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Journal Articles

XAFS analysis of ruthenium in simulated iron phosphate radioactive waste glass

Okamoto, Yoshihiro; Kobayashi, Hidekazu; Shiwaku, Hideaki; Sasage, Kenichi; Hatakeyama, Kiyoshi*; Nagai, Takayuki

Journal of Non-Crystalline Solids, 551, p.120393_1 - 120393_8, 2021/01

The chemical state of ruthenium in simulated iron phosphate radioactive waste glass was investigated by conventional X-ray absorption fine structure (XAFS) and imaging XAFS analyses. The EXAFS analysis suggested that ruthenium was contained as glass phase when content of the waste components was less than 10wt.% in 30 mol%Fe$$_{2}$$O$$_{3}$$-P$$_{2}$$O$$_{5}$$ base glass. In other samples, crystalline RuO$$_{2}$$ was predominant. According to the imaging XAFS analysis, RuO$$_{2}$$ particles in all samples had length smaller than 50$$mu$$m. Aggregations of RuO$$_{2}$$, which are found in nuclear waste borosilicate glass, were not seen in any of the iron phosphate glass samples.

Journal Articles

Pressure wave induced sound measurement for diagnosing the operation status of the J-PARC pulsed spallation neutron source

Naoe, Takashi; Kogawa, Hiroyuki; Wakui, Takashi; Teshigawara, Makoto; Haga, Katsuhiro; Futakawa, Masatoshi

Nuclear Instruments and Methods in Physics Research A, 982, p.164566_1 - 164566_6, 2020/12

 Times Cited Count:0

A liquid mercury target for the spallation neutron source is installed in the J-PARC. The liquid mercury is enclosed with the multi-walled stainless steel vessel. At the time of highly intense proton beams hits the target at a repetition rate of 25 Hz, pressure waves, that causes cavitation erosion, are generated owing the rapidly thermal expansion of mercury. We have installed the target diagnostic system consisting of a laser Doppler vibrometer (LDV) and a dynamic microphone to remotely investigate the structural integrity of the target under high-radiation environment. In this study, aiming to understand correlation between the acoustic vibration and the operation conditions such as the proton beam power and beam profile, proton beam induced acoustic vibration was measured by parametrically changing the target operation conditions. The result showed that the sound is well correlated with the operation conditions.

Journal Articles

Nanoscale structural analysis of Bi$$_{0.5}$$Na$$_{0.5}$$TiO$$_3$$

Yoneda, Yasuhiro; Noguchi, Yuji*

Japanese Journal of Applied Physics, 59(SP), p.SPPA01_1 - SPPA01_7, 2020/11

 Times Cited Count:0 Percentile:100(Physics, Applied)

We investigate A-site cation ordering in the ferroelectric perovskite Bi$$_{0.5}$$Na$$_{0.5}$$TiO$$_3$$ (BNT) by synchrotron X-ray total scattering. Although BNT has a problem of a low depolarization temperature, it is promising a lead-free piezoelectric material. Since the depolarization temperature is presumed to correspond to a relaxer like gradual order-disorder phase transition, local structure analysis is necessary to understand the structure of the diorder phase. Through this approach, the elusive connection between chemical heterogeneity and structural heterogeneity is revealed. Because of the large randomness, the Ti off-center shift is averaged out beyond the unit cell and the structure becomes very close to the average structure beyond the unit cell.

Journal Articles

Coexistence of two components in magnetic excitations of La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ ($$x$$ = 0.10 and 0.16)

Sato, Kentaro*; Ikeuchi, Kazuhiko*; Kajimoto, Ryoichi; Wakimoto, Shuichi; Arai, Masatoshi*; Fujita, Masaki*

Journal of the Physical Society of Japan, 89(11), p.114703_1 - 114703_7, 2020/11

 Times Cited Count:0

Journal Articles

Anomalous magnetic anisotropy and magnetic nanostructure in pure Fe induced by high-pressure torsion straining

Oba, Yojiro; Adachi, Nozomu*; Todaka, Yoshikazu*; Gilbert, E. P.*; Mamiya, Hiroaki*

Physical Review Research (Internet), 2(3), p.033473_1 - 033473_6, 2020/11

Journal Articles

Conceptual design of an abnormality sign determination system for the general control system of the Materials and Life Science Experimental Facility at J-PARC

Sakai, Kenji; Oi, Motoki; Teshigawara, Makoto; Naoe, Takashi; Haga, Katsuhiro; Watanabe, Akihiko*

Journal of Neutron Research, 22(2-3), p.337 - 343, 2020/10

For operating a spallation neutron source and a muon target safely and efficiently, a general control system (GCS) operates within Materials and Life Science Experimental Facility (MLF). GCS administers operation and interlock processes of many instruments under various operation status. Since the first beam injection in 2008, it has operated stably without any serious troubles for more than ten years. GCS has a data storage server storing operational data on status around target stations. It has functioned well to detect and investigate unusual situations by checking data in this server. For continuing stable operation of MLF in future, however, introduction of abnormality sign determination system (ASDS) will be necessary for picking up potential abnormalities of target stations caused by radiation damages, time-related deterioration and so on. It will judge abnormalities from slight state transitions of target stations based on analysis with various operational data throughout proton beams, target stations, and secondary beams during long-term operations. This report mentions present status of GCS, conceptual design of ASDS, and installation of an integral data storage server which can deal with various data for ASDS integrally.

Journal Articles

Energy resolution and neutron flux of the 4SEASONS spectrometer revisited

Kajimoto, Ryoichi; Nakamura, Mitsutaka; Iida, Kazuki*; Kamazawa, Kazuya*; Ikeuchi, Kazuhiko*; Inamura, Yasuhiro; Ishikado, Motoyuki*

Journal of Neutron Research, 22(2-3), p.99 - 107, 2020/10

Journal Articles

Distance-selected topochemical dehydro-diels-alder reaction of 1,4-Diphenylbutadiyne toward crystalline graphitic nanoribbons

Zhang, P.*; Tang, X.*; Wang, Y.*; Wang, X.*; Gao, D.*; Li, Y.*; Zheng, H.*; Wang, Y.*; Wang, X.*; Fu, R.*; et al.

Journal of the American Chemical Society, 142(41), p.17662 - 17669, 2020/10

 Times Cited Count:0

Solid-state topochemical polymerization (SSTP) is a promising method to construct functional crystalline polymeric materials, but in contrast to various reactions that happen in solution, only very limited types of SSTP reactions are reported. Diels-Alder (DA) and dehydro-DA (DDA) reactions are textbook reactions for preparing six-membered rings in solution but are scarcely seen in solid-state synthesis. Here, using multiple cutting-edge techniques, we demonstrate that the solid 1,4-diphenylbutadiyne (DPB) undergoes a DDA reaction under 10-20 GPa with the phenyl as the dienophile. The crystal structure at the critical pressure shows that this reaction is "distance-selected". The distance of 3.2${AA}$ between the phenyl and the phenylethynyl facilitates the DDA reaction, while the distances for other DDA and 1,4-addition reactions are too large to allow the bonding. The obtained products are crystalline armchair graphitic nanoribbons, and hence our studies open a new route to construct the crystalline carbon materials with atomic-scale control.

Journal Articles

Development and application of a $$^3$$He neutron spin filter at J-PARC

Okudaira, Takuya; Oku, Takayuki; Ino, Takashi*; Hayashida, Hirotoshi*; Kira, Hiroshi*; Sakai, Kenji; Hiroi, Kosuke; Takahashi, Shingo*; Aizawa, Kazuya; Endo, Hitoshi*; et al.

Nuclear Instruments and Methods in Physics Research A, 977, p.164301_1 - 164301_8, 2020/10

 Times Cited Count:0 Percentile:100(Instruments & Instrumentation)

Journal Articles

Insight into Kondo screening in the intermediate-valence compound SmOs$$_4$$Sb$$_{12}$$ uncovered by soft X-ray magnetic circular dichroism

Saito, Yuji; Fujiwara, Hidenori*; Yasui, Akira*; Kadono, Toshiharu*; Sugawara, Hitoshi*; Kikuchi, Daisuke*; Sato, Hideyuki*; Suga, Shigemasa*; Yamasaki, Atsushi*; Sekiyama, Akira*; et al.

Physical Review B, 102(16), p.165152_1 - 165152_8, 2020/10

 Times Cited Count:0

Journal Articles

Neutron diffraction monitoring of ductile cast iron under cyclic tension-compression

Harjo, S.; Kubota, Satoru*; Gong, W.*; Kawasaki, Takuro; Gao, S.*

Acta Materialia, 196, p.584 - 594, 2020/09

 Times Cited Count:0 Percentile:100(Materials Science, Multidisciplinary)

Journal Articles

Practical effects of pressure-transmitting media on neutron diffraction experiments using Paris-Edinburgh presses

Hattori, Takanori; Sano, Asami; Machida, Shinichi*; Ouchi, Keiichi*; Kira, Hiroshi*; Abe, Jun*; Funakoshi, Kenichi*

High Pressure Research, 40(3), p.325 - 338, 2020/09

 Times Cited Count:0 Percentile:100(Physics, Multidisciplinary)

To understand the practical effects of pressure-transmitting media (PTM) on neutron diffraction using Paris-Edinburgh presses, diffraction patterns of MgO were collected to approximately 20 GPa using PTMs of Pb, AgCl, 4:1 methano-ethanol (ME) mixture with and without heating, N$$_2$$, and Ar. Hydrostaticity in the sample chamber estimated from the MgO 220 peak width improves in the order of Pb, AgCl, Ar, ME mixture, N$$_2$$, and the heated ME mixture. Unlike previous results using a diamond anvil cell, the unheated ME mixture is superior to Ar even after freezing, probably due to the cup on the anvil face. Considering these results and the sizable coherent scattering of Ne, which would show good hydrostaticity, we conclude that the ME mixture (preferably the heated one) is the best PTM in neutron experiments up to 20 GPa, while Ar can be substituted when a sample is reactive to alcohols.

Journal Articles

Slow compression of crystalline ice at low temperature

Bauer, R.*; Tse, J. S.*; Komatsu, Kazuki*; Machida, Shinichi*; Hattori, Takanori

Nature, 585(7825), p.E9 - E10, 2020/09

 Times Cited Count:0 Percentile:100(Multidisciplinary Sciences)

Pressure-induced structural transformations in deuterated crystalline ice-Ih were studied in-situ at 100 K using neutron diffraction. Very long relaxation time was allowed between small pressure increments to promote transformations to the thermodynamic stable high pressure crystalline phases. The results contradict a recent report in which measurements under similar temperature and pressure environment show successive crystal-to-crystal transformations (Tulk, et.al., Nature 2019). Instead, ice Ih was found to transform partially to an amorphous form (high density amorphous, HDA) at 1.0 GPa and then ice VII started to emerge at 1.5 GPa, a pressure substantially lower than all earlier studies. During this pressure interval, crystalline ice Ih or ice VII co-exist with HDA. The ice VII formed is stable upon pressure release down to 0.1 GPa. The very low compression rate has a profound effect on the crystallinity in the amorphous regime. Gathering all the existing experimental evidences allows an unambiguous description of the phenomenon of pressure induced amorphization. The onset of the phase transition is triggered by a shear instability of the ice lattice. The co-existence ice VII with HDA, instead of the equilibrium thermodynamic stable and proton-ordered ice-VIII under the same pressure-temperature condition reveals at low temperature there is insufficient thermal energy to overcome the substantial geometrical rearrangement from a single proton disordered H-bond network to an interpenetrating proton ordered H-bond crystalline network. Thus, leaving the proton disordered H-network intact. The analysis shows unequivocally that the structure obtained from the compression of ice is controlled by kinetics and dependent on the temperature.

Journal Articles

Fabrication of a novel magnetic topological heterostructure and temperature evolution of its massive Dirac cone

Hirahara, Toru*; Otrokov, M. M.*; Sasaki, Taisuke*; Sumida, Kazuki*; Tomohiro, Yuta*; Kusaka, Shotaro*; Okuyama, Yuma*; Ichinokura, Satoru*; Kobayashi, Masaki*; Takeda, Yukiharu; et al.

Nature Communications (Internet), 11, p.4821_1 - 4821_8, 2020/09

 Times Cited Count:1 Percentile:100(Multidisciplinary Sciences)

Journal Articles

Applying image recognition technology by convolutional neural networks to mountain plot images

Nomura, Masahiro; Tamura, Fumihiko; Shimada, Taihei; Yamamoto, Masanobu; Furusawa, Masashi*; Sugiyama, Yasuyuki*; Hara, Keigo*; Hasegawa, Katsushi*; Omori, Chihiro*; Yoshii, Masahito*

Proceedings of 17th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.64 - 67, 2020/09

Image recognition using a convolutional neural network (CNN) has been used in a wide range of fields and has produced excellent results. If this image recognition technology is used effectively, it should be possible to obtain information from an image equal to or more than the information that a person can obtain from an image. At J-PARC, researchers with specialized knowledge obtain beam information needed to adjust the equipment from an image called mountain plot. In this study, we applied the image recognition technology by using CNN to this mountain plot image, and tried to obtain the information about the beam necessary for adjustment. As a result, we were able to obtain more information than is currently available by using the image recognition technology. In the future, we plan to adjust the equipment based on the information actually obtained from the image recognition technology and confirm its effectiveness

Journal Articles

Towards widespread use of MTCA in accelerators

Tamura, Fumihiko; Yoshii, Masahito*; Kamikubota, Norihiko*; Takahashi, Hiroki

Proceedings of 17th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.68 - 72, 2020/09

MTCA (MicroTCA) is expected to be the next generation platform for advanced control in accelerators. MTCA has many advantages over the widely used VMEs, such as high speed, large data transfer capacity, and high maintainability with hot-swappable modules. After the application to the LLRF control system at KEK, MTCA has been used in many accelerators around the world, while it takes a long time for MTCA to spread to the accelerators in Japan. Recently, the number of large-scale adoptions such as the LLRF control system, for the J-PARC RCS has been increasing. In this article, we introduce a case study of MTCA adoption and discuss why MTCA has not been widely used in Japan. Also, the efforts for the future promotion of MTCA in Japan are reported.

Journal Articles

Development of ignitron alternative semiconductor switch for J-PARC accelerator

Ono, Ayato; Takayanagi, Tomohiro; Ueno, Tomoaki*; Horino, Koki*; Yamamoto, Kazami; Kinsho, Michikazu

Proceedings of 17th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.590 - 593, 2020/09

At J-PARC, an ignitron is used for the clover device of the klystron power supply for high-frequency acceleration of a linear accelerator. Ignitron uses mercury, which is of limited use worldwide, and is expected to be discontinued in the future. Therefore, a semiconductor switch for ignitron substitution using a MOS gate thyristor is designed. In order to be used as a crowbar device, a switch capable of resisting an operating output of 120 kV, 40 kA, 50 us is required. We have realized an oval type substrate module that achieves an operating output of 3 kV, 40 kA, 50 us per substrate. It was possible to confirm the operating performance on a 1/10 scale (12 kV, 40 kA) against the voltage of the existing equipment (120 kV, 40 kA) by connecting four oval board modules in series. The output test result will be reported.

Journal Articles

Magnetic skyrmion lattice in 4f electron magnet EuPtSi

Kaneko, Koji; Kakihana, Masashi*; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*

Hamon, 30(3), p.160 - 165, 2020/08

no abstracts in English

Journal Articles

Local structure investigations of accumulated damage in irradiated MgAl$$_{2}$$O$$_{4}$$

Yoshioka, Satoru*; Tsuruta, Konosuke*; Yamamoto, Tomokazu*; Yasuda, Kazuhiro*; Matsumura, Sho*; Sugiyama, Takeharu*; Oba, Yojiro; Ishikawa, Norito; Kobayashi, Eiichi*; Okudaira, Koji*

Journal of the American Ceramic Society, 103(8), p.4654 - 4663, 2020/08

 Times Cited Count:0 Percentile:100(Materials Science, Ceramics)

X-ray absorption near edge structure (XANES) and small-angle X-ray scattering (SAXS) reveal the damaged structures in MgAl$$_{2}$$O$$_{4}$$ spinel induced by swift heavy ions. SAXS indicates the formation of ion tracks with cylindrical shape with a diameter of 5 nm. XANES indicates the cationic disordering between tetrahedral and octahedral sites by the irradiation. Quantitative analysis of XANES also reveals that cations preferably occupy the octahedral sites at high fluence.

Journal Articles

Strong lattice anharmonicity exhibited by the high-energy optical phonons in thermoelectric material

Wu, P.*; Fan, F.-R.*; Hagihara, Masato*; Kofu, Maiko; Peng, K.*; Ishikawa, Yoshihisa*; Lee, S.*; Honda, Takashi*; Yonemura, Masao*; Ikeda, Kazutaka*; et al.

New Journal of Physics (Internet), 22(8), p.083083_1 - 083083_9, 2020/08

 Times Cited Count:0 Percentile:100(Physics, Multidisciplinary)

Thermoelectric material SnSe has aroused world-wide interests in the past years, and its inherent strong lattice anharmonicity is regarded as a crucial factor for its outstanding thermoelectric performance. However, the understanding of lattice anharmonicity in SnSe system remains inadequate, especially regarding how phonon dynamics are affected by this behavior. In this work, we present a comprehensive study of lattice dynamics on Na$$_{0.003}$$Sn$$_{0.997}$$Se$$_{0.9}$$S$$_{0.1}$$ by means of neutron total scattering, inelastic neutron scattering, Raman spectroscopy as well as frozen-phonon calculations. Lattice anharmonicity is evidenced by pair distribution function, inelastic neutron scattering and Raman measurements. By separating the effects of thermal expansion and multi-phonon scattering, we found that the latter is very significant in high-energy optical phonon modes. The strong temperature-dependence of these phonon modes indicate the anharmonicity in this system. Moreover, our data reveals that the linewidths of high-energy optical phonons become broadened with mild doping of sulfur. Our studies suggest that the thermoelectric performance of SnSe could be further enhanced by reducing the contributions of high-energy optical phonon modes to the lattice thermal conductivity via phonon engineering.

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