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Journal Articles

Chiral effective theory of diquarks and the $$U_A(1)$$ anomaly

Harada, Masayasu*; Liu, Y.-R.*; Oka, Makoto; Suzuki, Kei

Physical Review D, 101(5), p.054038_1 - 054038_11, 2020/03

 Times Cited Count:2 Percentile:12.6(Astronomy & Astrophysics)

Using a chiral effective theory of diquarks, we analyze the spectrum and structure of diquark and heavy baryons consisting of diquarks. $$U_A(1)$$ anomaly is considered in the chiral Lagrangian and its effects are studied.

Journal Articles

Study on B$$_{4}$$C decoupler with burn-up reduction aiming at 1-MW pulsed neutron source

Oi, Motoki; Teshigawara, Makoto; Harada, Masahide; Ikeda, Yujiro

Journal of Nuclear Science and Technology, 56(7), p.573 - 579, 2019/07

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

In pulsed neutron sources, a neutron absorber called decoupler is attached to the moderator to sharpen the neutron pulses for achieving good neutron energy resolutions. Cadmium and boron carbide (B$$_{4}$$C) are widely used as the decoupler materials. However, it is difficult to use B$$_{4}$$C in MW-class spallation neutron sources owing to high burn-up, which decreases cut-off energy and increase of helium gas swelling. To solve these issues, we introduce the concept of pre-decoupler to reduce neutron absorption in the B$$_{4}$$C decoupler, which is sandwiched by appropriate neutron absorption materials. Then, we study impacts of the pre-decouplers on B$$_{4}$$C decoupler in terms of burn-up by performing simplified model calculations. It is shown that neutron absorption in B$$_{4}$$C is reduced by 60% by using a Cd pre-decoupler without neutron intensity penalty. Moreover, helium gas swelling in B$$_{4}$$C is restrained to be one-third of the value when not using the pre-decoupler.

Journal Articles

Measurement of neutron scattering cross section of nano-diamond with particle diameter of approximately 5 nm in energy range of 0.2 meV to 100 meV

Teshigawara, Makoto; Tsuchikawa, Yusuke*; Ichikawa, Go*; Takata, Shinichi; Mishima, Kenji*; Harada, Masahide; Oi, Motoki; Kawamura, Yukihiko*; Kai, Tetsuya; Kawamura, Seiko; et al.

Nuclear Instruments and Methods in Physics Research A, 929, p.113 - 120, 2019/06

 Times Cited Count:2 Percentile:26.15(Instruments & Instrumentation)

A nano-diamond is an attractive neutron reflection material below cold neutron energy. The total neutron cross section of a nano-diamond was derived from a neutron transmission measurement over the neutron energy range of 0.2 meV to 100 meV because total neutron cross section data were not available. The total cross section of a nano-diamond with particle size of approximately 5 nm increased with a decrease in neutron energy to 0.2 meV. It was approximately two orders of magnitude larger than that of graphite at 0.2 meV. The contribution of inelastic scattering to the total cross section was to be shown negligible small at neutron energies of 1.2, 1.5, 1.9, 2.6, and 5.9 meV in the inelastic neutron scattering measurement. Moreover, small-angle neutron scattering measurements of the nano-diamond showed a large scattering cross section in the forward direction for low neutron energies.

Journal Articles

Observation of simulated fuel debris using synchrotron radiation

Yoneda, Yasuhiro; Harada, Makoto; Takano, Masahide

Transactions of the Materials Research Society of Japan, 44(2), p.61 - 64, 2019/04

We performed three-dimensional observation of simulated fuel debris using Synchrotron Computed Tomography (CT). CT was used to make the inside of fuel debris clear. The CT observation provides that a clear contrast in the zirconia rich part and concrete rich part. Zirconia heavier than concrete moved to the lower part when crystals precipitate and aggregates near the bottom surface. As a result, phase separation occurs. The phase separation is caused by the difference in the composition ratio of zirconia, and can also be observed difference in crystal growth mode by composition ratio.

Journal Articles

Gamma-ray spectrum from thermal neutron capture on gadolinium-157

Hagiwara, Kaito*; Yano, Takatomi*; Das, P. K.*; Lorenz, S.*; Ou, Iwa*; Sakuda, Makoto*; Kimura, Atsushi; Nakamura, Shoji; Iwamoto, Nobuyuki; Harada, Hideo; et al.

Progress of Theoretical and Experimental Physics (Internet), 2019(2), p.023D01_1 - 023D01_26, 2019/02

 Times Cited Count:3 Percentile:25.77(Physics, Multidisciplinary)

Journal Articles

Experimental validation of the brightness distribution on the surfaces of coupled and decoupled moderators composed of 99.8% parahydrogen at the J-PARC pulsed spallation neutron source

Harada, Masahide; Teshigawara, Makoto; Oi, Motoki; Klinkby, E.*; Zanini, L.*; Batkov, K.*; Oikawa, Kenichi; Toh, Yosuke; Kimura, Atsushi; Ikeda, Yujiro

Nuclear Instruments and Methods in Physics Research A, 903, p.38 - 45, 2018/09

 Times Cited Count:4 Percentile:24.89(Instruments & Instrumentation)

Journal Articles

Present fabrication status of spare moderators and reflector in J-PARC spallation neutron source

Teshigawara, Makoto; Harada, Masahide; Oi, Motoki; Takada, Hiroshi

Journal of Physics; Conference Series, 1021(1), p.012061_1 - 012061_4, 2018/06

 Times Cited Count:0 Percentile:100

At the spallation neutron source of J-PARC, the structural material of moderators and reflector, such as an aluminum alloy, is going to reach to the design value (20 DPA) around 2020 by an accumulation of irradiation-damage. We started the fabrication of the spare moderators and reflector in 2013 with following design of two improvements. The invar joints, such as invar-A6061 and invar- SS316L joints were newly developed to utilize them in the cryogenic multi-layered pipe with 5th annular geometry, improving the fabrication procedure much simple. The Gold-Indium-Cadmium (Au-In-Cd) as a decoupler material is also developed to reduce residual radioactivity of the used components significantly for the decoupled moderator. In this presentation, we will report these results and progress of fabrication.

Journal Articles

Implementation of a low-activation Au-In-Cd decoupler into the J-PARC 1 MW short pulsed spallation neutron source

Teshigawara, Makoto; Ikeda, Yujiro; Oi, Motoki; Harada, Masahide; Takada, Hiroshi; Kakishiro, Masanori*; Noguchi, Gaku*; Shimada, Tsubasa*; Seita, Kyoichi*; Murashima, Daisuke*; et al.

Nuclear Materials and Energy (Internet), 14, p.14 - 21, 2018/01

 Times Cited Count:0 Percentile:100(Nuclear Science & Technology)

We developed an Au-In-Cd (AuIC) decoupler material to reduce induced radioactivity instead of Ag-In-Cd one, which has a cut off energy of 1eV. In order to implement it into an actual moderator-reflector assembly, a number of critical engineering issues need to be resolved with regard to large-sized bonding between AuIC and A5083 alloys by the hot isostatic pressing process. We investigated this process in terms of the surface conditions, sizes, and heat capacities of large AuIC alloys. We also show a successful implementation of an AuIC decoupler into a reflector assembly, resulting in a remarkable reduction of radioactivity by AuIC compared to AIC without sacrificing neutronic performance.

Journal Articles

Materials and Life Science Experimental Facility at the Japan Proton Accelerator Research Complex, 1; Pulsed spallation neutron source

Takada, Hiroshi; Haga, Katsuhiro; Teshigawara, Makoto; Aso, Tomokazu; Meigo, Shinichiro; Kogawa, Hiroyuki; Naoe, Takashi; Wakui, Takashi; Oi, Motoki; Harada, Masahide; et al.

Quantum Beam Science (Internet), 1(2), p.8_1 - 8_26, 2017/09

At the Japan Proton Accelerator Research Complex (J-PARC), a pulsed spallation neutron source provides neutrons with high intensity and narrow pulse width to promote researches on a variety of science in the Materials and life science experimental facility. It was designed to be driven by the proton beam with an energy of 3 GeV, a power of 1 MW at a repetition rate of 25 Hz, that is world's highest power level. A mercury target and three types of liquid para-hydrogen moderators are core components of the spallation neutron source. It is still on the way towards the goal to accomplish the operation with a 1 MW proton beam. In this paper, distinctive features of the target-moderator-reflector system of the pulsed spallation neutron source are reviewed.

Journal Articles

R&D of invar duct for fabrication of 2nd JSNS moderators

Harada, Masahide; Teshigawara, Makoto; Maekawa, Fujio; Oi, Motoki; Kasugai, Yoshimi; Takada, Hiroshi

Journal of Nuclear Materials, 450(1-3), p.104 - 109, 2014/07

 Times Cited Count:1 Percentile:87.72(Materials Science, Multidisciplinary)

Japan Spallation Neutron Source (JSNS) in Japan Proton Accelerator Research Complex (J-PARC) has three super-critical hydrogen moderators. The moderator piping has a multilayer structure; a cryogenic layer, a vacuum layer, a helium layer and a cooling water layer. Through the fabrication of the current (1st) moderators, we learned that thermal shrinkage between room temperature (R.T.) and cryogenic temperature at the cryogenic layer made the fabrication process very difficult. Therefore, for the spare (2nd) moderators, we proposed to use a low thermal shrinkage material, Invar, as a piping material. However, there were items to be solved for realizing the Invar duct inview of the fabrication. In this presentation, we report results of (1) Bending test, (2) Welding test and (3) Dissimilar joint test on the Invar duct. (1) In the bending test, the Invar ducts of 22 mm in diameter and 1.5 mm in thickness were tried to be bent into an elbow with 40 mm in radius. By pre-cooling the duct in the liquid nitrogen followed by the bending with slow speed (1 minute), the duct could be bent without any cracks. (2) Through some welding testes by TIG-welding, the proper groove geometry was determined. (3) For the dissimilar joint test, tensile specimens including a bonding region having size of 4 or 6 mm in diameter at the smallest part and 60 mm in length were cut from three rods made by Invar-A6061 and Invar-SS316L, respectively. Those rods were bonded by the friction welding. All specimens were examined at two temperatures, R.T. and 77 K (liquid nitrogen temperature), resulting that 0.2% proof stresses corresponding to the bonding strengths were larger than those of base materials for both the Invar-A6061 and the Invar-SS316L cases. The present result indicates that the Invar duct is available for the 2nd moderators.

Journal Articles

Development of Au-In-Cd decoupler by a Hot Isostatic Pressing (HIP) technique for short pulsed spallation neutron source

Oi, Motoki; Teshigawara, Makoto; Harada, Masahide; Naoe, Takashi; Maekawa, Fujio; Kasugai, Yoshimi

Journal of Nuclear Materials, 450(1-3), p.117 - 122, 2014/07

 Times Cited Count:3 Percentile:67.39(Materials Science, Multidisciplinary)

In order to utilize Au-In-Cd alloy as a decoupler, it is required to bond between the Au-In-Cd alloy and aluminum alloy with enough bonding strength (more than 30 MPa). We adopted a Hot Isostatic Pressing (HIP) technique to realize bonding between Au-In-Cd and aluminum alloy, because it is available for curved shape of moderator vessel. As a HIP conditions of the temperature of 535 $$^{circ}$$C, pressure of 100 MPa and holding time of 1 hour, we got enough tensile strength of the bonding surface (86.6 MPa). It is larger than the required strength of 30 MPa.

Journal Articles

Neutron resonance imaging of a Au-In-Cd alloy for the JSNS

Oi, Motoki; Teshigawara, Makoto; Kai, Tetsuya; Harada, Masahide; Maekawa, Fujio; Futakawa, Masatoshi; Hashimoto, Eiko*; Segawa, Mariko; Kureta, Masatoshi; Tremsin, A.*; et al.

Physics Procedia, 43, p.337 - 342, 2013/04

 Times Cited Count:6 Percentile:6.65

The Japan Spallation Neutron Source (JSNS) at the Japan Proton Accelerator Research Complex (J-PARC) had been developed as a 1-MW spallation neutron source. A Au-In-Cd alloy has been proposed as a new decoupler material. Recently, we successfully produced the ternary Au-In-Cd alloy. The alloy composition is 74.9 at% Au, 0.5 at% In, and 24.6 at% Cd. We used the pulsed neutron imaging techniques to measure the elements in the Au-In-Cd alloy. Both a time gated camera system and a multi-channel plate (MCP) detector were used as detectors. Measurement was performed at BL10 in the JSNS. A Au-In-Cd specimen, In foil and two Au foils are used as a sample. As a results, we could obtain distribution of Au, In and Cd in the Au-In-Cd specimens distinctly.

Journal Articles

Probing carbon edge exposure of iron phthalocyanine-based oxygen reduction catalysts by soft X-ray absorption spectroscopy

Niwa, Hideharu*; Saito, Makoto*; Kobayashi, Masaki*; Harada, Yoshihisa*; Oshima, Masaharu*; Moriya, Shogo*; Matsubayashi, Katsuyuki*; Nabae, Yuta*; Kuroki, Shigeki*; Ikeda, Takashi; et al.

Journal of Power Sources, 223, p.30 - 35, 2013/02

 Times Cited Count:16 Percentile:42.68(Chemistry, Physical)

To design non-platinum, inexpensive, but high performance carbon-based cathode catalysts for polymer electrolyte fuel cells, it is important to elucidate the active site for oxygen reduction reaction (ORR). However, it is difficult to directly identify the active site by applying conventional structural or electronic probes to such complex systems. Here, we used C 1${it s}$ X-ray absorption spectroscopy (XAS) to observe electronic structure of carbon in iron phthalocyanine-based catalysts, and found a signature of edge exposure below the $$pi^{ast}$$ edge, whose intensity is well correlated with the ORR activity. These results demonstrate that C 1${it s}$ XAS can be used to characterize the ORR activity of carbon-based cathode catalysts in terms of the edge exposure.

Journal Articles

Development status of low activation ternary Au-In-Cd alloy decoupler for a MW class spallation neutron source; 1st production of Au-In-Cd alloy

Oi, Motoki; Teshigawara, Makoto; Wakui, Takashi; Nishi, Tsuyoshi; Harada, Masahide; Maekawa, Fujio; Futakawa, Masatoshi

Journal of Nuclear Materials, 431(1-3), p.218 - 223, 2012/12

 Times Cited Count:6 Percentile:47.81(Materials Science, Multidisciplinary)

The Japan Spallation Neutron Source (JSNS) at the Japan Proton Accelerator Research Complex (J-PARC) is developed as a 1 MW spallation neutron source. The Ag-In-Cd (AIC) alloy was adopted as a decoupler material for two decoupled moderators. A high decoupling energy at 1 eV was for the first time achieved in MW class spallation neutron source due to the adoption of the AIC alloy. Although the AIC decoupler is superior in the neutronic performance, it has a demerit in high residual radioactivity due to production of Ag-110m and Ag-108m. To overcome this demerit, Au-In-Cd alloy was proposed. We studied to make ternary Au-In-Cd alloy and successfully done it at the maximum temperature of 1123 K with diffusion of the cadmium into the gold. Uniformity of the alloy was confirmed with EDX analysis. Thermal conductivity of Au-In-Cd alloy was 87.7 W/m/K. These results show enough performance as a decoupler.

JAEA Reports

Maintenance of used components in spallation neutron source; Moderator $$cdot$$ reflector and proton beam window

Teshigawara, Makoto; Kinoshita, Hidetaka; Wakui, Takashi; Meigo, Shinichiro; Seki, Masakazu; Harada, Masahide; Ito, Manabu; Suzuki, Toru; Ikezaki, Kiyomi; Maekawa, Fujio; et al.

JAEA-Technology 2012-024, 303 Pages, 2012/07

JAEA-Technology-2012-024.pdf:46.04MB

3 GeV Protons with 1 MW beam power are irradiated to mercury target of spallation neutron source in Materials and Life science Facility (MLF), which is one of facilities of J-PARC. Irradiated components, such as target container, moderator, reflector and proton beam window, are needed to replace periodically due to irradiation damage of high energy protons and neutrons. These used components are replaced remotely because of highly activated. Maintenance scenario was settled so as to handle these components. Required remote handling machines were designed and installed in hot cell and other room of the MLF. We performed remote handling tests by using actual components to confirm the design. We report results, such as replacement procedure, trouble and its solution, etc., for moderator, reflector and proton beam window in order to provide the handling of actual used components.

Journal Articles

Indirect contribution of transition metal towards oxygen reduction reaction activity in iron phthalocyanine-based carbon catalysts for polymer electrolyte fuel cells

Kobayashi, Masaki*; Niwa, Hideharu*; Saito, Makoto*; Harada, Yoshihisa*; Oshima, Masaharu*; Ofuchi, Hironori*; Terakura, Kiyoyuki*; Ikeda, Takashi; Koshigoe, Yuka*; Ozaki, Junichi*; et al.

Electrochimica Acta, 74, p.254 - 259, 2012/07

 Times Cited Count:44 Percentile:16.16(Electrochemistry)

The electronic structure of the residual metal atoms in FePc-based carbon catalysts, prepared by pyrolyzing a mixture of FePc and phenolic resin polymer at 800$$^{circ}$$C, before and after acid washing have been investigated using XAFS spectroscopy to clarify the role of Fe in the ORR activity. The decomposition analyses for the XAFS spectra reveal that the composition ratio of each Fe component is unaltered by the acid washing, indicating that the residual Fe components were removed by the acid washing irrespective of their chemical states. Because the oxygen reduction potential was approximately unchanged by the acid washing, the residual Fe itself does not seem to contribute directly to the ORR activity. The residual Fe can act as a catalyst to accelerate the growth of the sp$$^{2}$$ carbon network during pyrolysis. The results imply that light elements are components of the ORR active sites in the FePc-based carbon catalysts.

JAEA Reports

Influence of Great East Japan Earthquake on neutron source station in J-PARC

Sakai, Kenji; Sakamoto, Shinichi; Kinoshita, Hidetaka; Seki, Masakazu; Haga, Katsuhiro; Kogawa, Hiroyuki; Wakui, Takashi; Naoe, Takashi; Kasugai, Yoshimi; Tatsumoto, Hideki; et al.

JAEA-Technology 2011-039, 121 Pages, 2012/03

JAEA-Technology-2011-039.pdf:10.87MB

This report investigates the behavior, damage and restoration of a neutron source station of the MLF at the Great East Japan Earthquake and verified the safety design for emergency accidents in the neutron source station. In the MLF, after an occurrence of the Earthquake, strong quakes were detected at the instruments, the external power supply was lost, all of the circulators shut down automatically, and the hydrogen gas was released. The leakages of mercury, hydrogen and radio-activation gases did not occur. While, the quakes made gaps between the shield blocks and ruptured external pipe lines by subsidence around the building. But significant damages to the components were not found though the pressure drop of compressed air lines influenced on a target trolley lock system and so on. These results substantiated the validity of the safety design for emergency accidents in the source station, and suggested several points of improvement.

Journal Articles

Influence of Great East Japan Earthquake on neutron target station in J-PARC

Sakai, Kenji; Futakawa, Masatoshi; Takada, Hiroshi; Sakamoto, Shinichi; Maekawa, Fujio; Kinoshita, Hidetaka; Seki, Masakazu; Haga, Katsuhiro; Kogawa, Hiroyuki; Wakui, Takashi; et al.

Proceedings of 20th Meeting of the International Collaboration on Advanced Neutron Sources (ICANS-20) (USB Flash Drive), 6 Pages, 2012/03

This report investigates behaviors and damages of each component in a neutron target station of the MLF at the J-PARC at the time of the Great East Japan Earthquake (GEJE). At the date of the GEJE, in the MLF, strong quakes were detected at several instruments, an external power supply were lost, all of the circulation systems were shut down automatically, and a hydrogen gas was released as planned. Leakage of activation liquids and gases did not occur. While, the quakes made gaps between shield blocks and ruptured external pipe lines for air and water by subsidence. But significant damages on the components of the target station were not found though a loss of compressed air supply affected lock systems with air cylinders and pneumatic operation values. These results substantiated a validity of safety design on the target station for emergency accidents.

Journal Articles

Explanation of question and answer in special subject examination of the first test for professional engineer "nuclear and radiation" executed in 2010 fiscal year, Part 2; Nuclear section

Natsume, Tomohiro*; Nakano, Makoto*; Harada, Akio; Yamanaka, Atsushi; Kurihara, Ryoichi

Genshiryoku eye, 57(4), p.72 - 76, 2011/04

no abstracts in English

Journal Articles

First neutron production utilizing J-PARC pulsed spallation neutron source JSNS and neutronic performance demonstrated

Maekawa, Fujio; Harada, Masahide; Oikawa, Kenichi; Teshigawara, Makoto; Kai, Tetsuya; Meigo, Shinichiro; Oi, Motoki; Sakamoto, Shinichi; Takada, Hiroshi; Futakawa, Masatoshi; et al.

Nuclear Instruments and Methods in Physics Research A, 620(2-3), p.159 - 165, 2010/08

 Times Cited Count:54 Percentile:2.58(Instruments & Instrumentation)

The J-PARC 1-MW pulsed spallation neutron source JSNS was successfully launched on 30th of May 2008. To demonstrate the unique features of the moderator design and the neutronic performance of JSNS the neutron spectral intensity, absolute neutron flux, and time structure of the neutron pulse shapes etc have been measured using several neutron instruments since then. The measured energy spectra clearly revealed the feature of the para-hydrogen, as expected when designing the moderator. The measured neutron flux below 0.4 eV agreed with the corresponding design value within $$pm$$20%, thus suggesting that the JSNS design calculations to have been reliable. World-class high-resolution diffraction data could be recorded due to the suitability of design of the moderators and the instruments. Another world-class high-intensity neutron flux was also capable of being demonstrated due to the unique design of the large cylindrical coupled moderator.

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