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Journal Articles

Feasibility study of PGAA for boride identification in simulated melted core materials

Tsuchikawa, Yusuke; Abe, Yuta; Oishi, Yuji*; Kai, Tetsuya; Toh, Yosuke; Segawa, Mariko; Maeda, Makoto; Kimura, Atsushi; Nakamura, Shoji; Harada, Masahide; et al.

JPS Conference Proceedings (Internet), 33, p.011074_1 - 011074_6, 2021/03

In the decommissioning of the Fukushima-Daiichi (1F) Nuclear Power Plant, it is essential to understand characteristics of the melted core materials. The estimation of boride in the real debris is of great importance to develop safe debris removal plans. Hence, it is required to investigate the amount of boron in the melted core materials with nondestructive methods. Prompt gamma-ray activation analysis (PGAA) is one of the useful techniques to determine the amount of borides by means of the 478 keV prompt gamma-ray from neutron absorption reaction of boron. Moreover, it is well known that the width of the 478 keV gamma-ray peak is typically broadened due to the Doppler effect. The degree of the broadening is affected by coexisting materials, and can be recognized by the width of the prompt gamma-ray peak. As a feasibility study, the prompt gamma-ray from boride samples were measured using the ANNRI, NOBORU, and RADEN beamlines at the Materials and Life Science Experimental Facility (MLF) of Japan Proton Accelerator Complex (J-PARC).

Journal Articles

Quasifree neutron knockout reaction reveals a small $$s$$-Orbital component in the Borromean nucleus $$^{17}$$B

Yang, Z. H.*; Kubota, Yuki*; Corsi, A.*; Yoshida, Kazuki; Sun, X.-X.*; Li, J. G.*; Kimura, Masaaki*; Michel, N.*; Ogata, Kazuyuki*; Yuan, C. X.*; et al.

Physical Review Letters, 126(8), p.082501_1 - 082501_8, 2021/02

AA2020-0819.pdf:1.29MB

 Times Cited Count:31 Percentile:96.65(Physics, Multidisciplinary)

A quasifree ($$p$$,$$pn$$) experiment was performed to study the structure of the Borromean nucleus $$^{17}$$B, which had long been considered to have a neutron halo. By analyzing the momentum distributions and exclusive cross sections, we obtained the spectroscopic factors for $$1s_{1/2}$$ and $$0d_{5/2}$$ orbitals, and a surprisingly small percentage of 9(2)% was determined for $$1s_{1/2}$$. Our finding of such a small $$1s_{1/2}$$ component and the halo features reported in prior experiments can be explained by the deformed relativistic Hartree-Bogoliubov theory in continuum, revealing a definite but not dominant neutron halo in $$^{17}$$B. The present work gives the smallest $$s$$- or $$p$$-orbital component among known nuclei exhibiting halo features and implies that the dominant occupation of $$s$$ or $$p$$ orbitals is not a prerequisite for the occurrence of a neutron halo.

Journal Articles

$$omega N$$ scattering length from $$omega$$ photoproduction on the proton near the reaction threshold

Ishikawa, Takatsugu*; Fujimura, Hisako*; Fukasawa, Hiroshi*; Hashimoto, Ryo*; He, Q.*; Honda, Yuki*; Hosaka, Atsushi; Iwata, Takahiro*; Kaida, Shun*; Kasagi, Jirota*; et al.

Physical Review C, 101(5), p.052201_1 - 052201_6, 2020/05

Journal Articles

Neutron capture cross-section measurement and resolved resonance analysis of $$^{237}$$Np

Rovira, G.*; Katabuchi, Tatsuya*; Tosaka, Kenichi*; Matsuura, Shota*; Terada, Kazushi*; Iwamoto, Osamu; Kimura, Atsushi; Nakamura, Shoji; Iwamoto, Nobuyuki; Segawa, Mariko; et al.

Journal of Nuclear Science and Technology, 57(1), p.24 - 39, 2020/01

 Times Cited Count:8 Percentile:79.84(Nuclear Science & Technology)

Journal Articles

Characterisation of structural similarities of precipitates in Mg-Zn and Al-Zn-Mg alloys systems

Bendo, A.*; Maeda, Tomoyoshi*; Matsuda, Kenji*; Lervik, A.*; Holmestad, R.*; Marioara, C. D.*; Nishimura, Katsuhiko*; Nunomura, Norio*; Toda, Hiroyuki*; Yamaguchi, Masatake; et al.

Philosophical Magazine, 99(21), p.2619 - 2635, 2019/07

 Times Cited Count:26 Percentile:83.26(Materials Science, Multidisciplinary)

Journal Articles

Fluorination of PMDA-ODA polyimide using hyperthermal atomic fluorine beams

Tagawa, Masahito*; Yokota, Kumiko*; Maeda, Kenichi*; Yoshigoe, Akitaka; Teraoka, Yuden; Akamatsu, Kensuke*; Nawafune, Hidemi*

Polyimides and Other High-Temperature Polymers; Synthesis, Characterization and Applications, Vol.5, p.249 - 259, 2009/08

Surface fluorination of PMDA-ODA polyimide has been performed by a hyperthermal F beam. The fundamental properties of the F-beam-exposed polyimide surface are reported based on the analytical results by X-ray photoelectron spectroscopy and contact angle measurements. It was observed that CF, CF$$_{2}$$ or CF$$_{3}$$ moieties were formed at the polyimide surfaces depending on the F beam fluences. Advancing contact angles of water can be controlled from 60 to 120 degrees by varying the F beam fluences. Surface roughness analyzed by atomic force microscopy slightly increased with atomic F beam exposures due probably to the formation of volatile products such as CF$$_{4}$$. This is confirmed by the mass change during F beam exposure by a quartz crystal microbalance.

Journal Articles

Atomic layer fluorination of highly oriented pyrolytic graphite using hyperthermal atomic fluorine beam

Tagawa, Masahito*; Yokota, Kumiko*; Maeda, Kenichi*; Yoshigoe, Akitaka; Teraoka, Yuden

Applied Physics Express, 2(6), p.066002_1 - 066002_3, 2009/06

 Times Cited Count:3 Percentile:14.46(Physics, Applied)

Hyperthermal (kinetic energy of 10 eV) fluorine atom beam interaction with highly oriented pyrolytic graphite (HOPG) was studied. Surface analytical results of atomic fluorine-exposed HOPG using synchrotron radiation photoelectron spectroscopy showed that the fluorine reaction was limited at the topmost HOPG(0001) layer. This is due to the fact that the kinetic energy of 10 eV is not sufficient to penetrate graphite layer but is enough for breaking C-C bonds and forms CF and CF$$_{2}$$ functional groups through the beam-induced fluorination reactions. It was demonstrated that the use of hyperthermal energy in the range of 10 eV is advantageous for damage-free modification of the topmost surface of carbon-based materials.

Journal Articles

Supernova nucleosynthesis in the early universe

Tominaga, Nozomu*; Umeda, Hideyuki*; Maeda, Keiichi*; Nomoto, Kenichi*; Iwamoto, Nobuyuki

Proceedings of the International Astronomical Union, Volume 4, Symposium S255, p.189 - 193, 2008/06

 Times Cited Count:1 Percentile:48.95

The first metal enrichment in the universe was made by supernova (SN) explosions of population (Pop) III stars. The trace remains in abundance patterns of extremely metal-poor (EMP) stars. We investigate the properties of nucleosynthesis in Pop III SNe by means of comparing their yields with the abundance patterns of the EMP stars. We focus on (1) jet-induced SNe with various energy deposition rates [$$dot{E}_{rm dep}=(0.3-1500)times 10^{51}$$ ergs s$$^{-1}$$], and (2) SNe of stars with various main-sequence masses ($$M_{rm ms}=13-50M_odot$$) and explosion energies [$$E=(1-40)times10^{51}$$ ergs]. The varieties of Pop III SNe can explain varieties of the EMP stars: (1) higher [C/Fe] for lower [Fe/H] and (2) trends of abundance ratios [X/Fe] against [Fe/H].

Journal Articles

Supernova nucleosynthesis and extremely metal-poor stars

Tominaga, Nozomu*; Umeda, Hideyuki*; Maeda, Keiichi*; Iwamoto, Nobuyuki; Nomoto, Kenichi*

AIP Conference Proceedings 1016, p.49 - 54, 2008/05

We investigate hydrodynamical and nucleosynthetic properties of the jet-induced explosion of a population III 40M$$_odot$$ star with a two-dimensional special relativistic hydrodynamical code and compare the abundance patterns of the yields with those of the metal-poor stars. We conclude that (1) the ejection of Fe-peak products and the fallback of unprocessed materials can account for the abundance patterns of the extremely metal-poor stars and that (2) the jet-induced explosion with different energy deposition rates can explain the difference of the abundance patterns of the metal-poor stars.

Journal Articles

Microdosimetric study for secondary neutrons in phantom produced by a 290 MeV/nucleon carbon beam

Endo, Satoru*; Tanaka, Kenichi*; Takada, Masashi*; Onizuka, Yoshihiko*; Miyahara, Nobuyuki*; Sato, Tatsuhiko; Ishikawa, Masayoshi*; Maeda, Naoko*; Hayabuchi, Naofumi*; Shizuma, Kiyoshi*; et al.

Medical Physics, 34(9), p.3571 - 3578, 2007/09

 Times Cited Count:7 Percentile:26.01(Radiology, Nuclear Medicine & Medical Imaging)

Absorbed doses from main charged particle beams and charged-particle fragments have been measured with high accuracy for particle therapy but there are few reports for doses from neutron components produced as fragments. This study describes measurements on neutron dose produced by carbon beam, microdosimetric distributions of secondary neutrons produced by 290 MeV/nucleon carbon beams have been measured by using a tissue equivalent proportional counter (TEPC) at the Heavy Ion Medical Accelerator in Chiba (HIMAC) at the National Institute of Radiological Sciences (NIRS). The ratios of neutrons to charged particle fragments dominated to be 11 to 89 % in the absorbed doses at the side and below the faces of the acrylic phantom (300 mm height $$times$$ 300 mm width $$times$$ 253 mm thickness).

Journal Articles

The Connection between $$gamma$$-ray bursts and extremely metal-poor stars; Black hole-forming supernovae with relativistic jets

Tominaga, Nozomu*; Maeda, Keiichi*; Umeda, Hideyuki*; Nomoto, Kenichi*; Tanaka, Masaomi*; Iwamoto, Nobuyuki; Suzuki, Tomoharu*; Mazzali, P. A.*

Astrophysical Journal, 657(2, Part2), p.L77 - L80, 2007/03

 Times Cited Count:115 Percentile:92.09(Astronomy & Astrophysics)

Long-duration $$gamma$$-ray bursts (GRBs) are thought to be connected with luminous and energetic Type Ic supernovae [SNe, called hypernovae (HNe)] resulting from the black-hole (BH) forming collapse of massive stars. For GRBs 060505 and 060614, however, the expected SNe have not been detected. The upper limits to the SN brightness are about 100 times fainter than GRB-associated HNe (GRB-HNe), corresponding to the upper limits to the ejected $$^{56}$$Ni masses of $$M(^{56}$$Ni)$$sim 10^{-3}M_odot$$. SNe with a small amount of $$^{56}$$Ni ejection are observed as faint Type II SNe. HNe and faint SNe are thought to be responsible for the formaion of extremely metal-poor (EMP) stars. A relativistic jet-induced BH forming explosion of the 40$$M_odot$$ star is investigated and hydrodynamic and nucleosynthetic models are presented. These models can explain both GRB-HNe and GRBs without bright SNe in a unified manner. We suggest that GRBs without bright SNe are likely to synthesize $$M(^{56}$$Ni)$$sim 10^{-4}-10^{-3}M_odot$$ or $$sim 10^{-6}M_odot$$.

Journal Articles

Chemical abundances in the secondary star of the black hole binary V4641 Sagittarii (SAX J1819.3-2525)

Sadakane, Kozo*; Arai, Akira*; Aoki, Wako*; Arimoto, Nobuo*; Hidai, Masahide*; Onishi, Takashi*; Tajitsu, Akito*; Beers, T. C.*; Iwamoto, Nobuyuki; Tominaga, Nozomu*; et al.

Publications of the Astronomical Society of Japan, 58(3), p.595 - 604, 2006/06

 Times Cited Count:11 Percentile:32.02(Astronomy & Astrophysics)

We report detailed spectroscopic studies performed for the secondary star in the black hole binary (micro-quasar) V4641 Sgr in order to examine its surface chemical composition and to see if its surface shows any signature of pollution by ejecta from a supernova explosion. We obtain abundances of 10 elements and find definite over-abundances of N (by 0.8 dex or more) and Na (by 0.8 dex) in V4641 Sgr. From line-by-line comparisons of eight other elements (C, O, Mg, Al, Si, Ti, Cr, Fe) between V4641 Sgr and the two normal late B-type stars, which have been reported to have solar abundances. An evolutionary model of a massive close binary system has been constructed to explain the abundances observed in V4641 Sgr. The model suggests that the BH forming supernova in this system was a dark one.

Journal Articles

The First chemical enrichment in the universe and the formation of hyper metal-poor stars

Iwamoto, Nobuyuki; Umeda, Hideyuki*; Tominaga, Nozomu*; Nomoto, Kenichi*; Maeda, Keiichi*

Science, 309(5733), p.451 - 453, 2005/07

 Times Cited Count:223 Percentile:97.43(Multidisciplinary Sciences)

The recent discovery of a hyper-metal-poor (HMP) star, with a metallicity Fe/H smaller than 1/100,000 of the solar ratio, together with one earlier HMP star, has raised a challenging question whether these HMP stars are the actual first-generation, low-mass stars of the universe. We argue that these HMP stars are the second-generation stars formed from gases that were chemically enriched by the first-generation supernovae. The key to this solution is the very unusual abundance patterns of these HMP stars and the similarities and differences between them. We can reproduce these abundance features with core-collapse "faint" supernova models that include extensive matter mixing and fallback during explosions.

Journal Articles

Status of studies on HLW glass performance for confirming its validity in assessment

Inagaki, Yaohiro*; Mitsui, Seiichiro*; Makino, Hitoshi*; Ishiguro, Katsuhiko*; Kamei, Gento*; Kawamura, Kazuhiro*; Maeda, Toshikatsu; Ueno, Kenichi*; Bamba, Tsunetaka*; Yui, Mikazu*

Genshiryoku Bakkuendo Kenkyu, 10(1-2), p.69 - 84, 2004/03

no abstracts in English

Journal Articles

The Effect of temperature, pressure, and sulfur content on viscosity of the Fe-FeS melt

Terasaki, Hidenori*; Kato, Takumi*; Urakawa, Satoru*; Funakoshi, Kenichi*; Suzuki, Akio*; Okada, Taku; Maeda, Makoto*; Sato, Jin*; Kubo, Tomoaki*; Kasai, Shizu*

Earth and Planetary Science Letters, 190(1-2), p.93 - 101, 2001/07

 Times Cited Count:52 Percentile:68.67(Geochemistry & Geophysics)

The Fe-FeS melt is thought to be the major candidate of the outer core material. Its viscosity is one of the most important physical properties to study the dynamics of the convection in the outer core. We performed the in situ viscosity measurement of the Fe-FeS melt under high pressure using X-ray radiography falling sphere method with a novel sample assembly. Viscosity was measures in the temperature, pressure, and compositional conditions of 1233-1923 K, 1.5-6.9 GPa, and Fe-Fe $$_{72}$$ S $$_{28}$$ (wt %), respectively. The viscosity coefficients obtained by 17 measurements change systematically in the range of 0.008-0.036 Pa s. An activation energy of the viscous flow, 30 kJ/mol, and the activation volume, 1.5 cm $$^{3}$$ /mol, are determined as the temperature and pressure dependence, and the viscosity of the Fe $$_{72}$$ S $$_{28}$$ melt is found to be smaller than that of the Fe melt by 15 %. These tendencies can be well correlated with the structural variation of the Fe-FeS melt.

Journal Articles

Effect of seismic isolation on the tokamak in ITER

Tsunematsu, Toshihide; Namba, Haruyuki*; Akutsu, Yoichi; Okawa, Yoshinao; Yagenji, Akira; Takeda, Masatoshi*; Yajima, Kensaku*; Nitta, Yoshio*; Kobayashi, Kenichi*; Maeda, Ikuo*; et al.

Fusion Engineering and Design, 41(1-4), p.415 - 420, 1998/09

 Times Cited Count:3 Percentile:31.9(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Chemical forms of solid fission products in the irradiated uranium-plutonium mixed nitride fuel

Arai, Yasuo; Maeda, Atsushi; Shiozawa, Kenichi; Omichi, Toshihiko

Journal of Nuclear Materials, 210, p.161 - 166, 1994/00

 Times Cited Count:28 Percentile:89.33(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Fabrication of uranium-plutonium mixed nitride fuel pins for irradiation tests in JMTR

Arai, Yasuo; ; Iwai, Takashi; Maeda, Atsushi; ; Shiozawa, Kenichi; Omichi, Toshihiko

Journal of Nuclear Science and Technology, 30(8), p.824 - 830, 1993/08

 Times Cited Count:7 Percentile:60.47(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Fabrication of uranium-plutonium mixed nitride fuel pins(89F-3A) for second irradiation test at JMTR

; Iwai, Takashi; ; Maeda, Atsushi; Arai, Yasuo; Shiozawa, Kenichi; Omichi, Toshihiko

JAERI-M 91-078, 39 Pages, 1991/05

JAERI-M-91-078.pdf:1.19MB

no abstracts in English

Oral presentation

Population III supernovae and the abundance pattern of UMP stars

Iwamoto, Nobuyuki; Umeda, Hideyuki*; Tominaga, Nozomu*; Nomoto, Kenichi*; Maeda, Keiichi*

no journal, , 

The recent discovery of a hyper-metal-poor (HMP) star, with a metallicity Fe/H smaller than 1/100,000 of the solar ratio, together with one earlier HMP star, has raised a challenging question whether these HMP stars are the actual first-generation, low-mass stars of the universe. We argue that these HMP stars are second-generation stars formed from gases that were chemically enriched by the first-generation supernovae. The key to this solution is the very unusual abundance patterns of these HMP stars and the similarities and differences between them. We can reproduce these abundance features with core-collapse "faint" supernova models that include extensive matter mixing and fallback during explosions.

35 (Records 1-20 displayed on this page)