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Journal Articles

Basic performance tests on vibration of support structure with flexible plates for ITER tokamak device

Takeda, Nobukazu; Kakudate, Satoshi; Shibanuma, Kiyoshi

Purazuma, Kaku Yugo Gakkai-Shi, 81(4), p.312 - 316, 2005/04

http://ci.nii.ac.jp/naid/110006281933

The vibration experiments of the support structures with flexible plates for the ITER major components such as toroidal field coil and vacuum vessel were performed using small-sized flexible plates aiming to obtain its basic mechanical characteristics such as dependence of the stiffness on the loading angle. The experimental results obtained by the hammering and frequency sweep tests were agreed each other, so that the experimental method is found to be reliable. In addition, the experimental results were compared with the analytical ones in order to estimate an adequate analytical model. As a result, the bolt connection strongly affected on the stiffness of the support structure. After studies of modeling the bolts, it is found that the analytical results modeling the bolts with finite stiffness only in the axial direction and infinite stiffness in the other directions agree well with the experimental ones. Using this model, the stiffness of the support structure for the ITER major components can be calculated precisely in order to estimate the dynamic behaviors.

Journal Articles

Design and structural analysis of support structure for ITER vacuum vessel

Takeda, Nobukazu; Omori, Junji*; Nakahira, Masataka; Shibanuma, Kiyoshi

Journal of Nuclear Science and Technology, 41(12), p.1280 - 1286, 2004/12

https://doi.org/10.1080/18811248.2004.9726357

The vibration experiments of the support structures with flexible plates for the ITER major components such as toroidal field coil and vacuum vessel were performed using small-sized flexible plates aiming to obtain its basic mechanical characteristics such as dependence of the stiffness on the loading angle. The experimental results obtained by the hammering and frequency sweep tests were agreed each other, so that the experimental method is found to be reliable. In addition, the experimental results were compared with the analytical ones in order to estimate an adequate analytical model. As a result, the bolt connection strongly affected on the stiffness of the support structure. After studies of modeling the bolts, it is found that the analytical results modeling the bolts with finite stiffness only in the axial direction and infinite stiffness in the other directions agree well with the experimental ones. Using this model, the stiffness of the support structure for the ITER major components can be calculated precisely in order to estimate the dynamic behaviors.

Journal Articles

Neutron diagnostics for the energetic ion transport analysis

Nishitani, Takeo; Osakabe, Masaki*; Shinohara, Koji; Ishikawa, Masao

Purazuma, Kaku Yugo Gakkai-Shi, 80(10), p.860 - 869, 2004/10

http://ci.nii.ac.jp/naid/110003827867

no abstracts in English

Journal Articles

Theory of the Newcomb equation and applications to MHD stability analysis of a tokamak

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.

Journal Articles

Development of theory of reversed-shear alfven eigenmodes in tokamaks

Konovalov, S. V.; Mikhailovskii, A.*; Kovalishen, E.*; Ozeki, Takahisa; Takizuka, Tomonori; Shirokov, M. S.*

Proceedings of 20th IAEA Fusion Energy Conference (FEC 2004) (CD-ROM), 8 Pages, 2004/00

http://www-naweb.iaea.org/napc/physics/fec/fec2004/datasets/TH_P5-10.html

Alfven eigenmodes in tokamaks with reversed magnetic shear are studied theoretically by incorporating into the mode description the effects known theories of Global, Kinetic and Toroidal Alfven Eigenmodes. In particular mode forming effect due to thermal plasma density gradient is examined. Criteria of the fast ion density and its gradient on the existence of a localized solution of the eigenmode equation is softened by this effect. Effects of finite Larmor radius, continuum damping and fast ion density gradient are also studied.

Journal Articles

Inner layer problem for ideal MHD modes in a toroidal system

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.

Journal Articles

Energetic particle experiments in JT-60U and their implications for a fusion reactor

Tobita, Kenji; Kusama, Yoshinori; Shinohara, Koji; Nishitani, Takeo; Kimura, Haruyuki; Kramer, G. J.*; Nemoto, Masahiro*; Kondoh, Takashi; Oikawa, Toshihiro; Morioka, Atsuhiko; et al.

Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.315 - 326, 2002/09

https://doi.org/10.13182/FST02-A231

Times Cited Count：8 Percentile：47.85(Nuclear Science & Technology)

Energetic particle experiments in JT-60U are summarized, mainly covering ripple loss and Alfven eigenmodes (AE modes). Significant loss was observed for 85 keV NBI ions and fusion-produced tritons increased when toroidal field ripple at the plasma surface, especially in reversed shear plasma. Measurement of hot spots on the first wall due to ripple loss confirmed agreement with code predictions, validating the modeling incorporated in an orbit-following Monte Carlo code. A variety of AE modes were destabilized in ICRF minority heating and negative-ion-based NBI (N-NBI) heating. Most of the observed modes are gap modes identified to be TAE, EAE and NAE. Interesting finding is pulsating modes accompanying frequency sweep, which were destabilized by N-NBI and sometimes induced a beam ion loss of up to 25%. Also presented are energetic particle issues in auxiliary heating with ICRF and N-NBI.

Journal Articles

Energetic particles in spherical torus

Tobita, Kenji

Denki Gakkai Kenkyukai Shiryo, Pulazuma Kenkyukai (PST-01-73), p.43 - 46, 2001/09

Behavior of energetic particles in spherical torus (ST) is summarized in comparison with that in tokamaks. The issues treated in this article are neoclassical transport, ripple loss, Alfven eigenmodes and Magetohydrodynamic- instability-induced anomalous transport. ST is expected to be favorable in terms of neoclassical transport and ripple loss. On the other hand, Alfven eigenmodes and the resulting energetic particle loss can be serious concerns in a ST reactor because of a high volume-averaged beta and a super-Alfvenic speed of alpha particles.

Journal Articles