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Journal Articles

In-out asymmetry of low-$$Z$$ impurity deposition on the JT-60 divertor tiles

Masaki, 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:100(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Transmission electron microscopy of redeposition layers on graphite tiles used for open divertor armor of JT-60

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:28.15(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.

Journal Articles

Tritium distribution in the first wall of JT-60U

Masaki, Kei; Sugiyama, Kazuyoshi*; Tanabe, Tetsuo*; Goto, Yoshitaka*; Tobita, Kenji; Miyo, Yasuhiko; Kaminaga, Atsushi; Kodama, Kozo; Arai, Takashi; Miya, Naoyuki

Nippon Genshiryoku Gakkai Wabun Rombunshi, 2(2), p.130 - 139, 2003/06

no abstracts in English

Journal Articles

Tritium distribution in JT-60U W-shaped divertor

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:51 Percentile:4.69(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$$^{2}$$ 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$$^{2}$$) even with the thick deposition layer of $$sim$$60 $$mu$$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.

Journal Articles

Analyses of erosion and re-deposition layers on graphite tiles used in the W-shaped divertor region of JT-60U

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:45 Percentile:5.82

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.

Journal Articles

Tritium profiles on the surface of graphite tiles used in JT-60U

Sugiyama, Kazuyoshi*; Miyasaka, Kazutaka*; Tanabe, Tetsuo*; Masaki, Kei; Goto, Yoshitaka*; Tobita, Kenji; Kodama, Kozo; Miya, Naoyuki

Physica Scripta, T103, p.56 - 58, 2003/00

 Times Cited Count:14 Percentile:35.41(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Wall conditioning and experience of the carbon-based first wall in JT-60U

Masaki, Kei; Yagyu, Junichi; Arai, Takashi; Kaminaga, Atsushi; Kodama, Kozo; Miya, Naoyuki; Ando, Toshiro; Hiratsuka, Hajime; Saido, Masahiro

Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.386 - 395, 2002/09

 Times Cited Count:8 Percentile:49.24(Nuclear Science & Technology)

The wall conditioning of JT-60U consists of the 300$$^{circ}$$C baking, He-TDC, He-GDC, tokamak discharge cleaning and boronization. Using these methods, total pressure of the vacuum vessel reached finally 10$$^{-6}$$ $$sim$$ 10$$^{-5}$$ Pa. The oxygen impurity was decreased to $$sim$$0.5%. The experience with the carbon-based first wall showed that taper shaping is effective to reduce the local heat concentration to the tile edges. The observed poloidal asymmetric deposition of carbon on the divertor region implies that the carbon impurity produced in the outer divertor contributes to the deposition on the inner divertor. In 1992 and 1993, the B$$_{4}$$C converted CFC tiles were installed in the outer divertor to reduce chemical sputtering of CFC tiles and oxygen impurity. The reduction was successfully demonstrated with the B$$_{4}$$C converted CFC tiles. In order to understand the tritium behavior in JT-60U, tritium in the first wall and the exhaust gas were measured. The estimated tritium inventory in the first wall was $$sim$$50% of the generated tritium.

Journal Articles

Development and operational experiences of the JT-60U tokamak and power supplies

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:81.97(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.

Journal Articles

Surface distribution of tritium on graphite tiles of divertor area in JT-60U

Tanabe, Tetsuo*; Miyasaka, Kazutaka*; Sugiyama, Kazuyoshi*; Masaki, Kei; Kodama, Kozo; Miya, Naoyuki

Fusion Engineering and Design, 41(3), p.877 - 881, 2002/05

no abstracts in English

Journal Articles

JT-60U W-shaped divertor with in-out divertor pumping slots

Masaki, Kei; Morimoto, Masaaki*; Sakasai, Akira; Takenaga, Hidenobu; Sasajima, Tadayuki; Kodama, Kozo; Miyachi, Kengo; Hosogane, Nobuyuki

Proceedings of the 18th IEEE/NPSS Symposium on Fusion Engineering (SOFE '99), p.123 - 126, 1999/00

no abstracts in English

Journal Articles

Quality evaluation of graphites and carbon/carbon composites during production of JT-60U plasma facing materials

Ando, Toshiro; Kodama, Kozo; Yamamoto, Masahiro; Arai, Takashi; Kaminaga, Atsushi; Horiike, Hiroshi; Eto, Motokuni; Fukaya, Kiyoshi; Kiuchi, Teruo*; Teruyama, Kazuhiro*; et al.

Journal of Nuclear Materials, 191-194(2), p.1423 - 1427, 1992/09

no abstracts in English

11 (Records 1-11 displayed on this page)
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