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Mattan, K.*; Ono, Toshio*; Kawamura, Seiko; Nakajima, Kenji; Nambu, Yusuke*; Sato, Taku*
Physical Review B, 105(13), p.134403_1 - 134403_8, 2022/04
Times Cited Count：3 Percentile：48.5(Materials Science, Multidisciplinary)Spin dynamics of the spin-1/2 kagome-lattice antiferromagnet Cs
Cu
SnF
was studied using high-resolution, time-of-flight inelastic neutron scattering. The flat mode, a characteristic of the frustrated kagome antiferromagnet, and the low-energy dispersive mode, which is dominated by magnons, can be well described by the linear spin-wave theory. However, the theory fails to describe three weakly dispersive modes between 9 and 14 meV. These modes could be attributed to two-spinon bound states, which decay into free spinons away from the zone center and at a high temperature, giving rise to continuum scattering.
Takeda, Masayasu
Bunseki, 2021(11), p.611 - 615, 2021/11
no abstracts in English
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：8 Percentile：58.58(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
Sn
Se
S
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.
=0 long-range magnetic order in centennialite CaCu(OD)
Cl 
0.6DO; A Spin-
perfect kagome antiferromagnet with 
-
-
Iida, Kazuki*; Yoshida, Hiroyuki*; Nakao, Akiko*; Jeschke, H. O.*; Iqbal, Y.*; Nakajima, Kenji; Kawamura, Seiko; Munakata, Koji*; Inamura, Yasuhiro; Murai, Naoki; et al.
Physical Review B, 101(22), p.220408_1 - 220408_6, 2020/06
Times Cited Count：22 Percentile：80.38(Materials Science, Multidisciplinary)Crystal and magnetic structures of the mineral centennialite CaCu(OD)Cl 0.6DO are investigated by means of synchrotron X-ray diffraction and neutron diffraction measurements complemented by density functional theory (DFT) and pseudofermion functional renormalization group (PFFRG) calculations. In CaCu(OD)Cl 0.6DO, Cu
ions form a geometrically perfect kagome network with antiferromagnetic . No intersite disorder between Cu and Ca ions is detected. CaCu(OD)Cl 0.6DO enters a magnetic long-range ordered state below 
= 7.2 K, and the =0 magnetic structure with negative vector spin chirality is obtained. The ordered moment at 0.3 K is suppressed to 0.58(2)
B. Our DFT calculations indicate the presence of antiferromagnetic and ferromagnetic superexchange couplings of a strength which places the system at the crossroads of three magnetic orders (at the classical level) and a spin- PFFRG analysis shows a dominance of =0 type magnetic correlations, consistent with and indicating proximity to the observed =0 spin structure. The results suggest that this material is located close to a quantum critical point and is a good realization of a -- kagome antiferromagnet.
Oi, Motoki
Shiki, 43, P. 3, 2019/06
At the J-PARC Materials and Life Science Facility (MLF), we developed an Au-In-Cd alloy as a low activation neutron absorber for reducing the activity of moderator assembly, and put it to practical use in the reflector and moderator. As a method to confirm the distribution of indium in the alloy, pulse neutron imaging method is adopted, and the individual element distribution is measured by focusing on the resonance peak of indium, and the uniformity of the alloy is confirmed.
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.
Aso, Tomokazu; Teshigawara, Makoto; Hasegawa, Shoichi; Aoyagi, Katsuhiro*; Muto, Hideki*; Nomura, Kazutaka*; Takada, Hiroshi; Ikeda, Yujiro
JAEA-Technology 2017-021, 75 Pages, 2017/08
JAEA-Technology-2017-021.pdf:33.03MB
Liquid hydrogen is employed as a cold neutron moderator material at the spallation neutron source of Materials and Life science experimental Facility of Japan Proton Accelerator Research Complex (J-PARC). From January 2015, it became observable that the differential pressure between heat exchangers and an 80 K adsorber (ADS) in a helium refrigerator system increased with operating time. In November 2015, the differential pressure rise became more significant, leading to degrade the refrigerating performance in cooling liquid hydrogen. In order to investigate the cause of the abnormal differential pressure rise between the heat exchangers and the ADS, we carried out visual inspection inside the heat exchangers and analyzed the impurities contained in the helium gas. Unfortunately, we could not identify the impurities causing the performance degradation, but observed a trace of oil in the inlet piping of the heat exchanger. Based on investigations of the abnormal events occurred in the refrigerators with similar refrigerating capacity at other facilities, we took measures that cleaning the heat exchangers with Freon and replacing the ADS with new one. As a result, the differential pressure rise phenomenon was removed to recover the performance. We have detected oil from the Freon used for cleaning the heat exchangers and at a felt supporting charcoal packed in the ADS. In particular, oil was accumulated in membranous form onto the felt at the entrance side in the ADS. The amount of oil contained in the helium gas was about 10 ppb or so, less than the design value, in the helium refrigerator. However, the oil accumulated onto the felt in the ADS through long operating period may cause abnormal differential pressure rise, leading to the performance degradation of the helium refrigerator. Further study is needed to specify the cause more clearly.
Oh, J.*; Le, M. D.*; Nahm, H.-H.*; Sim, H.*; Jeong, J.*; Perring, T. G.*; Woo, H.*; Nakajima, Kenji; Kawamura, Seiko; Yamani, Z.*; et al.
Nature Communications (Internet), 7, p.13146_1 - 13146_6, 2016/10
Times Cited Count：56 Percentile：86.85(Multidisciplinary Sciences)Magnons and phonons are fundamental quasiparticles in a solid and can be coupled together to form a hybrid quasi-particle. However, detailed experimental studies on the underlying Hamiltonian of this particle are rare for actual materials. Moreover, the anharmonicity of such magnetoelastic excitations remains largely unexplored, although it is essential for a proper understanding of their diverse thermodynamic behaviour and intrinsic zero-temperature decay. Here we show that in non-collinear antiferromagnets, a strong magnon phonon coupling can significantly enhance the anharmonicity, resulting in the creation of magnetoelastic excitations and their spontaneous decay. By measuring the spin waves over the full Brillouin zone and carrying out anharmonic spin wave calculations using a Hamiltonian with an explicit magnon phonon coupling, we have identified a hybrid magnetoelastic mode in (Y,Lu)MnO and quantified its decay rate and the exchange-striction coupling termrequired to produce it.
Matsuo, Tatsuhito; Arata, Toshiaki*; Oda, Toshiro*; Nakajima, Kenji; Kawamura, Seiko; Kikuchi, Tatsuya; Fujiwara, Satoru
Biochemistry and Biophysics Reports (Internet), 6, p.220 - 225, 2016/07
-based magnet in a nanoporous metal complexSoda, Minoru*; Homma, Yuki*; Takamizawa, Satoshi*; Kawamura, Seiko; Nakajima, Kenji; Masuda, Takatsugu*
Journal of the Physical Society of Japan, 85(3), p.034717_1 - 034717_9, 2016/03
Times Cited Count：1 Percentile：11.46(Physics, Multidisciplinary)Inelastic neutron scattering experiments are performed on the nanoporous metal complex Cu-
-1,4-cyclohexanedicarboxylic acid (Cu-CHD) adsorbing O molecules to identify the spin model of the O-based magnet realized in the host complex. It is found that the magnetic excitations of Cu-CHDs adsorbing low- and high-concentration O molecules are explained by different spin models, the former by spin dimers and the latter by spin trimers. By using the obtained parameters and by assuming that the levels of the group of the highest energy states are reduced because of the nonnegligible spin dependence of the molecular potential of oxygen, the magnetization curves are explained quantitatively.
Yamada, Norifumi*; Takeda, Masayasu; Yamazaki, Dai
Hamon, 24(4), p.288 - 295, 2014/11
no abstracts in English
Takeda, Masayasu; Yamazaki, Dai; Soyama, Kazuhiko; To, Kentaro; Yamagishi, Hideshi*; Katagiri, Masaki*; Sakasai, Kaoru; Mizusawa, Tazuko*; Miyata, Noboru*; Kasai, Satoshi*; et al.
no journal, ,
Oi, Motoki; Harada, Masahide; Kai, Tetsuya; Aizawa, Kazuya; Sato, Koichi; Masuyama, Koichi; Kasugai, Yoshimi
no journal, ,
In the J-PARC Materials and Life Science Experimental Facility (MLF), material science experiments using muon and neutron beam are performed. In the MLF, proton beam power was 300KW at May 2014 and it is planning to enhance to 1MW. For proton beam enhancement, we performed evaluation of the shielding performance of the neutron beam instruments. As a result, dose on the shield surface of 16 neutron instruments are sufficiently low for 1MW proton beam operation. However, 4 neutron instruments show high dose rate in particular neutron beam conditions. For these neutron instruments, we have checked the drawings and recalculate the shielding performance and considered a cause. Then based on the measurement results, some shield are added for these four neutron instruments and dose rate are reduced sufficiently to 1MW proton beam operation.
Aso, Tomokazu; Teshigawara, Makoto; Hasegawa, Shoichi; Muto, Hideki; Aoyagi, Katsuhiro; Nomura, Kazutaka; Takada, Hiroshi
no journal, ,
no abstracts in English
Shibata, Kaoru
no journal, ,
A time-of-flight (TOF) type near-backscattering spectrometer (n-BSS), DNA was built and started operation in 2012 at the Materials and Life Science Experimental Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC).
Aso, Tomokazu; Teshigawara, Makoto; Hasegawa, Shoichi; Muto, Hideki; Aoyagi, Katsuhiro; Nomura, Kazutaka; Takada, Hiroshi
no journal, ,
no abstracts in English
Harada, Masahide; Kawakami, Kazuhiro*; Aizawa, Kazuya; Soyama, Kazuhiko; Sato, Koichi; Masuyama, Koichi; Kasugai, Yoshimi
no journal, ,
no abstracts in English
Nakatani, Takeshi; Inamura, Yasuhiro; Moriyama, Kentaro*
no journal, ,
The instrument control software framework "IROHA2" have been introduced and used in several neutron instruments at MLF, J-PARC. IROHA2 consists of several severs, which are the device control, the instrument management, the sequence management and the integrate control. Users cooperate to use these servers to carry out their experiments with a web browser. By the development since last year, new features are implemented to IROHA2 as follows: (1) Real-time data processing interface on the device control server with a distributed messaging middleware, (2) Flexible web user interfaces for automatic measurements on the sequence management server, (3) Remote experimental status monitoring system on the integrate control server, which is access controlled by the MLF integrate authorization system. We will report the implementation status and future plans of IROHA2.
Oi, Motoki; Hosokawa, Hidemitsu*; Nishikawa, Masaaki*; Fukuda, Shimpei; Teshigawara, Makoto; Meigo, Shinichiro; Takada, Hiroshi
no journal, ,
At J-PARC, a neutron production target is installed in the helium vessel, and 3-GeV proton beams are delivered from a 3-GeV synchrotron to the target through a beamline with high vacuum environment. A proton beam window (PBW) is installed to isolate the helium vessel from the proton beamline. Since the PBW is degraded by radiation damage, it is scheduled to be replaced every 2 or 3 years under the 1-MW operation. In the summer outage in 2017, the PBW #2 was replaced to #3. A shielding cask was used for transferring the activated PBW, while hands-on works were done to remove the cooling water pipes at the top of the shielding plug of PBW. Since the cooling water contains 5
10
Bq/cc of tritium, it was drained from the pipes and the pipes were dried before removing PBW. The hands-on work was carried out in a green-house with a local exhaust device to prevent scattering of radioactive materials. In this presentation, we report the replacement work of the PBW including safety measures.
Haga, Katsuhiro; Wakui, Takashi; Wakai, Eiichi; Naoe, Takashi; Kogawa, Hiroyuki; Takada, Hiroshi
no journal, ,
The maximum beam power for user operation of the present neutron target vessel is limited to 700 kW due to the allowable thermal stress. However, to allow the rated 1-MW operation, the next neutron target vessel changed the target structure and the water channel arrangement to reduce the thermal stress for achieving 1MW beam power. In the new target vessel design, the mercury vessel and water shroud were separated in the front half part of the target vessel where the heat generation density is high, and the water channel arrangement was optimized to reduce the thermal stress caused by the difference of thermal expansion between those two vessels. The fabrication design was changed to reduce the total parts number to be the minimum, and the number of welding lines was drastically reduced by fabricating each part from the block of stainless steel with wire electrode discharge machining. The welding deformation and the residual stress were also reduced by applying electron beam welding to part of the welds. Furthermore, the radiation tests and ultra-sonic tests were applied in the fabrication processes to check the soundness of welds. As for the cavitation damage caused by the pressure wave, the damage depth of the specimen cut out from the used neutron target vessel which was operated at the beam power of 150 kW to 200 kW was measured, and damage data to improve the damage evaluation under the non-bubble condition was obtained.
