A Metallic -wave magnet with commensurate spin helix

Yamada, Rinsuke*; Birch, M. T.*; Baral, P. R.*; Okumura, Shun*; Nakano, Ryota*; Gao, S.*; Ezawa, Motohiko*; Nomoto, Takuya*; Masell, J.*; Ishihara, Yuki*; et al.

Nature, 646(8086), p.837 - 842, 2025/10

https://doi.org/10.1038/s41586-025-09633-4

Anisotropic creep property related to non-spherical shape of mechanically alloyed powder of oxide dispersion strengthened F82H

Sakasegawa, Hideo; Nakajima, Motoki*; Kato, Taichiro*; Nozawa, Takashi*; Ando, Masami*

Materials Today Communications (Internet), 40, p.109659_1 - 109659_8, 2024/08

https://doi.org/10.1016/j.mtcomm.2024.109659

Nanometric oxide particles play an important role in improving the creep property of Oxide Dispersion Strengthened (ODS) steels. In our previous research, we examined a microstructural feature known as prior particle boundary (PPB). PPB refers to the surface of mechanically alloyed (MA) powders before consolidation. We revealed that the ODS steel with fine PPBs produced from smaller MA powders, exhibited shorter creep rupture times, compared to that with coarse PPBs produced from larger MA powders. The size of MA powders had an impact on the creep property. In this study, we examined the shape of MA powders, which were non-spherical shapes. Such shapes have the potential to induce anisotropic creep behavior. We conducted small punch creep tests on specimens with two different orientations to study the possible anisotropy. The results revealed that the creep rupture times varied depending on the orientation of specimen, thus indicating anisotropic creep property.

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

https://doi.org/10.1088/1367-2630/aba98f

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 NaSnSeS 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.

Experimental study on local interfacial parameters in upward air-water bubbly flow in a vertical 66 rod bundle

Han, X.*; Shen, X.*; Yamamoto, Toshihiro*; Nakajima, Ken*; Sun, Haomin; Hibiki, Takashi*

International Journal of Heat and Mass Transfer, 144, p.118696_1 - 118696_19, 2019/12

https://doi.org/10.1016/j.ijheatmasstransfer.2019.118696

Enhancement of element production by incomplete fusion reaction with weakly bound deuteron

Wang, H.*; Otsu, Hideaki*; Chiga, Nobuyuki*; Kawase, Shoichiro*; Takeuchi, Satoshi*; Sumikama, Toshiyuki*; Koyama, Shumpei*; Sakurai, Hiroyoshi*; Watanabe, Yukinobu*; Nakayama, Shinsuke; et al.

Communications Physics (Internet), 2(1), p.78_1 - 78_6, 2019/07

https://doi.org/10.1038/s42005-019-0165-1

Searching for effective pathways for the production of proton- and neutron-rich isotopes through an optimal combination of reaction mechanism and energy is one of the main driving forces behind experimental and theoretical nuclear reaction studies as well as for practical applications in nuclear transmutation of radioactive waste. We report on a study on incomplete fusion induced by deuteron, which contains one proton and one neutron with a weak binding energy and is easily broken up. This reaction study was achieved by measuring directly the cross sections for both proton and deuteron for Pd at 50 MeV/u via inverse kinematics technique. The results provide direct experimental evidence for the onset of a cross-section enhancement at high energy, indicating the potential of incomplete fusion induced by loosely-bound nuclei for creating proton-rich isotopes and nuclear transmutation of radioactive waste.

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

https://doi.org/10.3390/qubs1030009

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.

Long distance fast data transfer experiments for the ITER Remote Experiment

Yamanaka, Kenjiro*; Nakanishi, Hideya*; Ozeki, Takahisa; Abe, Shunji*; Urushidani, Shigeo*; Yamamoto, Takashi*; Otsu, Hideo; Nakajima, Noriyoshi*

Fusion Engineering and Design, 112, p.1063 - 1067, 2016/11

https://doi.org/10.1016/j.fusengdes.2016.07.008

Development of effective and fast data transfer system for the huge amount data between Europe and Japan is a critical issues for ITER Remote Experimentation Center (REC). To implement the system, effective data transfer methods and wide bandwidth international network are required. We have evaluated two data transfer methods: Packet Pacing and MMCFTP. By using Packet Pacing and 2.4 Gbps line, we achieved 2.2 Gbps data transfer from NIFS to IFERC. By using MMCFTP and 10 Gbps line, we achieved 2.5 bps data transfer from NIFS to Dubline, Ireland. Furthermore, by using MMCFTP and 100 Gbps line, we successfully achieved the stable transmission of 1 PB of data at approximately 84 Gbps, which is an order of the world's fastest transmission speed. This paper also describes the upgrade plan of SINET, which will be upgraded to the network based on 100 Gigabit Ethernet technology in April 2016.

Novel electrothermodynamic power generation

Kim, Y.*; Kim, J.*; Yamanaka, Satoru*; Nakajima, Akira*; Ogawa, Takashi*; Serizawa, Takeshi*; Tanaka, Hirohisa*; Baba, Masaaki*; Fukuda, Tatsuo; Yoshii, Kenji; et al.

Advanced Energy Materials, 5(13), p.1401942_1 - 1401942_6, 2015/07

https://doi.org/10.1002/aenm.201401942

An innovative electro-thermodynamic cycle based on temporal temperature variations using pyroelectric effect has been presented. Practical energy is successfully generated in both synchrotron X-ray diffraction measurements under controlled conditions and real engine dynamometer experiments. The main generating origin is revealed as a combination of a crystal structure change and dipole change phenomenon corresponds to the temperature variation. In particular, the electric field induced 180 domain switching extremely improves generating power, and the true energy breakeven with temperature variation is firstly achieved.

Research program for the evaluation of fission product release and transport behavior focusing on FP chemistry

Sato, Isamu; Miwa, Shuhei; Tanaka, Kosuke; Nakajima, Kunihisa; Hirosawa, Takashi; Iwasaki, Maho; Onishi, Takashi; Osaka, Masahiko; Takai, Toshihide; Amaya, Masaki; et al.

Proceedings of 2014 Water Reactor Fuel Performance Meeting/ Top Fuel/ LWR Fuel Performance Meeting (WRFPM 2014) (USB Flash Drive), 6 Pages, 2014/09

A new research program on severe accidents is lunched for the evaluation of FP release and transport behavior in BWR system. The purpose of the program is to improve the FP release and transport model using experimental database about FP chemistry focusing on Cs and I chemistry. In this program, effects of B including in control rod materials, BC for the Cs and I chemistry are paid attention. The experimental database used for the improvement will consist of results to obtain with newly-prepared test device under atmosphere with broad-ranging oxygen and/or steam partial pressure simulated those in BWR. The state of preparation for these experimental studies and analyses is introduced. In addition, the preliminary test was moved into action to show B chemical effect on Cs and I transport under one of the processes, which is deposited Cs compounds and B vapor and aerosol interaction. In this experiment, a "B stripping effect" to deposited CsI was observed.

Performance test results for the Advanced Fuel Assembly Assay System (AFAS) on the active length verification of LWR MOX fuel assembly by neutron detectors

Nakajima, Shinji; Nagatani, Taketeru; Shiromo, Hideo; Asano, Takashi; Marlow, J. B.*; Swinhoe, M. T.*; Menlove, H. O.*; Rael, C. D.*; Kawasue, Akane*; Iso, Shoko*; et al.

Proceedings of INMM 55th Annual Meeting (Internet), 10 Pages, 2014/07

The Advanced Fuel Assembly Assay System (AFAS) is an unattended non-destructive assay (NDA) system by neutron measurement to verify the plutonium amount in an LWR plutonium and uranium mixed oxide (MOX) fuel assembly. The assembly will be fabricated in the MOX fuel fabrication plant under construction by the Japan Nuclear Fuel Limited. The AFAS has been developed by Los Alamos National Laboratory under the auspices of the Secretariat of Nuclear Regulation Authority in Japan. The AFAS is the first NDA system which will verify the active length of the assembly without inspector attendance. Japan Atomic Energy Agency (JAEA) has conducted the performance test for the AFAS under the contract with Nuclear Material Control Center to demonstrate this active length verification technology by using MOX fuel assemblies owned by JAEA. As the results, it was confirmed that measurement error of the active length for the MOX fuel assembly was less than 0.1% and it was satisfied with requirement by IAEA. This paper provides the performance test results for the active length verification of the AFAS.