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Tsubone, Misora*; Shimotsuma, Yasuhiko*; Kono, Yoshio*; Kakizawa, Sho*; Yamada, Hiroki*; Kobayashi, Keita; Shimizu, Masahiro*; Miura, Kiyotaka*
NPG Asia Materials, 18, p.15_1 - 15_16, 2026/04
Times Cited Count：0 Percentile：0.00(Materials Science, Multidisciplinary)Silica glass exhibits diverse structural configurations accompanied with densification under varying temperature and pressure conditions; these factors significantly influence its optical properties, such as the refractive index. However, the fundamental structural mechanisms underlying the optical properties change induced by high pressure treatment and femtosecond laser direct writing remain poorly understood. Herein, we report the similarities and differences in the optical responses of densified silica glass induced by these two methods. The most significant difference is that the laser-irradiated region evolves toward a glass structure characteristic of a high fictive temperature by incorporating non-bridging oxygen defects associated with edge-sharing SiO
tetrahedra, which induces distinctly different photoluminescence behaviors compared to high pressure treatment.
Imaizumi, Tomomi; Miyauchi, Masaru; Ito, Masayasu; Watahiki, Shunsuke; Nagata, Hiroshi; Hanakawa, Hiroki; Naka, Michihiro; Kawamata, Kazuo; Yamaura, Takayuki; Ide, Hiroshi; et al.
JAEA-Technology 2011-031, 123 Pages, 2012/01
JAEA-Technology-2011-031.pdf:16.08MB
The number of research reactors in the world is decreasing because of their aging. However, the planning to introduce the nuclear power plants is increasing in Asian countries. In these Asian countries, the key issue is the human resource development for operation and management of nuclear power plants after constructed them, and also the necessity of research reactor, which is used for lifetime extension of LWRs, progress of the science and technology, expansion of industry use, human resources training and so on, is increasing. From above backgrounds, the Neutron Irradiation and Testing Reactor Center began to discuss basic concept of a multipurpose low-power research reactor for education and training, etc. This design study is expected to contribute not only to design tool improvement and human resources development in the Neutron Irradiation and Testing Reactor Center but also to maintain and upgrade the technology on research reactors in nuclear power-related companies. This report treats the activities of the working group from July 2010 to June 2011 on the multipurpose low-power research reactor in the Neutron Irradiation and Testing Reactor Center and nuclear power-related companies.
Fujita, Takaaki; Tamai, Hiroshi; Matsukawa, Makoto; Kurita, Genichi; Bialek, J.*; Aiba, Nobuyuki; Tsuchiya, Katsuhiko; Sakurai, Shinji; Suzuki, Yutaka; Hamamatsu, Kiyotaka; et al.
Nuclear Fusion, 47(11), p.1512 - 1523, 2007/11
Times Cited Count：25 Percentile：62.16(Physics, Fluids & Plasmas)Design of modification of JT-60U, JT-60SA, has been optimized in viewpoint of plasma control, and operation regimes have been evaluated. Upper and lower divertors with different geometry are prepared for flexibility of plasma shape control. The beam lines of negative-ion NBI are shifted downward for off-axis current drive, in order to obtain a weak/reversed shear plasma. The feedback control coils along the port hole in the stabilizing plate are found effective to suppress the resistive wall mode (RWM) and sustain high 
close to the ideal wall limit. The regime of full current drive operation has been extended with upgraded heating and current drive power. Full current drive operation for 100 s with reactor-relevant high values of normalized beta and bootstrap current fraction (
= 2.4 MA, = 4.4, 
= 0.70, 
/
= 0.86, H
= 1.3) is expected in a highly-shaped low-aspect-ratio configuration (
= 2.65). High , high-density ELMy H-mode is also expected.
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.
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：39.70(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：9.39(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：43.83(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.
Ushigusa, Kenkichi; Ide, Shunsuke; Oikawa, Toshihiro; Suzuki, Takahiro; Kamada, Yutaka; Fujita, Takaaki; Ikeda, Yoshitaka; Naito, Osamu; Matsuoka, Mamoru*; Kondoh, Takashi; et al.
Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.255 - 277, 2002/09
Times Cited Count：15 Percentile：24.24(Nuclear Science & Technology)Studies on non-inductive current drive and development of an integrated steady-state high performance operation in JT-60 are reviewed. Experiments on lower hybrid current drive in JT-60 haven shown a large non-inductive current up to 3.5MA, high current drive efficiency of 3.6x1019m-2A/W. Basic studies on LH waves in JT-60 have contributed to understand current drive physics. Significant progress in neutral beam current drive has been made in JT-60 by testing the performance of negative ion based NBI (N-NBI). The CD efficiency of ~1.5x1019m-2A /W, and N-NB driven current of ~1MA have been demonstrated in N-NBCD. Strongly localized driven current by electron cyclotron current drive was identified with a fundamental O-mode scheme. Efficiency of 0.5x1019m-2A/W and EC driven current of 0.2MA were achieved and suppression of neo-classical tearing mode was demonstrated. Based on these developments, two integrated steady-state operation scenarios were developed in JT-60, which are reversed magnetic shear (R/S) plasmas and high bp ELMy H-mode. In these operation regimes, discharges have been sustained near the steady-state current profile under full non-inductive current drive. High performance plasmas with a high nDotETio and at high normalized density were also produced under fully non-inductive condition in high bp ELMy H-mode and R/S mode.
Fujita, Takaaki; Miura, Yukitoshi; Suzuki, Takahiro; Ide, Shunsuke; Takenaga, Hidenobu; Oikawa, Toshihiro; Chankin, A. V.; Sakamoto, Yoshiteru; Koide, Yoshihiko; Hatae, Takaki; et al.
Proceedings of 29th European Physical Society Conference on Plasma Physics and Controlled Fusion, 9 Pages, 2002/00
no abstracts in English
