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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

Identification of coral spawn source areas around Sekisei Lagoon for recovery and poleward habitat migration by using a particle-tracking model

Takeda, Naoya*; Kashima, Motohiko*; Odani, Sachika*; Uchiyama, Yusuke*; Kamidaira, Yuki; Mitarai, Satoshi*

Scientific Reports (Internet), 11(1), p.6963_1 - 6963_10, 2021/03

 Times Cited Count:0 Percentile:0.01(Multidisciplinary Sciences)

A massive coral bleaching event occurred in 2016 in the interior of Japan's largest coral lagoon, the Sekisei Lagoon, located in the Kuroshio upstream region in southwestern Japan. Recovery of the coral lagoon will require the influx of coral spawn and larvae; therefore, it is important to identify and conserve source sites. A surface particle tracking simulation of coral spawn and larvae was used to identify source areas in the exterior Sekisei Lagoon for restoration of the interior lagoon. The northern coastal zone of Iriomote Island, including Hatoma Island, was identified as a major source area. Hatoma Island was also identified as a key source for the Kuroshio downstream region, making it one of the most important source areas in the Nansei Archipelago.

Journal Articles

High temperature gas-cooled reactors

Takeda, Tetsuaki*; Inagaki, Yoshiyuki; Aihara, Jun; Aoki, Takeshi; Fujiwara, Yusuke; Fukaya, Yuji; Goto, Minoru; Ho, H. Q.; Iigaki, Kazuhiko; Imai, Yoshiyuki; et al.

High Temperature Gas-Cooled Reactors; JSME Series in Thermal and Nuclear Power Generation, Vol.5, 464 Pages, 2021/02

As a general overview of the research and development of a High Temperature Gas-cooled Reactor (HTGR) in JAEA, this book describes the achievements by the High Temperature Engineering Test Reactor (HTTR) on the designs, key component technologies such as fuel, reactor internals, high temperature components, etc., and operational experience such as rise-to-power tests, high temperature operation at 950$$^{circ}$$C, safety demonstration tests, etc. In addition, based on the knowledge of the HTTR, the development of designs and component technologies such as high performance fuel, helium gas turbine and hydrogen production by IS process for commercial HTGRs are described. These results are very useful for the future development of HTGRs. This book is published as one of a series of technical books on fossil fuel and nuclear energy systems by the Power Energy Systems Division of the Japan Society of Mechanical Engineers.

Journal Articles

Structure of nitride layer formed on titanium alloy surface by N$$_{2}$$-gas exposure at high temperatures

Takeda, Yusuke; Iida, Kiyoshi*; Sato, Shinji*; Matsuo, Tadatoshi*; Nagashima, Yasuyuki*; Okubo, Nariaki; Kondo, Keietsu; Hirade, Tetsuya

JPS Conference Proceedings (Internet), 25, p.011023_1 - 011023_3, 2019/03

In this study, we prepared samples under two different conditions, (1) 810$$^{circ}$$C, for 600 min, and (2) 850$$^{circ}$$C, for 720 min. A depth-profile analysis of the surfaces of the samples is conducted through Doppler broadening (DB) measurements of positron annihilation $$gamma$$ rays using a slow positron beam. It was indicated that many of positrons annihilated in defects near the surface. According to the TEM image, there are nano-crystal grains near the surface and then positrons can diffuse in the grains and annihilate in defects at the grain boundaries. Furthermore, DB measurements indicated that there is a depth dependence on the chemical composition where positrons annihilate. EDS spectroscopy measurements also indicated that there is a depth dependence of impurities such as Vanadium. These results indicated change of the chemical composition at the grain boundaries.

Journal Articles

First ionization potentials of Fm, Md, No, and Lr; Verification of filling-up of 5f electrons and confirmation of the actinide series

Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Beerwerth, R.*; Kaneya, Yusuke*; Makii, Hiroyuki; Mitsukai, Akina*; Nagame, Yuichiro; Osa, Akihiko; Toyoshima, Atsushi; et al.

Journal of the American Chemical Society, 140(44), p.14609 - 14613, 2018/11

 Times Cited Count:16 Percentile:70.21(Chemistry, Multidisciplinary)

The first ionization potential (IP$$_1$$) yields information on valence electronic structure of an atom. IP$$_1$$ values of heavy actinides beyond einsteinium (Es, Z = 99), however, have not been determined experimentally so far due to the difficulty in obtaining these elements on scales of more than one atom at a time. Recently, we successfully measured IP$$_1$$ of lawrencium (Lr, Z = 103) using a surface ionization method. The result suggests that Lr has a loosely-bound electron in the outermost orbital. In contrast to Lr, nobelium (No, Z = 102) is expected to have the highest IP$$_1$$ among the actinide elements owing to its full-filled 5f and the 7s orbitals. In the present study, we have successfully determined IP$$_1$$ values of No as well as fermium (Fm, Z = 100) and mendelevium (Md, Z = 101) using the surface ionization method. The obtained results indicate that the IP$$_1$$ value of heavy actinoids would increase monotonically with filling electrons up in the 5f orbital like heavy lanthanoids.

Journal Articles

A Failure investigation of the beam collimator system in the J-PARC 3 GeV rapid cycling synchrotron

Okabe, Kota; Yamamoto, Kazami; Kamiya, Junichiro; Takayanagi, Tomohiro; Yamamoto, Masanobu; Yoshimoto, Masahiro; Takeda, Osamu*; Horino, Koki*; Ueno, Tomoaki*; Yanagibashi, Toru*; et al.

Proceedings of 14th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.853 - 857, 2017/12

The most important issue is to reduce the uncontrolled beam loss in the high intensity hadron accelerator such as J-PARC proton accelerators. The J-PARC 3 GeV Synchrotron (RCS) has a collimator system which narrows a high intensity beam in the RCS. After startup of RCS in 2007, the collimator system of the RCS worked well. However, in April 2016, vacuum leakage at the collimator system occurred during the maintenance operation. To investigate a cause of the failure, we took apart iron shields of the collimator reducing exposed dose of operators. As a result of inspection, we succeeded to identify the cause of the vacuum leakage failure. In this presentation, we report the failure investigation of the beam collimator system in the RCS.

Journal Articles

Structure of nitride layer formed on titanium alloy surface by N$$_{2}$$-gas exposure at high temperatures

Takeda, Yusuke; Iida, Kiyoshi*; Sato, Shinji*; Matsuo, Tadatoshi*; Nagashima, Yasuyuki*; Okubo, Nariaki; Kondo, Keietsu; Hirade, Tetsuya

Journal of Physics; Conference Series, 791(1), p.012022_1 - 012022_4, 2017/02

 Times Cited Count:1 Percentile:49.45

Titanium alloy is widely used for applications such as golf club heads and structural materials for aircrafts. The surface can be exceedingly hardened by nitriding treatment that initiates defects, but there are some difficulties on use of titanium nitride because the layer can be exfoliated by stress. Therefore, we prepared samples in two different treatment conditions, (1) 810$$^{circ}$$C 600 min and (2) 850$$^{circ}$$C 720 min and performed depth profile analysis of Doppler broadening of positron annihilation $$gamma$$-rays (DB) for these samples. According to a calculation of nitrogen diffusion depth, the nitride layer should be only about 0.05-0.1$$mu$$m. However, the depth profile analysis of the DB measurement indicated that the defects introduced by nitriding treatment extended to a depth of 0.5$$mu$$m.

Journal Articles

Vacuum chromatography of Tl on SiO$$_{2}$$ at the single-atom level

Steinegger, P.*; Asai, Masato; Dressler, R.*; Eichler, R.*; Kaneya, Yusuke*; Mitsukai, Akina*; Nagame, Yuichiro; Piguet, D.*; Sato, Tetsuya; Sch$"a$del, M.; et al.

Journal of Physical Chemistry C, 120(13), p.7122 - 7132, 2016/04

 Times Cited Count:18 Percentile:63.22(Chemistry, Physical)

A new experimental method "vacuum chromatography" has been developed to measure adsorption enthalpy of superheavy elements, and its feasibility has been examined using short-lived thallium isotopes. The short-lived thallium isotopes were produced at the JAEA tandem accelerator. The thallium ion beam prepared with an on-line isotope separator which ionized and mass-separated the thallium isotopes was injected into an isothermal vacuum chromatography apparatus. A temperature-dependent adsorption property of thallium atom on SiO$$_{2}$$ surface were measured. The adsorption enthalpy of thallium was determined to be 158 kJ/mol. The thallium is a homolog of element 113. Thus, the vacuum chromatography developed in this study enables us to perform chemical experiments for short-lived superheavy elements with half-lives of a order of one second.

Journal Articles

R&D on major components of control system for ITER blanket maintenance equipment

Takeda, Nobukazu; Kakudate, Satoshi; Matsumoto, Yasuhiro; Kozaka, Hiroshi; Aburadani, Atsushi; Negishi, Yusuke; Nakahira, Masataka*; Tesini, A.*

Fusion Engineering and Design, 85(7-9), p.1190 - 1195, 2010/12

 Times Cited Count:1 Percentile:11(Nuclear Science & Technology)

Several R&Ds for the ITER blanket remote handling system had been performed from the Engineering Design Activity phase until now and only several technical issues regarding the control system remained such as noise caused by slip ring, control of cable handling system, signal transmission through very long cable and radiation-hard amplifier. This study concentrates on these issues. As a conclusion, major issues for the control system have been solved and the ITER blanket remote handling system becomes further feasible.

Journal Articles

Observation of itinerant Ce 4$$f$$ electronic states in CeIrSi$$_3$$ studied by angle-resolved Ce 3$$drightarrow 4f$$ resonance photoemission spectroscopy

Okochi, Takuo*; Toshimitsu, Takafumi*; Yamagami, Hiroshi; Fujimori, Shinichi; Yasui, Akira; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Miyauchi, Yuichiro*; et al.

Journal of the Physical Society of Japan, 78(8), p.084802_1 - 084802_6, 2009/08

 Times Cited Count:8 Percentile:50.92(Physics, Multidisciplinary)

We have applied angle-resolved Ce 3$$d{rightarrow}$$4$$f$$ resonance photoemission spectroscopy to the non-centrosymmetric pressure-induced superconductor CeIrSi$$_3$$ and obtained the 4$$f$$ band-structure and Fermi surfaces. We have found that the Ce 4$$f$$ states are located mainly near the Fermi level and that the photoemission intensity derived from the dispersive conduction bands across the Fermi level shows considerable resonant enhancement. In addition, the band structure and Fermi surfaces of CeIrSi$$_3$$ are different from those of the non-$$f$$ reference compound, LaIrSi$$_3$$ and the difference is well explained by the band structure calculated within the local density approximation (LDA). These results strongly suggest that the Ce 4$$f$$ electrons in CeIrSi$$_3$$ are well hybridized with conduction bands and form itinerant electronic states.

Journal Articles

Formation of amorphous graded structure in Bi$$_{3}$$Pb$$_{7}$$ intermetallic compounds under strong gravitational field

Mashimo, Tsutomu; Iguchi, Yusuke*; Bagum, R.*; Sano, Tomokazu*; Takeda, Shingo*; Kimura, Shigeru*; Sakata, Osami*; Ono, Masao; Okayasu, Satoru; Tsurui, Takao*; et al.

Defect and Diffusion Forum, 289-292, p.357 - 360, 2009/04

A visible four-layers structure with anomalous nano-sturucture was formed from a homogeneous e-phase Bi$$_{3}$$Pb$$_{7}$$ intermetallic compound under a strong gravitational field (1.02$$times$$10$$^{6}$$ G, 130$$^{circ}$$C, 100 hours). In the 4th layer (lowest-gravity region), pure Bi particles precipitate. In the 2nd 3rd layers, composition graded structures, where Pb content increased along the gravity direction, were formed. It was found that the very broad XRD peak appeared in the 2nd layer, which indicated that an amorphous structure was contained.

Journal Articles

The de Haas-van Alphen oscillation and fermi surface properties of YCu$$_2$$Si$$_2$$

Nguyen, D.; Matsuda, Tatsuma; Ikeda, Shugo*; Yamamoto, Etsuji; Haga, Yoshinori; Takeda, Yuji*; Endo, Toyoaki*; Doi, Yusuke*; Settai, Rikio*; Harima, Hisatomo*; et al.

Journal of the Physical Society of Japan, 77(9), p.094702_1 - 094702_6, 2008/09

 Times Cited Count:13 Percentile:62.96(Physics, Multidisciplinary)

We have succeeded in growing a high-quality single crystal of a non-4$$f$$ reference compound YCu$$_2$$Si$$_2$$ for a heavy-fermion superconductor CeCu$$_2$$Si$$_2$$, and observed the de Haas-van Alphen (dHvA) oscillation. The detected dHvA branches in YCu$$_2$$Si$$_2$$ indicate that the Fermi surfaces are multiply connected, and the dHvA frequencies are in the range from 9$$times10^6$$ to 2$$times10^8$$ Oe. These dHvA branches are found to be well explained by the results of energy band calculations. The corresponding cyclotron masses are light, ranging from 0.4 to 1.5 $$m_0$$, and are consistent with the electronic specific heat coefficient of 2.2 mJ/K$$^2cdot$$mol.

Journal Articles

Magnetic and superconducting properties of LaIrSi$$_3$$ and CeIrSi$$_3$$ with the non-centrosymmetric crystal structure

Okuda, Yusuke*; Miyauchi, Yuichiro*; Ida, Yuki*; Takeda, Yuji*; Tonohiro, Chie*; Ozuchi, Yasuhiro*; Yamada, Tsutomu*; Nguyen, D.; Matsuda, Tatsuma; Haga, Yoshinori; et al.

Journal of the Physical Society of Japan, 76(4), p.044708_1 - 044708_11, 2007/04

 Times Cited Count:78 Percentile:91.73(Physics, Multidisciplinary)

Single crystals of LaIrSi$$_3$$ and CeIrSi$$_3$$ were grown by the Czochralski pulling method in a tetra-arc furnace and the magnetic and superconducting properties, together with super- conductivity in CeIr$$_{1-x}$$Co$$_x$$Si$$_3$$, were clarified by measuring the electrical resistivity, specific heat, magnetic susceptibility, magnetization and de Haas-van Alphen (dHvA) effect. From the results of the dHvA experiment for LaIrSi$$_3$$, the Fermi surface is found to split into two Fermi surfaces due to the spin-orbit interaction arising from the non-centrosymmetric crystal structure. The electronic state of CeIrSi$$_3$$ is tuned from the antiferro- magnetic state to the superconducting state by applying pressure. The upper critical field H$$_{c2}$$(0) at a pressure of 2.65 GPa is found to be highly anisotropic. Large magnitude and anisotropy of H$$_{c2}$$(0) in CeIrSi$$_3$$ are consistent with the theoretical prediction for superconductivity in the non-centrosymmetric crystal structure.

Journal Articles

Polarization transfer in the $$^{16}$$O($$p,p'$$) reaction at forward angles and structure of the spin-dipole resonances

Kawabata, Takahiro*; Ishikawa, Takatsugu*; Ito, M.*; Nakamura, M.*; Sakaguchi, Harutaka*; Takeda, H.*; Taki, T.*; Uchida, Makoto*; Yasuda, Yusuke*; Yosoi, Masaru*; et al.

Physical Review C, 65(6), p.064316_1 - 064316_12, 2002/06

 Times Cited Count:18 Percentile:68.54(Physics, Nuclear)

no abstracts in English

JAEA Reports

Development of fabrication technology for ITER vacuum vessel

Nakahira, Masataka; Shibanuma, Kiyoshi; Kajiura, Soji*; Shibui, Masanao*; Koizumi, Koichi; Takeda, Nobukazu; Kakudate, Satoshi; Taguchi, Ko*; Oka, Kiyoshi; Obara, Kenjiro; et al.

JAERI-Tech 2002-029, 27 Pages, 2002/03


The ITER vacuum vessel (VV) R&D has progressed with the international collaborative efforts by the Japan, Russia and US Parties during the Engineering Design Activities (EDA). Fabrication and testing of a full-scale VV sector model and a port extension have yielded critical information on the fabrication and assembly technologies of the vacuum vessel, magnitude of welding distortions, dimensional accuracy and achievable tolerances during sector fabrication and field assembly. In particular, the dimensional tolerances of $$pm$$3 mm for VV sector fabrication and $$pm$$10 mm for VV sector field assembly have been achieved and satisfied the requirements of $$pm$$5 mm and $$pm$$20 mm, respectively. Also, the basic feasibility of the remote welding robot has been demonstrated. This report presents detailed fabrication and assembly technologies such as welding technology applicable to the thick wall without large distortion, field joint welding technology between sectors and remote welding technology through the VV R&D project.

Journal Articles

Giant monopole resonances in deformed nuclei

Ito, M.*; Sakaguchi, Harutaka*; Ishikawa, Takatsugu*; Kawabata, Takahiro*; Murakami, Tetsuya*; Takeda, H.*; Taki, T.*; Tsukahara, N.*; Uchida, Makoto*; Yasuda, Yusuke*; et al.

Nuclear Physics A, 687(1-2), p.52c - 57c, 2001/04

no abstracts in English

Journal Articles

Thin ice target for $$^{16}$$O (p,p') experiment

Kawabata, Takahiro*; Akimune, Hidetoshi*; Fujimura, Hisako*; Fujita, Hirohiko*; Fujita, Yoshitaka*; Fujiwara, Mamoru; Hara, Keigo*; Hatanaka, Kichiji*; Hosono, K.*; Ishikawa, Takatsugu*; et al.

Nuclear Instruments and Methods in Physics Research A, 459(1-2), p.171 - 176, 2001/02

 Times Cited Count:17 Percentile:76.5(Instruments & Instrumentation)

no abstracts in English

Oral presentation

Electronic structure of CeIrSi$$_3$$ studied by angle-resolved resonant photoemission spectroscopy

Toshimitsu, Takafumi; Okochi, Takuo; Yasui, Akira; Kobayashi, Masaki*; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi*; Yamagami, Hiroshi*; Miyauchi, Yuichiro*; et al.

no journal, , 

We performed angle-resolved resonant photoemission spectroscopy on CeIrSi$$_3$$. CeIrSi$$_3$$ is said to be the superconductor which lacks inversion symmetry and therefore the measurements of electronic conductivity, magnetoresistance, dHvA, and so on, have been made on so far. In this study, we observed extremely clear 4$$f$$ derived band dispersions and Fermi surfaces. By these obtained profiles and comparison with those predicted by LDA calculation, Ce 4$$f$$ electrons in CeIrSi$$_3$$ have relatively itinerant electronic states.

Oral presentation

Electronic structure of CeIrSi$$_{3}$$ and LaIrSi$$_{3}$$ by angle-resolved photoemission spectroscopy

Toshimitsu, Takafumi; Okochi, Takuo; Yasui, Akira; Kobayashi, Masaki*; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi; Yamagami, Hiroshi; Miyauchi, Yuichiro*; et al.

no journal, , 

no abstracts in English

Oral presentation

4f band structure and Fermi surfaces of CeIrSi$$_3$$ by soft X-ray angle-resolved resonant photoemission spectroscopy

Okochi, Takuo; Yasui, Akira; Takeda, Yukiharu; Okane, Tetsuo; Saito, Yuji; Fujimori, Atsushi*; Yamagami, Hiroshi; Miyauchi, Yuichiro*; Okuda, Yusuke*; Settai, Rikio*; et al.

no journal, , 

We have investigated the bulk 4$$f$$ electronic structure of the non-centrosymmetric superconductor, CeIrSi$$_3$$ by soft X-ray angle-resolved photoemission spectroscopy. We have performed the angle-resolved 3$$d$$-4$$f$$ resonant photoemission and the comparison of the angle-resolved photoemission spectra of CeIrSi$$_3$$ with those of non-$$f$$ reference compound, LaIrSi$$_3$$ and revealed that the 4$$f$$ states of CeIrSi$$_3$$ well hybridized with the non-$$f$$ conduction bands.

33 (Records 1-20 displayed on this page)