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Kamiya, Kensaku; Urano, Hajime; Koide, Yoshihiko; Takizuka, Tomonori; Oyama, Naoyuki; Kamada, Yutaka; JT-60 Team
Plasma Physics and Controlled Fusion, 48(5A), p.A131 - A139, 2006/05
Times Cited Count：22 Percentile：58.85(Physics, Fluids & Plasmas)Effects of plasma rotation and ripple loss on the Type-I ELMs have systematically studied in the JT-60U tokamak, scanning combinations of NBI at the three kinds of plasma volumes. New findings on the Type-I ELMs confirm to be smaller ELM energy loss per pedestal stored energy, DWELM/Wped, and faster ELM frequency, fELM, in the counter-NBI than co-NBI, keeping the power of ELM, PELM, per heating power crossing the separatrix, PSEP, constant. Balanced-NBI case is also intermediate between co- and counter-NBI. In addition, the product of PELM/PSEP decreases according to increase in the plasma volume, suggesting an increase in the inter-ELM transport due mainly to an enhancement in the ripple loss of fast ion.
Urano, Hajime; Kamiya, Kensaku; Koide, Yoshihiko; Takizuka, Tomonori; Oyama, Naoyuki; Kamada, Yutaka; JT-60 Team
Plasma Physics and Controlled Fusion, 48(5A), p.A193 - A199, 2006/05
Times Cited Count：10 Percentile：34.26(Physics, Fluids & Plasmas)The characteristics of the H-mode pedestal structure were investigated by conducting the power scans for a variation of the toroidal momentum sources at different toroidal field ripple in JT-60U. It was found that the pedestal pressure is increased by reduced loss power of fast ions, independently of toroidal rotation. However, the energy confinement is improved with the CO-directed toroidal momentum source at H-mode plasmas with small ripple loss.
Tani, Keiji; Tobita, Kenji; Nishio, Satoshi; Iio, Shunji*; Tsutsui, Hiroaki*; Aoki, Takayuki*
Purazuma, Kaku Yugo Gakkai-Shi, 80(11), p.931 - 934, 2004/11
Studies were made on ripple losses of fusion produced alpha particles in a low-aspect-ratio tokamak reactor (VECTOR) by using an orbit-following Monte-Carlo code. Alpha particles are well confined in VECTOR. In a low-aspect-ratio tokamak, the dependence of ripple losses on the number of toroidal-field (TF) coils N is very weak. Assuming a toroidal peaking factor of 2 for the heat load due to loss particles, about 1.5% and 1.0% of TF ripple at the outer edge of plasma might be allowable for the first wall with and without cooling system, respectively. In both cases, the number of TF-coils can be reduced to about 4.
Urata, Kazuhiro*; Shinohara, Koji; Suzuki, Masanobu*; Kamata, Isao*
JAERI-Data/Code 2004-007, 45 Pages, 2004/03
JAERI-Data-Code-2004-007.pdf:5.63MB
As the toroidal magnetic field generated by discrete TF coils involves magnetic field ripple, the fast ion loss is induced to damage vacuum vessel in tokamaks. An idea of ripple compensation using ferromagnetic is proposed. Since low activation ferritic steel have low activation and thermal conduction properties, the ferritic steel is planned to install in tokamak reactors. Installation of ferritic steel plates with toroidal symmetry is effective to compensate ripple, however in the actual devices it is difficult for interference with other components. Besides the first wall shapes are often asymmetric. So it is better to treat toroidal asymmetry to evaluate the ripple induced loss in the actual devices. For the purpose, magnetic field calculation code considering ferritic steel; FEMAG(FErrite generating MAGnetic field)has been speeded up. On the basis of this magnetic field data, OFMC (Orbit Following Monte Carlo) has been upgraded to treat toroidal asymmetry. The use of FEMAG/OFMC, applications to the JFT-2M experiments, and the national centralized tokamak facility are reported.
Masaki, Kei; Sugiyama, Kazuyoshi*; Tanabe, Tetsuo*; Goto, Yoshitaka*; Tobita, Kenji; Miyo, Yasuhiko; Kaminaga, Atsushi; Kodama, Kozo; Arai, Takashi; Miya, Naoyuki
Nihon Genshiryoku Gakkai Wabun Rombunshi, 2(2), p.130 - 139, 2003/06
no abstracts in English
Urata, Kazuhiro*
JAERI-Data/Code 2003-005, 36 Pages, 2003/03
JAERI-Data-Code-2003-005.pdf:2.96MB
In design of the fusion devises in which ferritic steel is planned to use as the plasma facing material and/or the inserts for ripple reduction, the appreciation of the error field effect and the optimization of ferritic plate arrangement to reduce the toroidal field ripple require calculation of ferritic magnetic field. However iterative calculations by the non-linearity in B-H curve disturbs high-speed calculation. In the strong toroidal magnetic field in the tokamak, fully magnetic saturation of ferritic steel occurs. Hence a distribution of magnetic charges as magnetic field source is determined straightforward. Additionally objective ferritic steel geometry is limited to the thin plate and they are installed along the toroidal magnetic field. Taking them into account, high-speed calculation code FEMAG has been developed. In this report, the formalization of FEMAG, how to use FEMAG, and the validity check in comparison with a 3D FEM code, with the measurements of the magnetic field in JFT-2M are described. The presented examples are design studies for JT-60 modification.
Masaki, Kei; Sugiyama, Kazuyoshi*; Tanabe, Tetsuo*; Goto, Yoshitaka*; Miyasaka, Kazutaka*; Tobita, Kenji; Miyo, Yasuhiko; Kaminaga, Atsushi; Kodama, Kozo; Arai, Takashi; et al.
Journal of Nuclear Materials, 313-316, p.514 - 518, 2003/03
Times Cited Count：55 Percentile：94.93(Materials Science, Multidisciplinary)Detailed tritium profiles on the JT-60U W-shaped divertor and first wall tiles were examined by Tritium Imaging Plate Technique (TIPT) and full combustion method. The tritium deposition image obtained by TIPT was consistent with the distribution measured by combustion method. The highest tritium concentration was 60 kBq/cm
at the dome top tile. However, deposition layer was not obviously observed on the dome top tile. The tritium concentration in the inner divertor target tile was lower (2 kBq/cm) even with the thick deposition layer of 
60 
m. This tritium distribution can be explained by energetic triton particle loss due to ripple loss. According to the simulation using the OFMC code, 31% of the triton particles produced by D-D nuclear reaction is implanted deeply to the wall without fully losing the initial energy of 1 MeV.
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
Times Cited Count：8 Percentile：47.9(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.
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.
Nishitani, Takeo; Isobe, Mitsutaka*; G.A.Wurden*; R.E.Chrien*; Tobita, Kenji; Kusama, Yoshinori; Harano, Hideki*
Fusion Engineering and Design, 34-35, p.563 - 566, 1997/00
Times Cited Count：19 Percentile：79.94(Nuclear Science & Technology)no abstracts in English
Nishitani, Takeo; Hoek, M.; Harano, Hideki*; Isobe, Mitsutaka*; Tobita, Kenji; Kusama, Yoshinori; Wurden, G. A.*; Chrien, R. E.*
Plasma Physics and Controlled Fusion, 38(3), p.355 - 364, 1996/03
Times Cited Count：36 Percentile：73.44(Physics, Fluids & Plasmas)no abstracts in English
B drift direction on ripple-induced fast ion loss in JT-60UIsobe, Mitsutaka*; Tobita, Kenji; Nishitani, Takeo; Kusama, Yoshinori; *
JAERI-Research 96-005, 11 Pages, 1996/02
JAERI-Research-96-005.pdf:0.46MB
no abstracts in English
Nishitani, Takeo; M.Hoek*; Harano, Hideki*; G.A.Wurden*; R.E.Chrien*; Isobe, Mitsutaka*; Tobita, Kenji; Kusama, Yoshinori
22nd European Physical Society Conf. on Controlled Fusion and Plasma Physics,Vol. 19C,Part II, 0, p.2.061 - 2.064, 1995/00
no abstracts in English
Takeda, Tatsuoki; Tani, Keiji; Tsunematsu, Toshihide; Kishimoto, Yasuaki; ; *; *
Parallel Computing, 18, p.743 - 765, 1992/00
Times Cited Count：2 Percentile：48.33(Computer Science, Theory & Methods)no abstracts in English
