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Journal Articles

Development of advanced inductive scenarios for ITER

Luce, T. C.*; Challis, C. D.*; Ide, Shunsuke; Joffrin, E.*; Kamada, Yutaka; Politzer, P. A.*; Schweinzer, J.*; Sips, A. C. C.*; Stober, J.*; Giruzzi, G.*; et al.

Nuclear Fusion, 54(1), p.013015_1 - 013015_15, 2013/12

 Times Cited Count:20 Percentile:19.59(Physics, Fluids & Plasmas)

Journal Articles

Plasma size scaling of avalanche-like heat transport in tokamaks

Jolliet, S.; Idomura, Yasuhiro

Nuclear Fusion, 52(2), p.023026_1 - 023026_14, 2012/02

Journal Articles

Edge pedestal characteristics in JET and JT-60U tokamaks under variable toroidal field ripple

Urano, Hajime; Saibene, G.*; Oyama, Naoyuki; Parail, V.*; de Vries, P.*; Sartori, R.*; Kamada, Yutaka; Kamiya, Kensaku; Loarte, A.*; L$"o$nnroth, J.*; et al.

Nuclear Fusion, 51(11), p.113004_1 - 113004_10, 2011/11

 Times Cited Count:7 Percentile:64.01(Physics, Fluids & Plasmas)

The effect of TF ripple on the edge pedestal characteristics are examined in JET and JT-60U. By the installation of ferritic inserts, TF ripple was reduced from $$1%$$ to $$0.6%$$ in JT-60U. In JET, TF ripple was varied from $$0.1%$$ to $$1%$$ by feeding different currents to TF coils. The pedestal pressure was similar with reduced ripple in JT-60U. In JET, no clear difference of the pedestal characteristics was also observed. The edge toroidal rotation clearly decreased in counter direction by increased TF ripple. However, in JT-60U, the ELM frequency decreased by $$sim 20%$$ and the increased ELM loss power by $$30%$$ with reduced ripple. In JET, ELM frequency increases only slightly with increased TF ripple. From this inter-machine experiment, TF ripple less than $$1%$$ does not strongly affect the pedestal pressure. The effect of TF ripple on pedestal characteristics at lower collisionality close to ITER should be investigated as a next step study.

Journal Articles

ITER test blanket module error field simulation experiments at DIII-D

Schaffer, M. J.*; Snipes, J. A.*; Gohil, P.*; de Vries, P.*; Evans, T. E.*; Fenstermacher, M. E.*; Gao, X.*; Garofalo, A. M.*; Gates, D. A.*; Greenfield, C. M.*; et al.

Nuclear Fusion, 51(10), p.103028_1 - 103028_11, 2011/10

 Times Cited Count:32 Percentile:15.51(Physics, Fluids & Plasmas)

Experiments at DIII-D investigated the effects of ferromagnetic error fields similar to those expected from proposed ITER Test Blanket Modules (TBMs). Studied were effects on: plasma rotation and locking; confinement; L-H transition; edge localized mode (ELM) suppression by resonant magnetic perturbations; ELMs and the H-mode pedestal; energetic particle losses; and more. The experiments used a 3-coil mock-up of 2 magnetized ITER TBMs in one ITER equatorial port. The experiments did not reveal any effect likely to preclude ITER operations with a TBM-like error field. The largest effect was slowed plasma toroidal rotation v across the entire radial profile by as much as $$Delta v/v_{0} sim 50%$$ via non-resonant braking. Changes to global $$Delta n/n_{0}$$, $$Delta v/v_{0}$$ and $$Delta H_{98}/H_{98,0}$$ were $$sim$$3 times smaller. These effects are stronger at higher $$beta$$ and lower $$v_{0}$$. Other effects were smaller.

Journal Articles

ITER project and fusion technology

Takatsu, Hideyuki

Nuclear Fusion, 51(9), p.094002_1 - 094002_16, 2011/09

 Times Cited Count:6 Percentile:68.04(Physics, Fluids & Plasmas)

This is a summary paper on the three sessions on ITER (ITR), Fusion Technology (FTP) and Safety, Environment and Economic Aspect of Fusion Energy (SEE) presented at the 23rd IAEA Fusion Energy Conference in October, 2010, in Daejon, South Korea. Highlights of the three sessions are summarized with a minimum set of background information.

Journal Articles

Mechanisms of plasma rotation effects on the stability of type-I edge-localized mode in tokamaks

Aiba, Nobuyuki; Furukawa, Masaru*; Hirota, Makoto; Oyama, Naoyuki; Kojima, Atsushi; Tokuda, Shinji*; Yagi, Masatoshi

Nuclear Fusion, 51(7), p.073012_1 - 073012_9, 2011/07

We investigate numerically the destabilizing effect of a toroidal rotation on the edge localized MHD mode, which induces the large amplitude edge localized mode (ELM). As the results of this analysis, we reveal that the toroidal rotation with shear can destabilize this MHD mode, and the destabilization is caused by the difference between the plasma rotation frequency and the frequency of the unstable mode. Based on these results, we investigate numerically the stability of JT-60U type-I ELMy H-mode plasmas, and show that the toroidal rotation plays an important role for making the difference of ELM behavior observed in JT-60U plasmas with different plasma rotation profiles.

Journal Articles

Technology development for the manufacture of Nb$$_{3}$$Sn conductors for ITER Toroidal Field coils

Takahashi, Yoshikazu; Isono, Takaaki; Hamada, Kazuya; Nunoya, Yoshihiko; Nabara, Yoshihiro; Matsui, Kunihiro; Hemmi, Tsutomu; Kawano, Katsumi; Koizumi, Norikiyo; Oshikiri, Masayuki; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

Japan Atomic Energy Agency is procuring the Nb$$_{3}$$Sn superconductors for Toroidal Field (TF) coils under the ITER project. Because manufacturing amount of Nb$$_{3}$$Sn strands is quite large compared with the past experience and required superconducting performance is higher than that of the model coils which have been fabricated and tested in the ITER-EDA, quality control technique is very important for the manufacture of the strands. Sophisticated control technique is also required for the jacketing, in order to fabricate the conductors with the precise outer diameter and without leakage at welding part. Cu dummy conductor with full length (760 m) has been fabricated successfully and all jacketing technology was confirmed through this fabrication. The fabrication of the Nb$$_{3}$$Sn conductor for TF coils will start in March 2010.

Journal Articles

3D effect of ferromagnetic materials on alpha particle power loads on first wall structures and equilibrium on ITER

Shinohara, Koji; Kurki-Suonio, T.*; Spong, D.*; Asunta, O.*; Tani, Keiji*; Strumberger, E.*; Briguglio, S.*; G$"u$nter, S.*; Koskela, T.*; Kramer, G.*; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

Journal Articles

Demonstration of 500 keV beam acceleration on JT-60 negative-ion-based neutral beam injector

Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

Hydrogen negative ion beams of 490keV, 3A and 510 keV, 1A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of $$sim$$ 2 m$$^{2}$$ for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m$$^{2}$$). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60 SA and ITER.

Journal Articles

Analytic theory of a matching problem generalized for stability analysis of resistive wall modes in rotating plasmas

Shiraishi, Junya; Tokuda, Shinji*

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

no abstracts in English

Journal Articles

Effects of strong E$$times$$B flow on gyrokinetics

Miyato, Naoaki; Scott, B. D.*; Tokuda, Shinji*; Yagi, Masatoshi

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

Based on the phase space Lagrangian Lie-transform perturbation method and the field theory, a reduced kinetic model with large E$$times$$B flow beyond the standard ordering ($$V_{Etimes B}/v_{th}sim O(rho/L)$$) is constructed by modifying the guiding-centre phase space trans-formation. The model can be regarded as a natural extension of the standard model without flow since the symplectic part of the Lagrangian is the same as the standard one formally. Some aspects of the model are revealed and effects of the flow are discussed in course of comparison with the standard model. The push-forward representation of general particle fluid moment is presented in the subsonic flow case. In sonic flow case, corrections to the reduced quasi-neutrality condition due to the E$$times$$B flow are found by variational derivation of the push-forward representation of particle density.

Journal Articles

Interactions between MHD instabilities in the wall-stabilized high-$$beta$$ plasmas

Matsunaga, Go; Aiba, Nobuyuki; Shinohara, Koji; Sakamoto, Yoshiteru; Takechi, Manabu; Suzuki, Takahiro; Asakura, Nobuyuki; Isayama, Akihiko; Oyama, Naoyuki; Yoshida, Maiko; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

Journal Articles

Inward pinch of high-Z impurity due to atomic processes in a rotating tokamak plasma and the effect of radial electric field

Hoshino, Kazuo; Toma, Mitsunori*; Shimizu, Katsuhiro; Nakano, Tomohide; Hatayama, Akiyoshi*; Takizuka, Tomonori

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 6 Pages, 2011/03

The transport of high-Z impurity in a toroidally rotating tokamak plasma is investigated analytically and numerically. It is shown that the inward pinch is driven by the atomic processes in co- and ctr- rotating plasmas. This inward pinch is enhanced by the radial electric field. It is derived that the negative and positive radial electric fields cause the inward pinch and the outward movement (unpinch) of the high-Z impurity, respectively, under the influence of Coulomb collisions with the rotating background plasma. In the ctr-rotation case, the inward pinch becomes significant with increasing toroidal rotation velocity, because the directions of the both pinches are inward. On the other hand, in the co-rotation case, these pinches have opposite directions. Therefore, the unpinch due to the positive radial electric field is decreased by the inward pinch due to the atomic processes. These tendencies are consistent with the tungsten accumulation observed in the JT-60U.

Journal Articles

Integrated simulation of ELM triggered by pellet through energy absorption and transport enhancement

Hayashi, Nobuhiko; Parail, V.*; Koechl, F.*; Aiba, Nobuyuki; Takizuka, Tomonori; Wiesen, S.*; Lang, P.*; Oyama, Naoyuki; Ozeki, Takahisa; JET-EFDA Contributors*

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

Journal Articles

Development of full-size mockup bushing for 1 MeV ITER NB system

Tobari, Hiroyuki; Inoue, Takashi; Hanada, Masaya; Dairaku, Masayuki; Watanabe, Kazuhiro; Umeda, Naotaka; Taniguchi, Masaki; Kashiwagi, Mieko; Yamanaka, Haruhiko; Takemoto, Jumpei; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

High voltage (HV) bushing in the ITER NBI is one of critical components, which acts as a feedthrough for electric power and cooling water from the -1 MV power supply in SF$$_{6}$$ gas to beam source inside vacuum. JAEA has overcome a longstanding issue on manufacturing of a large bore ceramic ring with 1.56 m in diameter as the insulator of the five-stage HV bushing. Joining method of the ceramic and metal flange with thick Kovar plate to form vacuum boundary was also developed. By assembling components, a full-size mockup bushing simulating one stage of the HV bushing was successfully manufactured. In the voltage holding test, the high voltage of 240 kV including the margin of 20 % of a rated voltage was sustained for 3600 s without breakdown, and the voltage holding capability required in ITER was successfully verified.

Journal Articles

Impact of toroidal rotation and safety factor on ion turbulent transport in tokamaks

Idomura, Yasuhiro; Jolliet, S.; Yoshida, Maiko; Urano, Hajime

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

An impact of the toroidal rotation and the safety factor q on the ion temperature gradient driven (ITG) turbulence is studied using a global gyrokinetic toroidal full-f five dimensional Euleriancode GT5D. In the rotation scan numerical experiments, the radial electric field Er profile is changed depending on the toroidal rotation. Although local transport levels are affected by the Er profile, global transport properties are not changed, when the magnitudes of its shearing rate are in similar levels on average. In the q scan numerical experiments, turbulent transport is significantly enhanced at higher q. It is found that the stabilizing effect of Er shear on liner ITG modes becomes less effective at higher q. Both the ion heat transport and the non-diffusive momentum transport are enhanced. The former leads to lower ion temperature gradient, while the latter produces larger inward momentum flux and co-current spontaneous rotation in the plasma core.

Journal Articles

Estimation of kinetic parameters based on chirping Alfv$'e$n Eigenmodes

Lesur, M.*; Idomura, Yasuhiro; Shinohara, Koji; Garbet, X.*

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

Alfv$'e$n Eigenmodes (AEs) with frequency sweeping (chirping AEs) are analyzed based on the so-called Berk-Breizman (BB) model. Kinetic parameter regimes with chirping nonlinear solutions are delimited, and a new quasi-periodic chirping regime is found, where the quasi-period of chirping events depends on the linear growth rate. Fundamental kinetic parameters such as the linear drive and the external damping rate are estimated by fitting nonlinear chirping characteristics between the experiment and the BB model. This approach is applied to Toroidicity-induced AEs on JT-60U, which suggests the existence of modes far from marginal stability. Two collision models are considered, and it is shown that dynamical friction and velocity-space diffusion are essential to reproduce nonlinear features observed in experiments. The results are validated by recovering measured growth and decay of perturbation amplitude, and by estimating collision frequencies from experimental equilibrium data.

Journal Articles

Overview of anomalous toroidal momentum transport

Peeters, A. G.*; Angioni, C.*; Bortolon, A.*; Camenen, Y.*; Casson, F. J.*; Dubal, B.*; Fiederspiel, L.*; Hornsby, W. A.*; Idomura, Yasuhiro; Kluy, N.*; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 13 Pages, 2011/03

Journal Articles

Transport and turbulence with innovative plasma shapes in the TCV tokamak

Labit, B.*; Pochelon, A.*; Rancic, M.*; Piras, F.*; Bencze, A.*; Bottino, A.*; Brunner, S.*; Camenen, Y.*; Chattopadhyay, P. K.*; Coda, S.*; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

Journal Articles

1 MV holding and beam optics in a multi-aperture multi-grid accelerator for ITER NBI

Kashiwagi, Mieko; Taniguchi, Masaki; Kojima, Atsushi; Dairaku, Masayuki; Hanada, Masaya; Hemsworth, R. S.*; Mizuno, Takatoshi*; Takemoto, Jumpei; Tanaka, Masanobu*; Tanaka, Yutaka*; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

At JAEA, a multi-aperture multi-grid accelerator has been developed for the ITER neutral beam system. A target is H$$^{-}$$ ion beam acceleration of 0.5 A (200 A/m$$^{2}$$) at 1 MeV. In real accelerators, it was found that the voltage holding was about a half of that obtained in an ideal small electrode. After applying necessary gap length and radii of edges of grid supports to lower local electric field concentrations, the accelerator succeeded in sustaining 1 MV for 4000 s. As a result, beam parameters were increased to 879 keV, 0.36 A (157 A/m$$^{2}$$) at perveance matched condition from 796 kV, 0.32 A (140 A/m$$^{2}$$) reported in FEC2008. In the beam acceleration, the beamlet deflections due to magnetic field and space charge repulsion caused direct interceptions, that resulted in limitations in the beam energy and current. Compensation of these beamlet deflections has been tested applying aperture offset and field shaping plate, which were examined in a three-dimensional beam analysis.

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