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Journal Articles

Improved performance of wide bandwidth neutron-spin polarizer due to ferromagnetic interlayer exchange coupling

Maruyama, Ryuji; Yamazaki, Dai; Aoki, Hiroyuki; Akutsu, Kazuhiro*; Hanashima, Takayasu*; Miyata, Noboru*; Soyama, Kazuhiko; Bigault, T.*; Saerbeck, T.*; Courtois, P.*

Journal of Applied Physics, 130(8), p.083904_1 - 083904_10, 2021/08

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

Journal Articles

Improvement in sputtering rate uniformity over large deposition area of large-scale ion beam sputtering system

Maruyama, Ryuji; Yamazaki, Dai; Akutsu, Kazuhiro*; Hanashima, Takayasu*; Miyata, Noboru*; Aoki, Hiroyuki; Soyama, Kazuhiko

JPS Conference Proceedings (Internet), 33, p.011092_1 - 011092_6, 2021/03

no abstracts in English

Journal Articles

Fine-structure analysis of perhydropolysilazane-derived nano layers in deep-buried condition using polarized neutron reflectometry

Akutsu, Kazuhiro*; Kira, Hiroshi*; Miyata, Noboru*; Hanashima, Takayasu*; Miyazaki, Tsukasa*; Kasai, Satoshi*; Yamazaki, Dai; Soyama, Kazuhiko; Aoki, Hiroyuki

Polymers (Internet), 12(10), p.2180_1 - 2180_10, 2020/10

 Times Cited Count:0 Percentile:0(Polymer Science)

Journal Articles

Effect of the interface roughness correlation on the reflectivity in a neutron multilayer mirror

Maruyama, Ryuji; Yamazaki, Dai; Soyama, Kazuhiko

JPS Conference Proceedings (Internet), 22, p.011011_1 - 011011_5, 2018/11

Neutron multilayer mirrors are one of the most important optical elements for neutron scattering experiments. Good interface quality in terms of sharpness and smoothness plays a critical role in determining the performance of optical elements. We have shown that a multilayer with a large vertical correlation length and small lateral correlation length effectively suppresses the diffuse scattering intensity. In this study, the effect of the interface roughness correlation on the neutron reflectivity of the multilayer mirror is investigated using the reflectivity calculation based on the distorted wave Born approximation.

Journal Articles

Development of high-polarization Fe/Ge neutron polarizing supermirror; Possibility of fine-tuning of scattering length density in ion beam sputtering

Maruyama, Ryuji; Yamazaki, Dai; Akutsu, Kazuhiro*; Hanashima, Takayasu*; Miyata, Noboru*; Aoki, Hiroyuki; Takeda, Masayasu; Soyama, Kazuhiko

Nuclear Instruments and Methods in Physics Research A, 888, p.70 - 78, 2018/04

 Times Cited Count:3 Percentile:45.99(Instruments & Instrumentation)

The multilayer structure of Fe/Si and Fe/Ge systems fabricated by ion beam sputtering (IBS) was investigated using X-ray and polarized neutron reflectivity measurements and scanning transmission electron microscopy with energy-dispersive X-ray analysis. The obtained result revealed that the incorporation of sputtering gas particles (Ar) in the Ge layer gives rise to a marked reduction in the neutron scattering length density (SLD) and contributes to the SLD contrast between the Fe and Ge layers almost vanishing for spin-down neutrons. This leads to a possibility of fine-tuning of the SLD for the IBS, which is required to realize a high polarization efficiency of a neutron polarizing supermirror. Fe/Ge polarizing supermirror with $$m=5$$ fabricated showed a spin-up reflectivity of 0.70 at the critical momentum transfer. The polarization was higher than 0.985 for the $$q_z$$ range where the correction for the polarization inefficiencies of the beamline works properly.

Journal Articles

Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex, 2; Neutron scattering instruments

Nakajima, Kenji; Kawakita, Yukinobu; Ito, Shinichi*; Abe, Jun*; Aizawa, Kazuya; Aoki, Hiroyuki; Endo, Hitoshi*; Fujita, Masaki*; Funakoshi, Kenichi*; Gong, W.*; et al.

Quantum Beam Science (Internet), 1(3), p.9_1 - 9_59, 2017/12

The neutron instruments suite, installed at the spallation neutron source of the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC), is reviewed. MLF has 23 neutron beam ports and 21 instruments are in operation for user programs or are under commissioning. A unique and challenging instrumental suite in MLF has been realized via combination of a high-performance neutron source, optimized for neutron scattering, and unique instruments using cutting-edge technologies. All instruments are/will serve in world-leading investigations in a broad range of fields, from fundamental physics to industrial applications. In this review, overviews, characteristic features, and typical applications of the individual instruments are mentioned.

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

Accessible length scale of the in-plane structure in polarized neutron off-specular and grazing-incidence small-angle scattering measurements

Maruyama, Ryuji; Bigault, T.*; Wildes, A. R.*; Dewhurst, C. D.*; Saerbeck, T.*; Honecker, D.*; Yamazaki, Dai; Soyama, Kazuhiko; Courtois, P.*

Journal of Physics; Conference Series, 862(1), p.012017_1 - 012017_6, 2017/06

 Times Cited Count:6 Percentile:94.5

The in-plane magnetic structure of Fe/Si multilayers with a polycrystalline grain size less than the ferromagnetic exchange length was investigated using polarized neutron off-specular scattering and grazing-incidence small-angle scattering measurements. These complementary measurements, each of them covering different length scales, together with the data analysis based on the distorted wave Born approximation, revealed lateral correlation in the fluctuating orientation of the magnetization in the layer on a sub-$$mu$$m length scale. The obtained in-plane magnetic structure is consistent with the random anisotropy model, i.e. competition between the exchange interactions between neighboring spins and the local magnetocrystalline anisotropy.

Journal Articles

Silver photo-diffusion and photo-induced macroscopic surface deformation of Ge$$_{33}$$S$$_{67}$$/Ag/Si substrate

Sakaguchi, Yoshifumi*; Asaoka, Hidehito; Uozumi, Yuki; Kondo, Keietsu; Yamazaki, Dai; Soyama, Kazuhiko; Ailavajhala, M.*; Mitkova, M.*

Journal of Applied Physics, 120(5), p.055103_1 - 055103_10, 2016/08

 Times Cited Count:9 Percentile:49.94(Physics, Applied)

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:7 Percentile:41.71(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Improvement of exchanging method of neutron startup source of high temperature engineering test reactor

Sawahata, Hiroaki; Shimazaki, Yosuke; Ishitsuka, Etsuo; Yamazaki, Kazunori; Yanagida, Yoshinori; Fujiwara, Yusuke; Takada, Shoji; Shinozaki, Masayuki; Hamamoto, Shimpei; Tochio, Daisuke

Proceedings of 24th International Conference on Nuclear Engineering (ICONE-24) (DVD-ROM), 8 Pages, 2016/06

In the HTTR, $$^{252}$$Cf is loaded in the reactor core as a neutron startup source and changed at frequency. In this exchange work, there were two technical issues; slightly higher radiation exposure of workers by neutron leakage and reliability of neutron source transportation container in handling. To reduce the radiation dose by neutron leakage, detail numerical evaluations using PHITS code were carried out, the effective shielding method for fuel handling machine was proposed. Easily removable polyethylene blocks and particles were used as the neutron shielding, and installed in the cooling paths of the fuel handling machine. As a result, the collective effective dose by neutron was reduced from about 700 man-microSv to about 300 man-microSv. As to the neutron source transportation container, the handling performance was improved and the handling work was safety accomplished by downsizing.

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

Experiments of coolant accumulation in SG U tube and analytical model development

Yamaji, Tatsuya*; Koizumi, Yasuo; Yamazaki, Kohei*; Otake, Hiroyasu*; Hasegawa, Koji*; Onuki, Akira*; Kanamori, Daisuke*

Konsoryu Shimpojiumu 2015 Koen Rombunshu (USB Flash Drive), 2 Pages, 2015/08

Experiments of condensing counter-current two-phase flow in a vertical pipe were performed. This study was intended to examine water accumulation in the up-flow side of steam generator U-tubes of a PWR during the reflux cooling stage of a small break LOCA. It has been apprehended that the water accumulation may result in temporary core liquid level depression. The inner diameter and the length of a test flow channel used in the experiments were 18 mm and 4 m, respectively. The experiments were performed by using steam and water at 0.1 MPa. Two kinds of experiments were conducted; visualization experiments by using a transparent test section and quantitative water accumulation evaluation experiments by using a brass test section. Even if water on the inner surface of the test pipe could not flow downward at the lower portion of the test pipe, a part of water became to flow downward at the upper portion of the test pipe since steam velocity decreased because of condensation. Thus, two-phase mixture level was formed in the upper portion of the test pipe, which resulted in the water accumulation in the pipe. The model to predict the water accumulation was proposed. It predicted the water accumulation reasonably well.

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:8 Percentile:97.27

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

Neutron reflectometers in J-PARC

Yamada, Norifumi*; Takeda, Masayasu; Yamazaki, Dai

Hamon, 24(4), p.288 - 295, 2014/11

no abstracts in English

Journal Articles

Neutron reflectometer

Takeda, Masayasu; Yamazaki, Dai; Hino, Masahiro*

Hamon, 24(3), p.200 - 205, 2014/08

no abstracts in English

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:12 Percentile:66.54(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

Development of a compact vertical splitting system for the cold neutron beam at JRR-3

Tamura, Itaru; Maruyama, Ryuji; Yamazaki, Dai; Nakamura, Kiyoshi; Yamamoto, Kazuyoshi; Aizawa, Kazuya; Soyama, Kazuhiko

Journal of Physics; Conference Series, 528, p.012012_1 - 012012_7, 2014/07

 Times Cited Count:0 Percentile:0.03

To achieve efficient implementation of usage of neutron beam instruments, the instruments were rearranged at C2 cold neutron beam line at JRR-3 by using a newly developed compact vertical splitting system. The splitting system has two compact multi channel benders. The bender has been developed using Ni/Ti supermirrors coated on both sides of 0.2 mm thickness silicon substrates. The curvature radius of the bender is 938 mm and the length of the bender is 320 mm yielding deflection angles of 20$$^{circ}$$. Supermirrors with m=3 were deposited on both sides of silicon substrate by an ion beam sputtering apparatus in JAEA. Neutron flux at the end of the neutron guide that installed at the bender exit of which the deflection angle is 20$$^{circ}$$ was measured by the gold foil activation method. It was measured 1.58 $$times$$ 10$$^{7}$$ n/cm$$^{2}$$/s. The present study showed that the supermirrors coated on both sides with high reflectivity are suitable for the compact bender.

Journal Articles

Shielding study at the Fukui Prefectural Hospital Proton Therapy Center

Satoh, Daiki; Maeda, Yoshikazu*; Tameshige, Yuji*; Nakashima, Hiroshi; Shibata, Tokushi*; Endo, Akira; Tsuda, Shuichi; Sasaki, Makoto*; Maekawa, Motokazu*; Shimizu, Yasuhiro*; et al.

Journal of Nuclear Science and Technology, 49(11), p.1097 - 1109, 2012/11

 Times Cited Count:10 Percentile:65.97(Nuclear Science & Technology)

At the Fukui Prefectural Hospital Proton Therapy Center, neutron doses behind concrete shields and at maze have been measured by using radiation monitors, DARWIN, Wendi-2, a rem meter, and solid state nuclear track detectors. The measured data were compared with the estimations by analytical models and Monte Carlo code PHITS. The analytical model with the parameters employed in shielding design of the facility gave considerably larger estimates than the measured data. This means that the facility was designed with an enough safety margin. The calculation results of PHITS were less than those of the analytical model, and were about 3 times larger than the measured data. From the view point of a safety policy with conservative estimation for shielding design, Monte Carlo simulation is a better tool for estimating radiation safety at accelerator-based proton treatment facilities.

Journal Articles

Intermediate-valence icosahedral Au-Al-Yb quasicrystal

Watanuki, Tetsu; Kashimoto, Shiro*; Kawana, Daichi*; Yamazaki, Teruo*; Machida, Akihiko; Tanaka, Yukinori*; Sato, Taku*

Physical Review B, 86(9), p.094201_1 - 094201_6, 2012/09

 Times Cited Count:54 Percentile:89.78(Materials Science, Multidisciplinary)

A quasiperiodic, intermediate-valence (IV) system is realized in an icosahedral Au-Al-Yb quasicrystal. X-ray absorption spectroscopy near the Yb $$L$$$$_{3}$$-edge indicates that quasiperiodically arranged Yb ions assume a mean valence of 2.61, between a divalent state (4$$f$$$$^{14}$$, $$J$$ = 0) and a trivalent one (4$$f$$$$^{13}$$, $$J$$ = 7/2). Magnetization measurements demonstrate that the 4$$f$$ holes in this quasicrystal have a localized character. The magnetic susceptibility shows a Curie-Weiss behavior above $$sim$$100 K with an effective magnetic moment of 3.81 $$mu$$$$_{rm B}$$ per Yb. Moreover, a crystalline approximant to this quasicrystal is an IV compound. We propose a heterogeneous IV model for the quasicrystal, whereas the crystalline approximant is most likely a homogeneous IV system. At temperatures below $$sim$$10 K, specific heat and magnetization measurements reveal non-Fermi-liquid behavior in both the quasicrystal and its crystalline approximant without either doping, pressure, or field tuning.

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