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Journal Articles

Present status of manufacturing and R&Ds for the JT-60SA tokamak

Higashijima, Satoru; Kamada, Yutaka; Barabaschi, P.*; Shirai, Hiroshi; JT-60SA Team

Fusion Science and Technology, 68(2), p.259 - 266, 2015/09

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

Journal Articles

The Emission rates of CH, CD and C$$_{2}$$ spectral bands and a re-evaluation of the chemical sputtering yield of the JT-60U carbon divertor plates

Nakano, Tomohide; Higashijima, Satoru; Kubo, Hirotaka; Asakura, Nobuyuki; Fukumoto, Masakatsu

Nuclear Fusion, 54(4), p.043004_1 - 043004_10, 2014/03

 Times Cited Count:1 Percentile:92.74(Physics, Fluids & Plasmas)

We have determined the CH photon emission rate defined as the number of photons over dissociation and/or ionization event of $$mbox{CH}_4$$, from the ratio of the measured emission intensity of CH spectral band to the $$mbox{CH}_4$$ injection rate into the divertor plasma of JT-60U. Similar photon emission rates of CD for $$mbox{CD}_4$$, CH and $$mbox{C}_2$$ for $$mbox{C}_2mbox{H}_4$$ and $$mbox{C}_2mbox{H}_6$$ have also been determined. Interestingly, during the $$mbox{CH}_4$$ and the $$mbox{CD}_4$$ injection, the $$mbox{C}_2$$ spectral band intensity increases, suggesting that injected $$mbox{CH}_4$$ reacts with the carbon divertor plates to form heavier hydrocarbons. From the determined emission rates, previously published chemical sputtering yields, have been reevaluated. The reevaluated total chemical sputtering yield becomes lower ($$sim6%$$) compared to the original ($$sim8%$$) and the dependence on the incident ion flux and energy becomes weaker.

Journal Articles

Heat treatment for CuCrZr cooling tubes for JT-60SA monoblock-type divertor targets

Higashijima, Satoru; Sakurai, Shinji; Sakasai, Akira

Journal of Nuclear Materials, 417(1-3), p.912 - 915, 2011/10

 Times Cited Count:5 Percentile:55.47(Materials Science, Multidisciplinary)

JT-60SA divertor has to receive the maximum heat flux of $$sim$$15 MW/m$$^{2}$$ for 100 s, and JAEA have developed the monoblock-type CFC divertor target for JT-60SA. For boosting the production yield of the target, CFC cracking due to thermal expansion and contraction of the CuCrZr cooling tube should be suppressed. CuCrZr characteristics strongly depend on the heat treatment, and the target is heat-treated on the manufacturing process of brazing, solution treatment, and annealing. CuCrZr test specimens were heat-treated with the targets, and the strength and the hardness of the specimens were almost the same in the case of the quenching rates of $$sim$$0.65 $$^{circ}$$C/s and $$sim$$1.5 $$^{circ}$$C/s around 800 $$^{circ}$$C. It is clarified that the slower quenching rate is acceptable, and the half of the mock-ups at least removed high heat flux of 15 MW/m$$^{2}$$ as required without the CFC cracking.

Journal Articles

Design of lower divertor for JT-60SA

Sakurai, Shinji; Higashijima, Satoru; Hayashi, Takao; Shibama, Yusuke; Masuo, Hiroshige*; Ozaki, Hidetsugu; Sakasai, Akira; Shibanuma, Kiyoshi

Fusion Engineering and Design, 85(10-12), p.2187 - 2191, 2010/08

 Times Cited Count:8 Percentile:49.53(Nuclear Science & Technology)

JT-60SA tokamak project has just started construction phase under both the Japanese domestic program and the Japan-EU international program "ITER Broader Approach". All of plasma facing components (PFC) shall be actively cooled due to high power long pulse plasma heating. Lower single null closed divertor with vertical target (VT) will be installed at the start of experiment phase. Each divertor module covers a 10-degree sector in toroidal direction. PFCs such as VTs, baffles and dome shall be assembled on a divertor cassette, which provides integrated coolant pipe connection to coolant headers in the VV. Static structural analysis for dead weight, coolant pressure and EM loads shows that displacement and stress of the divertor module are generally small but a part of support structure of PFC requires improvement.

Journal Articles

Mock-up test results of monoblock-type CFC divertor armor for JT-60SA

Higashijima, Satoru; Sakurai, Shinji; Suzuki, Satoshi; Yokoyama, Kenji; Kashiwa, Yoshitoshi; Masaki, Kei; Shibama, Yusuke; Takechi, Manabu; Shibanuma, Kiyoshi; Sakasai, Akira; et al.

Fusion Engineering and Design, 84(2-6), p.949 - 952, 2009/06

 Times Cited Count:8 Percentile:45.57(Nuclear Science & Technology)

An upgrading device of JT-60 tokamak with fully superconducting coils (JT-60SA) is constructed under both the Japanese domestic program and the international program "Broader Approach". The maximum heat flux to JT-60SA divertor is estimated to 15 MW/m$$^{2}$$ for 100 s, and a monoblock-type CFC divertor armor is promising. The JT-60SA armor consists of CFC monoblocks, a cooling CuCrZr screw-tube, and a thin OFHC-Cu buffer layer, and the brazed joints are essential for the armor. Metalization inside CFC monoblock is applied for further improvement, and we confirmed again that the mock-up has heat removal capability in excess of ITER requirement. For optimization of the fabrication method and understanding of the production yield, the mock-ups corresponding to quantity produced in one furnace is also produced, and the half of the mock-ups could remove 15 MW/m$$^{2}$$ as required. This summarizes the recent progress of design and mock-up test results for JT-60SA divertor armor.

Journal Articles

Design, R&D and assessment of performance of the JT-60SA upper divertor

Sakurai, Shinji; Kawashima, Hisato; Higashijima, Satoru; Shimizu, Katsuhiro; Masaki, Kei; Asakura, Nobuyuki; Shibama, Yusuke; Sakasai, Akira

Journal of Nuclear Materials, 390-391, p.891 - 894, 2009/06

 Times Cited Count:1 Percentile:88.68(Materials Science, Multidisciplinary)

The entire plasma facing components should be water-cooled in JT-60SA. A cassette module of divertor is introduced for remote maintenance. The divertor targets are mounted on the cassette. A brazed carbon fiber composite target is promising candidate for the divertor target. The latest results of mock-ups test clarified that thermal fatigue life cycles are more than 1000 cycles of 15 MW/m$$^{2}$$$$times$$10 sec. The divertor is designed to control divertor detachment for heat load reduction. The vertical targets and a "V-shaped corner" like as that in ITER are adopted to enhance detachment. Divertor heat load and pumping efficiency has been evaluated, using 2D plasma fluid (SOLDOR) and neutral Monte-Carlo (NEUT2D) code. The plasma detachment occurs near the outer-strike point within the "V-shaped corner", which results in low peak heat flux density 5.8 MW/m$$^{2}$$ for the case with additional gas puff of 5$$times$$10$$^{21}$$/s compared to 11.4 MW/m$$^{2}$$ for the case without "V-shaped corner".

Journal Articles

Radiation process of carbon ions in JT-60U detached divertor plasmas

Nakano, Tomohide; Kubo, Hirotaka; Asakura, Nobuyuki; Shimizu, Katsuhiro; Kawashima, Hisato; Higashijima, Satoru

Journal of Nuclear Materials, 390-391, p.255 - 258, 2009/06

 Times Cited Count:17 Percentile:23.73(Materials Science, Multidisciplinary)

Therefore it is concluded that the dominant radiator, C$$^{3+}$$, is produced by ionization of C$$^{2+}$$ and recombination of C$$^{4+}$$ at similar rates around the X-point in the detached plasma, and that C$$^{2+}$$ is the second biggest radiator. Further the transport loss of C$$^{3+}$$ will be investigated by an impurity transport code (IMPMC), in addition to comparison of the radiation power and atomic processes.

Journal Articles

Status of JT-60SA tokamak under the EU-JA broader approach agreement

Matsukawa, Makoto; Kikuchi, Mitsuru; Fujii, Tsuneyuki; Fujita, Takaaki; Hayashi, Takao; Higashijima, Satoru; Hosogane, Nobuyuki; Ikeda, Yoshitaka; Ide, Shunsuke; Ishida, Shinichi; et al.

Fusion Engineering and Design, 83(7-9), p.795 - 803, 2008/12

 Times Cited Count:15 Percentile:26.15(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Impurity accumulation in the main plasma and radiation processes in the divetor plasma of JT-60U

Nakano, Tomohide; Kubo, Hirotaka; Asakura, Nobuyuki; Shimizu, Katsuhiro; Higashijima, Satoru

Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10

It has been found that tungsten accumulation becomes more significant with increasing plasma rotation velocity against the plasma current direction, where negative radial electric field is formed. In a high density plasma at 62% of the Greenwald density, the tungsten accumulation levels decreased significantly, suggesting a shielding effect of the peripheral plasma. It has been found that $$mbox{C}^{3+}$$ is produced by the volume recombination of $$mbox{C}^{4+}$$ and the ionization of $$mbox{C}^{2+}$$ comparably. In contrast, the volume recombination of $$mbox{C}^{3+}$$ is not detected, and the ionization flux of $$mbox{C}^{3+}$$ is less than 1% of the $$mbox{C}^{3+}$$ generation flux. Thus, this result suggests that another loss mechanism of $$mbox{C}^{3+}$$ such as transport loss from the ${sf X}$-point is significant.

Journal Articles

Volume recombination of C$$^{4+}$$ in detached divertor plasmas of JT-60U

Nakano, Tomohide; Kubo, Hirotaka; Asakura, Nobuyuki; Shimizu, Katsuhiro; Konoshima, Shigeru; Fujimoto, Kayoko; Kawashima, Hisato; Higashijima, Satoru

Nuclear Fusion, 47(11), p.1458 - 1467, 2007/11

 Times Cited Count:19 Percentile:39.53(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Study of highly ionized Xe spectra with 3s-3p and 3p-3d transitions in JT-60U reversed shear plasmas

Kubo, Hirotaka; Sasaki, Akira; Moribayashi, Kengo; Higashijima, Satoru; Takenaga, Hidenobu; Shimizu, Katsuhiro; Nakano, Tomohide; Whiteford, A.*; Sugie, Tatsuo

Journal of Nuclear Materials, 363-365, p.1441 - 1445, 2007/06

 Times Cited Count:6 Percentile:53.84(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Radiation processes of impurities and hydrogen in detached divertor plasmas of JT-60U

Nakano, Tomohide; Kubo, Hirotaka; Asakura, Nobuyuki; Shimizu, Katsuhiro; Konoshima, Shigeru; Fujimoto, Kayoko; Kawashima, Hisato; Higashijima, Satoru

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03

Volume recombination of C$$^{4+}$$ and $$e^{-}$$ into C$$^{3+}$$ is observed for the first time in detached plasmas with MARFE. It is found that the recombination flux of C$$^{4+}$$ to C$$^{3+}$$ is comparable to the ionization flux of C$$^{3+}$$ to C$$^{4+}$$, and that the recombination zone is above an X-point and beneath the ionization zone. This result suggests that this volume recombination predominantly produces C$$^{3+}$$ ions, which contribute 60-80 % to the total radiation power in the divertor plasma.

Journal Articles

Impact of wall saturation on particle control in long and high-power-heated discharges in JT-60U

Nakano, Tomohide; Asakura, Nobuyuki; Takenaga, Hidenobu; Kubo, Hirotaka; Miura, Yukitoshi; Shimizu, Katsuhiro; Konoshima, Shigeru; Masaki, Kei; Higashijima, Satoru; JT-60 Team

Nuclear Fusion, 46(5), p.626 - 634, 2006/05

 Times Cited Count:18 Percentile:43.48(Physics, Fluids & Plasmas)

In order to understand plasma-wall interactions in a long time scale, the discharge pulse length has been extended from 15 s to 65 s, with the NB-heating duration extended to 30 s. Nearly-saturation of the divertor plates was observed in the latter half of long pulse ELMy H-mode discharges. Particle sink into the divertor plates gradually decreased, and subsequently, wall-pumping efficiency became zero. This wall saturation resulted in a rise of the main plasma density without any auxiliary particle supply besides NB with divertor-pumping. Even when the total injected energy reached up to $$sim$$ 350 MJ in a discharge, neither sudden increase of carbon generation such as carbon bloom nor increase of the dilution of the main plasma was observed.

Journal Articles

Characterization of JT-60U exhaust gas during experimental operation

Isobe, Kanetsugu; Nakamura, Hirofumi; Kaminaga, Atsushi; Tsuzuki, Kazuhiro; Higashijima, Satoru; Nishi, Masataka; Kobayashi, Yasunori*; Konishi, Satoshi*

Fusion Engineering and Design, 81(1-7), p.827 - 832, 2006/02

 Times Cited Count:10 Percentile:38.99(Nuclear Science & Technology)

Exhaust gas from JT-60U during experimental operation has been measured with Gas Chromatography (GC), and the gas exhaust characteristic from JT-60U on plasma discharge conditions has been investigated during the JT-60U experimental campaign in 2003-2004. During experimental operation of JT-60U, hydrogen isotope concentration strongly depended on the type of discharges such as high performance, long pulse and so on. On the other hand, impurity species, such as helium, hydrocarbon and carbon oxide, were detected during plasma discharges occasionally. During the experimental operation, plasma disruption remarkably tended to produce high concentration impurities. Glow discharge and Taylor discharge for wall conditioning also produced impurities. In the case of normal plasma, impurity was detected and high performance plasma, such as high $$beta$$ plasma, tended to produce high concentration impurities. This result indicated that impurities concentration might be higher in the case of normal plasma in ITER, because of its high performance.

Journal Articles

Hydrogen isotopes removal from the vacuum vessel using discharges

Nakamura, Hirofumi; Higashijima, Satoru

Shinku, 49(2), p.62 - 68, 2006/02

no abstracts in English

Journal Articles

Compatibility of advanced tokamak plasma with high density and high radiation loss operation in JT-60U

Takenaga, Hidenobu; Asakura, Nobuyuki; Kubo, Hirotaka; Higashijima, Satoru; Konoshima, Shigeru; Nakano, Tomohide; Oyama, Naoyuki; Porter, G. D.*; Rognlien, T. D.*; Rensink, M. E.*; et al.

Nuclear Fusion, 45(12), p.1618 - 1627, 2005/12

 Times Cited Count:18 Percentile:44.87(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Relation between the oxygen contents in the neutral beam and in the core plasma in JT-60U

Nakano, Tomohide; Koide, Yoshihiko; Honda, Atsushi; Umeda, Naotaka; Akino, Noboru; Higashijima, Satoru; Takenaga, Hidenobu; Kubo, Hirotaka

Purazuma, Kaku Yugo Gakkai-Shi, 81(9), p.708 - 716, 2005/09

no abstracts in English

Journal Articles

Tritium release behavior from JT-60U vacuum vessel during air exposure phase and wall conditioning phase

Isobe, Kanetsugu; Nakamura, Hirofumi; Kaminaga, Atsushi; Higashijima, Satoru; Nishi, Masataka; Konishi, Satoshi*; Nishikawa, Masabumi*; Tanabe, Tetsuo*

Fusion Science and Technology, 48(1), p.302 - 305, 2005/07

 Times Cited Count:3 Percentile:73.58(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Spectroscopic study of hydrogen particle behavior in attached and detached divertor plasmas of JT-60U

Kubo, Hirotaka; Takenaga, Hidenobu; Sawada, Keiji*; Nakano, Tomohide; Kobayashi, Shinji*; Higashijima, Satoru; Asakura, Nobuyuki; Shimizu, Katsuhiro

Journal of Nuclear Materials, 337-339, p.161 - 165, 2005/03

 Times Cited Count:15 Percentile:26.79(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Study of plasma wall interactions in the long-pulse NB-heated discharges of JT-60U towards steady-state operation

Takenaga, Hidenobu; Asakura, Nobuyuki; Higashijima, Satoru; Nakano, Tomohide; Kubo, Hirotaka; Konoshima, Shigeru; Oyama, Naoyuki; Isayama, Akihiko; Ide, Shunsuke; Fujita, Takaaki; et al.

Journal of Nuclear Materials, 337-339, p.802 - 807, 2005/03

 Times Cited Count:14 Percentile:28.66(Materials Science, Multidisciplinary)

no abstracts in English

104 (Records 1-20 displayed on this page)