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Al
GaO
scintillators by gamma-ray-induced positron annihilation lifetime spectroscopyFujimori, Kosuke*; Kitaura, Mamoru*; Taira, Yoshitaka*; Fujimoto, Masaki*; Zen, H.*; Watanabe, Shinta*; Kamada, Kei*; Okano, Yasuaki*; Kato, Masahiro*; Hosaka, Masahito*; et al.
Applied Physics Express, 13(8), p.085505_1 - 085505_4, 2020/08
Times Cited Count：5 Percentile：33.01(Physics, Applied)To clarify the existence of cation vacancies in Ce-doped GdAlGaO (Ce:GAGG) scintillators, we performed gamma-ray-induced positron annihilation lifetime spectroscopy (GiPALS). GiPAL spectra of GAGG and Ce:GAGG comprised two exponential decay components, which were assigned to positron annihilation at bulk and defect states. By an analogy with Ce:YAl
O, the defect-related component was attributed to Al/Ga-O divacancy complexes. This component was weaker for Ce, Mg:GAGG, which correlated with the suppression of shallow electron traps responsible for phosphorescence. Oxygen vacancies were charge compensators for Al/Ga vacancies. The lifetime of the defect-related component was significantly changed by Mg co-doping. This was understood by considering aggregates of Mg
ions at Al/Ga sites with oxygen vacancies, which resulted in the formation of vacancy clusters.
Yamauchi, Kunihito; Okano, Jun; Shimada, Katsuhiro; Omori, Yoshikazu; Terakado, Tsunehisa; Matsukawa, Makoto; Koide, Yoshihiko; Kobayashi, Kazuhiro; Ikeda, Yoshitaka; Fukumoto, Masahiro; et al.
JAEA-Technology 2015-053, 36 Pages, 2016/03
JAEA-Technology-2015-053.pdf:8.33MB
The superconducting Satellite Tokamak machine "JT-60SA" under construction in Naka Fusion Institute is an international collaborative project between Japan (JA) and Europe (EU). The contributions for this project are based on the supply of components, and thus European manufacturer shall conduct the installation, commissioning and tests on Naka site. This means that Japan Atomic Energy Agency (JAEA) had a quite difficult issue to manage the works by European workers and their safety although there is no direct contract. This report describes the approaches for the work and safety managements, which were agreed with EU after the tough negotiation, and then the completed on-site works for Quench Protection Circuits (QPC) as the first experience for EU in JT-60SA project. With the help of these approaches by JAEA, the EU works for QPC were successfully completed with no accident, and a great achievement was made for both EU and JA.
Shimada, Katsuhiro; Omori, Yoshikazu; Okano, Jun; Matsukawa, Tatsuya; Terakado, Tsunehisa; Kurihara, Kenichi
JAEA-Technology 2008-031, 38 Pages, 2008/03
JAEA-Technology-2008-031.pdf:10.84MB
In JT-60SA, Toroidal Field coil (TF coil) and Poloidal Field coils (PF coils) are superconducting coils and a long-pulse plasma operation with more than 100s flattop is assumed. Corresponding to the superconducting TF and PF coils, new DC power supply system in JT-60SA is necessary. The DC power supply system is composed of the reused JT-60 power supply components and newly manufactured ones to reduce total cost. A quench protection circuit is newly introduced to fast discharge coil magnetic stored energy. This paper describes the initial design study of JT-60SA DC power supply system for TF and PF coils in Japan Atomic Energy Agency (JAEA).
Matsukawa, Makoto; Miura, Yushi; Shimada, Katsuhiro; Terakado, Tsunehisa; Okano, Jun; Isono, Takaaki; Nunoya, Yoshihiko
IEEE Transactions on Applied Superconductivity, 14(2), p.1414 - 1417, 2004/06
Times Cited Count：5 Percentile：32.92(Engineering, Electrical & Electronic)no abstracts in English
Hosogane, Nobuyuki; Ninomiya, Hiromasa; Matsukawa, Makoto; Ando, Toshiro; Neyatani, Yuzuru; Horiike, Hiroshi*; Sakurai, Shinji; Masaki, Kei; Yamamoto, Masahiro; Kodama, Kozo; et al.
Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.368 - 385, 2002/09
Times Cited Count：2 Percentile：17.03(Nuclear Science & Technology)This paper reviews developments of the JT-60U tokamak and coil power supplies and their operational experiences obtained to date. The JT-60U is a large tokamak upgraded from the original JT-60 to obtain high plasma current, large plasma volume and highly elongated divertor configurations. In the modification, all components inside the bore of toroidal magnetic field coils, a vacuum vessel, poloidal magnetic field coils (PF-coils), divertor etc., were renewed. Furthermore, boron carbide converted CFC tiles were used as divertor tiles to reduce erosion of carbon-base tiles. Later, a semi-closed divertor with pumps was installed in the replacement of the open divertor. Various technologies and ideas introduced to develop these components their operational experiences provide important data for designing future tokamaks. Also, major troubles that had influence on the JT-60U operations are described. As a maintenance issue for tokamaks using deuterium fueling gas, a method for reducing radiation exposure of in-vessel workers are introduced.
Omori, Yoshikazu; Matsukawa, Makoto; Omori, Shunzo; Terakado, Tsunehisa; Okano, Jun; Noda, Masaaki*
NIFS-MEMO-36, p.358 - 361, 2002/06
no abstracts in English
Kato, Takashi; Tsuji, Hiroshi; Ando, Toshinari; Takahashi, Yoshikazu; Nakajima, Hideo; Sugimoto, Makoto; Isono, Takaaki; Koizumi, Norikiyo; Kawano, Katsumi; Oshikiri, Masayuki*; et al.
Fusion Engineering and Design, 56-57, p.59 - 70, 2001/10
Times Cited Count：17 Percentile：74.85(Nuclear Science & Technology)no abstracts in English
Terakado, Tsunehisa; Okano, Jun; Shimada, Katsuhiro; Miura, Yushi; Yamashita, Yoshiki*; Matsukawa, Makoto; Hosogane, Nobuyuki; Tsuji, Hiroshi; Ando, Toshinari*; Takahashi, Yoshikazu; et al.
JAERI-Tech 2001-056, 24 Pages, 2001/08
JAERI-Tech-2001-056.pdf:1.17MB
no abstracts in English
Tsuji, Hiroshi; Okuno, Kiyoshi*; Thome, R.*; Salpietro, E.*; Egorov, S. A.*; Martovetsky, N.*; Ricci, M.*; Zanino, R.*; Zahn, G.*; Martinez, A.*; et al.
Nuclear Fusion, 41(5), p.645 - 651, 2001/05
Times Cited Count：57 Percentile：83.02(Physics, Fluids & Plasmas)no abstracts in English
Matsukawa, Makoto; Ishida, Shinichi; Sakasai, Akira; Kurita, Genichi; Miura, Yushi; Terakado, Tsunehisa; Omori, Yoshikazu; Omori, Shunzo; Okano, Jun; Shimada, Katsuhiro; et al.
Fusion Technology, 39(2-Part2), p.1106 - 1110, 2001/03
no abstracts in English
Nishio, Satoshi; Ueda, Shuzo; Kurihara, Ryoichi; Kuroda, Toshimasa*; Miura, H.*; Sako, Kiyoshi*; Takase, Kazuyuki; Seki, Yasushi; Adachi, Junichi*; Yamazaki, Seiichiro*; et al.
Fusion Engineering and Design, 48(3-4), p.271 - 279, 2000/09
Times Cited Count：17 Percentile：72(Nuclear Science & Technology)no abstracts in English
Matsukawa, Makoto; Miura, Yushi; Terakado, Tsunehisa; Okano, Jun; Kimura, Toyoaki
IEEE Transactions on Applied Superconductivity, 10(1), p.1410 - 1413, 2000/03
Times Cited Count：3 Percentile：29.75(Engineering, Electrical & Electronic)no abstracts in English
Matsukawa, Makoto; Terakado, Tsunehisa; Okano, Jun; *; Miura, Yushi; Neyatani, Yuzuru; Kimura, Toyoaki
Proceedings of 17th IEEE/NPSS Symposium Fusion Engineering (SOFE'97), 1, p.548 - 551, 1998/00
no abstracts in English
Omori, Yoshikazu; Kurihara, Kenichi; Matsukawa, Makoto; Terakado, Tsunehisa; Okano, Jun; Furukawa, Hiroshi
no journal, ,
no abstracts in English
Shimada, Katsuhiro; Terakado, Tsunehisa; Omori, Yoshikazu; Okano, Jun; Furukawa, Hiroshi; Shibata, Kazuyuki; Terakado, Hiroyuki; Shibata, Takatoshi; Matsukawa, Makoto; Kurihara, Kenichi
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Yamauchi, Kunihito; Shimada, Katsuhiro; Okano, Jun; Omori, Yoshikazu; Terakado, Tsunehisa; Kurihara, Kenichi
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Shimada, Katsuhiro; Terakado, Tsunehisa; Omori, Yoshikazu; Okano, Jun; Yamauchi, Kunihito; Kurihara, Kenichi
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Matsukawa, Makoto; Shimada, Katsuhiro; Terakado, Tsunehisa; Yamauchi, Kunihito; Omori, Yoshikazu; Okano, Jun
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Okano, Jun; Terakado, Tsunehisa
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Taira, Yoshitaka*; Fujimoto, Masaki*; Fujimori, Kosuke*; Kitaura, Mamoru*; Zen, H.*; Okano, Yasuaki*; Hosaka, Masahito*; Yamazaki, Junichiro*; Kato, Masahiro*; Hirade, Tetsuya; et al.
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For general positron sources, radioisotopes such as 
Na are often used. However, there is a problem that positrons cannot probe the deep region of metal materials with a thickness of 1 mm or more. Gamma-ray induced positron annihilation lifetime measurement (GiPALS) is a method for generating positrons in bulk samples with a thickness of several centimeters and samples placed in vessels such as high temperature and/or pressure furnaces. The annihilation lifetime of positrons is about 200 ps for metal materials, so it is important to use gamma rays with a shorter pulse width for GiPALS in order to accurately measure the positron lifetime. We have succeeded in the proof-of-principle experiment for GiPALS of ultra-short pulse gamma rays with a pulse width of 2 ps, which was originally developed using 90
collision laser Compton scattering at UVSOR.
