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Journal Articles

Simultaneous measurements of superradiance at multiple wavelength from helium excited states, 2; Analysis

Ohae, Chiaki*; Harries, J.; Iwayama, Hiroshi*; Kawaguchi, Kentaro*; Kuma, Susumu*; Miyamoto, Yuki*; Nagasono, Mitsuru*; Nakajima, Kyo*; Nakano, Itsuo*; Shigemasa, Eiji*; et al.

Journal of the Physical Society of Japan, 85(3), p.034301_1 - 034301_10, 2016/03

 Times Cited Count:7 Percentile:56.08(Physics, Multidisciplinary)

Journal Articles

Neutron angular distribution in ($$gamma$$, n) reactions with linearly polarized $$gamma$$-ray beam generated by laser Compton scattering

Horikawa, Ken*; Miyamoto, Shuji*; Mochizuki, Takayasu*; Amano, So*; Li, D.*; Imasaki, Kazuo*; Izawa, Yasukazu*; Ogata, Kazuyuki*; Chiba, Satoshi*; Hayakawa, Takehito

Physics Letters B, 737, p.109 - 113, 2014/10

 Times Cited Count:11 Percentile:65.49(Astronomy & Astrophysics)

It was predicted in 1950's, the neutron angular distribution in ($$gamma$$, n) reactions with a 100% linearly polarized $$gamma$$-ray beam should be anisotropic and described by a simple function of a + b sin$$^{2}$$$${theta}$$ at 90$$^{circ}$$ on the beam axis but it has not been experimentally confirmed for middle-heavy nuclides over than half a century. We have verified experimentally this angular distribution on $$^{197}$$Au, $$^{127}$$I, and natural Cu using linearly polarized laser Compton scattering $$gamma$$-rays at NewSUBARU.

Journal Articles

Aspect-ratio-dependent phase transitions and concentration fluctuations in aqueous colloidal dispersions of charged platelike particles

Yamaguchi, Daisuke; Miyamoto, Nobuyoshi*; Fujita, Takako*; Nakato, Teruyuki*; Koizumi, Satoshi; Ota, Noboru*; Yagi, Naoto*; Hashimoto, Takeji

Physical Review E, 85(1), p.011403_1 - 011403_15, 2012/01

 Times Cited Count:17 Percentile:71.93(Physics, Fluids & Plasmas)

Phase transition of aqueous colloidal dispersions of charged plate-like particles of niobate nanosheets were investigated as a function of the aspect ratio ($$r_{rm asp}$$) and particle volume concentration ($$theta$$$$_{rm P}$$) by small-angle neutron scattering and small-angle X-ray scattering. The results elucidated the following three pieces of evidence: (1) the macroscopic phase separation of the dispersions into an isotropic phase and a liquid crystalline phase (LC) under the condition of (a) varying $$r_{rm asp}$$ at a constant $$theta$$$$_{rm P}$$ = 0.01, and of (b) varying $$theta$$$$_{rm P}$$ (0.01 $$leq$$ $$theta$$$$_{rm P}$$ $$leq$$ 0.025) at a constant $$r_{rm asp}$$ = 2.5$$times$$10$$^{-3}$$. (2) the $$r_{rm asp}$$-induced phase transition of the LC phase from a nematic phase to a highly periodic layered phase upon increasing r under the condition (a). (3) the LC phase having remarkable concentration fluctuations of the particles which are totally unexpected for the conventional lyotropic molecular LC but which are anticipated to be general for the plate-like colloidal particles.

Journal Articles

Behavior of environmental tritium at NIFS Toki Site of Japan

Sugihara, Shinji*; Tanaka, Masahiro*; Tamari, Toshiya*; Shimada, Jun*; Takahashi, Tomoyuki*; Momoshima, Noriyuki*; Fukutani, Satoshi*; Atarashi-Andoh, Mariko; Sakuma, Yoichi*; Yokoyama, Sumi*; et al.

Fusion Science and Technology, 60(4), p.1300 - 1303, 2011/11

 Times Cited Count:1 Percentile:11.72(Nuclear Science & Technology)

The purpose of this study is to develop the technique to evaluate the environmental tritium behavior of the nuclear facility origin. Tritium concentrations of river water, precipitation and ground water around the NIFS site were determined by low background liquid scintillation measurement system combined with the electrolysis using solid polymer electrolyte. The electric conductivity and flow rate of the river and isotopic ratio of oxygen and hydrogen of water samples were also measured. The tritium concentrations in precipitation showed the seasonal variation and the range were 0.09-0.78 Bq/L. The tritium concentrations of river water and ground water were almost constant, 0.34 and 0.24 Bq/L respectively. The simple dynamic model for the site around the NIFS facilities was developed using measured data, and the behavior of tritium was simulated.

Journal Articles

QA/QC activities and estimation of uncertainty for ultra-trace analysis of uranium and plutonium in safeguards environmental samples

Usuda, Shigekazu*; Magara, Masaaki; Esaka, Fumitaka; Yasuda, Kenichiro; Kokubu, Yoko; Lee, C. G.; Miyamoto, Yutaka; Suzuki, Daisuke; Inagawa, Jun; Sakurai, Satoshi; et al.

Journal of Nuclear and Radiochemical Sciences, 11(2), p.A5 - A9, 2011/01

In the analysis of IAEA safeguards environmental samples, isotope ratios of ultra-trace amounts of uranium and plutonium in samples taken from nuclear facilities are determined to detect undeclared nuclear materials and activities. In order to keep and enhance the reliability of the measurement results, validation of analytical methods and estimation of measurement uncertainty in such ultra-trace analysis should be properly done in accordance with worldwide standards. In this paper, the current activities on achievement of QA/QC (quality assurance and quality control) and estimation of measurement uncertainty in the ultra-trace analysis at a clean chemistry laboratory (CLEAR) of JAEA are reported.

Journal Articles

Combined SANS, SEC, NMR, and UV-Vis studies of simultaneous living anionic copolymerization process; Simultaneous elucidation of propagating living chains at three different length scales

Zhao, Y.; Tanaka, Hirokazu*; Miyamoto, Nobuyoshi*; Koizumi, Satoshi; Hashimoto, Takeji

Macromolecules, 42(5), p.1739 - 1748, 2009/04

 Times Cited Count:13 Percentile:44.13(Polymer Science)

Journal Articles

Half-life of the $$^{164}$$Ho by the ($$gamma$$,$$n$$) reaction from Laser Compton scattering $$gamma$$ rays at the electron storage ring NewSUBARU

Hayakawa, Takehito; Shizuma, Toshiyuki; Miyamoto, Shuji*; Amano, So*; Horikawa, Ken*; Ishihara, Kazuki*; Mori, Michiaki; Kawase, Keigo; Kando, Masaki; Kikuzawa, Nobuhiro; et al.

Physical Review C, 77(6), p.068801_1 - 068801_4, 2008/06

 Times Cited Count:11 Percentile:60.8(Physics, Nuclear)

no abstracts in English

Journal Articles

Research and development on environmental radionuclides for nuclear non-proliferation at Japan Atomic Energy Agency

Usuda, Shigekazu; Shinohara, Nobuo; Sakurai, Satoshi; Magara, Masaaki; Miyamoto, Yutaka; Esaka, Fumitaka; Yasuda, Kenichiro; Kokubu, Yoko; Hirayama, Fumio; Lee, C. G.; et al.

KEK Proceedings 2007-16, p.13 - 22, 2008/02

For the purpose of controlling and monitoring radiations and radioactive materials emitted from nuclear facilities to the environment and also evaluating their effects, various R&D on environmental radioactivity has been carried out at Japan Atomic Energy Agency (JAEA). Especially, for the abolition of nuclear weapons and for peaceful uses nuclear energy, ultra-trace analysis of environmental samples for safeguards and ultra-high sensitive monitoring of radionuclides for the CTBT verification, which have been scheduled in the middle of 1990s, have been promotted under the auspices of the Japanese Government at JAERI, the former of JAEA. In this presentation, the outline of R&D on environmental radioactivity for nuclear non-proliferation is introduced. In addition, applications of the developed techniques and future perspectives will be discussed.

Journal Articles

Depositional records of plutonium and $$^{137}$$Cs released from Nagasaki atomic bomb in sediment of Nishiyama reservoir at Nagasaki

Kokubu, Yoko; Yasuda, Kenichiro; Magara, Masaaki; Miyamoto, Yutaka; Sakurai, Satoshi; Usuda, Shigekazu; Yamazaki, Hideo*; Yoshikawa, Shusaku*; Nagaoka, Shinji*; Mitamura, Muneki*; et al.

Journal of Environmental Radioactivity, 99(1), p.211 - 217, 2008/01

 Times Cited Count:15 Percentile:37.06(Environmental Sciences)

In a sediment core of Nishiyama reservoir at Nagasaki, depth profiles of $$^{240}$$Pu/$$^{239}$$Pu ratio, $$^{239+240}$$Pu and $$^{137}$$Cs concentrations were determined. Sediments containing plutonium and $$^{137}$$Cs, which were fallout deposited immediately after a detonation of Nagasaki atomic bomb, were identified in the core. Observed below the sediments were macroscopic charcoals, providing evidence for initial deposit of the fallout. This is the first entire depositional records of plutonium and $$^{137}$$Cs released from the Nagasaki atomic bomb together with those from atmospheric nuclear tests.

Journal Articles

Development of safeguards environmental sample analysis techniques at JAEA as a network laboratory of IAEA

Sakurai, Satoshi; Magara, Masaaki; Esaka, Fumitaka; Hirayama, Fumio; Lee, C. G.; Yasuda, Kenichiro; Inagawa, Jun; Suzuki, Daisuke; Iguchi, Kazunari; Kokubu, Yoko; et al.

STI/PUB/1298 (CD-ROM), p.791 - 799, 2007/08

no abstracts in English

Journal Articles

Geographical distribution of plutonium derived from the atomic bomb in the eastern area of Nagasaki

Kokubu, Yoko; Yasuda, Kenichiro; Magara, Masaaki; Miyamoto, Yutaka; Sakurai, Satoshi; Usuda, Shigekazu; Yamazaki, Hideo*; Yoshikawa, Shusaku*

Journal of Radioanalytical and Nuclear Chemistry, 273(1), p.183 - 186, 2007/07

 Times Cited Count:5 Percentile:39.35(Chemistry, Analytical)

no abstracts in English

Journal Articles

An Attempt for determining $$^{235}$$U/$$^{238}$$U ratio for a trace amount of uranium: Search for an extinct radionuclide $$^{247}$$Cm in the early solar system

Chai, J.; Miyamoto, Yutaka; Kokubu, Yoko; Magara, Masaaki; Sakurai, Satoshi; Usuda, Shigekazu; Oura, Yasuji*; Ebihara, Mitsuru*

Journal of Radioanalytical and Nuclear Chemistry, 272(2), p.397 - 401, 2007/05

 Times Cited Count:2 Percentile:19.85(Chemistry, Analytical)

$$^{247}$$Cm is an important nuclide because it has the next-shortest half-life (1.6$$cdot$$10$$^{7}$$ yr) from $$^{244}$$Pu among the transuranic nuclides. The disintegration of $$^{247}$$Cm to $$^{235}$$U by three $$alpha$$ decays and two $$beta$$ decays and the chemical fractionation between Cm and U during the formation of solid materials in early solar system lead to changes in the ratios of $$^{235}$$U to $$^{238}$$U. This variation may provide strict constraints on the time interval between the last r-process nucleosynthetic event and the formation of the solar system. It is important to develop a practical analysis protocol to determine the isotope ratio of trace uranium in geochemical and environment samples. As uranium is the least abundant element in our solar system, analytical techniques with high sensitivity and precision are required. In this study, a double focusing inductively coupled plasma mass spectory was applied to measure isotopic ratio of uranium. By one set data obtained from the EDTA phase of the Jilin meteorite sample, the upper limit of $$^{247}$$Cm in the early solar system was calculated and $$^{247}$$Cm/$$^{235}$$U $$<$$ 0.003 was obtained.

Journal Articles

Hierarchical structure of niobate nanosheets in aqueous solution

Yamaguchi, Daisuke; Miyamoto, Nobuyoshi; Koizumi, Satoshi; Nakato, Teruyuki*; Hashimoto, Takeji

Journal of Applied Crystallography, 40(s1), p.s101 - s105, 2007/04

 Times Cited Count:19 Percentile:85.33(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

Living anionic polymerization of methyl methacrylate controlled by metal-free phosphazene catalyst as observed by small-angle neutron scattering, gel-permeation chromatography and UV-visible spectroscopy

Miyamoto, Nobuyoshi; Inoue, Yoshihisa*; Koizumi, Satoshi; Hashimoto, Takeji

Journal of Applied Crystallography, 40(s1), p.s568 - s572, 2007/04

 Times Cited Count:5 Percentile:55.28(Chemistry, Multidisciplinary)

no abstracts in English

Journal Articles

Distribution of plutonium isotopes and $$^{137}$$Cs found in the surface soils of Nagasaki, Japan

Kokubu, Yoko; Yasuda, Kenichiro; Magara, Masaaki; Miyamoto, Yutaka; Sakurai, Satoshi; Usuda, Shigekazu; Yamazaki, Hideo*; Mitamura, Muneki*; Yoshikawa, Shusaku*

Journal of Geosciences, Osaka City University, 50, p.7 - 13, 2007/03

no abstracts in English

Journal Articles

Effect of change of environmental conditions on the elemental composition of airborne dust

Miyamoto, Yutaka; Saito, Yoko; Magara, Masaaki; Sakurai, Satoshi; Usuda, Shigekazu

Journal of Radioanalytical and Nuclear Chemistry, 271(1), p.83 - 88, 2007/01

 Times Cited Count:0 Percentile:0.01(Chemistry, Analytical)

Airborne dust samples were collected with a high-volume sampler at a fixed point in JAERI-Tokai for three years. Recently at JAERI-Tokai, a number of pine trees to arrest sand shifting was cut down. We analyzed the variation in elemental composition of the dust collected before and after felling the trees. It found, from the two-dimentional plots of ratio of elemental concentration such as Sc/Na-Cl/Na ratios, almost all samples consisted of mixture of sea-salt and soil. There were some differences between the elemental composition of the dust collected before and after felling the trees.

Journal Articles

Half-life of $$^{184}$$Re populated by the $$(gamma,n)$$ reaction from laser Compton scattering $$gamma$$ rays at the electron storage ring NewSUBARU

Hayakawa, Takehito; Miyamoto, Shuji*; Hayashi, Yukio; Kawase, Keigo*; Horikawa, Ken*; Chiba, Satoshi; Nakanishi, Kosuke*; Hashimoto, Hisanobu*; Ota, Takeshi*; Kando, Masaki; et al.

Physical Review C, 74(6), p.065802_1 - 065802_5, 2006/12

 Times Cited Count:23 Percentile:79.56(Physics, Nuclear)

We report a half-life of the ground state of $$^{184}$$Re populated by the $$^{185}$$Re$$(gamma,n)$$$$^{184}$$Re reaction with the laser Compton scattering $$gamma$$-rays generated through relativistic engineering. The $$gamma$$-rays are provided at the electron storage ring NewSUBARU. The previous experiment using deuteron-induced reactions has yielded a recommended half-life of the 3$$^-$$ ground state of $$^{184}$$Re to be 38.0 $$pm$$ 0.5 d, including a possible contribution from the 8$$^{+}$$ isomer ($$T_{1/2}$$ = 169 $$pm$$ 8 d) of $$^{184}$$Re since the presence of the isomer was not known at that time. In contrast, the $$(gamma,n)$$ reaction has an advantage to selectively populate the ground state because this reaction does not bring large angular momentum. The measured half-life of 35.4 $$pm$$ 0.7 d is shorter than the previous half-life by about 7%. This difference is crucial for applications using the activation method.

Journal Articles

Geological distribution of plutonium isotopes of Nagasaki atomic bomb spread over Nagasaki and Kumamoto area

Kokubu, Yoko; Yasuda, Kenichiro; Magara, Masaaki; Miyamoto, Yutaka; Sakurai, Satoshi; Usuda, Shigekazu; Yamazaki, Hideo*; Yoshikawa, Shusaku*

KEK Proceedings 2006-5, p.36 - 40, 2006/11

no abstracts in English

Journal Articles

Trace analysis of uranium, thorium and lead in the environmental samples; Examination of the scheme of anion-exchange separation

Miyamoto, Yutaka; Kokubu, Yoko; Magara, Masaaki; Sakurai, Satoshi; Usuda, Shigekazu

KEK Proceedings 2006-5, p.30 - 35, 2006/11

no abstracts in English

96 (Records 1-20 displayed on this page)