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Shimizu, Hirotaka*; Kosugi, Shinya*; Tahara, Yuki*; Yasunaga, Kazufumi*; Kaneta, Yasunori*; Ishikawa, Norito; Hori, Fuminobu*; Matsui, Toshiyuki*; Iwase, Akihiro*
Nuclear Instruments and Methods in Physics Research B, 286, p.291 - 294, 2012/09
Times Cited Count：27 Percentile：87.4(Instruments & Instrumentation)We have studied the magnetic properties of pure CeO irradiated with swift heavy ions. Experiment a results showed that the ferromagnetism was induced even at room temperature by 200 MeV Xe ion irradiation. The value of saturation magnetization, Ms, systematically changes as a function of ion-fluence. The X-ray diffraction (XRD) spectra show that the lattice constant of CeO increases with increasing ion-fluence. This result and our previous XPS result show that the ion-irradiation produced oxygen vacancies. The present study implies that the ferromagnetic behavior of the ion-irradiated CeO is attributed to the magnetic moments of localized 4f electrons on Ce
atoms, which are related to oxygen vacancies.
O
-doped CeO by means of synchrotron radiation X-ray spectroscopyTahara, Yuki*; Shimizu, Hirotaka*; Ishikawa, Norito; Okamoto, Yoshihiro; Hori, Fuminobu*; Matsui, Toshiyuki*; Iwase, Akihiro*
Nuclear Instruments and Methods in Physics Research B, 277, p.53 - 57, 2012/04
In this study, to simulate such an environment, GdO-doped CeO samples were irradiated with 200 MeV Xe
ions at room temperature using an ion beam accelerator at JAEA-Tokai. As CeO has the same fluorite structure as that of UO and several properties of CeO are similar to UO, in this study CeO was used as a simulation material of UO. To study the effects of the ion irradiation on GdO-doped CeO, extended X-ray absorption fine structure (EXAFS) and X-ray photoelectron spectroscopy (XPS) were used at the Photon Factory of High Energy Accelerator Research Organization (KEK) as well as conventional X-ray diffraction (XRD) measurement. The EXAFS and XRD spectra show that the effects of the ion irradiation are more pronounced for higher amount of GdO dopant.
O
-doped CeO by means of synchrotron radiation X-ray spectroscopyTahara, Yuki*; Shimizu, Hirotaka*; Ishikawa, Norito; Okamoto, Yoshihiro; Hori, Fuminobu*; Matsui, Toshiyuki*; Iwase, Akihiro*
Nuclear Instruments and Methods in Physics Research B, 277, p.53 - 57, 2012/04
Times Cited Count：11 Percentile：63.23(Instruments & Instrumentation)To study the effects of GdO-doping and the irradiation with high energy fission products in the nuclear fuels (UO), GdO-doped CeO pellets were irradiated with 200 MeV Xe ions. Effects of GdO-doping and the ion irradiation were estimated by using Extended X-ray Absorption Fine Structure (EXAFS) measurement. The interatomic distances between each Ce and the first nearest O atoms, and Ce and the second nearest Ce atoms increase by the irradiation and the effect of the ion irradiation on the atomic distances is more pronounced for higher amounts of dopant. The Debye-Waller factors for Ce-O and Ce-Ce pairs increase with increasing the amount of GdO dopant. These results suggest that the lattice binding energy is weakened by GdO-doping. The Debye-Waller factors increase also by the irradiation. The effect of ion irradiation on the Debye-Waller factors, however, becomes smaller for higher amounts of dopant.
Kosugi, Shinya*; Matsui, Toshiyuki*; Ishikawa, Norito; Ito, Masayoshi*; Sakurai, Yoshiharu*; Aiko, Kazuma*; Shimizu, Hirotaka*; Tahara, Yuki*; Hori, Fuminobu*; Iwase, Akihiro*
Journal of Applied Physics, 109(7), p.07B737_1 - 07B737_3, 2011/04
Times Cited Count：7 Percentile：31.11(Physics, Applied)The magnetic Compton profiles of FeRh intermetallic compound were measured to study the ferromagnetism induced by 200 MeV Xe ion irradiation. The magnetic effect at 50 K increases with increasing the ion-fluence. The analysis of the experimental result revealed that the values of spin moment induced by the irradiation were close to the values of magnetization obtained by a superconducting quantum interference device magnetometer, suggesting that the ion irradiation mainly induces the spin magnetic moment.
Fujimoto, Kayoko; Nakano, Tomohide; Kubo, Hirotaka; Sawada, Keiji*; Takizuka, Tomonori; Kawashima, Hisato; Shimizu, Katsuhiro; Asakura, Nobuyuki
Plasma and Fusion Research (Internet), 4, p.025_1 - 025_7, 2009/08
The volume recombination in detached divertor plasmas is a key process to reduce the ion flux to the divertor plates. Two-dimensional measurement is one of the ways to investigate a spatial structure of the volume recombination. In this work, the deuterium Balmer-series lines from a detached divertor plasma were observed two-dimensionally with a spatial resolution of 1 cm and were reconstructed into two-dimensional emissivities with a tomography technique. The ratio of the D
to the D
emissivity was compared to that calculated by the collisional-radiative model. This ratio could not be explained only by the excitation of D by electron impact, indicating that the volume recombination contributed to the D emission. This is the case for the region above the inner strike point with 8 cm and 4 cm, respectively, in the r- and the z-direction on the poloidal cross-section.
Nakano, Tomohide; Kubo, Hirotaka; Asakura, Nobuyuki; Shimizu, Katsuhiro; Kawashima, Hisato; Higashijima, Satoru
Journal of Nuclear Materials, 390-391, p.255 - 258, 2009/06
Times Cited Count：22 Percentile：80.29(Materials Science, Multidisciplinary)Therefore it is concluded that the dominant radiator, C, is produced by ionization of C
and recombination of C
at similar rates around the X-point in the detached plasma, and that C is the second biggest radiator. Further the transport loss of C will be investigated by an impurity transport code (IMPMC), in addition to comparison of the radiation power and atomic processes.
Nakano, Tomohide; Kubo, Hirotaka; Asakura, Nobuyuki; Shimizu, Katsuhiro
AIP Conference Proceedings 1125, p.131 - 140, 2009/05
no abstracts in English
Nakano, Tomohide; Kubo, Hirotaka; Asakura, Nobuyuki; Shimizu, Katsuhiro; Higashijima, Satoru
Proceedings of 22nd IAEA Fusion Energy Conference (FEC 2008) (CD-ROM), 8 Pages, 2008/10
It has been found that tungsten accumulation becomes more significant with increasing plasma rotation velocity against the plasma current direction, where negative radial electric field is formed. In a high density plasma at 62% of the Greenwald density, the tungsten accumulation levels decreased significantly, suggesting a shielding effect of the peripheral plasma. It has been found that 
is produced by the volume recombination of 
and the ionization of 
comparably. In contrast, the volume recombination of is not detected, and the ionization flux of is less than 1% of the generation flux. Thus, this result suggests that another loss mechanism of such as transport loss from the 
-point is significant.
in detached divertor plasmas of JT-60UNakano, Tomohide; Kubo, Hirotaka; Asakura, Nobuyuki; Shimizu, Katsuhiro; Konoshima, Shigeru; Fujimoto, Kayoko; Kawashima, Hisato; Higashijima, Satoru
Nuclear Fusion, 47(11), p.1458 - 1467, 2007/11
Times Cited Count：20 Percentile：57.53(Physics, Fluids & Plasmas)no abstracts in English
Fujimoto, Kayoko; Nakano, Tomohide; Kubo, Hirotaka; Sawada, Keiji*; Takizuka, Tomonori; Shimizu, Katsuhiro; Kawashima, Hisato; Asakura, Nobuyuki
Plasma and Fusion Research (Internet), 2, p.S1121_1 - S1121_4, 2007/11
Understanding deuterium particle behavior in the divertor plasma is necessary to study the ionizing and recombining plasmas. Two-dimensional spectroscopic measurement of deuterium emission is useful to understand deuterium particle behavior in divertor plasmas. The information of the ionization and recombination can be obtained by measurement of deuterium Balmer-series lines. A wide-spectral-band spectrometer with a CCD detector was used to observe deuterium Balmer-series lines with two-dimensional spatial distribution in the JT-60U divertor region. From the measurement, we can obtain a two-dimensional distribution of D and D
using a computer tomography technique. The D emission was strong above the strike point in the inner divertor and around the strike point in the outer divertor. The D emission was strong above the strike point in the inner divertor.
Kubo, Hirotaka; Sasaki, Akira; Moribayashi, Kengo; Higashijima, Satoru; Takenaga, Hidenobu; Shimizu, Katsuhiro; Nakano, Tomohide; Whiteford, A.*; Sugie, Tatsuo
Journal of Nuclear Materials, 363-365, p.1441 - 1445, 2007/06
Times Cited Count：6 Percentile：42.37(Materials Science, Multidisciplinary)no abstracts in English
Nakano, Tomohide; Asakura, Nobuyuki; Takenaga, Hidenobu; Kubo, Hirotaka; Shimizu, Katsuhiro; Kawashima, Hisato; JT-60 Team
Journal of Nuclear Materials, 363-365, p.1315 - 1322, 2007/06
Times Cited Count：11 Percentile：61(Materials Science, Multidisciplinary)no abstracts in English
Kubo, Hirotaka; Nakano, Tomohide; Asakura, Nobuyuki; Takenaga, Hidenobu; Tsuzuki, Kazuhiro; Oyama, Naoyuki; Kawashima, Hisato; Shimizu, Katsuhiro; Urano, Hajime; Fujimoto, Kayoko; et al.
Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03
no abstracts in English
Nakano, Tomohide; Kubo, Hirotaka; Asakura, Nobuyuki; Shimizu, Katsuhiro; Konoshima, Shigeru; Fujimoto, Kayoko; Kawashima, Hisato; Higashijima, Satoru
Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03
Volume recombination of C and 
into C is observed for the first time in detached plasmas with MARFE. It is found that the recombination flux of C to C is comparable to the ionization flux of C to C, and that the recombination zone is above an X-point and beneath the ionization zone. This result suggests that this volume recombination predominantly produces C ions, which contribute 60-80 % to the total radiation power in the divertor plasma.
Fujimoto, Kayoko; Nakano, Tomohide; Kubo, Hirotaka; Kawashima, Hisato; Shimizu, Katsuhiro; Asakura, Nobuyuki
Fusion Science and Technology, 51(2T), p.247 - 249, 2007/02
Times Cited Count：0 Percentile：0.01(Nuclear Science & Technology)no abstracts in English
Asakura, Nobuyuki; Kawashima, Hisato; Shimizu, Katsuhiro; Sakurai, Shinji; Fujita, Takaaki; Takenaga, Hidenobu; Nakano, Tomohide; Kubo, Hirotaka; Higashijima, Satoru; Hayashi, Takao; et al.
Europhysics Conference Abstracts (CD-ROM), 31F, 4 Pages, 2007/00
Divertor design for the JT-60 SA has been progressing in order to handle large heat flux during full pulse duration of 100 s. Divertor should be suitable for single null plasma experiments with the full power injection of 41 MW. The simulation results using 2D fluid (plasma) and Monte-Carlo (neutral) code are summarized. Lower single-null divertor is designed for ITER-like plasma configuration in order to study physics concept of the ITER divertor: control of the plasma detachment. Simulation results for various divertor geometries showed that the vertical target with V-shaped corner can produce plasma detachment near the outer strike-point for medium edge plasma density. It was also demonstrated that the divertor plasma became attached to move the outer strike point above the V-corner, suggesting that recover from sever detachment can be achieved by changing the plasma location. USN divertor will be designed for high-
plasma experiments with the highest shaping plasma of S=6.
Ninomiya, Hiromasa; Akiba, Masato; Fujii, Tsuneyuki; Fujita, Takaaki; Fujiwara, Masami*; Hamamatsu, Kiyotaka; Hayashi, Nobuhiko; Hosogane, Nobuyuki; Ikeda, Yoshitaka; Inoue, Nobuyuki; et al.
Journal of the Korean Physical Society, 49, p.S428 - S432, 2006/12
To contribute DEMO and ITER, the design to modify the present JT-60U into superconducting coil machine, named National Centralized Tokamak (NCT), is being progressed under nationwide collaborations in Japan. Mission, design and strategy of this NCT program is summarized.
Nakano, Tomohide; Asakura, Nobuyuki; Takenaga, Hidenobu; Kubo, Hirotaka; Miura, Yukitoshi; Shimizu, Katsuhiro; Konoshima, Shigeru; Masaki, Kei; Higashijima, Satoru; JT-60 Team
Nuclear Fusion, 46(5), p.626 - 634, 2006/05
Times Cited Count：21 Percentile：57.18(Physics, Fluids & Plasmas)In order to understand plasma-wall interactions in a long time scale, the discharge pulse length has been extended from 15 s to 65 s, with the NB-heating duration extended to 30 s. Nearly-saturation of the divertor plates was observed in the latter half of long pulse ELMy H-mode discharges. Particle sink into the divertor plates gradually decreased, and subsequently, wall-pumping efficiency became zero. This wall saturation resulted in a rise of the main plasma density without any auxiliary particle supply besides NB with divertor-pumping. Even when the total injected energy reached up to 
350 MJ in a discharge, neither sudden increase of carbon generation such as carbon bloom nor increase of the dilution of the main plasma was observed.
Kikuchi, Mitsuru; Tamai, Hiroshi; Matsukawa, Makoto; Fujita, Takaaki; Takase, Yuichi*; Sakurai, Shinji; Kizu, Kaname; Tsuchiya, Katsuhiko; Kurita, Genichi; Morioka, Atsuhiko; et al.
Nuclear Fusion, 46(3), p.S29 - S38, 2006/03
Times Cited Count：13 Percentile：41.68(Physics, Fluids & Plasmas)The National Centralized Tokamak (NCT) facility program is a domestic research program for advanced tokamak research to succeed JT-60U incorporating Japanese university accomplishments. The mission of NCT is to establish high beta steady-state operation for DEMO and to contribute to ITER. The machine flexibility and mobility is pursued in aspect ratio and shape controllability, feedback control of resistive wall modes, wide current and pressure profile control capability for the demonstration of the high-b steady state.
Takenaga, Hidenobu; Nakano, Tomohide; Asakura, Nobuyuki; Kubo, Hirotaka; Konoshima, Shigeru; Shimizu, Katsuhiro; Tsuzuki, Kazuhiro; Masaki, Kei; Tanabe, Tetsuo*; Ide, Shunsuke; et al.
Nuclear Fusion, 46(3), p.S39 - S48, 2006/03
Times Cited Count：18 Percentile：52.36(Physics, Fluids & Plasmas)no abstracts in English
