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Journal Articles

Microstructures and interface magnetic moments in Mn$$_{2}$$VAl/Fe layered films showing exchange bias

Kubota, Takahide*; Shimada, Yusuke*; Tsuchiya, Tomoki*; Yoshikawa, Tomoki*; Ito, Keita*; Takeda, Yukiharu; Saito, Yuji; Konno, Toyohiko*; Kimura, Akio*; Takanashi, Koki*

Nanomaterials (Internet), 11(7), p.1723_1 - 1723_11, 2021/07

 Times Cited Count:0 Percentile:0(Chemistry, Multidisciplinary)

Journal Articles

Effects of high-pressure annealing on critical current density in 122 type iron pnictide wires

Pyon, S.*; Tsuchiya, Yuji*; Inoue, Hiroshi*; Koizumi, Norikiyo; Kajitani, Hideki; Tamegai, Tsuyoshi*

Physica C, 504, p.69 - 72, 2014/09

 Times Cited Count:3 Percentile:17.38(Physics, Applied)

no abstracts in English

Journal Articles

Comparison of $$J$$c characteristics in PIT wires based on BaFe$$_{2}$$As$$_{2}$$ with different substitutions

Tamegai, Tsuyoshi*; Pyon, S.*; Ding, Q. P.*; Inoue, Hiroshi*; Kobayashi, Hiroki*; Tsuchiya, Yuji*; Sun, Y.*; Kajitani, Hideki; Koizumi, Norikiyo

Journal of Physics; Conference Series, 507(2), p.022041_1 - 022041_4, 2014/05

 Times Cited Count:3 Percentile:80.74

The author studied the effect of chemical compound for superconducting performance ($$J$$c) of iron-based superconductors. As a result, it was revealed that BaFe$$_{2}$$As$$_{2}$$ showed high Jc. And more, BaFe$$_{2}$$As$$_{2}$$ showed higer $$J$$c such as 32,000A/cm$$^{2}$$ (4.2K) by being applied of 120 MPa of hot isostatic pressure (HIP). Thus, higher $$J$$c performance could be achieved.

JAEA Reports

Study to improve recriticality evaluation methodology after severe accident (Joint research)

Kugo, Teruhiko; Ishikawa, Makoto; Nagaya, Yasunobu; Yokoyama, Kenji; Fukaya, Yuji; Maruyama, Hiromi*; Ishii, Yoshihiko*; Fujimura, Koji*; Kondo, Takao*; Minato, Hirokazu*; et al.

JAEA-Research 2013-046, 53 Pages, 2014/03

JAEA-Research-2013-046.pdf:4.42MB

The present report summarizes the results of a 2-year cooperative study between JAEA and Hitachi-GE in order to contribute to the settlement of the Fukushima-Daiichi Nuclear Power Plants which suffered from the severe accident on March 2011. In the present study, the possible scenarios to reach the recriticality events in Fukushima-Daiichi were investigated first. Then, the analytical methodology to evaluate the time-dependent recriticality events has been developed by modelling the reactivity insertion rate and the possible feedback according to the recriticality scenarios identified in the first step. The methodology developed here has been equipped as a transient simulation tool, PORCAS, which is operated on a multi-purpose platform for reactor analysis, MARBLE. Finally, the radiation exposure rates by the postulated recriticality events in Fukushima-Daiichi were approximately evaluated to estimate the impact to the public environment.

Journal Articles

Enhancement of critical current densities in (Ba,K)Fe$$_{2}$$As$$_{2}$$ by 320 MeV Au irradiation in single crystals and by high-pressure sintering in powder-in-tube wires

Pyon, S.*; Taen, Toshihiro*; Otake, Fumiaki*; Tsuchiya, Yuji*; Inoue, Hiroshi*; Akiyama, Hiroki*; Kajitani, Hideki; Koizumi, Norikiyo; Okayasu, Satoru; Tamegai, Tsuyoshi*

Applied Physics Express, 6(12), p.123101_1 - 123101_4, 2013/12

 Times Cited Count:19 Percentile:67.04(Physics, Applied)

We demonstrate a large enhancement of critical current density ($$J$$$$_{rm c}$$) up to 1.0 $$times$$ 10$$^{7}$$ A/cm$$^{2}$$ at 5 K under self-field in (Ba,K)Fe$$_{2}$$As$$_{2}$$ single crystals by irradiating 320 MeV Au ions. With the very promising potential of this material in mind, we have fabricated a (Ba,K)Fe$$_{2}$$As$$_{2}$$ superconducting wire through a powder-in-tube method combined with the hot isostatic pressing technique, whose effectiveness has been proven in industrial Bi2223 tapes. The Jc in the wire at 4.2 K has reached 37 kA/cm$$^{2}$$ under self-field and 3.0 kA/cm$$^{2}$$ at 90 kOe. Magneto-optical imaging of the wire confirmed the large intergranular Jc in the wire core.

Journal Articles

Evaluation of selected grades of beryllium metal as reflector materials for extended lifetime performance

Dorn, C. K.*; Tsuchiya, Kunihiko; Takemoto, Noriyuki; Ito, Masayasu; Hori, Junichi*; Chekushina, L.*; Hatano, Yuji*; Chakrov, P.*; Kawamura, Hiroshi

Proceedings of 6th International Symposium on Material Testing Reactors (ISMTR-6) (Internet), 9 Pages, 2013/10

no abstracts in English

Journal Articles

Basic study on surface chemical combination between beryllium metal and hydrogen isotope gas, 2

Ito, Masayasu; Kitagishi, Shigeru; Hanawa, Yoshio; Tsuchiya, Kunihiko; Hatano, Yuji*; Matsuyama, Masao*; Nagasaka, Takuya*; Hishinuma, Yoshimitsu*

Annual Report of National Institute for Fusion Science; April 2011 - March 2012, P. 535, 2012/12

Beryllium has been utilized as a moderator and/or reflector in a number of material testing reactors. Beryllium is also supposed to be widely used in fusion reactors as neutron multiplier and protective walls of plasma facing components. It is important to perform the characterization of the different grade beryllium such as the productivity, mechanical and chemical properties and the interaction under water and/or gas environment. In this study, three kinds of beryllium (S-200F, S-65H, I-220H) were prepared, and corrosion test and surface analysis of these beryllium samples were carried out for life time expansion under pure water. As a result, the surface change of each Be sample was observed by the corrosion test and influenced by the content of BeO and the grain size.

Journal Articles

Development of beryllium material for reflector lifetime expansion

Dorn, C. K.*; Tsuchiya, Kunihiko; Hatano, Yuji*; Chakrov, P.*; Kodama, Mitsuo*; Kawamura, Hiroshi

Proceedings of 5th International Symposium on Material Testing Reactors (ISMTR-5) (Internet), 9 Pages, 2012/10

The JMTR has used beryllium reflector since it began operation in 1968. Beryllium has been used as the reflector element material in the reactor, specifically S-200F structural grade beryllium in JMTR. As a part of the reactor upgrade, the Japan Atomic Energy Agency (JAEA) has carried out the cooperation experiments to extend the operating lifetime of the beryllium reflector elements. Thus, three kinds of beryllium metals such as S-200F, S-65H and I-220H were selected at the viewpoints of production methods, impurities and grain size of beryllium starting powders, mechanical properties. Now, data of the material properties and interaction between pure water and these beryllium grades are accumulated under un-irradiated. Additionally, irradiation tests have been prepared and development of PIE technologies has been performed. In this paper, the results of various properties and irradiation test plan for lifetime expansion of beryllium are described for material testing reactors.

Journal Articles

Effects of particle irradiations on vortex states in iron-based superconductors

Tamegai, Tsuyoshi*; Taen, Toshihiro*; Yagyuda, Hidenori*; Tsuchiya, Yuji*; Mohan, S.*; Taniguchi, Tomotaka*; Nakajima, Yasuyuki*; Okayasu, Satoru; Sasase, Masato*; Kitamura, Hisashi*; et al.

Superconductor Science and Technology, 25(8), p.084008_1 - 084008_14, 2012/08

 Times Cited Count:77 Percentile:93.85(Physics, Applied)

Various kinds of energetic particles are irradiated into iron-based superconductors, and their effects on the critical current density $$J$$$$_{rm c}$$ and vortex dynamics have been systematically studied. It is found that $$J$$$$_{rm c}$$ is enhanced and vortex dynamics is strongly suppressed by energetic particles having a sufficient energy deposition rate, similar to the case of high temperature cuprate superconductors. The enhancement of $$J$$$$_{rm c}$$, in general, persists up to much higher irradiation doses than in cuprates. However, details of the effect of irradiation depend on the kind of ion species and their energies. Even with the same ions and energies, the effect is not universal for different kinds of iron-based superconductors. The correlated nature of defects created by heavy-ion irradiation is confirmed by the angular dependence of irreversible magnetization.

Journal Articles

Status of material development for lifetime expansion of beryllium reflector

Dorn, C. K.*; Tsuchiya, Kunihiko; Hatano, Yuji*; Chakrov, P.*; Kodama, Mitsuo*; Kawamura, Hiroshi

JAEA-Conf 2011-003, p.93 - 97, 2012/03

The JMTR has used beryllium reflector since it began operation in 1968. Beryllium has been used as the reflector element material in the reactor, specifically S-200F structural grade beryllium in JMTR. As a part of the reactor upgrade, the Japan Atomic Energy Agency (JAEA) has carried out the cooperation experiments to extend the operating lifetime of the beryllium reflector elements. Thus, three kinds of beryllium metals such as S-200F, S-65H and I-220H were selected at the viewpoints of production methods, impurities and grain size of beryllium starting powders, mechanical properties. Now, data of the material properties of these beryllium grades are accumulated under un-irradiated and irradiated conditions. In this paper, the results of various properties and irradiation test plan for lifetime expansion of beryllium are described for material testing reactors.

Journal Articles

Basic study on surface chemical combination between beryllium metal and hydrogen isotope gas

Tsuchiya, Kunihiko; Kitagishi, Shigeru; Ito, Masayasu; Hanawa, Yoshio; Hatano, Yuji*; Matsuyama, Masao*; Nagasaka, Takuya*; Hishinuma, Yoshimitsu*

Annual Report of National Institute for Fusion Science; April 2010 - March 2011, P. 545, 2011/11

no abstracts in English

JAEA Reports

Investigation for methods of micro-structural observation of beryllium metals by TEM

Ito, Masayasu; Kawamata, Kazuo; Sozawa, Shizuo; Shibata, Akira; Tsuchiya, Kunihiko; Kitsunai, Yuji*; Kodama, Mitsuhiro*

JAEA-Testing 2011-003, 22 Pages, 2011/06

JAEA-Testing-2011-003.pdf:9.16MB

In JMTR, beryllium metal is used for neutron reflector. However, the periodical exchange of the neutron reflector is necessary due to degradation of strength and swelling under neutron irradiation. So it is required to select the material that bears long term from the viewpoint of the utilization rate improvement and the radioactive waste decrease in JMTR. It is important to evaluate the characteristics of beryllium metals precisely. This report describes the preparation method of the sample and observation results by the transmission electron microscope that is being examined as a evaluation method of the beryllium metal.

Journal Articles

Surface analysis for chemical combination of beryllium metals

Tsuchiya, Kunihiko; Hanawa, Yoshio; Kitagishi, Shigeru; Ito, Masayasu; Hatano, Yuji*; Matsuyama, Masao*

Heisei-21-Nendo Toyama Daigaku Kyodo Riyo, Kyodo Kenkyu Seika Hokokusho, p.9 - 10, 2010/12

no abstracts in English

Journal Articles

Effects of heavy-ion irradiation on the vortex state in Ba(Fe$$_{1-x}$$Co$$_{x}$$)$$_{2}$$As$$_{2}$$

Tamegai, Tsuyoshi*; Tsuchiya, Yuji*; Taen, Toshihiro*; Nakajima, Yasuyuki*; Okayasu, Satoru; Sasase, Masato*

Physica C, 470(Suppl.1), p.S360 - S362, 2010/12

 Times Cited Count:1 Percentile:7.06(Physics, Applied)

We report effects of heavy-ion irradiation in Ba(Fe$$_{1-x}$$Co$$_{x}$$)$$_{2}$$As$$_{2}$$ single crystals. The columnar defects with about 40% of the irradiation dose are confirmed by transmission electron microscopy. Magneto-optical imaging and bulk magnetization measurements reveal strong enhancement of the critical current density in the irradiated region. The vortex creep rate is also strongly suppressed by the columnar defects. Effects of heavy-ion irradiation into Ba(Fe$$_{1-x}$$Co$$_{x}$$)$$_{2}$$As$$_{2}$$ and cuprate superconductors are compared.

JAEA Reports

Dismantlement technique of irradiation facilities in JMTR

Onuma, Yuichi; Okada, Yuji; Hanawa, Hiroshi; Tsuchiya, Kunihiko; Kanno, Masaru

JAEA-Review 2010-047, 27 Pages, 2010/11

JAEA-Review-2010-047.pdf:3.0MB

The Japan Materials Testing Reactor (JMTR) has been refurbished to re-operate from 2011. As a part of the establishment of new irradiation facilities, technology development for the dismantling and removing of irradiation facilities such as OWL-1 (Oarai Water Loop No.1), OWL-2 (Oarai Water Loop No.2) and IASCC (Irradiation Assisted Stress Corrosion Cracking) facility installed in the JMTR loop cubicles has been performed. By using developed methods, techniques for the dismantling and removing of the irradiation facilities were established.

Journal Articles

Critical current densities and flux creep rate in Co-doped BaFe$$_{2}$$As$$_{2}$$ with columnar defects introduced by heavy-Ion irradiation

Nakajima, Yasuyuki*; Tsuchiya, Yuji*; Taen, Toshihiro*; Yagyuda, Hidenori*; Tamegai, Tsuyoshi*; Okayasu, Satoru; Sasase, Masato*; Kitamura, Hisashi*; Murakami, Takeshi*

Physica C, 470(20), p.1103 - 1105, 2010/11

 Times Cited Count:3 Percentile:18.65(Physics, Applied)

We report the formation of columnar defects in Co-doped BaFe$$_{2}$$As$$_{2}$$ single crystals with different heavy ion irradiations. The formation of columnar defects by 200 MeV Au ion irradiation is confirmed by transmission electron microscopy and their density is about 40% of the irradiation dose. Magneto-optical imaging and bulk magnetization measurements reveal that the critical current density $$J$$$$_{rm c}$$ is enhanced in the 200 MeV Au and 800 MeV Xe ion irradiated samples while $$J$$$$_{rm c}$$ is unchanged in the 200 MeV Ni ion irradiated sample. We also find that vortex creep rates are strongly suppressed by the columnar defects. We compare the effect of heavy-ion irradiation into Co-doped BaFe$$_{2}$$As$$_{2}$$ and cuprate superconductors.

Journal Articles

Critical current densities and vortex dynamics in Ba(Fe$$_{1-x}$$Co$$_{x}$$)$$_{2}$$As$$_{2}$$ single crystals

Tamegai, Tsuyoshi*; Taen, Toshihiro*; Tsuchiya, Yuji*; Nakajima, Yasuyuki*; Okayasu, Satoru; Sasase, Masato*

Journal of Superconductivity and Novel Magnetism, 23(5), p.605 - 608, 2010/07

 Times Cited Count:0 Percentile:0(Physics, Applied)

Superconducting properties are evaluated for high-quality single crystals of Ba(Fe$$_{1-x}$$Co$$_{x}$$)$$_{2}$$As$$_{2}$$ in a wide range of doping levels. The critical current density, $$J$$$$_{rm c}$$, in an optimally-doped crystal (Tc $$sim$$ 24 K) shows a fishtail effect with its value over 10$$^{5}$$ A/cm$$^{2}$$ even at 5 T below 10 K. Magneto-optical imaging has clarified rather homogeneous supercurrent flow in the crystal, in spite of a large amount of impurities. In the heavy-ion irradiated sample, the presence of columnar defects are confirmed and $$J$$$$_{rm c}$$ has been enhanced by a factor of five at low temperatures, reaching 6 $$times$$ 10$$^{6}$$ A/cm$$^{2}$$ at 2 K under zero field. Flux creep rate in the heavy-ion irradiated sample has been reduced in accordance with the enhancement of $$J$$$$_{rm c}$$.

Journal Articles

Recent progress in the energy recovery linac project in Japan

Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05

Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.

Journal Articles

Does Gd@C$$_{82}$$ have an anomalous endohedral structure? Synthesis and single crystal X-ray structure of the carbene adduct

Akasaka, Takeshi*; Kono, Takayoshi*; Takematsu, Yuji*; Nikawa, Hidefumi*; Nakahodo, Tsukasa*; Wakahara, Takatsugu*; Ishitsuka, Midori*; Tsuchiya, Takahiro*; Maeda, Yutaka*; Liu, M. T. H.*; et al.

Journal of the American Chemical Society, 130(39), p.12840 - 12841, 2008/10

 Times Cited Count:70 Percentile:84.61(Chemistry, Multidisciplinary)

We report here the results on single crystal X-ray crystallographic analysis of the Gd@C$$_{82}$$ carbene adduct (Gd@C$$_{82}$$(ad), Ad=adamantylidene). The Gd atom in Gd@C$$_{82}$$(Ad) is located at an off-centered position near a hexagonal ring in the C2v-C$$_{82}$$ cage, as found for M@C$$_{82}$$ (M = Sc and La) and La@C$$_{82}$$(Ad). Theoretical calculation also confirms the position of the Gd atom in the X-ray crystal structure.

Journal Articles

Recent results on beryllium and beryllides in Japan

Mishima, Yoshinao*; Yoshida, Naoaki*; Kawamura, Hiroshi; Ishida, Kiyohito*; Hatano, Yuji*; Shibayama, Tamaki*; Munakata, Kenzo*; Sato, Yoshiyuki*; Uchida, Munenori*; Tsuchiya, Kunihiko; et al.

Journal of Nuclear Materials, 367-370(2), p.1382 - 1386, 2007/08

 Times Cited Count:23 Percentile:83.86(Materials Science, Multidisciplinary)

no abstracts in English

27 (Records 1-20 displayed on this page)