Download or read book Transport in Gyrokinetic Tokamaks written by Harry E. Mynick and published by . This book was released on 1995 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Gyrokinetic simulation of tokamak turbulence and transport in realistic geometry written by Geoffrey Mark Furnish and published by . This book was released on 1996 with total page 402 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 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 Transport and Gyrokinetic Effects of Heating and Current Drive in Tokamaks written by M. Cox and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Gyrokinetic Simulations of Microturbulence and Transport in Tokamak Plasmas written by Daniel Tegnered and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Global Gyrokinetic Simulation of Tokamak Transport written by and published by . This book was released on 1998 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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?{sub i}(?{sub i} ≡ ∂lnT{sub i}/∂ln n{sub 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.

Download or read book Impurity Transport in Tokamak Plasmas written by Peter Donnel and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Impurity transport is an issue of utmost importance for tokamaks. Indeed high-Z materials are only partially ionized in the plasma core, so that they can lead to prohibitive radiative losses even at low concentrations, and impact dramatically plasma performance and stability. On-axis accumulation of tungsten has been widely observed in tokamaks.While the very core impurity peaking is generally attributed to neoclassical effects, turbulent transport could well dominate in the gradient region at ITER relevant collisionality. Up to recently, first principles simulations of corresponding fluxes were performed with different dedicated codes, implicitly assuming that both transport channels are separable and therefore additive. The validity of this assumption is questionned. Simulations obtained with the gyrokinetic code GYSELA have shown clear evidences of a neoclassical-turbulence synergy for impurity transport and allowed the identification of a mechanism that underly this synergy.An analytical work allows to compute the level and the structure of the axisymmetric part of the electric potential knowing the turbulence intensity. Two mechanisms are found for the generation of poloidal asymmetries of the electric potential: flow compressibility and the ballooning of the turbulence. A new prediction for the neoclassical impurity flux in presence of large poloidal asymmetries and pressure anisotropies has been derived. A fair agreement has been found between the new theoretical prediction for neoclassical impurity flux and the results of a GYSELA simulation displaying large poloidal asymmetries and pressure anisotropies induced by the presence of turbulence.

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 Turbulence and Transport in the Mega Ampere Spherical Tokamak written by Greg J. Colyer and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Quasi linear Gyrokinetic Transport Model for Tokamak Plasmas written by Alessandro Casati and published by . This book was released on 2009 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: Le développement d'un modèle de transport gyrocinétique quasi-linéaire pour les plasmas de tokamak, conçu pour fournir des prévisions physiquement fiables des quantités thermodynamiques pertinentes, est une tâche qui a exigé des liens étroits entre les études théoriques, expérimentales et numériques. Le cadre du modèle ici développé, Qualikiz, qui exploite une réduction de complexité par rapport à la dynamique non-linéaire du plasma, permet de multiples validations de la compréhension actuelle de la micro-turbulence dans les tokamaks. Les principaux résultats de cette thèse découlent des étapes fondamentales de la formulation du modèle de transport quasi-linéaire, c'est-à-dire : (1) la vérification de la réponse quasi-linéaire contre les résultats numériques non-linéaires, (2) l'amélioration du modèle de la saturation grâce à une validation quantitative des codes non-linéaires contre les mesures de turbulence, (3) l'intégration du modèle quasi-linéaire dans un solveur de transport intégré.

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 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.