2007 Fiscal Year Final Research Report Summary
Study of Plasma Transport and Zonal Flows Based on Gyrofluid and Gyrokinetic Models
| Project/Area Number |
16560727
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Nuclear fusion studies
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| Research Institution | National Institute for Fusion Science |
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Principal Investigator |
SUGAMA Hideo National Institute for Fusion Science, Department of Large Helical Device Project, Professor (80202125)
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| Co-Investigator(Kenkyū-buntansha) |
WATANABE Tomo-Hiko National Institute of Fusion Science, Theory and Computer Simulation Center, Associate Professor (30260053)
SHINSUKE Satake National Institute of Fusion Science, Department of Large Helical Device Project, Research Associate (70390630)
YAMAGISHI Osamu National Institute of Fusion Science, Department of Large Helical Device Project, Research Associate (20413990)
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| Project Period (FY) |
2004 – 2007
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| Keywords | gyrokinetics / gyrofluid model / zonal flow / turbulent transport / ITG mode / neoclassical transport |
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| Research Abstract |
Kinetic-Fluid Model of Zonal Flows
A novel kinetic-fluid model is presented, which describes collisionless time evolution of zonal flows in tokamaks. In the new zonal-flow closure relations, the parallel heat fluxes are written by the sum of short- and long-time-evolution parts. It is shown analytically and numerically that, when applied to the zonal flow driven by either ion or electron temperature gradient turbulence, the kinetic-fluid equations including the new closure relations can reproduce the same long-time zonal-flow responses to the initial condition and to the turbulence source as those obtained from the gyrokinetic model.
Gyrokinetic Theory and Simulation of Turbulent Transport and Zonal Flows
Gyrokinetic theory and simulation studies are done to investigate regulation of ion temperature gradient (ITG) turbulence due to ExB zonal flows in tokamaks and helical systems. In order to examine effects of changes in helical magnetic configuration on anomalous transport and zonal flow
… More
s, magnetic field parameters representing the standard and inward-shifted configurations of the Large Helical Device (LHD) are used. The linear gyrokinetic analyses show that the largest growth rate of the linear ITG instability for the inward-shifted configuration is slightly higher than that in the standard one while, as theoretically predicted, zonal flows generated by given sources keep larger values for longer time for the inward-shifted case because of a smaller safety factor, a lower aspect ratio, and slower radial drift velocities of helical-ripple-trapped particles. It is shown from the gyrokinetic Vlasov simulation of the ITG turbulence that, in spite of the higher ITG-mode growth rate, the inward-shifted plasma takes a smaller average value of the ion thermal diffusivity in the steady turbulent state with a higher zonal-flow level. These results imply that neoclassical optimization contributes to reduction of the anomalous transport by enhancing the zonal-flow level and give a physical explanation for the confinement improvement observed in the LHD experiments with the inward plasma shift.
Neoclassical Transport
A detailed comparison is made between moment-equation methods presented by Sugama and by Taguchi for calculating neoclassical transport coefficients in general toroidal plasmas including nonsymmetric systems. In both methods, the Laguerre polynomials of the energy variable are employed to expand the guiding-center distribution function and to obtain the moment equations, by which the radial neoclassical transport fluxes and the parallel flows are related to the thermodynamic forces. The methods are given here in the forms applicable for an arbitrary truncation number of the Laguerre-polynomial expansion so that their accuracies can be improved by increasing the truncation number. At each order of the truncation, the neoclassical transport coefficients obtained from the Sugama-Nishimura method show the Onsager symmetry and satisfy ambipolar-diffusion condition intrinsically for symmetric systems Less
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[Presentation] Dynamics of Zonal Flows in Helical Systems2005
Author(s)
H. Sugama, T.-H. Watanabe
Organizer
Joint Meeting of 2nd 21COE Plasma Theory Workshop and US-Japan JIFT Workshop on Progress of theoretical analyses in three dimensional configurations
Place of Presentation
Kyoto, Japan
Year and Date
20050125-27
Description
「研究成果報告書概要(欧文)」より
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