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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：3.39(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.
Matsumoto, Taro; Naito, Hiroshi*; Tokuda, Shinji; Kishimoto, Yasuaki*
Nuclear Fusion, 45(11), p.1264 - 1270, 2005/11
Times Cited Count：15 Percentile：43.88(Physics, Fluids & Plasmas)A gyrokinetic particle simulation is executed to clarify the effect of the electron inertia on the MHD phenomena in the reversed shear configuration (RSC) of a cylindrical tokamak plasma. It is found that the collisionless (kinetic) double tearing modes grow up at the Alfv
n time scale, and nonlinearly induce the internal collapse when the helical flux at the magnetic axis is less than that at the outer resonant surface. After the internal collapse, the secondary reconnection is induced by the current concentration due to the 
convective flow. It is also clarified that a nonlinear dynamics accompanied with the elementary processes caused by the flow can generate a new RSC with resonant surfaces. In the presence of the density gradient, after the full reconnection induced by the mode, the radial electric field is found to be generated due to the difference of the 
motion between ions and electrons. However, the intensity of the radial field is not so large as that induced by the collisionless kink mode.
Aiba, Nobuyuki*; Tokuda, Shinji; Ishizawa, Tomoko*; Okamoto, Masao*
Plasma Physics and Controlled Fusion, 46(11), p.1699 - 1721, 2004/11
Times Cited Count：3 Percentile：9.60(Physics, Fluids & Plasmas)The theory of the Newcomb equation has been applied to low-n external modes in a tokamak and a method has been developed to compute the stability matrix that gives the change of plasma potential energy due to external modes in terms of the surface values of the perturbations. By using this method, the spectral properties of the ideal external modes has been elucidated, such as coupling between external modes and internal modes, and the difference of the stability properties between a normal shear tokamak and a reversed shear tokamak. These results will be also useful in the stability analysis of resistive wall modes.
Tokuda, Shinji; Aiba, Nobuyuki*
Journal of Plasma and Fusion Research SERIES, Vol.6, p.207 - 209, 2004/00
Recent progress in the theory of the Newcomb equation is reported. Emphasis is put on the analysis of external modes including peeling modes (high 
kink modes), where is the toroidal mode number. A theory for low external modes is developed so that it is also useful for the analysis of resistive wall modes.
Mukhovatov, V.*; Shimada, Michiya; Chudnovskiy, A. N.*; Costley, A. E.*; Gribov, Y.*; Federici, G.*; Kardaun, O. J. F.*; Kukushkin, A. S.*; Polevoi, A. R.*; Pustovitov, V. D.*; et al.
Plasma Physics and Controlled Fusion, 45(12), p.235 - 252, 2003/12
Times Cited Count：70 Percentile：86.84(Physics, Fluids & Plasmas)ITER will be the first magnetic confinement device with burning DT plasma and fusion power of about 0.5 GW. During the past few years, new results have been obtained that substantiate the confidence in achieving Q 
10 in ITER with inductive H-mode operation. These include achievement of a good H-mode confinement near the Greenwald density at high triangularity of the plasma cross section; improvements in theory-based confinement projections for the core plasma; improvement in helium ash removal due to the elastic collisions of He atoms with D/T ions in the divertor predicted by modelling; demonstration of feedback control of NTMs and resultant improvement in the achievable beta-values; better understanding of ELM physics and development of ELM mitigation techniques; and demonstration of mitigation of plasma disruptions. ITER will have a flexibility to operate also in steady state and intermediate (hybrid) regimes. The paper concentrates on inductively driven plasma performance and discusses requirements for steady-state operation in ITER.
JT-60 Team
JAERI-Review 2003-029, 197 Pages, 2003/11
JAERI-Review-2003-029.pdf:13.06MB
no abstracts in English
Kurita, Genichi; Tsuda, Takashi; Azumi, Masafumi; Ishida, Shinichi; Takeji, Satoru*; Sakasai, Akira; Matsukawa, Makoto; Ozeki, Takahisa; Kikuchi, Mitsuru
Nuclear Fusion, 43(9), p.949 - 954, 2003/09
Times Cited Count：32 Percentile：66.20(Physics, Fluids & Plasmas)In order to improve economic and environmental suitability of tokamak fusion reactors, both the accomplishment of high beta plasmas and the practical use of low activation materials to reduce the amount of radioactive waste are crucially important. Low radio-activation ferritic steel is considered as a most promising candidate for structural material in DEMO reactors, and there is the possibility of reduction of critical beta value by the deterioration of MHD stability due to ferromagnetism of ferritic steel. This paper investigates the effect of ferromagnetism with plasma flow on the beta limit of tokamak plasma by carrying out MHD stability analyses including ferromagnetic and plasma flow effects.
Konovalov, S. V.; Mikhailovskii, A. B.*; Tsypin, V. S.*; Galv
o, R. M. 0.*; Nascimento, I. C.*
Plasma Physics Reports, 29(9), p.779 - 784, 2003/09
Times Cited Count：2 Percentile：5.88(Physics, Fluids & Plasmas)The problem of drift stabilization of internal resistive-wall modes (RWMs) in tokamaks is theoretically investigated. The basic assumption of our model is that these modes are unstable in the absence of a conducting wall and stable in the presence of a close-fitting ideally conducting wall, when drift effects are neglected. Stability of the internal RWMs, was estimated for several existing tokamaks contributing to the ITER data base, namely, AUG (ASDEX-Upgrade), DIII-D, JET, TFTR and JT-60U, as well as for the projected ITER-FEAT. It is concluded that although drift effects do not stabilize the internal RWMs in current devices, they should be effective for suppressing these modes in reactor-grade tokamaks.
Tokuda, Shinji
Proceedings of 30th EPS Conference on Controlled Fusion and Plasma Physics (CD-ROM), 4 Pages, 2003/00
When we solve the eigenvalue problem associated with the two-dimensional Newcomb equation, we can identify the stability of a tokamak plasma against ideal MHD perturbations. The eigenvalue problem does not give the physical growth rate when the plasma is unstable. However, we can determine the growth rate by constructing a dispersion relation that gives the relation between the growth rate and the eigenvalue. It is expected that the dispersion relation provides an effective and fast method of stability analysis of MHD modes close to the marginal stability against ideal MHD perturbations, and the relation can be extended for non-ideal MHD modes close to the marginal stability.
Takeji, Satoru; Isayama, Akihiko; Ozeki, Takahisa; Tokuda, Shinji; Ishii, Yasutomo; Oikawa, Toshihiro; Ishida, Shinichi; Kamada, Yutaka; Neyatani, Yuzuru; Yoshino, Ryuji; et al.
Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.278 - 297, 2002/09
Times Cited Count：7 Percentile：3.03(Nuclear Science & Technology)no abstracts in English
Smolyakov, A. I.; Lazzaro, E.*; Coelho, R.*; Ozeki, Takahisa
Physics of Plasmas, 9(1), p.371 - 374, 2002/01
Times Cited Count：8 Percentile：26.51(Physics, Fluids & Plasmas)no abstracts in English
Tokuda, Shinji
Theory of Fusion Plasmas, p.87 - 102, 2002/00
We report on recent development of solution methods of the Newcomb equation and boundary layer equations, which play important roles in MHD stability analysis of a tokamak. Especially, the two-dimensional Newcomb equation is applied to external modes and the method is desctribed for computing the stability matrix of the external modes.
Ozeki, Takahisa; Isayama, Akihiko
Purazuma, Kaku Yugo Gakkai-Shi, 77(5), p.409 - 419, 2001/05
Neoclassical tearing modes (NTMs) which are induced by lack of the bootstrap current inside the magnetic island are reviewed based on the modified Rutherford equation. Theoretical bases and experimental observations of NTM are described. The beta value scaling of the growth of NTM and the mechanism of the growth are discussed. Influence of NTM on energy confinement is described, and the stabilization of NTM by electron cyclotron current drive (ECCD) is introduced.
Tokuda, Shinji
Purazuma, Kaku Yugo Gakkai-Shi, 77(3), p.276 - 283, 2001/03
no abstracts in English
Tokuda, Shinji
Journal of Accelerator and Plasma Research, 5(1), p.87 - 108, 2000/00
no abstracts in English
Tokuda, Shinji;
Physics of Plasmas, 6(8), p.3012 - 3026, 1999/08
Times Cited Count：59 Percentile：83.25(Physics, Fluids & Plasmas)no abstracts in English
ITER Physics Expert Group on Disruptions, Plasma Control, and MHD
Nuclear Fusion, 39(12), p.2251 - 2389, 1999/00
no abstracts in English
Ozeki, Takahisa
Purazuma, Kaku Yugo Gakkai-Shi, 74(9), p.998 - 1005, 1998/09
no abstracts in English
p mode plasmas in the Japan Atomic Energy Research Institute Tokamak-60 upgradeTakeji, Satoru; Kamada, Yutaka; Ozeki, Takahisa; Ishida, Shinichi; Takizuka, Tomonori; Neyatani, Yuzuru; Tokuda, Shinji
Physics of Plasmas, 4(12), p.4283 - 4291, 1997/12
Times Cited Count：16 Percentile：48.94(Physics, Fluids & Plasmas)no abstracts in English
Tokuda, Shinji;
JAERI-Data/Code 97-040, 105 Pages, 1997/10
JAERI-Data-Code-97-040.pdf:2.32MB
no abstracts in English
