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Journal Articles

A Conceptual design study for the error field correction coil power supply in JT-60SA

Matsukawa, Makoto; Shimada, Katsuhiro; Yamauchi, Kunihito; Gaio, E.*; Ferro, A.*; Novello, L.*

Plasma Science and Technology, 15(3), p.257 - 260, 2013/03

 Times Cited Count:7 Percentile:31.27(Physics, Fluids & Plasmas)

To realize high performance plasmas in tokamak devices, error field correction (EFC) is one of the very important issues. Actually, error field correction coil is being planned in ITER using superconducting coils, while normal copper coils will be employed in JT-60SA. Similar coils are installed and under operation in many devices over the world. In the case of JT-60SA, EFC coils will be realized by 12 (or 18) sector coils installed inside the vacuum vessel. This paper describes a conceptual design study for the circuit configuration and control strategy of the power supply system of these EFC coils. In conclusion, to minimize the number of current feeders and semiconductor power devices, multi-phase inverter is the best solution not only from the cost merit but also from a view point of canceling the induced voltage of axisymmetric magnetic component.

Journal Articles

Estimation of TBR on the gap between neighboring blanket modules in the DEMO reactor

Someya, Yoji; Tobita, Kenji

Plasma Science and Technology, 15(2), p.171 - 174, 2013/02

 Times Cited Count:3 Percentile:13.73(Physics, Fluids & Plasmas)

When one wants to simply estimate Tritium Breeding Ratio (TBR) using 1D analysis, the TBR may be reduced from a "local" TBR for the breeding zone of a blanket module by multiplying the breeder coverage. The gap between adjoining modules and the frames of the modules are regarded as non-breeding zones. Based on the methodology, the width of the blanket modules gap was determined to be 5 mm or less in the SlimCS DEMO reactor. Contrary to this, recent study revealed that neutrons scattered in the non-breeding zones can enter breeding zones, contributing to tritium production. This means that the estimation method mentioned above tends to underestimate TBR. In order to assess the scattering effect quantitatively, we carried out the 3D Monte Carlo code MCNP-5 calculation. When a values of the TBR compare the MCNP to the previous method, indicating little decrease in TBR for the gap of less than 2 cm. The allowance of the gap will facilitate access of remote handling systems for replacement of the blanket modules.

Journal Articles

Minimization of reactive power fluctuation in JT-60SA magnet power supply

Shimada, Katsuhiro; Terakado, Tsunehisa; Yamauchi, Kunihito; Matsukawa, Makoto; Baulaigue, O.*; Coletti, R.*; Coletti, A.*; Novello, L.*

Plasma Science and Technology, 15(2), p.184 - 187, 2013/02

 Times Cited Count:4 Percentile:18.24(Physics, Fluids & Plasmas)

Journal Articles

Design study of top lid with clamp structure in JT-60SA cryostat

Nakamura, Shigetoshi; Shibama, Yusuke; Masaki, Kei; Sakasai, Akira

Plasma Science and Technology, 15(2), p.188 - 191, 2013/02

 Times Cited Count:0 Percentile:0.01(Physics, Fluids & Plasmas)

The JT-60SA project is to contribute to realization of fusion energy by supporting exploitation of ITER and by complementing ITER and engineering issues for DEMO reactors. A main component providing vacuum insulation, radiation shield, and tokamak machine components' support, is cryostat. We present integrity of top lid of the cryostat, which is final part to close a cryostat vessel. We calculate clamp structural parameters, which are weight, dimension, and stiffness, required to fasten a top flange of the top lid with a body flange of the cryostat vessel. To achieve vacuum insulation of 10$$^{-3}$$ Pa, the top flange and the body flange are lightly welded. Under vacuum condition, tensile load is loaded to the weld by bending deformation of the top flange. Bending moment is loaded to the weld by radial component of the deformation. The weld needs clamp structure to reduce these loads. We present integrity of the top lid with clamp.

Journal Articles

Detailed analysis of the transient voltage in a JT-60SA PF coil circuit

Yamauchi, Kunihito; Shimada, Katsuhiro; Terakado, Tsunehisa; Matsukawa, Makoto; Coletti, R.*; Lampasi, A.*; Gaio, E.*; Coletti, A.*; Novello, L.*

Plasma Science and Technology, 15(2), p.148 - 151, 2013/02

 Times Cited Count:6 Percentile:27.07(Physics, Fluids & Plasmas)

Journal Articles

Vacuum insulation and achievement of 980 keV, 185 A/m$$^{2}$$ H$$^{-}$$ ion beam acceleration at JAEA for the ITER neutral beam injector

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

Plasma Science and Technology, 15(2), p.179 - 183, 2013/02

 Times Cited Count:1 Percentile:4.55(Physics, Fluids & Plasmas)

Vacuum insulation is a common issue for the accelerator and the HV bushing for the ITER NBI. The HV bushing has five-stage structure and each stage consists of double-layered insulators. Hence, several triple points exist around the insulators. To reduce electric field at those points simultaneously, three types of stress ring were developed. In voltage holding test of a full-scale mockup equipped with those stress rings, 120% of rated voltage was sustained and the voltage holding capability required in ITER was verified. In the MeV accelerator, voltage holding capability was not sufficient due to breakdown triggered by electric field concentration at edge and corner on grid components. By extending gap length, 1 MV was sustained in vacuum. Furthermore, with new accelerator grids which compensates beam deflection due to magnetic field and space charge repulsion between beamlets, 980 keV, 185 A/m$$^{2}$$ H$$^{-}$$ ion beam acceleration was demonstrated, which was close to ITER requirement.

Journal Articles

Development of the PARASOL code and full particle simulation of tokamak plasma with an open-field SOL-divertor region using PARASOL

Takizuka, Tomonori

Plasma Science and Technology, 13(3), p.316 - 325, 2011/06

 Times Cited Count:11 Percentile:44.82(Physics, Fluids & Plasmas)

In order to investigate the particle and heat control with divertor system of fusion reactors, numerical simulations have been widely carried out. Fluid codes require further improvement of physics modeling for edge plasmas. The full particle simulation is powerful to study fundamental physics of open-field SOL-divertor plasmas as well as of the whole tokamak plasma including SOL-divertor region. PARASOL code with PIC method and binary collision model has been developed in JAERI and JAEA. Simulations with PARASOL code have been carried out for the above purpose. The one-dimensional (1D) version of PARASOL was applied to investigate the Bohm criterion, the supersonic flow, the SOL heat conduction, and so on. The ELM heat propagation was studied with the 1D-dynamic PARASOL. The two-dimensional version of PARASOL for the whole tokamak plasma with SOL-divertor region was useful to simulate the SOL flow pattern, the electric field formation etc. Based on PARASOL simulation results, physics modeling for the fluid simulation has been developed.

Journal Articles

Present status of JT-60SA project and development of heating systems for JT-60SA

Ikeda, Yoshitaka; JT-60SA Team

Plasma Science and Technology, 13(3), p.367 - 375, 2011/06

 Times Cited Count:0 Percentile:0.01(Physics, Fluids & Plasmas)

This paper describes the present status of the JT-60SA (JT-60 Super Advanced) project which has been implemented jointly by Europe and Japan since 2007. Design of the main tokamak components were completed in late 2008, where all the scientific missions are preserved to contribute to ITER and DEMO reactors. The construction of the JT-60SA has began with procurement activities for the superconducting magnet systems, vacuum vessel, in-vessel components and other components under the relevant procurement arrangements between the implementing agencies of JAEA (Japan Atomic Energy Agency) in Japan and Fusion for Energy in Europe. Designs and developments of the auxiliary heating systems for JT-60SA have been progressed at JAEA so as to provide the total injection power of 41 MW for 100s.

Journal Articles

Energetics of resistive wall modes in flowing plasmas

Hirota, Makoto

Plasma Science and Technology, 11(4), p.409 - 412, 2009/08

 Times Cited Count:4 Percentile:16.92(Physics, Fluids & Plasmas)

Stability of magnetohydrodynamic (MHD) waves subject to Alfv$'e$n and sound resonances and small resistivity at a conductive wall is formally discussed in terms of wave energy (or, more precisely, wave action). Negative energy wave, which may exist in the presence of mean flow, is shown to be destabilized by the resistive wall, where its growth rate is characterized by the energy dissipation rate. The effect of resonance is examined as well based on a recent knowledge of wave energy for Alfv$'e$n and sound continuum modes. Resonant coupling between an eigenmode and a continuum mode having the same sign of energy results in phase mixing (or continuum) damping. In contrast, if their signs are opposite, such resonance triggers an instability.

Journal Articles

Suppression of neoclassical tearing modes towards stationary high-beta plasmas in JT-60U

Isayama, Akihiko; JT-60 Team

Plasma Science and Technology, 8(1), p.36 - 40, 2006/01

 Times Cited Count:3 Percentile:10.97(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Study of particle behavior for steady-state operation in JT-60U

Kubo, Hirotaka; JT-60 Team

Plasma Science and Technology, 8(1), p.50 - 54, 2006/01

 Times Cited Count:2 Percentile:7.15(Physics, Fluids & Plasmas)

no abstracts in English

Journal Articles

Long pulse operation of high performance plasmas in JT-60U

Ide, Shunsuke; JT-60 Team

Plasma Science and Technology, 8(1), p.1 - 4, 2006/01

 Times Cited Count:0 Percentile:0.01(Physics, Fluids & Plasmas)

Recent progress in development of high performance plasma and efforts to prolong their sustainment towards ITER advanced operations and a steady-state reactor in JT-60U are presented focusing following achievements; $$beta$$N=3 sustained for 6.2s ($$sim$$4.1tR) without NTMs in normal shear, fBS$$sim$$0.45 sustained for 5.8s ($$sim$$2.8tR) under nearly full CD in weak a shear plasma, fBS$$sim$$0.75 sustained for 7.4s (2.7tR) under nearly full CD in a reversed shear plasma. Furthermore, importance of these results and issues in advanced tokamak development will be discussed.

Journal Articles

Dynamics of secondary large-scale structures in ETG turbulence simulations

Li, J.*; Kishimoto, Yasuaki; Dong, J.*; Miyato, Naoaki; Matsumoto, Taro

Plasma Science and Technology, 8(1), p.110 - 113, 2006/01

The dynamics of secondary large-scale structures in electron-temperature-gradient (ETG) turbulence is investigated based on gyrofluid simulations in sheared slab geometry. It is found that structural bifurcation to zonal flow dominated or streamer-like states depends on the spectral anisotropy of turbulent ETG fluctuation, which is governed by the magnetic shear. The turbulent electron transport is suppressed by enhanced zonal flows. However, it is still low even if the streamer is formed in ETG turbulence with strong shears. It is shown that the low transport may be related to the secondary excitation of poloidal long-wavelength mode due to the beat wave of the most unstable components or a modulation instability. This large-scale structure with a low frequency and a long wavelength may saturate, or at least contribute to the saturation of ETG fluctuations through a poloidal mode coupling. The result suggests a low fluctuation level in ETG turbulence.

Journal Articles

Application of Kelvin probe to studies of fusion reactor materials under irradiation

Luo, G.-N.*; Yamaguchi, Kenji; Terai, Takayuki*; Yamawaki, Michio*

Plasma Science and Technology, 7(4), p.2982 - 2984, 2005/08

no abstracts in English

Journal Articles

A Consideration on increasing current density in normal conducting toroidal field coil for spherical tokamak power plant

Song, Y.*; Nishio, Satoshi

Plasma Science and Technology, 7(2), p.2731 - 2733, 2005/04

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:0.02(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

Progress in physics and technology developments for the modification of JT-60

Tamai, Hiroshi; Matsukawa, Makoto; Kurita, Genichi; Hayashi, Nobuhiko; Urata, Kazuhiro*; Miura, Yushi; Kizu, Kaname; Tsuchiya, Katsuhiko; Morioka, Atsuhiko; Kudo, Yusuke; et al.

Plasma Science and Technology, 6(1), p.2141 - 2150, 2004/02

 Times Cited Count:2 Percentile:6.54(Physics, Fluids & Plasmas)

The dominant issue for the the modification program of JT-60 (JT-60SC) is to demonstrate the steady state reactor relevant plasma operation. Physics design on plasma parameters, operation scenarios, and the plasma control method are investigated for the achievement of high-$$beta$$. Engineering design and the R&D on the superconducting magnet coils, radiation shield, and vacuum vessel are performed. Recent progress in such physics and technology developments is presented.

Journal Articles

Results and future plan of JT-60U towards steady-state tokamak reactor

Sakurai, Shinji; JT-60 Team

Plasma Science and Technology, 6(1), p.2151 - 2158, 2004/02

 Times Cited Count:0 Percentile:0.02(Physics, Fluids & Plasmas)

no abstracts in English

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