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Journal Articles

Rabi-oscillation spectroscopy of the hyperfine structure of muonium atoms

Nishimura, Shoichiro*; Torii, Hiroyuki*; Fukao, Yoshinori*; Ito, Takashi; Iwasaki, Masahiko*; Kanda, Sotaro*; Kawagoe, Kiyotomo*; Kawall, D.*; Kawamura, Naritoshi*; Kurosawa, Noriyuki*; et al.

Physical Review A, 104(2), p.L020801_1 - L020801_6, 2021/08

 Times Cited Count:12 Percentile:84.06(Optics)

Journal Articles

$$q$$=0 long-range magnetic order in centennialite CaCu$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O; A Spin-$$frac{1}{2}$$ perfect kagome antiferromagnet with $$J_{1}$$-$$J_{2}$$-$$J_{d}$$

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:19 Percentile:81(Materials Science, Multidisciplinary)

Crystal and magnetic structures of the mineral centennialite CaCu$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O 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$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O, Cu$$^{2+}$$ ions form a geometrically perfect kagome network with antiferromagnetic $$J_{1}$$. No intersite disorder between Cu$$^{2+}$$ and Ca$$^{2+}$$ ions is detected. CaCu$$_{3}$$(OD)$$_{6}$$Cl$$_{2}$$ $$cdot$$ 0.6D$$_{2}$$O enters a magnetic long-range ordered state below $$T_{rm N}$$ = 7.2 K, and the $$q$$=0 magnetic structure with negative vector spin chirality is obtained. The ordered moment at 0.3 K is suppressed to 0.58(2)$$mu$$B. Our DFT calculations indicate the presence of antiferromagnetic $$J_{2}$$ and ferromagnetic $$J_{d}$$ superexchange couplings of a strength which places the system at the crossroads of three magnetic orders (at the classical level) and a spin-$$frac{1}{2}$$ PFFRG analysis shows a dominance of $$q$$=0 type magnetic correlations, consistent with and indicating proximity to the observed $$q$$=0 spin structure. The results suggest that this material is located close to a quantum critical point and is a good realization of a $$J_{1}$$-$$J_{2}$$-$$J_{d}$$ kagome antiferromagnet.

Journal Articles

Highlight of recent sample environment at J-PARC MLF

Kawamura, Seiko; Hattori, Takanori; Harjo, S.; Ikeda, Kazutaka*; Miyata, Noboru*; Miyazaki, Tsukasa*; Aoki, Hiroyuki; Watanabe, Masao; Sakaguchi, Yoshifumi*; Oku, Takayuki

Neutron News, 30(1), p.11 - 13, 2019/05

In Japanese neutron scattering facilities, some SE equipment that are frequently used at an instrument, such as the closed-cycle refrigerator (CCR), have been prepared for the instrument as standard SE. They are operated for user experiments by the instrument group. The advantage of this practice is that they can optimize the design of the SE for the instrument and can directly respond to users' requests. On the other hand, the SE team in the Materials and Life Science Experimental Facility (MLF) in J-PARC has managed commonly used SE to allow neutron experiments with more advanced SE. In this report, recent SE in the MLF is introduced. Highlighted are the SE in BL11, BL19, BL21 and BL17 and other SE recently progressed by the SE team.

Journal Articles

Fuel debris' air cooling analysis using a lattice Boltzmann method

Onodera, Naoyuki; Idomura, Yasuhiro; Kawamura, Takuma; Uesawa, Shinichiro; Yamashita, Susumu; Yoshida, Hiroyuki

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 6 Pages, 2019/05

A dry method is one of practical methods for decommissioning the TEPCO's Fukushima Daiichi Nuclear Power Station. Japan Atomic Energy Agency (JAEA) has been evaluating the air cooling performance by using the JUPITER code. However, the JUPITER code requires a large computational cost to capture debris' structures. To accelerate such CFD analyses, we use the CityLBM code, which is based on the lattice Boltzmann method (LBM) and is highly optimized for GPUs. The CityLBM code is validated against free convective heat transfer experiments at JAEA, and the similar accuracy as the JUPITER code is confirmed regarding the prediction capability of heat transfer and the resulting temperature distributions. It is also shown that the elapse time of a CityLBM simulation on GPUs is reduced to 1/6 compared with that of the corresponding JUPITER simulation on CPUs with the same number of GPUs and CPUs. The results show that the LBM is promising for accelerating thermal convective simulations.

Journal Articles

Development of compact high field pulsed magnet system for new sample environment equipment at MLF in J-PARC

Watanabe, Masao; Nojiri, Hiroyuki*; Ito, Shinichi*; Kawamura, Seiko; Kihara, Takumi*; Masuda, Takatsugu*; Sahara, Takuro*; Soda, Minoru*; Takahashi, Ryuta

JPS Conference Proceedings (Internet), 25, p.011024_1 - 011024_5, 2019/03

Recently, neutron scattering experiments have been rapidly progressed under high magnetic field. In the J-PARC, proto-type compact pulse magnet system with the power supply, the coil and the sample stick has been developed. Basic specifications of the power supply are as follows; maximum charged voltage with capacitor is 2 kV, maximum current is 8 kA, repetition rate is a pulse per several minutes and pulse duration is several msec. Maximum magnetic field in the coil is more than 30 Tesla. The sample stick is designed for Orange-Cryostat. In this presentation, We report the details of the pulsed magnet system and the performance of it on neutron scattering experiments at MLF beam line (HRC).

Journal Articles

New precise measurements of muonium hyperfine structure at J-PARC MUSE

Strasser, P.*; Abe, Mitsushi*; Aoki, Masaharu*; Choi, S.*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; et al.

EPJ Web of Conferences, 198, p.00003_1 - 00003_8, 2019/01

 Times Cited Count:13 Percentile:99.28

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

New precise measurement of muonium hyperfine structure interval at J-PARC

Ueno, Yasuhiro*; Aoki, Masaharu*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; Ito, Takashi; Iwasaki, Masahiko*; et al.

Hyperfine Interactions, 238(1), p.14_1 - 14_6, 2017/11

 Times Cited Count:3 Percentile:86.59

Journal Articles

New muonium HFS measurements at J-PARC/MUSE

Strasser, P.*; Aoki, Masaharu*; Fukao, Yoshinori*; Higashi, Yoshitaka*; Higuchi, Takashi*; Iinuma, Hiromi*; Ikedo, Yutaka*; Ishida, Katsuhiko*; Ito, Takashi; Iwasaki, Masahiko*; et al.

Hyperfine Interactions, 237(1), p.124_1 - 124_9, 2016/12

 Times Cited Count:7 Percentile:91.29

Journal Articles

Physics-basis simulation of bubble pinch-off

Ito, Kei; Koizumi, Yasuo; Ohshima, Hiroyuki; Kawamura, Takumi*

Mechanical Engineering Journal (Internet), 3(3), p.15-00671_1 - 15-00671_9, 2016/06

Journal Articles

Direct measurement of nanoscale lithium diffusion in solid battery materials using radioactive tracer of $$^{8}$$Li

Ishiyama, Hironobu*; Jeong, S.-C.*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Jung, H. S.*; Miyatake, Hiroari*; Oyaizu, Mitsuhiro*; Osa, Akihiko; Otokawa, Yoshinori; et al.

Nuclear Instruments and Methods in Physics Research B, 376, p.379 - 381, 2016/06

 Times Cited Count:7 Percentile:60.71(Instruments & Instrumentation)

Journal Articles

Physics-basis simulation of bubble pinch-off

Ito, Kei; Koizumi, Yasuo*; Ohshima, Hiroyuki; Kawamura, Takumi*

Proceedings of 23rd International Conference on Nuclear Engineering (ICONE-23) (DVD-ROM), 6 Pages, 2015/05

The authors are developing a high-precision CFD code with an interface tracking method to simulate the gas entrainment (GE) phenomena in sodium-cooled fast reactors (SFRs), which might be caused by a highly-intensified free surface vortex. The GE in SFRs is characterized by an elongated interfacial dent along the vortex core and the bubble pinch-off at the tip of the dent. To simulate this complicated phenomenon, our simulation code has physics-basis algorithms which model accurately the interfacial dynamic behavior, the pressure jump condition at an interface and the surface tension. Several verification problems have been already solved and the accuracy of each individual algorithm is confirmed. In this paper, a basic experiment of the GE is simulated to validate the developed code. The simulation result of the entrained flow rate shows comparable value to the experimental data, that is, our simulation code is considered applicable to the evaluation of the GE in SFRs.

Journal Articles

Nanoscale diffusion tracing by radioactive $$^{8}$$Li tracer

Ishiyama, Hironobu*; Jeong, S.-C.*; Watanabe, Yutaka*; Hirayama, Yoshikazu*; Imai, Nobuaki*; Miyatake, Hiroari*; Oyaizu, Mitsuhiro*; Katayama, Ichiro*; Osa, Akihiko; Otokawa, Yoshinori; et al.

Japanese Journal of Applied Physics, 53(11), p.110303_1 - 110303_4, 2014/11

 Times Cited Count:4 Percentile:18.27(Physics, Applied)

Journal Articles

Study on surface tension modeling for mechanistic evaluation of vortex cavitation

Ito, Kei; Ezure, Toshiki; Ohshima, Hiroyuki; Kawamura, Takumi*; Nakamine, Yoshiaki*

Proceedings of 9th Korea-Japan Symposium on Nuclear Thermal Hydraulics and Safety (NTHAS-9) (CD-ROM), 6 Pages, 2014/11

The authors have been studied the vortex cavitation in sodium-cooled fast reactors. In this paper, the authors present a modified evaluation method for vortex cavitation, in which a surface tension is modeled mechanistically. Namely, the cavity radius is calculated in consideration of radial pressure distribution, saturated vapor pressure and the pressure jump condition at an interface. As the basic validation of the developed surface tension model, numerical analyses of a simple experiment under various velocity conditions are performed. The evaluation results give qualitatively appropriate tendency, that is, the cavity radius becomes larger with the higher liquid velocity and/or lower reference pressure which cause the larger pressure drop at the vortex. In addition, the authors evaluate the influence of the kinematic viscosity which plays an important role in the vortex cavitation occurrences in the experiments.

Journal Articles

Present status of J-PARC linac

Oguri, Hidetomo; Hasegawa, Kazuo; Ito, Takashi; Chishiro, Etsuji; Hirano, Koichiro; Morishita, Takatoshi; Shinozaki, Shinichi; Ao, Hiroyuki; Okoshi, Kiyonori; Kondo, Yasuhiro; et al.

Proceedings of 11th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.389 - 393, 2014/10

no abstracts in English

Journal Articles

A Volume-conservative PLIC algorithm on three-dimensional fully unstructured meshes

Ito, Kei; Kunugi, Tomoaki*; Ohshima, Hiroyuki; Kawamura, Takumi*

Computers & Fluids, 88, p.250 - 261, 2013/12

 Times Cited Count:23 Percentile:69.83(Computer Science, Interdisciplinary Applications)

The PLIC (Piecewise Linear Interface Calculation) algorithm is one of the volume-of-fluid algorithms. However, the PLIC algorithm needs complicated geometrical calculations for the reconstructions of the interfaces in interfacial cells, and therefore, the PLIC algorithm on unstructured meshes have not been studied enough. In this paper, the authors propose a new PLIC algorithm on unstructured meshes with arbitrary-shaped cells. In the proposed PLIC algorithm, several methods are developed or implemented. In addition, the volume fraction transport is improved by developing a volume-conservative algorithm in which gas and liquid volumes are conserved perfectly during the transport. As a result of the verification and validation tests, it is confirmed that the proposed PLIC algorithm enables the numerical simulations of interfacial dynamic behaviors with high accuracy even on unstructured meshes with highly-irregular cell arrangement.

Journal Articles

Study on simulation code for dilute bubbly flow

Ito, Kei; Takata, Takashi*; Ohno, Shuji; Kogawa, Hiroyuki; Kamide, Hideki; Imai, Yasutomo*; Kawamura, Takumi*

Nihon Kikai Gakkai Rombunshu, B, 79(808), p.2630 - 2634, 2013/12

In a sodium-cooled fast reactor, inert gas exists in the primary coolant system as bubbles or dissolved gas. Similarly, small bubbles exist also in the mercury target loop in J-PARC to suppress cavitation erosion. To simulate these inert gas behaviors in liquid metal flows, the Japan Atomic Energy Agency (JAEA) has developed a plant dynamics code VIBUL. In this study, new models, i.e. the bubble release and bubble carry under models, are introduced to simulate the bubble behaviors in the fast reactor and mercury target system. Then, the small bubble behavior in the mercury target system is simulated to check the validity of the new models.

JAEA Reports

Study on numerical simulation of bubble and dissolved gas behavior in liquid metal flow

Ito, Kei; Ohno, Shuji; Kamide, Hideki; Kogawa, Hiroyuki; Futakawa, Masatoshi; Kawamura, Takumi*; Imai, Yasutomo*

JAEA-Research 2013-008, 117 Pages, 2013/10

JAEA-Research-2013-008.pdf:6.55MB

The Japan Atomic Energy Agency has been developed a plant dynamics code VIBUL to simulate the concentration distributions of the dissolved gas and the bubbles in a fast reactor. In this study, the VIBUL code is improved to achieve accurate simulations, e.g. rigorous mole conservation of inert gas. Moreover, new modles are introduced to simulate the small bubble behaviors in the J-PARC mercury target system. To validate the improved models and the newly developed models, the inert gas behaviors in the large-scale sodium-cooled reactor and the small bubble behaviors are simulated. As a result, it is confirmed that the complicated bubble dynamics in each component, e.g. core, IHX or surge tank, can be simulated appropriately by the VIBUL code.

Journal Articles

RF control system for the RFQ test station at J-PARC linac

Fukui, Yuji*; Kawamura, Masato*; Kobayashi, Tetsuya*; Fang, Z.*; Futatsukawa, Kenta*; Sato, Fumiaki; Shinozaki, Shinichi; Suzuki, Hiroyuki; Chishiro, Etsuji; Hori, Toshihiko; et al.

Proceedings of 9th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.762 - 764, 2013/08

no abstracts in English

Journal Articles

Tilted-foil technique for producing a spin-polarized radioactive isotope beam

Hirayama, Yoshikazu*; Mihara, Mototsugu*; Watanabe, Yutaka*; Jeong, S. C.*; Miyatake, Hiroari*; Momota, Sadao*; Hashimoto, Takashi*; Imai, Nobuaki*; Matsuta, Kensaku*; Ishiyama, Hironobu*; et al.

European Physical Journal A, 48(5), p.54_1 - 54_10, 2012/05

 Times Cited Count:2 Percentile:16.84(Physics, Nuclear)

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