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Aiba, Nobuyuki; Tokuda, Shinji; Ishizawa, Tomoko*
Journal of Plasma Physics, 72(6), p.1127 - 1131, 2006/12
Times Cited Count：1 Percentile：3.54(Physics, Fluids & Plasmas)We develop the method for the stability analysis of a ideal external magnetohydrodynamic (MHD) mode by solving the eigenvalue problem associated with the two-dimensional Newcomb equation, the inertia free linear ideal MHD equation. This eigenvalue problem can be expected to provide a powerful tool for not only a low-n external MHD mode but also a high-n mode, where n is a toroidal mode number. With this method, we analyze an effect of the aspect ratio on the stability of middle-n (1
n10) external MHD modes in tokamaks; this gets attention for the design research of a high performance tokamak. As the result of this work, we study that external MHD modes become stable as the aspect ratio decreases, and also find that the stability of middle-n external modes becomes important because an effect of a conducting wall is enhanced by reducing the aspect ratio.
Furukawa, Masaru; Tokuda, Shinji
Nuclear Fusion, 45(5), p.377 - 383, 2005/05
Times Cited Count：10 Percentile：33.97(Physics, Fluids & Plasmas)A ballooning perturbation in a toroidally rotating tokamak is expanded by square-integrable eigenfunctions of an eigenvalue problem associated with ballooning modes in a static plasma. Especially a weight function is chosen such that the eigenvalue problem has only the discrete spectrum. The eigenvalues evolve in time owing to toroidal rotation shear, resulting in countably infinite number of crossings among them. The crossings cause energy transfer from an unstable mode to the infinite number of stable modes; such transfer works as the stabilization mechanism of the ballooning mode. A simple analytic formula is derived for estimating the toroidal rotation shear required to stabilize the ballooning mode.
Furukawa, Masaru; Tokuda, Shinji
Physical Review Letters, 94(17), p.175001_1 - 175001_4, 2005/05
Times Cited Count：18 Percentile：66.53(Physics, Multidisciplinary)A ballooning perturbation in a toroidally rotating tokamaks is expanded by square-integrable eigenfunctions of an eigenvalue problem associated with ballooning modes in a static plasma. Especially a weight function is chosen such that the eigenvalue problem has only the discrete spectrum. The eigenvalues evolve in time owing to toroidal rotation shear, resulting in countably infinite number of crossings among them. The crossings cause energy transfer from an unstable mode to the infinite number of stable modes; such transfer works as the stabilization mechanism of the ballooning mode.
Furukawa, Masaru; Tokuda, Shinji; Wakatani, Masahiro*
Plasma Physics and Controlled Fusion, 46(2), p.409 - 421, 2004/02
Times Cited Count：7 Percentile：22.88(Physics, Fluids & Plasmas)In the H-mode (high-confinement mode) pedestal region of a static or a toroidally rotating D-shaped tokamak plasma, the separatrix or the X-point affects the high-n ballooning stability (n: toroidal mode number) only in a thin layer in the pedestal region. Therefore, D-shaping effectively stabilizes the ballooning modes even for a toroidally rotating plasma with a separatrix.
Furukawa, Masaru; Tokuda, Shinji
Journal of Plasma and Fusion Research SERIES, Vol.6, p.210 - 213, 2004/00
A model equation for ballooning modes in toroidally rotating tokamaks is derived. It is confirmed that the model equation is appropriate for analyzing the stabilization mechanism of the ballooning modes by comparing the numerical solutions of the model equation with those of the original ballooning equations.
Sugihara, Masayoshi; Mukhovatov, V.*; Polevoi, A.*; Shimada, Michiya
Plasma Physics and Controlled Fusion, 45(9), p.L55 - L62, 2003/09
Times Cited Count：40 Percentile：74.93(Physics, Fluids & Plasmas)Improvement of the scaling of H-mode edge pedestal pressure for a Type-I ELM regime based on a simple analytical formula is achieved by introducing shaping factors into the scaling. The physics basis of these shaping factors is an enhancement of the critical pressure gradient by the magnetic well. With increasing the magnetic well, a high toroidal mode number ideal ballooning mode and peeling mode decouple and critical gradient is determined by intermediate mode number, which results in significant enhancement of the critical pressure gradient. The improved scaling can reproduce the pedestal pressure reasonably well for ASDEX-U, JET, DIII-D and JT-60U Type-I ELmy data archived in the ITER pedestal database.
ballooning modes in tokamaksFurukawa, Masaru; Tokuda, Shinji; Wakatani, Masahiro*
Nuclear Fusion, 43(6), p.425 - 429, 2003/06
We have found numerically that damping phases appear in the time evolution of the perturbation energy of high- ballooning modes in the presence of toroidal shear flows. The damping dominates exponential growth which occurs in the bad curvature region, resulting in stabilization of ballooning modes. D-shaping of plasma cross-section, reduction of aspect ratio, and arrangement of X-point at inner side of the torus enhance the stabilization effect of the toroidal flow through this mechanism.
ballooning modes in tokamaksFurukawa, Masaru; Tokuda, Shinji; Wakatani, Masahiro*
Nuclear Fusion, 43(6), p.425 - 429, 2003/06
Times Cited Count：10 Percentile：31.59(Physics, Fluids & Plasmas)We have found numerically that damping phases appear in the time evolution of the perturbation energy of high- ballooning modes in the presence of toriodal flow shear, where n is a toroidal mode number. The damping dominates exponential growth which occurs in the bad curvature region, resulting in stabilization of ballooning modes. D-shaping of plasma cross-section, reduction of aspect ratio, and arrangement of an X-point at inner side of the torus enhance the stabilization effect of the toroidal flow shear through this mechanism.
Idomura, Yasuhiro; Tokuda, Shinji; Kishimoto, Yasuaki
Nuclear Fusion, 43(4), p.234 - 243, 2003/04
Times Cited Count：119 Percentile：94.96(Physics, Fluids & Plasmas)no abstracts in English
Yamagiwa, Mitsuru; *
Plasma Physics and Controlled Fusion, 40(9), p.1673 - 1678, 1998/00
Times Cited Count：1 Percentile：4.02(Physics, Fluids & Plasmas)no abstracts in English
Yamagiwa, Mitsuru; *; M.Elia*
Physics of Plasmas, 4(11), p.4031 - 4034, 1997/11
Times Cited Count：2 Percentile：8.87(Physics, Fluids & Plasmas)no abstracts in English
*; Yamagiwa, Mitsuru
Canadian Journal of Physics, 75(9), p.599 - 604, 1997/09
no abstracts in English
Yamagiwa, Mitsuru; *; M.Elia*
PPL-167, p.1 - 13, 1997/08
no abstracts in English
Yamagiwa, Mitsuru; ; *; M.Elia*
JAERI-Data/Code 97-032, 15 Pages, 1997/07
JAERI-Data-Code-97-032.pdf:0.59MB
no abstracts in English
Yamagiwa, Mitsuru; Hirose, A*; Elia, M.*
PPL-163, 22 Pages, 1997/01
no abstracts in English
Yamagiwa, Mitsuru; Hirose, A*; Elia, M.*
Plasma Physics and Controlled Fusion, 39(3), p.531 - 540, 1997/00
Times Cited Count：6 Percentile：24.39(Physics, Fluids & Plasmas)no abstracts in English
Tokuda, Shinji; Ozeki, Takahisa
JAERI-Research 94-030, 13 Pages, 1994/11
JAERI-Research-94-030.pdf:0.62MB
no abstracts in English
Ishida, Shinichi; Koide, Yoshihiko; Ozeki, Takahisa; Kikuchi, Mitsuru; Tsuji, Shunji; Shirai, Hiroshi; Naito, Osamu; Azumi, Masafumi
Physical Review Letters, 68(10), p.1531 - 1534, 1992/03
Times Cited Count：54 Percentile：87.28(Physics, Multidisciplinary)no abstracts in English
; *; ;
Journal of the Physical Society of Japan, 53(5), p.1759 - 1774, 1984/00
Times Cited Count：2 Percentile：34.43(Physics, Multidisciplinary)no abstracts in English
; ; ; ; Takeda, Tatsuoki; ; ; Tsunematsu, Toshihide; *; *; et al.
Plasma Physics and Controlled Nuclear Fusion Research l984, Vol.2, p.173 - 178, 1984/00
no abstracts in English
