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Journal Articles

Design and actual performance of J-PARC 3 GeV rapid cycling synchrotron for high-intensity operation

Yamamoto, Kazami; Kinsho, Michikazu; Hayashi, Naoki; Saha, P. K.; Tamura, Fumihiko; Yamamoto, Masanobu; Tani, Norio; Takayanagi, Tomohiro; Kamiya, Junichiro; Shobuda, Yoshihiro; et al.

Journal of Nuclear Science and Technology, 59(9), p.1174 - 1205, 2022/09

 Times Cited Count:1 Percentile:58.67(Nuclear Science & Technology)

In the Japan Proton Accelerator Research Complex, the purpose of the 3 GeV rapid cycling synchrotron (RCS) is to accelerate a 1 MW, high-intensity proton beam. To achieve beam operation at a repetition rate of 25 Hz at high intensities, the RCS was elaborately designed. After starting the RCS operation, we carefully verified the validity of its design and made certain improvements to establish a reliable operation at higher power as possible. Consequently, we demonstrated beam operation at a high power, namely, 1 MW. We then summarized the design, actual performance, and improvements of the RCS to achieve a 1 MW beam.

JAEA Reports

Manufacture of substitutive assemblies for MONJU reactor decommissioning

Sakakibara, Hiroshi; Aoki, Nobuhiro; Muto, Masahiro; Otabe, Jun; Takahashi, Kenji*; Fujita, Naoyuki*; Hiyama, Kazuhiko*; Suzuki, Hirokazu*; Kamogawa, Toshiyuki*; Yokosuka, Toru*; et al.

JAEA-Technology 2020-020, 73 Pages, 2021/03


The decommissioning is currently in progress at the prototype fast breeder reactor Monju. Fuel assemblies will be taken out of its core for the first step of the great task. Fuel assemblies stand on their own spike plugged into a socket on the core support plate and support with adjacent assemblies through their housing pads each other, resulting in steady core structure. For this reason, some substitutive assemblies are necessary for the purpose of discharging the fuel assemblies of the core. Monju side commissioned, therefore, Plutonium Fuel Development Center to manufacture the substitutive assemblies and the Center accepted it. This report gives descriptions of design, manufacture, and shipment in regard to the substitutive assemblies.

Journal Articles

Materials and Life Science Experimental Facility at the Japan Proton Accelerator Research Complex, 3; Neutron devices and computational and sample environments

Sakasai, Kaoru; Sato, Setsuo*; Seya, Tomohiro*; Nakamura, Tatsuya; To, Kentaro; Yamagishi, Hideshi*; Soyama, Kazuhiko; Yamazaki, Dai; Maruyama, Ryuji; Oku, Takayuki; et al.

Quantum Beam Science (Internet), 1(2), p.10_1 - 10_35, 2017/09

Neutron devices such as neutron detectors, optical devices including supermirror devices and $$^{3}$$He neutron spin filters, and choppers are successfully developed and installed at the Materials Life Science Facility (MLF) of the Japan Proton Accelerator Research Complex (J-PARC), Tokai, Japan. Four software components of MLF computational environment, instrument control, data acquisition, data analysis, and a database, have been developed and equipped at MLF. MLF also provides a wide variety of sample environment options including high and low temperatures, high magnetic fields, and high pressures. This paper describes the current status of neutron devices, computational and sample environments at MLF.

Journal Articles

Experiments of coolant accumulation in SG U tube and analytical model development

Yamaji, Tatsuya*; Koizumi, Yasuo; Yamazaki, Kohei*; Otake, Hiroyasu*; Hasegawa, Koji*; Onuki, Akira*; Kanamori, Daisuke*

Konsoryu Shimpojiumu 2015 Koen Rombunshu (USB Flash Drive), 2 Pages, 2015/08

Experiments of condensing counter-current two-phase flow in a vertical pipe were performed. This study was intended to examine water accumulation in the up-flow side of steam generator U-tubes of a PWR during the reflux cooling stage of a small break LOCA. It has been apprehended that the water accumulation may result in temporary core liquid level depression. The inner diameter and the length of a test flow channel used in the experiments were 18 mm and 4 m, respectively. The experiments were performed by using steam and water at 0.1 MPa. Two kinds of experiments were conducted; visualization experiments by using a transparent test section and quantitative water accumulation evaluation experiments by using a brass test section. Even if water on the inner surface of the test pipe could not flow downward at the lower portion of the test pipe, a part of water became to flow downward at the upper portion of the test pipe since steam velocity decreased because of condensation. Thus, two-phase mixture level was formed in the upper portion of the test pipe, which resulted in the water accumulation in the pipe. The model to predict the water accumulation was proposed. It predicted the water accumulation reasonably well.

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

Direct stress measurement of Si(111) 7$$times$$7 reconstruction

Asaoka, Hidehito; Yamazaki, Tatsuya; Yokoyama, Yuta; Yamaguchi, Kenji

Journal of Crystal Growth, 378, p.37 - 40, 2013/09

 Times Cited Count:3 Percentile:32.85(Crystallography)

We have focused on stress measurements of the reconstructed Si(111) 7$$times$$7 and the H-terminated Si(111) 1$$times$$1 surfaces. In order to obtain information on both the surface stress and the surface structure simultaneously, we have combined the surface-curvature and the reflection-high-electron-energy-diffraction instrumentations in an identical ultrahigh vacuum system. At the beginning of Ge wetting layer growth on H-terminated Si(111), the stress gradient drastically changes accompanied by change in the surface structure resulting from the H desorption. Comparison of the surface stress behaviors between Ge wetting layer growth on the H-terminated Si(111) 1$$times$$1 and the Si(111) 7$$times$$7 surfaces reveals that the Si(111) 1$$times$$1 surface releases 1.6 N/m (=J/m$$^{2}$$), or (1.3 eV/(1$$times$$1 unit cell)), of the surface energy from the strong tensile Si(111) 7$$times$$7 reconstruction.

Journal Articles

Change of Si(110) reconstructed structure by Ge nanocluster formation

Yokoyama, Yuta; Yamazaki, Tatsuya; Asaoka, Hidehito

Journal of Crystal Growth, 378, p.230 - 232, 2013/09

 Times Cited Count:2 Percentile:24.24(Crystallography)

The initial processes of Ge nano cluster formation on Si(110)-16$$times$$2 reconstructed structure were investigated via scanning tunneling microscopy. For a small amount of Ge deposited on Si(110)-16$$times$$2 single-domain structure at room temperature, the surface structure did not change significantly. After direct current heating at 973 K for 20 min, the striped structure almost broken and disordered-like structure was formed on the terrace. With increasing the annealing time, the surface structure changed from disordered-like structure to the 16$$times$$2 double-domain structure and pyramidal nano clusters were formed at the domain boundary. These results suggest that the surface stress was induced by Ge nano cluster formation and the double-domain structure was formed in order to relax the stress.

Journal Articles

HBC foil beam study and long-term observation at the 3-GeV RCS in J-PARC

Yoshimoto, Masahiro; Saha, P. K.; Yamazaki, Yoshio; Kawase, Masato; Saeki, Riuji; Hayashi, Naoki; Yamamoto, Kazami; Hotchi, Hideaki; Ishiyama, Tatsuya; Kinsho, Michikazu; et al.

Journal of Physics; Conference Series, 417, p.012073_1 - 012073_6, 2013/03

 Times Cited Count:4 Percentile:76.89

The HBC foil are installed in the J-PARC RCS for the charge-exchange H$$^{-}$$ beam injection. In order to examine the characteristics of the HBC foils, beam studies for the HBC foil were carried out from the viewpoint of foil's life time and the beam survival rate due to foils. According to the compromise between charge-exchange efficiency and foil scattering beam loss, we optimized the foils thickness for user operation. The long-term observation during the user operation as well as the HBC foil endurance test for its life time evaluation was carried out. Even after one year was operation, there was no deterioration of the stripping foil.

Journal Articles

Direct measurement of surface stress during Bi-mediated Ge growth on Si

Asaoka, Hidehito; Yamazaki, Tatsuya*; Yamaguchi, Kenji; Shamoto, Shinichi; Filimonov, S.*; Suemitsu, Maki*

Surface Science, 609, p.157 - 160, 2013/03

 Times Cited Count:1 Percentile:5.19(Chemistry, Physical)

We have focused on stress measurements during Bi termination of Si(111) and Ge growth on this Bi-mediated Si(111). In order to obtain information on both the surface stress and the surface structure simultaneously, we have combined the surface-curvature and the reflection-high-electron-energy-diffraction instrumentations in an identical ultrahigh vacuum system. We find the Bi-terminated Si(111) $$sqrt{3}$$$$times$$$$sqrt{3}$$-$$beta$$ surface releases 1.8 N/m (=J/m$$^{2}$$), or (1.4 eV/(1$$times$$1 unit cell)), of the surface energy from the strong tensile Si(111) 7$$times$$7 reconstruction. Subsequent Ge deposition on the Bi-terminated Si surface develops a compressive stress, which oscillates with a period corresponding to the growth of a single bilayer. The real-time stress measurement provides a direct evidence for this oscillatory stress relaxation in the layer-by-layer growth.

Journal Articles

Current status of a new polarized neutron reflectometer at the intense pulsed neutron source of the Materials and Life Science Experimental Facility (MLF) of J-PARC

Takeda, Masayasu; Yamazaki, Dai; Soyama, Kazuhiko; Maruyama, Ryuji; Hayashida, Hirotoshi; Asaoka, Hidehito; Yamazaki, Tatsuya; Kubota, Masato; Aizawa, Kazuya; Arai, Masatoshi; et al.

Chinese Journal of Physics, 50(2), p.161 - 170, 2012/04

Journal Articles

Analysis of buried heterointerfacial hydrogen in highly lattice-mismatched epitaxy on silicon

Yamazaki, Tatsuya; Asaoka, Hidehito; Taguchi, Tomitsugu; Yamamoto, Shunya; Yamazaki, Dai; Maruyama, Ryuji; Takeda, Masayasu; Shamoto, Shinichi

Thin Solid Films, 520(8), p.3300 - 3303, 2012/02

 Times Cited Count:2 Percentile:10.41(Materials Science, Multidisciplinary)

We succeeded in realizing the epitaxial growth of a Sr layer on Si(111) with an atomically abrupt heterointerface - in spite of its large lattice mismatch (12%) with Si - by introducing a monoatomic layer of H on Si. In order to identify the buried H, we carried out a combination analysis involving neutron reflectometry and resonant nuclear reaction of $$^{1}$$H($$^{15}$$N,$$alpha$$$$gamma$$)$$^{12}$$C analysis. We found different neutron reflectivity profiles resulting from a contrast variation between the H and D atoms at the buried heterointerface. Furthermore, the depth $$gamma$$-ray intensity profiles revealed that the H at the heterointerface acts as an effective buffer layer that enables it to manage the highly mismatched epitaxy on Si.

JAEA Reports

Conceptual design of multipurpose compact research reactor; Annual report FY2010 (Joint research)

Imaizumi, Tomomi; Miyauchi, Masaru; Ito, Masayasu; Watahiki, Shunsuke; Nagata, Hiroshi; Hanakawa, Hiroki; Naka, Michihiro; Kawamata, Kazuo; Yamaura, Takayuki; Ide, Hiroshi; et al.

JAEA-Technology 2011-031, 123 Pages, 2012/01


The number of research reactors in the world is decreasing because of their aging. However, the planning to introduce the nuclear power plants is increasing in Asian countries. In these Asian countries, the key issue is the human resource development for operation and management of nuclear power plants after constructed them, and also the necessity of research reactor, which is used for lifetime extension of LWRs, progress of the science and technology, expansion of industry use, human resources training and so on, is increasing. From above backgrounds, the Neutron Irradiation and Testing Reactor Center began to discuss basic concept of a multipurpose low-power research reactor for education and training, etc. This design study is expected to contribute not only to design tool improvement and human resources development in the Neutron Irradiation and Testing Reactor Center but also to maintain and upgrade the technology on research reactors in nuclear power-related companies. This report treats the activities of the working group from July 2010 to June 2011 on the multipurpose low-power research reactor in the Neutron Irradiation and Testing Reactor Center and nuclear power-related companies.

Journal Articles

Neutron reflectometry of buried monatomic hydrogen layer at the hetero-interface in a highly mismatched Sr and H-terminated Si(111)

Yamazaki, Tatsuya; Yamazaki, Dai; Asaoka, Hidehito; Taguchi, Tomitsugu; Shamoto, Shinichi; Toyoshima, Yasutake*

Hyomen Kagaku, 31(8), p.380 - 385, 2010/08

Strontium (Sr) is a well-known template on Si for a highly-desirable transistor gate material SrTiO$$_{3}$$. Sr layers are grown epitaxially on hydrogen-terminated Si(111) surface despite the large lattice mismatch of 12%. However, there are still many unclear points concerning the specific interface structure. We need to study how the buried monatomic hydrogen layer behaves to manage the large mismatch. In order to clarify its buried hetero-interface structure related to monatomic hydrogen layer, Si-H bonding states are in situ monitored during Sr growth by Multiple Internal Reflection Fourier Transform Infrared (MIR-FTIR) spectroscopy, and the buried hetero-interface between Sr layer and Si(111) surface is investigated by ex situ neutron reflectometry (NR). FTIR has shown change of Si-H bonding states caused by the Sr growth at the initial monolayer growth stage. Furthermore, we have found the difference in neutron reflectivity profiles between the Sr layers grown on H- and D-terminated Si substrates. These results suggest the existence of buried monatomic hydrogen layer at the hetero-interface acting as an effective component of interface structure to manage the high lattice mismatch.

Journal Articles

Beam study results with HBC stripping foils at the 3-GeV RCS in J-PARC

Yoshimoto, Masahiro; Yamazaki, Yoshio; Hayashi, Naoki; Yamamoto, Kazami; Saeki, Riuji; Hotchi, Hideaki; Saha, P. K.; Harada, Hiroyuki; Kawase, Masato; Ishiyama, Tatsuya; et al.

Proceedings of 1st International Particle Accelerator Conference (IPAC '10) (Internet), p.3927 - 3929, 2010/05

The ($underline{H}$)ybrid type thick ($underline{B}$)oron-doped ($underline{C}$)arbon (HBC) stripping foils are installed and used for the beam injection at the 3GeV RCS (Rapid Cycling Synchrotron) in J-PARC (Japan Proton Accelerator Research Complex). Up to now, the performance deterioration of the stripping foils can not be seen after the long beam irradiation for the 120kW user operation and 300kW high power beam demonstration at the RCS. In order to examine the characteristic of the HBC foils, various beam studies were carried out. The beam-irradiated spot at the foil was measured by scanning the foil setting position, the charge exchange efficiency was evaluated with various thickness foils, and the effect of the SiC fibers supporting the foil mounting was checked with different mounting foils. Beam study results obtained with using the HBC foils will be presented. In addition, the trends of outgas from the stripping foils and the deformations of the foils during the beam irradiation will be reported.

Journal Articles

Initial oxidation of Si(110) surface evaluated by photoemission spectroscopy and substrate-curvature measurements

Yamamoto, Yoshihisa*; Suzuki, Yasushi*; Miyamoto, Yu*; Bantaculo, R.*; Suemitsu, Maki*; Enta, Yoshiharu*; Teraoka, Yuden; Yoshigoe, Akitaka; Asaoka, Hidehito; Yamazaki, Tatsuya

Hakumaku, Hyomen Butsuri Bunkakai, Shirikon Tekunoroji Bunkakai Kyosai Tokubetsu Kenkyukai Kenkyu Hokoku, p.207 - 210, 2009/01

The bending of Si substrate has been measured optically in the oxidation of Si(110) surface and variation of curvature for (001) and (-110) directions have been evaluated. Furthermore, time evolutions of oxygen adsorption content and its chemical bonding states have been measured by photoemission spectroscopy to discuss inisotropy of the Si(110) oxidation in comjunction with substrate curvature measurements. Oxygen adsorption content was evaluated from O1s photoemission and chemical bonding states were evaluated from Si2p photoemission. O$$_{2}$$ gas pressure was ranging from 5.0$$times$$10$$^{-6}$$ Pa to 6.7$$times$$10$$^{-6}$$ and substrate temperature was 873 K. Compressive stress was detected in the (-110) direction. In turn, stretching stress was detected. The photoemission spectroscopy indicated that a layer-by-layer oxidation was not took place. The stretching stress in the (001) direction implies that oxidation of B-bonds which have components along the (001) direction takes place.

Journal Articles

Direct determination of surface stress during Bi-mediated Ge growth on Si

Asaoka, Hidehito; Yamazaki, Tatsuya; Filimonov, S.*; Shamoto, Shinichi

Proceedings of 14th International Conference on Thin Films (ICTF-14) & Reactive Sputter Deposition 2008 (RSD 2008), p.179 - 182, 2008/11

We report stress evolutions during Bi adsorption on Si(111) 7$$times$$7 and initial stages of Bi-mediated Ge growth on Si(111). Surface stress is determined by using a real-time measurement of the substrate curvature. We find a difference in the surface stress between clean Si(111) 7$$times$$7 surface and Si(111) $$sqrt{3}$$$$times$$$$sqrt{3}$$ surface covered with one monolayer of Bi, and an increase in the surface stress accompanied by RHEED intensity oscillation of the specular beam during ideal pseudomorphic Ge layer growth with Bi. For Ge coverage of up to 2 bilayers, the stress evolution shows a clear stress relaxation due to formation of trenches on the Ge surface and injection of misfit dislocations into the Ge/Si interface.

Journal Articles

Buried H monolayer at hetero-interface between highly mismatched Sr films and Si substrates

Yamazaki, Tatsuya; Asaoka, Hidehito; Takeda, Masayasu; Yamazaki, Dai; Taguchi, Tomitsugu; Torikai, Naoya*; Toyoshima, Yasutake*; Shamoto, Shinichi

Transactions of the Materials Research Society of Japan, 33(3), p.611 - 614, 2008/09

Strontium and SrO are well-known templates on Si for SrTiO$$_{3}$$, highly-desirable transistor gate material. When stacked on Si, Srlayer becomes amorphous due to its large lattice mismatch of 12%. By introducing a monatomic hydrogen layer on Si, we succeeded in making the Sr (and subsequent SrO) layer(s) grow epitaxially with atomically abrupt interface. However, it is some what mysterious how the monatomic hydrogen layer behaves to manage this large mismatch. In order to identify its behavior, we have employed compound analysis by neutron reflectometer as well as multiple-internal-reflection fourier-transform infrared spectroscopy (MIR-FTIR) to investigate the buried heterointerface of Sr grown on Si(111)1$$times$$1: monohydride. We have found difference between the H- and D-terminated substrates in the reflectivity profiles, and changes in Si-H bonding features with the Sr growth (mainly at the initial monolayer stage) in the FTIR spectra. From these, existence of buried H layer at the heterointerfaceis confirmed with its bonding environment.

Journal Articles

Real-time stress analysis of low-temperature Ge nanodot growth on H-terminated Si(111)-1$$times$$1 and Si(111)-7$$times$$7 surfaces

Asaoka, Hidehito; Yamazaki, Tatsuya; Shamoto, Shinichi

Current Applied Physics, 8(3-4), p.246 - 248, 2008/05

 Times Cited Count:1 Percentile:5.26(Materials Science, Multidisciplinary)

Control of intrinsic stress in heteroepitaxial films is one of the most important challenges in modern nanotechnology. We have focused on the stress evolution during the initial growth stage of Ge epitaxial films in the thickness range of a few atomic layers on Si(111)-7$$times$$7 and H-terminat ed Si(111)-1$$times$$1 surfaces. The stress/strain behavior and surface morphology were observed simultaneously by using real-time measurement of substrate curvature and reflection high energy electron diffraction (RHEED) methods. Furthermore, as confirmed by using the structural results from scanning tunnelling microscopy (STM) measurement, it provided direct information on the onset and thickness range of the nanodot growth.

Journal Articles

Magnetism on Mg$$_{1-x}$$Zn$$_x$$C$$_y$$Ni$$_3$$

Uehara, Masatomo*; Yamazaki, Takahiro*; Kori, Tatsuya*; Kashida, Takefumi*; Kimishima, Yoshihide*; Oishi, Kazuki

Journal of Physics and Chemistry of Solids, 68(11), p.2178 - 2182, 2007/11

 Times Cited Count:16 Percentile:58.33(Chemistry, Multidisciplinary)

The magnetic phase diagram for Mg$$_{1-x}$$Zn$$_x$$C$$_y$$Ni$$_3$$ has been tentatively constructed based on magnetization and muon spin relaxation ($$mu$$SR) measurements. The superconducting phase was observed to fade as $$x$$ ($$y$$) increases (decreases). The low $$y$$ samples show early stages of long-range ferromagnetism, or complete long-range ferromagnetism. In the phase diagram, the ferromagnetic phase exists in addition to the superconducting phase, suggesting that there is some correlation between superconductivity and ferromagnetism, even though the coexistence of ferromagnetism and superconductivity is not observed from the $$mu$$SR measurements down to 20 mK for the superconducting sample.

Journal Articles

Real-time stress measurement in Ge/Si(111)-7$$times$$7 heteroepitaxial growth

Asaoka, Hidehito; Yamazaki, Tatsuya; Shamoto, Shinichi; Arnoldo, A.*; Goto, Seiichi*; Suemitsu, Maki*

Hyomen Kagaku, 28(9), p.500 - 503, 2007/09

Stress evolution during initial stage of Ge nanodot formation on Si(111)-7$$times$$7 has been investigated by using simultaneous measurements of the substrate curvature and the surface morphology. In the beginning of the first bilayer growth of Ge on Si(111)-7$$times$$7, a strong compressive film stress is observed, indicating a formation of a two-dimensional wetting layer. When the layer thickness approaches the critical one for three-dimensional nanodot nucleation, a clear bend in the stress curve is observed, corresponding to a partial relaxation of the lattice planes on the surface of the nanodots. Moreover, a stress transition has been also found to exist in the very early stage of the nanodot formation, which is concurrent with the trench formation around the three-dimensional nanodots.

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