Download or read book Gyrokinetic Simulations of Turbulent Particle and Heat Transport in Tokamaks written by and published by . This book was released on 2015 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modeling the Turbulent Momentum Transport in Tokamak Plasmas written by Pierre Cottier and published by LAP Lambert Academic Publishing. This book was released on 2014-04-01 with total page 128 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 ExB shear induced residual stress as well as the influence of rotation on the heat and particle fluxes. The different contributions to the turbulent momentum flux are studied and successfully compared against both non-linear gyro-kinetic simulations and experimental data.
Download or read book Transport Analysis in Tokamak Plasmas written by Sara Moradi and published by LAP Lambert Academic Publishing. This book was released on 2010-08 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the least understood areas of the plasma particle or heat transport is the turbulent transport. In this work the main focus is on the development and data analysis of anomalous transport characteristics (transport coefficients and fluxes) under fusion conditions in large tokamaks. Fluid and gyro-kinetic models are used and obtained results are compared. A model based on fractional kinetics for the study of the SOL turbulent transport characteristics, where non-Gaussian PDFs are observed, is developed.
Download or read book Lecture Series on Turbulent Transport in Tokamaks written by Ronald E. Waltz and published by . This book was released on 1987 with total page 210 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Collisions in Global Gyrokinetic Simulations of Tokamak Plasmas Using the Delta f Particle in cell Approach written by Thibaut Vernay and published by . This book was released on 2013 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Gyrokinetic Simulations of Turbulent Transport in Tokamak Plasmas written by Andreas Skyman and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Gyrokinetic Studies of Particle Transport in Tokamaks written by Carlos Andres Estrada-Mila and published by . This book was released on 2006 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation a systematic study of particle transport in tokamaks, using gyrokinetic simulations and theory, is presented. This work can be divided into three major parts. The first part studies particle transport in pure plasmas and investigates the origin and nature of flows against density gradients, also known as particle pinches. It is found that these pinches, which are primarily driven by temperature gradients, can also be responsible for the density peaking observed in experiments such as ASDEX-U, DIII-D or JET. The second part of this work studies plasmas with multiple ion species. First, we study helium ash transport and its effects in the core of a reactor plasma, finding that a helium pinch driven by finite toroidicity can be created in some cases. Second, we study deuterium and tritium plasmas from the point of view of isotope flow separation, finding that in a 50-50 deuterium-tritium plasma, a small fuel separation may occur. Finally, the last part studies the behavior of energetic species in reactor plasmas. It is found that alpha particles interact strongly with the background turbulence. Perhaps the most surprising finding is that the fluxes per particle of alphas can be stronger than the fluxes per particle of deuterium (i.e. main ion), as opposed to ``conventional wisdom'' which assumes that species with large gyroradii do not significantly interact with the turbulence.
Download or read book Gyrokinetic Simulation of Global Turbulent Transport Properties in Tokamak Experiments written by and published by . This book was released on 2006 with total page 92505 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book ADVANCES IN COMPREHENSIVE GYROKINETIC SIMULATIONS OF TRANSPORT IN TOKAMAKS written by R. E. WALTZ and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 {beta}, equilibrium ExB shear stabilization, and all in real tokamak geometry. Most importantly the code operates at finite relative gyroradius ({rho}{sub *}) 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.
Download or read book Tokamaks written by John Wesson and published by Oxford University Press. This book was released on 2011-10-13 with total page 828 pages. Available in PDF, EPUB and Kindle. Book excerpt: The tokamak is the principal tool in controlled fusion research. This book acts as an introduction to the subject and a basic reference for theory, definitions, equations, and experimental results. The fourth edition has been completely revised, describing their development of tokamaks to the point of producing significant fusion power.
Download or read book Advances in Comprehensive Gyrokinetic Simulations of Transport in Tokamaks written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 [beta], equilibrium ExB shear stabilization, and all in real tokamak geometry. Most importantly the code operates at finite relative gyroradius ([rho]{sub *}) 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.
Download or read book Gyrokinetic Simulations of Turbulent Impurity Transport in Tokamaks written by Pierre Manas and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding impurity transport in the core of tokamak plasmas is central to achieving controlled fusion. Indeed impurities are ubiquitous in these devices and their presence in the core are detrimental to plasma confinement (fuel dilution, Bremsstrahlung). Recently, specific attention was given to the convective mechanism related to the gradient of the toroidal rotation to explain experimental flat/hollow impurity profiles in the plasma core. In this thesis, up-to-date modelling tools (NEO for neoclassical transport and GKW for turbulent transport) including the impact of toroidal rotation are used to study both the neoclassical and turbulent contributions to impurity fluxes. A comparison of the experimental and modelled carbon density peaking factor (R/LnC) is performed for a large number of baseline and hybrid H-mode plasmas (increased confinement regimes) with modest to high toroidal rotation from the European tokamak JET. Confrontation of experimental and modelled carbon peaking factor yields two main results. First roto-diffusion is found to have a nonnegligible impact on the carbon peaking factor at high values of the toroidal rotation frequency gradient. Second, there is a tendency to overpredict the experimental R/LnC in the core inner region where the carbon density profiles are hollow. This disagreement between experimental and modelled R/LnC, closely related to the collisionality, is also observed for the momentum transport channel which hints at a common parallel symmetry breaking mechanism lacking in the simulations.
Download or read book Transport in Gyrokinetic Tokamaks written by and published by . This book was released on 1995 with total page 45 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive study of transport in full-volume gyrokinetic (gk) simulations of ion temperature gradient driven turbulence in core tokamak plasmas is presented. Though this g̀̀yrokinetic tokamak ̀̀is much simpler than experimental tokamaks, such simplicity is an asset, because a dependable nonlinear transport theory for such systems should be more attainable. Toward this end, we pursue two related lines of inquiry. (1) We study the scalings of gk tokamaks with respect to important system parameters. In contrast to real machines, the scalings of larger gk systems (a/?{sub s} ≳ 64) with minor radius, with current, and with a/?{sub s} are roughly consistent with the approximate theoretical expectations for electrostatic turbulent transport which exist as yet. Smaller systems manifest quite different scalings, which aids in interpreting differing mass-scaling results in other work. (2) With the goal of developing a first-principles theory of gk transport, we use the gk data to infer the underlying transport physics. The data indicate that, of the many modes k present in the simulation, only a modest number (N{sub k} ∼ 10) of k dominate the transport, and for each, only a handful (N{sub p} ∼ 5) of couplings to other modes p appear to be significant, implying that the essential transport physics may be described by a far simpler system than would have been expected on the basis of earlier nonlinear theory alone. Part of this analysis is the inference of the coupling coefficients M{sub kpq} governing the nonlinear mode interactions, whose measurement from tokamak simulation data is presented here for the first time.
Download or read book Turbulence and Transport in Enhanced Confinement Regimes of Tokamaks written by and published by . This book was released on 1996 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Magnetic Fluctuations in Gyrokinetic Simulations of Tokamak Scrape Off Layer Turbulence written by Noah Roth Mandell and published by . This book was released on 2021 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding turbulent transport physics in the tokamak edge and scrape-off layer (SOL) is critical to developing a successful fusion reactor. The dynamics in these regions plays a key role in achieving high fusion performance by determining the edge pedestal that suppresses turbulence in the high-confinement mode (H-mode). Additionally, the survivability of a reactor is set by the heat load to the vessel walls, making it important to understand turbulent spreading of heat as it flows along open magnetic field lines in the SOL. Large-amplitude fluctuations, magnetic X-point geometry, and plasma interactions with material walls make simulating turbulence in the edge/SOL more challenging than in the core region, necessitating specialized gyrokinetic codes. Further, the inclusion of electromagnetic effects in gyrokinetic simulations that can handle the unique challenges of the boundary plasma is critical to the understanding of phenomena such as the pedestal and edge-localized modes, for which electromagnetic dynamics are expected to be important.In this thesis, we develop the first capability to simulate electromagnetic gyrokinetic turbulence on open magnetic field lines. This is an important step towards comprehensive electromagnetic gyrokinetic simulations of the coupled edge/SOL system. By using a continuum full-f approach via an energy-conserving discontinuous Galerkin (DG) discretization scheme that avoids the Ampere cancellation problem, we show that electromagnetic fluctuations can be handled in a robust, stable, and efficient manner in the gyrokinetic module of the Gkeyll code. We then present results which roughly model the scrape-off layer of the National Spherical Torus Experiment (NSTX), and show that electromagnetic effects can affect blob dynamics and transport. We also formulate the gyrokinetic system in field-aligned coordinates for modeling realistic edge and scrape-off layer geometries in experiments. A novel DG algorithm for maintaining positivity of the distribution function while preserving conservation laws is also presented.
Download or read book Collisional Transport in Magnetized Plasmas written by Per Helander and published by Cambridge University Press. This book was released on 2005-10-06 with total page 316 pages. Available in PDF, EPUB and Kindle. Book excerpt: A graduate level text treating transport theory, an essential element of theoretical plasma physics.
Download or read book Turbulent Transport In Magnetized Plasmas Second Edition written by C Wendell Horton, Jr and published by #N/A. This book was released on 2017-07-21 with total page 522 pages. Available in PDF, EPUB and Kindle. Book excerpt: For a few seconds with large machines, scientists and engineers have now created the fusion power of the stars in the laboratory and at the same time find the rich range of complex turbulent electromagnetic waves that transport the plasma confinement systems. The turbulent transport mechanisms created in the laboratory are explained in detail in the second edition of 'Turbulent Transport in Magnetized Plasmas' by Professor Horton.The principles and properties of the major plasma confinement machines are explored with basic physics to the extent currently understood. For the observational laws that are not understood — the empirical confinement laws — offering challenges to the next generation of plasma students and researchers — are explained in detail. An example, is the confinement regime — called the 'I-mode' — currently a hot topic — is explored.Numerous important problems and puzzles for the next generation of plasma scientists are explained. There is growing demand for new simulation codes utilizing the massively parallel computers with MPI and GPU methods. When the 20 billion dollar ITER machine is tested in the 2020ies, new theories and faster/smarter computer simulations running in near real-time control systems will be used to control the burning hydrogen plasmas.
