Nonlinear Gyrokinetic Simulations of Intrinsic Rotation in Up-down Asymmetric Tokamaks PDF Download
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Author: Justin Richard Ball
Publisher:
ISBN:
Category :
Languages : en
Pages : 136
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Book Description
Experiments and theory show that tokamak plasmas with strong toroidal rotation and rotation shear can suppress turbulent energy transport as well as allow violation of the Troyon [beta] limit. However, using external neutral beams to inject toroidal momentum, as is done in many current experiments, would require a prohibitive amount of energy in larger, reactor-sized devices. The most promising alternative to achieve significant mean plasma flow that scales to large devices is intrinsic rotation, the rotation that is observed in the absence of external momentum injection. Intrinsic rotation is observed in current experiments, but is generated by effects that are formally small in [pi]* =- [pi]i / a, the ratio of the ion gyroradius to the tokamak minor radius. These effects are insufficient in anticipated reactors because [pi]*, will be significantly smaller. Recent theoretical work concludes that up-down asymmetry in the poloidal crosssection of tokamaks can drive intrinsic rotation to lowest order in [pi]*, [1, 2]. In this thesis, we extend GS2, a local [delta] f gyrokinetic code that self-consistently calculates momentum transport, to permit up-down asymmetric configurations. MHD analysis shows that ellipticity is most effective at introducing up-down asymmetry throughout the plasma. Accordingly, tokamaks with tilted elliptical poloidal cross-sections were simulated in GS2 to determine nonlinear momentum transport. The results suggest that the current experimentally measured rotation levels can be generated in reactorsized devices using up-down asymmetry. Surprisingly, linear and nonlinear gyrokinetic simulations also suggest that tilted elliptical flux surfaces may naturally suppress turbulent energy transport. Using cyclone base case parameters [3] (except for an elongation K = 2), a 40% reduction in the linear turbulent growth rate was observed by tilting the flux surface [pi]/4 from vertical. However, this reduction of energy transport was not observed when the background temperature gradient was increased by 50%.
Author: Justin Richard Ball
Publisher:
ISBN:
Category :
Languages : en
Pages : 136
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Book Description
Experiments and theory show that tokamak plasmas with strong toroidal rotation and rotation shear can suppress turbulent energy transport as well as allow violation of the Troyon [beta] limit. However, using external neutral beams to inject toroidal momentum, as is done in many current experiments, would require a prohibitive amount of energy in larger, reactor-sized devices. The most promising alternative to achieve significant mean plasma flow that scales to large devices is intrinsic rotation, the rotation that is observed in the absence of external momentum injection. Intrinsic rotation is observed in current experiments, but is generated by effects that are formally small in [pi]* =- [pi]i / a, the ratio of the ion gyroradius to the tokamak minor radius. These effects are insufficient in anticipated reactors because [pi]*, will be significantly smaller. Recent theoretical work concludes that up-down asymmetry in the poloidal crosssection of tokamaks can drive intrinsic rotation to lowest order in [pi]*, [1, 2]. In this thesis, we extend GS2, a local [delta] f gyrokinetic code that self-consistently calculates momentum transport, to permit up-down asymmetric configurations. MHD analysis shows that ellipticity is most effective at introducing up-down asymmetry throughout the plasma. Accordingly, tokamaks with tilted elliptical poloidal cross-sections were simulated in GS2 to determine nonlinear momentum transport. The results suggest that the current experimentally measured rotation levels can be generated in reactorsized devices using up-down asymmetry. Surprisingly, linear and nonlinear gyrokinetic simulations also suggest that tilted elliptical flux surfaces may naturally suppress turbulent energy transport. Using cyclone base case parameters [3] (except for an elongation K = 2), a 40% reduction in the linear turbulent growth rate was observed by tilting the flux surface [pi]/4 from vertical. However, this reduction of energy transport was not observed when the background temperature gradient was increased by 50%.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 6
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Book Description
Three different aspects of intrinsic rotation have been treated. i) A new, first principles model for intrinsic rotation [F.I. Parra, M. Barnes and P.J. Catto, Nucl. Fusion 51, 113001 (2011)] has been implemented in the gyrokinetic code GS2. The results obtained with the code are consistent with several experimental observations, namely the rotation peaking observed after an L-H transition, the rotation reversal observed in Ohmic plasmas, and the change in rotation that follows Lower Hybrid wave injection. ii) The model in [F.I. Parra, M. Barnes and P.J. Catto, Nucl. Fusion 51, 113001 (2011)] has several simplifying assumptions that seem to be satisfied in most tokamaks. To check the importance of these hypotheses, first principles equations that do not rely on these simplifying assumptions have been derived, and a version of these new equations has been implemented in GS2 as well. iii) A tokamak cross-section that drives large intrinsic rotation has been proposed for future large tokamaks. In large tokamaks, intrinsic rotation is expected to be very small unless some up-down asymmetry is introduced. The research conducted under this contract indicates that tilted ellipticity is the most efficient way to drive intrinsic rotation.
Author: Olivier Sauter
Publisher: American Institute of Physics
ISBN: 9780735406001
Category : Science
Languages : en
Pages : 400
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Book Description
The Joint Varenna-Lausanne International Workshop on Theory of Fusion Plasmas takes place every other year in a place particularly favorable for informal and in depth discussions. Invited and contributed papers present state-of-the art researches in theoretical plasma physics, covering all domains relevant to fusion plasmas. This workshop always allows a fruitful mix of experienced researchers and students, to allow for a better understanding of the key theoretical physics models and applications, such as: Theoretical issues related to burning plasmas; Anomalous Transport (Turbulence, Coherent Structures, Microinstabilities) RF Heating and Current Drive; Macroinstabilities; Plasma-Edge Physics and Divertors; Fast particles instabilities.
Author: Per Helander
Publisher: Cambridge University Press
ISBN: 9780521020985
Category : Science
Languages : en
Pages : 316
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Book Description
A graduate level text treating transport theory, an essential element of theoretical plasma physics.
Author: Jason Parisi
Publisher: World Scientific
ISBN: 1786345447
Category : Science
Languages : en
Pages : 405
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Book Description
'The text provides an interesting history of previous and anticipated accomplishments, ending with a chapter on the relationship of fusion power to nuclear weaponry. They conclude on an optimistic note, well worth being understood by the general public.'CHOICEThe gap between the state of fusion energy research and public understanding is vast. In an entertaining and engaging narrative, this popular science book gives readers the basic tools to understand how fusion works, its potential, and contemporary research problems.Written by two young researchers in the field, The Future of Fusion Energy explains how physical laws and the Earth's energy resources motivate the current fusion program — a program that is approaching a critical point. The world's largest science project and biggest ever fusion reactor, ITER, is nearing completion. Its success could trigger a worldwide race to build a power plant, but failure could delay fusion by decades. To these ends, this book details how ITER's results could be used to design an economically competitive power plant as well as some of the many alternative fusion concepts.
Author: Kenro Miyamoto
Publisher: Taylor & Francis
ISBN: 1584887109
Category : Science
Languages : en
Pages : 393
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Book Description
Resulting from ongoing, international research into fusion processes, the International Tokamak Experimental Reactor (ITER) is a major step in the quest for a new energy source.The first graduate-level text to cover the details of ITER, Controlled Fusion and Plasma Physics introduces various aspects and issues of recent fusion research activ
Author: Jeffrey P. Freidberg
Publisher: Cambridge University Press
ISBN: 1107006252
Category : Science
Languages : en
Pages : 743
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Book Description
Comprehensive, self-contained, and clearly written, this book describes the macroscopic equilibrium and stability of high temperature plasmas.
Author: Hans-Joachim Bungartz
Publisher: Springer Nature
ISBN: 3030479560
Category : Computers
Languages : en
Pages : 624
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Book Description
This open access book summarizes the research done and results obtained in the second funding phase of the Priority Program 1648 "Software for Exascale Computing" (SPPEXA) of the German Research Foundation (DFG) presented at the SPPEXA Symposium in Dresden during October 21-23, 2019. In that respect, it both represents a continuation of Vol. 113 in Springer’s series Lecture Notes in Computational Science and Engineering, the corresponding report of SPPEXA’s first funding phase, and provides an overview of SPPEXA’s contributions towards exascale computing in today's sumpercomputer technology. The individual chapters address one or more of the research directions (1) computational algorithms, (2) system software, (3) application software, (4) data management and exploration, (5) programming, and (6) software tools. The book has an interdisciplinary appeal: scholars from computational sub-fields in computer science, mathematics, physics, or engineering will find it of particular interest.
Author: L. J. Reinders
Publisher: Springer Nature
ISBN: 3030643441
Category : Science
Languages : en
Pages : 628
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Book Description
This carefully researched book presents facts and arguments showing, beyond a doubt, that nuclear fusion power will not be technically feasible in time to satisfy the world's urgent need for climate-neutral energy. The author describes the 70-year history of nuclear fusion; the vain attempts to construct an energy-generating nuclear fusion power reactor, and shows that even in the most optimistic scenario nuclear fusion, in spite of the claims of its proponents, will not be able to make a sizable contribution to the energy mix in this century, whatever the outcome of ITER. This implies that fusion power will not be a factor in combating climate change, and that the race to save the climate with carbon-free energy will have been won or lost long before the first nuclear fusion power station comes on line. Aimed at the general public as well as those whose decisions directly affect energy policy, this book will be a valuable resource for informing future debates.
Author: A.V. Melnikov
Publisher: Springer
ISBN: 303003481X
Category : Science
Languages : en
Pages : 240
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Book Description
This work introduces heavy ion beam probe diagnostics and presents an overview of its applications. The heavy ion beam probe is a unique tool for the measurement of potential in the plasma core in order to understand the role of the electric field in plasma confinement, including the mechanism of transition from low to high confinement regimes (L–H transition). This allows measurement of the steady-state profile of the plasma potential, and its use has been extended to include the measurement of quasi-monochromatic and broadband oscillating components, the turbulent-particle flux and oscillations of the electron density and poloidal magnetic field. Special emphasis is placed on the study of Geodesic Acoustic Modes and Alfvén Eigenmodes excited by energetic particles with experimental data sets. These experimental studies help to understand the link between broadband turbulent physics and quasi-coherent oscillations in devices with a rather different magnetic configuration. The book also compares spontaneous and biased transitions from low to high confinement regimes on both classes of closed magnetic traps (tokamak and stellarator) and highlights the common features in the behavior of electric potential and turbulence of magnetized plasmas. A valuable resource for physicists, postgraduates and students specializing in plasma physics and controlled fusion.
