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Journal Articles

Behavior of Sm in the boron cage of Sm-doped $$R$$B$$_{6}$$ ($$R$$ =Yb, La) observed by multiple-wavelength neutron holography

Uechi, Shoichi*; Oyama, Kenji*; Fukumoto, Yohei*; Kanazawa, Yuki*; Happo, Naohisa*; Harada, Masahide; Inamura, Yasuhiro; Oikawa, Kenichi; Matsuhra, Wataru*; Iga, Fumitoshi*; et al.

Physical Review B, 102(5), p.054104_1 - 054104_10, 2020/08

 Times Cited Count:0 Percentile:100(Materials Science, Multidisciplinary)

Journal Articles

Energy of the $$^{229}$$Th nuclear clock isomer determined by absolute $$gamma$$-ray energy difference

Yamaguchi, Atsushi*; Muramatsu, Haruka*; Hayashi, Tasuku*; Yuasa, Naoki*; Nakamura, Keisuke; Takimoto, Misaki; Haba, Hiromitsu*; Konashi, Kenji*; Watanabe, Makoto*; Kikunaga, Hidetoshi*; et al.

Physical Review Letters, 123(22), p.222501_1 - 222501_6, 2019/11

 Times Cited Count:5 Percentile:33.25(Physics, Multidisciplinary)

Journal Articles

Temperature of thermal spikes induced by swift heavy ions

Matsuzaki, Shota*; Hayashi, Hiroaki*; Nakajima, Kaoru*; Matsuda, Makoto; Sataka, Masao*; Tsujimoto, Masahiko*; Toulemonde, M.*; Kimura, Kenji*

Nuclear Instruments and Methods in Physics Research B, 406(Part B), p.456 - 459, 2017/09

 Times Cited Count:3 Percentile:50.46(Instruments & Instrumentation)

Journal Articles

Multiple-wavelength neutron holography with pulsed neutrons

Hayashi, Koichi*; Oyama, Kenji*; Happo, Naohisa*; Matsushita, Tomohiro*; Hosokawa, Shinya*; Harada, Masahide; Inamura, Yasuhiro; Nitani, Hiroaki*; Shishido, Toetsu*; Yubuta, Kunio*

Science Advances (Internet), 3(8), p.e1700294_1 - e1700294_7, 2017/08

Journal Articles

Magnetocaloric effect of Sr-substituted BaFeO$$_{3}$$ in the liquid nitrogen and natural gas temperature regions

Yoshii, Kenji; Hayashi, Naoaki*; Mizumaki, Masaichiro*; Takano, Mikio*

AIP Advances (Internet), 7(4), p.045117_1 - 045117_6, 2017/04

 Times Cited Count:2 Percentile:81.55(Nanoscience & Nanotechnology)

We have investigated the magnetocaloric effect (MCE) of Ba$$_{1-x}$$Sr$$_{x}$$Fe$$^{4+}$$O$$_{3}$$ (x$$underline{<}$$0.2), a series of cubic perovskites showing a field-induced transition from helical antiferromagnetism to ferromagnetism. The maximum magnetic entropy change (-$$Delta$$S$$_{max}$$) at 50 kOe varies from $$sim$$ 5.8 J kg$$^{-1}$$K$$^{-1}$$ (x=0) to $$sim$$ 4.9 J kg$$^{-1}$$K$$^{-1}$$ (x=0.2), while the refrigerant capacity remains almost the same at $$sim$$165 J kg$$^{-1}$$. Interestingly, the temperature of -$$Delta$$S$$_{max}$$ decreases from $$sim$$116 K to $$sim$$77 K with increasing x, providing this series of rare-earth-free oxides with potential as a magnetic refrigerant for the liquefaction of nitrogen and natural gas.

Journal Articles

Deuterium permeation behavior for damaged tungsten by ion implantation

Oya, Yasuhisa*; Li, X.*; Sato, Misaki*; Yuyama, Kenta*; Oyaizu, Makoto; Hayashi, Takumi; Yamanishi, Toshihiko; Okuno, Kenji*

Journal of Nuclear Science and Technology, 53(3), p.402 - 405, 2016/03

 Times Cited Count:9 Percentile:21.82(Nuclear Science & Technology)

The deuterium (D) permeation behaviors for ion damaged tungsten (W) by 3 keV D$$_{2}$$$$^{+}$$ and 10 keV C$$^{+}$$ were studied. The D permeability was obtained for un-damaged W at various temperatures. For both D$$_{2}$$$$^{+}$$ and C$$^{+}$$ implanted W, the permeability was clearly reduced. But, for the D$$_{2}$$$$^{+}$$ implanted W, the permeability was recovered by heating at 1173 K and it was almost consistent with that for un-damaged W. In the case of C$$^{+}$$ implanted W, the permeability was not recovered even if the sample was heated at 1173 K, indicating that the existence of carbon would prevent the recovery of permeation path in W. In addition, TEM observation showed the voids were grown by heating at 1173 K and not removed, showing the existence of damages would not largely influence on the hydrogen permeation behavior in W in the present study.

Journal Articles

Progress report of Japanese simulation research projects using the high-performance computer system Helios in the International Fusion Energy Research Centre

Ishizawa, Akihiro*; Idomura, Yasuhiro; Imadera, Kenji*; Kasuya, Naohiro*; Kanno, Ryutaro*; Satake, Shinsuke*; Tatsuno, Tomoya*; Nakata, Motoki*; Nunami, Masanori*; Maeyama, Shinya*; et al.

Purazuma, Kaku Yugo Gakkai-Shi, 92(3), p.157 - 210, 2016/03

The high-performance computer system Helios which is located at The Computational Simulation Centre (CSC) in The International Fusion Energy Research Centre (IFERC) started its operation in January 2012 under the Broader Approach (BA) agreement between Japan and the EU. The Helios system has been used for magnetised fusion related simulation studies in the EU and Japan and has kept high average usage rate. As a result, the Helios system has contributed to many research products in a wide range of research areas from core plasma physics to reactor material and reactor engineering. This project review gives a short catalogue of domestic simulation research projects. First, we outline the IFERC-CSC project. After that, shown are objectives of the research projects, numerical schemes used in simulation codes, obtained results and necessary computations in future.

Journal Articles

Local structure of room-temperature superionic Ag-GeSe$$_3$$ glasses

Stellhorn, J. R.*; Hosokawa, Shinya*; Kawakita, Yukinobu; Gies, D.*; Pilgrim, W.-C.*; Hayashi, Koichi*; Oyama, Kenji*; Blanc, N.*; Boudet, N.*

Journal of Non-Crystalline Solids, 431, p.68 - 71, 2016/01

 Times Cited Count:6 Percentile:54.52(Materials Science, Ceramics)

Journal Articles

Spontaneous formation of suboxidic coordination around Co in ferromagnetic rutile Ti$$_{0.95}$$Co$$_{0.05}$$O$$_2$$ film

Hu, W.*; Hayashi, Koichi*; Fukumura, Tomoteru*; Akagi, Kazuto*; Tsukada, Masaru*; Happo, Naohisa*; Hosokawa, Shinya*; Owada, Kenji; Takahashi, Masamitsu; Suzuki, Motohiro*; et al.

Applied Physics Letters, 106(22), p.222403_1 - 222403_5, 2015/06

 Times Cited Count:28 Percentile:16.63(Physics, Applied)

Journal Articles

Electronic structure of BaFeO$$_{3}$$ studied by X-ray spectroscopy

Mizumaki, Masaichiro*; Fujii, Hitoshi*; Yoshii, Kenji; Hayashi, Naoaki*; Saito, Takashi*; Shimakawa, Yuichi*; Uozumi, Takayuki*; Takano, Mikio*

Physica Status Solidi (C), 12(6), p.818 - 821, 2015/06

 Times Cited Count:6 Percentile:7.01

We investigated the electronic structure of BaFeO$$_{3}$$ by using HAXPES and XAS measurements and first principle studies. The experimental and theoretical results indicated that BaFeO$$_{3}$$ is a negative charge transfer compound. We concluded that the on-site Coulomb energy and the strong hybridization between Fe-3d and O-2p orbitals play a very important role of emergence of negative charge transfer. And we found the new structure in the Fe-2p XPS spectrum and concluded this structure is originated from non-local screening.

Journal Articles

R&D status on water cooled ceramic breeder blanket technology

Enoeda, Mikio; Tanigawa, Hisashi; Hirose, Takanori; Nakajima, Motoki; Sato, Satoshi; Ochiai, Kentaro; Konno, Chikara; Kawamura, Yoshinori; Hayashi, Takumi; Yamanishi, Toshihiko; et al.

Fusion Engineering and Design, 89(7-8), p.1131 - 1136, 2014/10

 Times Cited Count:17 Percentile:12.12(Nuclear Science & Technology)

The development of a Water Cooled Ceramic Breeder (WCCB) Test Blanket Module (TBM) is being performed as one of the most important steps toward DEMO blanket in Japan. Regarding the fabrication technology development using F82H, the fabrication of a real scale mockup of the back wall of TBM was completed. Also the assembling of the complete box structure of the TBM mockup and planning of the pressurization testing was studied. The development of advanced breeder and multiplier pebbles for higher chemical stability was performed for future DEMO blanket application. From the view point of TBM test result evaluation and DEMO blanket performance design, the development of the blanket tritium simulation technology, investigation of the TBM neutronics measurement technology and the evaluation of tritium production and recovery test using D-T neutron in the Fusion Neutronics Source (FNS) facility has been performed.

Journal Articles

Study of safety features and accident scenarios in a fusion DEMO reactor

Nakamura, Makoto; Tobita, Kenji; Gulden, W.*; Watanabe, Kazuhito*; Someya, Yoji; Tanigawa, Hisashi; Sakamoto, Yoshiteru; Araki, Takao*; Matsumiya, Hisato*; Ishii, Kyoko*; et al.

Fusion Engineering and Design, 89(9-10), p.2028 - 2032, 2014/10

 Times Cited Count:10 Percentile:26.91(Nuclear Science & Technology)

After the Fukushima Dai-ichi nuclear accident, a social need for assuring safety of fusion energy has grown gradually in the Japanese (JA) fusion research community. DEMO safety research has been launched as a part of BA DEMO Design Activities (BA-DDA). This paper reports progress in the fusion DEMO safety research conducted under BA-DDA. Safety requirements and evaluation guidelines have been, first of all, established based on those established in the Japanese ITER site invitation activities. The amounts of radioactive source terms and energies that can mobilize such source terms have been assessed for a reference DEMO, in which the blanket technology is based on the Japanese fusion technology R&D programme. Reference event sequences expected in DEMO have been analyzed based on the master logic diagram and functional FMEA techniques. Accident initiators of particular importance in DEMO have been selected based on the event sequence analysis.

Journal Articles

Hydrogen isotope behavior on a water-metal boundary with simultaneous transfer from and to the metal surface

Hayashi, Takumi; Isobe, Kanetsugu; Nakamura, Hirofumi; Kobayashi, Kazuhiro; Oya, Yasuhisa*; Okuno, Kenji*; Oyaizu, Makoto; Edao, Yuki; Yamanishi, Toshihiko

Fusion Engineering and Design, 89(7-8), p.1520 - 1523, 2014/10

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

Tritium confinement is the most important safety issue in the fusion reactor. Tritium behavior on the water metal boundary is very important to design tritium plant with breading blanket system using cooling water. A series of tritium permeation experiment into pressurized water or water vapor jacket with He or Ar have been performed through pure iron piping with/without 7 micro-meter gold plating, which contained about 1 kPa of pure tritium gas at 423 K, with monitoring the chemical forms of tritium. Also, deuterium permeation experiments from heavy water vessel through various metal piping, such as pure iron (Fe), nickel (Ni), stainless steel (SS304), and pure iron with 10 micro-meter gold plating, were performed at 573 K and at 15 MPa. Recently, using the above heavy water system, we have succeeded to detect simultaneous hydrogen isotopes transfer from and to the metal surface by introducing H$$_{2}$$ gas to the metal piping after stabilized deuterium permeation was detected.

Journal Articles

Key aspects of the safety study of a water-cooled fusion DEMO reactor

Nakamura, Makoto; Tobita, Kenji; Someya, Yoji; Tanigawa, Hisashi; Gulden, W.*; Sakamoto, Yoshiteru; Araki, Takao*; Watanabe, Kazuhito*; Matsumiya, Hisato*; Ishii, Kyoko*; et al.

Plasma and Fusion Research (Internet), 9, p.1405139_1 - 1405139_11, 2014/10

Key aspects of the safety study of a water-cooled fusion DEMO reactor is reported. Safety requirements, dose target, DEMO plant model and confinement strategy of the safety study are briefly introduced. The internal hazard of a water-cooled DEMO, i.e. radioactive inventories, stored energies that can mobilize these inventories and accident initiators and scenarios, are evaluated. It is pointed out that the enthalpy in the first wall/blanket cooling loops, the decay heat and the energy potentially released by the Be-steam chemical reaction are of special concern for the water-cooled DEMO. An ex-vessel loss-of-coolant of the first wall/blanket cooling loop is also quantitatively analyzed. The integrity of the building against the ex-VV LOCA is discussed.

Journal Articles

Improvement of the position monitor using white light interferometer for measuring precise movement of compact ERL superconducting cavities in cryomodule

Sakai, Hiroshi*; Enami, Kazuhiro*; Furuya, Takaaki*; Sato, Masato*; Shinoe, Kenji*; Umemori, Kensei*; Sawamura, Masaru; Cenni, E.*; Aoto, Tomohiro*; Hayashi, Kyohei*; et al.

Proceedings of 5th International Particle Accelerator Conference (IPAC '14) (Internet), p.1787 - 1789, 2014/07

Alignment of superconducting cavities is one of the important issues for linear collider and/or future light source like ERL and X-FEL. To measure the cavity displacement under cooling to liquid He temperature more precisely, we newly developed the position monitor based on the measurement of the interference of light between the measurement target and the reference point. We applied this monitor to the main linac cryomodule of Compact ERL (cERL) and successfully measured the displacement during 2 K cooling with the resolution of 10 $$mu$$m.

Journal Articles

Acute and obtuse rhombohedrons in the local structures of relaxor ferroelectric Pb(Mg$$_{1/3}$$Nb$$_{2/3}$$)O$$_3$$

Hu, W.*; Hayashi, Koichi*; Owada, Kenji; Chen, J.*; Happo, Naohisa*; Hosokawa, Shinya*; Takahashi, Masamitsu; Bokov, A.*; Ye, Z.-G*

Physical Review B, 89(14), p.140103_1 - 140103_5, 2014/04

 Times Cited Count:33 Percentile:14.55(Materials Science, Multidisciplinary)

Journal Articles

Precise measurement of superconducting cavity movement in cryomodule by the position monitor using white light interferometer

Sakai, Hiroshi*; Aoto, Tomohiro*; Enami, Kazuhiro*; Furuya, Takaaki*; Sato, Masato*; Shinoe, Kenji*; Umemori, Kensei*; Sawamura, Masaru; Cenni, E.*; Hayashi, Kyohei*; et al.

Proceedings of 16th International Conference on RF Superconductivity (SRF 2013) (Internet), p.291 - 296, 2014/02

Alignment of superconducting cavities is one of the important issues for linear collider and/or future light source like ERL and X-FEL. To measure the cavity displacement under cooling to liquid He temperature more precisely, we newly developed the position monitor by using white light interferometer. This monitor is based on the measurement of the interference of light between the measurement target and the reference point. It can measure the position from the outside of the cryomodule. We applied this monitor to the main linac cryomodule of Compact ERL (cERL) and successfully measured the displacement during 2 K cooling with the resolution of 10 $$mu$$m.

Journal Articles

Magnetocaloric effect of field-induced ferromagnet BaFeO$$_{3}$$

Mizumaki, Masaichiro*; Yoshii, Kenji; Hayashi, Naoaki*; Saito, Takashi*; Shimakawa, Yuichi*; Takano, Mikio*

Journal of Applied Physics, 114(7), p.073901_1 - 073901_6, 2013/08

 Times Cited Count:16 Percentile:35.36(Physics, Applied)

We have investigated the magnetocaloric effect (MCE) of a perovskite oxide, BaFeO$$_{3}$$, that shows ferromagnetism by the aid of a small external field of about 0.3 T below the Curie temperature T$$_{C}$$ = 111 K. The magnetization is found to change almost reversibly in both field and temperature cycles. Hence, magnetic and thermal hysteretic losses are negligibly low during refrigeration, a property that is suitable for application. The reversible MCE is likely to arise from the absence of an orbital magnetic moment of Fe ions which are essentially in the Fe$$^{3+}$$L state (L: ligand hole). The magnetic entropy change and refrigerant capacity near the T$$_{C}$$ are about 5.8 J kg$$^{-1}$$ K$$^{-1}$$ and about 172 J kg$$^{-1}$$, respectively, both of which are comparable to those of ferromagnetic perovskite manganites. As BaFeO$$_{3}$$ contains no rare metals and is stable against corrosion, the material can be regarded as a candidate refrigerant material.

Journal Articles

${it Arabidopsis sos1}$ mutant in a salt-tolerant accession revealed an importance of salt acclimation ability in plant salt tolerance

Ariga, Hirotake*; Katori, Taku*; Yoshihara, Ryohei*; Hase, Yoshihiro; Nozawa, Shigeki; Narumi, Issei; Iuchi, Satoshi*; Kobayashi, Masatomo*; Tezuka, Kenji*; Sakata, Yoichi*; et al.

Plant Signaling & Behavior (Internet), 8(7), p.e24779_1 - e24779_5, 2013/07

Based on analysis of the salinity tolerance among 354 ${it Arabidopsis thaliana}$ accessions, some accessions showed greater salt shock tolerance compared with a reference accession, Col-0 on a typical assay with drastic change in NaCl concentration from 0 mM to 225 mM. On the other hand, several accessions including Zu-0 exhibited marked acquired salt tolerance, which is induced after exposure to moderate salt stress (salt acclimation ability). It is likely that Arabidopsis plants have at least two types of tolerance abilities, salt shock tolerance and salt acclimation. To dissect the salt tolerance mechanisms of the salt tolerant accessions, we isolated a salt-sensitive mutant from ion beam-mutagenized Zu-0 seedlings. The mutant showed severe growth inhibition under salt shock stress due to a single base deletion in SOS1 gene as well-known salt shock tolerance gene, even more salt sensitive than Col-0. Nevertheless, the mutant was able to survive on the salt acclimation with 100 mM NaCl for 7 days followed with 750 mM sorbitol for 20 days (salt acclimation assay) as well as the Zu-0 wild type, whereas Col-0 showed apparent chlorosis under the condition. We propose that a gene for salt acclimation ability is different from a gene for salt shock tolerance and plays an important role in acquisition for marked salt- or osmotic tolerance.

Journal Articles

Manufacturing and development of JT-60SA vacuum vessel and divertor

Sakasai, Akira; Masaki, Kei; Shibama, Yusuke; Sakurai, Shinji; Hayashi, Takao; Nakamura, Shigetoshi; Ozaki, Hidetsugu; Yokoyama, Kenji; Seki, Yohji; Shibanuma, Kiyoshi; et al.

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

The JT-60SA vacuum vessel (VV) and divertor are key components for the performance requirements. Therefore the manufacturing and development of VV and divertor are in progress, inclusive of the superconducting magnets. The vacuum vessel has a double wall structure in high rigidity to withstand electromagnetic force at disruption and to keep high toroidal one-turn resistance. In addition, the double wall structure fulfills originally two functions. (1) The remarkable reduction of the nuclear heating in the superconducting magnets is made by boric-acid water circulated in the double wall. (2) The effective baking is enabled by nitrogen gas flow of 200$$^{circ}$$C in the double wall after draining of water. Three welding types were chosen for the manufacturing of the double wall structure VV to minimize deformation by welding. Divertor cassettes with fully water cooled plasma facing components were designed to realize the JT-60SA lower single null closed divertor. The divertor cassettes in the radio-active VV have been developed to ensure compatibility with remote handling (RH) maintenance in order to allow long pulse high performance discharges with high neutron yield. The manufacturing of divertor cassettes with typical accuracy of *1 mm has been successfully completed. Brazed CFC (carbon fiber composite) monoblock targets for a divertor target have been manufactured by precise control of tolerances inside CFC blocks. The infrared thermography test of monoblock targets has been developed as new acceptance inspection.

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