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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:21 Percentile:56.42(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

Design study of national centralized tokamak facility for the demonstration of steady state high-$$beta$$ plasma operation

Tamai, 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:44.82(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.

Journal Articles

Actively-cooled plasma electrode for long pulse operations in a cesium-seeded negative ion source

Fujiwara, Yukio; Watanabe, Kazuhiro; Okumura, Yoshikazu; Trainham, R.*; Jacquot, C.*

Review of Scientific Instruments, 76(1), p.013501_1 - 013501_5, 2005/01

 Times Cited Count:0 Percentile:0.00(Instruments & Instrumentation)

A new actively-cooled plasma electrode has been developed for long pulse operation in a cesium-seeded negative ion source. To keep the electrode temperature at about 300 $$^{circ}$$C, which is optimum range of temperature to enhance cesium effects, the electrode cooling structure has been designed using three-dimensional numerical simulation assuming that the heat flux from the source plasma was 15 W/cm$$^{2}$$. Water cooling tubes were brazed to the plasma electrode substrate with spacers made of stainless steel which acts as a thermal resistance. The fabricated plasma electrode has been tested in a cesium-seeded volume negative ion source called Kamaboko source. The temperature of the electrode reached 280 $$^{circ}$$C for the arc power of 41 kW, which is operating condition required for producing D- beams with current densities exceeding 20 mA/cm$$^{2}$$. It was demonstrated that the actively-cooled plasma electrode is applicable to long pulse operations, meeting the temperature requirement for optimizing the surface-production process of negative ions in the cesium seeded ion source.

Journal Articles

Radiation-induced thermoelectric sensitivity in the mineral-insulated cable of magnetic diagnostic coils for ITER

Nishitani, Takeo; Vayakis, G.*; Yamauchi, Michinori*; Sugie, Tatsuo; Kondoh, Takashi; Shikama, Tatsuo*; Ishitsuka, Etsuo; Kawashima, Hisato

Journal of Nuclear Materials, 329-333(Part2), p.1461 - 1465, 2004/08

 Times Cited Count:16 Percentile:69.08(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Advanced control scenario of high-performance steady-state operation for JT-60 superconducting tokamak

Tamai, Hiroshi; Kurita, Genichi; Matsukawa, Makoto; Urata, Kazuhiro*; Sakurai, Shinji; Tsuchiya, Katsuhiko; Morioka, Atsuhiko; Miura, Yushi; Kizu, Kaname; Kamada, Yutaka; et al.

Plasma Science and Technology, 6(3), p.2281 - 2285, 2004/06

 Times Cited Count:0 Percentile:0.00(Physics, Fluids & Plasmas)

High performance steady-state operation for JT-60SC are evaluated by the TOPICS analysis. $$beta$$$$_N$$$$sim$$5 and bootstrap current fraction $$sim$$86% is kept steady at I$$_p$$=1.5 MA, B$$_t$$=2 T by neutral beam power of 11 MW. The ERATO-J analysis shows that the external-kink mode with multiple toroidal mode numbers of n=1 and n=2 is stable at $$beta$$$$_N$$ $$leq$$5.5 at the average ratio of conducting wall radius to plasma minor radius of about 1.2 with the wall stabilisation effect. Resistive wall modes, induced by a close location of the wall to plasma, is expected to be suppressed by the active feedback stabilisation with a set of non-axisymmetric field coils behind the stabilising plates. Further optimisation for the high-$$beta$$$$_N$$ accessibility by the plasma shaping is performed with the TOSCA analysis. The plasma shaping factor defined as S=(I$$_p$$/aB$$_t$$)q$$_9$$$$_5$$ and strongly correlated to the plasma elongation and triangularity, is scanned from $$sim$$4 to $$sim$$6, which extends the availability of current and pressure profile control for the high performance plasma operation.

Journal Articles

Neural-net disruption predictor in JT-60U

Yoshino, Ryuji

Nuclear Fusion, 43(12), p.1771 - 1786, 2003/12

 Times Cited Count:57 Percentile:83.42(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Research activities on Tokamaks in Japan; JT-60U, JFT-2M and TRIAM-1M

Ninomiya, Hiromasa; Kitsunezaki, Akio; Shimizu, Masatsugu; Kuriyama, Masaaki; JT-60 Team; Kimura, Haruyuki; Kawashima, Hisato; Tsuzuki, Kazuhiro; Sato, Masayasu; Isei, Nobuaki; et al.

Fusion Science and Technology, 42(1), p.7 - 31, 2002/07

 Times Cited Count:13 Percentile:24.24(Nuclear Science & Technology)

In order to establish scientific basis for the sustainment of highly integrated performance required in the advanced steady-state operation, JT-60U has been optimizing the discharge control scenarios of improved confinement plasmas and expanding the operation regions. Promising results toward the steady-state tokamak were obtained. The detail of such results is reported. JFT-2M has performed advanced and basic research for the development of high performance tokamak plasma as well as the structural material for a fusion reactor. The toroidal ripple reduction with ferritic steel plates outside the vacuum vessel was successfully demonstrated. No adverse effects were observed in the pre-testing on compatibility between ferritic steel plates, covering ~20% of the inside wall of the vacuum vessel, and plasma. The results of TRIAM-1M is also reported.

Journal Articles

Mock-up test of remote controlled dismantling apparatus for large-sized vessels

Kimura, Masanori; Myodo, Masato; Okane, Shogo; Miyajima, Kazutoshi

Proceeding of International Waste Management Symposium 2002 (WM '02) (CD-ROM), 14 Pages, 2002/00

no abstracts in English

Journal Articles

Burn control in tokamak fusion reactors; Disruption and fast plasma shutdown

Yoshino, Ryuji

Purazuma, Kaku Yugo Gakkai-Shi, 75(12), p.1337 - 1374, 1999/12

no abstracts in English

Journal Articles

ITER physics basis, 8; Plasma operation and control

ITER Physics Expert Group on Disruptions, Plasma Control, and MHD; ITER Physics Expert Group on Energetic Particles, Heating and Current Drive; ITER Physics Expert Group on Diagnostics

Nuclear Fusion, 39(12), p.2577 - 2625, 1999/00

no abstracts in English

Journal Articles

Advances in JT-60U facilities and its operation

Kimura, Toyoaki; JT-60 Team

16th IEEE/NPSS Symp. on Fusion Engineering (SOFE '95), 1, p.724 - 729, 1996/00

no abstracts in English

Journal Articles

Machine performance and its effects on experiments in JT-60U

; JT-60 Team

Fusion Technology 1994, 0, p.759 - 762, 1995/00

no abstracts in English

Journal Articles

Status of machine and operation of JT-60U

; JT-60 Team

15th IEEE/NPSS Symp. on Fusion Engineering,Vol. 2, 0, p.826 - 829, 1993/00

no abstracts in English

Journal Articles

Underwater cutting of JPDR reactor pressure vessel and core internals

Tachibana, Mitsuo; Hoshi, Tatsuo; Miki, Ichiro

Proc. of the 1st JSME/ASME Joint Int. Conf. on Nuclear Engineering,Vol. 2, p.81 - 84, 1991/00

no abstracts in English

14 (Records 1-14 displayed on this page)
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