Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Harjo, S.; Hemmi, Tsutomu; Abe, Jun; Gong, W.; Nunoya, Yoshihiko; Aizawa, Kazuya; Ito, Takayoshi*; Koizumi, Norikiyo; Machiya, Shutaro*; Osamura, Kozo*
Materials Science Forum, 777, p.84 - 91, 2014/02
Times Cited Count：2 Percentile：72.57(Materials Science, Multidisciplinary)
Sn cable-in-conduit conductorsHemmi, Tsutomu; Harjo, S.; Ito, Takayoshi; Matsui, Kunihiro; Nunoya, Yoshihiko; Koizumi, Norikiyo; Takahashi, Yoshikazu; Nakajima, Hideo; Aizawa, Kazuya; Suzuki, Hiroshi; et al.
IEEE Transactions on Applied Superconductivity, 21(3), p.2028 - 2031, 2011/06
Times Cited Count：10 Percentile：49.88(Engineering, Electrical & Electronic)Residual strain in conductors is caused by the difference in the coefficient of expansion between NbSn strands and the jacket over a temperature range of 5 - 923 K. The superconducting properties of strands vary significantly, depending on the strain. It is important to clarify the residual strain as part of the evaluation of superconducting performance. However, the residual strain of strands in the conductor has not been measured so far because of their complicated configuration and their location in a jacket. The engineering materials diffractometer "Takumi" in J-PARC can measure residual strain with a relative accuracy of around 0.02%, using neutron diffraction. In this study, the Takumi was applied to the measurement of residual strain in strands for the ITER TF conductor. Results indicate that the residual strain of strands in the conductor can be determined, thereby clarifying the mechanism of residual strain and its relationship to superconducting performance.
Ito, Takayoshi; Harjo, S.; Osamura, Kozo*; Hemmi, Tsutomu; Awaji, Satoshi*; Machiya, Shutaro*; Oguro, Hidetoshi*; Nishijima, Gen*; Takahashi, Koki*; Matsui, Kunihiro; et al.
Materials Science Forum, 681, p.209 - 214, 2011/05
Times Cited Count：1 Percentile：52.59(Materials Science, Multidisciplinary)Sn conductors for ITER Toroidal Field coilsTakahashi, Yoshikazu; Isono, Takaaki; Hamada, Kazuya; Nunoya, Yoshihiko; Nabara, Yoshihiro; Matsui, Kunihiro; Hemmi, Tsutomu; Kawano, Katsumi; Koizumi, Norikiyo; Oshikiri, Masayuki; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03
Japan Atomic Energy Agency is procuring the NbSn superconductors for Toroidal Field (TF) coils under the ITER project. Because manufacturing amount of NbSn strands is quite large compared with the past experience and required superconducting performance is higher than that of the model coils which have been fabricated and tested in the ITER-EDA, quality control technique is very important for the manufacture of the strands. Sophisticated control technique is also required for the jacketing, in order to fabricate the conductors with the precise outer diameter and without leakage at welding part. Cu dummy conductor with full length (760 m) has been fabricated successfully and all jacketing technology was confirmed through this fabrication. The fabrication of the NbSn conductor for TF coils will start in March 2010.
Sn superconducting conductors in ITERNabara, Yoshihiro; Isono, Takaaki; Nunoya, Yoshihiko; Koizumi, Norikiyo; Hamada, Kazuya; Matsui, Kunihiro; Hemmi, Tsutomu; Kawano, Katsumi; Uno, Yasuhiro*; Seki, Shuichi*; et al.
Journal of Plasma and Fusion Research SERIES, Vol.9, p.270 - 275, 2010/08
Ito, Kiyoshi*; Wada, Hiroo*; Omi, Shiro*; Hirano, Norio*; Ueno, Tomotake*
Geodynamics of Atotsugawa Fault System, p.45 - 63, 2007/00
The seismicity in the Atotsugawa fault area is studied in detail from the data of dense network stations, together with temporary station data. Since the observation network has been improved by adding new stations, the accuracy of the hypocenters has been accordingly raised by using the dense network data of temporary observations conducted by the Frontier Project. As a result, the distribution of hypocenters has greatly improved to reveal regional changes in focal depths along the fault. Besides, the characteristic features of seismicity along the Atotsugawa fault system are well derived from the high frequency and high-gain observations for about the last 30 years. Each distribution of focal depths along the Atotsugawa and Mozumi-Sukenobe faults is found to be vertical in the seismogenic zone of 15 km in depth from the detailed analyses of hypocenters. The distance between the two faults is 8 km at most. hypocenters are relatively deeper in the northwestern side of the fault zone compared to those in the southeast of the fault. These observation results, together with those of the GPS observations, lead to a model of the strain concentration along the fault zone. The model contains a detachment dipping towards the northwest in the middle or in the lower crust, where no earthquakes occur. In the Hida Mountains, shallow seismicity is well correlated with volcanoes. The seismicity in the mountains is different from those of the tectonic event for their focal depth and a maximum event size of M5.5. Detailed surveys in the Tateyama volcano area show that focal depths of earthquakes become shallower stepwise from the Atotsugawa fault system to the Hida Mountains. This suggests that the Atotsugawa fault ends at the foot of the Tateyama volcano.
Ito, Kiyoshi*; Ueno, Tomotake*; Wada, Hiroo*; Matsumura, Kazuo*
Geodynamics of Atotsugawa Fault System, p.65 - 78, 2007/00
The Atotsugawa fault system is a well-known active fault and the only active fault with a creeping section in Japan. Besides, the fault area is also thought to be a part of the "Niigata-Kobe Tectonic Zone" (NKTZ). Although seismic activities and crustal movements in the fault area have been well-studied in recent years, the mechanism of the strain concentration along the area is not still unknown. Therefore, we analyzed seismic explosion data along and across the fault system to reveal the relationship between crustal structures and seismic activity. P-wave velocity and reflectors in the crust are derived from the seismic surveys of 2000 and 2001. Furthermore, seismic surveys carried out in the Chubu district are re-analyzed to reveal reflectors in the crust. We obtained the followings for the structures and earthquake distribution along and across the fault: Most earthquakes occur only in the layer with a P-wave velocity of 6.0-6.2 km/s and seismicity is very low in the surface layer with a P-wave velocity of less than 5.8 km/s. Two distinct reflectors are located at depths of about 12-15 and 18-21 km in the crust. The shallower reflector seems to be roughly coincident with the base of the seismogenic layer and the other in the mid-crust by about 8-10 km below the cutoff of the seismicity. These two reflectors have also been found in wide areas in the Chubu district from the seismic surveys in 1981 and 1991, although the depth varies from place to place. The velocity between the two reflectors seems to be of intermittent value between the upper and lower crustal layers. The cutoff of seismicity seems to be coincident with the upper reflector.
Ninomiya, Hiromasa; Akiba, Masato; Fujii, Tsuneyuki; Fujita, Takaaki; Fujiwara, Masami*; Hamamatsu, Kiyotaka; Hayashi, Nobuhiko; Hosogane, Nobuyuki; Ikeda, Yoshitaka; Inoue, Nobuyuki; et al.
Journal of the Korean Physical Society, 49, p.S428 - S432, 2006/12
To contribute DEMO and ITER, the design to modify the present JT-60U into superconducting coil machine, named National Centralized Tokamak (NCT), is being progressed under nationwide collaborations in Japan. Mission, design and strategy of this NCT program is summarized.
Kawasuso, Atsuo; Yoshikawa, Masahito; Ito, Hisayoshi; Krause-Rehberg, R.*; Redmann, F.*; Higuchi, Takatoshi*; Betsuyaku, Kiyoshi*
Physica B; Condensed Matter, 376-377, p.350 - 353, 2006/04
Times Cited Count：13 Percentile：51.98(Physics, Condensed Matter)In this presentation, we report identification of vacancy defects in cubic and hexagonal SiC irradiated with fast electrons through electron-pisitron momentum distribution measurements and theoretical analyses. In cubic SiC isolated silicon vacancies are responsible for positron trapping. The lifetime of positrons trapped at silicon vacancies is prolonged due to the outward lattice relaxation. Because of the local tetrahedral symmetry of silicon vacancies, the observed momentum distributions are consistently explained. In the case of hexagonal SiC, one particular vacancy defects appearing after annealing of isolated silicon vacancies have dangling bonds along the c-axis. From the enhancement of positron annihilation probability with carbon 1s electrons, the above defects are attributed to carbon-vacancy-antisite-carbon complexes.
Kikuchi, Mitsuru; Tamai, Hiroshi; Matsukawa, Makoto; Fujita, Takaaki; Takase, Yuichi*; Sakurai, Shinji; Kizu, Kaname; Tsuchiya, Katsuhiko; Kurita, Genichi; Morioka, Atsuhiko; et al.
Nuclear Fusion, 46(3), p.S29 - S38, 2006/03
Times Cited Count：13 Percentile：41.68(Physics, Fluids & Plasmas)The National Centralized Tokamak (NCT) facility program is a domestic research program for advanced tokamak research to succeed JT-60U incorporating Japanese university accomplishments. The mission of NCT is to establish high beta steady-state operation for DEMO and to contribute to ITER. The machine flexibility and mobility is pursued in aspect ratio and shape controllability, feedback control of resistive wall modes, wide current and pressure profile control capability for the demonstration of the high-b steady state.
Tsuchiya, Katsuhiko; Akiba, Masato; Azechi, Hiroshi*; Fujii, Tsuneyuki; Fujita, Takaaki; Fujiwara, Masami*; Hamamatsu, Kiyotaka; Hashizume, Hidetoshi*; Hayashi, Nobuhiko; Horiike, Hiroshi*; et al.
Fusion Engineering and Design, 81(8-14), p.1599 - 1605, 2006/02
Times Cited Count：1 Percentile：9.94(Nuclear Science & Technology)no abstracts in English
plasma operationTamai, Hiroshi; Akiba, Masato; Azechi, Hiroshi*; Fujita, Takaaki; Hamamatsu, Kiyotaka; Hashizume, Hidetoshi*; Hayashi, Nobuhiko; Horiike, Hiroshi*; Hosogane, Nobuyuki; Ichimura, Makoto*; et al.
Nuclear Fusion, 45(12), p.1676 - 1683, 2005/12
Times Cited Count：15 Percentile：45.44(Physics, Fluids & Plasmas)Design studies are shown on the National Centralized Tokamak facility. The machine design is carried out to investigate the capability for the flexibility in aspect ratio and shape controllability for the demonstration of the high-beta steady state operation with nation-wide collaboration, in parallel with ITER towards DEMO. Two designs are proposed and assessed with respect to the physics requirements such as confinement, stability, current drive, divertor, and energetic particle confinement. The operation range in the aspect ratio and the plasma shape is widely enhanced in consistent with the sufficient divertor pumping. Evaluations of the plasma performance towards the determination of machine design are presented.
Kawasuso, Atsuo; Yoshikawa, Masahito; Ito, Hisayoshi; Chiba, Toshinobu*; Higuchi, Takatoshi*; Betsuyaku, Kiyoshi*; Redmann, F.*; Krause-Rehberg, R.*
Physical Review B, 72(4), p.045204_1 - 045204_6, 2005/07
Times Cited Count：16 Percentile：55.73(Materials Science, Multidisciplinary)Two-dimensional angular correlation of annihilation radiation (2D-ACAR) and coincidence Doppler broadening (CDB) of annihilation radiation measurements have been performed on electron-irradiated n-type 3C SiC in which isolated silicon vacancies are responsible for positron trapping. After irradiation, the intensity of CDB spectrum increased and decreased in low and high momentum regions, respectively. These fetures were explained by the theoretical calculation considering silicon vacancies. The center region of 2D-ACAR spectra became isotropic after iradiation, while the overall anisotropies extending within the Jones zone were conserved suggesting that isolated silicon vacancies have the tetrahedral symmetry as expected from the previous electron spin resonance study.
Kinoshita, Hirohisa; Nohara, Tsuyoshi; Nakata, Takashi*; Ikeda, Yasutaka*; Ito, Kiyoshi*; Otsuki, Kenshiro*; Sagiya, Takeshi*; Takada, Keita*; Toda, Shinji*
Katsudanso Kenkyu, (25), p.27 - 37, 2005/06
Results of numerical analyses and field studies in the epicenter area of the 2000 Tottoriken-seibu earthquake suggest that several research techniques are effective for identifying subsurface active faults unaccompanied with remarkable surface earthquake faults. Field observation of the lineaments found in the area by detailed air-photo interpretation revealed that most of them are accompanied by faults and/or dikes, and some of them show minor slips at the time of the earthquake. Crustal deformation caused by the activity of the subsurface seismogenic faults is deduced by numerical analyses based on seismic and geodetic data. The vertical deformation assumed from the height changes of the terraces along the river across the epicenter area suggests that cumulative uplift and subsidence associated with left-lateral strike-slip has been continuing. Offsets rate of the streams and uplift rate of the river terraces surfaces show good agreement with the estimate from the parameter of the earthquake faults model. Identification of active faults without clear surface evidence before occurrence of earthquakes is a difficult issue, and the techniques adopted in this study will probably provide relevant information effective to locate subsurface active faults.
Tamai, Hiroshi; Matsukawa, Makoto; Kurita, Genichi; Hayashi, Nobuhiko; Urata, Kazuhiro*; Miura, Yushi; Kizu, Kaname; Tsuchiya, Katsuhiko; Morioka, Atsuhiko; Kudo, Yusuke; et al.
Plasma Science and Technology, 6(1), p.2141 - 2150, 2004/02
Times Cited Count：2 Percentile：6.49(Physics, Fluids & Plasmas)The dominant issue for the the modification program of JT-60 (JT-60SC) is to demonstrate the steady state reactor relevant plasma operation. Physics design on plasma parameters, operation scenarios, and the plasma control method are investigated for the achievement of high-. Engineering design and the R&D on the superconducting magnet coils, radiation shield, and vacuum vessel are performed. Recent progress in such physics and technology developments is presented.
Ishida, Shinichi; Abe, Katsunori*; Ando, Akira*; Chujo, T.*; Fujii, Tsuneyuki; Fujita, Takaaki; Goto, Seiichi*; Hanada, Kazuaki*; Hatayama, Akiyoshi*; Hino, Tomoaki*; et al.
Nuclear Fusion, 43(7), p.606 - 613, 2003/07
no abstracts in English
Ishida, Shinichi; Abe, Katsunori*; Ando, Akira*; Cho, T.*; Fujii, Tsuneyuki; Fujita, Takaaki; Goto, Seiichi*; Hanada, Kazuaki*; Hatayama, Akiyoshi*; Hino, Tomoaki*; et al.
Nuclear Fusion, 43(7), p.606 - 613, 2003/07
Times Cited Count：33 Percentile：69.03(Physics, Fluids & Plasmas)no abstracts in English
Ito, Kiyoshi
Geophysical Research Letters, 0 Pages, 2002/00
None
Ito, Kiyoshi
Seismogenic Process Monitoring, p.229 - 243, 2002/00
None
