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Journal Articles

Conductance of a long rectangular channel; Pressure dependence

Ogiwara, Norio; Hikichi, Yusuke*; Kamiya, Junichiro; Kinsho, Michikazu; Yoshida, Hajime*; Arai, Kenta*

Journal of the Vacuum Society of Japan, 60(12), p.475 - 480, 2017/12

Journal Articles

Large trigonal-field effect on spin-orbit coupled states in a pyrochlore iridate

Uematsu, Daisuke*; Sagayama, Hajime*; Arima, Takahisa*; Ishikawa, Jun*; Nakatsuji, Satoru*; Takagi, Hidenori*; Yoshida, Masahiro*; Mizuki, Junichiro; Ishii, Kenji

Physical Review B, 92(9), p.094405_1 - 094405_6, 2015/09

 Times Cited Count:18 Percentile:68.15(Materials Science, Multidisciplinary)

Journal Articles

Effects of toroidal rotation shear and magnetic shear on thermal and particle transport in plasmas with electron cyclotron heating on JT-60U

Yoshida, Maiko; Honda, Mitsuru; Narita, Emi*; Hayashi, Nobuhiko; Urano, Hajime; Nakata, Motoki; Miyato, Naoaki; Takenaga, Hidenobu; Ide, Shunsuke; Kamada, Yutaka

Nuclear Fusion, 55(7), p.073014_1 - 073014_9, 2015/07

 Times Cited Count:13 Percentile:61.42(Physics, Fluids & Plasmas)

Conditions without the increases in the thermal and particle transport with ECH have been experimentally investigated in positive magnetic shear (PS), weak magnetic shear (WS) and reversed magnetic shear (RS) plasmas with internal transport barriers (ITBs) on JT-60U. The ion heat diffusivity around an internal transport barrier in the ion temperature ($$T_{rm i}$$-ITB) remains constant with ECH when a large negative toroidal rotation shear is formed before the ECH. The condition does not depend on the electron to ion temperature ratio ($$T_{rm e}$$/$$T_{rm i}$$) and ECH power. The electron heat diffusivity around a $$T_{rm e}$$-ITB stays constant with ECH when the magnetic shear is negative around the Te-ITB region. Effective particle transport remains constant or reduces during ECH under the condition of negative magnetic shear.

Journal Articles

Integrated modelling of toroidal rotation with the 3D non-local drift-kinetic code and boundary models for JT-60U analyses and predictive simulations

Honda, Mitsuru; Satake, Shinsuke*; Suzuki, Yasuhiro*; Yoshida, Maiko; Hayashi, Nobuhiko; Kamiya, Kensaku; Matsuyama, Akinobu; Shinohara, Koji; Matsunaga, Go; Nakata, Motoki; et al.

Nuclear Fusion, 55(7), p.073033_1 - 073033_11, 2015/07

 Times Cited Count:5 Percentile:29.96(Physics, Fluids & Plasmas)

Journal Articles

Roles of argon seeding in energy confinement and pedestal structure in JT-60U

Urano, Hajime; Nakata, Motoki; Aiba, Nobuyuki; Kubo, Hirotaka; Honda, Mitsuru; Hayashi, Nobuhiko; Yoshida, Maiko; Kamada, Yutaka; JT-60 Team

Nuclear Fusion, 55(3), p.033010_1 - 033010_9, 2015/03

 Times Cited Count:26 Percentile:85.34(Physics, Fluids & Plasmas)

Physics picture of improving energy confinement with argon seeding at high density has been investigated in JT-60U. Better confinement is sustained at high density by argon seeding accompanied by higher core and pedestal temperatures. Peaked density profiles are kept with argon seeding. Density peaking and dilution effects lower the pedestal density at a given averaged density. The pedestal density in the argon seeded plasmas which is relatively lower than that in a single deuterium puff enables the pedestal temperature to be higher. The density peaking is a key factor of sustaining better confinement in argon seeded H-mode plasmas.

Journal Articles

Boundary condition for toroidal plasma flow imposed at the separatrix in high confinement JT-60U plasmas with edge localized modes and the physics process in pedestal structure formation

Kamiya, Kensaku; Honda, Mitsuru; Urano, Hajime; Yoshida, Maiko; Kamada, Yutaka; Ito, Kimitaka*; JT-60 Team

Physics of Plasmas, 21(12), p.122517_1 - 122517_8, 2014/12

 Times Cited Count:13 Percentile:61.76(Physics, Fluids & Plasmas)

Modulation Charge eXchange Recombination Spectroscopy (MCXRS) measurements with high spatial and temporal resolution have made the evaluation of the toroidal plasma flow of fully stripped carbon impurity ions in the JT-60U tokamak peripheral region (including in particular separatrix) possible with a better signal-to-noise ratio. Boundary condition of Vt imposed at the separatrix in ELMy H-mode plasmas has been identified, comparing between co- and counter-NBI discharges. The Vt value at the separatrix is not held fixed at the zero, varying with momentum input direction, but being not strongly affected by the ELM event. A non-zero Vt value at the separatrix might be connected to fast ion losses due to toroidal field ripple that results in formation of a negative radial electric field (Er) layer having almost zero (or very weak positive) Er-shear value at the separatrix. Improved understanding of physics process in pedestal structure formation for the Vt and Er is also discussed.

Journal Articles

Experimental analyses and predictive simulations of toroidal rotation driven by the neoclassical toroidal viscosity in rippled tokamaks

Honda, Mitsuru; Satake, Shinsuke*; Suzuki, Yasuhiro*; Matsunaga, Go; Shinohara, Koji; Yoshida, Maiko; Matsuyama, Akinobu; Ide, Shunsuke; Urano, Hajime

Nuclear Fusion, 54(11), p.114005_1 - 114005_14, 2014/11

 Times Cited Count:10 Percentile:52.66(Physics, Fluids & Plasmas)

Journal Articles

Integrated modeling of toroidal rotation with the 3D non-local drift-kinetic code and boundary models for JT-60U analyses and predictive simulations

Honda, Mitsuru; Satake, Shinsuke*; Suzuki, Yasuhiro*; Yoshida, Maiko; Hayashi, Nobuhiko; Kamiya, Kensaku; Matsuyama, Akinobu; Shinohara, Koji; Matsunaga, Go; Nakata, Motoki; et al.

Proceedings of 25th IAEA Fusion Energy Conference (FEC 2014) (CD-ROM), 8 Pages, 2014/10

Journal Articles

Role of seed impurity for H-mode plasmas in JT-60U

Urano, Hajime; Nakata, Motoki; Aiba, Nobuyuki; Kubo, Hirotaka; Honda, Mitsuru; Yoshida, Maiko; Hayashi, Nobuhiko; Kamada, Yutaka; JT-60 Team

Europhysics Conference Abstracts (Internet), 38F, p.P4.018_1 - P4.018_4, 2014/06

This paper reports the analysis result of heat transport and pedestal structure in H-mode plasmas with and without argon seeding on JT-60U.

Journal Articles

Numerical prediction on heat transfer-characteristics of supercritical pressure water in a heated pipe based on three dimensional two-fluid model

Ose, Yasuo*; Yoshimori, Hajime*; Misawa, Takeharu; Yoshida, Hiroyuki; Takase, Kazuyuki

Nihon Kikai Gakkai Dai-26-Kai Keisan Rikigaku Koenkai Rombunshu (CD-ROM), p.701_1 - 701_2, 2013/11

no abstracts in English

Journal Articles

Temporal and spatial responses of temperature, density and rotation to electron cyclotron heating in JT-60U

Yoshida, Maiko; Ide, Shunsuke; Takenaga, Hidenobu; Honda, Mitsuru; Urano, Hajime; Kobayashi, Takayuki; Nakata, Motoki; Miyato, Naoaki; Kamada, Yutaka

Nuclear Fusion, 53(8), p.083022_1 - 083022_10, 2013/07

 Times Cited Count:6 Percentile:30.65(Physics, Fluids & Plasmas)

Time and special responses of electron channels and ion channels with central electron cyclotron heating (ECH) have been investigated in JT-60U positive shear H-mode and internal transport barrier (ITB) plasmas. The ion temperature reduces with ECH after the increase in the electron temperature where an increase in the ion heat transport with ECH accompanies an increase in the electron thermal transport. The core electron density decreases with ECH when the density profile is peaked before ECH injection. The counter intrinsic rotation with ECH is identified using H-mode plasmas with small torque input (BAL-NBI). The counter intrinsic rotation is generated after the increase in the electron temperature and correlates with the change in the electron temperature with ECH around the EC deposition. Time scale of the change in the toroidal rotation velocity is about 90-200 ms around the ECH deposition and the time scale is longer compared to those in $$T$$$$_{rm e}$$ and $$T$$$$_{rm i}$$.

Journal Articles

Numerical evaluation of core uncovery process in Fukushima Daiichi Nuclear Plant Unit No.1 with TRAC-BF1

Nagatake, Taku; Tamai, Hidesada; Akimoto, Hajime; Yoshida, Hiroyuki; Takase, Kazuyuki

Nihon Kikai Gakkai Dai-25-Kai Keisan Rikigaku Koenkai Rombunshu (CD-ROM), p.718 - 719, 2012/10

no abstracts in English

Journal Articles

Modifications to the edge radial electric field by angular momentum injection in JT-60U and their implication for pedestal transport

Kamiya, Kensaku; Honda, Mitsuru; Miyato, Naoaki; Urano, Hajime; Yoshida, Maiko; Sakamoto, Yoshiteru; Matsunaga, Go; Oyama, Naoyuki; Koide, Yoshihiko; Kamada, Yutaka; et al.

Nuclear Fusion, 52(11), p.114010_1 - 114010_12, 2012/10

 Times Cited Count:10 Percentile:45.75(Physics, Fluids & Plasmas)

Depending on the direction of the external tangential momentum input, substantial changes in not only toroidal but also poloidal flows for the carbon impurity ions are observed at around the $$E$$$$_{r}$$-well region. The shear in the edge $$E$$$$_{r}$$ becomes wider in the co-NBI case, while the edge $$E$$$$_{r}$$-well becomes deeper in the counter-NBI case.

Journal Articles

Core and edge toroidal rotation study in JT-60U

Yoshida, Maiko; Sakamoto, Yoshiteru; Honda, Mitsuru; Kamada, Yutaka; Takenaga, Hidenobu; Oyama, Naoyuki; Urano, Hajime; JT-60 Team

Nuclear Fusion, 52(2), p.023024_1 - 023024_9, 2012/02

 Times Cited Count:12 Percentile:52.06(Physics, Fluids & Plasmas)

Relation between the toroidal rotation velocities in the core and edge regions has been investigated in H-mode plasmas with small external torque input from the viewpoint of momentum transport. The toroidal rotation velocity in the core region gradually varies on a timescale after a rapid change in the toroidal rotation velocity in the edge region at the L-H transition. In steady state, a linear correlation between the core- and edge-rotation is observed in H-mode plasmas when the ion pressure gradient is small. The rotation profiles with a large have been reproduced in the core region by adopting a residual stress term proposed in this paper. Parameter dependencies of the edge-rotation are investigated at a constant ripple loss power, ripple amplitude and the plasma current. A reduction in the CTR-rotation is observed with decreasing the ion temperature gradient. Here CTR refers in the counter-$$I$$$$_{rm P}$$ direction.

Journal Articles

Report on ITPA (International Tokamak Physics Activity) meeting, 34

Yoshida, Maiko; Isayama, Akihiko; Urano, Hajime; Kawano, Yasunori; Hamamatsu, Kiyotaka; Hayashi, Nobuhiko

Purazuma, Kaku Yugo Gakkai-Shi, 87(12), p.849 - 852, 2011/12

Some ITPA Topical Group Meetings were held individually. We discussed international joint experiments, issues for ITER and plan for next year in each group.

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:8 Percentile:38.12(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

Core transport properties in JT-60U and JET identity plasmas

Litaudon, X.*; Sakamoto, Yoshiteru; de Vries, P. C.*; Salmi, A.*; Tala, T.*; Angioni, C.*; Benkadda, S.*; Beurskens, M. N. A.*; Bourdelle, C.*; Brix, M.*; et al.

Nuclear Fusion, 51(7), p.073020_1 - 073020_13, 2011/07

 Times Cited Count:8 Percentile:38.12(Physics, Fluids & Plasmas)

A variety of triggering mechanisms and structures of internal transport barrier (ITB) has been observed in various devices or depending on operation scenarios. Thus identity experiments on ITB in JT-60U and JET have been performed to shed light on the physics behind ITBs. Because of their similar size, the dimensionless parameters between both devices are the same. These experiments were performed with near identical magnetic configurations, heating waveforms and normalized quantities such as safety factor, magnetic shear, normalized Larmor radius, normalized collision frequency, beta, temperatures ratio. Similarities of the ITB triggering mechanism and the ITB strength have been observed when a proper match is achieved of the most relevant profiles of the normalized quantities. This paper will report on the detail comparison of transport properties of ITBs obtained in these JET/JT-60U identity experiments.

Journal Articles

Plasma regimes and research goals of JT-60SA towards ITER and DEMO

Kamada, Yutaka; Barabaschi, P.*; Ishida, Shinichi; Ide, Shunsuke; Lackner, K.*; Fujita, Takaaki; Bolzonella, T.*; Suzuki, Takahiro; Matsunaga, Go; Yoshida, Maiko; et al.

Nuclear Fusion, 51(7), p.073011_1 - 073011_11, 2011/07

 Times Cited Count:55 Percentile:92.54(Physics, Fluids & Plasmas)

Journal Articles

Strong correlation among structural, electronic, and magnetic properties of Sr$$_{2}$$Fe$$_{1+x}$$Mo$$_{1-x}$$O$$_{6}$$ (0 $$leq$$x$$leq$$ 1)

Yoshida, koji*; Ikeuchi, Shinya*; Shimizu, Hajime*; Okayasu, Satoru; Suzuki, Takashi*

Journal of the Physical Society of Japan, 80(4), p.044716_1 - 044716_4, 2011/04

 Times Cited Count:5 Percentile:41.54(Physics, Multidisciplinary)

We studied systematic changes of the structural, electric, and magnetic properties in Sr$$_{2}$$Fe$$_{1+x}$$Mo$$_{1-x}$$O$$_{6}$$ with 0 $$leq$$ x $$leq$$ 1, which bridges between a half-metallic double perovskite Sr$$_{2}$$FeMoO$$_{6}$$ (x = 0) and an antiferromagnetic metal SrFeO$$_{3}$$ (= Sr$$_{2}$$Fe$$_{2}$$O$$_{6}$$: x = 1). The lattice volume at room temperature linearly decreases with x. The decline steeply enhances around x = 0.5, which is accompanied with a symmetry change from a tetragonal to a cubic crystal structure. In the same composition, we also found changes in the electronic ground state from a metal to an insulator and in the magnetic one from ferromagnetism to paramagnetism. These results indicate the strong correlation among the crystal structure, itinerant electrons and occurrence of ferromagnetic state in the double perovskite. In addition, the value of the critical composition could reflect peculiar physical changes with x.

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

214 (Records 1-20 displayed on this page)