Refine your search:     
Report No.
 - 
Search Results: Records 1-20 displayed on this page of 336

Presentation/Publication Type

Initialising ...

Refine

Journal/Book Title

Initialising ...

Meeting title

Initialising ...

First Author

Initialising ...

Keyword

Initialising ...

Language

Initialising ...

Publication Year

Initialising ...

Held year of conference

Initialising ...

Save select records

Journal Articles

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

 Times Cited Count:86 Percentile:0.14(Multidisciplinary Sciences)

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

Journal Articles

Electric resistance measurement of silicon carbide resistors

Suganuma, Kazuaki; Shimoyama, Nobuyoshi*; Yonekyu, Naoyuki*; Taki, Yukina*; Kinsho, Michikazu

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.686 - 688, 2015/09

no abstracts in English

Journal Articles

Integrated simulation study of ELM pacing by pellet injection in ITER

Hayashi, Nobuhiko; Aiba, Nobuyuki; Takizuka, Tomonori*; Oyama, Naoyuki

Contributions to Plasma Physics, 54(4-6), p.599 - 604, 2014/06

 Times Cited Count:0 Percentile:100(Physics, Fluids & Plasmas)

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

Reduction of ELM energy loss by pellet injection for ELM pacing

Hayashi, Nobuhiko; Aiba, Nobuyuki; Takizuka, Tomonori*; Oyama, Naoyuki

Nuclear Fusion, 53(12), p.123009_1 - 123009_10, 2013/12

 Times Cited Count:5 Percentile:71.64(Physics, Fluids & Plasmas)

Journal Articles

Hydrogen isotope effects on ITG scale length, pedestal and confinement in JT-60 H-mode plasmas

Urano, Hajime; Takizuka, Tomonori*; Aiba, Nobuyuki; Kikuchi, Mitsuru; Nakano, Tomohide; Fujita, Takaaki; Oyama, Naoyuki; Kamada, Yutaka; Hayashi, Nobuhiko; JT-60 Team

Nuclear Fusion, 53(8), p.083003_1 - 083003_8, 2013/08

 Times Cited Count:21 Percentile:22(Physics, Fluids & Plasmas)

Dependence of heat transport, edge pedestal and confinement on isotopic composition was investigated in conventional H-mode plasmas. Identical profiles for the electron density, electron temperature, and ion temperature were obtained for hydrogen and deuterium plasmas, whereas the required power clearly increased for hydrogen, which resulted in reduction of heat diffusivity for deuterium. The inverse of the ion-temperature-gradient (ITG) scale length which is required for a given ion heat diffusivity increased by a factor of approximately 1.2 for deuterium compared with that for hydrogen.

Journal Articles

ELM triggering by energetic particle driven mode in wall-stabilized high-$$beta$$ plasmas

Matsunaga, Go; Aiba, Nobuyuki; Shinohara, Koji; Asakura, Nobuyuki; Isayama, Akihiko; Oyama, Naoyuki; JT-60 Team

Nuclear Fusion, 53(7), p.073046_1 - 073046_9, 2013/06

 Times Cited Count:2 Percentile:88.58(Physics, Fluids & Plasmas)

Journal Articles

Report of International Tokamak Physics Activity meeting, 40

Isayama, Akihiko; Asakura, Nobuyuki; Hayashi, Nobuhiko; Shinohara, Koji; Honda, Mitsuru; Oyama, Naoyuki

Purazuma, Kaku Yugo Gakkai-Shi, 89(6), p.430 - 433, 2013/06

no abstracts in English

Journal Articles

Resonant magnetic perturbation for ELM suppression with helical ferritic steel inserts in tokamak DEMO reactor

Takizuka, Tomonori*; Oyama, Naoyuki; Fukuda, Takeshi*

Fusion Science and Technology, 63(1T), p.64 - 69, 2013/05

 Times Cited Count:1 Percentile:86.75(Nuclear Science & Technology)

Edge localized mode (ELM) must be eliminated which enhances the erosion of divertor plates in the H-mode operation of tokamak reactors. Suppression of ELM has been experimentally achieved by the resonant magnetic perturbation (RMP) with multipartite coils. In a DEMO reactor with strong neutron flux, however, it is desired the coils near the first wall not to be put in. We propose an innovative concept of the RMP for tokamak DEMO reactors without installing coils but inserting ferritic steels of the helical configuration. Helically perturbed magnetic field is naturally formed in the axisymmetric toroidal magnetic field through the helical ferritic steel inserts (FSIs). The perturbation amplitude in the plasma pedestal region can easily be set above several 10$$^{-4}$$ of the toroidal field strength in the DEMO reactor condition, which is enough for the RMP to suppress ELM.

Journal Articles

A View of technology maturity assessment to realize fusion reactor by Japanese young researchers

Kasada, Ryuta*; Goto, Takuya*; Fujioka, Shinsuke*; Hiwatari, Ryoji*; Oyama, Naoyuki; Tanigawa, Hiroyasu; Miyazawa, Junichi*; Young Scientists Special Interest Group on Fusion Reactor Realization*

Purazuma, Kaku Yugo Gakkai-Shi, 89(4), p.193 - 198, 2013/04

Japanese young researchers who have interest in realizing fusion reactor have analyzed Technology Readiness Levels (TRL) in Young Scientists Special Interest Group on Fusion Reactor Realization. In this report, brief introduction to TRL assessment and a view of TRL assessment against fusion reactor projects conducting in Japan.

Journal Articles

Reduction of ELM energy loss by pellet injection for ELM pacing

Hayashi, Nobuhiko; Aiba, Nobuyuki; Takizuka, Tomonori*; Oyama, Naoyuki

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/03

Journal Articles

Dependence of heat transport and confinement on isotopic composition in conventional H-mode plasmas in JT-60U

Urano, Hajime; Takizuka, Tomonori*; Kikuchi, Mitsuru; Nakano, Tomohide; Fujita, Takaaki; Oyama, Naoyuki; Kamada, Yutaka; Hayashi, Nobuhiko; JT-60 Team

Proceedings of 24th IAEA Fusion Energy Conference (FEC 2012) (CD-ROM), 8 Pages, 2013/01

Dependence of heat transport on isotopic composition is investigated in conventional H-mode plasmas for the application to ITER. The identical profiles of $$n_mathrm{e}$$, $$T_mathrm{e}$$ and $$T_mathrm{i}$$ are obtained for hydrogen and deuterium plasmas while the required power becomes clearly larger for hydrogen, resulting in the reduction of the heat diffusivity for deuterium. The result of the identical temperature profiles in spite of different heating power suggests that the characteristics of heat conduction differs essentially between hydrogen and deuterium even at the same scale length of temperature gradient. On the other hand, the edge stability is improved by increased total $$beta_mathrm{p}$$ regardless of the difference of the isotropic composition.

Journal Articles

Effects of local toroidal field ripple due to test blanket modules for ITER on radial transport of thermal ions

Oyama, Naoyuki; Urano, Hajime; Shinohara, Koji; Honda, Mitsuru; Takizuka, Tomonori; Hayashi, Nobuhiko; Kamada, Yutaka; JT-60 Team

Nuclear Fusion, 52(11), p.114013_1 - 114013_9, 2012/11

 Times Cited Count:4 Percentile:78.04(Physics, Fluids & Plasmas)

Effects of local toroidal field (TF) ripple due to test blanket modules (TBMs) for ITER on radial transport of thermal ions are investigated using fully three-dimensional magnetic field orbit following Monte Carlo (F3D-OFMC) code. The simulation under ITER plasma condition indicates that the additional losses caused by the localized TF ripple due to TBMs linearly increase with number of TBMs. When the amplitude of local TF ripple in one TBM port is increased, on the other hand, the additional losses increase quickly. A comparison of the number of lost particles suggests that a condition with three TBM ports corresponds to 1.7 times of ripple amplitude at one TBM port.

Journal Articles

Numerical analysis of key factors for the appearance of grassy ELMs in tokamak plasmas

Aiba, Nobuyuki; Oyama, Naoyuki

Nuclear Fusion, 52(11), p.114002_1 - 114002_8, 2012/11

 Times Cited Count:12 Percentile:44.88(Physics, Fluids & Plasmas)

In this paper, we developed a simplified model that is used for the MHD stability analysis with the kinetic effects, and applied this to the numerical analysis of small amplitude ELM, called grassy ELM. As the result, we found that the stabilizing effect due to the ion diamagnetic drift can be canceled by taking into account the plasma compressibility and the electron diamagnetic drift, and this cancelation moves the stability boundary of small ELM closer to the ideal ballooning stability boundary. This trend is consistent with the experimental results of JT-60U grassy ELM plasma, and implies that the short-wavelength electromagnetic instability like ideal ballooning mode is thought as the origin of grassy ELM.

Journal Articles

Energy confinement of hydrogen and deuterium H-mode plasmas in JT-60U

Urano, Hajime; Takizuka, Tomonori*; Fujita, Takaaki; Kamada, Yutaka; Nakano, Tomohide; Oyama, Naoyuki; JT-60 Team

Nuclear Fusion, 52(11), p.114021_1 - 114021_10, 2012/11

 Times Cited Count:14 Percentile:39.2(Physics, Fluids & Plasmas)

Energy confinement properties for hydrogen and deuterium H-mode plasmas are investigated. The stored energy for deuterium becomes larger approximately by a factor of 1.7-2.0 than that for hydrogen at a given heating power. When the stored energy is fixed for both cases, the required power differs roughly a factor of $$sim1.7$$ and the identical spatial profiles of electron density $$n_mathrm{e}$$, electron temperature $$T_mathrm{e}$$ and ion temperature $$T_mathrm{i}$$ are obtained. Despite almost the same power crossing the separatrix, type-I ELM frequency for hydrogen becomes approximately in double from that for deuterium. The pedestal pressure differs approximately by a factor of $$sim2$$ for the cases between hydrogen and deuterium plasmas at a given absorbed power. The relation between $$beta_mathrm{p}^mathrm{TOT}$$ and $$beta_mathrm{p}^mathrm{ped}$$ is almost identical regardless of the difference of the isotropic composition.

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:9 Percentile:55.33(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

The Unified effect of counter-toroidal rotation and power across separatrix on type-I ELMs in JT-60U

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:88.95(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 $$f_mathrm{ELM}$$ increased monotonically together with the power across the sepratrix $$P_mathrm{sep}$$ for all the cases of tangential NBs. However, dependence of $$f_mathrm{ELM}$$ on $$P_mathrm{sep}$$ was explicitly stronger than a proportional relation when the perpendicular NBs were injected. The toroidal rotation velocity at the H-mode pedestal $$V$$$$rm_T^{rm PED}$$ shifted continuously in counter direction when the perpendicular NBs were applied. At fixed values of $$V$$$$rm_T^{rm PED}$$, $$f_mathrm{ELM}$$ increased clearly in proportion to $$P_mathrm{sep}$$.

Journal Articles

Small ion-temperature-gradient scale length and reduced heat diffusivity at large hydrogen isotope mass in conventional $$H$$-mode plasmas

Urano, Hajime; Takizuka, Tomonori*; Kikuchi, Mitsuru; Nakano, Tomohide; Hayashi, Nobuhiko; Oyama, Naoyuki; Kamada, Yutaka

Physical Review Letters, 109(12), p.125001_1 - 125001_5, 2012/09

 Times Cited Count:19 Percentile:25.9(Physics, Multidisciplinary)

The dependence of the ion temperature gradient scale length on the hydrogen isotope mass was examined in conventional $$H$$-mode plasmas in JT-60U tokamak. While identical profiles for density and temperature were obtained for hydrogen and deuterium plasmas, the ion conductive heat flux necessary for hydrogen to sustain the same thermal stored energy was two times that required for deuterium, resulting in a clearly higher ion heat diffusivity for hydrogen at the same ion temperature gradient scale length. The ion temperature gradient scale length for deuterium is less than that for hydrogen at a given ion heat diffusivity.

Journal Articles

Report on ITPA (International Tokamak Physics Activity) meeting, 36

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

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:9 Percentile:55.33(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.

336 (Records 1-20 displayed on this page)