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Author : Greg J. Colyer
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)
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:
Author : Nicholas Ross Walkden
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)
Download or read book Properties of Intermittent Transport in the Mega Ampere Spherical Tokamak written by Nicholas Ross Walkden and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Young-chul Kim
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (872 download)
Download or read book Characteristics of Plasma Turbulence in the Mega Amp Spherical Tokamak written by Young-chul Kim and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Ferdinand van Wyk
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)
Download or read book Subcritical Turbulence in the Mega Ampere Spherical Tokamak written by Ferdinand van Wyk and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Benjamin D. Dudson
Publisher :
ISBN 13 :
Total Pages : 434 pages
Book Rating : 4.:/5 (311 download)
Download or read book Edge Turbulence in the Mega-amp Spherical Tokamak written by Benjamin D. Dudson and published by . This book was released on 2007 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Owen Matthew Jones
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)
Download or read book Experimental Fast-ion Transport Studies on the Mega-Amp Spherical Tokamak written by Owen Matthew Jones and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Geoffrey Mark Furnish
Publisher :
ISBN 13 :
Total Pages : 402 pages
Book Rating : 4.:/5 (388 download)
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:
Author : Noah Roth Mandell
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.5/5 (152 download)
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.
Author :
Publisher :
ISBN 13 :
Total Pages : 170 pages
Book Rating : 4.:/5 (931 download)
Download or read book Edge Turbulence Studies During Inter-ELM Periods in the Mega-amp Spherical Tokamak written by and published by . This book was released on 2009 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Distinct Turbulence Sources and Confinement Features in the Spherical Tokamak Plasma Regime written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: New turbulence contributions to plasma transport and confinement in the spherical tokamak (ST) regime are identified through nonlinear gyrokinetic simulations. The drift wave Kelvin-Helmholtz (KH) mode characterized by intrinsic mode asymmetry is shown to drive significant ion thermal transport in strongly rotating national spherical torus experiment (NSTX) L-modes. The long wavelength, quasi-coherent dissipative trapped electron mode (TEM) is destabilized in NSTX H-modes despite the presence of strong ExB shear, providing a robust turbulence source dominant over collisionless TEM. Dissipative trapped electron mode (DTEM)-driven transport in the NSTX parametric regime is shown to increase with electron collision frequency, offering one possible source for the confinement scaling observed in experiments. There exists a turbulence-free regime in the collision-induced collisionless trapped electron mode to DTEM transition for ST plasmas. This predicts a natural access to a minimum transport state in the low collisionality regime that future advanced STs may cover.
Author :
Publisher :
ISBN 13 :
Total Pages : 92505 pages
Book Rating : 4.:/5 (727 download)
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 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.
Author : Pierre Cottier
Publisher : LAP Lambert Academic Publishing
ISBN 13 : 9783659411038
Total Pages : 128 pages
Book Rating : 4.4/5 (11 download)
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.
Author :
Publisher :
ISBN 13 :
Total Pages : 38 pages
Book Rating : 4.:/5 (893 download)
Download or read book Optimization of a Mega-ampere Spherical Tokamak for Beta-limit and Confinement Studies written by and published by . This book was released on 1994 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent favorable results on the START experiment have caused renewed interest in the potential of low aspect ratio tokamaks. To aid in designing a next-step spherical tokamak to study confinement scaling, high beta, and high normalized beta plasmas for minimal cost, the authors have developed a transport scaling and device optimization code. This code STOP, benchmarked against START, includes 10 empirical confinement scaling laws and essential tokamak physics such as stability limits. Parameters are optimized separately for each scaling law and physical goal. Using STOP the authors find for R/a = 1.2 to 2.0 one can achieve [beta]{sub N} = 5, ([beta]) = 31--44%, and easily study predicted confinement degradation with auxiliary heating with just two neutral beams (P{sub NB}
Author :
Publisher :
ISBN 13 :
Total Pages : 45 pages
Book Rating : 4.:/5 (873 download)
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.
Author : Pierre Manas
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (965 download)
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.
Author : Andreas Skyman
Publisher :
ISBN 13 : 9789173859615
Total Pages : pages
Book Rating : 4.8/5 (596 download)
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:
