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Journal Articles

Measurements and analyses of the distribution of the radioactivity induced by the secondary neutrons produced by 17-MeV protons in compact cyclotron facility

Matsuda, Norihiro; Izumi, Yuichi*; Yamanaka, Yoshiyuki*; Gando, Toshiyuki*; Yamada, Masaaki*; Oishi, Koji*

EPJ Web of Conferences (Internet), 153, p.07001_1 - 07001_6, 2017/09

 Times Cited Count:0 Percentile:100

Journal Articles

Thermodynamic evidence for nematic superconductivity in Cu$$_{x}$$Bi$$_{2}$$Se$$_{3}$$

Yonezawa, Shingo*; Tajiri, Kengo*; Nakata, Suguru*; Nagai, Yuki; Wang, Z.*; Segawa, Koji*; Ando, Yoichi*; Maeno, Yoshiteru*

Nature Physics, 13(2), p.123 - 126, 2017/02

 Times Cited Count:76 Percentile:0.69(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Universal scaling for the spin-electricity conversion on surface states of topological insulators

Yamamoto, Keita*; Shiomi, Yuki*; Segawa, Koji*; Ando, Yoichi*; Saito, Eiji

Physical Review B, 94(2), p.024404_1 - 024401_6, 2016/05

 Times Cited Count:8 Percentile:38.92(Materials Science, Multidisciplinary)

We have investigated spin-electricity conversion on surface states of bulk-insulating topological insulator (TI) materials using a spin-pumping technique. The sample structure is Ni-Fe/Cu/TI trilayers, in which magnetic proximity effects on the TI surfaces are negligibly small owing to the inserted Cu layer. Voltage signals produced by the spin-electricity conversion are clearly observed and are enhanced with decreasing temperature, in line with the dominant surface transport at lower temperatures. The efficiency of the spin-electricity conversion is greater for TI samples with a higher resistivity of bulk states and longer mean free path of surface states, consistent with the surface spin-electricity conversion.

Journal Articles

Spin-electricity conversion induced by spin injection into topological insulators

Shiomi, Yuki*; Nomura, Kentaro*; Kajiwara, Yosuke*; Eto, Kazuma*; Novak, M.*; Segawa, Koji*; Ando, Yoichi*; Saito, Eiji

Physical Review Letters, 113(19), p.196601_1 - 196601_5, 2014/11

 Times Cited Count:158 Percentile:0.89(Physics, Multidisciplinary)

JAEA Reports

Conceptual design of the SlimCS fusion DEMO reactor

Tobita, Kenji; Nishio, Satoshi*; Enoeda, Mikio; Nakamura, Hirofumi; Hayashi, Takumi; Asakura, Nobuyuki; Uto, Hiroyasu; Tanigawa, Hiroyasu; Nishitani, Takeo; Isono, Takaaki; et al.

JAEA-Research 2010-019, 194 Pages, 2010/08

JAEA-Research-2010-019-01.pdf:48.47MB
JAEA-Research-2010-019-02.pdf:19.4MB

This report describes the results of the conceptual design study of the SlimCS fusion DEMO reactor aiming at demonstrating fusion power production in a plant scale and allowing to assess the economic prospects of a fusion power plant. The design study has focused on a compact and low aspect ratio tokamak reactor concept with a reduced-sized central solenoid, which is novel compared with previous tokamak reactor concept such as SSTR (Steady State Tokamak Reactor). The reactor has the main parameters of a major radius of 5.5 m, aspect ratio of 2.6, elongation of 2.0, normalized beta of 4.3, fusion out put of 2.95 GW and average neutron wall load of 3 MW/m$$^{2}$$. This report covers various aspects of design study including systemic design, physics design, torus configuration, blanket, superconducting magnet, maintenance and building, which were carried out increase the engineering feasibility of the concept.

Journal Articles

Beam injection tuning of the J-PARC main ring

Wei, G.; Koseki, Tadashi*; Igarashi, Susumu*; Tomizawa, Masahito*; Takano, Jumpei*; Ishii, Koji*; Shirakata, Masashi*; Fan, K.*; Hatakeyama, Shuichiro; Uota, Masahiko*; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.3915 - 3917, 2010/05

Journal Articles

Beam fast extraction tuning of the J-PARC main ring

Wei, G.; Koseki, Tadashi*; Tomizawa, Masahito*; Igarashi, Susumu*; Ishii, Koji*; Ando, Ainosuke; Takano, Jumpei*; Uota, Masahiko*; Fan, K.*; Hatakeyama, Shuichiro; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.3918 - 3920, 2010/05

Journal Articles

Compact DEMO, SlimCS; Design progress and issues

Tobita, Kenji; Nishio, Satoshi; Enoeda, Mikio; Kawashima, Hisato; Kurita, Genichi; Tanigawa, Hiroyasu; Nakamura, Hirofumi; Honda, Mitsuru; Saito, Ai*; Sato, Satoshi; et al.

Nuclear Fusion, 49(7), p.075029_1 - 075029_10, 2009/07

 Times Cited Count:111 Percentile:1.56(Physics, Fluids & Plasmas)

Recent design study on SlimCS focused mainly on the torus configuration including blanket, divertor, materials and maintenance scheme. For vertical stability of elongated plasma and high beta access, a sector-wide conducting shell is arranged in between replaceable and permanent blanket. The reactor adopts pressurized-water-cooled solid breeding blanket. Compared with the previous advanced concept with supercritical water, the design options satisfying tritium self-sufficiency are relatively scarce. Considered divertor technology and materials, an allowable heat load to the divertor plate should be 8 MW/m$$^{2}$$ or lower, which can be a critical constraint for determining a handling power of DEMO (a combination of alpha heating power and external input power for current drive).

Journal Articles

Local electronic structure of Cr in the II-VI diluted ferromagnetic semiconductor Zn$$_{1-x}$$Cr$$_x$$Te

Kobayashi, Masaki*; Ishida, Yukiaki*; Hwang, J. I.*; Song, G. S.*; Fujimori, Atsushi; Yang, C. S.*; Lee, L.*; Lin, H.-J.*; Huang, D.-J.*; Chen, C. T.*; et al.

New Journal of Physics (Internet), 10, p.055011_1 - 055011_15, 2008/05

 Times Cited Count:11 Percentile:38.39(Physics, Multidisciplinary)

Journal Articles

Prediction accuracy improvement of neutronic characteristics of a breeding light water reactor core by extended bias factor methods with use of FCA-XXII-1 critical experiments

Kugo, Teruhiko; Ando, Masaki; Kojima, Kensuke; Fukushima, Masahiro; Mori, Takamasa; Nakano, Yoshihiro; Okajima, Shigeaki; Kitada, Takanori*; Takeda, Toshikazu*

Journal of Nuclear Science and Technology, 45(4), p.288 - 303, 2008/04

 Times Cited Count:6 Percentile:52.62(Nuclear Science & Technology)

The effectiveness of the extended bias factor methods, the LC and PE methods, is numerically investigated by applying them to a breeding light water reactor core as a target core with use of FCA-XXII-1 critical experiments. The present study numerically verifies the features of the extended bias factor methods. Both the methods can improve the prediction accuracy the most by using all the experiments. The PE method always improves the prediction accuracy with any combination of experiments. The PE method is always superior to the LC method for improvement of the prediction accuracy. From the present study, the followings are found. The experiments on multiplication factor are more applicable to a reaction rate ratio of $$^{238}$$U capture to $$^{239}$$Pu fission (C28/F49) of the target core than the experiments on C28/F49. Combinations of the experiments on multiplication factor is more effective to a void reactivity of the target core than those of the experiments on void reactivity though those on void reactivity are superior to those on multiplication factors in the case of using a single experiment. From these results, we conclude that the experiments on multiplication factor are more effective than the other experiments for all the neutronic characteristics of the target core. From these results, it is concluded that the PE method is promising to complement full mockup experiments for various future nuclear systems by using a number of existing and future benchmark experiments.

Journal Articles

Application of bias factor method with use of exponentiated experimental value to prediction uncertainty reduction in coolant void reactivity of breeding light water reactor

Kugo, Teruhiko; Kojima, Kensuke; Ando, Masaki; Mori, Takamasa; Takeda, Toshikazu*

Journal of Power and Energy Systems (Internet), 2(1), p.73 - 82, 2008/00

We have applied the bias factor method to coolant void reactivity of a breeding light water reactor with use of FCA-XXII-1 experiment with introducing a concept of exponentiated experimental value into the bias factor method in order to overcome a problem caused by the conventional bias factor method in which the prediction uncertainty increases in the case that the experimental core has the opposite reactivity worth and the consequent opposite sensitivity coefficients to the real core. In the present study, we have formulated the prediction uncertainty reduction by the use of the bias factor method extended by the concept of the exponentiated experimental value. From the numerical results, it is verified that the concept of exponentiated experimental value can improve the prediction accuracy compared with the original uncertainty in the design calculation value while the conventional bias factor method cannot improve the prediction accuracy. It is concluded that the introduction of exponentiated experimental value can effectively utilize experimental data and extend applicability of the bias factor method.

Journal Articles

Axial orientation of molecular-beam-epitaxy-grown Fe$$_{3}$$Si/Ge hybrid structures and its degradation

Maeda, Yoshihito; Jonishi, Takafumi*; Narumi, Kazumasa; Ando, Yuichiro*; Ueda, Koji*; Kumano, Mamoru*; Sado, Taizo*; Miyao, Masanobu*

Applied Physics Letters, 91(17), p.171910_1 - 171910_3, 2007/10

 Times Cited Count:29 Percentile:24.07(Physics, Applied)

The axial orientation of molecular-beam-epitaxy (MBE)-grown Fe$$_{3}$$Si(111)/Ge(111) hybrid structures was investigated by Rutherford backscattering spectroscopy. We confirmed that during MBE above 300$$^{circ}$$C, the interdiffusion of Fe and Ge atoms results in a composition change and the epitaxial growth of FeGe in Fe$$_{3}$$Si. Low-temperature ($$<$$200 $$^{circ}$$C) MBE can realize fully ordered DO$$_{3}$$-Fe$$_{3}$$Si with highly axial orientation [minimum yield ($$chi$$$$_{min}$$)=2.2%]. Postannealing above 400 $$^{circ}$$C results in a composition change and the degradation of axial orientation in the off-stoichiometric Fe$$_{3}$$Si. The significance of stoichiometry with regard to thermal stability and the interfacial quality of Fe$$_{3}$$Si(111)/Ge(111) hybrid structures was also discussed.

Journal Articles

A Modular metal-fuel fast reactor with one-loop main cooling system

Chikazawa, Yoshitaka; Okano, Yasushi; Konomura, Mamoru; Sato, Koji; Sawa, Naoki*; Sumita, Hiroyuki*; Nakanishi, Shigeyuki*; Ando, Masato*

Nuclear Technology, 159(3), p.267 - 278, 2007/09

 Times Cited Count:1 Percentile:86.98(Nuclear Science & Technology)

A diversified or modular power source is attractive since it requires a low construction cost per unit and can be demonstrated in small scale experimental facilities. In this study, a new metal fuel sodium cooled reactor with 300MW electric has been developed enhancing cost reduction. And economical potential at demonstration stage with first of a kind (FOAK) is emphasized. A minimum configuration with a compact reactor vessel, a one-loop main cooling system and a simple fuel handling system is adopted enhancing cost reduction. For safety evaluation, reliability of the one-loop main cooling system has been shown by pipe-break transient analyses. Besides, construction cost of a demonstration plant with a first reactor and a small reprocessing and fuel fabrication facility is also evaluated. A major feature of the present concept is that the demonstration reactor and facilities can be directly appropriated for first commercial modules and the power plant can easily increase its capacity adding reactor and electrorefiner modules. A fast reactor cycle commercialization scenario using the present concept is thought to give low R&D or investment risk and high cost performance since the total demonstration plant cost is relatively small and the facilities are directly appropriated to commercial use.

Journal Articles

Low temperature hetero-epitaxy of ferromagnetic silicide on Ge substrates for spin-transistor application

Ando, Yuichiro*; Ueda, Koji*; Kumano, Mamoru*; Sado, Taizo*; Narumi, Kazumasa; Maeda, Yoshihito; Miyao, Masanobu*

Shingaku Giho, 107(111), p.221 - 224, 2007/06

Ferromagnetic silicide Fe$$_{3}$$Si (Currie temperature: 840 K) has three phases (A2, B2, and DO3), where the DO3-type is an ordered phase and calculated to be spin-polarized at the Fermi level. In addition, the lattice constant (0.565 nm) of Fe$$_{3}$$Si is almost completely equal to that (0.565 nm) of Ge. Therefore, atomically controlled epitaxial growth of Fe$$_{3}$$Si is expected on Ge. This will be a powerful tool to realize Ge channel spin transistors with ultrahigh speed operation and ultralow power consumption. This paper reviews our recent progress in novel epitaxial growth of Fe$$_{3}$$Si on Ge for spintronics application.

Journal Articles

Introduction to plasma fusion energy

Takamura, Shuichi*; Kado, Shinichiro*; Fujii, Takashi*; Fujiyama, Hiroshi*; Takabe, Hideaki*; Adachi, Kazuo*; Morimiya, Osamu*; Fujimori, Naoji*; Watanabe, Takayuki*; Hayashi, Yasuaki*; et al.

Kara Zukai, Purazuma Enerugi No Subete, P. 164, 2007/03

no abstracts in English

Journal Articles

Low-temperature epitaxial growth of [Fe$$_{3}$$Si/SiGe]$$_{n}$$ (n = 1-2) multi-layered structures for spintronics application

Sado, Taizo*; Ueda, Koji*; Ando, Yuichiro*; Kumano, Mamoru*; Narumi, Kazumasa; Maeda, Yoshihito; Miyao, Masanobu*

ECS Transactions, 11(6), p.473 - 479, 2007/00

Our recent progresses in epitaxial growth of Fe$$_{3}$$Si on Ge substrates are reviewed. Single crystalline Fe$$_{3}$$Si layers with atomically flat interfaces were achieved on Ge(111) substrates by optimizing growth conditions at low temperatures (60$$sim$$200 $$^{circ}$$C). Thermal stability of it was guaranteed up to 400 $$^{circ}$$C. In addition, epitaxial growth of mixed layers composed of Fe$$_{3}$$Si, FeGe, and FeSi on Ge substrates at 400 $$^{circ}$$C is reported. Finally, epitaxial growth of Fe$$_{3}$$Si/Ge/Fe$$_{3}$$Si/Ge structures is discussed. These results will be a powerful tool to open up SiGe related spintronics.

Journal Articles

Effect of Fe/Si ratio on epitaxial growth of Fe$$_{3}$$Si on Ge substrate

Kumano, Mamoru*; Ando, Yuichiro*; Ueda, Koji*; Sado, Taizo*; Narumi, Kazumasa; Maeda, Yoshihito; Miyao, Masanobu*

ECS Transactions, 11(6), p.481 - 485, 2007/00

The effects of the Fe/Si ratios on molecular beam epitaxy (MBE) of Fe$$_{3}$$Si on Ge substrate have been investigated in a wide range of growth temperatures (60$$sim$$300 $$^{circ}$$C). From XRD measurements, it was found that Fe$$_{3}$$Si layers were epitaxially grown on Ge(111) substrates at 60$$sim$$200 $$^{circ}$$C under the stoichiometric (Fe:Si = 3:1) and non-stoichiometric (Fe:Si = 4:1) conditions. From RBS measurement, it was found that atomic mixing of Fe and Ge at Fe$$_{3}$$Si/Ge interfaces began at a growth temperature of 300 $$^{circ}$$C. In the case of MBE under the stoichiometric condition, the crystallinity of Fe$$_{3}$$Si is significantly improved compared to the non-stoichiometric condition. As a result, very low $$chi$$$$_{min}$$ was obtained in a wide temperature (60$$sim$$200 $$^{circ}$$C) under the stoichiometric condition. From the transmission electron microscopy measurements, it was shown that high-quality DO3-type Fe$$_{3}$$Si/Ge structures with atomically flat interfaces were realized at a low temperature ($$sim$$200 $$^{circ}$$C) under the stoichiometric condition.

Journal Articles

Estimation of photon dose generated by a short pulse high power laser

Hayashi, Yukio; Fukumi, Atsushi*; Matsukado, Koji*; Mori, Michiaki; Kotaki, Hideyuki; Kando, Masaki; Chen, L.-M.; Daito, Izuru; Kondo, Shuji; Kanazawa, Shuhei; et al.

Radiation Protection Dosimetry, 121(2), p.99 - 107, 2006/12

 Times Cited Count:14 Percentile:25.29(Environmental Sciences)

The authors obtain a new equation to estimate the forward component of a photon dose which is generated through the interaction between a target and a short pulse high power laser. As the equation is quite simple, it is useful for calculating the photon dose. The equation shows that the photon dose is proportional to the electron temperature for the range of its temperature $$>$$ 3 MeV, and proportional to square of the electron temperature for the range of its temperature $$<$$ 3 MeV. The dose estimated with this method is roughly consistent with the result of Monte Carlo simulation. On someassumptions and corrections, it can reproduce experimental results obtained and the dose result calculated at other laboratories.

Journal Articles

A Modular metal fuel fast reactor enhancing economic potential

Chikazawa, Yoshitaka; Okano, Yasushi; Konomura, Mamoru; Sato, Koji; Ando, Masato*; Nakanishi, Shigeyuki*; Sawa, Naoki*; Shimakawa, Yoshio*

Proceedings of 2006 International Congress on Advances in Nuclear Power Plants (ICAPP '06) (CD-ROM), 8 Pages, 2006/06

A diversified or modular power source is attractive since it requires a low construction cost per unit and can be demonstrated in small scale experimental facilities. In this study, a new metal fuel sodium cooled reactor with 300MW electric has been developed enhancing cost reduction. And economical potential at demonstration stage with first of a kind (FOAK) is emphasized. A minimum configuration with a compact reactor vessel, a one-loop main cooling system and a simple fuel handling system are adopted enhancing cost reduction within safety requirement. Besides, construction cost of a demonstration plant with a first kind of reactor and a small reprocessing and fuel manufacturing facility is also evaluated. A major feature of the present concept is that the demonstration facilities can be appropriated for commercialized ones since they can be easily commercialize by increasing reactor and electrorefiner modules. A FBR cycle commercialization scenario using the present concept is thought to give low risk and high cost performance since the total demonstration plant cost is relatively small and the facilities are directly appropriated to commercial use.

Journal Articles

Preliminary evaluation of reduction of prediction error in breeding light water reactor core performance

Kugo, Teruhiko; Kojima, Kensuke; Ando, Masaki; Okajima, Shigeaki; Mori, Takamasa; Takeda, Toshikazu*; Kitada, Takanori*; Matsuoka, Shogo*

Proceedings of 2005 International Congress on Advances in Nuclear Power Plants (ICAPP '05) (CD-ROM), 10 Pages, 2005/05

We have preliminarily evaluated the reduction of prediction errors of the core characteristics of the breeding light water reactor core based on the bias factor method by utilizing the FCA critical experiments carried out for MOX fueled tight lattice light water reactor cores. The prediction uncertainty of k$$_{eff}$$ is reduced from 0.62% to 0.39% by utilizing the FCA-XV-2 (65V) result. As for the reaction rate ratio of $$^{238}$$U capture and $$^{239}$$Pu fission, it is found that the FCA XXII-1 (95V) and XV (95V) results are suitable for the upper core and the upper blanket of the real core and the FCA XXII-1 (65V) and XV-2 (65V) results are suitable for the lower core and the internal blanket.

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