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Journal Articles

Short- and middle-ranges order structures of KNbO$$_3$$ nanocrystals

Yoneda, Yasuhiro; Kunisada, Ryoichi*; Chikada, Tsukasa*; Ueno, Shintaro*; Fujii, Ichiro*; Nagata, Hajime*; Ohara, Koji*; Wada, Satoshi*

Japanese Journal of Applied Physics, 58(SL), p.SLLA03_1 - SLLA03_7, 2019/11

Journal Articles

Dielectric and magnetocaloric study of TmCrO$$_{3}$$

Yoshii, Kenji; Ikeda, Naoshi*

Journal of Alloys and Compounds, 804, p.364 - 369, 2019/10

Dielectric and magnetocaloric measurements are carried out for the chromite TmCrO$$_{3}$$. This oxide was reported to be multiferroic below the N$'e$el temperature ($$T_{rm N}$$) of 125 K, likely due to a structural transformation. The dielectric response shows large dielectric constants below 300 K. However, from the analyses of loss tangent, AC conductivity and dielectric modulus, this behavior is rooted in hopping of charge carriers rather than electric dipoles, as proposed for some other chromites. No dielectric anomaly is found at $$T_{rm N}$$. The magnetocaloric effect shows that the magnetic transitions at $$T_{rm N}$$ as well as the spin reorientation temperature are of a second order. This result strongly suggests the absence of magnetostructural transition at $$T_{rm N}$$ in accord with no observation of ferroelectric transition at this temperature.

Journal Articles

Electronic structure of UTe$$_2$$ studied by photoelectron spectroscopy

Fujimori, Shinichi; Kawasaki, Ikuto; Takeda, Yukiharu; Yamagami, Hiroshi; Nakamura, Ai*; Homma, Yoshiya*; Aoki, Dai*

Journal of the Physical Society of Japan, 88(10), p.103701_1 - 103701_5, 2019/10

Journal Articles

Numerical simulation of laser welding different kinds of materials using a thermohydraulics computational science numerical simulation code SPLICE

Muramatsu, Toshiharu; Sato, Yuji; Kamei, Naomitsu; Aoyagi, Yuji*; Shobu, Takahisa

Nippon Kikai Gakkai Dai-13-Kai Seisan Kako, Kosaku Kikai Bumon Koenkai Koen Rombunshu (No.19-307) (Internet), p.157 - 160, 2019/10

no abstracts in English

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.

Journal Articles

Direct observation of electronic structure change by resistance random access memory effect in amorphous alumina

Kubota, Masato; Nigo, Seisuke*; Kato, Seiichi*; Amemiya, Kenta*

AIP Advances (Internet), 9(9), p.095050_1 - 095050_4, 2019/09

We measured the X-ray absorption spectra of amorphous alumina with vacancy-type oxygen defects which exhibits the resistance random access memory effect. For the first time, we detected changes in the electronic structure owing to the memory effect. A major difference in spectrum was observed near the O K-absorption edge.

Journal Articles

Magnetic field induced triple-$$q$$ magnetic order in trillium lattice antiferromagnet EuPtSi studied by resonant X-ray scattering

Tabata, Chihiro*; Matsumura, Takeshi*; Nakao, Hironori*; Michimura, Shinji*; Kakihana, Masashi*; Inami, Toshiya*; Kaneko, Koji; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*

Journal of the Physical Society of Japan, 88(9), p.093704_1 - 093704_5, 2019/09

Journal Articles

Multiharmonic vector rf voltage control for wideband cavities driven by vacuum tube amplifiers in a rapid cycling synchrotron

Tamura, Fumihiko; Sugiyama, Yasuyuki*; Yoshii, Masahito*; Yamamoto, Masanobu; Omori, Chihiro*; Nomura, Masahiro; Shimada, Taihei; Hasegawa, Katsushi*; Hara, Keigo*; Furusawa, Masashi*

Physical Review Accelerators and Beams (Internet), 22(9), p.092001_1 - 092001_22, 2019/09

Beam loading compensation in the rf cavities is a key for acceleration of high intensity beams in 3 GeV RCS of the J-PARC. Since we employ wideband magnetic alloy rf cavities for the J-PARC RCS and the wake voltage contains several harmonics, a multiharmonic beam loading compensation is required. The multiharmonic rf feedforward for the most important six harmonics is implemented in the existing low level rf (LLRF) control system, which has been working fairly well for acceleration of high intensity beams of up to 1 MW. However, we found the degradation of the performance for compensation of the feedforward with very high intensity beams. Therefore, a multiharmonic vector rf voltage control has been developed. The detail of system configuration, commissioning methodology, and beam test results using very high intensity beams are described. The beam loading by the 1~MW equivalent beam in the cavity is successfully compensated.

Journal Articles

Structure change of monoclinic ZrO$$_{2}$$ baddeleyite involving softenings of bulk modulus and atom vibrations

Fukui, Hiroshi*; Fujimoto, Manato*; Akahama, Yuichi*; Sano, Asami; Hattori, Takanori

Acta Crystallographica Section B; Structural Science, Crystal Engineering and Materials (Internet), 75(4), p.742 - 749, 2019/08

Monoclinic ZrO$$_{2}$$ baddeleyite exhibits anomalous softenings of bulk modulus and atom vibrations with compression. We have investigated the pressure evolution of the structure by neutron powder diffraction combined with ab-initio calculations. The present results showed that the anomalous pressure response of the bulk modulus is related not to the change in the bonding characters but to the deformation of an oxygen sublattice, especially one of layers made of oxygens in the crystallographic $$a$$* plane. The layer consists of two parallelograms; one is rotating with little distortion and the other is being distorted with increasing pressure. This deformation of this layer makes one of Zr-O distances long, resulting in the softening of some atom vibrational modes.

Journal Articles

Evaluation growing and collapsing behaviors of cavitation bubbles under flowing condition

Kawamura, Shunsuke; Naoe, Takashi; Ikeda, Tsubasa*; Tanaka, Nobuatsu*; Futakawa, Masatoshi

Advanced Experimental Mechanics, 4, p.33 - 37, 2019/08

A mercury enclosure vessel made of stainless steel is used as a spallation target in the pulsed spallation neutron source at J-PARC. It is severely damaged by the cavitation induced with pressure waves in association with the pulsed proton beam injection. A double-walled structure with a narrow mercury channel was adopted in the front end of the target vessel to reduce the cavitation damage. It has been experimentally demonstrated that the cavitation damage could be mitigated in the narrow channel but its mechanism has been unclarified yet. In this study, we investigated the cavitation from growing to collapsing through visualizing the spark-induced cavitation bubbles under flow field using a high-speed video camera. Furthermore, we measured the wall vibration due to the cavitation bubble collapse with changing flow velocity parametrically. It was found that the microjet collided perpendicular to the wall in the stagnant flow condition while it collided with an inclined angle from the perpendicular direction, suggesting that the collision pressure on the wall was reduced by flowing.

Journal Articles

Coherent magnetization rotation of a layered system observed by polarized neutron scattering under grazing incidence geometry

Maruyama, Ryuji; Bigault, T.*; Saerbeck, T.*; Honecker, D.*; Soyama, Kazuhiko; Courtois, P.*

Crystals, 9(8), p.383_1 - 383_13, 2019/08

The in-plane magnetic structure of a layered system composed of polycrystalline grains smaller than the ferromagnetic exchange length was studied to elucidate the mechanism controlling the magnetic properties considerably different from the bulk using polarized neutron scattering under grazing incidence geometry. The measured result, together with quantitative analysis based on the distorted wave Born approximation, showed that the in-plane length of the area with uniform orientation of moments ranging from 0.5 to 1.1 $$mu$$m is not significantly varied during the process of demagnetization followed by remagnetization. The obtained behavior of moments is in good agreement with the two-dimensional random anisotropy model where coherent magnetization rotation is dominant.

Journal Articles

Dynamic properties of human $$alpha$$-synuclein related to propensity to amyloid fibril formation

Fujiwara, Satoru*; Kono, Fumiaki*; Matsuo, Tatsuhito*; Sugimoto, Yasunobu*; Matsumoto, Tomoharu*; Narita, Tetsuhiro*; Shibata, Kaoru

Journal of Molecular Biology, 431(17), p.3229 - 3245, 2019/08

$$alpha$$-synuclein ($$alpha$$Syn) is an intrinsically disordered protein (IDP) with unknown function. $$alpha$$Syn is known to form amyloid fibrils, which are implicated with the pathogenesis of Parkinson's disease and other synucleinopathies. Elucidating the mechanism of fibril formation of $$alpha$$Syn is therefore important for understanding the mechanism of the pathogenesis of these diseases. Here, using the quasielastic neutron scattering (QENS) and small-angle X-ray scattering (SAXS) techniques, we investigated the dynamic and structural properties of $$alpha$$Syn. These results imply that fibril formation of $$alpha$$Syn requires not only the enhanced local motions but also the segmental motions such that the proper inter-molecular interactions are possible.

Journal Articles

Journal Articles

Applicability and limitations of $$G(r,E)$$ analysis transformed from the inelastic neutron scattering data

Nakamura, Mitsutaka; Kikuchi, Tatsuya*; Kawakita, Yukinobu

Physica B; Condensed Matter, 567, p.61 - 64, 2019/08

Recently, we reported the phonon dynamical study of a polycrystalline NaI by using the dynamical structure factor in real-space $$G(r,E)$$ transformed from the inelastic neutron scattering (INS) data. Our study has shown that the INS experiments under the conventional condition Q$$_{max}$$ $$sim$$ 5$AA$^{-1}$$ can provide us a meaningful information on the phonon dynamics at around the first nearest neighbor distance on accepting the worse real-space resolution. These results suggest the possibility that a large amount of $$S(Q,E)$$ data which were previously obtained can be effectively reused. In this study, we will examine both the applicability and limitations of $$G(r,E)$$ analysis for various types of materials whose INS data were obtained at the Fermi chopper spectrometer 4SEASONS in J-PARC.

Journal Articles

Hexagonal close-packed iron hydride behind the conventional phase diagram

Machida, Akihiko*; Saito, Hiroyuki*; Hattori, Takanori; Sano, Asami; Funakoshi, Kenichi*; Sato, Toyoto*; Orimo, Shinichi*; Aoki, Katsutoshi*

Scientific Reports (Internet), 9(1), p.12290_1 - 12290_9, 2019/08

Hexagonal close-packed iron hydride, hcp FeHx, is absent from the conventional phase diagram of the Fe-H system, although hcp metallic Fe exists stably over extensive temperature ($$T$$) and pressure ($$P$$) conditions, including those corresponding to the Earth's inner core. ${{it In situ}}$ X-ray and neutron diffraction measurements at temperatures ranging from 298 to 1073 K and H pressures ranging from 4 to 7 GPa revealed that the hcp hydride was formed for FeH$$_{x}$$ compositions when $$x < 0.6$$. Hydrogen atoms occupied the octahedral interstitial sites of the host metal lattice both partially and randomly. The hcp hydride exhibited a H-induced volume expansion of 2.48(5) $AA $^{3}$$/H-atom, which was larger than that of the face-centered cubic (fcc) hydride. The hcp hydride showed an increase in $$x$$ with $$T$$, whereas the fcc hydride showed a corresponding decrease. The present study provides guidance for further investigations of the Fe-H system over an extensive $$x$$-$$T$$-$$P$$ region.

Journal Articles

Turbomolecular pump as main pump in a high-power proton accelerator vacuum system

Kamiya, Junichiro; Kinsho, Michikazu; Ogiwara, Norio*; Sakurai, Mitsuru*; Mabuchi, Takuya*; Wada, Kaoru*

Vacuum and Surface Science, 62(8), p.476 - 485, 2019/08

J-PARC 3GeV rapid cycling synchrotron (RCS) is one of the highest beam power proton accelerators. Challenges for achieving low pressure region in ultra-high vacuum (UHV) in the beam line are the large outgassing source. We focused turbo molecular pumps (TMP) as maing pump because it can evacuate the continuous and additional outgassing with large pumping speed in wide pressure range. It is also possible to evacuate from low vacuum to UHV with only a few hours by using TMP, which ensures users' experimental time after vacuum device maintenance. During more than 10 years operation of the vacuum system, many experiences have been accumulated about the usage of TMP in RCS. In this presentation, we discussed about validity of TMP as main pump in high power proton beam accelerator by showing the performance of the beam line pressure during the beam operation. Further, in anticipation of upgrade higher beam power more than 1 MW, validity of a combination of TMP and NEG pump will be mentioned.

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

Universality and structural implications of the Boson peak in Proteins

Nakagawa, Hiroshi; Jochi, Yasumasa*; Kitao, Akio*; Yamamuro, Osamu*; Kataoka, Mikio*

Biophysical Journal, 117(2), p.229 - 238, 2019/07

Softness and rigidity of proteins are reflected in the structural dynamics, which are in turn affected by the environment. The characteristic low-frequency vibrational spectrum of a protein, known as boson peak, is an indication of the structural rigidity of the protein at cryogenic temperature or dehydrated conditions. In this paper, the effect of hydration, temperature, and pressure on the boson peak and volumetric properties of a globular protein are evaluated by using inelastic neutron scattering and molecular dynamics simulation. Hydration, pressurization, and cooling shift the boson peak position to higher energy and depress the peak intensity and decreases the protein and cavity volumes, although pressure hardly affects the boson peak of the fully hydrated protein. A decrease of each volume means the increase of rigidity, which is the origin of the boson peak shift. The boson peak profile can be predicted by the total cavity volume. This prediction is effective for the evaluation of the net quasielastic scattering of incoherent neutron scattering spectra when the boson peak cannot be distinguished experimentally because of a strong contribution from quasielastic scattering.

Journal Articles

Development of next-generation LLRF control system for J-PARC rapid cycling synchrotron

Tamura, Fumihiko; Sugiyama, Yasuyuki*; Yoshii, Masahito*; Ryoshi, Masatsugu*

IEEE Transactions on Nuclear Science, 66(7), p.1242 - 1248, 2019/07

The LLRF control system for the rapid cycling synchrotron of the J-PARC started its operation in 2007. The key functions of the LLRF control system are the dual harmonic auto voltage control and the multiharmonic rf feedforward to compensate the beam loading in the MA cavity caused by high intensity beams. The system has been working well without major problems for more than ten years. However, the old FPGAs are discontinued and not supported by the current development environment. It will be difficult to maintain the system in near future. Thus, we are planning to replace the existing VME-based LLRF control system with a new MicroTCA.4 based system. In this presentation, we present the configuration of the system under development, the implemented functions, and preliminary test results.

Journal Articles

Proton chelating ligands drive improved chemical separations for rhodium

Narita, Hirokazu*; Nicolson, R. M.*; Motokawa, Ryuhei; Ito, Fumiyuki*; Morisaku, Kazuko*; Goto, Midori*; Tanaka, Mikiya*; Heller, W. T.*; Shiwaku, Hideaki; Yaita, Tsuyoshi; et al.

Inorganic Chemistry, 58(13), p.8720 - 8734, 2019/07

18521 (Records 1-20 displayed on this page)