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Author :
Publisher :
ISBN 13 :
Total Pages : 10 pages
Book Rating : 4.:/5 (871 download)
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:
Author : Jan Weiland
Publisher : Springer Science & Business Media
ISBN 13 : 1461437431
Total Pages : 235 pages
Book Rating : 4.4/5 (614 download)
Download or read book Stability and Transport in Magnetic Confinement Systems written by Jan Weiland and published by Springer Science & Business Media. This book was released on 2012-06-27 with total page 235 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stability and Transport in Magnetic Confinement Systems provides an advanced introduction to the fields of stability and transport in tokamaks. It serves as a reference for researchers with its highly-detailed theoretical background, and contains new results in the areas of analytical nonlinear theory of transport using kinetic theory and fluid closure. The use of fluid descriptions for advanced stability and transport problems provide the reader with a better understanding of this topic. In addition, the areas of nonlinear kinetic theory and fluid closure gives the researcher the basic knowledge of a highly relevant area to the present development of transport physics.
Author : Marshall N. Rosenbluth
Publisher : Springer Science & Business Media
ISBN 13 : 9781563961311
Total Pages : 514 pages
Book Rating : 4.9/5 (613 download)
Download or read book New Ideas in Tokamak Confinement written by Marshall N. Rosenbluth and published by Springer Science & Business Media. This book was released on 1997-05-08 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt: Market: Scientists and students involved in thermonuclear fusion research. Thermonuclear fusion research using the confinement device tokamak represents one of the most prominent science projects in the second half of the 20th century. International Tokamak Community is now committing significant effort and funds to experiments with burning plasma, hot and dense enough to produce significant nuclear fusion reactions. The methods used to enhance tokamak performance have a profound and immediate effect on machine design. This book provides an up-to-date account of research in tokamak fusion and puts forward innovative ideas in confinement physics.
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ISBN 13 :
Total Pages : 6 pages
Book Rating : 4.:/5 (682 download)
Download or read book Role of Core Toroidal Rotation Shear on Turbulence and Transport in the Improved Confinement Regimes of the DIII-D Tokamak written by and published by . This book was released on 1993 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt: This a brief report which discusses the role of core toroidal rotation shear on turbulence and transport in the improved confinement regimes of the doublet-3 tokamak.
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ISBN 13 :
Total Pages : 66 pages
Book Rating : 4.:/5 (873 download)
Download or read book Issues in Tokamak/stellarator Transport and Confinement Enhancement Mechanisms written by and published by . This book was released on 1990 with total page 66 pages. Available in PDF, EPUB and Kindle. Book excerpt: At present, the mechanism for anomalous energy transport in low-[beta] toroidal plasmas -- tokamaks and stellarators -- remains unclear, although transport by turbulent E × B velocities associated with nonlinear, fine-scale microinstabilities is a leading candidate. This article discusses basic theoretical concepts of various transport and confinement enhancement mechanisms as well as experimental ramifications which would enable one to distinguish among them and hence identify a dominant transport mechanism. While many of the predictions of fine-scale turbulence are born out by experiment, notable contradictions exist. Projections of ignition margin rest both on the scaling properties of the confinement mechanism and on the criteria for entering enhanced confinement regimes. At present, the greatest uncertainties lie with the basis for scaling confinement enhancement criteria. A series of questions, to be answered by new experimental/theoretical work, is posed to resolve these outstanding contradictions (or refute the fine-scale turbulence model) and to establish confinement enhancement criteria. 73 refs., 4 figs., 5 tabs.
Author : Ronald E. Waltz
Publisher :
ISBN 13 :
Total Pages : 210 pages
Book Rating : 4.3/5 (91 download)
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 Enhancement of Confinement in Tokamaks written by and published by . This book was released on 1986 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A plausible interpretation of the experimental evidence is that energy confinement in tokamaks is governed by two separate considerations: (1) the need for resistive MHD kink-stability, which limits the permissible range of current profiles - and therefore normally also the range of temperature profiles; and (2) the presence of strongly anomalous microscopic energy transport near the plasma edge, which calibrates the amplitude of the global temperature profile, thus determining the energy confinement time tau/sub E/. Correspondingly, there are two main paths towards the enhancement of tokamak confinement: (1) Configurational optimization, to increase the MHD-stable energy content of the plasma core, can evidently be pursued by varying the cross-sectional shape of the plasma and/or finding stable radial profiles with central q-values substantially below unity - but crossing from ''first'' to ''second'' stability within the peak-pressure region would have the greatest ultimate potential. (2) Suppression of edge turbulence, so as to improve the heat insulation in the outer plasma shell, can be pursued by various local stabilizing techniques, such as use of a poloidal divertor. The present confinement model and initial TFTR pellet-injection results suggest that the introduction of a super-high-density region within the plasma core should be particularly valuable for enhancing ntau/subE/. In D-T operation, a centrally peaked plasma pressure profile could possibly lend itself to alpha-particle-driven entry into the second-stability regime.
Download or read book Identification of New Turbulence Contributions to Plasma Transport and Confinement in Spherical Tokamak Regime written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Highly distinct features of spherical tokamaks (ST), such as National Spherical Torus eXperiment (NSTX) and NSTX-U, result in a different fusion plasma regime with unique physics properties compared to conventional tokamaks. Nonlinear global gyrokinetic simulations critical for addressing turbulence and transport physics in the ST regime have led to new insights. The drift wave Kelvin-Helmholtz (KH) instability characterized by intrinsic mode asymmetry is identified in strongly rotating NSTX L-mode plasmas. While the strong E x B shear associated with the rotation leads to a reduction in KH/ion temperature gradient turbulence, the remaining fluctuations can produce a significant ion thermal transport that is comparable to the experimental level in the outer core region (with no "transport shortfall"). The other new, important turbulence source identified in NSTX is the dissipative trapped electron mode (DTEM), which is believed to play little role in conventional tokamak regime. Due to the high fraction of trapped electrons, long wavelength DTEMs peaking around k(theta)rho(s) similar to 0.1 are destabilized in NSTX collisionality regime by electron density and temperature gradients achieved there. Surprisingly, the E x B shear stabilization effect on DTEM is remarkably weak, which makes it a major turbulence source in the ST regime dominant over collisionless TEM (CTEM). The latter, on the other hand, is subject to strong collisional and E x B shear suppression in NSTX. DTEM is shown to produce significant particle, energy and toroidal momentum transport, in agreement with experimental levels in NSTX H-modes. Moreover, DTEM-driven transport in NSTX parametric regime is found to increase with electron collision frequency, providing one possible source for the scaling of confinement time observed in NSTX H-modes. Most interestingly, the existence of a turbulence-free regime in the collision-induced CTEM to DTEM transition, corresponding to a minimum plasma transport in advanced ST collisionality regime, is predicted. (C) 2015 AIP Publishing LLC.
Author :
Publisher :
ISBN 13 :
Total Pages : 230 pages
Book Rating : 4.:/5 (684 download)
Download or read book The Texas Experimental Tokamak written by and published by . This book was released on 1995 with total page 230 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Fusion Research Center (FRC) at the University Texas will operate the tokamak TEXT-U and its associated systems for experimental research in basic plasma physics. While the tokamak is not innovative, the research program, diagnostics and planned experiments are. The fusion community will reap the benefits of the success in completing the upgrades (auxiliary heating, divertor, diagnostics, wall conditioning), developing diverted discharges in both double and single null configurations, exploring improved confinement regimes including a limiter H-mode, and developing unique, critical turbulence diagnostics. With these new regimes, the authors are poised to perform the sort of turbulence and transport studies for which the TEXT group has distinguished itself and for which the upgrade was intended. TEXT-U is also a facility for collaborators to perform innovative experiments and develop diagnostics before transferring them to larger machines. The general philosophy is that the understanding of plasma physics must be part of any intelligent fusion program, and that basic experimental research is the most important part of any such program. The emphasis of the proposed research is to provide well-documented plasmas which will be used to suggest and evaluate theories, to explore control techniques, to develop advanced diagnostics and analysis techniques, and to extend current drive techniques. Up to 1 MW of electron cyclotron heating (ECH) will be used not only for heating but as a localized, perturbative tool. Areas of proposed research are: (1) core turbulence and transport; (2) edge turbulence and transport; (3) turbulence analysis; (4) improved confinement; (5) ECH physics; (6) Alfven wave current drive; and (7) diagnostic development.
Author : M. G. Bell
Publisher :
ISBN 13 :
Total Pages : 18 pages
Book Rating : 4.:/5 (713 download)
Download or read book Core Transport Reduction in Tokamak Plasmas with Modified Magnetic Shear written by M. G. Bell and published by . This book was released on 1998 with total page 18 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 :
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ISBN 13 :
Total Pages : 500 pages
Book Rating : 4.X/5 (4 download)
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : C Wendell Horton, Jr
Publisher : #N/A
ISBN 13 : 9813225904
Total Pages : 522 pages
Book Rating : 4.8/5 (132 download)
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.
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 : Roscoe B White
Publisher : World Scientific Publishing Company
ISBN 13 : 1911298984
Total Pages : 389 pages
Book Rating : 4.9/5 (112 download)
Download or read book The Theory of Toroidally Confined Plasmas written by Roscoe B White and published by World Scientific Publishing Company. This book was released on 2001-07-09 with total page 389 pages. Available in PDF, EPUB and Kindle. Book excerpt: This invaluable book is designed to provide a basic introduction to plasma equilibrium, particle orbits, transport, and those ideal and resistive magnetohydrodynamic instabilities which dominate the behavior of toroidal magnetically confined plasmas, and to develop the mathematical methods necessary for their theoretical analysis. The book deals primarily with the consequences of ideal and resistive magnetohydrodynamics, these theories being responsible for most of what is well understood regarding the physics of fusion oriented discharges. Contents:Toroidal Configuration: EquilibriumGuiding Center MotionLinear Ideal ModesLinear Resistive ModesNonlinear BehaviorMode-Particle InteractionTransportPhase Integral Methods Readership: Graduate students, researchers and academics in the field of fusion.
Author : Michael Lane Garrett
Publisher :
ISBN 13 :
Total Pages : 120 pages
Book Rating : 4.:/5 (871 download)
Download or read book Fluctuation Induced Cross-field Transport in Hall Thrusters and Tokamaks written by Michael Lane Garrett and published by . This book was released on 2013 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: One area of fundamental plasma physics which remains poorly understood is the transport of particles across magnetic field lines at rates significantly higher than predicted by theory exclusively based on collisions. This "anomalous" transport is observed in many different classes of plasma experiment. Notably, both magnetic confinement fusion devices and Hall thrusters exhibit anomalous cross-field particle diffusion. This higher than predicted "loss" of particles has significant practical implications for both classes of experiment. In the case of magnetic confinement fusion experiments, such as tokamaks, the Lawson criterion nT[tau]E >/= 1021 [keV. s. M- 3] dictates that the reactant particles in a fusion plasma must be confined for a sufficient time to fuse. Higher than predicted cross-field transport decreases the effectiveness of the magnetic confinement and makes fusion more difficult to achieve. For Hall thrusters, enhanced cross-field electron mobility reduces the efficiency of the thruster. As a result, more propellant and power is required to achieve the same thrust. The goal of this thesis is to review observed and predicted fluctuation induced particle transport in Hall thrusters and tokamaks. To date, significant work has been done within both the tokamak and propulsion communities to attempt to quantify the effect of turbulent fluctuations of plasma parameters on anomalous cross-field transport. However, our understanding of the fundamental physical processes that lead to anomalously high cross-field transport remains incomplete. These two regimes of plasma physics are very different in several important ways. The magnetic field strength and field orientation, the device size, the collisionality of different species, the ion mass, and the presence of neutrals are all areas with significant differences between tokamaks and Hall thrusters. However, there are similarities as well. For example, the edge density and temperature in a tokamak are similar to those found in Hall thrusters, both have magnetized electrons, drift waves occur in both regimes and many of the observed fluctuations are of similar scale. Generally, research on cross-field transport within the tokamak community is isolated from work done within the thruster community. However, analysis of physics within both regimes reveals a rich set of complex fluctuations across a broad frequency spectrum, which contribute to cross-field transport. By studying the relevant phenomena in tandem, we can reveal fundamental processes present in both regimes. Hopefully, this will lead to a global explanation for these elusive physical processes.
Author : Nicolas Nace
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (18 download)
Download or read book Dynamics of Driven and Spontaneous Transport Barriers in the Edge Plasma of Tokamaks written by Nicolas Nace and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermonuclear fusion reactors are one of the mid to long term solutions to transit towards a world dominated by carbon-free energy. Extreme temperatures are required for fusion reactions and the plasma of hydrogen isotopes must be magnetically confined in a torus shape. Sustaining such high level of particle and energy confinements is a key issue. Reactors are expected to operate in a high confinement regime - the H-mode - in which turbulent transport is reduced by the presence of a transport barrier in the edge plasma. This regime is observed in all current devices but remains largely miss-understood. In this thesis, we investigate several mechanisms involved in the transition towards H-mode. For that purpose, we use a range of numerical simulation tools of increasing complexity. Using simple models, we first highlight and analyze basic mechanisms likely to play a role in the on-set of transport barriers and in their impact on turbulence. Moving progressively to more complex models, we discuss the relevance of these physics in explaining experimental observations. The magnetic geometry and especially the magnetic shear are pointed out as key players.
