Ideal MHD Stability of Very High Beta Tokamaks PDF Download
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Author: M. S. Chance
Publisher:
ISBN:
Category :
Languages : en
Pages : 17
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Book Description
Author: M. S. Chance
Publisher:
ISBN:
Category :
Languages : en
Pages : 17
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Achieving very high [beta] and high [beta]{sub p} simultaneously in tokamaks generally implies that the second stability region against ballooning modes must be accessed. They describe several approaches for doing this, which are characterized by the choice of constraints imposed on the equilibrium profiles and the cross-sectional shape of the plasma. The combination of high toroidal beta, restricting the current density to vanish at the edge of the plasma and maintaining a monotonic q profile, proves to be the most stringent. Consideration of equilibria with high [epsilon][beta]{sub p} but low [beta] facilitates accessibility with peaked pressure profiles and high values of q0. Allowing the pressure gradient and hence the current density to be finite at the plasma edge allows all surfaces to lie within the second stability regime. For free boundary plasmas with divertors, the divertor stabilized edge region remains in the first stability regime while the plasma core reaches into the second regime. Careful tailoring of the profiles must be used to traverse the unstable barrier commonly seen near the edge of these plasmas. The CAMINO code allows them to compute s-[alpha] curves for general tokamak geometry. These diagrams enable them to construct equilibria whose profiles are only constrained, at worst, to be marginally stable everywhere, but do not necessarily satisfy the constraints on the current or [beta]. There are theoretical indications that under certain conditions the external kinks possess a second region of stability at high q0 that is analogous to that of the ballooning modes. It is found that extremely accurate numerical means must be developed and applied to confidently establish the validity of these results.
Author: Hartmut Zohm
Publisher: John Wiley & Sons
ISBN: 3527412328
Category : Science
Languages : en
Pages : 254
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Book Description
This book bridges the gap between general plasma physics lectures and the real world problems in MHD stability. In order to support the understanding of concepts and their implication, it refers to real world problems such as toroidal mode coupling or nonlinear evolution in a conceptual and phenomenological approach. Detailed mathematical treatment will involve classical linear stability analysis and an outline of more recent concepts such as the ballooning formalism. The book is based on lectures that the author has given to Master and PhD students in Fusion Plasma Physics. Due its strong link to experimental results in MHD instabilities, the book is also of use to senior researchers in the field, i.e. experimental physicists and engineers in fusion reactor science. The volume is organized in three parts. It starts with an introduction to the MHD equations, a section on toroidal equilibrium (tokamak and stellarator), and on linear stability analysis. Starting from there, the ideal MHD stability of the tokamak configuration will be treated in the second part which is subdivided into current driven and pressure driven MHD. This includes many examples with reference to experimental results for important MHD instabilities such as kinks and their transformation to RWMs, infernal modes, peeling modes, ballooning modes and their relation to ELMs. Finally the coverage is completed by a chapter on resistive stability explaining reconnection and island formation. Again, examples from recent tokamak MHD such as sawteeth, CTMs, NTMs and their relation to disruptions are extensively discussed.
Author:
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Category :
Languages : en
Pages :
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Book Description
Limitations on high-.beta. tokamaks are imposed by a number of ideal and resistive MHD instabilities. The present paper reports results on three such studies: (1) Numerical analysis using the Princeton PEST code on .beta. optimization of tokamaks for low toroidal mode numbers n; (2) analytic and numerical results on ideal ballooning modes with high n; and (3) analytic and numerical results on resistive ballooning modes at high n.
Author: D. Sherwell
Publisher:
ISBN:
Category :
Languages : en
Pages : 94
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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:
Publisher:
ISBN:
Category : Magnetohydrodynamics
Languages : en
Pages : 60
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Author:
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Category :
Languages : en
Pages :
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Book Description
Stable high-beta plasmas are required for the tokamak to attain an economical fusion reactor. Recently, intense neutral beam heating experiments in tokamaks have shown new effects on plasma stability and confinement associated with high beta plasmas. The observed spectrum of MHD fluctuations at high beta is clearly dominated by the n = 1 mode when the q = 1 surface is in the plasma. The m/n = 1/1 mode drives other n = 1 modes through toroidal coupling and n> 1 modes through nonlinear coupling. On PDX, with near perpendicular injection, a resonant interaction between the n = 1 internal kink and the trapped fast ions results in loss of beam particles and heating power. Key parameters in the theory are the value of q0 and the injection angle. High frequency broadband magnetic fluctuations have been observed on ISX-B and D-III and a correlation with the deterioration of plasma confinement was reported. During enhanced confinement (H-mode) discharges in divertor plasmas, two new edge instabilities were observed, both localized radially near the separatrix. By assembling results from the different tokamak experiments, it is found that the simple theoretical ideal MHD beta limit has not been exceeded. Whether this represents an ultimate tokamak limit or if beta optimized configurations (Dee- or bean-shaped plasmas) can exceed this limit and perhaps enter a second regime of stability remains to be clarified.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 10
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Book Description
This paper will give an overview of the some of the methods which are used to simulate the ideal MHD properties of tokamak plasmas. A great deal of the research in this field is necessarily numerical and the substantial progress made during the past several years has roughly paralleled the continuing availability of more advanced supercomputers. These have become essential to accurately model the complex configurations necessary for achieving MHD stable reactor grade conditions. Appropriate tokamak MHD equilibria will be described. Then the stability properties is discussed in some detail, emphasizing the difficulties of obtaining stable high [beta] discharges in plasmas in which the current is mainly ohmically driven and thus demonstrating the need for tailoring the current and pressure profiles of the plasma away from the ohmic state. The outline of this paper will roughly follow the physics development to attain the second region of stability in the PBX-M device at The Princeton Plasmas Physics Laboratory.
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Author:
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Category :
Languages : en
Pages :
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Book Description
MHD equilibrium, stability, and transport calculations are made to study the accessibility and behavior of ''high beta'' tokamak plasmas in the range .beta. approximately 5 to 15 percent. For next generation devices, beta values of at least 8 percent appear to be accessible and stable if there is a conducting surface nearby.
