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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：4 Percentile：61.64(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
. 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.
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.
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 
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.
CoSb
O
Ito, Saya*; Kurita, Nubuyuki*; Tanaka, Hidekazu*; Kawamura, Seiko; Nakajima, Kenji; Ito, Shinichi*; Kuwahara, Keitaro*; Kakurai, Kazuhisa*
Nature Communications (Internet), 8, p.235_1 - 235_6, 2017/08
Times Cited Count：38 Percentile：6.12(Multidisciplinary Sciences)Ohae, Chiaki*; Harries, J.; Iwayama, Hiroshi*; Kawaguchi, Kentaro*; Kuma, Susumu*; Miyamoto, Yuki*; Nagasono, Mitsuru*; Nakajima, Kyo*; Nakano, Itsuo*; Shigemasa, Eiji*; et al.
Journal of the Physical Society of Japan, 85(3), p.034301_1 - 034301_10, 2016/03
Times Cited Count：7 Percentile：41.41(Physics, Multidisciplinary)
C level structure by 
-ray spectroscopyHosomi, Kenji; Ma, Y.*; Ajimura, Shuhei*; Aoki, Kanae*; Dairaku, Seishi*; Fu, Y.*; Fujioka, Hiroyuki*; Futatsukawa, Kenta*; Imoto, Wataru*; Kakiguchi, Yutaka*; et al.
Progress of Theoretical and Experimental Physics (Internet), 2015(8), p.081D01_1 - 081D01_8, 2015/08
Times Cited Count：12 Percentile：29.87(Physics, Multidisciplinary)Level structure of the C hypernucleus was precisely determined by means of -ray spectroscopy. We identified four -ray transitions via the 
C
reaction using a germanium detector array, Hyperball2. The spacing of the ground-state doublet 
was measured to be 
(stat)
(syst)keV from the direct 
transition. Excitation energies of the 
and 
states were measured to be 
, keV and 
, keV, respectively. The obtained level energies provide definitive references for the reaction spectroscopy of 
hypernuclei.
Enoeda, Mikio; Tanigawa, Hisashi; Hirose, Takanori; Nakajima, Motoki; Sato, Satoshi; Ochiai, Kentaro; Konno, Chikara; Kawamura, Yoshinori; Hayashi, Takumi; Yamanishi, Toshihiko; et al.
Fusion Engineering and Design, 89(7-8), p.1131 - 1136, 2014/10
Times Cited Count：17 Percentile：13.4(Nuclear Science & Technology)The development of a Water Cooled Ceramic Breeder (WCCB) Test Blanket Module (TBM) is being performed as one of the most important steps toward DEMO blanket in Japan. Regarding the fabrication technology development using F82H, the fabrication of a real scale mockup of the back wall of TBM was completed. Also the assembling of the complete box structure of the TBM mockup and planning of the pressurization testing was studied. The development of advanced breeder and multiplier pebbles for higher chemical stability was performed for future DEMO blanket application. From the view point of TBM test result evaluation and DEMO blanket performance design, the development of the blanket tritium simulation technology, investigation of the TBM neutronics measurement technology and the evaluation of tritium production and recovery test using D-T neutron in the Fusion Neutronics Source (FNS) facility has been performed.
Kikuchi, Tatsuya; Nakajima, Kenji; Kawamura, Seiko; Inamura, Yasuhiro; Yamamuro, Osamu*; Kofu, Maiko*; Kawakita, Yukinobu; Suzuya, Kentaro; Nakamura, Mitsutaka; Arai, Masatoshi
Physical Review E, 87(6), p.062314_1 - 062314_8, 2013/06
Times Cited Count：11 Percentile：35.97(Physics, Fluids & Plasmas)A quasi-elastic neutron scattering (QENS) experiment is a particular technique that endeavors to define a relationship between time and space for the diffusion dynamics of atoms and molecules. However, in most cases, analyses of QENS data are model dependent. We have developed a new method for processing QENS data without a specific model, wherein all modes can be described as combinations of the relaxations based on the exponential law. By this method, we can obtain a new distribution function, 
, which we call the mode distribution function (MDF), to represent the number of relaxation modes and distributions of the relaxation times in the modes. The deduction of MDF is based on the maximum entropy method. We report the first application to experimental data of liquid water. In addition to the two known modes, the existence of a new relaxation mode of water molecules with an intermediate time scale has been discovered.
-FeSi nanocrystalsMaeda, Yoshihito; Nishimura, Kentaro*; Nakajima, Takahito*; Matsukura, Bui*; Narumi, Kazumasa; Sakai, Seiji
Physica Status Solidi (C), 9(10-11), p.1884 - 1887, 2012/10
Times Cited Count：4 Percentile：7.89We report enhancement of intrinsic photoluminescence (PL) from -FeSi nanocrystals by doping carbon. In the appropriate dose of C
ion implantation into the average nanocrystal size of 14 nm, the PL intensity was enhanced by 260% and increase of the exciton binding energy of 1.8 meV in comparison with that of the non-doped nanocrystal. Furthermore, we found that there was a clear correlation between the PL enhancement and increase of the exciton binding energy. This important result suggests that carbon atoms doped in the silicide lattice may play as an isoelectronic trap and probably form bound excitons with stable states as predicted theoretically. We found a new mechanism of the PL enhancement for -FeSi nanocrystals.
-FeSi nanocrystals embedded in SiMaeda, Yoshihito; Nishimura, Kentaro*; Nakajima, Takahito*; Matsukura, Bui*; Narumi, Kazumasa; Sakai, Seiji
Physica Status Solidi (C), 9(10-11), p.1888 - 1891, 2012/10
Times Cited Count：3 Percentile：11.77We have systematically investigated photoluminescence (PL) properties of -phase nanocrystals which are formed by a phase transition from metastable -FeSi with a Fluorite structure to -FeSi, and succeeded in enhancement of the PL intensity in the optimum conditions of double annealing process. For the PL enhancement, the time of postannealing at 800
C is dominated by the time of the preannealing at 400 or 500C which is related to amount of the -phase. After discussing some possible factors, we speculate that the PL enhancement observed in this study may be attributed mainly to improvement of the interface condition between the nanocrystal and Si, because the crystallographic epitaxial relationship among the phases, Si(111)//(111)//(202)/(220) can be maintained during precipitation of the nanocrystal on Si(111).
Ga
O (x =0, 0.018)Nakajima, Taro*; Mitsuda, Setsuo*; Takahashi, Keiichiro*; Yoshitomi, Keisuke*; Masuda, Kazuya*; Kaneko, Chikafumi*; Homma, Yuki*; Kobayashi, Satoru*; Kitazawa, Hideaki*; Kosaka, Masashi*; et al.
Journal of the Physical Society of Japan, 81(9), p.094710_1 - 094710_8, 2012/09
GaO (
= 0, 0.018)Nakajima, Taro*; Mitsuda, Setsuo*; Takahashi, Keiichiro*; Yoshitomi, Keisuke*; Masuda, Kazuya*; Kaneko, Chikafumi*; Homma, Yuki*; Kobayashi, Satoru*; Kitazawa, Hideaki*; Kosaka, Masashi*; et al.
Journal of the Physical Society of Japan, 81(9), p.094710_1 - 094710_8, 2012/09
Times Cited Count：12 Percentile：36.34(Physics, Multidisciplinary)
as seen via inelastic neutron scatteringNakajima, Taro*; Suno, Azusa*; Mitsuda, Setsuo*; Terada, Noriki*; Kimura, Shojiro*; Kaneko, Koji; Yamauchi, Hiroki
Physical Review B, 84(18), p.184401_1 - 184401_7, 2011/11
Times Cited Count：33 Percentile：19.05(Materials Science, Multidisciplinary)Sn cable-in-conduit conductorsHemmi, Tsutomu; Harjo, S.; Ito, Takayoshi; Matsui, Kunihiro; Nunoya, Yoshihiko; Koizumi, Norikiyo; Takahashi, Yoshikazu; Nakajima, Hideo; Aizawa, Kazuya; Suzuki, Hiroshi; et al.
IEEE Transactions on Applied Superconductivity, 21(3), p.2028 - 2031, 2011/06
Times Cited Count：9 Percentile：48.93(Engineering, Electrical & Electronic)Residual strain in conductors is caused by the difference in the coefficient of expansion between NbSn strands and the jacket over a temperature range of 5 - 923 K. The superconducting properties of strands vary significantly, depending on the strain. It is important to clarify the residual strain as part of the evaluation of superconducting performance. However, the residual strain of strands in the conductor has not been measured so far because of their complicated configuration and their location in a jacket. The engineering materials diffractometer "Takumi" in J-PARC can measure residual strain with a relative accuracy of around 0.02%, using neutron diffraction. In this study, the Takumi was applied to the measurement of residual strain in strands for the ITER TF conductor. Results indicate that the residual strain of strands in the conductor can be determined, thereby clarifying the mechanism of residual strain and its relationship to superconducting performance.
Nakajima, Kenji; Kawamura, Seiko; Kikuchi, Tatsuya; Nakamura, Mitsutaka; Kajimoto, Ryoichi; Inamura, Yasuhiro; Takahashi, Nobuaki; Aizawa, Kazuya; Suzuya, Kentaro; Shibata, Kaoru; et al.
Journal of the Physical Society of Japan, 80(Suppl.B), p.SB028_1 - SB028_6, 2011/05
Times Cited Count：84 Percentile：5.87(Physics, Multidisciplinary)AMATERAS is a cold-neutron disk-chopper spectrometer in MLF, J-PARC. The construction of main part of the spectrometer has been completed in spring of 2009. Soon after that, we have started the commissioning work on AMATERAS. The performance of AMATERAS has been examined by test experiments in the course of commissioning. In parallel to these works, we have started the user program on AMATERAS from December 2009 and we are getting scientific results from our spectrometer. In this presentation, we will report the current status of AMATERAS including the results of performance tests and some of examples of scientific outputs.
Kajimoto, Ryoichi; Nakamura, Mitsutaka; Inamura, Yasuhiro; Mizuno, Fumio; Nakajima, Kenji; Kawamura, Seiko; Yokoo, Tetsuya*; Nakatani, Takeshi; Maruyama, Ryuji; Soyama, Kazuhiko; et al.
Journal of the Physical Society of Japan, 80(Suppl.B), p.SB025_1 - SB025_6, 2011/01
Times Cited Count：66 Percentile：8.02(Physics, Multidisciplinary)Sakanaka, Shogo*; Akemoto, Mitsuo*; Aoto, Tomohiro*; Arakawa, Dai*; Asaoka, Seiji*; Enomoto, Atsushi*; Fukuda, Shigeki*; Furukawa, Kazuro*; Furuya, Takaaki*; Haga, Kaiichi*; et al.
Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.2338 - 2340, 2010/05
Future synchrotron light source using a 5-GeV energy recovery linac (ERL) is under proposal by our Japanese collaboration team, and we are conducting R&D efforts for that. We are developing high-brightness DC photocathode guns, two types of cryomodules for both injector and main superconducting (SC) linacs, and 1.3 GHz high CW-power RF sources. We are also constructing the Compact ERL (cERL) for demonstrating the recirculation of low-emittance, high-current beams using above-mentioned critical technologies.
Ga
OTerada, Noriki*; Nakajima, Taro*; Mitsuda, Setsuo*; Matsuda, Masaaki; Kakurai, Kazuhisa; Tanaka, Yoshihito*; Kitazawa, Hideaki*
Journal of Physics; Conference Series, 211(1), p.012005_1 - 012005_6, 2010/01
Times Cited Count：2 Percentile：29.85Al
O
Nakajima, Taro*; Mitsuda, Setsuo*; Inami, Toshiya; Terada, Noriki*; Osumi, Hiroyuki*; Prokes, K.*; Podlesnyak, A.*
Physical Review B, 78(2), p.024106_1 - 024106_10, 2008/07
Times Cited Count：35 Percentile：19.99(Materials Science, Multidisciplinary)Terada, Atsuhiko; Hino, Ryutaro; Hirayama, Toshio; Nakajima, Norihiro; Sugiyama, Hitoshi*
Proceedings of 15th International Conference on Nuclear Engineering (ICONE-15) (CD-ROM), 6 Pages, 2007/04
The Japan Atomic Energy Agency has been conducting study on thermochemical IS process for water splitting hydrogen production. Based on the test results and know-how obtained through the bench-scale test, a pilot test plant, which has a hydrogen production performance of 30 Nm/h, is being designed conceptually as the next step of the IS process development. In design of the IS pilot plant, it is important to make chemical reactors compact with high performance from the viewpoint of plant cost reduction. A new hydraulic analytical code has been developed for optimizing mixing performance of multi-phase flow involving chemical reactions especially in the Bunsen reactor. Preliminary analytical results obtained with above mentioned code, especially flow patterns induced by swirling flow agreed well with that measured by water experiments, which showed vortex breakdown pattern in a simplified Bunsen reactor.
