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JAEA Reports

Status of study of long-term assessment of transport of radioactive contaminants in the environment of Fukushima (FY2018)

Nagao, Fumiya; Niizato, Tadafumi; Sasaki, Yoshito; Ito, Satomi; Watanabe, Takayoshi; Dohi, Terumi; Nakanishi, Takahiro; Sakuma, Kazuyuki; Hagiwara, Hiroki; Funaki, Hironori; et al.

JAEA-Research 2019-002, 235 Pages, 2019/08

JAEA-Research-2019-002.pdf:21.04MB

The accident of the Fukushima Daiichi Nuclear Power Station (hereinafter referred to 1F), Tokyo Electric Power Company Holdings, Inc. occurred due to the Great East Japan Earthquake, Sanriku offshore earthquake, of 9.0 magnitude and the accompanying tsunami. As a result, large amount of radioactive materials was released into the environment. Under these circumstances, JAEA has been conducting Long-term Environmental Dynamics Research concerning radioactive materials released in environment, especially migration behavior of radioactive cesium since November 2012. This report is a summary of the research results that have been obtained in environmental dynamics research conducted by JAEA in Fukushima Prefecture.

Journal Articles

Phase-transition kinetics of magnetic skyrmions investigated by stroboscopic small-angle neutron scattering

Nakajima, Taro*; Inamura, Yasuhiro; Ito, Takayoshi*; Oishi, Kazuki*; Oike, Hiroshi*; Kagawa, Fumitaka*; Kikkawa, Akiko*; Taguchi, Yasujiro*; Kakurai, Kazuhisa*; Tokura, Yoshinori*; et al.

Physical Review B, 98(1), p.014424_1 - 014424_5, 2018/07

 Times Cited Count:3 Percentile:56.62(Materials Science, Multidisciplinary)

We investigated the phase-transition kinetics of magnetic skyrmion lattice (SkL) in MnSi by means of stroboscopic small-angle neutron scattering (SANS). Temporal evolutions of SANS patterns were measured with time resolution of 13 ms while sweeping temperature as fast as 50 Ks$$^{-1}$$. It turned out that the paramagnetic-to-SkL transition immediately occurs upon traversing the equilibrium phase boundary on the rapid cooling, whereas the SkL-to-conical transition can be kinetically avoided to realize the low-temperature metastable SkL with a long-range magnetic order. The formation of the metastable SkL was found to be strongly dependent not only on cooling rate, but also on magnetic eld and trajectory in the H-T phase diagram.

Journal Articles

Stroboscopic time-of-flight neutron diffraction during cyclic testing using the event data recording system at J-PARC

Kawasaki, Takuro; Inamura, Yasuhiro; Ito, Takayoshi*; Nakatani, Takeshi; Harjo, S.; Gong, W.*; Aizawa, Kazuya

Journal of Applied Crystallography, 51(3), p.630 - 634, 2018/06

 Times Cited Count:2 Percentile:54.56(Chemistry, Multidisciplinary)

Journal Articles

High stereographic resolution texture and residual stress evaluation using time-of-flight neutron diffraction

Xu, P. G.; Harjo, S.; Ojima, Mayumi*; Suzuki, Hiroshi; Ito, Takayoshi*; Gong, W.; Vogel, S. C.*; Inoue, Junya*; Tomota, Yo*; Aizawa, Kazuya; et al.

Journal of Applied Crystallography, 51(3), p.746 - 760, 2018/06

 Times Cited Count:10 Percentile:8.83(Chemistry, Multidisciplinary)

Journal Articles

Applications of the differential events reading method at MLF, J-PARC

Inamura, Yasuhiro; Ito, Takayoshi*; Suzuki, Jiro*

Journal of Physics; Conference Series, 1021(1), p.012015_1 - 012015_5, 2018/06

 Times Cited Count:1 Percentile:20.8

An event recording method for data acquisition for neutron scattering and its analysis provides a lot of benefits for the measurement of time-resolved and time transient phenomena. Almost all instruments installed in the Materials and Life Science Experimental Facility (MLF) at J-PARC have adopted this method since the first beam came and have achieved good results. On the other hand, our treatment of event recorded data leaves room for improvements and developments to achieve more effective utilization. This paper introduces one of the applications of the event recording method to achieve the pseudo real-time data treatment in MLF in a simple way.

Journal Articles

Hydrological and climate changes in southeast Siberia over the last 33 kyr

Katsuta, Nagayoshi*; Ikeda, Hisashi*; Shibata, Kenji*; Kokubu, Yoko; Murakami, Takuma*; Tani, Yukinori*; Takano, Masao*; Nakamura, Toshio*; Tanaka, Atsushi*; Naito, Sayuri*; et al.

Global and Planetary Change, 164, p.11 - 26, 2018/05

 Times Cited Count:4 Percentile:41.06(Geography, Physical)

Paleoenvironmental and paleoclimate changes in Siberia were reconstructed by continuous, high-resolution records of chemical compositions from a sediment core retrieved from the Buguldeika Saddle, Lake Baikal, dating back to the last 33 cal. ka BP. The Holocene climate followed by a shift at ca. 6.5 cal. ka BP toward warm and dry, suggesting that the climate system transition from the glacial to interglacial state occurred. In the last glacial period, the deposition of carbonate mud from the Primorsky Range was associated with Heinrich events (H3 and H1) and the Selenga River inflow was caused by meltwater of mountain glaciers in the Khamar-Daban Range. The anoxic bottom-water during Allerod-Younger Dryas was probably a result of weakened ventilation associated with reduced Selenga River inflow and microbial decomposition of organic matters from the Primorsky Range. The rapid decline in precipitation during the early Holocene may have been a response to the 8.2 ka cooling event.

Journal Articles

Materials and Life Science Experimental Facility at the Japan Proton Accelerator Research Complex, 3; Neutron devices and computational and sample environments

Sakasai, Kaoru; Sato, Setsuo*; Seya, Tomohiro*; Nakamura, Tatsuya; To, Kentaro; Yamagishi, Hideshi*; Soyama, Kazuhiko; Yamazaki, Dai; Maruyama, Ryuji; Oku, Takayuki; et al.

Quantum Beam Science (Internet), 1(2), p.10_1 - 10_35, 2017/09

Neutron devices such as neutron detectors, optical devices including supermirror devices and $$^{3}$$He neutron spin filters, and choppers are successfully developed and installed at the Materials Life Science Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC), Tokai, Japan. Four software components of MLF computational environment, instrument control, data acquisition, data analysis, and a database, have been developed and equipped at MLF. MLF also provides a wide variety of sample environment options including high and low temperatures, high magnetic fields, and high pressures. This paper describes the current status of neutron devices, computational and sample environments at MLF.

Journal Articles

Comprehensive study on initial thermal oxidation of GaN(0001) surface and subsequent oxide growth in dry oxygen ambient

Yamada, Takahiro*; Ito, Joyo*; Asahara, Ryohei*; Watanabe, Kenta*; Nozaki, Mikito*; Nakazawa, Satoshi*; Anda, Yoshiharu*; Ishida, Masahiro*; Ueda, Tetsuzo*; Yoshigoe, Akitaka; et al.

Journal of Applied Physics, 121(3), p.035303_1 - 035303_9, 2017/01

 Times Cited Count:31 Percentile:6.97(Physics, Applied)

Initial oxidation of GaN(0001) epilayers and subsequent growth of thermal oxides in dry oxygen ambient were investigated by means of X-ray photoelectron spectroscopy, spectroscopic ellipsometry, atomic force microscopy and X-ray diffraction measurements. It was found that, whereas initial oxide formation tends to saturate at temperatures below 800$$^{circ}$$C, selective growth of small oxide grains proceeds at dislocations in the epilayers, followed by noticeable grain growth leading to rough surface morphology at higher oxidation temperatures. This indicates that oxide growth and its morphology are crucially dependent on the defect density in the GaN epilayers. Structural characterizations also revealed that polycrystalline $$alpha$$- and $$beta$$-phase Ga$$_{2}$$O$$_{3}$$ grains in an epitaxial relation with the GaN substrate are formed from the initial stage of the oxide growth. On the basis of these experimental findings, we also developed a comprehensive model for GaN oxidation mediated by nitrogen removal and mass transport.

Journal Articles

Effect of nitrogen incorporation into Al-based gate insulators in AlON/AlGaN/GaN metal-oxide-semiconductor structures

Asahara, Ryohei*; Nozaki, Mikito*; Yamada, Takahiro*; Ito, Joyo*; Nakazawa, Satoshi*; Ishida, Masahiro*; Ueda, Tetsuzo*; Yoshigoe, Akitaka; Hosoi, Takuji*; Shimura, Takayoshi*; et al.

Applied Physics Express, 9(10), p.101002_1 - 101002_4, 2016/10

 Times Cited Count:25 Percentile:13.13(Physics, Applied)

The superior physical and electrical properties of AlON gate dielectrics on AlGaN/GaN substrates in terms of thermal stability, reliability, and interface quality were demonstrated by direct AlON deposition and subsequent annealing. Nitrogen incorporation into alumina was proven to be beneficial both for suppressing intermixing at the insulator/AlGaN interface and reducing the number of electrical defects in Al$$_{2}$$O$$_{3}$$ films. Consequently, we achieved high-quality AlON/AlGaN/GaN metal-oxide-semiconductor capacitors with improved stability against charge injection and a reduced interface state density as low as 1.2$$times$$10$$^{11}$$ cm$$^{-2}$$eV$$^{-1}$$. The impact of nitrogen incorporation into the insulator was discussed on the basis of experimental findings.

Journal Articles

Synchrotron radiation X-ray photoelectron spectroscopy of Ti/Al ohmic contacts to n-type GaN; Key role of Al capping layers in interface scavenging reactions

Nozaki, Mikito*; Ito, Joyo*; Asahara, Ryohei*; Nakazawa, Satoshi*; Ishida, Masahiro*; Ueda, Tetsuzo*; Yoshigoe, Akitaka; Hosoi, Takuji*; Shimura, Takayoshi*; Watanabe, Heiji*

Applied Physics Express, 9(10), p.105801_1 - 105801_4, 2016/10

 Times Cited Count:4 Percentile:66.57(Physics, Applied)

Interface reactions between Ti-based electrodes and n-type GaN epilayers were investigated by synchrotron radiation X-ray photoelectron spectroscopy. Metallic Ga and thin TiN alloys were formed at the interface by subsequently depositing Al capping layers on ultrathin Ti layers even at room temperature. By comparing results from stacked Ti/Al and single Ti electrodes, the essential role of Al capping layers serving as an oxygen-scavenging element to produce reactive Ti underlayers was demonstrated. Further growth of the metallic interlayer during annealing was observed. A strategy for achieving low-resistance ohmic contacts to n-GaN with low-thermal-budget processing is discussed.

Journal Articles

Processes of silver photodiffusion into Ge-chalcogenide probed by neutron reflectivity technique

Sakaguchi, Yoshifumi*; Asaoka, Hidehito; Uozumi, Yuki; Kawakita, Yukinobu; Ito, Takayoshi*; Kubota, Masato; Yamazaki, Dai; Soyama, Kazuhiko; Sheoran, G.*; Mitkova, M.*

Physica Status Solidi (A), 213(7), p.1894 - 1903, 2016/07

 Times Cited Count:6 Percentile:53.67(Materials Science, Multidisciplinary)

no abstracts in English

JAEA Reports

The User's manual of "Manyo Library" data reduction software framework at MLF, J-PARC

Inamura, Yasuhiro; Ito, Takayoshi*; Suzuki, Jiro*; Nakatani, Takeshi

JAEA-Testing 2016-001, 91 Pages, 2016/06

JAEA-Testing-2016-001.pdf:2.38MB

Manyo Library is a software framework for developing analysis software of neutron scattering data produced at MLF, J-PARC. This software framework is required to work on many instruments in MLF and to include base functions applied to various scientific purposes at beam lines. This framework mainly consists of data containers, which enable to store 1, 2 and 3 dimensional axes data for neutron scattering. Data containers have many functions to calculate four arithmetic operations with errors distribution between containers, to store the meta-data about measurements and to read or write text file. Since Manyo Library is built in C++ language, we' ve introduced the technology to call C++ function from Python environment into the framework. As results, we have already developed a lot of software for data reduction, analysis and visualization, which are utilized widely in beam lines at MLF. This document is the manual for the beginner to touch this framework.

Journal Articles

Measurement of transient photo-induced changes in thin films at J-PARC; Time-resolved neutron reflectivity measurements of silver photo-diffusion into Ge-chalcogenide films

Sakaguchi, Yoshifumi*; Asaoka, Hidehito; Uozumi, Yuki; Kawakita, Yukinobu; Ito, Takayoshi*; Kubota, Masato; Yamazaki, Dai; Soyama, Kazuhiko; Ailavajhala, M.*; Wolf, K.*; et al.

JPS Conference Proceedings (Internet), 8, p.031023_1 - 031023_6, 2015/09

We report recent results of time-resolved neutron reflectivity measurements for silver photo-diffusion into Ge$$_{x}$$S$$_{1-x}$$ (x=0.20, 0.33, 0.40) films performed on BL17 (SHARAKU). It is well known that silver diffuses into Ge-chalcogenide layer by visible light exposure with a distinct diffusion front, where the silver concentration abruptly drops off. Using an event recording system at the Materials and Life Science Experimental Facility, neutron reflectivity profiles were collected with a time-resolution of 30 seconds in the shortest case. It was found from the measurements that a relatively stable Ag-rich phase in the reaction layer is firstly formed, and then, slower diffusion occurs at the interface between Ag-rich and Ag-poor layers. Fourier transform analysis showed that the position of the interface is essentially fixed. This result is in contrast to the previously reported model of silver diffusion that postulates a mechanism involving progression of the diffusion front. The results of the measurements on Ag/Ge-Se films performed on the INTER instrument at ISIS are also reported.

Journal Articles

Thermal strain in superconducting Nb$$_{3}$$Sn strand at cryogenic temperature

Harjo, S.; Kawasaki, Takuro; Hemmi, Tsutomu; Ito, Takayoshi*; Nakamoto, Tatsushi*; Aizawa, Kazuya

JPS Conference Proceedings (Internet), 8, p.031001_1 - 031001_5, 2015/09

Journal Articles

Progress in bulk texture measurement using neutron diffraction

Xu, P. G.; Harjo, S.; Ito, Takayoshi*; Morii, Yukio*; Gong, W.; Suzuki, Hiroshi; Akita, Koichi; Suzuki, Tetsuya*; Tomota, Yo; Lutterotti, L.*

JPS Conference Proceedings (Internet), 8, p.031022_1 - 031022_6, 2015/09

Journal Articles

Dynamics of silver photo-diffusion into Ge-chalcogenide films; Time-resolved neutron reflectometry

Sakaguchi, Yoshifumi*; Asaoka, Hidehito; Uozumi, Yuki; Kawakita, Yukinobu; Ito, Takayoshi*; Kubota, Masato; Yamazaki, Dai; Soyama, Kazuhiko; Ailavajhala, M.*; Latif, M. R.*; et al.

Journal of Physics; Conference Series, 619(1), p.012046_1 - 012046_4, 2015/06

 Times Cited Count:7 Percentile:2.2

We report the results of time-resolved neutron reflectivity measurements of Ag/a- Ge$$_{20}$$S$$_{80}$$/Si and a- Ge$$_{40}$$Se$$_{60}$$/Ag/ Si films taken while the films are exposed to visible light. Silver diffuses into an amorphous (a-) chalcogenide layer while visible light illuminates Ag/a-chalcogenide films. Neutron reflectometry is a suitable technique probing time evolution of the multi-layer structure without damaging the sample by the probe beam itself. It was found from the measurements of Ag/a-Ge$$_{20}$$S$$_{80}$$/Si films that a relatively stable Ag-rich phase in the reaction layer is first formed, and then, slower diffusion occurs at the interface between Ag-rich and Ag-poor layers. This result is in contrast to the previously reported model of silver diffusion that suggests a mechanism involving progression of the diffusion front. From the measurements of a-Ge$$_{40}$$Se$$_{60}$$/Ag/ Si films, we found enormous changes in the neutron reflectivity profile, including loss of total reflection region, with continuous illumination even after forming one homogeneous layer, which was about 60 min after starting illumination. At this stage, clear off-specular scattering was observed by a linear detector and a surface roughness was observed with naked eyes.

Journal Articles

Studies of silver photo diffusion dynamics in Ag/Ge$$_{x}$$S$$_{1-x}$$ ($$x$$=0.2 and 0.4) films using neutron reflectometry

Sakaguchi, Yoshifumi*; Asaoka, Hidehito; Uozumi, Yuki; Kawakita, Yukinobu; Ito, Takayoshi*; Kubota, Masato; Yamazaki, Dai; Soyama, Kazuhiko; Ailavajhala, M.*; Latif, R.*; et al.

Canadian Journal of Physics, 92(7/8), p.654 - 658, 2014/07

 Times Cited Count:11 Percentile:33.79(Physics, Multidisciplinary)

We report our recent results of neutron reflectivity measurements for Ag/a-Ge $$_{x}$$S$$_{1-x}$$ (x=0.2, 0.4) films under light illumination. The neutron reflectivity measurements have been performed on a polarized neutron reflectometer (BL17, SHARAKU) at Japan Proton Accelerator Research Complex (J-PARC), Japan. By using the time-of flight instrument with intensive pulsed neutrons produced by 300kW proton beams, time evolution of the neutron reflectivity under a light illumination has been revealed, with at least 2-min time resolution. From the detailed analysis, it was found for Ag 50nm/Ge $$_{40}$$S $$_{60}$$ 150nm films under a light illumination from the Ag layer side that there are two types of diffusion processes: a fast change observed in the first 10 min after illumination using a xenon lamp, which is then followed by a slow change observed after a 1 hour of additional light exposure. The result indicates that there is a comparatively stable (metastable) state in the Ag-doped Ge $$_{40}$$S $$_{60}$$ layer in terms of Ag composition, and the next silver diffusion process occurs by affecting the Ag-doped Ge $$_{40}$$S $$_{60}$$ layer / interface. This coincides with the Ge $$_{40}$$S $$_{60}$$ results of Wagner et al. obtained for Ag/As-S films. These results are also in accord with the results reported by some of us by modeling of the Ag transport in Ge-Se glass showing the presence of slow and fast moving Ag ions. Our result demonstrated that the idea of a two-step reaction process can be applied to Ge-chalcogenide system. We also discuss illumination-side dependence and Ge-composition dependence of reaction process.

Journal Articles

Engineering & Related Studies at J-PARC

Harjo, S.; Aizawa, Kazuya; Abe, Jun*; Gong, W.; Ito, Takayoshi*; Kawasaki, Takuro; Iwahashi, Takaaki

Materials Science Forum, 777, p.12 - 18, 2014/04

 Times Cited Count:0 Percentile:100

Journal Articles

Residual strains in ITER conductors by neutron diffraction

Harjo, S.; Hemmi, Tsutomu; Abe, Jun; Gong, W.; Nunoya, Yoshihiko; Aizawa, Kazuya; Ito, Takayoshi*; Koizumi, Norikiyo; Machiya, Shutaro*; Osamura, Kozo*

Materials Science Forum, 777, p.84 - 91, 2014/02

 Times Cited Count:2 Percentile:17.26

Journal Articles

Preparation of polymer gel dosimeters based on less toxic monomers and gellan gum

Hiroki, Akihiro; Sato, Yuichi*; Nagasawa, Naotsugu; Ota, Akio*; Seito, Hajime; Yamabayashi, Hisamichi*; Yamamoto, Takayoshi*; Taguchi, Mitsumasa; Tamada, Masao; Kojima, Takuji

Physics in Medicine and Biology, 58(20), p.7131 - 7141, 2013/10

 Times Cited Count:15 Percentile:37.47(Engineering, Biomedical)

156 (Records 1-20 displayed on this page)