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JAEA Reports

Improvement of accumulator in cryogenic hydrogen system used for 1-MW pulsed spallation neutron source

Aso, Tomokazu; Tatsumoto, Hideki*; Otsu, Kiichi*; Kawakami, Yoshihiko*; Komori, Shinji*; Muto, Hideki*; Takada, Hiroshi

JAEA-Technology 2019-013, 77 Pages, 2019/09

JAEA-Technology-2019-013.pdf:5.59MB

At Materials and Life Science experimental Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC), a 1-MW pulsed spallation neutron source is equipped with a cryogenic hydrogen system which circulates liquid hydrogen (20 K and 1.5 MPa) to convert high energy neutrons generated at a mercury target to cold neutrons at three moderators with removing nuclear heat of 3.8 kW deposited there. The cryogenic system includes an accumulator with a bellows structure in order to absorb pressure fluctuations generated by the nuclear heat deposition in the system. Welded inner bellows of the first accumulator was failured during operation, forcing us to improve the accumulater to have sufficient pressure resistance and longer life-time. We have developed elemental technologies for manufacturing welded bellows of the accumulator by a thick plate with high pressure resistance, succeeding to find optimum welding conditions. We fabricated a prototype bellows block and carried out an endurance test by adding a pressure change of 2 MPa repeatedly. As a result, the prototype bellows was successfully in use exceeding the design life of 10,000 times. Since distortions given during welding and assembling affect functionality and lifetime of the bellows, we set the levelness of each element of the bellows as within 0.1$$^{circ}$$. The improved accumulator has already been in operation for about 25,000 hours as of January 2019, resulting that the number of strokes reached to 16,000. In July 2018, we demonstrated that the accumulator could suppress the pressure fluctuation generated by the 932 kW beam injection as designed. As current operational beam power is 500 kW, the current cryogenic hydrogen system could be applicable for stable operation at higher power in the future.

JAEA Reports

Development of prototype for TEF-T integral control system of J-PARC

Sakai, Kenji; Obayashi, Hironari; Saito, Shigeru; Sasa, Toshinobu; Sugawara, Takanori; Watanabe, Akihiko*

JAEA-Technology 2019-009, 18 Pages, 2019/07

JAEA-Technology-2019-009.pdf:2.34MB

Construction of Transmutation Experimental Facility (TEF) is under planning in the Japan Proton Accelerator Research Complex (J-PARC) program to promote R&D on the transmutation technology with using accelerator driven systems (ADS). ADS Target Test Facility (TEF-T) in TEF will develop spallation target technology and study on target materials with irradiating high intensity proton beams on a lead-bismuth eutectic (LBE) target. For safe and efficient beam operation, a general control system (GCS) will be constructed in TEF-T. GCS comprises several subsystems, such as a network system (LAN), an integral control system (ICS), an interlock system (ILS), and a timing distribution system (TDS) according to their roles. Especially, the ICS plays the important role that executes integral operations in the entire facility, acquires, stores and distributes operation data. We planned to develop a prototype of the ICS, to evaluate its concrete performances such as data transmission speeds, data storage capability, control functions, long-term stability of the system, and to utilize them for design of the actual ICS. This report mentions to product the prototype of ICS and to apply it to remote operations of instruments for developing LBE target technology.

Journal Articles

Beam dynamics study for beam loss mitigation in the J-PARC RCS

Hotchi, Hideaki; Harada, Hiroyuki; Okabe, Kota; Saha, P. K.; Shobuda, Yoshihiro; Tamura, Fumihiko; Yoshimoto, Masahiro

Kasokuki, 16(2), p.109 - 118, 2019/07

no abstracts in English

Journal Articles

Background issues encountered by cold-neutron chopper spectrometer AMATERAS

Kikuchi, Tatsuya*; Nakajima, Kenji; Kawamura, Seiko; Inamura, Yasuhiro; Nakamura, Mitsutaka; Wakai, Daisuke*; Aoyama, Kazuhiro*; Iwahashi, Takaaki*; Kambara, Wataru*

Physica B; Condensed Matter, 564, p.45 - 53, 2019/07

Details of the background, that is, unwanted signals accumulated by the data acquisition system of neutron instruments, observed by the cold-neutron chopper spectrometer AMATERAS installed at the Materials and Life Science Experimental Facility at J-PARC are reported. In the design phase of AMATERAS, we carefully considered the achievement of high signal-to-noise ratio, and possible countermeasures were implemented. Actually, recent scientific outputs from AMATERAS indicates that the spectrometer is one of excellent neutron instruments with low background. In spite of that, in nine years of AMATERAS operation, we have encountered unwanted signals due to various reasons, including gamma-rays emitted at materials on or near the beam line including the sample itself, scattered neutrons from the beam line devices, air scattering, electronic noise in data acquisition system, cosmic rays, T0 burst, and other unknown sources. In this report, we discuss the background observed by AMATERAS, especially in the conditions of without samples, comprehensively. The possible sources of these signals and the countermeasures considered against the above sources are discussed, which may be helpful to those who are engaged in other existing or planned neutron-scattering instruments.

Journal Articles

Localized magnetic excitations in the fully frustrated dimerized magnet Ba$$_{2}$$CoSi$$_{2}$$O$$_{6}$$Cl$$_{2}$$

Kurita, Nubuyuki*; Yamamoto, Daisuke*; Kanesaka, Takuya*; Furukawa, Nobuo*; Kawamura, Seiko; Nakajima, Kenji; Tanaka, Hidekazu*

Physical Review Letters, 123(2), p.027206_1 - 027206_6, 2019/07

JAEA Reports

Assessment report on research and development activities in FY 2018; Activity "Research and development on J-PARC" (Interim report)

J-PARC Center

JAEA-Evaluation 2019-003, 52 Pages, 2019/06

JAEA-Evaluation-2019-003.pdf:6.61MB

Evaluation Committee of Research Activities for J-PARC for interim assessment of Japan Proton Accelerator Research Complex evaluated the management and research activities of J-PARC center on the explanatory documents and oral presentations during the period from April 2015 to December 2018. This report summarizes the results of the assessment by the Committee with the Committee report attached.

Journal Articles

Measurements of the $$^{243}$$Am neutron capture and total cross sections with ANNRI at J-PARC

Kimura, Atsushi; Nakamura, Shoji; Terada, Kazushi*; Nakao, Taro*; Mizuyama, Kazuhito*; Iwamoto, Nobuyuki; Iwamoto, Osamu; Harada, Hideo; Katabuchi, Tatsuya*; Igashira, Masayuki*; et al.

Journal of Nuclear Science and Technology, 56(6), p.479 - 492, 2019/06

Journal Articles

Evidence for singular-phonon-induced nematic superconductivity in a topological superconductor candidate Sr$$_{0.1}$$Bi$$_{2}$$Se$$_{3}$$

Wang, J.*; Ran, K.*; Li, S.*; Ma, Z.*; Bao, S.*; Cai, Z.*; Zhang, Y.*; Nakajima, Kenji; Kawamura, Seiko; $v{C}$erm$'a$k, P.*; et al.

Nature Communications (Internet), 10, p.2802_1 - 2802_6, 2019/06

Journal Articles

Triplon band splitting and topologically protected edge states in the dimerized antiferromagnet

Nawa, Kazuhiro*; Tanaka, Kimihito*; Kurita, Nubuyuki*; Sato, Taku*; Sugiyama, Haruki*; Uekusa, Hidehiro*; Kawamura, Seiko; Nakajima, Kenji; Tanaka, Hidekazu*

Nature Communications (Internet), 10, p.2096_1 - 2096_8, 2019/05

Search for topological materials has been actively promoted in the field of condensed matter physics for their potential application in energy-efficient information transmission and processing. Recent studies have revealed that topologically invariant states, such as edge states in topological insulators, can emerge not only in a fermionic electron system but also in a bosonic system, enabling nondissipative propagation of quasiparticles. Here we report the topologically nontrivial triplon bands measured by inelastic neutron scattering on the spin-1/2 two-dimensional dimerized antiferromagnet Ba$$_{2}$$CuSi$$_{2}$$O$$_{6}$$Cl$$_{2}$$. The excitation spectrum exhibits two triplon bands that are clearly separated by a band gap due to a small alternation in interdimer exchange interaction, consistent with a refined crystal structure. By analytically modeling the triplon dispersion, we show that Ba$$_{2}$$CuSi$$_{2}$$O$$_{6}$$Cl$$_{2}$$ is the first bosonic realization of the coupled Su-Schrieffer-Heeger model, where the presence of topologically protected edge states is prompted by a bipartite nature of the lattice.

Journal Articles

Coexistence of ferromagnetic and stripe-type antiferromagnetic spin fluctuations in YFe$$_{2}$$Ge$$_{2}$$

Wo, H.*; Wang, Q.*; Shen, Y.*; Zhang, X.*; Hao, Y.*; Feng, Y.*; Shen, S.*; He, Z.*; Pan, B.*; Wang, W.*; et al.

Physical Review Letters, 122(21), p.217003_1 - 217003_5, 2019/05

Journal Articles

Colossal barocaloric effects in plastic crystals

Li, B.*; Kawakita, Yukinobu; Kawamura, Seiko; Sugahara, Takeshi*; Wang, H.*; Wang, J.*; Chen, Y.*; Kawaguchi, Saori*; Kawaguchi, Shogo*; Ohara, Koji*; et al.

Nature, 567(7749), p.506 - 510, 2019/03

Refrigeration is of vital importance for modern society for example, for food storage and air conditioning- and 25 to 30% of the world's electricity is consumed for refrigeration. Current refrigeration technology mostly involves the conventional vapour compression cycle, but the materials used in this technology are of growing environmental concern because of their large global warming potential. As a promising alternative, refrigeration technologies based on solid-state caloric effects have been attracting attention in recent decades. However, their application is restricted by the limited performance of current caloric materials, owing to small isothermal entropy changes and large driving magnetic fields. Here we report colossal barocaloric effects (CBCEs) (barocaloric effects are cooling effects of pressure-induced phase transitions) in a class of disordered solids called plastic crystals. The obtained entropy changes in a representative plastic crystal, neopentylglycol, are about 389 joules per kilogram per kelvin near room temperature. Pressure-dependent neutron scattering measurements reveal that CBCEs in plastic crystals can be attributed to the combination of extensive molecular orientational disorder, giant compressibility and highly anharmonic lattice dynamics of these materials. Our study establishes the microscopic mechanism of CBCEs in plastic crystals and paves the way to next-generation solid-state refrigeration technologies.

Journal Articles

Numerical study on the potential of cavitation damage in a lead-bismuth eutectic spallation target

Wan, T.; Naoe, Takashi; Kogawa, Hiroyuki; Futakawa, Masatoshi; Obayashi, Hironari; Sasa, Toshinobu

Materials, 12(4), p.681_1 - 681_15, 2019/02

Journal Articles

"$$K^-pp$$", a $$bar K$$-meson nuclear bound state, observed in $$^3$$He($$K^-,Lambda p)n$$ reactions

Hashimoto, Tadashi; Tanida, Kiyoshi; 67 of others*

Physics Letters B, 789, p.620 - 625, 2019/02

 Percentile:100(Astronomy & Astrophysics)

We observed a distinct peak in the $$Lambda p$$ invariant mass spectrum of $$^{3}{rm He}(K^-, , Lambda p)n$$, well below $$m_K + 2m_p$$, $$i.e.$$, the mass threshold of the $$K^-$$ to be bound to two protons. By selecting a relatively large momentum-transfer region $$q = 350 sim650$$ MeV/$$c$$, one can clearly separate the peak from the quasi-free process,$$overline{K}N rightarrow overline{K}N$$ followed by the non-resonant absorption by the non-resonant absorption by the two spectator-nucleons $$overline{K}NN rightarrow Lambda N$$. We found that the simplest fit to the observed peak gives us a Breit-Wignerpole position at $$B_{rm {it Kpp}} = 47 pm 3 , (stat.) ,^{+3}_{-6},(sys.)$$ MeV having a width $$Gamma_{rm {it Kpp}} = 115 pm 7 , (stat.),^{+10}_{-20} ,(sys.)$$ MeV, and the $$S$$-wave Gaussian reaction form-factor parameter $$Q_{rm {it Kpp}} = 381 pm 14 , (stat.),^{+57}_{-0} ,(sys.)$$MeV/$$c$$, as a new form of the nuclear bound system with strangeness -"$$K^-pp$$".

JAEA Reports

Progress of general control system for Materials and Life Science Experimental Facility at J-PARC

Sakai, Kenji; Oi, Motoki; Takada, Hiroshi; Kai, Tetsuya; Nakatani, Takeshi; Kobayashi, Yasuo*; Watanabe, Akihiko*

JAEA-Technology 2018-011, 57 Pages, 2019/01

JAEA-Technology-2018-011.pdf:4.98MB

For safely and efficiently operating a spallation neutron source and a muon target, a general control system (GCS) operates within Materials and Life Science Experimental Facility (MLF). GCS administers operation processes and interlocks of many instruments. It consists of several subsystems such as an integral control system (ICS), interlock systems (ILS), shared servers, network system, and timing distribution system (TDS). Although GCS is an independent system that controls the target stations, it works closely with the control systems of the accelerators and other facilities in J-PARC. Since the first beam injection, GCS has operated stably without any serious troubles after modification based on commissioning for operation and control. Then, significant improvements in GCS such as upgrade of ICS by changing its framework software and function enhancement of ILS were proceeded until 2015. In this way, many modifications have been proceeded in the entire GCS during a period of approximately ten years after start of beam operation. Under these situation, it is important to comprehend upgrade history and present status of GCS in order to decide its upgrade plan. This report summarizes outline, structure, roles and functions of GCS in 2017.

Journal Articles

Thermal-hydraulic analysis of the LBE spallation target head in JAEA

Wan, T.; Obayashi, Hironari; Sasa, Toshinobu

Nuclear Technology, 205(1-2), p.188 - 199, 2019/01

 Percentile:100(Nuclear Science & Technology)

Journal Articles

Spin correlations of quantum spin liquid and quadrupole-ordered states of Tb$$_{2+x}$$Ti$$_{2-x}$$O$$_{7+y}$$

Kadowaki, Hiroaki*; Wakita, Mika*; F${aa}$k, B.*; Ollivier, J.*; Kawamura, Seiko; Nakajima, Kenji; Lynn, J. W.*

Physical Review B, 99(1), p.014406_1 - 014406_12, 2019/01

Spin correlations of the frustrated pyrochlore oxide Tb$$_{2+x}$$Ti$$_{2-x}$$O$$_{7+y}$$ have been investigated by using inelastic neutron scattering on single-crystalline samples (x = -0.007, 0.000, and 0.003), which have the putative quantum-spin-liquid (QSL) or electric-quadrupolar ground states. Spin correlations, which are notably observed in nominally elastic scattering, show short-range correlations around $$Gamma$$ points, tiny antiferromagnetic Bragg scattering at L and $$Gamma$$ points, and pinch-point-type structures around $$Gamma$$ points. The short-range spin correlations were analyzed using a random-phase approximation (RPA) assuming the paramagnetic state and two-spin interactions among Ising spins. These analyses have shown that the RPA scattering intensity well reproduces the experimental data using temperature- and x-dependent coupling constants of up to tenth-neighbor site pairs. This suggests that no symmetry breaking occurs in the QSL sample and that a quantum treatment beyond the semiclassical RPA approach is required. Implications of the experimental data and the RPA analyses are discussed.

Journal Articles

Measurement of activation cross sections of aluminum for protons with energies between 0.4 GeV and 3.0 GeV at J-PARC

Matsuda, Hiroki; Meigo, Shinichiro; Iwamoto, Hiroki

Progress in Nuclear Science and Technology (Internet), 6, p.171 - 174, 2019/01

Activation cross sections of various materials are strongly required for the improvement of the accuracy of nuclear design and the reduction of the construction costs for spallation neutron sources and transmutation systems. Activation cross sections have been measured in several facilities. However, they have low accuracy and precision. Especially, there are merely experimental data with 3 GeV protons which are used for spallation neutron source (MLF) in J-PARC, the experimental data is required for the improvement of the target materials. Thus, we measured cross sections of tungsten, gold, indium, and beryllium with 0.4 GeV to 3.0 GeV protons. Moreover, ones of aluminium that are set with materials were also measured for a variation of this experiment. It was found that more accurate data than current ones would be measured by using precise beam controls and highly accurate beam monitoring. We compared the experimental data, the evaluated data (JENDL-HE/2007), and the calculations with several intra-nuclear cascade models by PHITS code. Although the experimental data agreed with JENDL-HE/2007, the calculations underestimated about 40%. This could come from the evaporation model (GEM) being included in PHITS code. We found that the calculations agreed with the experimental data by upgrading PHITS code. The cross sections for the other materials have been analysed so far.

Journal Articles

Progress of neutron-capture cross-section measurements promoted by ImPACT project at ANNRI in MLF of J-PARC

Nakamura, Shoji; Kimura, Atsushi; Hales, B. P.; Iwamoto, Osamu; Shibahara, Yuji*; Uehara, Akihiro*; Fujii, Toshiyuki*

JAEA-Conf 2018-001, p.199 - 203, 2018/12

Study on cross-section measurements has been promoted for $$^{135}$$Cs among long-lived fission products in ImPACT Project. The feasibility study on $$^{79}$$Se sample preparation also has been conducted to measure its cross sections in future. During the feasibility study, we started the neutron-capture cross-section measurements of stable Se isotopes. This paper reports research progresses on preparation of a radioactive $$^{135}$$Cs sample, neutron irradiation experiments with the Cs sample, and cross-section measurements of stable Se isotopes.

Journal Articles

High-energy magnetic excitations in lightly oxygen-doped lanthanum nickel oxides

Nakajima, Kenji; Kajimoto, Ryoichi

Physica B; Condensed Matter, 551, p.142 - 145, 2018/12

 Percentile:100(Physics, Condensed Matter)

Journal Articles

Al-impurity-induced magnetic excitations in heavily over-doped La$$_{1.7}$$Sr$$_{0.3}$$Cu$$_{0.95}$$Al$$_{0.05}$$O$$_{4}$$

Ikeuchi, Kazuhiko*; Nakajima, Kenji; Kawamura, Seiko; Kajimoto, Ryoichi; Wakimoto, Shuichi; Suzuki, Kensuke*; Fujita, Masaki*

AIP Advances (Internet), 8(10), p.101318_1 - 101318_5, 2018/10

By means of inelastic neutron scattering, we measured magnetic excitations in a sizable single crystal of La$$_{1.7}$$Sr$$_{0.3}$$Cu$$_{0.95}$$Al$$_{0.05}$$O$$_{4}$$, which is an Al-substituted system of the heavily hole-doped cuprate system La$$_{2-x}$$Sr$$_{x}$$CuO$$_{4}$$ with an effective concentration of holes of $$X_{rm eff}$$ = 0.25.

405 (Records 1-20 displayed on this page)