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Kobayashi, Tatsuya*; Ito, Kimitaka*; Ido, Takeshi*; Kamiya, Kensaku*; Ito, Sanae*; Miura, Yukitoshi; Nagashima, Yoshihiko*; Fujisawa, Akihide*; Inagaki, Shigeru*; Ida, Katsumi*
Scientific Reports (Internet), 7(1), p.14971_1 - 14971_8, 2017/11
Times Cited Count：20 Percentile：81.1(Multidisciplinary Sciences)Kobayashi, Tatsuya*; Ito, Kimitaka*; Ido, Takeshi*; Kamiya, Kensaku; Ito, Sanae*; Miura, Yukitoshi; Nagashima, Yoshihiko*; Fujisawa, Akihide*; Inagaki, Shigeru*; Ida, Katsumi*; et al.
Scientific Reports (Internet), 6, p.30720_1 - 30720_7, 2016/08
Times Cited Count：13 Percentile：67.28(Multidisciplinary Sciences)In this Letter, we report model verifications for a key physics for the L-H transition. Radial electric field excitation, using discharges having a two-step transition. Examining time derivative of Poissons equation, it is found that the sum of the loss cone loss current and neoclassical bulk viscosity current agrees the experimentally observed current in the order of magnitude at the first transition. Following second transition and an ambipolar condition in the L-mode cannot be explained by the models.
Urano, Hajime; Aiba, Nobuyuki; Kamiya, Kensaku; Kamada, Yutaka; JT-60 Team
Nuclear Fusion, 56(1), p.016005_1 - 016005_8, 2016/01
Times Cited Count：6 Percentile：36.16(Physics, Fluids & Plasmas)Dependence of pedestal structure on collisionality at fixed beta has been investigated in JT-60U. In the ITER-relevant low collisionality regime, the pedestal width does not change with edge collisionality. In the high collisionality regime, the pedestal width broadens with increased edge collisionality. The pedestal pressure gradient and width are not significantly changed when the pedestal is close to an intermediate 
peeling-ballooning mode boundary at low collisionality. The experimental result indicates that conventional pedestal models where the pedestal width is independent of collisionality and is determined by 
at the pedestal is not a bad assumption in the ITER-relevant low collisionality regime. On the other hand, the pressure gradient decreases and the pedestal width increases at high collisionality. The pedestal broadening becomes significant when the pedestal is marginal to be unstable at high ballooning mode in high collisionality regime.
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：25.88(Physics, Fluids & Plasmas)Ito, Kimitaka*; Ito, Sanae*; Kamiya, Kensaku; Kasuya, Naohiro*
Plasma Physics and Controlled Fusion, 57(7), p.075008_1 - 075008_7, 2015/07
Times Cited Count：19 Percentile：72.07(Physics, Fluids & Plasmas)The solitary radial electric field in the edge of toroidal plasma is studied based on the electric field bifurcation model. Results are applied to tokamak and helical plasmas, and the dependence of the electric field structure on the plasma parameters and geometrical factors is analyzed. The order of magnitude estimate for tokamak plasma is not far from experimental observations. It is shown that, in helical plasmas, the height of electric field structure is reduced substantially owing to the ripple particle transport, while the width is influenced less. The implications of the results for the limit of achievable gradient in the H-mode pedestal are also discussed.
Urano, Hajime; Aiba, Nobuyuki; Kamiya, Kensaku; Kamada, Yutaka; JT-60 Team
Europhysics Conference Abstracts (Internet), 39E, p.P5.146_1 - P5.146_4, 2015/06
no abstracts in English
Kamiya, Kensaku; Itami, Kiyoshi; Takeuchi, Masaki; Enokuchi, Akito*
Fusion Engineering and Design, 89(12), p.3089 - 3094, 2014/12
Times Cited Count：2 Percentile：17.55(Nuclear Science & Technology)Design study of a wide-angle infrared (IR) thermography and visible observation diagnostics for JT-60SA are reported. In order to image a large section inside the vacuum vessel (both in poloidal and toroidal directions), the optical system of endoscope is to provide a wide-angle view in the IR and visible range, which is being designed with a field of view of 106 degrees vertical and 63 degrees horizontal. The estimated spatial resolution is better than a few cm at a distance of 7.6 m from the front optics with a slit diameter of 4 mm.
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：57.12(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.
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
Kobayashi, Tatsuya*; Ito, Kimitaka*; Ido, Takeshi*; Kamiya, Kensaku; Ito, Sanae*; Miura, Yukitoshi; Nagashima, Yoshihiko*; Fujisawa, Akihide*; Inagaki, Shigeru*; Ida, Katsumi*; et al.
Nuclear Fusion, 54(7), p.073017_1 - 073017_14, 2014/07
Times Cited Count：26 Percentile：79.9(Physics, Fluids & Plasmas)In the JFT-2M tokamak, limit-cycle oscillation among several variables is observed before L-to-H transition. Spatiotemporal dynamics of the LCO is analyzed in detail. Zonal fows are not seen, and modulation in edge-localized poloidal flow and density gradient is observed. Modulation is also seen in Reynolds stress, caused by that in turbulence intensity and turbulence wavenumber. However, flow acceleration is not able to be explained by the modulation in the Reynolds stress. Rapid inward propagation in density gradient and turbulence packet is also observed. Characteristics of the propagation are veried by means of turbulence spreading theory and diffusion theory.
Kamiya, Kensaku; Matsunaga, Go; Honda, Mitsuru; Miyato, Naoaki; Urano, Hajime; Kamada, Yutaka; Ida, Katsumi*; Ito, Kimitaka*; JT-60 Team
Contributions to Plasma Physics, 54(4-6), p.591 - 598, 2014/06
Times Cited Count：6 Percentile：31.83(Physics, Fluids & Plasmas)no abstracts in English
Yoshida, Maiko; Shinohara, Koji; Hayashi, Nobuhiko; Isayama, Akihiko; Kamiya, Kensaku
Purazuma, Kaku Yugo Gakkai-Shi, 89(12), p.887 - 889, 2013/12
ITPA (International Tokamak Physics Activity) meetings were held in Autumn 2013.
Kobayashi, Tatsuya*; Ito, Kimitaka*; Ido, Takeshi*; Kamiya, Kensaku; Ito, Sanae*; Miura, Yukitoshi; Nagashima, Yoshihiko*; Fujisawa, Akihide*; Inagaki, Shigeru*; Ida, Katsumi*; et al.
Physical Review Letters, 111(3), p.035002_1 - 035002_5, 2013/07
Times Cited Count：90 Percentile：94.52(Physics, Multidisciplinary)In this Letter, we report analyses of spatiotemporal dynamics of turbulence and structure in the limit cycle oscillation that precedes L-to-H transition. Zonal flows are not observed during LCO, and the oscillation is the periodic generations/decays of barrier with edge localized mean flow. Oscillatory Reynolds stress is found too small to accelerate the LCO flow. Changes of the density gradient and turbulence amplitude are found to propagate into the core in a ballistic manner, suggesting a cause of fast change of core transport after H-mode transition.
Ida, Katsumi; Kamiya, Kensaku; Suzuki, Yasuhiro*
Purazuma, Kaku Yugo Gakkai-Shi, 89(5), p.319 - 327, 2013/05
This paper provides and proposes a new technique to determine the location of the LCFS that is based on a characterization of the Er structure derived from CXS measurements in the LHD. We found that the spatial derivative in the Er structure had the local maximum value at the region very near, or possibly outside the vacuum LCFS location of vacuum magnetic field at the outer midplane in the low beta plasma.
Kamiya, Kensaku; Ida, Katsumi*; Yoshinuma, Mikiro*; Suzuki, Chihiro*; Suzuki, Yasuhiro*; Yokoyama, Masayuki*; LHD Experimental Group*
Nuclear Fusion, 53(1), p.013003_1 - 013003_9, 2013/01
Times Cited Count：17 Percentile：62.8(Physics, Fluids & Plasmas)This paper provides and proposes a new technique to determine the location of the LCFS that is based on a characterization of the 
structure derived from CXS measurements in the LHD. We found that the spatial derivative in the structure had the local maximum value at the region very near, or possibly outside the vacuum LCFS location of vacuum magnetic field at the outer midplane in the low 
plasma.
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：42.62(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 -well region. The shear in the edge becomes wider in the co-NBI case, while the edge -well becomes deeper in the counter-NBI case.
Urano, Hajime; Oyama, Naoyuki; Kamiya, Kensaku; Aiba, Nobuyuki; Kamada, Yutaka; Fujita, Takaaki; JT-60 Team
Nuclear Fusion, 52(10), p.103012_1 - 103012_7, 2012/10
Times Cited Count：2 Percentile：9.42(Physics, Fluids & Plasmas)The unified effect of counter toroidal rotation and heating power on type-I ELMs was investigated in JT-60U tokamak. ELM frequency 
increased monotonically together with the power across the sepratrix 
for all the cases of tangential NBs. However, dependence of on was explicitly stronger than a proportional relation when the perpendicular NBs were injected. The toroidal rotation velocity at the H-mode pedestal 
shifted continuously in counter direction when the perpendicular NBs were applied. At fixed values of , increased clearly in proportion to .
Ida, Katsumi*; Kamiya, Kensaku; Isayama, Akihiko; Sakamoto, Yoshiteru; JT-60 Team
Physical Review Letters, 109(6), p.065001_1 - 065001_4, 2012/08
Times Cited Count：42 Percentile：84.97(Physics, Multidisciplinary)The transport inside the magnetic island is investigated in the plasma during the transient phase after the back transition from 
-mode to 
-mode, where a sudden drop of temperature outside the magnetic island causes a peaking of ion temperature at the 
-point inside the magnetic island.
Oyama, Naoyuki; Shinohara, Koji; Isayama, Akihiko; Yoshida, Maiko; Kamiya, Kensaku
Purazuma, Kaku Yugo Gakkai-Shi, 88(5), p.282 - 285, 2012/05
no abstracts in English
Matsunaga, Go; Kamiya, Kensaku; Shinohara, Koji; Miyato, Naoaki; Kojima, Atsushi; Bierwage, A.; JT-60 Team
Europhysics Conference Abstracts (Internet), 36F, p.P2.062_1 - P2.062_4, 2012/00
