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Journal Articles

Self-organization of zonal flows and isotropic eddies in toroidal electron temperature gradient driven turbulence

Kawai, Chika*; Idomura, Yasuhiro; Ogawa, Yuichi*; Yamada, Hiroshi*

Physics of Plasmas, 27(8), p.082302_1 - 082302_11, 2020/08

 Times Cited Count:1 Percentile:27.66(Physics, Fluids & Plasmas)

Self-organization in the toroidal electron temperature gradient driven (ETG) turbulence is investigated based on a global gyrokinetic model in a weak magnetic shear configuration. Because of global profile effects, toroidal ETG modes with higher toroidal mode number n are excited at the outer magnetic surfaces, leading to strong linear wave dispersion. The resulting anisotropic wave turbulence boundary and the inverse energy cascade generate the self-organization of zonal flows, which is the unique mechanism in the global gyrokinetic model. The self-organization is confirmed both in the decaying turbulence initialized by random noises and in the toroidal ETG turbulence. It is also shown that the self-organization process generates zonal flows and isotropic eddies depending on a criterion parameter, which is determined by the ion to electron temperature ratio and the turbulence intensity.

Journal Articles

Computations of stress intensity factors for semi-elliptical cracks with high aspect ratios by using the tetrahedral finite element; Fully automated parametric study

Okada, Hiroshi*; Koya, Hirohito*; Kawai, Hiroshi*; Li, Y.; Osakabe, Kazuya*

Engineering Fracture Mechanics, 158, p.144 - 166, 2016/06

 Times Cited Count:12 Percentile:58.03(Mechanics)

The stress intensity factor (SIF) solutions of semi-elliptical cracks with high aspect ratios in plate and thick wall cylinder have been investigated under various assumed stress distributions. The authors have developed an automated analysis procedure to perform parametric studies on crack shapes and loading conditions. It consists of programs to perform automatic mesh generation, analysis execution including assignments of boundary conditions and SIF evaluations by virtual crack closure integral method. It was also found that SIF solutions for the thick wall cylinder and for the complex structure could be estimated by those for the flat plate.

Journal Articles

Practice for reducing contamination of controlled area under the influence of Fukushima nuclear accident

Yoshitomi, Hiroshi; Tatebe, Yosuke; Kawai, Keiichi; Kowatari, Munehiko

Progress in Nuclear Science and Technology (Internet), 4, p.81 - 84, 2014/04

The Facility of Radiation Standards of the Japan Atomic Energy Agency provides various radiation fields for calibration and testing. It is located about 120 km away from Fukushima Dai-ichi Nuclear Power Plant, and radioactive materials discharged by the Fukushima nuclear accident contaminated around the FRS, even inside the building including radiation controlled areas. One month after the accident, the maximum contamination level in the controlled areas was 3.8 Bq/cm$$^2$$. $$^{134}$$Cs, $$^{137}$$Cs, $$^{131}$$I, $$^{132}$$Te and $$^{132}$$I were detected by $$gamma$$ spectrometry using an HPGe detector. However, contamination in controlled areas under widely contaminated environment have not been discussed in detail. As for FRS, practices for reducing contamination in the controlled areas were necessary to avoid the influence of the contamination to the calibration works. These practices described that the following two approaches were effective: (1) decontamination of the controlled areas by wiping out with wet cloth or steam cleaners, and (2) to prevent the dust with radioactive materials from letting in the controlled areas. As a result, surface contaminates inside the controlled areas were reduced to be dozens of times lower as compared with outside.

Journal Articles

Huge upper critical field in the superconductor with non-centrosymmetric crystal structure CeCoGe$$_3$$

M$'e$asson, M.-A.*; Muranaka, Hiroshi*; Matsuda, Tatsuma; Kawai, Tomoya*; Haga, Yoshinori; Knebel, G.*; Aoki, Dai*; Lapertot, G.*; Honda, Fuminori*; Settai, Rikio*; et al.

Physica C, 470(Suppl.1), p.S536 - S538, 2010/12

 Times Cited Count:4 Percentile:23.57(Physics, Applied)

Journal Articles

Measurements of time-dependent stress distribution on material after HP impact

Kawai, Masayoshi*; Futakawa, Masatoshi; Naoe, Takashi; Xu, C.-N.*; Yamada, Hiroshi*

Proceedings of 7th International Symposium on Impact Engineering (ISIE 2010) (CD-ROM), p.380 - 385, 2010/07

We have proposed a sophisticated novel method of the SHB experiment to measure the time-dependent local strain distributions on a surface of the specimen by using mechanoluminescent materials combined with a high-speed camera and an image intensifier. The feasibility study was made for the aluminum specimens pasted with a typical mechanoluminescent material -Eu doped SrAl$$_2$$O$$_4$$ film, in order to obtain the fundamental data for the method. Our results showed that SrAl$$_2$$O$$_4$$: Eu emitted lights as a response to the strain. Rise up of the light intensity was swift enough to follow the strain change due to HP impact. The luminescence intensity was experimentally verified and expressed as product of strain and strain rate. Accordingly, it can be said that this method gives a good tool for measuring time variation of local strain distributions.

Journal Articles

Performance evaluation of structural analysis solver for many RHS problem on multicore processor

Yamada, Tomonori; Kawai, Hiroshi*

Keisan Kogaku Koenkai Rombunshu, 15(1), p.179 - 180, 2010/05

In this study, computational performance of iterative solver of large linear equations with many right hand side vectors derived from finite element discretization in structural mechanics is evaluated. The current multicore architecture has memory wall problem and many iterative solvers suffer for this problem. Hence, high performance computing with iterative solver on multicore architecture is one of key issues in recent computer science. Because the performance of sparse matrix single vector multiplication has well surveyed, the performance of sparse matrix multiple vectors multiplication is investigated in this paper.

Journal Articles

Experimental observation of bulk band dispersions in the oxide semiconductor ZnO using soft X-ray angle-resolved photoemission spectroscopy

Kobayashi, Masaki*; Song, G.-S.*; Kataoka, Takashi*; Sakamoto, Yuta*; Fujimori, Atsushi; Okochi, Takuo*; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Yamagami, Hiroshi; et al.

Journal of Applied Physics, 105(12), p.122403_1 - 122403_4, 2009/06

BB2009-1947.pdf:0.84MB

 Times Cited Count:11 Percentile:44.86(Physics, Applied)

Journal Articles

Magnetic and superconducting properties of CeTX$$_3$$ (T:transition metal and X:Si and Ge) with non-centrosymmetric crystal structure

Kawai, Tomoya*; Muranaka, Hiroshi*; M$'e$asson, M.-A.*; Shimoda, Tetsuya*; Doi, Yusuke*; Matsuda, Tatsuma; Haga, Yoshinori; Knebel, G.*; Lapertot, G.*; Aoki, Dai*; et al.

Journal of the Physical Society of Japan, 77(6), p.064716_1 - 064716_9, 2008/06

 Times Cited Count:60 Percentile:89.2(Physics, Multidisciplinary)

Physical properties of cerium compounds CeTX$$_3$$ were studied on single crystals. Electrical resistivity, magnetization as well as their pressure dependence revealed that the antiferromagnetism of CeCoGe$$_3$$ is destroyed under hydrostatic pressure above 5.4 GPa and the superconductivity appears above this pressure.

Journal Articles

Split Fermi surface properties of LaTGe$$_3$$ (T:transition metal) and PrCoGe$$_3$$ with the non-centrosymmetric crystal structure

Kawai, Tomoya*; Muranaka, Hiroshi*; Endo, Toyoaki*; Nguyen, D.; Doi, Yusuke*; Ikeda, Shugo*; Matsuda, Tatsuma; Haga, Yoshinori; Harima, Hisatomo*; Settai, Rikio*; et al.

Journal of the Physical Society of Japan, 77(6), p.064717_1 - 064717_15, 2008/06

 Times Cited Count:39 Percentile:83.54(Physics, Multidisciplinary)

Fermi surfaces of the non-centrosymmetric LaTGe$$_3$$ and PrCoGe$$_3$$ have been studied in detail using the de Haas-van Alphen effect. Splitting of the conduction bands due to the spin-orbit interaction was clearly observed. These results are important in understanding the exotic superconductivity realized in non-centrosymmetric structure.

Journal Articles

Photoemission and X-ray absorption studies of valence states in (Ni,Zn,Fe,Ti)$$_3$$O$$_4$$ thin films exhibiting photoinduced magnetization

Kobayashi, Masaki*; Oki, Yasuhiro*; Takizawa, Masaru*; Song, G. S.*; Fujimori, Atsushi; Takeda, Yukiharu; Terai, Kota*; Okane, Tetsuo; Fujimori, Shinichi; Saito, Yuji; et al.

Applied Physics Letters, 92(8), p.082502_1 - 082502_3, 2008/02

 Times Cited Count:12 Percentile:46.79(Physics, Applied)

Journal Articles

Technical design of NBI system for JT-60SA

Ikeda, Yoshitaka; Akino, Noboru; Ebisawa, Noboru; Hanada, Masaya; Inoue, Takashi; Honda, Atsushi; Kamada, Masaki; Kawai, Mikito; Kazawa, Minoru; Kikuchi, Katsumi; et al.

Fusion Engineering and Design, 82(5-14), p.791 - 797, 2007/10

 Times Cited Count:19 Percentile:79.3(Nuclear Science & Technology)

Modification of JT-60U to a superconducting device (so called JT-60SA) has been planned to contribute to ITER and DEMO. The NBI system is required to inject 34 MW for 100 s. The upgraded NBI system consists of twelve positive ion based NBI (P-NBI) units and one negative ion based NBI (N-NBI) unit. The injection power of the P-NBI units are 2 MW each at 85 keV, and the N-NBI unit will be 10 MW at 500 keV, respectively. On JT-60U, the long pulse operation of 30 s at 2 MW (85 keV) and 20 s at 3.2 MW (320 keV) have been achieved on P-NBI and N-NBI units, respectively. Since the temperature increase of the cooling water in both ion sources is saturated within 20 s, further pulse extension up to 100 s is expected to mainly modify the power supply systems in addition to modification of the N-NBI ion source for high acceleration voltage. The detailed technical design of the NBI system for JT-60SA is presented.

Journal Articles

Current status of the AGS spallation target experiment

Nakashima, Hiroshi; Takada, Hiroshi; Kasugai, Yoshimi; Meigo, Shinichiro; Maekawa, Fujio; Kai, Tetsuya; Konno, Chikara; Ikeda, Yujiro; Oyama, Yukio; Watanabe, Noboru; et al.

Proceedings of 6th Meeting of the Task Force on Shielding Aspects of Accelerators, Targets and Irradiation Facilities (SATIF-6), (OECD/NEA No.3828), p.27 - 36, 2004/00

no abstracts in English

Journal Articles

Operation and develoment on the positive-ion based neutral beam injection system for JT-60 and JT-60U

Kuriyama, Masaaki; Akino, Noboru; Ebisawa, Noboru; Honda, Atsushi; Ito, Takao; Kawai, Mikito; Mogaki, Kazuhiko; Oga, Tokumichi; Ohara, Hiroshi; Umeda, Naotaka; et al.

Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.424 - 434, 2002/09

 Times Cited Count:15 Percentile:69.46(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Operation and development on the 500-keV negative-ion-based neutral beam injection system for JT-60U

Kuriyama, Masaaki; Akino, Noboru; Ebisawa, Noboru; Grisham, L. R.*; Honda, Atsushi; Ito, Takao; Kawai, Mikito; Kazawa, Minoru; Mogaki, Kazuhiko; Ohara, Yoshihiro; et al.

Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.410 - 423, 2002/09

 Times Cited Count:48 Percentile:93.88(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Research activities on neutronics under ASTE collaboration at AGS/BNL

Nakashima, Hiroshi; Takada, Hiroshi; Kasugai, Yoshimi; Meigo, Shinichiro; Maekawa, Fujio; Kai, Tetsuya; Konno, Chikara; Ikeda, Yujiro; Oyama, Yukio; Watanabe, Noboru; et al.

Journal of Nuclear Science and Technology, 39(Suppl.2), p.1155 - 1160, 2002/08

no abstracts in English

JAEA Reports

Dose coefficients for radionuclides produced in high energy proton accelerator facilities; Coefficients for radionuclides not listed in ICRP publications

Kawai, Katsuo; Endo, Akira; Noguchi, Hiroshi

JAERI-Data/Code 2002-013, 66 Pages, 2002/05

JAERI-Data-Code-2002-013.pdf:2.75MB
JAERI-Data-Code-2002-013-DoseCD.pdf:81.85MB

Effective dose coefficients by inhalation and ingestion have been calculated for 334 nuclides, including (1) nuclides with half-lives $$ge$$ 10min and their daughters that are not listed in ICRP Publications and (2) nuclides with half-lives $$<$$ 10min that are produced in a spallation target. Dose calculation was carried out using a nuclear decay database DECDC and a decay data library newly compiled from the ENSDF. The dose coefficients were calculated with the computer code DOCAP based on the respiratory tract model and biokinetic model of ICRP. The calculated results are presented as tables, which are the same forms as those in ICRP Publs.68 and 72. The complete listings of the dose coefficients are arranged on a CD-ROM, DoseCD, as indexed tables for inhalation of ten particle sizes, ingestion and injection into blood for workers and members of the public. The dose coefficients calculated in the present study are useful to calculate internal doses for a variety of radionuclides produced in high energy proton accelerator facilities.

Journal Articles

Present status of the negative ion based neutral beam injector for JT-60U

Oga, Tokumichi; Umeda, Naotaka; Akino, Noboru; Ebisawa, Noboru; Grisham, L. R.*; Hikida, Shigenori*; Honda, Atsushi; Ito, Takao; Kawai, Mikito; Kazawa, Minoru; et al.

Review of Scientific Instruments, 73(2), p.1058 - 1060, 2002/02

 Times Cited Count:12 Percentile:56.93(Instruments & Instrumentation)

no abstracts in English

JAEA Reports

Construction of negative-ion based NBI for JT-60U

Kawai, Mikito; Akino, Noboru; Ebisawa, Noboru; Honda, Atsushi; Ito, Takao; Kazawa, Minoru; Kuriyama, Masaaki; Mogaki, Kazuhiko; Oga, Tokumichi; Ohara, Hiroshi; et al.

JAERI-Tech 2001-073, 98 Pages, 2001/11

JAERI-Tech-2001-073.pdf:4.65MB

The world's first negative-ion based neutral beam injector(N-NBI) system has been developed for studies of non-inductive current drive and plasma core heating with high energy neutral beam injection in higher density plasma. Construction of the N-NBI system for JT-60U was completed in March 1996. The system is composed of a beamline with two ion souces, a set of ion source power supllies, control system and auxiliary sub-system such as cooling water, refrigeration and vaccum system. In July 2001, deuterium neutral beam injection of 400keV and 5.8MW into JT-60U plasma was achieved. In order to increase both beam power and energy we have to go on more improvement of the N-NBI.

Journal Articles

Study of increasing the beam power on the negative ion based neutral beam injector for JT-60U

Kuriyama, Masaaki; Akino, Noboru; Ebisawa, Noboru; Grisham, L. R.*; Hikida, Shigenori*; Honda, Atsushi; Ito, Takao; Kawai, Mikito; Kazawa, Minoru; Kusaka, Makoto*; et al.

Fusion Engineering and Design, 56-57(Part.A), p.523 - 527, 2001/10

 Times Cited Count:5 Percentile:40.34(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Development of negative ion based NBI system for JT-60U

Umeda, Naotaka; Akino, Noboru; Ebisawa, Noboru; Grisham, L. R.*; Hikida, Shigenori*; Honda, Atsushi; Ito, Takao; Kawai, Mikito; Kazawa, Minoru; Kusaka, Makoto*; et al.

Fusion Technology, 39(2-Part2), p.1135 - 1139, 2001/03

no abstracts in English

63 (Records 1-20 displayed on this page)