observed in natural crystals by more than 12 orders of magnitude and a direction-dependent transmission that differs by a factor of 65.
International Nuclear Information System (INIS)
Liu, Dongjian; Zhang, Wenlu; McClenaghan, Joseph; Wang, Jiaqi; Lin, Zhihong
2014-01-01
Global gyrokinetic particle simulation of resistive tearing modes has been developed and verified in the gyrokinetic toroidal code (GTC). GTC linear simulations in the fluid limit of the kink-tearing and resistive tearing modes in the cylindrical geometry agree well with the resistive magnetohydrodynamic eigenvalue and initial value codes. Ion kinetic effects are found to reduce the radial width of the tearing modes. GTC simulations of the resistive tearing modes in the toroidal geometry find that the toroidicity reduces the growth rates
International Nuclear Information System (INIS)
Miller, J.S.
1987-01-01
An electromagnetic shield is described comprising: closed, electrically-conductive rings, each having an open center; and binder means for arranging the rings in a predetermined, fixed relationship relative to each other, the so-arranged rings and binder means defining an outer surface; wherein electromagnetic energy received by the shield from a source adjacent its outer surface induces an electrical current to flow in a predetermined direction adjacent and parallel to the outer surface, through the rings; and wherein each ring is configured to cause source-induced alternating current flowing through the portion of the ring closest to the outer surface to electromagnetically induce an oppositely-directed current in the portion of the ring furthest from the surface, such oppositely-directed current bucking any source-induced current in the latter ring portion and thus reducing the magnitude of current flowing through it, whereby the electromagnetic shielding effected by the shield is enhanced
Thomas, David T; Hartnett, James P; Hughes, William F
1973-01-01
The applications involving electromagnetic fields are so pervasive that it is difficult to estimate their contribution to the industrial output: generation of electricity, power transmission lines, electric motors, actuators, relays, radio, TV and microwave transmission and reception, magnetic storage, and even the mundane little magnet used to hold a paper note on the refrigerator are all electromagnetic in nature. One would be hard pressed to find a device that works without relaying on any electromagnetic principle or effect. This text provides a good theoretical understanding of the electromagnetic field equations but also treats a large number of applications. In fact, no topic is presented unless it is directly applicable to engineering design or unless it is needed for the understanding of another topic. In electrostatics, for example, the text includes discussions of photocopying, ink-jet printing, electrostatic separation and deposition, sandpaper production, paint spraying, and powder coating. In ma...
DEFF Research Database (Denmark)
Cermak, Daniel; Okutsu, Ayaka; Jørgensen, Stina Marie Hasse
2015-01-01
Daniel Cermak-Sassenrath, Ayaka Okutsu, Stina Hasse. Electromagnetic Landscape - In-between Signal, Noise and Environment. Installation and artist talk. 21th International Symposium on Electronic Art (ISEA) 2015, Vancouver, CAN, Aug 14-18, 2015.......Daniel Cermak-Sassenrath, Ayaka Okutsu, Stina Hasse. Electromagnetic Landscape - In-between Signal, Noise and Environment. Installation and artist talk. 21th International Symposium on Electronic Art (ISEA) 2015, Vancouver, CAN, Aug 14-18, 2015....
Directory of Open Access Journals (Sweden)
Taheri M.
2015-09-01
Full Text Available Background: Drug resistance is widely believed to be an increasingly serious threat to global public health. We have previously reported that short term exposure of microorganisms to diagnostic ultrasound waves could significantly alter their sensitivity to antibiotics. In our previous studies, Klebsiella pneumoniae showed major differences in the sensitivity to antibiotics in exposed and non-exposed samples. This study was aimed at investigating the alteration of antibiotic resistance of Klebsiella pneumonia, after exposure to Wi-Fi 2.4 GHz electromagnetic radiofrequency radiation. Materials and Methods: In this in vitro study, three replicate agar plates were used for each test. The antibiotic susceptibility test was carried out using disc diffusion method on Mueller Hinton agar plates and the inhibition zones in both control and exposed groups were measured. A common Wi-Fi router was used in this study as the radiofrequency exposure source. Irradiated samples were exposed to Wi-Fi radiofrequency radiation for 3, 4.5 and 8 hours. Results: Statistically significant variations of sensitivity to antibiotics were found for all studied antibiotics after 4.5 hours of RF exposure, compared to non-exposed bacteria. Interestingly, the mean diameters of the inhibition zones after 3 hours of exposure were less than those exposed for 4.5 hours. Following this rise in the sensitivity to antibiotics, a fall was observed in the bacteria exposed for 8 hours for all studied antibiotics. Conclusion: The findings of this study show a statistically significant rise in the sensitivity of Klebsiella pneumoniae to different antibiotics after 4.5 hours of exposure to 2.4 GHz Wi-Fi radiation, followed by a fall after 8 hours of exposure. These observations can be interpreted by the concept of non-linearity in the responses of Klebsiella pneumoniae to different antibiotics after exposure to electromagnetic radiofrequency radiation. As in this study a minimum level of
Verniero, J. L.; Howes, G. G.; Klein, K. G.
2018-02-01
In space and astrophysical plasmas, turbulence is responsible for transferring energy from large scales driven by violent events or instabilities, to smaller scales where turbulent energy is ultimately converted into plasma heat by dissipative mechanisms. The nonlinear interaction between counterpropagating Alfvén waves, denoted Alfvén wave collisions, drives this turbulent energy cascade, as recognized by early work with incompressible magnetohydrodynamic (MHD) equations. Recent work employing analytical calculations and nonlinear gyrokinetic simulations of Alfvén wave collisions in an idealized periodic initial state have demonstrated the key properties that strong Alfvén wave collisions mediate effectively the transfer of energy to smaller perpendicular scales and self-consistently generate current sheets. For the more realistic case of the collision between two initially separated Alfvén wavepackets, we use a nonlinear gyrokinetic simulation to show here that these key properties persist: strong Alfvén wavepacket collisions indeed facilitate the perpendicular cascade of energy and give rise to current sheets. Furthermore, the evolution shows that nonlinear interactions occur only while the wavepackets overlap, followed by a clean separation of the wavepackets with straight uniform magnetic fields and the cessation of nonlinear evolution in between collisions, even in the gyrokinetic simulation presented here which resolves dispersive and kinetic effects beyond the reach of the MHD theory.
Nature of turbulent transport across sheared zonal flows: insights from gyrokinetic simulations
International Nuclear Information System (INIS)
Sanchez, R; Newman, D E; Leboeuf, J-N; Decyk, V K
2011-01-01
The traditional view regarding the reduction of turbulence-induced transport across a stable sheared flow invokes a reduction of the characteristic length scale in the direction perpendicular to the flow as a result of the shearing and stretching of eddies caused by the differential pull exerted in the direction of the flow. A reduced effective transport coefficient then suffices to capture the reduction, that can then be readily incorporated into a transport model. However, recent evidence from gyrokinetic simulations of the toroidal ion-temperature-gradient mode suggests that the dynamics of turbulent transport across sheared flows changes in a more fundamental manner, and that the use of reduced effective transport coefficients fails to capture the full dynamics that may exhibit both subdiffusion and non-Gaussian statistics. In this contribution, after briefly reviewing these results, we propose some candidates for the physical mechanisms responsible for endowing transport with such non-diffusive characteristics, backing these proposals with new numerical gyrokinetic data.
Self-consistent gyrokinetic modeling of neoclassical and turbulent impurity transport
Estève , D. ,; Sarazin , Y.; Garbet , X.; Grandgirard , V.; Breton , S. ,; Donnel , P. ,; Asahi , Y. ,; Bourdelle , C.; Dif-Pradalier , G; Ehrlacher , C.; Emeriau , C.; Ghendrih , Ph; Gillot , C.; Latu , G.; Passeron , C.
2018-01-01
International audience; Trace impurity transport is studied with the flux-driven gyrokinetic GYSELA code [V. Grandgirard et al., Comp. Phys. Commun. 207, 35 (2016)]. A reduced and linearized multi-species collision operator has been recently implemented, so that both neoclassical and turbulent transport channels can be treated self-consistently on an equal footing. In the Pfirsch-Schlüter regime likely relevant for tungsten, the standard expression of the neoclassical impurity flux is shown t...
Renormalized perturbation theory: Vlasov-Poisson System, weak turbulence limit and gyrokinetics
International Nuclear Information System (INIS)
Zhang, Y.Z.; Mahajan, S.M.
1987-10-01
The Self-consistency of the renormalized perturbation theory is demonstrated by applying it to the Vlasov-Poisson System and showing that the theory has the correct weak turbulence limit. Energy conservation is proved to arbitrary high order for the electrostatic drift waves. The theory is applied to derive renormalized equations for a low-β gyrokinetic system. Comparison of our theory with other current theories is presented. 22 refs
Gyrokinetics Simulation of Energetic Particle Turbulence and Transport
Energy Technology Data Exchange (ETDEWEB)
Diamond, Patrick H.
2011-09-21
Progress in research during this year elucidated the physics of precession resonance and its interaction with radial scattering to form phase space density granulations. Momentum theorems for drift wave-zonal flow systems involving precession resonance were derived. These are directly generalizable to energetic particle modes. A novel nonlinear, subcritical growth mechanism was identified, which has now been verified by simulation. These results strengthen the foundation of our understanding of transport in burning plasmas
Gyrokinetics Simulation of Energetic Particle Turbulence and Transport
International Nuclear Information System (INIS)
Diamond, Patrick H.
2011-01-01
Progress in research during this year elucidated the physics of precession resonance and its interaction with radial scattering to form phase space density granulations. Momentum theorems for drift wave-zonal flow systems involving precession resonance were derived. These are directly generalizable to energetic particle modes. A novel nonlinear, subcritical growth mechanism was identified, which has now been verified by simulation. These results strengthen the foundation of our understanding of transport in burning plasmas
International Nuclear Information System (INIS)
Ito, Koji; Suetake, Norio; Aizawa, Toshie; Nakasaki, Masayoshi
1998-01-01
The present invention provides an electromagnetic pump suitable to a recycling pump for liquid sodium as coolants of an FBR type reactor. Namely, a stator module of the electromagnetic pump of the present invention comprises a plurality of outer laminate iron core units and outer stator modules stacked alternately in the axial direction. With such a constitution, even a long electromagnetic pump having a large number of outer stator coils can be manufactured without damaging electric insulation of the outer stator coils. In addition, the inner circumferential surface of the outer laminate iron cores is urged and brought into contact with the outer circumferential surface of the outer duct by an elastic material. With such a constitution, Joule loss heat generated in the outer stator coils and internal heat generated in the outer laminate iron cores can be released to an electroconductive fluid flowing the inner circumference of the outer duct by way of the outer duct. (I.S.)
Nonlinear Simulations of Trapped Electron Mode Turbulence in Low Magnetic Shear Stellarators
Faber, B. J.; Pueschel, M. J.; Terry, P. W.; Hegna, C. C.
2017-10-01
Optimized stellarators, like the Helically Symmetric eXperiment (HSX), often operate with small global magnetic shear to avoid low-order rational surfaces and magnetic islands. Nonlinear, flux-tube gyrokinetic simulations of density-gradient-driven Trapped Electron Mode (TEM) turbulence in HSX shows two distinct spectral fluctuation regions: long-wavelength slab-like TEMs localized by global magnetic shear that extend along field lines and short-wavelength TEMs localized by local magnetic shear to a single helical bad curvature region. The slab-like TEMs require computational domains significantly larger than one poloidal turn and are computationally expensive, making turbulent optimization studies challenging. A computationally more efficient, zero-average-magnetic-shear approximation is shown to sufficiently describe the relevant nonlinear physics and replicate finite-shear computations, and can be exploited in quasilinear models based on linear gyrokinetics as a feasible optimization tool. TEM quasilinear heat fluxes are computed with the zero-shear approximation and compared to experimentally-relevant nonlinear gyrokinetic TEM heat fluxes for HSX. Research supported by U.S. DoE Grants DE-FG02-99ER54546, DE-FG02-93ER54222 and DE-FG02-89ER53291.
International Nuclear Information System (INIS)
Sati, Priti; Tripathi, V. K.
2012-01-01
Parametric decay of a large amplitude electromagnetic wave into two electromagnetic modes in a rippled density plasma channel is investigated. The channel is taken to possess step density profile besides a density ripple of axial wave vector. The density ripple accounts for the momentum mismatch between the interacting waves and facilitates nonlinear coupling. For a given pump wave frequency, the requisite ripple wave number varies only a little w.r.t. the frequency of the low frequency decay wave. The radial localization of electromagnetic wave reduces the growth rate of the parametric instability. The growth rate decreases with the frequency of low frequency electromagnetic wave.
Nonlinear temporal modulation of pulsar radioemission
International Nuclear Information System (INIS)
Chian, A.C.-L.
1984-01-01
A nonlinear theory is discussed for self-modulation of pulsar radio pulses. A nonlinear Schroedinger equation is derived for strong electromagnetic waves propagating in an electron-positron plasma. The nonlinearities arising from wave intensity induced relativistic particle mass variation may excite the modulational instability of circularly and linearly polarized pulsar radiation. The resulting wave envelopes can take the form of periodic wave trains or solitons. These nonlinear stationary wave forms may account for the formation of pulsar microstructures. (Author) [pt
DEFF Research Database (Denmark)
Cermak, Daniel; Okutsu, Ayaka; Hasse, Stina
2015-01-01
Electromagnetic Landscape demonstrates in direct, tangible and immediate ways effects of the disruption of the familiar. An ubiquitous technological medium, FM radio, is turned into an alien and unfamiliar one. Audience participation, the environment, radio signals and noise create a site...
Electromagnetic Compatibility of Devices on Hybrid Electromagnetic Components
Konesev, S. G.; Khazieva, R. T.; Kirillov, R. V.; Gainutdinov, I. Z.; Kondratyev, E. Y.
2018-01-01
There is a general tendency to reduce the weight and dimensions, the consumption of conductive and electrical insulating materials, increase the reliability and energy efficiency of electrical devices. In recent years, designers have been actively developing devices based on hybrid electromagnetic components (HEMC) such as inductive-capacitive converters (ICC), voltages pulse generators (VPG), secondary power supplies (SPS), capacitive storage devices (CSD), induction heating systems (IHS). Sources of power supplies of similar electrical devices contain, as a rule, links of increased frequency and function in key (pulse) modes, which leads to an increase in electromagnetic interference (EMI). Nonlinear and periodic (impulse) loads, non-sinusoidal (pulsation) of the electromotive force and nonlinearity of the internal parameters of the source and input circuits of consumers distort the shape of the input voltage lead to an increase in thermal losses from the higher harmonic currents, aging of the insulation, increase in the weight of the power supply filter units, resonance at higher harmonics. The most important task is to analyze the operation of electrotechnical devices based on HEMC from the point of view of creating EMIs and assessing their electromagnetic compatibility (EMC) with power supply systems (PSS). The article presents the results of research on the operation of an IHS, the operation principle of a secondary power supply source of which is based on the operation of a half-bridge autonomous inverter, the switching circuit of which is made in the form of a HEMC, called the «multifunctional integrated electromagnetic component»" (MIEC).
Niessen, E.M.J.; Niessen, E.M.J.; Zandbergen, P.J.
1993-01-01
Analytical results are presented concerning the electromagnetic response of a composite superconducting wire in fields parallel to the wire axis, using the Maxwell equations supplemented with constitutive equations. The problem is nonlinear due to the nonlinearity in the constitutive equation
Nonlinear electrodynamics and cosmology
International Nuclear Information System (INIS)
Breton, Nora
2010-01-01
Nonlinear electrodynamics (NLED) generalizes Maxwell's theory for strong fields. When coupled to general relativity NLED presents interesting features like the non-vanishing of the trace of the energy-momentum tensor that leads to the possibility of violation of some energy conditions and of acting as a repulsive contribution in the Raychaudhuri equation. This theory is worth to study in cosmological and astrophysical situations characterized by strong electromagnetic and gravitational fields.
International Nuclear Information System (INIS)
Tzeng, Wen-Shian V.
1991-01-01
Electromagnetic interference (EMI) shielding materials are well known in the art in forms such as gaskets, caulking compounds, adhesives, coatings and the like for a variety of EMI shielding purposes. In the past, where high shielding performance is necessary, EMI shielding has tended to use silver particles or silver coated copper particles dispersed in a resin binder. More recently, aluminum core silver coated particles have been used to reduce costs while maintaining good electrical and physical properties. (author). 8 figs
Energy Technology Data Exchange (ETDEWEB)
Aldridge, David F.
2014-11-01
A reciprocity theorem is an explicit mathematical relationship between two different wavefields that can exist within the same space - time configuration. Reciprocity theorems provi de the theoretical underpinning for mod ern full waveform inversion solutions, and also suggest practical strategies for speed ing up large - scale numerical modeling of geophysical datasets . In the present work, several previously - developed electromagnetic r eciprocity theorems are generalized to accommodate a broader range of medi um, source , and receiver types. Reciprocity relations enabling the interchange of various types of point sources and point receivers within a three - dimensional electromagnetic model are derived. Two numerical modeling algorithms in current use are successfully tested for adherence to reciprocity. Finally, the reciprocity theorem forms the point of departure for a lengthy derivation of electromagnetic Frechet derivatives. These mathe matical objects quantify the sensitivity of geophysical electromagnetic data to variatio ns in medium parameters, and thus constitute indispensable tools for solution of the full waveform inverse problem. ACKNOWLEDGEMENTS Sandia National Labor atories is a multi - program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the US Department of Energy's National Nuclear Security Administration under contract DE - AC04 - 94AL85000. Signif icant portions of the work reported herein were conducted under a Cooperative Research and Development Agreement (CRADA) between Sandia National Laboratories (SNL) and CARBO Ceramics Incorporated. The author acknowledges Mr. Chad Cannan and Mr. Terry Pa lisch of CARBO Ceramics, and Ms. Amy Halloran, manager of SNL's Geophysics and Atmospheric Sciences Department, for their interest in and encouragement of this work. Special thanks are due to Dr . Lewis C. Bartel ( recently retired from Sandia National Labo ratories
Ida, Nathan
2015-01-01
This book provides students with a thorough theoretical understanding of electromagnetic field equations and it also treats a large number of applications. The text is a comprehensive two-semester textbook. The work treats most topics in two steps – a short, introductory chapter followed by a second chapter with in-depth extensive treatment; between 10 to 30 applications per topic; examples and exercises throughout the book; experiments, problems and summaries. The new edition includes: updated end of chapter problems; a new introduction to electromagnetics based on behavior of charges; a new section on units; MATLAB tools for solution of problems and demonstration of subjects; most chapters include a summary. The book is an undergraduate textbook at the Junior level, intended for required classes in electromagnetics. It is written in simple terms with all details of derivations included and all steps in solutions listed. It requires little beyond basic calculus and can be used for self-study. The weal...
International Nuclear Information System (INIS)
Decyk, Viktor K.
2011-01-01
computational complexity, such as electromagnetic or gyrokinetic codes should perform better. We therefore implemented an 2-1/2D electromagnetic, relativistic code, which used the same algorithms and data structures as the electrostatic code. Typical speedup achieved on the Tesla C1060 was about 40. The Fermi C2050, a newer GPU, achieved a speedup of 55, with a particle processing time of 2.2 nsec/particle/time step. These results were reported at the APS Division of Plasma Physics Meeting and the US-Japan Workshop on Development of Simulation Science in Plasma Physics.
International Nuclear Information System (INIS)
Idomura, Yasuhiro; Jolliet, Sebastien
2010-01-01
A gyrokinetic toroidal five dimensional Eulerian code GT5D is ported on six advanced massively parallel platforms and comprehensive benchmark tests are performed. A parallelisation technique based on physical properties of the gyrokinetic equation is presented. By extending the parallelisation technique with a hybrid parallel model, the scalability of the code is improved on platforms with multi-core processors. In the benchmark tests, a good salability is confirmed up to several thousands cores on every platforms, and the maximum sustained performance of ∼18.6 Tflops is achieved using 16384 cores of BX900. (author)
Energy Technology Data Exchange (ETDEWEB)
McClenaghan, J.; Lin, Z.; Holod, I.; Deng, W.; Wang, Z. [University of California, Irvine, California 92697 (United States)
2014-12-15
The gyrokinetic toroidal code (GTC) capability has been extended for simulating internal kink instability with kinetic effects in toroidal geometry. The global simulation domain covers the magnetic axis, which is necessary for simulating current-driven instabilities. GTC simulation in the fluid limit of the kink modes in cylindrical geometry is verified by benchmarking with a magnetohydrodynamic eigenvalue code. Gyrokinetic simulations of the kink modes in the toroidal geometry find that ion kinetic effects significantly reduce the growth rate even when the banana orbit width is much smaller than the radial width of the perturbed current layer at the mode rational surface.
Finite element approach to global gyrokinetic particle-in-cell simulations using magnetic coordinate
International Nuclear Information System (INIS)
Fivaz, M.; Brunner, S.; Ridder, G. de; Sauter, O.; Tran, T.M.; Vaclavik, J.; Villard, L.; Appert, K.
1997-08-01
We present a fully-global linear gyrokinetic simulation code (GYGLES) aimed at describing the instable spectrum of the ion-temperature-gradient modes in toroidal geometry. We formulate the Particle-In-Cell method with finite elements defined in magnetic coordinates, which provides excellent numerical convergence properties. The poloidal mode structure corresponding to k // =0 is extracted without approximation from the equations, which reduces drastically the numerical resolution needed. The code can simulate routinely modes with both very long and very short toroidal wavelengths, can treat realistic (MHD) equilibria of any size and runs on a massively parallel computer. (author) 10 figs., 28 refs
Development of a global toroidal gyrokinetic Vlasov code with new real space field solver
International Nuclear Information System (INIS)
Obrejan, Kevin; Imadera, Kenji; Li, Ji-Quan; Kishimoto, Yasuaki
2015-01-01
This work introduces a new full-f toroidal gyrokinetic (GK) Vlasov simulation code that uses a real space field solver. This solver enables us to compute the gyro-averaging operators in real space to allow proper treatment of finite Larmor radius (FLR) effects without requiring any particular hypothesis and in any magnetic field configuration (X-point, D-shaped etc). The code was well verified through benchmark tests such as toroidal Ion Temperature Gradient (ITG) instability and collisionless damping of zonal flow. (author)
International Nuclear Information System (INIS)
Ibrahim, Khaled Z.; Madduri, Kamesh; Williams, Samuel; Wang, Bei; Oliker, Leonid
2013-01-01
The Gyrokinetic Toroidal Code (GTC) uses the particle-in-cell method to efficiently simulate plasma microturbulence. This paper presents novel analysis and optimization techniques to enhance the performance of GTC on large-scale machines. We introduce cell access analysis to better manage locality vs. synchronization tradeoffs on CPU and GPU-based architectures. Finally, our optimized hybrid parallel implementation of GTC uses MPI, OpenMP, and NVIDIA CUDA, achieves up to a 2× speedup over the reference Fortran version on multiple parallel systems, and scales efficiently to tens of thousands of cores.
Energy Technology Data Exchange (ETDEWEB)
Besse, Nicolas, E-mail: Nicolas.Besse@oca.eu [Laboratoire J.-L. Lagrange, UMR CNRS/OCA/UCA 7293, Université Côte d’Azur, Observatoire de la Côte d’Azur, Bd de l’Observatoire CS 34229, 06304 Nice Cedex 4 (France); Institut Jean Lamour, UMR CNRS/UL 7198, Université de Lorraine, BP 70239 54506 Vandoeuvre-lès-Nancy Cedex (France); Coulette, David, E-mail: David.Coulette@ipcms.unistra.fr [Institut Jean Lamour, UMR CNRS/UL 7198, Université de Lorraine, BP 70239 54506 Vandoeuvre-lès-Nancy Cedex (France); Institut de Physique et Chimie des Matériaux de Strasbourg, UMR CNRS/US 7504, Université de Strasbourg, 23 Rue du Loess, 67034 Strasbourg (France)
2016-08-15
Achieving plasmas with good stability and confinement properties is a key research goal for magnetic fusion devices. The underlying equations are the Vlasov–Poisson and Vlasov–Maxwell (VPM) equations in three space variables, three velocity variables, and one time variable. Even in those somewhat academic cases where global equilibrium solutions are known, studying their stability requires the analysis of the spectral properties of the linearized operator, a daunting task. We have identified a model, for which not only equilibrium solutions can be constructed, but many of their stability properties are amenable to rigorous analysis. It uses a class of solution to the VPM equations (or to their gyrokinetic approximations) known as waterbag solutions which, in particular, are piecewise constant in phase-space. It also uses, not only the gyrokinetic approximation of fast cyclotronic motion around magnetic field lines, but also an asymptotic approximation regarding the magnetic-field-induced anisotropy: the spatial variation along the field lines is taken much slower than across them. Together, these assumptions result in a drastic reduction in the dimensionality of the linearized problem, which becomes a set of two nested one-dimensional problems: an integral equation in the poloidal variable, followed by a one-dimensional complex Schrödinger equation in the radial variable. We show here that the operator associated to the poloidal variable is meromorphic in the eigenparameter, the pulsation frequency. We also prove that, for all but a countable set of real pulsation frequencies, the operator is compact and thus behaves mostly as a finite-dimensional one. The numerical algorithms based on such ideas have been implemented in a companion paper [D. Coulette and N. Besse, “Numerical resolution of the global eigenvalue problem for gyrokinetic-waterbag model in toroidal geometry” (submitted)] and were found to be surprisingly close to those for the original
Chang, C S; Ku, S; Tynan, G R; Hager, R; Churchill, R M; Cziegler, I; Greenwald, M; Hubbard, A E; Hughes, J W
2017-04-28
Transport barrier formation and its relation to sheared flows in fluids and plasmas are of fundamental interest in various natural and laboratory observations and of critical importance in achieving an economical energy production in a magnetic fusion device. Here we report the first observation of an edge transport barrier formation event in an electrostatic gyrokinetic simulation carried out in a realistic diverted tokamak edge geometry under strong forcing by a high rate of heat deposition. The results show that turbulent Reynolds-stress-driven sheared E×B flows act in concert with neoclassical orbit loss to quench turbulent transport and form a transport barrier just inside the last closed magnetic flux surface.
Effects of the magnetic equilibrium on gyrokinetic simulations of tokamak microinstabilities
Energy Technology Data Exchange (ETDEWEB)
Wan, Weigang; Chen, Yang; Parker, Scott E. [Department of Physics, University of Colorado, Boulder, Colorado 80309 (United States); Groebner, Richard J. [General Atomics, Post Office Box 85068, San Diego, California 92186 (United States)
2015-06-15
The general geometry of the experimental tokamak magnetic equilibrium is implemented in the global gyrokinetic simulation code GEM. Compared to the general geometry, the well used Miller parameterization of the magnetic equilibrium is a good approximation in the core region and up to the top of the pedestal. Linear simulations indicate that results with the two geometries agree for r/a ≤ 0.9. However, in the edge region, the instabilities are sensitive to the magnetic equilibrium in both the L-mode and the H-mode plasmas. A small variation of the plasma shaping parameters leads to large changes to the edge instability.
Gyrokinetic simulations in general geometry and applications to collisional damping of zonal flows
International Nuclear Information System (INIS)
Lin, Z.; Hahm, T.S.; Lee, W.W.; Tang, W.M.; White, R.B.
2000-01-01
A fully three-dimensional gyrokinetic particle code using magnetic coordinates for general geometry has been developed and applied to the investigation of zonal flows dynamics in toroidal ion-temperature-gradient turbulence. Full torus simulation results support the important conclusion that turbulence-driven zonal flows significantly reduce the turbulent transport. Linear collisionless simulations for damping of an initial poloidal flow perturbation exhibit an asymptotic residual flow. The collisional damping of this residual causes the dependence of ion thermal transport on the ion-ion collision frequency even in regimes where the instabilities are collisionless
International Nuclear Information System (INIS)
Burch, Aidan
2004-01-01
Working within the HPO (History Projection Operator) Consistent Histories formalism, we follow the work of Savvidou on (scalar) field theory [J. Math. Phys. 43, 3053 (2002)] and that of Savvidou and Anastopoulos on (first-class) constrained systems [Class. Quantum Gravt. 17, 2463 (2000)] to write a histories theory (both classical and quantum) of Electromagnetism. We focus particularly on the foliation-dependence of the histories phase space/Hilbert space and the action thereon of the two Poincare groups that arise in histories field theory. We quantize in the spirit of the Dirac scheme for constrained systems
Benchmark test of drift-kinetic and gyrokinetic codes through neoclassical transport simulations
International Nuclear Information System (INIS)
Satake, S.; Sugama, H.; Watanabe, T.-H.; Idomura, Yasuhiro
2009-09-01
Two simulation codes that solve the drift-kinetic or gyrokinetic equation in toroidal plasmas are benchmarked by comparing the simulation results of neoclassical transport. The two codes are the drift-kinetic δf Monte Carlo code (FORTEC-3D) and the gyrokinetic full- f Vlasov code (GT5D), both of which solve radially-global, five-dimensional kinetic equation with including the linear Fokker-Planck collision operator. In a tokamak configuration, neoclassical radial heat flux and the force balance relation, which relates the parallel mean flow with radial electric field and temperature gradient, are compared between these two codes, and their results are also compared with the local neoclassical transport theory. It is found that the simulation results of the two codes coincide very well in a wide rage of plasma collisionality parameter ν * = 0.01 - 10 and also agree with the theoretical estimations. The time evolution of radial electric field and particle flux, and the radial profile of the geodesic acoustic mode frequency also coincide very well. These facts guarantee the capability of GT5D to simulate plasma turbulence transport with including proper neoclassical effects of collisional diffusion and equilibrium radial electric field. (author)
International Nuclear Information System (INIS)
Tang, W.M.
2005-01-01
The present lecture provides an introduction to the subject of gyrokinetic theory with applications in the area of magnetic confinement research in plasma physics--the research arena from which this formalism was originally developed. It was presented as a component of the ''Short Course in Kinetic Theory within the Thematic Program in Partial Differential Equations'' held at the Fields Institute for Research in Mathematical Science (24 March 2004). This lecture also discusses the connection between the gyrokinetic formalism and powerful modern numerical simulations. Indeed, simulation, which provides a natural bridge between theory and experiment, is an essential modern tool for understanding complex plasma behavior. Progress has been stimulated in particular by the exponential growth of computer speed along with significant improvements in computer technology. The advances in both particle and fluid simulations of fine-scale turbulence and large-scale dynamics have produced increasingly good agreement between experimental observations and computational modeling. This was enabled by two key factors: (i) innovative advances in analytic and computational methods for developing reduced descriptions of physics phenomena spanning widely disparate temporal and spatial scales and (ii) access to powerful new computational resources
Hakim, Ammar; Shi, Eric; Juno, James; Bernard, Tess; Hammett, Greg
2017-10-01
For weakly collisional (or collisionless) plasmas, kinetic effects are required to capture the physics of micro-turbulence. We have implemented solvers for kinetic and gyrokinetic equations in the computational plasma physics framework, Gkeyll. We use a version of discontinuous Galerkin scheme that conserves energy exactly. Plasma sheaths are modeled with novel boundary conditions. Positivity of distribution functions is maintained via a reconstruction method, allowing robust simulations that continue to conserve energy even with positivity limiters. We have performed a large number of benchmarks, verifying the accuracy and robustness of our code. We demonstrate the application of our algorithm to two classes of problems (a) Vlasov-Maxwell simulations of turbulence in a magnetized plasma, applicable to space plasmas; (b) Gyrokinetic simulations of turbulence in open-field-line geometries, applicable to laboratory plasmas. Supported by the Max-Planck/Princeton Center for Plasma Physics, the SciDAC Center for the Study of Plasma Microturbulence, and DOE Contract DE-AC02-09CH11466.
The spectral problem of global microinstabilities in tokamak-like plasmas using a gyrokinetic model
International Nuclear Information System (INIS)
Brunner, S.; Vaclavik, J.; Fivaz, M.; Appert, K.
1996-01-01
Tokamak-like plasmas are modeled by a periodic cylindrical system with magnetic shear and realistic density and temperature profiles. Linear electrostatic microinstabilities in such plasmas are studied by solving the eigenvalue problem starting from gyrokinetic theory. The actual eigenvalue equation is then of integral type. With this approach, finite Larmor radius (FLR) effects to all orders are taken into account. FLR effects provide for the only radial coupling in a cylinder and to lowest order correspond to polarization drift. This effectively one-dimensional problem helped us to gain useful knowledge for solving gyrokinetic equations in a curved system. When searching for the eigenfrequencies of the global modes, two different methods have been tested and compared. Either the true eigenvalue problem is solved by finding the zeros of the characteristic equation, or one considers a system driven by an antenna and looks for resonances in the power response of the plasma. In addition, mode structures were computed as well in direct as in Fourier space. The advantages and disadvantages of these various approaches are discussed. Ion temperature gradient (ITG) instabilities are studied over a wide range of parameters and for wavelengths perpendicular to the magnetic field down to the scale of ion Larmor radii. Flute instabilities driven by magnetic curvature drifts are also considered. Some of these results are compared with a time evolution PIC code. Such comparisons are valuable as the convergence of PIC results is often questioned. Work considering true toroidal geometry is in progress
Second-order nonlinearity induced transparency.
Zhou, Y H; Zhang, S S; Shen, H Z; Yi, X X
2017-04-01
In analogy to electromagnetically induced transparency, optomechanically induced transparency was proposed recently in [Science330, 1520 (2010)SCIEAS0036-807510.1126/science.1195596]. In this Letter, we demonstrate another form of induced transparency enabled by second-order nonlinearity. A practical application of the second-order nonlinearity induced transparency is to measure the second-order nonlinear coefficient. Our scheme might find applications in quantum optics and quantum information processing.
Classical mechanics and electromagnetism in accelerator physics
Stupakov, Gennady
2018-01-01
This self-contained textbook with exercises discusses a broad range of selected topics from classical mechanics and electromagnetic theory that inform key issues related to modern accelerators. Part I presents fundamentals of the Lagrangian and Hamiltonian formalism for mechanical systems, canonical transformations, action-angle variables, and then linear and nonlinear oscillators. The Hamiltonian for a circular accelerator is used to evaluate the equations of motion, the action, and betatron oscillations in an accelerator. From this base, we explore the impact of field errors and nonlinear resonances. This part ends with the concept of the distribution function and an introduction to the kinetic equation to describe large ensembles of charged particles and to supplement the previous single-particle analysis of beam dynamics. Part II focuses on classical electromagnetism and begins with an analysis of the electromagnetic field from relativistic beams, both in vacuum and in a resistive pipe. Plane electromagne...
Perturbation methods and closure approximations in nonlinear systems
International Nuclear Information System (INIS)
Dubin, D.H.E.
1984-01-01
In the first section of this thesis, Hamiltonian theories of guiding center and gyro-center motion are developed using modern symplectic methods and Lie transformations. Littlejohn's techniques, combined with the theory of resonant interaction and island overlap, are used to explore the problem of adiabatic invariance and onset of stochasticity. As an example, the breakdown of invariance due to resonance between drift motion and gyromotion in a tokamak is considered. A Hamiltonian is developed for motion in a straight magnetic field with electrostatic perturbations in the gyrokinetic ordering, from which nonlinear gyrokinetic equations are constructed which have the property of phase-space preservation, useful for computer simulation. Energy invariants are found and various limits of the equations are considered. In the second section, statistical closure theories are applied to simple dynamical systems. The logistic map is used as an example because of its universal properties and simple quadratic nonlinearity. The first closure considered is the direct interaction approximation of Kraichnan, which is found to fail when applied to the logistic map because it cannot approximate the bounded support of the map's equilibrium distribution. By imposing a periodically constraint on a Langevin form of the DIA a new stable closure is developed
Nonlinear diffuse scattering of the random-phased wave
International Nuclear Information System (INIS)
Kato, Yoshiaki; Arinaga, Shinji; Mima, Kunioki.
1983-01-01
First experimental observation of the nonlinear diffuse scattering is reported. This new effect was observed in the propagation of the random-phased wave through a nonlinear dielectric medium. This effect is ascribed to the diffusion of the wavevector of the electro-magnetic wave to the lateral direction due to the randomly distributed nonlinear increase in the refractive index. (author)
Electromagnetic topology: Characterization of internal electromagnetic coupling
Parmantier, J. P.; Aparicio, J. P.; Faure, F.
1991-01-01
The main principles are presented of a method dealing with the resolution of electromagnetic internal problems: Electromagnetic Topology. A very interesting way is to generalize the multiconductor transmission line network theory to the basic equation of the Electromagnetic Topology: the BLT equation. This generalization is illustrated by the treatment of an aperture as a four port junction. Analytical and experimental derivations of the scattering parameters are presented. These concepts are used to study the electromagnetic coupling in a scale model of an aircraft, and can be seen as a convenient means to test internal electromagnetic interference.
Electromagnetically shielded building
International Nuclear Information System (INIS)
Takahashi, T.; Nakamura, M.; Yabana, Y.; Ishikawa, T.; Nagata, K.
1992-01-01
This invention relates to a building having an electromagnetic shield structure well-suited for application to an information network system utilizing electromagnetic waves, and more particularly to an electromagnetically shielded building for enhancing the electromagnetic shielding performance of an external wall. 6 figs
Electromagnetically shielded building
Energy Technology Data Exchange (ETDEWEB)
Takahashi, T; Nakamura, M; Yabana, Y; Ishikawa, T; Nagata, K
1992-04-21
This invention relates to a building having an electromagnetic shield structure well-suited for application to an information network system utilizing electromagnetic waves, and more particularly to an electromagnetically shielded building for enhancing the electromagnetic shielding performance of an external wall. 6 figs.
Dynamics and Control of a Chaotic Electromagnetic System
Shun-Chang Chang
2012-01-01
In this paper, different nonlinear dynamics analysis techniques are employed to unveil the rich nonlinear phenomena of the electromagnetic system. In particular, bifurcation diagrams, time responses, phase portraits, Poincare maps, power spectrum analysis, and the construction of basins of attraction are all powerful and effective tools for nonlinear dynamics problems. We also employ the method of Lyapunov exponents to show the occurrence of chaotic motion and to verify those numerical simula...
Kolm, H.; Mongeau, P.; Williams, F.
1980-09-01
Recent advances in energy storage, switching and magnet technology make electromagnetic acceleration a viable alternative to chemical propulsion for certain tasks, and a means to perform other tasks not previously feasible. Applications include the acceleration of gram-size particles for hypervelocity research and the initiation of fusion by impact, a replacement for chemically propelled artillery, the transportation of cargo and personnel over inaccessible terrain, and the launching of space vehicles to supply massive space operations, and for the disposal of nuclear waste. The simplest launcher of interest is the railgun, in which a short-circuit slide or an arc is driven along two rails by direct current. The most sophisticated studied thus far is the mass driver, in which a superconducting shuttle bucket is accelerated by a line of pulse coils energized by capacitors at energy conversion efficiencies better than 90%. Other accelerators of interest include helical, brush-commutated motors, discrete coil arc commutated drivers, flux compression momentum transformers, and various hybrid electrochemical devices.
Continuum mechanics of electromagnetic solids
Maugin, GA
1988-01-01
This volume is a rigorous cross-disciplinary theoretical treatment of electromechanical and magnetomechanical interactions in elastic solids. Using the modern style of continuum thermomechanics (but without excessive formalism) it starts from basic principles of mechanics and electromagnetism, and goes on to unify these two fields in a common framework. It treats linear and nonlinear static and dynamic problems in a variety of elastic solids such as piezoelectrics, electricity conductors, ferromagnets, ferroelectrics, ionic crystals and ceramics. Chapters 1-3 are introductory, describing the e
Electromagnetic weak turbulence theory revisited
Energy Technology Data Exchange (ETDEWEB)
Yoon, P. H. [IPST, University of Maryland, College Park, Maryland 20742 (United States); Ziebell, L. F. [Instituto de Fisica, UFRGS, Porto Alegre, RS (Brazil); Gaelzer, R.; Pavan, J. [Instituto de Fisica e Matematica, UFPel, Pelotas, RS (Brazil)
2012-10-15
The statistical mechanical reformulation of weak turbulence theory for unmagnetized plasmas including fully electromagnetic effects was carried out by Yoon [Phys. Plasmas 13, 022302 (2006)]. However, the wave kinetic equation for the transverse wave ignores the nonlinear three-wave interaction that involves two transverse waves and a Langmuir wave, the incoherent analogue of the so-called Raman scattering process, which may account for the third and higher-harmonic plasma emissions. The present paper extends the previous formalism by including such a term.
Topological Foundations of Electromagnetism
Barrett, Terrence W
2008-01-01
Topological Foundations of Electromagnetism seeks a fundamental understanding of the dynamics of electromagnetism; and marshals the evidence that in certain precisely defined topological conditions, electromagnetic theory (Maxwell's theory) must be extended or generalized in order to provide an explanation and understanding of, until now, unusual electromagnetic phenomena. Key to this generalization is an understanding of the circumstances under which the so-called A potential fields have physical effects. Basic to the approach taken is that the topological composition of electromagnetic field
Recent advances in gyrokinetic full-f particle simulation of medium sized Tokamaks with ELMFIRE
International Nuclear Information System (INIS)
Janhunen, S.J.; Kiviniemi, T.P.; Korpio, T.; Leerink, S.; Nora, M.; Heikkinen, J.A.; Ogando, F.
2010-01-01
Large-scale kinetic simulations of toroidal plasmas based on first principles are called for in studies of transition from low to high confinement mode and internal transport barrier formation in the core plasma. Such processes are best observed and diagnosed in detached plasma conditions in mid-sized tokamaks, so gyrokinetic simulations for these conditions are warranted. A first principles test-particle based kinetic model ELMFIRE[1] has been developed and used in interpretation[1,2] of FT-2 and DIII-D experiments. In this work we summarize progress in Cyclone (DIII-D core) and ASDEX Upgrade pedestal region simulations, and show that in simulations the choice of adiabatic electrons results in quenching of turbulence (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Parker, Jeffrey; Lodestro, Lynda; Told, Daniel; Merlo, Gabriele; Ricketson, Lee; Campos, Alejandro; Jenko, Frank; Hittinger, Jeffrey
2017-10-01
Predictive whole-device simulation models will play an increasingly important role in ensuring the success of fusion experiments and accelerating the development of fusion energy. In the core of tokamak plasmas, a separation of timescales between turbulence and transport makes a single direct simulation of both processes computationally expensive. We present the first demonstration of a multiple-timescale method coupling global gyrokinetic simulations with a transport solver to calculate the self-consistent, steady-state temperature profile. Initial results are highly encouraging, with the coupling method appearing robust to the difficult problem of turbulent fluctuations. The method holds potential for integrating first-principles turbulence simulations into whole-device models and advancing the understanding of global plasma behavior. Work supported by US DOE under Contract DE-AC52-07NA27344 and the Exascale Computing Project (17-SC-20-SC).
Grid-based Parallel Data Streaming Implemented for the Gyrokinetic Toroidal Code
International Nuclear Information System (INIS)
Klasky, S.; Ethier, S.; Lin, Z.; Martins, K.; McCune, D.; Samtaney, R.
2003-01-01
We have developed a threaded parallel data streaming approach using Globus to transfer multi-terabyte simulation data from a remote supercomputer to the scientist's home analysis/visualization cluster, as the simulation executes, with negligible overhead. Data transfer experiments show that this concurrent data transfer approach is more favorable compared with writing to local disk and then transferring this data to be post-processed. The present approach is conducive to using the grid to pipeline the simulation with post-processing and visualization. We have applied this method to the Gyrokinetic Toroidal Code (GTC), a 3-dimensional particle-in-cell code used to study microturbulence in magnetic confinement fusion from first principles plasma theory
Gyrokinetic Calculations of Microturbulence and Transport for NSTX and Alcator-CMOD H-modes
International Nuclear Information System (INIS)
Redi, M.H.; Dorland, W.; Bell, R.; Bonoli, P.; Bourdelle, C.; Candy, J.; Ernst, D.; Fiore, C.; Gates, D.; Hammett, G.; Hill, K.; Kaye, S.; LeBlanc, B.; Menard, J.; Mikkelsen, D.; Rewoldt, G.; Rice, J.; Waltz, R.; Wukitch, S.
2003-01-01
Recent H-mode experiments on NSTX [National Spherical Torus Experiment] and experiments on Alcator-CMOD, which also exhibit internal transport barriers (ITB), have been examined with gyrokinetic simulations with the GS2 and GYRO codes to identify the underlying key plasma parameters for control of plasma performance and, ultimately, the successful operation of future reactors such as ITER [International Thermonuclear Experimental Reactor]. On NSTX the H-mode is characterized by remarkably good ion confinement and electron temperature profiles highly resilient in time. On CMOD, an ITB with a very steep electron density profile develops following off-axis radio-frequency heating and establishment of H-mode. Both experiments exhibit ion thermal confinement at the neoclassical level. Electron confinement is also good in the CMOD core
Recent advances in gyrokinetic full-f particle simulation of medium sized Tokamaks with ELMFIRE
Energy Technology Data Exchange (ETDEWEB)
Janhunen, S.J.; Kiviniemi, T.P.; Korpio, T.; Leerink, S.; Nora, M. [Helsinki University of Technology, Euratom-Tekes Association, Espoo (Finland); Heikkinen, J.A. [VTT, Euratom-Tekes Association, Espoo (Finland); Ogando, F. [Helsinki University of Technology, Euratom-Tekes Association, Espoo (Finland); Universidad Nacional de Educacion a Distancia, Madrid (Spain)
2010-05-15
Large-scale kinetic simulations of toroidal plasmas based on first principles are called for in studies of transition from low to high confinement mode and internal transport barrier formation in the core plasma. Such processes are best observed and diagnosed in detached plasma conditions in mid-sized tokamaks, so gyrokinetic simulations for these conditions are warranted. A first principles test-particle based kinetic model ELMFIRE[1] has been developed and used in interpretation[1,2] of FT-2 and DIII-D experiments. In this work we summarize progress in Cyclone (DIII-D core) and ASDEX Upgrade pedestal region simulations, and show that in simulations the choice of adiabatic electrons results in quenching of turbulence (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Managing locality in grand challenge applications: a case study of the gyrokinetic toroidal code
Energy Technology Data Exchange (ETDEWEB)
Marin, G; Jin, G; Mellor-Crummey, J [Department of Computer Science, Rice University, Houston, TX 77005 (United States)
2008-07-15
Achieving high performance with grand challenge applications on today's large-scale parallel systems requires tailoring applications for the characteristics of the modern microprocessor architectures. As part of the US Department of Energy's Scientific Discovery through Advanced Computing (SciDAC) program, we studied and tuned the Gyrokinetic Toroidal Code (GTC), a particle-in-cell code for simulating turbulent transport of particles and energy in burning plasma, developed at Princeton Plasma Physics Laboratory. In this paper, we present a performance study of the application that revealed several opportunities for improving performance by enhancing its data locality. We tuned GTC by performing three kinds of transformations: static data structure reorganization to improve spatial locality, loop nest restructuring for better temporal locality, and dynamic data reordering at run-time to enhance both spatial and temporal reuse. Experimental results show that these changes improve execution time by more than 20% on large parallel systems, including a Cray XT4.
A Systematic Method for Verification and Validation of Gyrokinetic Microstability Codes
Energy Technology Data Exchange (ETDEWEB)
Bravenec, Ronald [Fourth State Research, Austin, TX (United States)
2017-11-14
My original proposal for the period Feb. 15, 2014 through Feb. 14, 2017 called for an integrated validation and verification effort carried out by myself with collaborators. The validation component would require experimental profile and power-balance analysis. In addition, it would require running the gyrokinetic codes varying the input profiles within experimental uncertainties to seek agreement with experiment before discounting a code as invalidated. Therefore, validation would require a major increase of effort over my previous grant periods which covered only code verification (code benchmarking). Consequently, I had requested full-time funding. Instead, I am being funded at somewhat less than half time (5 calendar months per year). As a consequence, I decided to forego the validation component and to only continue the verification efforts.
Gyrokinetic analysis of linear microinstabilities for the stellarator Wendelstein 7-X
Xanthopoulos, P.; Jenko, F.
2007-04-01
A linear collisionless gyrokinetic investigation of ion temperature gradient (ITG) modes—considering both adiabatic and full electron dynamics—and trapped electron modes (TEMs) is presented for the stellarator Wendelstein 7-X (W7-X) [G. Grieger et al., Plasma Physics and Controlled Nuclear Fusion Research 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. 3, p. 525]. The study of ITG modes reveals that in W7-X, microinstabilities of distinct character coexist. The effect of changes in the density gradient and temperature ratio is discussed. Substantial differences with respect to the axisymmetric geometry appear in W7-X, concerning the relative separation of regions with a large fraction of helically trapped particles and those of pronounced bad curvature. For both ITG modes and TEMs, the dependence of their linear growth rates on the background gradients is studied along with their parallel mode structure.
A comprehensive gyrokinetic description of global electrostatic microinstabilities in a tokamak
Chowdhury, J.; Ganesh, R.; Brunner, S.; Vaclavik, J.; Villard, L.; Angelino, P.
2009-05-01
It is believed that low frequency microinstabilities such as ion temperature gradient (ITG) driven modes and trapped electron modes (TEMs) are largely responsible for the experimentally observed anomalous transport via the ion and electron channels in a tokamak. In the present work, a comprehensive global linear gyrokinetic model incorporating fully kinetic (trapped and passing) electrons and ions, actual ion to electron mass ratio, radial coupling, and profile variation is used to investigate the ITG driven modes and pure TEMs. These modes are found to exhibit multiscale structures in the presence of nonadiabatic passing electrons. The multiscale structure is related to the large nonadiabaticity of electrons in the vicinity of mode rational magnetic surfaces and leads to reduced mixing length estimates of transport compared to those obtained from adiabatic electron models.
Managing locality in grand challenge applications: a case study of the gyrokinetic toroidal code
International Nuclear Information System (INIS)
Marin, G; Jin, G; Mellor-Crummey, J
2008-01-01
Achieving high performance with grand challenge applications on today's large-scale parallel systems requires tailoring applications for the characteristics of the modern microprocessor architectures. As part of the US Department of Energy's Scientific Discovery through Advanced Computing (SciDAC) program, we studied and tuned the Gyrokinetic Toroidal Code (GTC), a particle-in-cell code for simulating turbulent transport of particles and energy in burning plasma, developed at Princeton Plasma Physics Laboratory. In this paper, we present a performance study of the application that revealed several opportunities for improving performance by enhancing its data locality. We tuned GTC by performing three kinds of transformations: static data structure reorganization to improve spatial locality, loop nest restructuring for better temporal locality, and dynamic data reordering at run-time to enhance both spatial and temporal reuse. Experimental results show that these changes improve execution time by more than 20% on large parallel systems, including a Cray XT4
Gyrokinetic Vlasov code including full three-dimensional geometry of experiments
International Nuclear Information System (INIS)
Nunami, Masanori; Watanabe, Tomohiko; Sugama, Hideo
2010-03-01
A new gyrokinetic Vlasov simulation code, GKV-X, is developed for investigating the turbulent transport in magnetic confinement devices with non-axisymmetric configurations. Effects of the magnetic surface shapes in a three-dimensional equilibrium obtained from the VMEC code are accurately incorporated. Linear simulations of the ion temperature gradient instabilities and the zonal flows in the Large Helical Device (LHD) configuration are carried out by the GKV-X code for a benchmark test against the GKV code. The frequency, the growth rate, and the mode structure of the ion temperature gradient instability are influenced by the VMEC geometrical data such as the metric tensor components of the Boozer coordinates for high poloidal wave numbers, while the difference between the zonal flow responses obtained by the GKV and GKV-X codes is found to be small in the core LHD region. (author)
Gyrokinetic modelling of the quasilinear particle flux for plasmas with neutral-beam fuelling
Narita, E.; Honda, M.; Nakata, M.; Yoshida, M.; Takenaga, H.; Hayashi, N.
2018-02-01
A quasilinear particle flux is modelled based on gyrokinetic calculations. The particle flux is estimated by determining factors, namely, coefficients of off-diagonal terms and a particle diffusivity. In this paper, the methodology to estimate the factors is presented using a subset of JT-60U plasmas. First, the coefficients of off-diagonal terms are estimated by linear gyrokinetic calculations. Next, to obtain the particle diffusivity, a semi-empirical approach is taken. Most experimental analyses for particle transport have assumed that turbulent particle fluxes are zero in the core region. On the other hand, even in the stationary state, the plasmas in question have a finite turbulent particle flux due to neutral-beam fuelling. By combining estimates of the experimental turbulent particle flux and the coefficients of off-diagonal terms calculated earlier, the particle diffusivity is obtained. The particle diffusivity should reflect a saturation amplitude of instabilities. The particle diffusivity is investigated in terms of the effects of the linear instability and linear zonal flow response, and it is found that a formula including these effects roughly reproduces the particle diffusivity. The developed framework for prediction of the particle flux is flexible to add terms neglected in the current model. The methodology to estimate the quasilinear particle flux requires so low computational cost that a database consisting of the resultant coefficients of off-diagonal terms and particle diffusivity can be constructed to train a neural network. The development of the methodology is the first step towards a neural-network-based particle transport model for fast prediction of the particle flux.
International Nuclear Information System (INIS)
Boyd, R.W.
1992-01-01
Nonlinear optics is the study of the interaction of intense laser light with matter. This book is a textbook on nonlinear optics at the level of a beginning graduate student. The intent of the book is to provide an introduction to the field of nonlinear optics that stresses fundamental concepts and that enables the student to go on to perform independent research in this field. This book covers the areas of nonlinear optics, quantum optics, quantum electronics, laser physics, electrooptics, and modern optics
Electromagnetic wave collapse in a radiation background
International Nuclear Information System (INIS)
Marklund, Mattias; Brodin, Gert; Stenflo, Lennart
2003-01-01
The nonlinear interaction, due to quantum electrodynamical (QED) effects between an electromagnetic pulse and a radiation background, is investigated by combining the methods of radiation hydrodynamics with the QED theory for photon-photon scattering. For the case of a single coherent electromagnetic pulse, we obtain a Zakharov-like system, where the radiation pressure of the pulse acts as a driver of acoustic waves in the photon gas. For a sufficiently intense pulse and/or background energy density, there is focusing and the subsequent collapse of the pulse. The relevance of our results for various astrophysical applications are discussed
Progress of electromagnetic analysis for fusion reactors
International Nuclear Information System (INIS)
Takagi, T.; Ruatto, P.; Boccaccini, L.V.
1998-01-01
This paper describes the recent progress of electromagnetic analysis research for fusion reactors including methods, codes, verification tests and some applications. Due to the necessity of the research effort for the structural design of large tokamak devices since the 1970's with the help of the introduction of new numerical methods and the advancement of computer technologies, three-dimensional analysis methods have become as practical as shell approximation methods. The electromagnetic analysis is now applied to the structural design of new fusion reactors. Some more modeling and verification tests are necessary when the codes are applied to new materials with nonlinear material properties. (orig.)
Electromagnetically Induced Transparency In Rydberg Atomic Medium
Deng, Li; Cong, Lu; Chen, Ai-Xi
2018-03-01
Due to possessing big principal quantum number, Rydberg atom has some unique properties, for example: its radiative lifetime is long, dipole moment is large, and interaction between atoms is strong and so on. These properties make one pay attention to Rydberg atoms. In this paper we investigate the effects of Rydberg dipole-dipole interactions on electromagnetically induced transparency (EIT) schemes and group velocity in three-level systems of ladder type, which provides theoretical foundation for exploring the linear and nonlinear characteristics of light in a Rydberg electromagnetically-induced-transparency medium.
Nonlinear coupled Alfven and gravitational waves
International Nuclear Information System (INIS)
Kaellberg, Andreas; Brodin, Gert; Bradley, Michael
2004-01-01
In this paper we consider nonlinear interaction between gravitational and electromagnetic waves in a strongly magnetized plasma. More specifically, we investigate the propagation of gravitational waves with the direction of propagation perpendicular to a background magnetic field and the coupling to compressional Alfven waves. The gravitational waves are considered in the high-frequency limit and the plasma is modeled by a multifluid description. We make a self-consistent, weakly nonlinear analysis of the Einstein-Maxwell system and derive a wave equation for the coupled gravitational and electromagnetic wave modes. A WKB-approximation is then applied and as a result we obtain the nonlinear Schroedinger equation for the slowly varying wave amplitudes. The analysis is extended to 3D wave pulses, and we discuss the applications to radiation generated from pulsar binary mergers. It turns out that the electromagnetic radiation from a binary merger should experience a focusing effect, that in principle could be detected
Kim, Kyuho; Kwon, Jae-Min; Chang, C. S.; Seo, Janghoon; Ku, S.; Choe, W.
2017-06-01
Flux-driven full-f gyrokinetic simulations are performed to study carbon impurity effects on the ion temperature gradient (ITG) turbulence and ion thermal transport in a toroidal geometry. Employing the full-f gyrokinetic code XGC1, both main ions and impurities are evolved self-consistently including turbulence and neoclassical physics. It is found that the carbon impurity profile self-organizes to form an inwardly peaked density profile, which weakens the ITG instabilities and reduces the overall fluctuations and ion thermal transport. A stronger reduction appears in the low frequency components of the fluctuations. The global structure of E × B flow also changes, resulting in the reduction of global avalanche like transport events in the impure plasma. Detailed properties of impurity transport are also studied, and it is revealed that both the inward neoclassical pinch and the outward turbulent transport are equally important in the formation of the steady state impurity profile.
Extreme Nonlinear Optics An Introduction
Wegener, Martin
2005-01-01
Following the birth of the laser in 1960, the field of "nonlinear optics" rapidly emerged. Today, laser intensities and pulse durations are readily available, for which the concepts and approximations of traditional nonlinear optics no longer apply. In this regime of "extreme nonlinear optics," a large variety of novel and unusual effects arise, for example frequency doubling in inversion symmetric materials or high-harmonic generation in gases, which can lead to attosecond electromagnetic pulses or pulse trains. Other examples of "extreme nonlinear optics" cover diverse areas such as solid-state physics, atomic physics, relativistic free electrons in a vacuum and even the vacuum itself. This book starts with an introduction to the field based primarily on extensions of two famous textbook examples, namely the Lorentz oscillator model and the Drude model. Here the level of sophistication should be accessible to any undergraduate physics student. Many graphical illustrations and examples are given. The followi...
Bloembergen, Nicolaas
1996-01-01
Nicolaas Bloembergen, recipient of the Nobel Prize for Physics (1981), wrote Nonlinear Optics in 1964, when the field of nonlinear optics was only three years old. The available literature has since grown by at least three orders of magnitude.The vitality of Nonlinear Optics is evident from the still-growing number of scientists and engineers engaged in the study of new nonlinear phenomena and in the development of new nonlinear devices in the field of opto-electronics. This monograph should be helpful in providing a historical introduction and a general background of basic ideas both for expe
Nonlinear generation of the fundamental radiation in plasmas
International Nuclear Information System (INIS)
Chian, A.C.L.; Rizzato, F.B.
1993-01-01
Nonlinear generation of coherent electromagnetic radiation by intense Langmuir waves in the vicinity of the fundamental plasma frequency f p is of current interest in space and laboratory plasmas. In a pioneer work, Lashmore-Davies demonstrated that an efficient process for converting intense Langmuir waves into f p electromagnetic radiation can be achieved by two counterstreaming Langmuir pump waves through an electromagnetic oscillating two-stream instability. Recently Chian and Alves, Akimoto and Rizzato and Chian extended the formalism of Lashmore-Davies in order to include mixed processes with induced modes which are purely electrostatic or electromagnetic. In this paper we extend our previous analysis, in order to study the nonlinear interaction involving travelling electromagnetic pumps, low-frequency density fluctuations and high-frequency f p modes which can be electrostatic-electromagnetic hybrids. (author) 5 refs., 2 figs
International Nuclear Information System (INIS)
Lashmore-Davies, C.N.; Fuchs, V.; Dendy, R.O.
1993-01-01
A full-wave equation has been obtained from the gyrokinetic theory for the fast wave traversing a minority cyclotron resonance [Phys. Fluids B 4, 493 (1992)] with the aid of the fast wave approximation [Phys. Fluids 31, 1614 (1988)]. This theory describes the transmission, reflection, and absorption of the fast wave for arbitrary values of the parallel wave number. For oblique propagation the absorption is due to both ion cyclotron damping by minority ions and mode conversion to the ion Bernstein wave. The results for a 3 He minority in a D plasma indicate that for perpendicular propagation and minority temperatures of a few keV the power lost by the fast wave is all mode converted whereas for minority temperatures ∼100 keV∼30% of the incident power is dissipated by the minority ions due to the gyrokinetic correction. The gyrokinetic correction also results in a significant reduction in the reflection coefficient for low field side incidence when k zLB approx-lt 1 and the minority and hybrid resonances overlap
Nonlinear phenomena at cyclotron resonance
International Nuclear Information System (INIS)
Subbarao, D.; Uma, R.
1986-01-01
Finite amplitude electromagnetic waves in a magnetoplasma which typically occur in situations as in present day wave heating, current drives and other schemes in magnetically confined fusion systems, can show qualitatively different absorption and emission characteristics around resonant frequencies of the plasma because of anharmonicity. Linear wave plasma coupling as well as weak nonlinear effects such as parametric instabilities generally overlook this important effect even though the thresholds for the two phenomena as shown here are comparable. Though the effects described here are relevant to a host of nonlinear resonance effects in fusion plasmas, the authors mainly limit themselves to ECRH
Large amplitude parallel propagating electromagnetic oscillitons
International Nuclear Information System (INIS)
Cattaert, Tom; Verheest, Frank
2005-01-01
Earlier systematic nonlinear treatments of parallel propagating electromagnetic waves have been given within a fluid dynamic approach, in a frame where the nonlinear structures are stationary and various constraining first integrals can be obtained. This has lead to the concept of oscillitons that has found application in various space plasmas. The present paper differs in three main aspects from the previous studies: first, the invariants are derived in the plasma frame, as customary in the Sagdeev method, thus retaining in Maxwell's equations all possible effects. Second, a single differential equation is obtained for the parallel fluid velocity, in a form reminiscent of the Sagdeev integrals, hence allowing a fully nonlinear discussion of the oscilliton properties, at such amplitudes as the underlying Mach number restrictions allow. Third, the transition to weakly nonlinear whistler oscillitons is done in an analytical rather than a numerical fashion
Intermediate energy electromagnetic interactions
International Nuclear Information System (INIS)
Garcon, M.
1994-11-01
Polarization measurements in electromagnetic interactions are reviewed. Deep inelastic scattering of polarized electrons and muons an polarized targets, photoproduction of pseudoscalar mesons on protons, photonuclear reactions, and the electromagnetic structure of the deuteron are discussed. (K.A.)
Intermediate energy electromagnetic interactions
Energy Technology Data Exchange (ETDEWEB)
Garcon, M.
1994-11-01
Polarization measurements in electromagnetic interactions are reviewed. Deep inelastic scattering of polarized electrons and muons an polarized targets, photoproduction of pseudoscalar mesons on protons, photonuclear reactions, and the electromagnetic structure of the deuteron are discussed. (K.A.).
Electromagnetic wave matching device
International Nuclear Information System (INIS)
Hirata, Yosuke; Mitsunaka, Yoshika; Hayashi, Ken-ichi; Ito, Yasuyuki.
1997-01-01
The present invention provides an electromagnetic wave matching capable of reducing a cost for the transmission system in a system of using electromagnetic waves for plasma heating of a thermonuclear reactor. Namely, incident electromagnetic waves are reflected by using a plurality of phase correction mirrors. The reflected electromagnetic waves are connected to an external transmission system through an exit. The phase correction mirrors have such a shape to receive a plurality of beam-like electromagnetic waves and output electromagnetic waves by the number different from the number of the received electromagnetic wave beams having a predetermined distribution. Further, at least two of the phase correction mirrors have such a shape to change the phase of the electromagnetic waves beams incident to the reflection surface of the phase correction mirrors by a predetermined amount corresponding to the position of the reflection surface. Then, the cost for transmission system can greatly be reduced. (I.S.)
Probing nonlinear electrodynamics in slowly rotating spacetimes through neutrino astrophysics
Cuesta, Herman J. Mosquera; Lambiase, Gaetano; Pereira, Jonas P.
2017-01-01
Huge electromagnetic fields are known to be present during the late stages of the dynamics of supernovae. Thus, when dealing with electrodynamics in this context, the possibility may arise to probe nonlinear theories (generalizations of the Maxwellian electromagnetism). We firstly solve Einstein field equations minimally coupled to an arbitrary (current-free) nonlinear Lagrangian of electrodynamics (NLED) in the slow rotation regime $a\\ll M$ (black hole's mass), up to first order in $a/M$. We...
Electromagnetic Education in India
Bajpai, Shrish; Asif, Siddiqui Sajida; Akhtar, Syed Adnan
2016-01-01
Out of the four fundamental interactions in nature, electromagnetics is one of them along with gravitation, strong interaction and weak interaction. The field of electromagnetics has made much of the modern age possible. Electromagnets are common in day-to-day appliances and are becoming more conventional as the need for technology increases.…
Electronic circuit for control rod attracting electromagnet
International Nuclear Information System (INIS)
Ito, Koji.
1991-01-01
The present invention provides a discharging circuit for control rod attracting electromagnet used for a reactor which is highly reliable and has high performance. The resistor of the circuit comprises a non-linear resistor element and a blocking rectification element connected in series. The discharging circuit can be prevented from short-circuit by selecting a resistor having a resistance value about ten times as great as the coil resistance, even in a case where the blocking rectification element and the non-linear resistor element are failed. Accordingly, reduction of attracting force and the increase of scream releasing time can be minimized. (I.S.)
Electromagnetic fields with vanishing quantum corrections
Ortaggio, Marcello; Pravda, Vojtěch
2018-04-01
We show that a large class of null electromagnetic fields are immune to any modifications of Maxwell's equations in the form of arbitrary powers and derivatives of the field strength. These are thus exact solutions to virtually any generalized classical electrodynamics containing both non-linear terms and higher derivatives, including, e.g., non-linear electrodynamics as well as QED- and string-motivated effective theories. This result holds not only in a flat or (anti-)de Sitter background, but also in a larger subset of Kundt spacetimes, which allow for the presence of aligned gravitational waves and pure radiation.
Metamaterial Electromagnetic Superabsorber with Arbitrary Geometries
Directory of Open Access Journals (Sweden)
Jingjing Yang
2010-06-01
Full Text Available The electromagnetic superabsorber that has larger absorption cross section than its real size may be a novel photothermal device with improved solar energy conversion rates. Based on a transformation optical approach, the material parameters for a two-dimensional (2D metamaterial-assisted electromagnetic superabsorber with arbitrary geometries are derived and validated by numerical simulation. We find that for the given geometry size, the absorption cross section of the superabsorber using nonlinear transformation is larger than that using linear transformation. These transformations can also be specialized to the designing the N-sided regular polygonal superabsorber just by changing the contour equation. All theoretical and numerical results validate the material parameters for the 2D electromagnetic superabsorber we have developed.
Multiscale gyrokinetics for rotating tokamak plasmas: fluctuations, transport and energy flows.
Abel, I G; Plunk, G G; Wang, E; Barnes, M; Cowley, S C; Dorland, W; Schekochihin, A A
2013-11-01
This paper presents a complete theoretical framework for studying turbulence and transport in rapidly rotating tokamak plasmas. The fundamental scale separations present in plasma turbulence are codified as an asymptotic expansion in the ratio ε = ρi/α of the gyroradius to the equilibrium scale length. Proceeding order by order in this expansion, a set of coupled multiscale equations is developed. They describe an instantaneous equilibrium, the fluctuations driven by gradients in the equilibrium quantities, and the transport-timescale evolution of mean profiles of these quantities driven by the interplay between the equilibrium and the fluctuations. The equilibrium distribution functions are local Maxwellians with each flux surface rotating toroidally as a rigid body. The magnetic equilibrium is obtained from the generalized Grad-Shafranov equation for a rotating plasma, determining the magnetic flux function from the mean pressure and velocity profiles of the plasma. The slow (resistive-timescale) evolution of the magnetic field is given by an evolution equation for the safety factor q. Large-scale deviations of the distribution function from a Maxwellian are given by neoclassical theory. The fluctuations are determined by the 'high-flow' gyrokinetic equation, from which we derive the governing principle for gyrokinetic turbulence in tokamaks: the conservation and local (in space) cascade of the free energy of the fluctuations (i.e. there is no turbulence spreading). Transport equations for the evolution of the mean density, temperature and flow velocity profiles are derived. These transport equations show how the neoclassical and fluctuating corrections to the equilibrium Maxwellian act back upon the mean profiles through fluxes and heating. The energy and entropy conservation laws for the mean profiles are derived from the transport equations. Total energy, thermal, kinetic and magnetic, is conserved and there is no net turbulent heating. Entropy is produced
Center for Gyrokinetic Particle Simulation of Turbulent Transport in Burning Plasma
International Nuclear Information System (INIS)
Decyk, Viktor K.
2008-01-01
The UCLA work on this grant was to design and help implement an object-oriented version of the GTC code, which is written in Fortran90. The GTC code is the main global gyrokinetic code used in this project, and over the years multiple, incompatible versions have evolved. The reason for this effort is to allow multiple authors to work together on GTC and to simplify future enhancements to GTC. The effort was designed to proceed incrementally. Initially, an upper layer of classes (derived types and methods) was implemented which called the original GTC code 'under the hood.' The derived types pointed to data in the original GTC code, and the methods called the original GTC subroutines. The original GTC code was modified only very slightly. This allowed one to define (and refine) a set of classes which described the important features of the GTC code in a new, more abstract way, with a minimum of implementation. Furthermore, classes could be added one at a time, and at the end of the each day, the code continued to work correctly. This work was done in close collaboration with Y. Nishimura from UC Irvine and Stefan Ethier from PPPL. Ten classes were ultimately defined and implemented: gyrokinetic and drift kinetic particles, scalar and vector fields, a mesh, jacobian, FLR, equilibrium, interpolation, and particles species descriptors. In the second state of this development, some of the scaffolding was removed. The constructors in the class objects now allocated the data and the array data in the original GTC code was removed. This isolated the components and now allowed multiple instantiations of the objects to be created, in particular, multiple ion species. Again, the work was done incrementally, one class at a time, so that the code was always working properly. This work was done in close collaboration with Y. Nishimura and W. Zhang from UC Irvine and Stefan Ethier from PPPL. The third stage of this work was to integrate the capabilities of the various versions of
Large time asymptotics of solutions to the anharmonic oscillator model from nonlinear optics
Jochmann, Frank
2005-01-01
The anharmonic oscillator model describing the propagation of electromagnetic waves in an exterior domain containing a nonlinear dielectric medium is investigated. The system under consideration consists of a generally nonlinear second order differential equation for the dielectrical polarization coupled with Maxwell's equations for the electromagnetic field. Local decay of the electromagnetic field for t to infinity in the charge free case is shown for a large class of potentials. (This pape...
Yoshida, Zensho
2010-01-01
This book gives a general, basic understanding of the mathematical structure "nonlinearity" that lies in the depths of complex systems. Analyzing the heterogeneity that the prefix "non" represents with respect to notions such as the linear space, integrability and scale hierarchy, "nonlinear science" is explained as a challenge of deconstruction of the modern sciences. This book is not a technical guide to teach mathematical tools of nonlinear analysis, nor a zoology of so-called nonlinear phenomena. By critically analyzing the structure of linear theories, and cl
Nayfeh, Ali Hasan
1995-01-01
Nonlinear Oscillations is a self-contained and thorough treatment of the vigorous research that has occurred in nonlinear mechanics since 1970. The book begins with fundamental concepts and techniques of analysis and progresses through recent developments and provides an overview that abstracts and introduces main nonlinear phenomena. It treats systems having a single degree of freedom, introducing basic concepts and analytical methods, and extends concepts and methods to systems having degrees of freedom. Most of this material cannot be found in any other text. Nonlinear Oscillations uses sim
Energy Technology Data Exchange (ETDEWEB)
Matsumoto, H.; Kimura, T.
1986-01-01
Triggered by the experimental results of the MINIX, a computer simulation study was initiated on the nonlinear excitation of electrostatic electron cyclotron waves by a monochromatic electromagnetic wave such as the transmitted microwave in the MINIX. The model used assumes that both of the excited waves and exciting (pumping) electromagnetic wave as well as the idler electromagnetic wave propagate in the direction perpendicular to the external magnetic field. The simulation code used for this study was the one-and-two-half dimensional electromagnetic particle code named KEMPO. The simulation result shows the high power electromagnetic wave produces both the backscattered electromagnetic wave and electrostatic electron cyclotron waves as a result of nonlinear parametric instability. Detailed nonlinear microphysics related to the wave excitation is discussed in terms of the nonlinear wave-wave couplings and associated ponderomotive force produced by the high power electromagnetic waves. 2 references, 4 figures.
International Nuclear Information System (INIS)
Matsumoto, H.; Kimura, T.
1986-01-01
Triggered by the experimental results of the MINIX, a computer simulation study was initiated on the nonlinear excitation of electrostatic electron cyclotron waves by a monochromatic electromagnetic wave such as the transmitted microwave in the MINIX. The model used assumes that both of the excited waves and exciting (pumping) electromagnetic wave as well as the idler electromagnetic wave propagate in the direction perpendicular to the external magnetic field. The simulation code used for this study was the one-and-two-half dimensional electromagnetic particle code named KEMPO. The simulation result shows the high power electromagnetic wave produces both the backscattered electromagnetic wave and electrostatic electron cyclotron waves as a result of nonlinear parametric instability. Detailed nonlinear microphysics related to the wave excitation is discussed in terms of the nonlinear wave-wave couplings and associated ponderomotive force produced by the high power electromagnetic waves. 2 references, 4 figures
Memory-efficient optimization of Gyrokinetic particle-to-grid interpolation for multicore processors
Energy Technology Data Exchange (ETDEWEB)
Madduri, Kamesh [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Williams, Samuel [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Ethier, Stephane [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Oliker, Leonid [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Shalf, John [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Strohmaier, Erich [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Yelicky, Katherine [Univ. of California, Berkeley, CA (United States)
2009-01-01
We present multicore parallelization strategies for the particle-to-grid interpolation step in the Gyrokinetic Toroidal Code (GTC), a 3D particle-in-cell (PIC) application to study turbulent transport in magnetic-confinement fusion devices. Particle-grid interpolation is a known performance bottleneck in several PIC applications. In GTC, this step involves particles depositing charges to a 3D toroidal mesh, and multiple particles may contribute to the charge at a grid point. We design new parallel algorithms for the GTC charge deposition kernel, and analyze their performance on three leading multicore platforms. We implement thirteen different variants for this kernel and identify the best-performing ones given typical PIC parameters such as the grid size, number of particles per cell, and the GTC-specific particle Larmor radius variation. We find that our best strategies can be 2x faster than the reference optimized MPI implementation, and our analysis provides insight into desirable architectural features for high-performance PIC simulation codes.
Continuum Gyrokinetic Simulations of Turbulence in a Helical Model SOL with NSTX-type parameters
Hammett, G. W.; Shi, E. L.; Hakim, A.; Stoltzfus-Dueck, T.
2017-10-01
We have developed the Gkeyll code to carry out 3D2V full- F gyrokinetic simulations of electrostatic plasma turbulence in open-field-line geometries, using special versions of discontinuous-Galerkin algorithms to help with the computational challenges of the edge region. (Higher-order algorithms can also be helpful for exascale computing as they reduce the ratio of communications to computations.) Our first simulations with straight field lines were done for LAPD-type cases. Here we extend this to a helical model of an SOL plasma and show results for NSTX-type parameters. These simulations include the basic elements of a scrape-off layer: bad-curvature/interchange drive of instabilities, narrow sources to model plasma leaking from the core, and parallel losses with model sheath boundary conditions (our model allows currents to flow in and out of the walls). The formation of blobs is observed. By reducing the strength of the poloidal magnetic field, the heat flux at the divertor plate is observed to broaden. Supported by the Max-Planck/Princeton Center for Plasma Physics, the SciDAC Center for the Study of Plasma Microturbulence, and DOE Contract DE-AC02-09CH11466.
Neoclassical and gyrokinetic analysis of time-dependent helium transport experiments on MAST
International Nuclear Information System (INIS)
Henderson, S.S.; O'Mullane, M.; Summers, H.P.; Garzotti, L.; Casson, F.J.; Dickinson, D.; Fox, M.F.J.; Patel, A.; Roach, C.M.; Valovič, M.
2014-01-01
Time-dependent helium gas puff experiments have been performed on the Mega Ampère Spherical Tokamak (MAST) during a two point plasma current scan in L-mode and a confinement scan at 900 kA. An evaluation of the He II (n = 4 → 3) spectrum line induced by charge exchange suggests anomalous rates of diffusion and inward convection in the outer regions of both L-mode plasmas. Similar rates of diffusion are found in the H-mode plasma, however these rates are consistent with neoclassical predictions. The anomalous inward pinch found in the core of L-mode plasmas is also not apparent in the H-mode core. Linear gyrokinetic simulations of one flux surface in L-mode using the GS2 and GKW codes find that equilibrium flow shear is sufficient to stabilize ITG modes, consistent with beam emission spectroscopy (BES) observations, and suggest that collisionless TEMs may dominate the anomalous helium particle transport. A quasilinear estimate of the dimensionless peaking factor associated with TEMs is in good agreement with experiment. Collisionless TEMs are more stable in H-mode because the electron density gradient is flatter. The steepness of this gradient is therefore pivotal in determining the inward neoclassical particle pinch and the particle flux associated with TEM turbulence. (paper)
International Nuclear Information System (INIS)
Brunner, S.
1997-08-01
Ion temperature gradient (ITG)-related instabilities are studied in tokamak-like plasmas with the help of a new global eigenvalue code. Ions are modelled in the frame of gyrokinetic theory so that finite Larmor radius effects of these particles are retained to all orders. Non-adiabatic trapped electron dynamics is taken into account through the bounce-averaged drift kinetic equation. Assuming electrostatic perturbations, the system is closed with the quasineutrality relation. Practical methods are presented which make this global approach feasible. These include a non-standard wave decomposition compatible with the curved geometry as well as adapting an efficient root finding algorithm for computing the unstable spectrum. These techniques are applied to a low pressure configuration given by a large aspect ratio torus with circular, concentric magnetic surfaces. Simulations from a linear, time evolution, particle in cell code provide a useful benchmark. Comparisons with local ballooning calculations for different parameter scans enable further validation while illustrating the limits of that representation at low toroidal wave numbers or for non-interchange-like instabilities. The stabilizing effect of negative magnetic shear is also considered, in which case the global results show not only an attenuation of the growth rate but also a reduction of the radial extent induced by a transition from the toroidal- to the slab-ITG mode. Contributions of trapped electrons to the ITG instability as well as the possible coupling to the trapped electron mode are clearly brought to the fore. (author) figs., tabs., 69 refs
Gyrokinetic theory of perpendicular cyclotron resonance in a nonuniformly magnetized plasma
International Nuclear Information System (INIS)
Lashmore-Davies, C.N.; Dendy, R.O.
1989-01-01
The extension of gyrokinetic theory to arbitrary frequencies by Chen and Tsai [Phys. Fluids 26, 141 (1983); Plasma Phys. 25, 349 (1983)] is used to study cyclotron absorption in a straight magnetic field with a perpendicular, linear gradient in strength. The analysis includes the effects of magnetic field variation across the Larmor orbit and is restricted to propagation perpendicular to the field. It yields the following results for propagation into the field gradient. The standard optical depths for the fundamental O-mode and second harmonic X-mode resonances are obtained from the absorption profiles given in this paper, without invoking relativistic mass variation [see also Antonsen and Manheimer, Phys. Fluids 21, 2295 (1978)]. The compressional Alfven wave is shown to undergo perpendicular cyclotron damping at the fundamental minority resonance in a two-ion species plasma and at second harmonic resonance in a single-ion species plasma. Ion Bernstein waves propagating into the second harmonic resonance are no longer unattenuated, but are increasingly damped as they approach the resonance. It is shown how the kinetic power flow affects absorption profiles, yielding information previously obtainable only from full-wave theory. In all cases, the perpendicular cyclotron damping arises from the inclusion of magnetic field variation across the Larmor orbit
Neoclassical and gyrokinetic analysis of time-dependent helium transport experiments on MAST
Henderson, S. S.; Garzotti, L.; Casson, F. J.; Dickinson, D.; Fox, M. F. J.; O'Mullane, M.; Patel, A.; Roach, C. M.; Summers, H. P.; Valovič, M.; The MAST Team
2014-09-01
Time-dependent helium gas puff experiments have been performed on the Mega Ampère Spherical Tokamak (MAST) during a two point plasma current scan in L-mode and a confinement scan at 900 kA. An evaluation of the He II (n = 4 → 3) spectrum line induced by charge exchange suggests anomalous rates of diffusion and inward convection in the outer regions of both L-mode plasmas. Similar rates of diffusion are found in the H-mode plasma, however these rates are consistent with neoclassical predictions. The anomalous inward pinch found in the core of L-mode plasmas is also not apparent in the H-mode core. Linear gyrokinetic simulations of one flux surface in L-mode using the GS2 and GKW codes find that equilibrium flow shear is sufficient to stabilize ITG modes, consistent with beam emission spectroscopy (BES) observations, and suggest that collisionless TEMs may dominate the anomalous helium particle transport. A quasilinear estimate of the dimensionless peaking factor associated with TEMs is in good agreement with experiment. Collisionless TEMs are more stable in H-mode because the electron density gradient is flatter. The steepness of this gradient is therefore pivotal in determining the inward neoclassical particle pinch and the particle flux associated with TEM turbulence.
Smoniewski, J.; Faber, B. J.; Sánchez, E.; Calvo, I.; Pueschel, M. J.; Likin, K. M.; Deng, C. B.; Talmadge, J. N.
2017-10-01
The Helically Symmetric eXperiment (HSX) has demonstrated reduced neoclassical transport in the plasma core with quasi-symmetry [Lore Thesis 2010], while outside this region the electron thermal diffusivity is well above the neoclassical level, likely due to the Trapped Electron Mode (TEM) [Weir PoP 2015, Faber PoP 2015]. We compare gyrokinetic simulations of the TEM to experimental heat flux and density fluctuation measurements for two configurations: Quasi-Helical Symmetry (QHS) and broken symmetry (Mirror). Both experiment and simulation show that the heat flux for Mirror is larger than for QHS by about a factor of two. Initial interferometer measurements provide evidence that density-gradient-driven TEMs are driving turbulence. Calculations of the collisionless damping of zonal flows provide another perspective into the difference between geometries. Similar to other stellarators [Monreal PPCF 2016], the zonal flow residual goes to zero at long wavelengths in both configurations. Additionally, the very short time decay of the zonal flow due to neoclassical polarization is constant between configurations. However, the collisionless damping time is longer and the zonal flow oscillation frequency is smaller in QHS than Mirror, consistent with reduced radial particle drifts. Work supported by the US DOE under Grant DE-FG02-93ER54222.
Electromagnetic signatures of far-field gravitational radiation in the 1 + 3 approach
International Nuclear Information System (INIS)
Chua, Alvin J K; Cañizares, Priscilla; Gair, Jonathan R
2015-01-01
Gravitational waves (GWs) from astrophysical sources can interact with background electromagnetic fields, giving rise to distinctive and potentially detectable electromagnetic signatures. In this paper, we study such interactions for far-field gravitational radiation using the 1 + 3 approach to relativity. Linearized equations for the electromagnetic field on perturbed Minkowski space are derived and solved analytically. The inverse Gertsenshteĭn conversion of GWs in a static electromagnetic field is rederived, and the resultant electromagnetic radiation is shown to be significant for highly magnetized pulsars in compact binary systems. We also obtain a variety of nonlinear interference effects for interacting gravitational and electromagnetic waves, although wave–wave resonances previously described in the literature are absent when the electric–magnetic self-interaction is taken into account. The fluctuation and amplification of electromagnetic energy flux as the GW strength increases towards the gravitational–electromagnetic frequency ratio is a possible signature of gravitational radiation from extended astrophysical sources. (paper)
Electromagnetic waves in single- and multi-Josephson junctions
International Nuclear Information System (INIS)
Matsumoto, Hideki; Koyama, Tomio; Machida, Masahiko
2008-01-01
The terahertz wave emission from the intrinsic Josephson junctions is one of recent topics in high T c superconductors. We investigate, by numerical simulation, properties of the electromagnetic waves excited by a constant bias current in the single- and multi-Josephson junctions. Nonlinear equations of phase-differences are solved numerically by treating the effects of the outside electromagnetic fields as dynamical boundary conditions. It is shown that the emitted power of the electromagnetic wave can become large near certain retrapping points of the I-V characteristics. An instability of the inside phase oscillation is related to large amplitude of the oscillatory waves. In the single- (or homogeneous mutli-) Josephson junctions, electromagnetic oscillations can occur either in a form of standing waves (shorter junctions) or by formation of vortex-antivortex pairs (longer junctions). How these two effects affects the behavior of electromagnetic waves in the intrinsic Josephson junctions is discussed
Palmero, Faustino; Lemos, M; Sánchez-Rey, Bernardo; Casado-Pascual, Jesús
2018-01-01
This book presents an overview of the most recent advances in nonlinear science. It provides a unified view of nonlinear properties in many different systems and highlights many new developments. While volume 1 concentrates on mathematical theory and computational techniques and challenges, which are essential for the study of nonlinear science, this second volume deals with nonlinear excitations in several fields. These excitations can be localized and transport energy and matter in the form of breathers, solitons, kinks or quodons with very different characteristics, which are discussed in the book. They can also transport electric charge, in which case they are known as polarobreathers or solectrons. Nonlinear excitations can influence function and structure in biology, as for example, protein folding. In crystals and other condensed matter, they can modify transport properties, reaction kinetics and interact with defects. There are also engineering applications in electric lattices, Josephson junction a...
Nonlinear theory of the free-electron laser
International Nuclear Information System (INIS)
Chian, A.C.-L.; Padua Brito Serbeto, A. de.
1984-01-01
A theory of Raman free-electron laser using a circularly polarized electromagnetic pump is investigated. Coupled wave equations that describe both linear and nonlinear evolution of stimulated Raman scattering are derived. The dispersion relation and the growth rate for the parametric instability are obtained. Nonlinear processes that may lead to saturation of the free-electron laser are discussed. (Author) [pt
Three-dimensional sparse electromagnetic imaging accelerated by projected steepest descent
Desmal, Abdulla; Bagci, Hakan
2016-01-01
An efficient and accurate scheme for solving the nonlinear electromagnetic inverse scattering problem on three-dimensional sparse investigation domains is proposed. The minimization problem is constructed in such a way that the data misfit between
Variation principle for nonlinear wave propagation
International Nuclear Information System (INIS)
Watanabe, T.; Lee, Y.C.; Nishikawa, Kyoji; Hojo, H.; Yoshida, Y.
1976-01-01
Variation principle is derived which determines stationary nonlinear propagation of electrostatic waves in the self-consistent density profile. Example is given for lower-hybrid waves and the relation to the variation principle for the Lagrangian density of electromagnetic fluids is discussed
Spatiotemporal solitons in quadratic nonlinear media
Indian Academy of Sciences (India)
Optical solitons are localized electromagnetic waves that propagate stably in .... conversion generates a nonlinear phase shift ∆ΦNL at the FH frequency. ... to incidence on the SHG crystal (lithium iodate or barium borate, cut for type-I interac-.
Electromagnetic wave matching device
International Nuclear Information System (INIS)
Hirata, Yosuke; Mitsunaka, Yoshika; Hayashi, Ken-ichi; Ito, Yasuyuki.
1997-01-01
The present invention provides a matching device capable of increasing an efficiency of combining beams of electromagnetic waves outputted from an output window of a gyrotron which is expected for plasma heating of a thermonuclear reactor and an electromagnetic wave transmission system as high as possible. Namely, an electromagnetic wave matching device reflects beams of electromagnetic waves incident from an inlet by a plurality of phase correction mirrors and combines them to an external transmission system through an exit. In this case, the phase correction mirrors change the phase of the beams of electromagnetic waves incident to the phase correction mirrors by a predetermined amount corresponding to the position of the reflection mirrors. Then, the beams of electromagnetic waves outputted, for example, from a gyrotron can properly be shaped as desired for the intensity and the phase. As a result, combination efficiency with the transmission system can be increased. (I.S.)
Electromagnetic ultrasonic guided waves
Huang, Songling; Li, Weibin; Wang, Qing
2016-01-01
This book introduces the fundamental theory of electromagnetic ultrasonic guided waves, together with its applications. It includes the dispersion characteristics and matching theory of guided waves; the mechanism of production and theoretical model of electromagnetic ultrasonic guided waves; the effect mechanism between guided waves and defects; the simulation method for the entire process of electromagnetic ultrasonic guided wave propagation; electromagnetic ultrasonic thickness measurement; pipeline axial guided wave defect detection; and electromagnetic ultrasonic guided wave detection of gas pipeline cracks. This theory and findings on applications draw on the author’s intensive research over the past eight years. The book can be used for nondestructive testing technology and as an engineering reference work. The specific implementation of the electromagnetic ultrasonic guided wave system presented here will also be of value for other nondestructive test developers.
Basic Electromagnetism and Materials
Moliton, André
2007-01-01
Basic Electromagnetism and Materials is the product of many years of teaching basic and applied electromagnetism. This textbook can be used to teach electromagnetism to a wide range of undergraduate science majors in physics, electrical engineering or materials science. However, by making lesser demands on mathematical knowledge than competing texts, and by emphasizing electromagnetic properties of materials and their applications, this textbook is uniquely suited to students of materials science. Many competing texts focus on the study of propagation waves either in the microwave or optical domain, whereas Basic Electromagnetism and Materials covers the entire electromagnetic domain and the physical response of materials to these waves. Professor André Moliton is Director of the Unité de Microélectronique, Optoélectronique et Polymères (Université de Limoges, France), which brings together three groups studying the optoelectronics of molecular and polymer layers, micro-optoelectronic systems for teleco...
Boyd, Robert W
2013-01-01
Nonlinear Optics is an advanced textbook for courses dealing with nonlinear optics, quantum electronics, laser physics, contemporary and quantum optics, and electrooptics. Its pedagogical emphasis is on fundamentals rather than particular, transitory applications. As a result, this textbook will have lasting appeal to a wide audience of electrical engineering, physics, and optics students, as well as those in related fields such as materials science and chemistry.Key Features* The origin of optical nonlinearities, including dependence on the polarization of light* A detailed treatment of the q
Review on Computational Electromagnetics
Directory of Open Access Journals (Sweden)
P. Sumithra
2017-03-01
Full Text Available Computational electromagnetics (CEM is applied to model the interaction of electromagnetic fields with the objects like antenna, waveguides, aircraft and their environment using Maxwell equations. In this paper the strength and weakness of various computational electromagnetic techniques are discussed. Performance of various techniques in terms accuracy, memory and computational time for application specific tasks such as modeling RCS (Radar cross section, space applications, thin wires, antenna arrays are presented in this paper.
Static electromagnetic frequency changers
Rozhanskii, L L
1963-01-01
Static Electromagnetic Frequency Changers is about the theory, design, construction, and applications of static electromagnetic frequency changers, devices that used for multiplication or division of alternating current frequency. It is originally published in the Russian language. This book is organized into five chapters. The first three chapters introduce the readers to the principles of operation, the construction, and the potential applications of static electromagnetic frequency changers and to the principles of their design. The two concluding chapters use some hitherto unpublished work
Model for Electromagnetic Information Leakage
Mao Jian; Li Yongmei; Zhang Jiemin; Liu Jinming
2013-01-01
Electromagnetic leakage will happen in working information equipments; it could lead to information leakage. In order to discover the nature of information in electromagnetic leakage, this paper combined electromagnetic theory with information theory as an innovative research method. It outlines a systematic model of electromagnetic information leakage, which theoretically describes the process of information leakage, intercept and reproduction based on electromagnetic radiation, and ana...
Electromagnetic solitary waves in magnetized plasmas
International Nuclear Information System (INIS)
Hazeltine, R.D.; Holm, D.D.; Morrison, P.J.
1985-03-01
A Hamiltonian formulation, in terms of noncanonical Poisson bracket, is presented for a nonlinear fluid system that includes reduced magnetohydrodynamics and the Hasegawa-Mima equation as limiting cases. The single-helicity and axisymmetric versions possess three nonlinear Casimir invariants, from which a generalized potential can be constructed. Variation of the generalized potential yields a description of exact nonlinear stationary states. The new equilibria, allowing for plasma flow as well as partial electron adiabaticity, are distinct from those found in conventional magnetohydrodynamic theory. They differ from electrostatic stationary states in containing plasma current and magnetic field excitation. One class of steady-state solutions is shown to provide a simple electromagnetic generalization of drift-solitary waves
Electromagnetic Interface Testing Facility
Federal Laboratory Consortium — The Electromagnetic Interface Testing facilitysupports such testing asEmissions, Field Strength, Mode Stirring, EMP Pulser, 4 Probe Monitoring/Leveling System, and...
The modulational and filamentational instabilities of two coupled electromagnetic waves in plasmas
International Nuclear Information System (INIS)
Shukla, P.K.
1992-01-01
The modulational and filamentational instabilities of two coupled electromagnetic waves have been investigated, taking into account the combined effect of relativistic electron mass variations and nonresonant density fluctuations that are driven by the ponderomotive force. The relevance of our investigation to phenomena related with nonlinear mixing of electromagnetic waves is pointed out. (orig.)
On the self-trapping of an electromagnetic wave in magnetized plasma
International Nuclear Information System (INIS)
El-Ashry, M.Y.; Berezhiani, V.I.; Pichkhadze, Sh.D.
1987-06-01
The possibility of relativistic self-trapping of an electromagnetic wave in magnetized plasma is studied. It is shown that in the case of propagation of fast wave packet of electromagnetic wave in plasma, self-trapping is possible due to the effect of relativistic non-linearity, which is effective even for small amplitudes of the pumping wave. (author). 7 refs
National Research Council Canada - National Science Library
Drazin, P. G
1992-01-01
This book is an introduction to the theories of bifurcation and chaos. It treats the solution of nonlinear equations, especially difference and ordinary differential equations, as a parameter varies...
Gasinski, Leszek
2005-01-01
Hausdorff Measures and Capacity. Lebesgue-Bochner and Sobolev Spaces. Nonlinear Operators and Young Measures. Smooth and Nonsmooth Analysis and Variational Principles. Critical Point Theory. Eigenvalue Problems and Maximum Principles. Fixed Point Theory.
A new hybrid-Lagrangian numerical scheme for gyrokinetic simulation of tokamak edge plasma
Energy Technology Data Exchange (ETDEWEB)
Ku, S., E-mail: sku@pppl.gov [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Hager, R.; Chang, C.S. [Princeton Plasma Physics Laboratory, Princeton University, Princeton, NJ 08543 (United States); Kwon, J.M. [National Fusion Research Institute (Korea, Republic of); Parker, S.E. [University of Colorado Boulder (United States)
2016-06-15
In order to enable kinetic simulation of non-thermal edge plasmas at a reduced computational cost, a new hybrid-Lagrangian δf scheme has been developed that utilizes the phase space grid in addition to the usual marker particles, taking advantage of the computational strengths from both sides. The new scheme splits the particle distribution function of a kinetic equation into two parts. Marker particles contain the fast space-time varying, δf, part of the distribution function and the coarse-grained phase-space grid contains the slow space-time varying part. The coarse-grained phase-space grid reduces the memory-requirement and the computing cost, while the marker particles provide scalable computing ability for the fine-grained physics. Weights of the marker particles are determined by a direct weight evolution equation instead of the differential form weight evolution equations that the conventional delta-f schemes use. The particle weight can be slowly transferred to the phase space grid, thereby reducing the growth of the particle weights. The non-Lagrangian part of the kinetic equation – e.g., collision operation, ionization, charge exchange, heat-source, radiative cooling, and others – can be operated directly on the phase space grid. Deviation of the particle distribution function on the velocity grid from a Maxwellian distribution function – driven by ionization, charge exchange and wall loss – is allowed to be arbitrarily large. The numerical scheme is implemented in the gyrokinetic particle code XGC1, which specializes in simulating the tokamak edge plasma that crosses the magnetic separatrix and is in contact with the material wall.
International Nuclear Information System (INIS)
Baumgaertel J.A., Redi M.H., Budny R.V., Rewoldt G., Dorland W.
2005-01-01
Insight into plasma microturbulence and transport is being sought using linear simulations of drift waves on the National Spherical Torus Experiment (NSTX), following a study of drift wave modes on the Alcator C-Mod Tokamak. Microturbulence is likely generated by instabilities of drift waves, which cause transport of heat and particles. Understanding this transport is important because the containment of heat and particles is required for the achievement of practical nuclear fusion. Microtearing modes may cause high heat transport through high electron thermal conductivity. It is hoped that microtearing will be stable along with good electron transport in the proposed low collisionality International Thermonuclear Experimental Reactor (ITER). Stability of the microtearing mode is investigated for conditions at mid-radius in a high density NSTX high performance (H-mode) plasma, which is compared to the proposed ITER plasmas. The microtearing mode is driven by the electron temperature gradient, and believed to be mediated by ion collisions and magnetic shear. Calculations are based on input files produced by TRXPL following TRANSP (a time-dependent transport analysis code) analysis. The variability of unstable mode growth rates is examined as a function of ion and electron collisionalities using the parallel gyrokinetic computational code GS2. Results show the microtearing mode stability dependence for a range of plasma collisionalities. Computation verifies analytic predictions that higher collisionalities than in the NSTX experiment increase microtearing instability growth rates, but that the modes are stabilized at the highest values. There is a transition of the dominant mode in the collisionality scan to ion temperature gradient character at both high and low collisionalities. The calculations suggest that plasma electron thermal confinement may be greatly improved in the low-collisionality ITER
Gyrokinetic analysis of ion temperature gradient modes in the presence of sheared flows
International Nuclear Information System (INIS)
Artun, M.; Tang, W.M.
1992-01-01
The linearized gyrokinetic equation governing electrostatic microinstabilities in the presence of sheared equilibrium flow in both the z and y directions has been systematically derived for a sheared slab geometry, where in the large aspect ratio limit z and y directions correspond to the toroidal and poloidal directions respectively. In the familiar long perpendicular wavelength regime (κ perpendicular ρi > 1), the analysis leads to a comprehensive kinetic differential eigenmode equation which is solved numerically. The numerical results have been successfully cross-checked against analytic estimates in the fluid limit. For typical conditions, the Ion Temperature Gradient (ηi) modes are found to be stabilized for y-direction flows with a velocity shear scale comparable to that of the ion temperature gradient and velocities of a few percent of the sound speed. Sheared flows in the z-direction taken along are usually destabilizing, with the effect being independent of the sign of the flow. However, when both types are simultaneously considered, it is found that in the presence of shared z-direction flow, sheared y-direction flow can be either stabilizing or destabilizing depending on the relative sign of these flows. However, for sufficiently large values of υ' y the mode is completely stabilized regardless of the sign of υ' z υ' y . The importance of a proper kinetic treatment of this problem is supported by comparisons with fluid estimates. In particular, when such effects are favorable, significantly smaller values of sheared y-direction flow are required for stability than fluid estimates would indicate
SciDAC Center for Gyrokinetic Particle Simulation of Turbulent Transport in Burning Plasmas
Energy Technology Data Exchange (ETDEWEB)
Lin, Zhihong [Univ. of California, Irvine, CA (United States)
2013-12-18
During the first year of the SciDAC gyrokinetic particle simulation (GPS) project, the GPS team (Zhihong Lin, Liu Chen, Yasutaro Nishimura, and Igor Holod) at the University of California, Irvine (UCI) studied the tokamak electron transport driven by electron temperature gradient (ETG) turbulence, and by trapped electron mode (TEM) turbulence and ion temperature gradient (ITG) turbulence with kinetic electron effects, extended our studies of ITG turbulence spreading to core-edge coupling. We have developed and optimized an elliptic solver using finite element method (FEM), which enables the implementation of advanced kinetic electron models (split-weight scheme and hybrid model) in the SciDAC GPS production code GTC. The GTC code has been ported and optimized on both scalar and vector parallel computer architectures, and is being transformed into objected-oriented style to facilitate collaborative code development. During this period, the UCI team members presented 11 invited talks at major national and international conferences, published 22 papers in peer-reviewed journals and 10 papers in conference proceedings. The UCI hosted the annual SciDAC Workshop on Plasma Turbulence sponsored by the GPS Center, 2005-2007. The workshop was attended by about fifties US and foreign researchers and financially sponsored several gradual students from MIT, Princeton University, Germany, Switzerland, and Finland. A new SciDAC postdoc, Igor Holod, has arrived at UCI to initiate global particle simulation of magnetohydrodynamics turbulence driven by energetic particle modes. The PI, Z. Lin, has been promoted to the Associate Professor with tenure at UCI.
Nonlinear theory of electroelastic and magnetoelastic interactions
Dorfmann, Luis
2014-01-01
This book provides a unified theory of nonlinear electro-magnetomechanical interactions of soft materials capable of large elastic deformations. The authors include an overview of the basic principles of the classical theory of electromagnetism from the fundamental notions of point charges and magnetic dipoles through to distributions of charge and current in a non-deformable continuum, time-dependent electromagnetic fields and Maxwell’s equations. They summarize the basic ingredients of continuum mechanics that are required to account for the deformability of material and present nonlinear constitutive frameworks for electroelastic and magnetoelastic interactions in a highly deformable material. The equations contained in the book are used to formulate and solve a variety of representative boundary-value problems for both nonlinear electroelasticity and magnetoelasticity.
An Electromagnetic Beam Converter
DEFF Research Database (Denmark)
2009-01-01
The present invention relates to an electromagnetic beam converter and a method for conversion of an input beam of electromagnetic radiation having a bell shaped intensity profile a(x,y) into an output beam having a prescribed target intensity profile l(x',y') based on a further development...
Classical electromagnetic radiation
Heald, Mark A
2012-01-01
Newly corrected, this highly acclaimed text is suitable for advanced physics courses. The author presents a very accessible macroscopic view of classical electromagnetics that emphasizes integrating electromagnetic theory with physical optics. The survey follows the historical development of physics, culminating in the use of four-vector relativity to fully integrate electricity with magnetism.
High frequency electromagnetic dosimetry
Sánchez-Hernández, David A
2009-01-01
Along with the growth of RF and microwave technology applications, there is a mounting concern about the possible adverse effects over human health from electromagnetic radiation. Addressing this issue and putting it into perspective, this groundbreaking resource provides critical details on the latest advances in high frequency electromagnetic dosimetry.
Electromagnetically Operated Counter
Goldberg, H D; Goldberg, M I
1951-12-18
An electromagnetically operated counter wherein signals to be counted are applied to cause stepwise rotation of a rotatable element which is connected to a suitable register. The mechanism involved consists of a rotatable armature having three spaced cores of magnetic material and a pair of diametrically opposed electromagnets with a suitable pulsing circuit to actuate the magnets.
Electromagnetic cyclotron harmonic waves
International Nuclear Information System (INIS)
Ohnuma, T.; Watanabe, T.; Hamamatsu, K.
1981-09-01
Electromagnetic electron cyclotron harmonic waves just below the electron cyclotron harmonics are investigated numerically and experimentally. Backward waves which are observed to propagate nearly perpendicular to the magnetic field just below the electron cyclotron frequency in a high density magnetoplasma are confirmed to be in accord with the theoretical electromagnetic cyclotron waves. (author)
Propagation of strong electromagnetic beams in inhomogeneous plasmas
Energy Technology Data Exchange (ETDEWEB)
Ferrari, A; Massaglia, S [Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica; Turin Univ. (Italy). Ist. di Fisica Generale)
1980-09-01
We study some simple aspects of nonlinear propagation of relativistically strong electromagnetic beams in inhomogeneous plasmas, especially in connection with effects of beam self-trapping in extended extragalactic radio sources. The two effects of (i) long scale longitudinal and radial inhomogeneities inherent to the plasma and (ii) radial inhomogeneities produced by the ponderomotive force of the beam itself are investigated.
Dark and bright vortex solitons in electromagnetically induced transparent media
International Nuclear Information System (INIS)
Wu Xuan; Xie Xiaotao; Yang Xiaoxue
2006-01-01
We show that dark and bright vortex solitons can exist in three-state electromagnetically induced transparent media under some appropriate conditions. We also analyse the stability of the dark and bright vortex solitons. This work may provide other research opportunities in nonlinear optical experiments and may result in a substantial impact on technology
Quantum control of light using electromagnetically induced transparency
International Nuclear Information System (INIS)
Andre, A; Eisaman, M D; Walsworth, R L; Zibrov, A S; Lukin, M D
2005-01-01
We present an overview of recent theoretical and experimental work on the control of the propagation and quantum properties of light using electromagnetically induced transparency in atomic ensembles. Specifically, we discuss techniques for the generation and storage of few-photon quantum-mechanical states of light as well as novel approaches to manipulate weak pulses of light via enhanced nonlinear optical processes
Electromagnetic effects on trace impurity transport in tokamak plasmas
Hein, T.; Angioni, C.
2010-01-01
The impact of electromagnetic effects on the transport of light and heavy impurities in tokamak plasmas is investigated by means of an extensive set of linear gyrokinetic numerical calculations with the code GYRO [J. Candy and R. E. Waltz, J. Comput. Phys. 186, 545 (2003)] and of analytical derivations with a fluid model. The impurity transport is studied by appropriately separating diffusive and convective contributions, and conditions of background microturbulence dominated by both ion temperature gradient (ITG) and trapped electron modes (TEMs) are analyzed. The dominant contribution from magnetic flutter transport turns out to be of pure convective type. However it remains small, below 10% with respect to the E ×B transport. A significant impact on the impurity transport due to an increase in the plasma normalized pressure parameter β is observed in the case of ITG modes, while for TEM the overall effect remains weak. In realistic conditions of high β plasmas in the high confinement (H-) mode with dominant ITG turbulence, the impurity diffusivity is found to decrease with increasing β in qualitative agreement with recent observations in tokamaks. In contrast, in these conditions, the ratio of the total off-diagonal convective velocity to the diagonal diffusivity is not strongly affected by an increase in β, particularly at low impurity charge, due to a compensation between the different off-diagonal contributions.
International Nuclear Information System (INIS)
Omura, Yoshiharu; Matsumoto, Hiroshi.
1989-01-01
Past theoretical and numerical studies of the nonlinear evolution of electromagnetic cyclotron waves are reviewed. Such waves are commonly observed in space plasmas such as Alfven waves in the solar wind or VLF whistler mode waves in the magnetosphere. The use of an electromagnetic full-particle code to study an electron cyclotron wave and of an electromagnetic hybrid code to study an ion cyclotron wave is demonstrated. Recent achievements in the simulations of nonlinear revolution of electromagnetic cyclotron waves are discussed. The inverse cascading processes of finite-amplitude whistler and Alfven waves is interpreted in terms of physical elementary processes. 65 refs
Rogers, Barrett N.; Zhu, Ben; Francisquez, Manaure
2018-05-01
A gyrokinetic linear stability analysis of a collisionless slab geometry in the local approximation is presented. We focus on k∥=0 universal (or entropy) modes driven by plasma gradients at small and large plasma β. These are small scale non-MHD instabilities with growth rates that typically peak near k⊥ρi˜1 and vanish in the long wavelength k⊥→0 limit. This work also discusses a mode known as the Gradient Drift Coupling (GDC) instability previously reported in the gyrokinetic literature, which has a finite growth rate γ=√{β/[2 (1 +β)] }Cs/|Lp| with Cs2=p0/ρ0 for k⊥→0 and is universally unstable for 1 /Lp≠0 . We show that the GDC instability is a spurious, unphysical artifact that erroneously arises due to the failure to respect the total equilibrium pressure balance p0+B02/(8 π)=constant , which renders the assumption B0'=0 inconsistent if p0'≠0 .
Bao, J.; Liu, D.; Lin, Z.
2017-10-01
A conservative scheme of drift kinetic electrons for gyrokinetic simulations of kinetic-magnetohydrodynamic processes in toroidal plasmas has been formulated and verified. Both vector potential and electron perturbed distribution function are decomposed into adiabatic part with analytic solution and non-adiabatic part solved numerically. The adiabatic parallel electric field is solved directly from the electron adiabatic response, resulting in a high degree of accuracy. The consistency between electrostatic potential and parallel vector potential is enforced by using the electron continuity equation. Since particles are only used to calculate the non-adiabatic response, which is used to calculate the non-adiabatic vector potential through Ohm's law, the conservative scheme minimizes the electron particle noise and mitigates the cancellation problem. Linear dispersion relations of the kinetic Alfvén wave and the collisionless tearing mode in cylindrical geometry have been verified in gyrokinetic toroidal code simulations, which show that the perpendicular grid size can be larger than the electron collisionless skin depth when the mode wavelength is longer than the electron skin depth.
International Nuclear Information System (INIS)
Ohana, N; Lanti, E; Tran, T M; Brunner, S; Hariri, F; Villard, L; Jocksch, A; Gheller, C
2016-01-01
With the aim of enabling state-of-the-art gyrokinetic PIC codes to benefit from the performance of recent multithreaded devices, we developed an application from a platform called the “PIC-engine” [1, 2, 3] embedding simplified basic features of the PIC method. The application solves the gyrokinetic equations in a sheared plasma slab using B-spline finite elements up to fourth order to represent the self-consistent electrostatic field. Preliminary studies of the so-called Particle-In-Fourier (PIF) approach, which uses Fourier modes as basis functions in the periodic dimensions of the system instead of the real-space grid, show that this method can be faster than PIC for simulations with a small number of Fourier modes. Similarly to the PIC-engine, multiple levels of parallelism have been implemented using MPI+OpenMP [2] and MPI+OpenACC [1], the latter exploiting the computational power of GPUs without requiring complete code rewriting. It is shown that sorting particles [3] can lead to performance improvement by increasing data locality and vectorizing grid memory access. Weak scalability tests have been successfully run on the GPU-equipped Cray XC30 Piz Daint (at CSCS) up to 4,096 nodes. The reduced time-to-solution will enable more realistic and thus more computationally intensive simulations of turbulent transport in magnetic fusion devices. (paper)
Three-dimensional analysis of nonlinear plasma oscillation
International Nuclear Information System (INIS)
Miano, G.
1990-01-01
In an underdense plasma a large-amplitude plasma oscillation may be produced by the beating of two external and colinear electromagnetic waves with a frequency difference approximately equal to the plasma frequency - plasma beat wave (PBW) resonant mechanism. The plasma oscillations are driven by the ponderomotive force arising from the beating of the two imposed electromagnetic waves. In this paper two pump electromagnetic waves with arbitrary transverse profiles have been considered. The plasma is described by using the three dimensinal weakly relativistic fluid equations. The nonlinear plasma oscillation dynamics is studied by using the eulerian description, the averaging and the multiple time scale methods. Unlike the linear theory a strong cross field coupling between longitudinal ans transverse electric field components of the plasma oscillation comes out, resulting in a nonlinear phase change and energy transfer between the two components. Unlike the one-dimensional nonlinear theory, the nonlinear frequency shift is caused by relativistic effects as well as by convective effects and electromagnetic field generated from the three dimensional plasma oscillation. The large amplitude plasma oscillation dynamics produced by a bunched relativistic electron beam with arbitrary transverse profile - plasma wave field (PWF) - or by a high power single frequency short electromagnetic pulse with arbitrary transverse profile - electromagnetic plasma wake field (EPWF) - may be described by means of the present theory. (orig.)
Ruszczynski, Andrzej
2011-01-01
Optimization is one of the most important areas of modern applied mathematics, with applications in fields from engineering and economics to finance, statistics, management science, and medicine. While many books have addressed its various aspects, Nonlinear Optimization is the first comprehensive treatment that will allow graduate students and researchers to understand its modern ideas, principles, and methods within a reasonable time, but without sacrificing mathematical precision. Andrzej Ruszczynski, a leading expert in the optimization of nonlinear stochastic systems, integrates the theory and the methods of nonlinear optimization in a unified, clear, and mathematically rigorous fashion, with detailed and easy-to-follow proofs illustrated by numerous examples and figures. The book covers convex analysis, the theory of optimality conditions, duality theory, and numerical methods for solving unconstrained and constrained optimization problems. It addresses not only classical material but also modern top...
Merlo, G.; Brunner, S.; Sauter, O.; Camenen, Y.; Görler, T.; Jenko, F.; Marinoni, A.; Told, D.; Villard, L.
2015-05-01
The experimental observation made on the TCV tokamak of a significant confinement improvement in plasmas with negative triangularity (δ TEMs) and electron temperature gradient (ETG) modes are the dominant microinstabilities, with the latter providing a significant contribution to the non-linear electron heat fluxes near the plasma edge. Two series of simulations with different levels of realism are performed, addressing the question of profile stiffness at various radial locations. Retaining finite collisionality, impurities and electromagnetic effects, as well as the physical electron-to-ion mass ratio are all necessary in order to approach the experimental flux measurements. However, flux-tube simulations are unable to fully reproduce the TCV results, pointing towards the need to carry out radially nonlocal (global) simulations, i.e. retaining finite machine size effects, in a future study. Some conclusions about the effect of triangularity can nevertheless be drawn based on the flux-tube results. In particular, the importance of considering the sensitivity to both temperature and density gradient is shown. The flux tube results show an increase of the critical gradients towards the edge, further enhanced when δ < 0, and they also appear to indicate a reduction of profile stiffness towards plasma edge.
International Nuclear Information System (INIS)
Takahashi, Kenji.
1994-01-01
As an electromagnetic shaft seal, there are disposed outwarding electromagnetic induction devices having generating power directing to an electroconductive fluid as an object of sealing, and inwarding electromagnetic induction device added coaxially. There are disposed elongate rectangular looped first coils having a predetermined inner diameter, second coils having the same shape and shifted by a predetermined pitch relative to the first coil and third coil having the same shape and shifted by a predetermined pitch relative to the second coil respectively each at a predetermined inner diameter of clearance to the outwarding electromagnetic induction devices and the inwarding electromagnetic induction device. If the inwarding electromagnetic induction device and the outwarding electromagnetic induction device are operated, they are stopped at a point that the generating power of the former is equal with the sum of the generating power of the latter and a differential pressure. When three-phase AC is charged to the first coil, the second coil and the third coil successively, a force is generated in the advancing direction of the magnetic field in the electroconductive fluid by the similar effect to that of a linear motor, and the seal is maintained at high reliability. Moreover, the limit for the rotational angle of the shaft is not caused. (N.H.)
Terahertz Solitons in Biomolecular Systems and their Excitation by External Electromagnetic Field
Directory of Open Access Journals (Sweden)
Bugay А.N.
2015-01-01
Full Text Available Nonlinear dynamics of charge and acoustic excitations in cellular microtubules is considered. Different types of nonlinear solitary waves were studied taking account for dissipation. The mechanism of electro-acoustic pulse excitation by external electromagnetic field of terahertz frequency is recognized.
Nonlinear interplay of TEM and ITG turbulence and its effect on transport
Merz, F.; Jenko, F.
2010-05-01
The dominant source of anomalous transport in fusion plasmas on ion scales is turbulence driven by trapped electron modes (TEMs) and ion temperature gradient (ITG) modes. While the individual properties of each of these two instabilities and the corresponding microturbulence have been examined in detail in the past, the effects of a coexistence of the two modes and the phenomena of transitions between the TEM and ITG dominated regimes are not well studied. In many experimental situations, the temperature and density gradients support both microinstabilities simultaneously, so that transitional regimes are important for a detailed understanding of fusion plasmas. In this paper, this issue is addressed, using the gyrokinetic code GENE for a detailed investigation of the dominant and subdominant linear instabilities and the corresponding nonlinear system. A simple quasilinear model based on eigenvalue computations is presented which is shown to reproduce important features of the nonlinear TEM-ITG transition.
Curved electromagnetic missiles
International Nuclear Information System (INIS)
Myers, J.M.; Shen, H.M.; Wu, T.T.
1989-01-01
Transient electromagnetic fields can exhibit interesting behavior in the limit of great distances from their sources. In situations of finite total radiated energy, the energy reaching a distant receiver can decrease with distance much more slowly than the usual r - 2 . Cases of such slow decrease have been referred to as electromagnetic missiles. All of the wide variety of known missiles propagate in essentially straight lines. A sketch is presented here of a missile that can follow a path that is strongly curved. An example of a curved electromagnetic missile is explicitly constructed and some of its properties are discussed. References to details available elsewhere are given
Electromagnetic spatial coherence wavelets
International Nuclear Information System (INIS)
Castaneda, R.; Garcia-Sucerquia, J.
2005-10-01
The recently introduced concept of spatial coherence wavelets is generalized for describing the propagation of electromagnetic fields in the free space. For this aim, the spatial coherence wavelet tensor is introduced as an elementary amount, in terms of which the formerly known quantities for this domain can be expressed. It allows analyzing the relationship between the spatial coherence properties and the polarization state of the electromagnetic wave. This approach is completely consistent with the recently introduced unified theory of coherence and polarization for random electromagnetic beams, but it provides a further insight about the causal relationship between the polarization states at different planes along the propagation path. (author)
The structure of electromagnetism and gravitation
International Nuclear Information System (INIS)
Pommaret, J.F.
1983-01-01
The formalisms of gauge theory and continuum mechanics linked to the construction of the non-linear Spencer sequences in the formal theory of Lie pseudogroups give results showing that a contradiction exists between the two theories quoted above as the Yang-Mills ''potentials'' of physicists are sections of the first Spencer vector bundle, coming from connections, while the ''fields'' of mechanicians are sections of the same bundle, not coming from connections. The purpose of this Note is to explain this contradiction by showing that the electromagnetic model of gauge theory must be modified. Maxwell and Einstein equations then automatically appear in this differential framework that unifies electromagnetism and gravitation. These conclusions are imposed, not by the choice of physical assumptions, but by the use of a new mathematical tool [fr
Self-modulation and filamentation of electromagnetic waves in a plasma
International Nuclear Information System (INIS)
Bingham, R.; Lashmore-Davies, C.N.
1976-01-01
Self-modulation and filamentation of an electromagnetic wave is considered as a problem of the non-linear interaction between electromagnetic and ion waves. A new electro-magnetic modulational instability is obtained, whose threshold is the same as that of the oscillating two-stream instability. A simple geometrical model is given of filamentation when the non-linearity is due to the ponderomotive force. The relationship between the filamentation and electromagnetic modulational instabilities and other parametric instabilities is considered. In particular, it is shown that both electromagnetic modulational and filamentation instabilities can occur at the critical density where they have the same threshold as the modulational instability of a Langmuir wave. Finally, a conservation relation (a generalization of the Manley-Rowe relation) for the wave action density is obtained for the filamentation instability. This shows clearly that this instability results from a four wave interaction. (author)
Statistical electromagnetics: Complex cavities
Naus, H.W.L.
2008-01-01
A selection of the literature on the statistical description of electromagnetic fields and complex cavities is concisely reviewed. Some essential concepts, for example, the application of the central limit theorem and the maximum entropy principle, are scrutinized. Implicit assumptions, biased
Broadband Electromagnetic Technology
2011-06-23
The objectives of this project are to continue the enhancements to the combined Broadband Electromagnetic and Full Encirclement Unit (BEM-FEU) technologies and to evaluate the systems capability in the laboratory and the field. The BEM instrument ...
Magnetorheological suspension electromagnetic brake
International Nuclear Information System (INIS)
Bica, Ioan
2004-01-01
The magnetorheological suspension (MRS) brake is of the monoblock type. The main part of the electromagnetic brake is an electromagnet, between whose poles two MRS disks are placed. For distances between disks of 0.65x10 -3 m±10%, revolutions of the electric motor, coupled to the electromagnetic brake, ranging between 200 and 1600 rev/min and braking powers of up to 85 W, there are no differences in revolutions between the disks of the electromagnetic brake. For fixed revolutions of the electric motor, the revolution of the parallel disk can be modified continuously by means of the intensity of the magnetic field. In all cases, the quantity of MRS is of 0.35x10 -3 kg
Computational electromagnetic-aerodynamics
Shang, Joseph J S
2016-01-01
Presents numerical algorithms, procedures, and techniques required to solve engineering problems relating to the interactions between electromagnetic fields, fluid flow, and interdisciplinary technology for aerodynamics, electromagnetics, chemical-physics kinetics, and plasmadynamics This book addresses modeling and simulation science and technology for studying ionized gas phenomena in engineering applications. Computational Electromagnetic-Aerodynamics is organized into ten chapters. Chapter one to three introduce the fundamental concepts of plasmadynamics, chemical-physics of ionization, classical magnetohydrodynamics, and their extensions to plasma-based flow control actuators, high-speed flows of interplanetary re-entry, and ion thrusters in space exploration. Chapter four to six explain numerical algorithms and procedures for solving Maxwell’s equation in the time domain for computational electromagnetics, plasma wave propagation, and the time-dependent c mpressible Navier-Stokes equation for aerodyn...
OPAL detector electromagnetic calorimeter
1988-01-01
Half of the electromagnetic calorimeter of the OPAL detector is seen in this photo. This calorimeter consists of 4720 blocks of lead glass. It was used to detect and measure the energy of photons, electrons and positrons by absorbing them.
The classical electromagnetic field
Eyges, Leonard
2010-01-01
This excellent text covers a year's course in advanced theoretical electromagnetism, first introducing theory, then its application. Topics include vectors D and H inside matter, conservation laws for energy, momentum, invariance, form invariance, covariance in special relativity, and more.
Mathematics and electromagnetism
International Nuclear Information System (INIS)
Rodriguez Danta, M.
2000-01-01
Symbiosis between mathematics and electromagnetism is analyzed in a simple and concise manner by taking a historical perspective. The universal tool character of mathematical models allowed the transfer of models from several branches of physics into the realm of electromagnetism by drawing analogies. The mutual interdependence between covariant formulation and tensor calculus is marked. The paper focuses on the guiding idea of field theory and Maxwell's equations. Likewise, geometrization of interactions in connection with gauge fields is also noted. (Author)
The ATLAS electromagnetic calorimeter
Maximilien Brice
2003-01-01
Michel Mathieu, a technician for the ATLAS collaboration, is cabling the ATLAS electromagnetic calorimeter's first end-cap, before insertion into its cryostat. Millions of wires are connected to the electromagnetic calorimeter on this end-cap that must be carefully fed out from the detector so that data can be read out. Every element on the detector will be attached to one of these wires so that a full digital map of the end-cap can be recreated.
Electromagnetic Fields Exposure Limits
2018-01-01
Mr. T.P. (Tjerk) KUIPERS Senior Adviser Health Physics Military Healthcare & Occupational Health Expertise Co-ordination Centre Support...Test of Biological Integrity in Dogs Exposed to an Electromagnetic Pulse Environment”, Health Physics 36:159-165, 1979. [11] Baum, S.J., Ekstrom, M.E...Electromagnetic Radiation”, Health Physics 30:161-166, 1976. [12] Baum, S., Skidmore, W. and Ekstrom, M., “Continuous Exposure of Rodents to 108 Pulses
Electromagnetic Manifestation of Earthquakes
Uvarov Vladimir
2017-01-01
In a joint analysis of the results of recording the electrical component of the natural electromagnetic field of the Earth and the catalog of earthquakes in Kamchatka in 2013, unipolar pulses of constant amplitude associated with earthquakes were identified, whose activity is closely correlated with the energy of the electromagnetic field. For the explanation, a hypothesis about the cooperative character of these impulses is proposed.
Electromagnetic Manifestation of Earthquakes
Directory of Open Access Journals (Sweden)
Uvarov Vladimir
2017-01-01
Full Text Available In a joint analysis of the results of recording the electrical component of the natural electromagnetic field of the Earth and the catalog of earthquakes in Kamchatka in 2013, unipolar pulses of constant amplitude associated with earthquakes were identified, whose activity is closely correlated with the energy of the electromagnetic field. For the explanation, a hypothesis about the cooperative character of these impulses is proposed.
Electromagnetic reverberation chambers
Besnier, Philippe
2013-01-01
Dedicated to a complete presentation on all aspects of reverberation chambers, this book provides the physical principles behind these test systems in a very progressive manner. The detailed panorama of parameters governing the operation of electromagnetic reverberation chambers details various applications such as radiated immunity, emissivity, and shielding efficiency experiments.In addition, the reader is provided with the elements of electromagnetic theory and statistics required to take full advantage of the basic operational rules of reverberation chambers, including calibration proc
Electromagnetic processes and interactions
International Nuclear Information System (INIS)
Scheck, F.
1983-01-01
The electron and muon are important tools in testing the structure of the fundamental electromagnetic interactions. On the other hand, if these interactions are known, they serve as ideal probes for the internal structure of complex hadronic targets such as nucleons and nuclei. Purely electromagnetic interactions play a distinctive role, for obvious experimental reasons: At low and intermediate energies the effective electromagnetic coupling is larger by many orders of magnitude than the weak couplings, so that electromagnetic processes are measurable to much higher accuracy than purely weak processes. The present chapter deals primarily with applications of charged leptons to problems of nucleon and nuclear structure, and to selected precision tests of quantum electrodynamics (QED) at low momentum transfers. In most of these applications the electromagnetic interactions effectively appear in the form of external fields in the leptonic particle's Dirac equation. This is the domain where the physics of (electromagnetically) interacting leptons can still be described in the framework of an effective, though relativistic, single particle theory. (orig.)
Covariant electromagnetic field lines
Hadad, Y.; Cohen, E.; Kaminer, I.; Elitzur, A. C.
2017-08-01
Faraday introduced electric field lines as a powerful tool for understanding the electric force, and these field lines are still used today in classrooms and textbooks teaching the basics of electromagnetism within the electrostatic limit. However, despite attempts at generalizing this concept beyond the electrostatic limit, such a fully relativistic field line theory still appears to be missing. In this work, we propose such a theory and define covariant electromagnetic field lines that naturally extend electric field lines to relativistic systems and general electromagnetic fields. We derive a closed-form formula for the field lines curvature in the vicinity of a charge, and show that it is related to the world line of the charge. This demonstrates how the kinematics of a charge can be derived from the geometry of the electromagnetic field lines. Such a theory may also provide new tools in modeling and analyzing electromagnetic phenomena, and may entail new insights regarding long-standing problems such as radiation-reaction and self-force. In particular, the electromagnetic field lines curvature has the attractive property of being non-singular everywhere, thus eliminating all self-field singularities without using renormalization techniques.
Electromagnetic cellular interactions.
Cifra, Michal; Fields, Jeremy Z; Farhadi, Ashkan
2011-05-01
Chemical and electrical interaction within and between cells is well established. Just the opposite is true about cellular interactions via other physical fields. The most probable candidate for an other form of cellular interaction is the electromagnetic field. We review theories and experiments on how cells can generate and detect electromagnetic fields generally, and if the cell-generated electromagnetic field can mediate cellular interactions. We do not limit here ourselves to specialized electro-excitable cells. Rather we describe physical processes that are of a more general nature and probably present in almost every type of living cell. The spectral range included is broad; from kHz to the visible part of the electromagnetic spectrum. We show that there is a rather large number of theories on how cells can generate and detect electromagnetic fields and discuss experimental evidence on electromagnetic cellular interactions in the modern scientific literature. Although small, it is continuously accumulating. Copyright © 2010 Elsevier Ltd. All rights reserved.
Finite-temperature Casimir effect in the presence of nonlinear dielectrics
DEFF Research Database (Denmark)
Kheirandish, Fardin; Amooghorban, Ehsan; Soltani, Morteza
2011-01-01
Starting from a Lagrangian, the electromagnetic field in the presence of a nonlinear dielectric medium is quantized using path-integral techniques, and correlation functions of different fields are calculated. The susceptibilities of the nonlinear medium are obtained, and their relations to coupl......Starting from a Lagrangian, the electromagnetic field in the presence of a nonlinear dielectric medium is quantized using path-integral techniques, and correlation functions of different fields are calculated. The susceptibilities of the nonlinear medium are obtained, and their relations...
Rotating black string with nonlinear source
International Nuclear Information System (INIS)
Hendi, S. H.
2010-01-01
In this paper, we derive rotating black string solutions in the presence of two kinds of nonlinear electromagnetic fields, so-called Born-Infeld and power Maxwell invariant. Investigation of the solutions show that for the Born-Infeld black string the singularity is timelike and the asymptotic behavior of the solutions is anti-de Sitter, but for power Maxwell invariant solutions, depending on the values of nonlinearity parameter, the singularity may be timelike as well as spacelike and the solutions are not asymptotically anti-de Sitter for all values of the nonlinearity parameter. Next, we calculate the conserved quantities of the solutions by using the counterterm method, and find that these quantities do not depend on the nonlinearity parameter. We also compute the entropy, temperature, the angular velocity, the electric charge, and the electric potential of the solutions, in which the conserved and thermodynamics quantities satisfy the first law of thermodynamics.
Oscillating electromagnetic soliton in an anisotropic ferromagnetic medium
Energy Technology Data Exchange (ETDEWEB)
Sathishkumar, P., E-mail: perumal_sathish@yahoo.co.in [Department of Physics, K.S.R. College of Engineering (Autonomous), Tiruchengode 637215, Tamilnadu (India); Senjudarvannan, R. [Department of Physics, Jansons Institute of Technology, Karumathampatty, Coimbatore 641659 (India)
2017-05-01
We investigate theoretically the propagation of electromagnetic oscillating soliton in the form of breather in an anisotropic ferromagnetic medium. The interaction of magnetization with the magnetic field component of the electromagnetic (EM) wave has been studied by solving Maxwell's equations coupled with a Landau–Lifshitz equation for the magnetization of the medium. We made a small perturbation on the magnetization and magnetic field along the direction of propagation of EM wave in the framework of reductive perturbation method and the associated nonlinear magnetization dynamics is governed by a generalized derivative nonlinear Schrödinger (DNLS) equation. In order to understand the dynamics of the concerned system, we employ the Jacobi elliptic function method to solve the DNLS equation and deduce breatherlike soliton modes for the EM wave in the medium. - Highlights: • The propagation of electromagnetic oscillating soliton in an anisotropic ferromagnetic medium is investigated in the presence of varying external magnetic field. • The magnetization and electromagnetic wave modulates in the form of breathing like oscillating solitons. • The governing nonlinear spin dynamical equation is studied through a reductive perturbation method. • The magnetization components of the ferromagnetic medium are derived using Jacobi elliptic functions method with the aid of symbolic computation.
Scalar, electromagnetic, and gravitational fields interaction: Particlelike solutions
International Nuclear Information System (INIS)
Bronnikov, K.A.; Melnikov, V.N.; Shikin, G.N.; Staniukovich, K.P.
1979-01-01
Particlelike static spherically symmetric solutions to massless scalar and electromagnetic field equations combined with gravitational field equations are considered. Two criteria for particlelike solutions are formulated: the strong one (solutions are required to be singularity free) and the weak one (singularities are admitted but the total energy and material field energy should be finite). Exact solutions for the following physical systems are considered with their own gravitational field: (i) linear scalar (minimally coupled or conformal) plus electromagnetic field; (ii) the same fields with a bare mass source in the form of charged incoherent matter distributions; (iii) nonlinear electromagnetic field with an abritrary dependence on the invariant F/sub alphabeta/F/sup alphabeta/; and (iv) directly interacting scalar and electromagnetic fields. Case (i) solutions are not particlelike (except those with horizons, in which static regions formally satisfy the weak criterion). For systems (ii), examples of nonsingular models are constructed, in particular, a model for a particle--antiparticle pair of a Wheeler-handle type, without scalar field and explict electric charges. Besides, a number of limitations upon nonsingular model parameters is indicated. Systems (iii) are proved to violate the strong criterion for any type of nonlinearity but can satisfy the weak criterion (e.g., the Born--Infeld nonlinearity). For systems (iv) some particlelike solutions by the weak criterion are constructed and a regularizing role of gravitation is demonstrated. Finally, an example of a field system satisfying the strong criterion is given
Nonlinear inertial Alfven waves in plasmas with sheared magnetic field and flow
International Nuclear Information System (INIS)
Chen Yinhua; Wang Ge; Tan Liwei
2004-01-01
Nonlinear equations describing inertial Alfven waves in plasmas with sheared magnetic field and flow are derived. For some specific parameters chosen, authors have found a new type of electromagnetic coherent structures in the tripolar vortex-like form
Ku, S.; Chang, C. S.; Hager, R.; Churchill, R. M.; Tynan, G. R.; Cziegler, I.; Greenwald, M.; Hughes, J.; Parker, S. E.; Adams, M. F.; D'Azevedo, E.; Worley, P.
2018-05-01
A fast edge turbulence suppression event has been simulated in the electrostatic version of the gyrokinetic particle-in-cell code XGC1 in a realistic diverted tokamak edge geometry under neutral particle recycling. The results show that the sequence of turbulent Reynolds stress followed by neoclassical ion orbit-loss driven together conspire to form the sustaining radial electric field shear and to quench turbulent transport just inside the last closed magnetic flux surface. The main suppression action is located in a thin radial layer around ψN≃0.96 -0.98 , where ψN is the normalized poloidal flux, with the time scale ˜0.1 ms.
Energy Technology Data Exchange (ETDEWEB)
Ku, S [Courant Institute of Mathematical Sciences, New York University (United States); Chang, C-S [Courant Institute of Mathematical Sciences, New York University (United States); Adams, M [Columbia University (United States); Cummings, J [California Institute of Technology (United States); Hinton, F [Hinton Associates (United States); Keyes, D [Columbia University (United States); Klasky, S [Oak Ridge National Laboratory (United States); Lee, W [Princeton Plasma Physics Laboratory (United States); Lin, Z [University of California at Irvine (United States); Parker, S [University of Colorado at Boulder (United States)
2006-09-15
A gyrokinetic neoclassical solution for a diverted tokamak edge plasma has been obtained for the first time using the massively parallel Jaguar XT3 computer at Oak Ridge National Laboratory. The solutions show similar characteristics to the experimental observations: electric potential is positive in the scrape-off layer and negative in the H-mode layer, and the parallel rotation is positive in the scrape-off layer and at the inside boundary of the H-mode layer. However, the solution also makes a new physical discovery that there is a strong ExB convective flow in the scrape-off plasma. A general introduction to the edge simulation problem is also presented.
Klein, R.; Gravier, E.; Morel, P.; Besse, N.; Bertrand, P.
2009-08-01
Describing turbulent transport in fusion plasmas is a major concern in magnetic confinement fusion. It is now widely known that kinetic and fluid descriptions can lead to significantly different properties. Although more accurate, the kinetic calculation of turbulent transport is much more demanding of computer resources than fluid simulations. An alternative approach is based on a water-bag representation of the distribution function that is not an approximation but rather a special class of initial conditions, allowing one to reduce the full kinetic Vlasov equation into a set of hydrodynamics equations while keeping its kinetic character [P. Morel, E. Gravier, N. Besse et al., Phys. Plasmas 14, 112109 (2007)]. In this paper, the water-bag concept is used in a gyrokinetic context to study finite Larmor radius effects with the possibility of using the full Larmor radius distribution instead of an averaged Larmor radius. The resulting model is used to study the ion temperature gradient (ITG) instability.
Cross-separatrix Coupling in Nonlinear Global Electrostatic Turbulent Transport in C-2U
Lau, Calvin; Fulton, Daniel; Bao, Jian; Lin, Zhihong; Binderbauer, Michl; Tajima, Toshiki; Schmitz, Lothar; TAE Team
2017-10-01
In recent years, the progress of the C-2/C-2U advanced beam-driven field-reversed configuration (FRC) experiments at Tri Alpha Energy, Inc. has pushed FRCs to transport limited regimes. Understanding particle and energy transport is a vital step towards an FRC reactor, and two particle-in-cell microturbulence codes, the Gyrokinetic Toroidal Code (GTC) and A New Code (ANC), are being developed and applied toward this goal. Previous local electrostatic GTC simulations find the core to be robustly stable with drift-wave instability only in the scrape-off layer (SOL) region. However, experimental measurements showed fluctuations in both regions; one possibility is that fluctuations in the core originate from the SOL, suggesting the need for non-local simulations with cross-separatrix coupling. Current global ANC simulations with gyrokinetic ions and adiabatic electrons find that non-local effects (1) modify linear growth-rates and frequencies of instabilities and (2) allow instability to move from the unstable SOL to the linearly stable core. Nonlinear spreading is also seen prior to mode saturation. We also report on the progress of the first turbulence simulations in the SOL. This work is supported by the Norman Rostoker Fellowship.
Gyrokinetic Electron and Fully Kinetic Ion Particle Simulation of Collisionless Plasma Dynamics
Energy Technology Data Exchange (ETDEWEB)
Yu Lin; Xueyi Wang; Liu Chen; Zhihong Lin
2009-08-11
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
Gyrokinetic Electron and Fully Kinetic Ion Particle Simulation of Collisionless Plasma Dynamics
International Nuclear Information System (INIS)
Lin, Yu; Wang, Xueyi; Chen, Liu; Lin, Zhihong
2009-01-01
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
Electromagnetic radiation optimum neutralizer
International Nuclear Information System (INIS)
Smirnov, Igor
2002-01-01
This particular article relates to subtle electrical effects, and provides some evidence of a fundamental nature on how subtle low frequency electromagnetic fields might be utilized to protect human body against harmful effects of high frequencies electromagnetic radiation. I have focused my efforts on definite polar polymer compound named EMRON which is patented in the USA. This polar polymer compound can be excited by external high frequencies electromagnetic fields to generate subtle low frequency oscillations that are beneficial for cellular life structures. This concept is based on the possibility of existence of resonance phenomenon between polar polymers and biopolymers such as proteins, nucleic acids, lipids, etc. Low frequency patterns generated by defined polar polymer compound can interact with biostructures and transmit the signals that support and improve cellular functions in the body. The mechanism of this process was confirmed by number of studies. The animal (including human) brain is affected by electromagnetic waves to the extent that production of Alpha or Theta waves can be directly induced into brain by carrying an ELF (extremely low frequency, 5-12 Hz) signal on a microwave carrier frequency. EMRON does not reduce the power of electromagnetic fields. It 'shields' the cellular structures of the body against the harmful effects of EMR. The radiation is still entering the body but the neutralizing effect of EMRON renders the radiation harmless
4th International Conference on Nonlinear Mechanics
Maugin, G
2003-01-01
The mechanics of electromagnetic materials and structures has been developing rapidly with extensive applications in, e. g. , electronics industry, nuclear engineering, and smart materials and structures. Researchers in this interdisciplinary field are with diverse background and motivation. The Symposium on the Mechanics of Electromagnetic Materials and Structures of the Fourth International Conference on Nonlinear Mechanics in Shanghai, China in August 13-16, 2002 provided an opportunity for an intimate gathering of researchers and exchange of ideas. This volume contains papers based on most of the presentations at the symposium, and articles from a few invited contributors. These papers reflect some of the recent activities in the mechanics of electromagnetic materials and structures. The first twelve papers are in the order in which they were listed in the program of the conference. These are followed by six invited papers in alphabetical order of the last names of the first authors. We would like to exte...
Nonlinear Elliptic Differential Equations with Multivalued Nonlinearities
Indian Academy of Sciences (India)
In this paper we study nonlinear elliptic boundary value problems with monotone and nonmonotone multivalued nonlinearities. First we consider the case of monotone nonlinearities. In the first result we assume that the multivalued nonlinearity is defined on all R R . Assuming the existence of an upper and of a lower ...
Electromagnetic fields and their impacts
Prša, M. A.; Kasaš-Lažetić, K. K.
2018-01-01
The main goal of this paper is to briefly recall some different electromagnetic field definitions, some macroscopic sources of electromagnetic fields, electromagnetic fields classification regarding time dependences, and the ways of field determination in concrete cases. After that, all the mechanisms of interaction between electromagnetic field and substance, on atomic level, are described in details. Interaction between substance and electric field is investigated separately from the substance and magnetic field interaction. It is demonstrated that, in all cases of the unique electromagnetic field, total interaction can be treated as a superposition of two separated interactions. Finally, the main electromagnetic fields surrounding us is cited and discussed.
Gravitation and electromagnetism
Apsel, D
1979-01-01
Through an examination of the Bohm-Aharonov experiment, a new theory of gravitation and electromagnetism is proposed. The fundamental assumption of the theory is that the motion of a particle in a combination of gravitational and electromagnetic fields is determined from a variational principle of the form delta integral /sub A//sup B /d tau =0. The form of the physical time is determined from an examination of the Maxwell-Einstein action function. The field and motion equations are formally identical to those of Maxwell-Einstein theory. The theory predicts that even in a field-free region of space, electromagnetic potentials can alter the phase of a wave function and the lifetime of a charged particle. The phase alteration has been observed in the Bohm-Aharonov experiment. There is an indication that the lifetime alteration has shown up in a recent CERN storage ring experiment. Experimental tests are proposed. (11 refs).
Applied electromagnetic scattering theory
Osipov, Andrey A
2017-01-01
Besides classical applications (radar and stealth, antennas, microwave engineering), scattering and diffraction are enabling phenomena for some emerging research fields (artificial electromagnetic materials or metamaterials, terahertz technologies, electromagnetic aspects of nano-science). This book is a tutorial for advanced students who need to study diffraction theory. The textbook gives fundamental knowledge about scattering and diffraction of electromagnetic waves and provides some working examples of solutions for practical high-frequency scattering and diffraction problems. The book focuses on the most important diffraction effects and mechanisms influencing the scattering process and describes efficient and physically justified simulation methods - physical optics (PO) and the physical theory of diffraction (PTD) - applicable in typical remote sensing scenarios. The material is presented in a comprehensible and logical form, which relates the presented results to the basic principles of electromag...
Metamaterial electromagnetic wave absorbers.
Watts, Claire M; Liu, Xianliang; Padilla, Willie J
2012-06-19
The advent of negative index materials has spawned extensive research into metamaterials over the past decade. Metamaterials are attractive not only for their exotic electromagnetic properties, but also their promise for applications. A particular branch-the metamaterial perfect absorber (MPA)-has garnered interest due to the fact that it can achieve unity absorptivity of electromagnetic waves. Since its first experimental demonstration in 2008, the MPA has progressed significantly with designs shown across the electromagnetic spectrum, from microwave to optical. In this Progress Report we give an overview of the field and discuss a selection of examples and related applications. The ability of the MPA to exhibit extreme performance flexibility will be discussed and the theory underlying their operation and limitations will be established. Insight is given into what we can expect from this rapidly expanding field and future challenges will be addressed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Radiation from nonlinear coupling of plasma waves
International Nuclear Information System (INIS)
Fung, S.F.
1986-01-01
The author examines the generation of electromagnetic radiation by nonlinear resonant interactions of plasma waves in a cold, uniformly magnetized plasma. In particular, he considers the up-conversion of two electrostatic wave packets colliding to produce high frequency electromagnetic radiation. Efficient conversion of electrostatic to electromagnetic wave energy occurs when the pump amplitudes approach and exceed the pump depletion threshold. Results from the inverse scattering transform analysis of the three-wave interaction equations are applied. When the wave packets are initially separated, the fully nonlinear set of coupling equations, which describe the evolution of the wave packets, can be reduced to three separate eigenvalue problems; each can be considered as a scattering problem, analogous to eh Schroedinger equation. In the scattering space, the wave packet profiles act as the scattering potentials. When the wavepacket areas approach (or exceed) π/2, the wave functions are localized (bound states) and the scattering potentials are said to contain solitons. Exchange of solitons occurs during the interaction. The transfer of solitons from the pump waves to the electromagnetic wave leads to pump depletion and the production of strong radiation. The emission of radio waves is considered by the coupling of two upper-hybrid branch wave packets, and an upper-hybrid and a lower hybrid branch wave packet
Electromagnetic solitary vortices in rotating plasma
International Nuclear Information System (INIS)
Liu, J.; Horton, W.
1985-12-01
The nonlinear equations describing drift-Alfven solitary vortices in a low β, rotating plasma are derived. Two types of solitary vortex solutions along with their corresponding nonlinear dispersion relations are obtained. Both solutions have the localized coherent dilopar structure. The first type of solution belongs to the family of the usual Rossby or drift wave vortex, while the second type of solution is intrinsic to the electromagnetic perturbation in a magnetized plasma and is a complicated structure. While the first type of vortex is a solution to a second order differential equation the second one is the solution of a fourth order differential equation intrinsic to the electromagnetic problem. The fourth order vortex solution has two intrinsic space scales in contrast to the single space scale of the previous drift vortex solution. With the second short scale length the parallel current density at the vortex interface becomes continuous. As special cases the rotational electron drift vortex and the rotational ballooning vortex also are given. 10 refs
Intrinsic electromagnetic solitary vortices in magnetized plasma
International Nuclear Information System (INIS)
Liu, J.; Horton, W.
1986-01-01
Several Rossby type vortex solutions constructed for electromagnetic perturbations in magnetized plasma encounter the difficulty that the perturbed magnetic field and the parallel current are not continuous on the boundary between two regions. We find that fourth order differential equations must be solved to remove this discontinuity. Special solutions for two types of boundary value problems for the fourth order partial differential equations are presented. By applying these solutions to different nonlinear equations in magnetized plasma, the intrinsic electromagnetic solitary drift-Alfven vortex (along with solitary Alfven vortex) and the intrinsic electromagnetic solitary electron vortex (along with short-wavelength drift vortex) are constructed. While still keeping a localized dipole structure, these new vortices have more complicated radial structures in the inner and outer regions than the usual Rossby wave vortex. The new type of vortices guarantees the continuity of the perturbed magnetic field deltaB/sub perpendicular/ and the parallel current j/sub parallel/ on the boundary between inner and outer regions of the vortex. The allowed regions of propagation speeds for these vortices are analyzed, and we find that the complementary relation between the vortex propagating speeds and the corresponding phase velocities of the linear modes no longer exists
Coherent polarization driven by external electromagnetic fields
International Nuclear Information System (INIS)
Apostol, M.; Ganciu, M.
2010-01-01
The coherent interaction of the electromagnetic radiation with an ensemble of polarizable, identical particles with two energy levels is investigated in the presence of external electromagnetic fields. The coupled non-linear equations of motion are solved in the stationary regime and in the limit of small coupling constants. It is shown that an external electromagnetic field may induce a macroscopic occupation of both the energy levels of the particles and the corresponding photon states, governed by a long-range order of the quantum phases of the internal motion (polarization) of the particles. A lasing effect is thereby obtained, controlled by the external field. Its main characteristics are estimated for typical atomic matter and atomic nuclei. For atomic matter the effect may be considerable (for usual external fields), while for atomic nuclei the effect is extremely small (practically insignificant), due to the great disparity in the coupling constants. In the absence of the external field, the solution, which is non-analytic in the coupling constant, corresponds to a second-order phase transition (super-radiance), which was previously investigated.
The theory of electromagnetism
Jones, D S
1964-01-01
The Theory of the Electomagnetism covers the behavior of electromagnetic fields and those parts of applied mathematics necessary to discover this behavior. This book is composed of 11 chapters that emphasize the Maxwell's equations. The first chapter is concerned with the general properties of solutions of Maxwell's equations in matter, which has certain macroscopic properties. The succeeding chapters consider specific problems in electromagnetism, including the determination of the field produced by a variable charge, first in isolation and then in the surface distributions of an antenna. The
Das, Ashok
2013-01-01
These lecture notes on electromagnetism have evolved from graduate and undergraduate EM theory courses given by the author at the University of Rochester, with the basics presented with clarity and his characteristic attention to detail. The thirteen chapters cover, in logical sequence, topics ranging from electrostatics, magnetostatics and Maxwell's equations to plasmas and radiation. Boundary value problems are treated extensively, as are wave guides, electromagnetic interactions and fields. This second edition comprises many of the topics expanded with more details on the derivation of vari
Electromagnetic clutches and couplings
Vorob'Yeva, T M; Fry, D W; Higinbotham, W
2013-01-01
Electromagnetic Clutches and Couplings contains a detailed description of U.S.S.R. electromagnetic friction clutches, magnetic couplings, and magnetic particle couplings. This book is divided into four chapters. The first chapter discusses the design and construction of magnetic (solenoid-operated) couplings, which are very quick-acting devices and used in low power high-speed servo-systems. Chapter 2 describes the possible fields of application, design, construction, and utilization of magnetic particle couplings. The aspects of construction, design, and utilization of induction clutches (sli
Improved Electromagnetic Brake
Martin, Toby B.
2004-01-01
A proposed design for an electromagnetic brake would increase the reliability while reducing the number of parts and the weight, relative to a prior commercially available electromagnetic brake. The reductions of weight and the number of parts could also lead to a reduction of cost. A description of the commercial brake is prerequisite to a description of the proposed electromagnetic brake. The commercial brake (see upper part of figure) includes (1) a permanent magnet and an electromagnet coil on a stator and (2) a rotor that includes a steel contact plate mounted, with tension spring loading, on an aluminum hub. The stator is mounted securely on a stationary object, which would ordinarily be the housing of a gear drive or a motor. The rotor is mounted on the shaft of the gear drive or motor. The commercial brake nominally operates in a fail-safe (in the sense of normally braking) mode: In the absence of current in the electromagnet coil, the permanent magnet pulls the contact plate, against the spring tension, into contact with the stator. To release the brake, one excites the electromagnet with a current of the magnitude and polarity chosen to cancel the magnetic flux of the permanent magnet, thereby enabling the spring tension to pull the contact plate out of contact with the stator. The fail-safe operation of the commercial brake depends on careful mounting of the rotor in relation to the stator. The rotor/stator gap must be set with a tolerance between 10 and 15 mils (between about 0.25 and about 0.38 mm). If the gap or the contact pad is thicker than the maximum allowable value, then the permanent magnetic field will not be strong enough to pull the steel plate across the gap. (For this reason, any contact pad between the contact plate and the stator must also be correspondingly thin.) If the gap exceeds the maximum allowable value because of shaft end play, it becomes impossible to set the brake by turning off the electromagnet current. Although it may
Essentials of Computational Electromagnetics
Sheng, Xin-Qing
2012-01-01
Essentials of Computational Electromagnetics provides an in-depth introduction of the three main full-wave numerical methods in computational electromagnetics (CEM); namely, the method of moment (MoM), the finite element method (FEM), and the finite-difference time-domain (FDTD) method. Numerous monographs can be found addressing one of the above three methods. However, few give a broad general overview of essentials embodied in these methods, or were published too early to include recent advances. Furthermore, many existing monographs only present the final numerical results without specifyin
Electromagnetic Fields in Reverberant Environments
Vogt-Ardatjew, Robert Andrzej
2017-01-01
The phenomenon of resonating electromagnetic (EM) fields has been commonly and successfully exploited in reverberation chambers (RC) for the purpose of electromagnetic compatibility (EMC) testing, as well as modeling multipath environments. Although largely successful, the currently used statistical
New perspectives on classical electromagnetism
Cote, Paul J.
2009-01-01
The fallacies associated with the gauge concept in electromagnetism are illustrated. A clearer and more valid formulation of the basics of classical electromagnetism is provided by recognizing existing physical constraints as well as the physical reality of the vector potential.
Electromagnetic fields in stratified media
Li, Kai
2009-01-01
Dealing with an important branch of electromagnetic theory with many useful applications in subsurface communication, radar, and geophysical prospecting and diagnostics, this book introduces electromagnetic theory and wave propagation in complex media.
Electromagnetic interference: a radiant future!
Leferink, Frank Bernardus Johannes
2015-01-01
Although Electromagnetic Interference and Electromagnetic Compatibility are well established domains, the introduction of new technologies results in new challenges. Changes in both measurement techniques, and technological trends resulting in new types of interference are described. These are the
Study of large nonlinear change phase in Hibiscus Sabdariffa
Trejo-Durán, M.; Alvarado-Méndez, E.; Andrade-Lucio, J. A.; Rojas-Laguna, R.; Vázquez-Guevara, M. A.
2015-09-01
High intensities electromagnetic energy interacting with organic media gives rise to nonlinear optical effects. Hibiscus Sabdariffa is a flower whose concentrated solution presents interesting nonlinear optical properties. This organic material shows an important self-phase modulation with changes bigger than 2π. We present a diffraction ring patterns study of the Hibiscus Sabdariffa solution. Numerical results of transmittance, with refraction and simultaneous absorption, are shown.
Nonlinear Flow Generation By Electrostatic Turbulence In Tokamaks
International Nuclear Information System (INIS)
Wang, W.X.; Diamond, P.H.; Hahm, T.S.; Ethier, S.; Rewoldt, G.; Tang, W.M.
2010-01-01
Global gyrokinetic simulations have revealed an important nonlinear flow generation process due to the residual stress produced by electrostatic turbulence of ion temperature gradient (ITG) modes and trapped electron modes (TEM). In collisionless TEM (CTEM) turbulence, nonlinear residual stress generation by both the fluctuation intensity and the intensity gradient in the presence of broken symmetry in the parallel wave number spectrum is identified for the first time. Concerning the origin of the symmetry breaking, turbulence self-generated low frequency zonal flow shear has been identified to be a key, universal mechanism in various turbulence regimes. Simulations reported here also indicate the existence of other mechanisms beyond E - B shear. The ITG turbulence driven 'intrinsic' torque associated with residual stress is shown to increase close to linearly with the ion temperature gradient, in qualitative agreement with experimental observations in various devices. In CTEM dominated regimes, a net toroidal rotation is driven in the cocurrent direction by 'intrinsic' torque, consistent with the experimental trend of observed intrinsic rotation. The finding of a 'flow pinch' in CTEM turbulence may offer an interesting new insight into the underlying dynamics governing the radial penetration of modulated flows in perturbation experiments. Finally, simulations also reveal highly distinct phase space structures between CTEM and ITG turbulence driven momentum, energy and particle fluxes, elucidating the roles of resonant and non-resonant particles.
Nonlinear mechanisms for drift wave saturation and induced particle transport
International Nuclear Information System (INIS)
Dimits, A.M.; Lee, W.W.
1989-12-01
A detailed theoretical study of the nonlinear dynamics of gyrokinetic particle simulations of electrostatic collisionless and weakly collisional drift waves is presented. In previous studies it was shown that, in the nonlinearly saturated phase of the evolution, the saturation levels and especially the particle fluxes have an unexpected dependence on collisionality. In this paper, the explanations for these collisionality dependences are found to be as follows: The saturation level is determined by a balance between the electron and ion fluxes. The ion flux is small for levels of the potential below an E x B-trapping threshold and increases sharply once this threshold is crossed. Due to the presence of resonant electrons, the electron flux has a much smoother dependence on the potential. In the 2-1/2-dimensional (''pseudo-3D'') geometry, the electrons are accelerated away from the resonance as they diffuse spatially, resulting in an inhibition of their diffusion. Collisions and three-dimensional effects can repopulate the resonance thereby increasing the value of the particle flux. 30 refs., 32 figs., 2 tabs
Low frequency electromagnetic field sensor
International Nuclear Information System (INIS)
Zhu Min; Zhou Yan; He Yicheng; Zheng Zhenxing; Liu Sunkun
2000-01-01
The measurement technique of low frequency electromagnetic field is reported. According to this principle, the authors have designed a sensor, which is used to measure the natural electromagnetic field, SLEMP and electromagnetic signals generated by some explosions. The frequency band of this sensor is from 0.08 Hz to 2 MHz
Electromagnetic radiation detector
Benson, Jay L.; Hansen, Gordon J.
1976-01-01
An electromagnetic radiation detector including a collimating window, a cathode member having a photoelectric emissive material surface angularly disposed to said window whereby radiation is impinged thereon at acute angles, an anode, separated from the cathode member by an evacuated space, for collecting photoelectrons emitted from the emissive cathode surface, and a negatively biased, high transmissive grid disposed between the cathode member and anode.
Disconnected electromagnetic form factors
International Nuclear Information System (INIS)
Wilcox, Walter
2001-01-01
Preliminary results of a calculation of disconnected nucleon electromagnetic factors factors on the lattice are presented. The implementation of the numerical subtraction scheme is outlined. A comparison of results for electric and magnetic disconnected form factors on two lattice sizes with those of the Kentucky group is presented. Unlike previous results, the results found in this calculation are consistent with zero in these sectors
Electromagnetic distance measurement
1967-01-01
This book brings together the work of forty-eight geodesists from twenty-five countries. They discuss various new electromagnetic distance measurement (EDM) instruments - among them the Tellurometer, Geodimeter, and air- and satellite-borne systems - and investigate the complex sources of error.
Equivalence principles and electromagnetism
Ni, W.-T.
1977-01-01
The implications of the weak equivalence principles are investigated in detail for electromagnetic systems in a general framework. In particular, it is shown that the universality of free-fall trajectories (Galileo weak equivalence principle) does not imply the validity of the Einstein equivalence principle. However, the Galileo principle plus the universality of free-fall rotation states does imply the Einstein principle.
Electromagnetic Environments Simulator (EMES)
International Nuclear Information System (INIS)
Varnado, G.B.
1975-11-01
A multipurpose electromagnetic environments simulator has been designed to provide a capability for performing EMR, EMP, and lightning near stroke testing of systems, subsystems and components in a single facility. This report describes the final facility design and presents the analytical and experimental verification of the design
Pregnancy and electromagnetic fields
International Nuclear Information System (INIS)
Bisseriex, Ch.; Laurent, P.; Cabaret, Ph.; Bonnet, C.; Marteau, E.; Le Berre, G.; Tirlemont, S.; Castro, H.; Becker, A.; Demaret, Ph.; Donati, M.; Ganem, Y.; Moureaux, P.
2011-07-01
This document briefly indicates the status of knowledge regarding the effect of magnetic fields on biological tissues and pregnancy, outlines the lack of data on some frequencies and the weakness of studies on long term effects on child development. It evokes the issue of exposure assessment and that of identification of workstations exposed to electromagnetic fields
Electromagnetic structure of nuclei
International Nuclear Information System (INIS)
Arnold, R.G.
1986-07-01
A brief review is given of selected topics in the electromagnetic structure of nucleons and nuclei, including nucleon form factors from both quantum chromodynamics and electron scattering data, measurements of the deuteron and triton form factors, quasi-elastic scattering, and the EMC effect. 47 refs., 13 figs
"Hearing" Electromagnetic Waves
Rojo, Marta; Munoz, Juan
2014-01-01
In this work, an educational experience is described in which a microwave communication link is used to make students aware that all electromagnetic waves have the same physical nature and properties. Experimental demonstrations are linked to theoretical concepts to increase comprehension of the physical principles underlying electromagnetic…
Electromagnetic resonance waves
International Nuclear Information System (INIS)
Villaba, J.M.; Manjon, F.J.; Guirao, A.; Andres, M.V.
1994-01-01
We describe in this paper a set of experiments designed to make qualitative and quantitative measurements on electromagnetic resonances of several simple systems. The experiments are designed for the undergraduate laboratory of Electricity and Magnetism in Physics. These experiments can help the students understanding the concept of resonance, which appears in different fields of Physics. (Author) 8 refs
Fu, Y. B.; Ogden, R. W.
2001-05-01
This collection of papers by leading researchers in the field of finite, nonlinear elasticity concerns itself with the behavior of objects that deform when external forces or temperature gradients are applied. This process is extremely important in many industrial settings, such as aerospace and rubber industries. This book covers the various aspects of the subject comprehensively with careful explanations of the basic theories and individual chapters each covering a different research direction. The authors discuss the use of symbolic manipulation software as well as computer algorithm issues. The emphasis is placed firmly on covering modern, recent developments, rather than the very theoretical approach often found. The book will be an excellent reference for both beginners and specialists in engineering, applied mathematics and physics.
Rajasekar, Shanmuganathan
2016-01-01
This introductory text presents the basic aspects and most important features of various types of resonances and anti-resonances in dynamical systems. In particular, for each resonance, it covers the theoretical concepts, illustrates them with case studies, and reviews the available information on mechanisms, characterization, numerical simulations, experimental realizations, possible quantum analogues, applications and significant advances made over the years. Resonances are one of the most fundamental phenomena exhibited by nonlinear systems and refer to specific realizations of maximum response of a system due to the ability of that system to store and transfer energy received from an external forcing source. Resonances are of particular importance in physical, engineering and biological systems - they can prove to be advantageous in many applications, while leading to instability and even disasters in others. The book is self-contained, providing the details of mathematical derivations and techniques invo...
Gauge theory of weak, electromagnetic and dual electromagnetic interactions
International Nuclear Information System (INIS)
Soln, J.
1980-01-01
An SU 2 x U 1 algebra, in addition to the ordinary electric charge, also establishes the existence of the dual electric charge. This is taken as an indication of the existence of dual electromagnetic interactions in nature. Here, the unification of weak, electromagnetic and dual electromagnetic interactions is performed. The Yang-Mills-type group which contains the electromagnetic, dual electromagnetic and weak currents is SUsub(L,2) x U 1 x U' 1 . The masses of vector mesons are generated through the Higgs-Kibble mechanism. A simple consistency requirement suggests that dual electromagnetism and ordinary electromagnetism have the same strengths, leading the theory to a rather good agreement with experiments. (author)
Coherent nonlinear electromagnetic response in twisted bilayer and ...
Indian Academy of Sciences (India)
The phenomenon of Rabi oscillations far from resonance is described in bilayer and few-layer graphene. These oscillations in the population and polarization at the Dirac point in -layer graphene are seen in the nth harmonic termin the external driving frequency. The underlying reason behind these oscillations is ...
Preconditioned Inexact Newton for Nonlinear Sparse Electromagnetic Imaging
Desmal, Abdulla; Bagci, Hakan
2014-01-01
with smoothness promoting optimization/regularization schemes. However, this type of regularization schemes are known to perform poorly when applied in imagining domains with sparse content or sharp variations. In this work, an inexact Newton algorithm
Coherent nonlinear electromagnetic response in twisted bilayer and ...
Indian Academy of Sciences (India)
done theoretically and experimentally on multilayer graphene (MLG) as well, which is ... (a) Honeycomb lattice structure of BLG containing four atoms per unit cell: ..... This is especially important in doped systems where a finite den- ..... [9] A Luican, G Li, A Reina, J Kong, R Nair, K S Novoselov, A K Geim and E Andrei, Phys.
Energy Recovery from a Non-Linear Electromagnetic System
Directory of Open Access Journals (Sweden)
Kęcik Krzysztof
2018-03-01
Full Text Available The paper presents study of a pseudo-magnetic levitation system (pseudo-maglev dedicated for energy harvesting. The idea rely on motion of a pseudo-levitating magnet in a coil’s terminal. The study based on real prototype harvester system, which in the pendulum dynamic vibration absorber is applied. For some parameters, the stability loss caused by the period doubling bifurcation is detected. The coexistence of two stable solutions, one of which is much better for energy harvesting is observed. The influence of the pseudo-maglev parameters on the recovered current and stability of the periodic solutions is presented in detail. The obtained results show, that the best energy recovery occurs for the high pseudo-maglev stiffness and close to the coil resistance. The amplitude’s excitation, the load resistances and the coupling coefficient strongly influence on the system’s response.
Sparse Nonlinear Electromagnetic Imaging Accelerated With Projected Steepest Descent Algorithm
Desmal, Abdulla; Bagci, Hakan
2017-01-01
steepest descent algorithm. The algorithm uses a projection operator to enforce the sparsity constraint by thresholding the solution at every iteration. Thresholding level and iteration step are selected carefully to increase the efficiency without
Energy Technology Data Exchange (ETDEWEB)
Sagdeev, R Z
1984-01-01
The results of theoretical and experimental investigations of nonlinear and turbulent phenomena from a wide range of fields in physics are presented in reviews and reports. Topics examined include localized vortex formations in an ideal fluid, phase transitions in crystals, spatially nonuniform structures in condensed matter, solitons in molecular systems, the migration of quasi-particles in easily deformed crystals, bifurcations and dissipative structures in distributed kinetic systems, and structures in a nonlinear burning medium. Consideration is given to macroscopic motion generation in nonequilibrium media, the interaction of bulk and surface wave trains, near-threshold instabilities in hydrodynamics, solitons in nonlinear elastic rods with variable characteristics, the generation of solitons and vortices from chaos, and nonlinear electromagnetic-wave dissipation in an electron system.
Electromagnetic effects on plasma blob-filament transport
Energy Technology Data Exchange (ETDEWEB)
Lee, Wonjae, E-mail: wol023@ucsd.edu [University of California, San Diego, La Jolla, CA (United States); Angus, J.R. [Naval Research Laboratory, Washington, DC (United States); Umansky, Maxim V. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Krasheninnikov, Sergei I. [University of California, San Diego, La Jolla, CA (United States); Nuclear Research National University MEPhI, Moscow 115409 (Russian Federation)
2015-08-15
Both microscopic and macroscopic impacts of the electromagnetic effects on blob dynamics are considered. Linear stability analysis and nonlinear BOUT++ simulations demonstrate that electromagnetic effects in high temperature or high beta plasmas suppress the resistive drift wave turbulence in the blob when resistivity drops below a certain value. In the course of blob’s motion in the SOL its temperature is reduced, which leads to enhancement of resistive effects, so the blob can switch from electromagnetic to electrostatic regime, where resistive drift wave turbulence become important. It is found that inhomogeneity of magnetic curvature or plasma pressure along the filament length leads to bending of the high-beta blob filaments. This is caused by the increase of the propagation time of plasma current (Alfvén time) in higher-density plasma. The effects of sheath boundary conditions on the part of the blob away from the boundary are also diminished by the increased Alfvén time.
Vibration control of a flexible structure with electromagnetic actuators
DEFF Research Database (Denmark)
Gruzman, Maurício; Santos, Ilmar
2016-01-01
This work presents the model of a shear-frame-type structure composed of six flexible beams and three rigid masses. Fixed on the ground, outside the structure, two voltage-controlled electromagnetic actuators are used for vibration control. To model the flexible beams, unidimensional finite...... elements were used. Nonlinear equations for the actuator electromagnetic force, noise in the position sensor, time delays for the control signal update and voltage saturation were also considered in the model. For controlling purposes, a discrete linear quadratic regulator combined with a predictive full......-order discrete linear observer was employed. Results of numerical simulations, where the structure is submitted to an impulsive disturbance force and to a harmonic force, show that the oscillations can be significantly reduced with the use of the electromagnetic actuators....
Spectral properties of electromagnetic turbulence in plasmas
Directory of Open Access Journals (Sweden)
D. Shaikh
2009-03-01
Full Text Available We report on the nonlinear turbulent processes associated with electromagnetic waves in plasmas. We focus on low-frequency (in comparison with the electron gyrofrequency nonlinearly interacting electron whistlers and nonlinearly interacting Hall-magnetohydrodynamic (H-MHD fluctuations in a magnetized plasma. Nonlinear whistler mode turbulence study in a magnetized plasma involves incompressible electrons and immobile ions. Two-dimensional turbulent interactions and subsequent energy cascades are critically influenced by the electron whisters that behave distinctly for scales smaller and larger than the electron skin depth. It is found that in whistler mode turbulence there results a dual cascade primarily due to the forward spectral migration of energy that coexists with a backward spectral transfer of mean squared magnetic potential. Finally, inclusion of the ion dynamics, resulting from a two fluid description of the H-MHD plasma, leads to several interesting results that are typically observed in the solar wind plasma. Particularly in the solar wind, the high-time-resolution databases identify a spectral break at the end of the MHD inertial range spectrum that corresponds to a high-frequency regime. In the latter, turbulent cascades cannot be explained by the usual MHD model and a finite frequency effect (in comparison with the ion gyrofrequency arising from the ion inertia is essentially included to discern the dynamics of the smaller length scales (in comparison with the ion skin depth. This leads to a nonlinear H-MHD model, which is presented in this paper. With the help of our 3-D H-MHD code, we find that the characteristic turbulent interactions in the high-frequency regime evolve typically on kinetic-Alfvén time-scales. The turbulent fluctuation associated with kinetic-Alfvén interactions are compressive and anisotropic and possess equipartition of the kinetic and magnetic energies.
Wave propagation in electromagnetic media
International Nuclear Information System (INIS)
Davis, J.L.
1990-01-01
This book is concerned with wave propagation in reacting media, specifically in electromagnetic materials. An account is presented of the mathematical methods of wave phenomena in electromagnetic materials. The author presents the theory of time-varying electromagnetic fields, which involves a discussion of Faraday's laws, Maxwell's equations and their application to electromagnetic wave propagation under a variety of conditions. The author gives a discussion of magnetohydrodynamics and plasma physics. Chapters are included on quantum mechanics and the theory of relativity. The mathematical foundation of electromagnetic waves vis a vis partial differential equations is discussed
Dispersion relation of linearly polarized strong electromagnetic waves
Energy Technology Data Exchange (ETDEWEB)
Ferrari, A; Massaglia, S [Consiglio Nazionale delle Ricerche, Turin (Italy). Lab. di Cosmo-Geofisica; Dobrowolny, M [Comitato Nazionale per l' Energia Nucleaire, Frascati (Italy). Lab. Plasma Spazio
1975-12-15
A numerical study is presented of the dispersion relation of linearly polarized strong electromagnetic waves in a cold electron plasma. The nonlinear effects introduced by the relativistic motion of electrons are: (1) the dispersion relation depends explicitly on the field strength ..cap alpha..=eE/sub 0//mc..omega../sub 0/, and (2) the propagation of modes with frequencies below the formal electron plasma frequency is allowed.
Lorentz covariance ‘almost’ implies electromagnetism and more
International Nuclear Information System (INIS)
Sobouti, Y
2015-01-01
Beginning from two simple assumptions, (i) the speed of light is a universal constant, or its equivalent, the spacetime intervals are Lorentz invariant, and (ii) there are mutually interacting particles, with a covariant ‘source-field’ equation, one arrives at a class of field equations of which the standard electromagnetism (EM) and electrodynamics are special cases. The formalism, depending on how one formulates the source-field equation, allows one to speculate magnetic monopoles, massive photons, nonlinear EMs, and more. (paper)
Panagopoulos, Dimitris J.; Johansson, Olle; Carlo, George L.
2013-01-01
PURPOSE: To evaluate SAR as a dosimetric quantity for EMF bioeffects, and identify ways for increasing the precision in EMF dosimetry and bioactivity assessment. METHODS: We discuss the interaction of man-made electromagnetic waves with biological matter and calculate the energy transferred to a single free ion within a cell. We analyze the physics and biology of SAR and evaluate the methods of its estimation. We discuss the experimentally observed non-linearity between electromagnetic exposu...
Nonlinear extraordinary wave in dense plasma
Energy Technology Data Exchange (ETDEWEB)
Krasovitskiy, V. B., E-mail: krasovit@mail.ru [Russian Academy of Sciences, Keldysh Institute of Applied Mathematics (Russian Federation); Turikov, V. A. [Russian University of Peoples’ Friendship (Russian Federation)
2013-10-15
Conditions for the propagation of a slow extraordinary wave in dense magnetized plasma are found. A solution to the set of relativistic hydrodynamic equations and Maxwell’s equations under the plasma resonance conditions, when the phase velocity of the nonlinear wave is equal to the speed of light, is obtained. The deviation of the wave frequency from the resonance frequency is accompanied by nonlinear longitudinal-transverse oscillations. It is shown that, in this case, the solution to the set of self-consistent equations obtained by averaging the initial equations over the period of high-frequency oscillations has the form of an envelope soliton. The possibility of excitation of a nonlinear wave in plasma by an external electromagnetic pulse is confirmed by numerical simulations.
A variational approach to nonlinear evolution equations in optics
Indian Academy of Sciences (India)
optics. D ANDERSON, M LISAK and A BERNTSON£. Department of Electromagnetics, Chalmers University of Technology, SE-41296 Göteborg, Sweden. £Ericsson Telcom ... Many works in nonlinear optics have made efficient ...... focusing dynamics of a laser beam (or a Bose–Einstein condensate) in a parabolic external.
Nonlinear interaction of the surface waves at a plasma boundary
International Nuclear Information System (INIS)
Dolgopolov, V.V.; El-Naggar, I.A.; Hussein, A.M.; Khalil, Sh.M.
1976-01-01
Amplitudes of electromagnetic waves with combination frequencies, radiating from the plasma boundary due to nonlinear interaction of the surface waves, have been found. Previous papers on this subject did not take into account that the tangential components of the electric field of waves with combination frequencies were discontinuous at the plasma boundary. (Auth.)
Nonlinear entropy transfer in ETG-TEM turbulence via TEM driven zonal flows
International Nuclear Information System (INIS)
Asahi, Yuuichi; Tsutsui, Hiroaki; Tsuji-Iio, Shunji; Ishizawa, Akihiro; Sugama, Hideo; Watanabe, Tomohiko
2015-01-01
Nonlinear interplay of the electron temperature gradient (ETG) modes and the trapped electron modes (TEMs) was investigated by means of gyrokinetic simulation. Focusing on the situation where both TEMs and ETG modes are linearly unstable, the effects of TEM-driven zonal flows on ETG turbulence were examined by means of entropy transfer analysis. In a statistically steady turbulence where the TEM driven zonal flows are dominant, it turned out that the zonal flows meditate the entropy transfer of the ETG modes from the low to high radial wavenumber regions. The successive entropy transfer broadens the potential fluctuation spectrum in the radial wavenumber direction. In contrast, in the situation where ETG modes are unstable but TEMs are stable, the pure ETG turbulence does not produce strong zonal flows, leading to a rather narrow spectrum in the radial wavenumber space and a higher transport level. (author)
International Nuclear Information System (INIS)
Angelino, P; Bottino, A; Hatzky, R; Jolliet, S; Sauter, O; Tran, T M; Villard, L
2006-01-01
The mutual interactions of ion temperature gradient (ITG) driven modes, zonal flows and geodesic acoustic modes (GAM) in tokamak plasmas are investigated using a global nonlinear gyrokinetic formulation with totally unconstrained evolution of temperature gradient and profile. A series of numerical simulations with the same initial temperature and density profile specifications is performed using a sequence of ideal MHD equilibria differing only in the value of the total plasma current, in particular with identical magnetic shear profiles and shapes of magnetic surfaces. On top of a bursty or quasi-steady state behaviour the zonal flows oscillate at the GAM frequency. The amplitude of these oscillations increases with the value of the safety factor q, resulting in a less effective suppression of ITG turbulence by zonal flows at a lower plasma current. The turbulence-driven volume-averaged radial heat transport is found to scale inversely with the total plasma current
Theory and design of nonlinear metamaterials
Rose, Alec Daniel
If electronics are ever to be completely replaced by optics, a significant possibility in the wake of the fiber revolution, it is likely that nonlinear materials will play a central and enabling role. Indeed, nonlinear optics is the study of the mechanisms through which light can change the nature and properties of matter and, as a corollary, how one beam or color of light can manipulate another or even itself within such a material. However, of the many barriers preventing such a lofty goal, the narrow and limited range of properties supported by nonlinear materials, and natural materials in general, stands at the forefront. Many industries have turned instead to artificial and composite materials, with homogenizable metamaterials representing a recent extension of such composites into the electromagnetic domain. In particular, the inclusion of nonlinear elements has caused metamaterials research to spill over into the field of nonlinear optics. Through careful design of their constituent elements, nonlinear metamaterials are capable of supporting an unprecedented range of interactions, promising nonlinear devices of novel design and scale. In this context, I cast the basic properties of nonlinear metamaterials in the conventional formalism of nonlinear optics. Using alternately transfer matrices and coupled mode theory, I develop two complementary methods for characterizing and designing metamaterials with arbitrary nonlinear properties. Subsequently, I apply these methods in numerical studies of several canonical metamaterials, demonstrating enhanced electric and magnetic nonlinearities, as well as predicting the existence of nonlinear magnetoelectric and off-diagonal nonlinear tensors. I then introduce simultaneous design of the linear and nonlinear properties in the context of phase matching, outlining five different metamaterial phase matching methods, with special emphasis on the phase matching of counter propagating waves in mirrorless parametric amplifiers
[Nonlinear magnetohydrodynamics
International Nuclear Information System (INIS)
1994-01-01
Resistive MHD equilibrium, even for small resistivity, differs greatly from ideal equilibrium, as do the dynamical consequences of its instabilities. The requirement, imposed by Faraday's law, that time independent magnetic fields imply curl-free electric fields, greatly restricts the electric fields allowed inside a finite-resistivity plasma. If there is no flow and the implications of the Ohm's law are taken into account (and they need not be, for ideal equilibria), the electric field must equal the resistivity times the current density. The vanishing of the divergence of the current density then provides a partial differential equation which, together with boundary conditions, uniquely determines the scalar potential, the electric field, and the current density, for any given resistivity profile. The situation parallels closely that of driven shear flows in hydrodynamics, in that while dissipative steady states are somewhat more complex than ideal ones, there are vastly fewer of them to consider. Seen in this light, the vast majority of ideal MHD equilibria are just irrelevant, incapable of being set up in the first place. The steady state whose stability thresholds and nonlinear behavior needs to be investigated ceases to be an arbitrary ad hoc exercise dependent upon the whim of the investigator, but is determined by boundary conditions and choice of resistivity profile
Electromagnetic wave energy converter
Bailey, R. L. (Inventor)
1973-01-01
Electromagnetic wave energy is converted into electric power with an array of mutually insulated electromagnetic wave absorber elements each responsive to an electric field component of the wave as it impinges thereon. Each element includes a portion tapered in the direction of wave propagation to provide a relatively wideband response spectrum. Each element includes an output for deriving a voltage replica of the electric field variations intercepted by it. Adjacent elements are positioned relative to each other so that an electric field subsists between adjacent elements in response to the impinging wave. The electric field results in a voltage difference between adjacent elements that is fed to a rectifier to derive dc output power.
Electromagnetic fields and waves
Iskander, Magdy F
2013-01-01
The latest edition of Electromagnetic Fields and Waves retains an authoritative, balanced approach, in-depth coverage, extensive analysis, and use of computational techniques to provide a complete understanding of electromagnetic—important to all electrical engineering students. An essential feature of this innovative text is the early introduction of Maxwell's equations, together with the quantifying experimental observations made by the pioneers who discovered electromagnetics. This approach directly links the mathematical relations in Maxwell's equations to real experiments and facilitates a fundamental understanding of wave propagation and use in modern practical applications, especially in today's wireless world. New and expanded topics include the conceptual relationship between Coulomb's law and Gauss's law for calculating electric fields, the relationship between Biot-Savart's and Ampere's laws and their use in calculating magnetic fields from current sources, the development of Faraday's law from e...
Homogenized description and retrieval method of nonlinear metasurfaces
Liu, Xiaojun; Larouche, Stéphane; Smith, David R.
2018-03-01
A patterned, plasmonic metasurface can strongly scatter incident light, functioning as an extremely low-profile lens, filter, reflector or other optical device. When the metasurface is patterned uniformly, its linear optical properties can be expressed using effective surface electric and magnetic polarizabilities obtained through a homogenization procedure. The homogenized description of a nonlinear metasurface, however, presents challenges both because of the inherent anisotropy of the medium as well as the much larger set of potential wave interactions available, making it challenging to assign effective nonlinear parameters to the otherwise inhomogeneous layer of metamaterial elements. Here we show that a homogenization procedure can be developed to describe nonlinear metasurfaces, which derive their nonlinear response from the enhanced local fields arising within the structured plasmonic elements. With the proposed homogenization procedure, we are able to assign effective nonlinear surface polarization densities to a nonlinear metasurface, and link these densities to the effective nonlinear surface susceptibilities and averaged macroscopic pumping fields across the metasurface. These effective nonlinear surface polarization densities are further linked to macroscopic nonlinear fields through the generalized sheet transition conditions (GSTCs). By inverting the GSTCs, the effective nonlinear surface susceptibilities of the metasurfaces can be solved for, leading to a generalized retrieval method for nonlinear metasurfaces. The application of the homogenization procedure and the GSTCs are demonstrated by retrieving the nonlinear susceptibilities of a SiO2 nonlinear slab. As an example, we investigate a nonlinear metasurface which presents nonlinear magnetoelectric coupling in near infrared regime. The method is expected to apply to any patterned metasurface whose thickness is much smaller than the wavelengths of operation, with inclusions of arbitrary geometry
Global gyrokinetic simulations of intrinsic rotation in ASDEX Upgrade Ohmic L-mode plasmas
Hornsby, W. A.; Angioni, C.; Lu, Z. X.; Fable, E.; Erofeev, I.; McDermott, R.; Medvedeva, A.; Lebschy, A.; Peeters, A. G.; The ASDEX Upgrade Team
2018-05-01
Non-linear, radially global, turbulence simulations of ASDEX Upgrade (AUG) plasmas are performed and the nonlinear generated intrinsic flow shows agreement with the intrinsic flow gradients measured in the core of Ohmic L-mode plasmas at nominal parameters. Simulations utilising the kinetic electron model show hollow intrinsic flow profiles as seen in a predominant number of experiments performed at similar plasma parameters. In addition, significantly larger flow gradients are seen than in a previous flux-tube analysis (Hornsby et al 2017 Nucl. Fusion 57 046008). Adiabatic electron model simulations can show a flow profile with opposing sign in the gradient with respect to a kinetic electron simulation, implying a reversal in the sign of the residual stress due to kinetic electrons. The shaping of the intrinsic flow is strongly determined by the density gradient profile. The sensitivity of the residual stress to variations in density profile curvature is calculated and seen to be significantly stronger than to neoclassical flows (Hornsby et al 2017 Nucl. Fusion 57 046008). This variation is strong enough on its own to explain the large variations in the intrinsic flow gradients seen in some AUG experiments. Analysis of the symmetry breaking properties of the turbulence shows that profile shearing is the dominant mechanism in producing a finite parallel wave-number, with turbulence gradient effects contributing a smaller portion of the parallel wave-vector.
Nanofocusing of electromagnetic radiation
DEFF Research Database (Denmark)
Gramotnev, D. K.; Bozhevolnyi, Sergey I.
2014-01-01
Nanofocusing of electromagnetic radiation, that is, reducing the cross sections of propagating optical modes far beyond the diffraction limit in dielectric media, can be achieved in tapered metal-dielectric waveguides that support surface plasmon-polariton modes. Although the main principles...... radiation on the nanoscale. Here, we present the underlying physical principles of radiation nanofocusing in metallic nanostructures, overview recent progress and major developments, and consider future directions and potential applications of this subfield of nano-optics....
Electromagnetic Hammer for Metalworking
Anderson, S. A.; Brunet, F.; Dowd, A.; Durham, R.; Ezell, J.; Gorr, G.; Hartley, D.; Jackson, F.; Marchand, J.; Macfarlane, W.;
1986-01-01
High eddy currents apply pressure for cold-forming. Coil housing constructed for mechanical strength to hold coil against magnetic force, to maintain electrical contact with coil ends, and to maintain insulation between coil turns. Drilled holes placed to facilitate release of bubbles during potting. In contrast with mechanical hammers, electromagnetic hammer requires no dynamic material contact with workpiece; consequently, produces almost no change in metal grain structure.
Electromagnetic compatibility and earths
International Nuclear Information System (INIS)
Duque Henao, Alan; Casas Ospina, Favio
2001-01-01
It is such the increment of applications of electric and electronic equipment in the modern companies that the lack of control of the electromagnetic perturbations, brings, get big losses and difficulties in the normal operations. The paper contribute to ago with base in the challenges that day-by-day are confronting, where the settings to earth, to be the foundation of the electric building, are fundamental for a good coexistence among the different equipment s