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Journal Articles

Role of low order rational $$q$$-values in the ITB events in JT-60U reverse shear plasmas

Neudatchin, S. V.*; Takizuka, Tomonori; Hayashi, Nobuhiko; Isayama, Akihiko; Shirai, Hiroshi; Fujita, Takaaki; Kamada, Yutaka; Koide, Yoshihiko; Suzuki, Takahiro

Nuclear Fusion, 44(9), p.945 - 953, 2004/09

The formation of internal transport barriers (ITBs) near q=3 surfaces in normal shear (NrS) discharges of JT-60U is known. In reverse shear (RS) JT-60U plasmas, the role of q minimum (qmin) equal to 3.5,3,2.5,2 was not obvious for ITB formation. ITB-events (non-local confinement bifurcations inside and around ITB) are found in various NrS and RS plasmas. Under sufficient heating power, ITB-events are seen at rational and not rational values of qmin. The space-time evolution of Te and Ti is similar, suggesting the same mechanism of Te and Ti transport. The temporal formation of strong ITB under passing of qmin=3 (after periodical improvements and degradations via ITB-events) in RS mode is presented. Under smaller power, ITB-events are observed only at rational values of qmin. In a weak RS shot, abrupt rise of Te is seen at qmin=3.5, while more cases of Ti rise are observed. The difference of Te and Ti evolutions seen regularly under the low power, suggests decoupling of Te and Ti transport.

Journal Articles

Properties of internal transport barrier formation in JT-60U

Sakamoto, Yoshiteru; Suzuki, Takahiro; Ide, Shunsuke; Koide, Yoshihiko; Takenaga, Hidenobu; Kamada, Yutaka; Fujita, Takaaki; Fukuda, Takeshi; Takizuka, Tomonori; Shirai, Hiroshi; et al.

Nuclear Fusion, 44(8), p.876 - 882, 2004/08

 Times Cited Count:26 Percentile:32.65(Physics, Fluids & Plasmas)

Response of the ion thermal diffusivity to the radial electric field Er shear has been investigated in JT-60U and the following results were found. (1) In the case of positive magnetic shear (PS) plasma, the ion thermal diffusivity in the core region shows L mode state, weak internal transport barrier (ITB), and strong ITB depending upon the heating power. In the case of reversed magnetic shear (RS) plasma, however, no power degradation of the ion thermal diffusivity is observed. (2) In the case of weak ITB, the ion thermal diffusivity decreases gradually with increasing the Er shear for both PS and RS plasmas. There exists a threshold of an effective Er shear to change its state from weak to strong ITBs. (3) The threshold of the effective Er shear in the case of RS plasma is small compared with that in the case of PS plasma.

Journal Articles

Heating and current drive by electron cyclotron waves in JT-60U

Suzuki, Takahiro; Ide, Shunsuke; Hamamatsu, Kiyotaka; Isayama, Akihiko; Fujita, Takaaki; Petty, C. C.*; Ikeda, Yoshitaka; Kajiwara, Ken*; Naito, Osamu; Seki, Masami; et al.

Nuclear Fusion, 44(7), p.699 - 708, 2004/05

 Times Cited Count:28 Percentile:30.29(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Fast dynamics of type I ELMs and transport of the ELM pulse in JT-60U

Oyama, Naoyuki; Asakura, Nobuyuki; Chankin, A. V.; Oikawa, Toshihiro; Sugihara, Masayoshi; Takenaga, Hidenobu; Itami, Kiyoshi; Miura, Yukitoshi; Kamada, Yutaka; Shinohara, Koji; et al.

Nuclear Fusion, 44(5), p.582 - 592, 2004/05

 Times Cited Count:45 Percentile:17.16(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Driving mechanism of sol plasma flow and effects on the divertor performance in JT-60U

Asakura, Nobuyuki; Takenaga, Hidenobu; Sakurai, Shinji; Porter, G. D.*; Rognlien, T. D.*; Rensink, M. E.*; Shimizu, Katsuhiro; Higashijima, Satoru; Kubo, Hirotaka

Nuclear Fusion, 44(4), p.503 - 512, 2004/04

 Times Cited Count:66 Percentile:9.75(Physics, Fluids & Plasmas)

The measurements of the SOL flow and plasma profiles both at the high-field-side (HFS) and low-field-side (LFS), for the first time, found out the SOL flow pattern and its driving mechanism. "Flow reversal" was found near the HFS and LFS separatrix of the main plasma for the ion ▽B drift direction towards the divertor. Radial profiles of the SOL flow were similar to those calculated numerically using the UEDGE code with the plasma drifts included although Mach numbers in measurements were faster than those obtained numerically. Particle fluxes towards the HFS and LFS divertors produced by the parallel SOL flow and Er$$times$$B drift flow were evaluated. The particle flux for the case of intense gas puff and divertor pump (puff and pump) was investigated, and it was found that both flow velocity and collisionality were enhanced, in particular, at HFS SOL. Drift flux in the private flux region was also evaluated, and important physics issues for the divertor design and operation, such as in-out asymmetries of the heat and particle fluxes, and control of impurity ions were investigated.

Journal Articles

Performance of ITER as a burning plasma experiment

Shimada, Michiya; Mukhovatov, V.*; Federici, G.*; Gribov, Y.*; Kukushkin, A.*; Murakami, Yoshiki*; Polevoi, A. R.*; Pustovitov, V. D.*; Sengoku, Seio; Sugihara, Masayoshi

Nuclear Fusion, 44(2), p.350 - 356, 2004/02

Recent performance analysis has improved confidence in achieving Q $$>$$ 10 in inductive operation in ITER. Performance analysis based on empirical scaling shows the feasibility of achieving Q $$>$$ 10 in inductive operation with a sufficient margin. Theory-based core modeling indicates the need of high pedestal temperature (2-4 keV) to achieve Q $$>$$ 10, which is in the range of projection with pedestal scaling. The heat load of type-I ELM could be made tolerable by high density operation and further tilting the target plate (if necessary). Pellet injection from High-Field Side would be useful in enhancing Q and reducing ELM heat load. Steady state operation scenarios have been developed with modest requirement on confinement improvement and beta (HH98(y,2) $$>$$ 1.3 and betaN $$>$$ 2.6). Stabilisation of RWM, required in such regimes, is feasible with the present saddle coils and power supplies with double-wall structure taken into account.

Journal Articles

Advanced fusion technologies developed for JT-60 superconducting Tokamak

Sakasai, Akira; Ishida, Shinichi; Matsukawa, Makoto; Akino, Noboru; Ando, Toshinari*; Arai, Takashi; Ezato, Koichiro; Hamada, Kazuya; Ichige, Hisashi; Isono, Takaaki; et al.

Nuclear Fusion, 44(2), p.329 - 334, 2004/02

no abstracts in English

Journal Articles

Studies of the influence of electron heating on ITB subject to advanced tokamak operation in JT-60U

Ide, Shunsuke; Suzuki, Takahiro; Sakamoto, Yoshiteru; Takenaga, Hidenobu; Fujita, Takaaki; Oyama, Naoyuki; Isayama, Akihiko; Koide, Yoshihiko; Kamada, Yutaka; JT-60 Team

Nuclear Fusion, 44(1), p.87 - 92, 2004/01

 Times Cited Count:18 Percentile:44.86(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Overview of JT-60U results leading to high integrated performance in reactor-relevant regimes

Fujita, Takaaki; JT-60 Team

Nuclear Fusion, 43(12), p.1527 - 1539, 2003/12

 Times Cited Count:29 Percentile:31.18(Physics, Fluids & Plasmas)

Recent JT-60U results toward high integrated performance are reported with emphasis on the projection to the reactor-relevant regime. N-NB and EC power increased up to 6.2 MW and 3 MW, respectively. A high betap H-mode plasma with full non-inductive current drive has been obtained at 1.8 MA and the fusion triple product reached 3.1E20m$$^{-3}$$keVs. NTM suppression with EC was accomplished using a real-time feedback control system and improvement in betaN was obtained. A stable existence of current hole was observed. High DT-equivalent fusion gain of 0.8 was maintained for 0.55 s in a plasma with a current hole. The current profile control in high bootstrap current reversed shear plasmas was demonstrated using N-NB and LH. A new operation scenario has been established in which a plasma with high bootstrap current fraction and ITBs is produced without the use of OH coil. A new type of AE mode has been proposed and found to explain the observed frequency chirp quite well. Ar exhaust with EC heating was obtained in a high betap mode plasma.

Journal Articles

Relationship between particle and heat transport in JT-60U plasmas with internal transport barrier

Takenaga, Hidenobu; Higashijima, Satoru; Oyama, Naoyuki; Bruskin, L. G.; Koide, Yoshihiko; Ide, Shunsuke; Shirai, Hiroshi; Sakamoto, Yoshiteru; Suzuki, Takahiro; Hill, K. W.*; et al.

Nuclear Fusion, 43(10), p.1235 - 1245, 2003/10

 Times Cited Count:62 Percentile:11.61(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Achievement of high fusion triple product, steady-state sustainment and real-time NTM stabilization in high-$$beta_p$$ ELMy H-mode discharges in JT-60U

Isayama, Akihiko; Kamada, Yutaka; Hayashi, Nobuhiko; Suzuki, Takahiro; Oikawa, Toshihiro; Fujita, Takaaki; Fukuda, Takeshi; Ide, Shunsuke; Takenaga, Hidenobu; Ushigusa, Kenkichi; et al.

Nuclear Fusion, 43(10), p.1272 - 1278, 2003/10

 Times Cited Count:124 Percentile:3.4(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

High performance tokamak experiments with a ferritic steel wall on JFT-2M

Tsuzuki, Kazuhiro; Kimura, Haruyuki; Kawashima, Hisato; Sato, Masayasu; Kamiya, Kensaku; Shinohara, Koji; Ogawa, Hiroaki; Hoshino, Katsumichi; Bakhtiari, M.; Kasai, Satoshi; et al.

Nuclear Fusion, 43(10), p.1288 - 1293, 2003/10

 Times Cited Count:38 Percentile:24.34(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Observation of high recycling steady H-mode edge and compatibility with improved core confinement mode on JFT-2M

Kamiya, Kensaku; Kimura, Haruyuki; Ogawa, Hiroaki; Kawashima, Hisato; Tsuzuki, Kazuhiro; Sato, Masayasu; Miura, Yukitoshi; JFT-2M Group

Nuclear Fusion, 43(10), p.1214 - 1219, 2003/10

no abstracts in English

Journal Articles

Development of advanced blanket materials for a solid breeder blanket of a fusion reactor

Kawamura, Hiroshi; Ishitsuka, Etsuo; Tsuchiya, Kunihiko; Nakamichi, Masaru; Uchida, Munenori*; Yamada, Hirokazu*; Nakamura, Kazuyuki; Ito, Haruhiko; Nakazawa, Tetsuya; Takahashi, Heishichiro*; et al.

Nuclear Fusion, 43(8), p.675 - 680, 2003/08

 Times Cited Count:24 Percentile:37.86(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Improvement of beam performance in the negative-ion based NBI system for JT-60U

Umeda, Naotaka; Grisham, L. R.*; Yamamoto, Takumi; Kuriyama, Masaaki; Kawai, Mikito; Oga, Tokumichi; Mogaki, Kazuhiko; Akino, Noboru; Yamazaki, Haruyuki*; Usui, Katsutomi; et al.

Nuclear Fusion, 43(7), p.522 - 526, 2003/07

 Times Cited Count:37 Percentile:24.34(Physics, Fluids & Plasmas)

The Negative-ion based Neutral Beam Injection System (N-NBI) for JT-60U has been operating for plasma heating and non-inductive current drive since 1996. The target is inject of neutral beam into plasma with beam energy 500 keV, injection power 10 MW, for 10 seconds. Until now pulse duration time was restricted up to 5.3 seconds because of larger heat load of port limiter. Recently from the measurement of beam profile at 3.5m downstream from the ion source, it was found that the outermost beamlets in each segment were deflected outward. It was caused by non-uniform electric field by grooves. By improving this, outermost beamlet deflection angle was decreased from 14 mrad to 4 mrad. In this result, 10 seconds injection, which is target parameter, has achieved at 355 keV, 2.6MW, while pulse length was restricted up to 5.3 seconds by larger heat load of port limiter.

Journal Articles

Effects of complex magnetic ripple on fast ions in JFT-2M ferritic insert experiments

Shinohara, Koji; Kawashima, Hisato; Tsuzuki, Kazuhiro; Urata, Kazuhiro*; Sato, Masayasu; Ogawa, Hiroaki; Kamiya, Kensaku; Sasao, Hajime; Kimura, Haruyuki; Kasai, Satoshi; et al.

Nuclear Fusion, 43(7), p.586 - 593, 2003/07

 Times Cited Count:45 Percentile:18.86(Physics, Fluids & Plasmas)

In JFT-2M, the ferritic steel was installed inside the vacuum vessel as the third step of tne Advanced Material Tokamak Experiment (AMTEX) programme. The magnetic field structure has become the complex ripple strucuture such as non-periodic ripple structure in the toroidal direction and high Fourier-number ripple because of the existence of the port and the limitation of the periodic installation. Under such a complex ripple structure, we have performed the experiment to understand its effect on fast ions. To actively change the ripple structure, we have installed the additional ferritic steel plates (FPs). We also have compared the experiment result with the newly updated OFMC code which does not need the toroidal 16-folded symmetry. The experiment results were almost consistent with the OFMC calcution with the complex magnetic field and the complex first wall.

Journal Articles

Neutronics experiments for DEMO blanket at JAERI/FNS

Sato, Satoshi; Ochiai, Kentaro; Hori, Junichi; Verzilov, Y. M.; Klix, A.; Wada, Masayuki*; Terada, Yasuaki*; Yamauchi, Michinori*; Morimoto, Yuichi*; Nishitani, Takeo

Nuclear Fusion, 43(7), p.527 - 530, 2003/07

 Times Cited Count:13 Percentile:57.35(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Objectives and design of the JT-60 superconducting tokamak

Ishida, Shinichi; Abe, Katsunori*; Ando, Akira*; Chujo, T.*; Fujii, Tsuneyuki; Fujita, Takaaki; Goto, Seiichi*; Hanada, Kazuaki*; Hatayama, Akiyoshi*; Hino, Tomoaki*; et al.

Nuclear Fusion, 43(7), p.606 - 613, 2003/07

no abstracts in English

Journal Articles

Long timescale plasma dynamics and explosive growth driven by the double tearing mode in reversed shear plasmas

Ishii, Yasutomo; Azumi, Masafumi; Kishimoto, Yasuaki; Leboeuf, J. N.*

Nuclear Fusion, 43(7), p.539 - 546, 2003/07

no abstracts in English

Journal Articles

Geometrical improvements of rotational stabilization of high-$$n$$ ballooning modes in tokamaks

Furukawa, Masaru; Tokuda, Shinji; Wakatani, Masahiro*

Nuclear Fusion, 43(6), p.425 - 429, 2003/06

We have found numerically that damping phases appear in the time evolution of the perturbation energy of high-$$n$$ ballooning modes in the presence of toroidal shear flows. The damping dominates exponential growth which occurs in the bad curvature region, resulting in stabilization of ballooning modes. D-shaping of plasma cross-section, reduction of aspect ratio, and arrangement of X-point at inner side of the torus enhance the stabilization effect of the toroidal flow through this mechanism.

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