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Goto, Yoshitaka*; Tanabe, Tetsuo*; Ishimoto, Yuki*; Masaki, Kei; Arai, Takashi; Kubo, Hirotaka; Tsuzuki, Kazuhiro*; Miya, Naoyuki
Journal of Nuclear Materials, 357(1-3), p.138 - 146, 2006/10
Times Cited Count：27 Percentile：85.58(Materials Science, Multidisciplinary)no abstracts in English
Ishimoto, Yuki; Goto, Yoshitaka*; Arai, Takashi; Masaki, Kei; Miya, Naoyuki; Oyama, Naoyuki; Asakura, Nobuyuki
Journal of Nuclear Materials, 350(3), p.301 - 309, 2006/05
Times Cited Count：21 Percentile：80.09(Materials Science, Multidisciplinary)Thermal properties of the redeposition layer on the inner plate of the W-shaped divertor of JT-60U have been measured with laser flash method for the first time so as to estimate transient heat loads onto the divertor. Measurement of a redeposition layer sample of more than 200 m thick showed following results: (1) the bulk density of the redeposition layer is about half of that of carbon fiber composite material; (2) the specific heat of the layer is roughly equal to that of the isotropic graphite; (3) the thermal conductivity of the redeposition layer is two orders of magnitude smaller than that of the carbon fiber composite. The difference between the divertor heat loads and the loss of the plasma stored energy becomes smaller taking account of thermal properties of the redeposition layer on the inner divertor, whereas estimated heat loads due to the ELMs is still larger than the loss. This is probably caused by the poloidal distribution of the thermal properties and heat flux asymmetry inherent in the device.
Hayashi, Takao; Ochiai, Kentaro; Masaki, Kei; Goto, Yoshitaka*; Kutsukake, Chuzo; Arai, Takashi; Nishitani, Takeo; Miya, Naoyuki
Journal of Nuclear Materials, 349(1-2), p.6 - 16, 2006/02
Times Cited Count：10 Percentile：56.98(Materials Science, Multidisciplinary)Deuterium concentrations and depth profiles in plasma-facing graphite tiles used in the divertor of JT-60U were investigated by NRA. The highest deuterium concentration of D/
C of 0.053 was found in the outer dome wing tile, where the deuterium accumulated probably through the deuterium-carbon co-deposition. In the outer and inner divertor target tiles, the D/C data were lower than 0.006. Additionally, the maximum (H+D)/C in the dome top tile was estimated to be 0.023 from the results of NRA and SIMS. OFMC simulation showed energetic deuterons caused by NBI were implanted into the dome region with high heat flux. Furthermore, the surface temperature and conditions such as deposition and erosion significantly influenced the accumulation process of deuterium. The deuterium depth profile, SEM observation and OFMC simulation indicated the deuterium was considered to accumulate through three processes: the deuterium-carbon co-deposition, the implantation of energetic deuterons and the deuterium diffusion into the bulk.
Oya, Yasuhisa*; Hirohata, Yuko*; Tanabe, Tetsuo*; Shibahara, Takahiro*; Kimura, Hiromi*; Oyaizu, Makoto*; Arai, Takashi; Masaki, Kei; Goto, Yoshitaka*; Okuno, Kenji*; et al.
Fusion Engineering and Design, 75-79, p.945 - 949, 2005/11
Times Cited Count：9 Percentile：53.19(Nuclear Science & Technology)no abstracts in English
Hirohata, Yuko*; Shibahara, Takahiro*; Tanabe, Tetsuo*; Oya, Yasuhisa*; Arai, Takashi; Goto, Yoshitaka*; Masaki, Kei; Yagyu, Junichi; Oyaizu, Makoto*; Okuno, Kenji*; et al.
Fusion Science and Technology, 48(1), p.557 - 560, 2005/07
Times Cited Count：3 Percentile：24.22(Nuclear Science & Technology)no abstracts in English
Yagisawa, Hiroshi; Arai, Takashi; Goto, Yoshitaka*
Heisei-16-Nendo Osaka Daigaku Sogo Gijutsu Kenkyukai Hokokushu (CD-ROM), 4 Pages, 2005/03
no abstracts in English
Masaki, Kei; Sugiyama, Kazuyoshi*; Hayashi, Takao; Ochiai, Kentaro; Goto, Yoshitaka*; Shibahara, Takahiro*; Hirohata, Yuko*; Oya, Yasuhisa*; Miya, Naoyuki; Tanabe, Tetsuo*
Journal of Nuclear Materials, 337-339, p.553 - 559, 2005/03
Times Cited Count：26 Percentile：84.04(Materials Science, Multidisciplinary)no abstracts in English
Hirohata, Yuko*; Shibahara, Takahiro*; Tanabe, Tetsuo*; Arai, Takashi; Goto, Yoshitaka*; Oya, Yasuhisa*; Yoshida, Hajime*; Morimoto, Yasutomi*; Yagyu, Junichi; Masaki, Kei; et al.
Journal of Nuclear Materials, 337-339, p.609 - 613, 2005/03
Times Cited Count：13 Percentile：65.42(Materials Science, Multidisciplinary)no abstracts in English
Ochiai, Kentaro; Hayashi, Takao; Kutsukake, Chuzo; Goto, Yoshitaka*; Masaki, Kei; Arai, Takashi; Miya, Naoyuki; Nishitani, Takeo
Journal of Nuclear Materials, 329-333(Part1), p.836 - 839, 2004/08
Times Cited Count：4 Percentile：29.26(Materials Science, Multidisciplinary)no abstracts in English
impurity deposition on the JT-60 divertor tilesMasaki, Kei; Yagyu, Junichi; Miyo, Yasuhiko; Goto, Yoshitaka*; Arai, Takashi; Hayashi, Takao; Kodama, Kozo; Sasajima, Tadayuki; Kaminaga, Atsushi; Tanabe, Tetsuo*; et al.
Journal of Nuclear Materials, 329-333(Part1), p.845 - 848, 2004/08
Times Cited Count：0 Percentile：0.01(Materials Science, Multidisciplinary)no abstracts in English
Goto, Yoshitaka*; Arai, Takashi; Yagyu, Junichi; Masaki, Kei; Kodama, Kozo; Miya, Naoyuki
Journal of Nuclear Materials, 329-333(1), p.840 - 844, 2004/08
Times Cited Count：15 Percentile：68.2(Materials Science, Multidisciplinary)TEM and Selected Area Diffraction (SAD) were made on nm-structures of redeposition layers on graphite tiles used in the lower-X-point divertor of JT-60. The tiles were used in the 1988 experimental campaign in which 300 divertor discharges and 1500 limiter discharges were made. TEM observations were made at poloidal and/or toroidal sections at two positions on the inboard side of the inner-separatrix strike point. Layer structures in 0-6micron depths were correlated to the last 40-shots in the campaign. Columnar structures corresponded to divertor discharges of additional heating power below 10MW. Lamellar structures were due to limiter discharges or to the higher power divertor discharges. Carbon-Mo, Ti or carbon-Ni, Fe, Cr, Ti codeposition layers were ascribed to disruptive shots. From analyses on poloidal orientation of the column axes and graphene sheets composing columns, the observed columnar structures were ascribed to both low adatom-migration due to the low deposition temperatures and also to self-shadowing effects due to inclined incidence of carbon impurity ions.
Goto, Yoshitaka*
Kaku Yugoro, (11), p.34 - 37, 2004/03
Recent results of erosion and re-deposition studies are reported for graphite tiles from W-shaped divertor region of JT-60U. The tiles were operated in Jun. 1997 - Oct. 1998 periods in which more than 3000 D-D discharge experiments were made with all-carbon walls with 2-times boronizations and inner-private flux pumping. Erosion depth was estimated by using dial gauge, while deposition was measured with SEM. On the outer divertor target, erosion was found dominant, while on the inner target, re-deposition was found to be dominant. No continuous deposition layers on the dome top. Observed in/out asymmetry is attributable to in/out asymmetry of plasma particle conditions in front of the divertor plates. Columnar structures in the redeposition layers corresponded to the lower heat-flux zone, while lamellar structures were found in the overlayers in the higher heat-flux zone near the separatrix strike point.
Yagisawa, Hiroshi; Arai, Takashi; Goto, Yoshitaka*; Kaminaga, Atsushi; Miya, Naoyuki
KEK Proceedings 2003-16 (CD-ROM), 4 Pages, 2004/02
no abstracts in English
Oya, Yasuhisa*; Morimoto, Yasutomi*; Oyaizu, Makoto*; Hirohata, Yuko*; Yagyu, Junichi; Miyo, Yasuhiko; Goto, Yoshitaka*; Sugiyama, Kazuyoshi*; Okuno, Kenji*; Miya, Naoyuki; et al.
Physica Scripta, T108, p.57 - 62, 2004/00
no abstracts in English
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
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.
Oya, Yasuhisa*; Hirohata, Yuko*; Morimoto, Yasutomi*; Yoshida, Hajime*; Kodama, Hiroshi*; Kizu, Kaname; Yagyu, Junichi; Goto, Yoshitaka*; Masaki, Kei; Okuno, Kenji*; et al.
Journal of Nuclear Materials, 313-316, p.209 - 213, 2003/03
Times Cited Count：25 Percentile：82.89(Materials Science, Multidisciplinary)no abstracts in English
Goto, Yoshitaka*; Yagyu, Junichi; Masaki, Kei; Kizu, Kaname; Kaminaga, Atsushi; Kodama, Kozo; Arai, Takashi; Tanabe, Tetsuo*; Miya, Naoyuki
Journal of Nuclear Materials, 313-316, p.370 - 376, 2003/03
Times Cited Count：46 Percentile：92.95(Materials Science, Multidisciplinary)Erosion and re-deposition were studied for graphite tiles from W-shaped divertor region of JT-60U in Jun. 1997 - Oct. 1998 periods in which more than 3000 D-D discharges were made with all-carbon wall with boronizations and inner-private flux pumping. On the outer divertor targets, erosion was dominant: maximum erosion depth of around 20 micrometers was measured, while on the inner targets, re-deposition was dominant: columnar structure layers and laminar/columnar-layered structures of maximum thickness around 60 micrometers were found. Through XPS analysis, compositions of the re-deposition layers at a around mid point on the inner target were 94 - 95 at% C, 3 - 4 at% B, and less than 0.6 at% O, Fe, Cr, and Ni. Boron is mainly bound to Carbon. No continuous deposition layers on the dome top/outer wing, while deposition layers were found on the inner wing. Observed in/out asymmetry is attributable to in/out asymmetry of plasma particle conditions in the divertor region.
Yagyu, Junichi; Goto, Yoshitaka*; Arai, Takashi; Miya, Naoyuki; Morimoto, Yasutomi*; Okuno, Kenji*; Oya, Yasuhisa*; Hirohata, Yuko*; Tanabe, Tetsuo*
Heisei-15-Nendo Kiki, Bunseki Gijutsu Kenkyukai Hokoku, p.105 - 108, 2003/00
no abstracts in English
Miyo, Yasuhiko; Goto, Yoshitaka*; Yagyu, Junichi; Masaki, Kei; Miya, Naoyuki
Heisei-15-Nendo Kiki, Bunseki Gijutsu Kenkyukai Hokoku, p.117 - 120, 2003/00
no abstracts in English
