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Journal Articles

Observation of spontaneously excited waves in the ion cyclotron frequency range on JT-60U

Ichimura, Makoto*; Higaki, Hiroyuki*; Kakimoto, Shingo*; Yamaguchi, Yusuke*; Nemoto, Tatsuki*; Katano, Makoto*; Ishikawa, Masao; Moriyama, Shinichi; Suzuki, Takahiro

Nuclear Fusion, 48(3), p.035012_1 - 035012_7, 2008/03

 Times Cited Count:26 Percentile:24.77(Physics, Fluids & Plasmas)

In this paper, experimental observations of spontaneously excited waves in the ion cyclotron range of frequency (ICRF) on JT-60U are described. The fluctuations in ICRF are driven by the presence of non-thermal ion distribution in magnetic confinement plasmas. Two types of magnetic fluctuations are detected: one is due to high energy D ions from neutral beam injections and the other is due to fusion products (FPs) of $$^{3}$$He and T ions. These fluctuations have been reported as ion cyclotron emissions (ICEs) in the burning plasma experiments on large tokamaks. This paper describes the first measurement of the spatial structures of the excited modes in the poloidal and toroidal directions. It is confirmed by using ICRF antennas as magnetic probes that all modes excited spontaneously have magnetic components and couple to the antenna straps. The modes due to D ions have small toroidal wave number $$kappa$$$$_{z}$$ and will behave as electrostatic waves. On the while, the measurement of finite $$kappa$$$$_{z}$$ in the modes due to FP ions supports the excitation of the Alfv$'e$n waves is the possible origin of FP-ICEs. It is also confirmed that the excited modes due to FP ions have different wave structures and are suggested to be in the different branch of the Alfv$'e$n waves, that is, the fast Alfv$'e$n wave and the slow Alfv$'e$n wave. Frequency peaks due to FP ions are sometimes split into doublet shape as observed in JET experiments. The phase differences of both peaks are measured and indicate that two waves are traveling in both toroidal directions. Both beam-driven ICEs and FP-ICEs are observed and those spatial structures are obtained on JT-60U.

Journal Articles

Free-surface fluctuation at high speed lithium flow for IFMIF

Horiike, Hiroshi*; Kondo, Hiroo*; Nakamura, Hiroo; Miyamoto, Seiji*; Yamaoka, Nobuo*; Matsushita, Izuru*; Ida, Mizuho; Ara, Kuniaki; Muroga, Takeo*; Matsui, Hideki*

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

no abstracts in English

Journal Articles

ITER limiters moveable during plasma discharge and optimization of ferromagnetic inserts to minimize toroidal field ripple

Ioki, Kimihiro; Chuyanov, V.*; Elio, F.*; Garkusha, D.*; Gribov, Y.*; Lamzin, E.*; Morimoto, Masaaki; Shimada, Michiya; Sugihara, Masayoshi; Terasawa, Atsumi; et al.

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

Two important design updates have been made in the ITER VV and in-vessel components recently. One is the introduction of limiters moveable during a plasma discharge, and the other is optimization of the ferromagnetic insert configuration to minimize the toroidal field ripple. In the new limiter concept, the limiters are retracted by 8 cm during the plasma flat top phase in the divertor configuration. This concept gives important advantages: (1) the particle and heat loads due to disruptions, ELMs and blobs on the limiters will be mitigated approximately by a factor 1.5 or more; (2) the gap between the plasma and the ICRH antenna can be reduced to improve the coupling of the ICRH power. The ferromagnetic inserts have previously not been planned to be installed in the outboard midplane region between equatorial ports due to irregularity of tangential ports for NB injection. The result is a relatively large ripple (1 %) in a limited region of the plasma, which nevertheless seems acceptable from the plasma performance viewpoint. However, toroidal field flux lines fluctuate 10 mm due to the large ripple in the FW region. To avoid problems due to the large TF flux line fluctuation, additional ferromagnetic inserts are now planned to be installed in the equatorial port region.

Journal Articles

Development of advanced tritium breeders and neutron multipliers for DEMO solid breeder blankets

Tsuchiya, Kunihiko; Hoshino, Tsuyoshi; Kawamura, Hiroshi; Mishima, Yoshinao*; Yoshida, Naoaki*; Terai, Takayuki*; Tanaka, Satoru*; Munakata, Kenzo*; Kato, Shigeru*; Uchida, Munenori*; et al.

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

no abstracts in English

Journal Articles

Development of the 170GHz gyrotron and equatorial launcher for ITER

Sakamoto, Keishi; Kasugai, Atsushi; Takahashi, Koji; Minami, Ryutaro*; Kariya, Tsuyoshi*; Mitsunaka, Yoshika*; Kobayashi, Noriyuki

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

no abstracts in English

Journal Articles

Engineering feature in the design of JT-60SA

Matsukawa, Makoto; JA-EU Satellite Tokamak Working Group; JT-60SA Design Team

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

no abstracts in English

Journal Articles

Surface analysis for the TFTR Armor tile exposed to D-T plasmas using nuclear technique

Kubota, Naoyoshi; Ochiai, Kentaro; Kutsukake, Chuzo; Hayashi, Takao; Shu, Wataru; Kondo, Keitaro; Verzilov, Y.*; Sato, Satoshi; Yamauchi, Michinori; Nishi, Masataka; et al.

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 7 Pages, 2007/03

Fuel and impurity particles show complicated behavior on the surface of plasma facing components (PFC) in fusion devices. The study is important for the design of the fuel recycling, safety management of the tritium inventory, etc. Quantitative measurements of hydrogen and lithium isotopes together with other impurities on the PFC surface exposed to D-T plasmas in TFTR were performed using the deuteron-induced nuclear reaction analysis, imaging plate method, full combustion method and activation analysis. The tritium depth profile was different from deuterium one. The surface tritium largely contributed to the whole tritium in the sample. On the other hand, the retained amount of lithium-6 was lager than that of lithium-7. This relates to the injection of enriched lithium-6 pellets in some campaigns. No other impurities were detected. So the large amount of tritium remained near the surface and did not diffuse more deeply, which gives a bright prospect for tritium safety.

Journal Articles

Status and key issues of reduced activation martensitic steels as the structural materials of ITER test blanket module and beyond

Tanigawa, Hiroyasu; Shiba, Kiyoyuki; Hirose, Takanori; Kasada, Ryuta*; Wakai, Eiichi; Jitsukawa, Shiro; Kimura, Akihiko*; Koyama, Akira*

Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 6 Pages, 2007/03

The status of research and development of reduced activation martensitic steels (RAMs) in Japan are reviewed and key issues suggested from recent achievements in Japan since the last conference are highlighted, with the aim of the fabrication for the ITER Test Blanket Module (TBM) and application for the DEMO reactor. It was pointed out that international collaboration would be desirable for research on key issues such as precipitate stability under irradiation or Ta effects which are common for all RAMs and require an extensive research effort.

Journal Articles

Studies on behavior of tritium in components and structure materials of tritium confinement and detritiation systems of ITER

Kobayashi, Kazuhiro; Isobe, Kanetsugu; Iwai, Yasunori; Hayashi, Takumi; Shu, Wataru; Nakamura, Hirofumi; Kawamura, Yoshinori; Yamada, Masayuki; Suzuki, Takumi; Miura, Hidenori*; et al.

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

no abstracts in English

Journal Articles

Experimental study on nuclear properties of water cooled pebble bed blanket

Sato, Satoshi; Verzilov, Y.*; Ochiai, Kentaro; Wada, Masayuki*; Kubota, Naoyoshi; Kondo, Keitaro; Yamauchi, Michinori; Nishitani, Takeo; Konno, Chikara

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

no abstracts in English

Journal Articles

Particle control under wall saturation in long-pulse high-density H-mode plasmas of JT-60U

Kubo, Hirotaka; Nakano, Tomohide; Asakura, Nobuyuki; Takenaga, Hidenobu; Tsuzuki, Kazuhiro; Oyama, Naoyuki; Kawashima, Hisato; Shimizu, Katsuhiro; Urano, Hajime; Fujimoto, Kayoko; et al.

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

no abstracts in English

Journal Articles

Active control of neoclassical tearing modes toward stationary high-beta plasmas in JT-60U

Isayama, Akihiko; Oyama, Naoyuki; Urano, Hajime; Suzuki, Takahiro; Takechi, Manabu; Hayashi, Nobuhiko; Nagasaki, Kazunobu*; Kamada, Yutaka; Ide, Shunsuke; Ozeki, Takahisa; et al.

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

no abstracts in English

Journal Articles

Ferritic insertion for reduction of toroidal magnetic field ripple on JT-60U

Shinohara, Koji; Sakurai, Shinji; Ishikawa, Masao; Tsuzuki, Kazuhiro*; Suzuki, Yutaka; Masaki, Kei; Naito, Osamu; Kurihara, Kenichi; Suzuki, Takahiro; Koide, Yoshihiko; et al.

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

Ferritic steel plates have been installed to improve the energetic ion confinement through reducing a toroidal magnetic field ripple. Aiming at cost-effective installation, orbit following calculations of energetic ions were performed for a design of ferritic installation on JT-60U by using the Fully three Dimensional magnetic field Orbit-Following Monte-Carlo (F3D OFMC) code. The installed ferritic steel adds the non-linear magnetic field on magnetic sensors for a plasma control and an equilibrium calculation. The code for a real-time control have been modified to take into account the magnetic field by ferritic steel. The plasma operation was successfully resumed and a real-time plasma control was successfully carried out after usual preparation processes. The heat load measurement indicates the improved confinement of energetic ions. These results are important for practical application of ferritic steel which is a leading candidate of a structural material on a demo reactor.

Journal Articles

Effects of "Sharpness" of the plasma cross-section on the stability of peeling-ballooning modes in tokamaks

Aiba, Nobuyuki; Tokuda, Shinji; Takizuka, Tomonori; Kurita, Genichi; Ozeki, Takahisa

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

Stabilities of peeling, ballooning and peeling-ballooning modes, which relate to edge-localized modes (ELMs), are investigated numerically with the linear ideal magnetohydrodynamic (MHD) stability code MARG2D. Effects of "sharpness" on the stability of the peeling-ballooning mode are examined, where the sharpness is defined in terms of the curvature at the top and bottom of the outermost flux surface. It is found for the first time that the stable pressure gradient significantly improves as the sharpness increases even when the ellipticity and the triangularity are unchanged. The sharpness is an important parameter for high performance H-mode operations with high pedestal pressure.

Journal Articles

Driving mechanism of toroidal rotation and momentum transport in JT-60U

Yoshida, Maiko; Koide, Yoshihiko; Takenaga, Hidenobu; Urano, Hajime; Oyama, Naoyuki; Kamiya, Kensaku; Sakamoto, Yoshiteru; Kamada, Yutaka; JT-60 Team

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

no abstracts in English

Journal Articles

Off-axis current drive and current profile control in JT-60U

Suzuki, Takahiro; Ide, Shunsuke; Oikawa, Toshihiro; Fujita, Takaaki; Ishikawa, Masao*; Seki, Masami; Matsunaga, Go; Takechi, Manabu; Naito, Osamu; Hamamatsu, Kiyotaka; et al.

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

For the first time, we have measured the current density profile for off-axis neutral beam current drive (NBCD), using motional Stark effect (MSE) diagnostic. A spatially localized NBCD profile was clearly observed at $$rho=0.6-0.8$$. The location was also confirmed by neutron emission profile measurement. The total amount of the driven current (0.15MA) was consistent with the decrease in the surface loop voltage. The off-axis current drive can raise safety factor (q) in the center and help to avoid instability that limits performance of the plasma. We have developed a real-time control system of the minimum q (qmin), using the off-axis current drive. Injection power of lower hybrid (LH) waves, and hence, its off-axis driven current controls qmin. In a high $$beta$$ plasma ($$beta_{N}=1.7$$, $$beta_{p}=1.5$$), the system was adopted to control qmin. With the control, qmin was raised and MHD fluctuations were suppressed. The stored energy increased by 16% with the MHD fluctuations suppressed.

Journal Articles

Improved performance in long-pulse ELMy H-mode plasmas with internal transport barrier in JT-60U

Oyama, Naoyuki; Isayama, Akihiko; Suzuki, Takahiro; Koide, Yoshihiko; Takenaga, Hidenobu; Ide, Shunsuke; Nakano, Tomohide; Asakura, Nobuyuki; Kubo, Hirotaka; Takechi, Manabu; et al.

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

After installation of ferritic steel tiles (FSTs) which reduced fast ion losses due to toroidal field ripple, the performance of long-pulse ELMy H-mode plasmas was improved in terms of sustained duration time for both high normalized beta ($$beta_N$$) and high thermal confinement enhancement factor ($$H_{98}$$). High $$beta_N$$$$>$$2.3 together with $$H_{98}$$$$sim$$1 was sustained for 23.1s ($$sim$$12$$tau_{rm R}$$) $$q_{rm 95} sim 3.3$$, which also provide high $$beta_{rm N}H_{rm H98(y,2)} ge 2.2$$, which is higher than ITER reference scenario. These long-pulse plasmas are possible candidates for ITER hybrid operation scenario.

Journal Articles

Hydrogen retention and carbon deposition in plasma facing wall and shadowed area of JT-60U

Masaki, Kei; Tanabe, Tetsuo*; Hirohata, Yuko*; Oya, Yasuhisa*; Shibahara, Takahiro*; Hayashi, Takao; Sugiyama, Kazuyoshi*; Arai, Takashi; Okuno, Kenji*; Miya, Naoyuki

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

Evaluation of fuel inventory and its retention process are critical issues for a next-step fusion device, especially with carbon-based wall. In order to resolve the issues, the hydrogen retention and carbon deposition analyses for the plasma facing surfaces and plasma-shadowed area of JT-60U have been performed. In JT-60U, erosion/deposition analyses for the plasma facing wall have shown that deposition was dominant at the inner-middle first wall and the inner divertor, whereas erosion dominant at the upper first wall and the outer divertor. Assuming toroidal symmetry in the erosion and deposition patterns, the net carbon erosion and deposition in the divertor area were estimated to be 0.34 kg and 0.55 kg, respectively. In a whole, the increment of carbon in the divertor region was 0.21 kg, which should be originated from the first wall. The hydrogen concentration in the thick deposition layer of the inner divertor was $$sim$$0.02 in (H+D)/C. In the plasma-shadowed area underneath the divertor region at around 420 K, re-deposited layers of $$sim$$2$$mu$$m-thick were found with high hydrogen concentration of $$sim$$0.8 in (H+D)/C. The carbon deposition rate in the plasma-shadowed area, however, was 8$$times$$10$$^{19}$$ atoms/s, which was one order smaller than that (6$$times$$10$$^{20}$$ atoms/s) on the wall surface.

Journal Articles

Measurement and analysis of the fluctuations and poloidal flow on JFT-2M tokamak

Hoshino, Katsumichi; Ido, Takeshi*; Nagashima, Yoshihiko*; Shinohara, Koji; Ogawa, Hiroaki; Kamiya, Kensaku; Kawashima, Hisato; Tsuzuki, Kazuhiro*; Kusama, Yoshinori; Oasa, Kazumi; et al.

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

We report on the potential/density fluctuations in the JFT-2M tokamak. We identified a geodesic acoustic mode (GAM) and its electric field structure. The GAM interacts with the background turbulence in consistent with a drift wave - zonal flow theory. The GAM modulates the turbulence, and the suppression depends on the direction and gradient of the flow velocity in consistent with a theory. During the H-mode, the GAM disappears presumably due to the suppression of the turbulence. We analysed the low frequency potential oscillation during the H-mode. A wavelet analysis showed a low frequency characteristic potential fluctuations (several handred kHz), which disappears in the L-mode and at the occurence of ELM. Observed poloidal flow is about 20 times as large as that of the GAM during the H-mode. If the potential has a spatial inhomogineity, there is a possibility that this low frequency fluctuation comes from the EXB flow or the zonal flow.

Journal Articles

Enhanced H-mode pedestal and energy confinement by reduction of toroidal field ripple in JT-60U

Urano, Hajime; Oyama, Naoyuki; Kamiya, Kensaku; Koide, Yoshihiko; Takenaga, Hidenobu; Takizuka, Tomonori; Yoshida, Maiko; Kamada, Yutaka; JT-60 Team

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

The pedestal pressure and energy confinement of H-mode plasmas were improved by the reduction of toroidal field (TF) ripple with the installation of ferritic steel tiles (FSTs) in JT-60U. The profile of toroidal rotation $$V_mathrm{T}$$ became less counter and the pedestal pressure $$p_mathrm{ped}$$ is increased with FSTs particularly in case where co-NBI was used at a large volume configuration. ELM frequency $$f_mathrm{ELM}$$ was reduced and ELM energy loss $$Delta W_{ELM}$$ was increased. For increased $$p_mathrm{ped}$$ due to $$V_mathrm{T}$$ enhanced in co-direction and the reduction of TF ripple, the spatial width of H-mode pedestal became wider. The energy confinement was improved by enhancing $$V_mathrm{T}$$ in co-direction and by the reduction of TF ripple.

55 (Records 1-20 displayed on this page)