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JAEA Reports

Improvement of load control unit in material irradiation test system (Contract research)

Okada, Yuji; Magome, Hirokatsu; Matsui, Yoshinori

JAEA-Technology 2022-014, 113 Pages, 2022/09


Material irradiation test system had been newly installed in JMTR (Japan Materials Testing Reactor) with taking 5 years which was from 2008 through 2013. The aim of material irradiation test system is to conduct IASCC (Irradiation Assisted Stress Corrosion Cracking) evaluation study. This system is mainly consist of water control unit, which can simulate elevated temperature and pressure of the light water reactor environment in the reactor, and load control unit, which can perform the crack propagation examination under irradiation. This load control unit gives a load to CT (Compact Tension) specimen, and perform the crack propagation examination. The principle of loading to CT specimen is using pressure difference between pressure generated by high temperature and high pressure water by water control unit in capsule and pressure generated by load gas pressure supplied by helium gas cylinder in bellows installed in load control unit. In 2013, the commissioning of material irradiation test system was carried out for adjustment. During this commissioning, the correlation between the differential pressure in load control unit and the load was confirmed by using the test container connected to load control unit with load cell. From the results of commissioning, the problem, which the load change speeds at loading and unloading were different due to different pressure change speeds by the piping resistance performance in the periodic loading test in which load from minimum to maximum repeatedly applied, was confirmed. This report summarizes the problem of load change speed due to the piping resistance performance, which was confirmed in 2013, the improvement and performance test of load control unit for solving the problem described above, which were carried out from 2014 to 2015, and operating procedure.

Journal Articles

Effect of hydrogen on evolution of deformation microstructure in low-carbon steel with ferrite microstructure

Okada, Kazuho*; Shibata, Akinobu*; Gong, W.; Tsuji, Nobuhiro*

Acta Materialia, 225, p.117549_1 - 117549_13, 2022/02

 Times Cited Count:10 Percentile:95.2(Materials Science, Multidisciplinary)

Journal Articles

Catalog of gamma-ray glows during four winter seasons in Japan

Wada, Yuki*; Matsumoto, Takahiro*; Enoto, Teruaki*; Nakazawa, Kazuhiro*; Yuasa, Takayuki*; Furuta, Yoshihiro*; Yonetoku, Daisuke*; Sawano, Tatsuya*; Okada, Go*; Nanto, Hidehito*; et al.

Physical Review Research (Internet), 3(4), p.043117_1 - 043117_31, 2021/12

Journal Articles

Revisit of XPS studies of supersonic O$$_{2}$$ molecular adsorption on Cu(111); Copper oxides

Hayashida, Koki*; Tsuda, Yasutaka; Yamada, Takashi*; Yoshigoe, Akitaka; Okada, Michio*

ACS Omega (Internet), 6(40), p.26814 - 26820, 2021/10

 Times Cited Count:3 Percentile:31.05(Chemistry, Multidisciplinary)

We report the X-ray photoemission spectroscopy (XPS) characterization of the bulk Cu$$_{2}$$O(111) surface and 8-type and 29-type oxide structures on Cu(111) prepared by using 0.5 eV O$$_{2}$$ supersonic molecular beam (SSMB) source. We propose a new structural model for the 8-type oxide structure and also confirmed the previously proposed model for the [29] oxide structure on Cu(111), based on the O1s XPS spectra. The detection-angle dependence of the O 1s spectra supports that the nanopyramidal model is more preferable for the ($$sqrt{3}$$X$$sqrt{3}$$)R30$$^{circ}$$ Cu$$_{2}$$O(111). We also report the electronic excitations which O1s electrons suffer.

Journal Articles

Design for detecting recycling muon after muon-catalyzed fusion reaction in solid hydrogen isotope target

Okutsu, Kenichi*; Yamashita, Takuma*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.

Fusion Engineering and Design, 170, p.112712_1 - 112712_4, 2021/09

 Times Cited Count:3 Percentile:56.29(Nuclear Science & Technology)

A muonic molecule which consists of two hydrogen isotope nuclei (deuteron (d) or tritium (t)) and a muon decays immediately via nuclear fusion and the muon will be released as a recycling muon, and start to find another hydrogen isotope nucleus. The reaction cycle continues until the muon ends up its lifetime of 2.2 $$mu$$s. Since the muon does not participate in the nuclear reaction, the reaction is so called a muon catalyzed fusion ($$mu$$CF). The recycling muon has a particular kinetic energy (KE) of the muon molecular orbital when the nuclear reaction occurs. Since the KE is based on the unified atom limit where distance between two nuclei is zero. A precise few-body calculation estimating KE distribution (KED) is also in progress, which could be compared with the experimental results. In the present work, we observed recycling muons after $$mu$$CF reaction.

Journal Articles

Time evolution calculation of muon catalysed fusion; Emission of recycling muons from a two-layer hydrogen film

Yamashita, Takuma*; Okutsu, Kenichi*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.

Fusion Engineering and Design, 169, p.112580_1 - 112580_5, 2021/08

 Times Cited Count:3 Percentile:56.29(Nuclear Science & Technology)

A muon ($$mu$$) having 207 times larger mass of electron and the same charge as the electron has been known to catalyze a nuclear fusion between deuteron (d) and triton (t). These two nuclei are bound by $$mu$$ and form a muonic hydrogen molecular ion, dt$$mu$$. Due to the short inter-nuclear distance of dt$$mu$$, the nuclear fusion, d +t$$rightarrow alpha$$ + n + 17.6 MeV, occurs inside the molecule. This reaction is called muon catalyzed fusion ($$mu$$CF). Recently, the interest on $$mu$$CF is renewed from the viewpoint of applications, such as a source of high-resolution muon beam and mono-energetic neutron beam. In this work, we report a time evolution calculation of $$mu$$CF in a two-layered hydrogen isotope target.

Journal Articles

Benchmark analysis by Beremin model and GTN model in CAF subcommittee

Hirota, Takatoshi*; Nagoshi, Yasuto*; Hojo, Kiminobu*; Okada, Hiroshi*; Takahashi, Akiyuki*; Katsuyama, Jinya; Ueda, Takashi*; Ogawa, Takuya*; Yashirodai, Kenji*; Ohata, Mitsuru*; et al.

Proceedings of ASME 2021 Pressure Vessels and Piping Conference (PVP 2021) (Internet), 9 Pages, 2021/07

Journal Articles

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

 Times Cited Count:30 Percentile:96.52(Astronomy & Astrophysics)

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 $$^{circ}$$C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 $$^{circ}$$C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

Journal Articles

Interface atom mobility and charge transfer effects on CuO and Cu$$_{2}$$O formation on Cu$$_{3}$$Pd(111) and Cu$$_{3}$$Pt(111)

Tsuda, Yasutaka; Gueriba, J. S.*; Makino, Takamasa*; Di$~n$o, W. A.*; Yoshigoe, Akitaka; Okada, Michio*

Scientific Reports (Internet), 11, p.3906_1 - 3906_8, 2021/02

 Times Cited Count:2 Percentile:14.22(Multidisciplinary Sciences)

Journal Articles

Development and operation of an electrostatic time-of-flight detector for the Rare RI storage Ring

Nagae, Daisuke*; Abe, Yasushi*; Okada, Shunsuke*; Omika, Shuichiro*; Wakayama, Kiyoshi*; Hosoi, Shun*; Suzuki, Shinji*; Moriguchi, Tetsuro*; Amano, Masamichi*; Kamioka, Daiki*; et al.

Nuclear Instruments and Methods in Physics Research A, 986, p.164713_1 - 164713_7, 2021/01

 Times Cited Count:5 Percentile:74.78(Instruments & Instrumentation)

Journal Articles

Real-time ${{it in vivo}}$ dosimetry system based on an optical fiber-coupled microsized photostimulable phosphor for stereotactic body radiation therapy

Yada, Ryuichi*; Maenaka, Kazusuke*; Miyamoto, Shuji*; Okada, Go*; Sasakura, Aki*; Ashida, Motoi*; Adachi, Masashi*; Sato, Tatsuhiko; Wang, T.*; Akasaka, Hiroaki*; et al.

Medical Physics, 47(10), p.5235 - 5249, 2020/10

 Times Cited Count:7 Percentile:52.93(Radiology, Nuclear Medicine & Medical Imaging)

The ${{it in vivo}}$ dosimeter system is capable of real-time, accurate, and precise measurement under stereotactic body radiation therapy (SBRT) conditions. The probe is smaller than a conventional dosimeter, has excellent spatial resolution, and can be valuable in SBRT with a steep dose distribution over a small field. The developed PSP dosimeter system appears to be suitable for in vivo SBRT dosimetry.

Journal Articles

The Surface composition of asteroid 162173 Ryugu from Hayabusa2 near-infrared spectroscopy

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Arai, Takehiko*; Nakauchi, Yusuke*; Nakamura, Tomoki*; Matsuoka, Moe*; et al.

Science, 364(6437), p.272 - 275, 2019/04

 Times Cited Count:233 Percentile:99.74(Multidisciplinary Sciences)

The near-Earth asteroid 162173 Ryugu, the target of Hayabusa2 sample return mission, is believed to be a primitive carbonaceous object. The Near Infrared Spectrometer (NIRS3) on Hayabusa2 acquired reflectance spectra of Ryugu's surface to provide direct measurements of the surface composition and geological context for the returned samples. A weak, narrow absorption feature centered at 2.72 micron was detected across the entire observed surface, indicating that hydroxyl (OH)-bearing minerals are ubiquitous there. The intensity of the OH feature and low albedo are similar to thermally- and/or shock-metamorphosed carbonaceous chondrite meteorites. There are few variations in the OH-band position, consistent with Ryugu being a compositionally homogeneous rubble-pile object generated from impact fragments of an undifferentiated aqueously altered parent body.

Journal Articles

Magnetization dynamics and its scattering mechanism in thin CoFeB films with interfacial anisotropy

Okada, Atsushi*; He, S.*; Gu, B.; Kanai, Shun*; Soumyanarayanan, A.*; Lim, S. T.*; Tran, M.*; Mori, Michiyasu; Maekawa, Sadamichi; Matsukura, Fumihiro*; et al.

Proceedings of the National Academy of Sciences of the United States of America, 144(15), p.3815 - 3820, 2017/04

Journal Articles

Oxidation processes of copper-gold alloy surface induced by supersonic oxygen molecular beam

Okada, Michio*; Tsuda, Yasutaka*; Yoshigoe, Akitaka; Di$~n$o, W. A.*

Do To Dogokin, 56(1), p.232 - 236, 2017/00

We reported the our studies on the surface temperature (Ts) dependence of oxidation on the Cu$$_{3}$$Au(111) surface by a supersonic O$$_{2}$$ molecular beam, using synchrotron radiation X-ray photoemission spectroscopy. Clean surface shows strong Au segregation to the top layer, i.e., Au surface enrichment of the clean surface. Complete Cu segregation to the surface occurs at 0.5 ML O surface coverage. The Au-rich second and third layers of the oxidized surface demonstrate the protective layer formation against oxidation deeper into the bulk. We found that Cu$$_{2}$$O formation occurs. At Ts = 300K, the Cu$$_{2}$$O growth is not so effective. The surface oxidation is less effective on Cu$$_{3}$$Au(111) than on Cu(111). At Ts = 400K, the protection by the Au-rich layer against oxidation into bulk is effective. At Ts = 500K, the Au protective layer is broken due to effective Au diffusion and thus Cu$$_{2}$$O grows deeper into bulk.

Journal Articles

Experimental and theoretical studies on oxidation of Cu-Au alloy surfaces; Effect of bulk Au concentration

Okada, Michio*; Tsuda, Yasutaka*; Oka, Kohei*; Kojima, Kazuki*; Di$~n$o, W. A.*; Yoshigoe, Akitaka; Kasai, Hideaki*

Scientific Reports (Internet), 6, p.31101_1 - 31101_8, 2016/08

 Times Cited Count:24 Percentile:71.36(Multidisciplinary Sciences)

We report results of our experimental and theoretical studies on the oxidation of Cu-Au alloy surfaces, viz., Cu$$_{3}$$Au(111), CuAu(111), and Au$$_{3}$$Cu(111), using hyperthermal O$$_{2}$$ molecular beam (HOMB). We observed strong Au segregation to the top layer of the corresponding clean (111) surfaces. This forms a protective layer that hinders further oxidation into the bulk. The higher the concentration of Au in the protective layer formed, the higher the protective efficacy. As a result, of the three Cu-Au surfaces studied, Au$$_{3}$$Cu(111) is the most stable against dissociative adsorption of O$$_{2}$$, even with HOMB. We also found that this protective property breaks down for oxidations occurring at temperatures above 300 K.

Journal Articles

Surface temperature dependence of oxidation of Cu$$_{3}$$Au(111) by an energetic oxygen molecule

Tsuda, Yasutaka*; Yoshigoe, Akitaka; Teraoka, Yuden; Okada, Michio*

Materials Research Express (Internet), 3(3), p.035014_1 - 035014_8, 2016/03

 Times Cited Count:5 Percentile:19.79(Materials Science, Multidisciplinary)

We report a study on the surface-temperature ($$T_{s}$$) dependence of oxidation process at Cu$$_{3}$$Au(111) by using a hyperthermal oxygen molecular beam and synchrotron-radiation X-ray photoemission spectroscopy. The O-1s spectra and the corresponding O-uptake curves demonstrate that Cu$$_{2}$$O domains grow effectively at high $$T_{s}$$ of 400 and 500 K. The simple analysis of the O distribution suggests that the temperature-induced atomic diffusion causes the Cu$$_{2}$$O domains growing thicker at 500 K. The oxidation of Cu$$_{3}$$Au(111) is less efficient at $$T_{s}$$ = 300-500 K than that of Cu(111), demonstrating that the protective nature of Cu$$_{3}$$Au against oxidation, in comparison to Cu, remains even at high $$T_{s}$$.

JAEA Reports

Performance confirmation operation of water environment control facility

Magome, Hirokatsu; Okada, Yuji; Tomita, Kenji; Iida, Kazuhiro; Ando, Hitoshi; Yonekawa, Akihisa; Ueda, Haruyasu; Hanawa, Hiroshi; Kanno, Masaru; Sakuta, Yoshiyuki

JAEA-Technology 2015-025, 100 Pages, 2015/09


In Japan Atomic Energy Agency, in order to solve the problem in the long-term operation of a light water reactor, preparation which does the irradiation experiment of light-water reactor fuel and material was advanced. JMTR stopped after the 165th operation cycle in August 2006, and is advancing renewal of the irradiation facility towards re-operation. The material irradiation test facility was installed from 2008 fiscal year to 2012 fiscal year in JMTR. The material irradiation test facility is used for IASCC study, and that consists of mainly three equipments. This report is described performance operating test of the water environmental control facilities for IASCC study carried out 2013 fiscal year.

Journal Articles

In situ synchrotron radiation photoemission study of ultrathin surface oxides of Ge(111)-c(2$$times$$8) induced by supersonic O$$_{2}$$ beams

Okada, Ryuta; Yoshigoe, Akitaka; Teraoka, Yuden; Yamada, Yoichi*; Sasaki, Masahiro*

Applied Physics Express, 8(2), p.025701_1 - 025701_4, 2015/02

 Times Cited Count:7 Percentile:32.08(Physics, Applied)

We studied the surface oxidation on a Ge(111)-c(2$$times$$8) surface at room temperature using supersonic oxygen beams as a function of the translational energy of the incident oxygen molecules ranging from 26 meV to 2.3 eV. In situ synchrotron photoemission spectroscopy performed during the oxidation revealed that the surface oxidation terminated with the formation of a sub-monolayer oxide of at most 0.52 ML, for all the beam energies examined. In addition, the oxidation state of the surface oxides was found to depend on the translational energy. These results demonstrate the precise chemical control of the ultrathin surface oxides of Ge(111)-c(2$$times$$8).

Journal Articles

High order harmonics from relativistic electron spikes

Pirozhkov, A. S.; Kando, Masaki; Esirkepov, T. Z.; Faenov, A. Y.*; Pikuz, T. A.*; Kawachi, Tetsuya; Sagisaka, Akito; Koga, J. K.; Mori, Michiaki; Kawase, Keigo*; et al.

RAL-TR-2015-025, P. 22, 2015/00

Journal Articles

${{it In situ}}$ synchrotron radiation photoelectron spectroscopy study of the oxidation of the Ge(100)-2$$times$$1 surface by supersonic molecular oxygen beams

Yoshigoe, Akitaka; Teraoka, Yuden; Okada, Ryuta; Yamada, Yoichi*; Sasaki, Masahiro*

Journal of Chemical Physics, 141(17), p.174708_1 - 174708_7, 2014/11

 Times Cited Count:8 Percentile:30.87(Chemistry, Physical)

${{it In situ}}$ synchrotron radiation photoelectron spectroscopy was performed during the oxidation of the Ge(100)-2$$times$$1 surface induced by a molecular oxygen beam with various incident energies up to 2.2 eV from the initial to saturation coverage of surface oxides. The saturation coverage of oxygen on the clean Ge(100) surface was much lower than one monolayer and the oxidation state of Ge was +2 at most. This indicates that the Ge(100) surface is in strong contrast to Si surfaces. The direct adsorption process can be activated by increasing the translational energy, resulting in an increased population of Ge$$^{2+}$$ and a higher final oxygen coverage. Our findings will contribute to the fundamental understanding of oxygen adsorption processes at 300 K from the initial stages to saturated oxidation.

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