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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

How different is the core of $$^{25}$$F from $$^{24}$$O$$_{g.s.}$$ ?

Tang, T. L.*; Uesaka, Tomohiro*; Kawase, Shoichiro; Beaumel, D.*; Dozono, Masanori*; Fujii, Toshihiko*; Fukuda, Naoki*; Fukunaga, Taku*; Galindo-Uribarri, A.*; Hwang, S. H.*; et al.

Physical Review Letters, 124(21), p.212502_1 - 212502_6, 2020/05

 Times Cited Count:14 Percentile:74.77(Physics, Multidisciplinary)

The structure of a neutron-rich $$^{25}$$F nucleus is investigated by a quasifree ($$p,2p$$) knockout reaction. The sum of spectroscopic factors of $$pi 0d_{5/2}$$ orbital is found to be 1.0 $$pm$$ 0.3. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus, and the core consists of $$sim$$35% $$^{24}$$O$$_{rm g.s.}$$, and $$sim$$65% excited $$^{24}$$O. The result shows that the $$^{24}$$O core of $$^{25}$$F nucleus significantly differs from a free $$^{24}$$O nucleus. The result may infer that the addition of the $$0d_{5/2}$$ proton considerably changes the neutron structure in $$^{25}$$F from that in $$^{24}$$O, which could be a possible mechanism responsible for the oxygen dripline anomaly.

Journal Articles

Characterization study of four candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station

Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Nauchi, Yasushi*; Maeda, Makoto; Sagara, Hiroshi*; Kosuge, Yoshihiro*; Kureta, Masatoshi; Tomikawa, Hirofumi; Okumura, Keisuke; et al.

Energy Procedia, 131, p.258 - 263, 2017/12

 Times Cited Count:8 Percentile:98.37

Journal Articles

Characterization study of four candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station (Interim report)

Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Maeda, Makoto; Nauchi, Yasushi*; Sagara, Hiroshi*; Kosuge, Yoshihiro*; Kureta, Masatoshi; Tomikawa, Hirofumi; Okumura, Keisuke; et al.

Proceedings of INMM 57th Annual Meeting (Internet), 10 Pages, 2016/07

Journal Articles

Development of a microcalorimeter with transition edge sensor for detection of LX rays emitted by transuranium elements

Nakamura, Keisuke; Maeda, Makoto*; Yasumune, Takashi*; Maehata, Keisuke*; Ishibashi, Kenji*; Tanaka, Keiichi*; Umeno, Takahiro*; Takasaki, Koji; Momose, Takumaro

Radiation Protection Dosimetry, 146(1-3), p.88 - 91, 2011/07

 Times Cited Count:1 Percentile:10.77(Environmental Sciences)

A Transition Edge Sensor (TES) microcalorimeter has been developed for use as an energy dispersive X-ray spectrometer. A TES microcalorimeter is a thermal detector used to measure the energy of an incident photon with increase in temperature. In this work, a TES microcalorimeter with a 5$$mu$$m Au absorber was developed for use in measuring LX rays emitted from transuranium elements. Furthermore, as a cooling system a dilution refrigerator utilizing a Gifford-McMahon refrigerator was used, which needs no liquid helium. The performance of the TES microcalorimeter was evaluated by measuring the LX rays emitted by an $$^{241}$$Am source. This system proved effective in the measurement of the LX rays because the full width at half maximum of the L$$_{beta1}$$X ray was about 80 eV.

Journal Articles

$$^{13}$$C-selective infrared multiple photon dissociation of $$beta$$-propiolactone by a free electron laser

Miyomoto, Yoshiki*; Majima, Tetsuro*; Arai, Shigeyoshi*; Katsumata, Keiichi*; Akagi, Hiroshi; Maeda, Akihiko*; Hata, Hiroo*; Kuramochi, Koji*; Kato, Yoshiyasu*; Tsukiyama, Koichi*

Nuclear Instruments and Methods in Physics Research B, 269(2), p.180 - 184, 2011/01

 Times Cited Count:12 Percentile:66.95(Instruments & Instrumentation)

Journal Articles

Microbeam irradiation facilities for radiobiology in Japan and China

Kobayashi, Yasuhiko; Funayama, Tomoo; Hamada, Nobuyuki*; Sakashita, Tetsuya; Konishi, Teruaki*; Imaseki, Hitoshi*; Yasuda, Keisuke*; Hatashita, Masanori*; Takagi, Keiichi*; Hatori, Satoshi*; et al.

Journal of Radiation Research, 50(Suppl.A), p.A29 - A47, 2009/03

 Times Cited Count:37 Percentile:72.85(Biology)

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

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.

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.

Oral presentation

High linear power irradiation test with Am-MOX fuels, 7; Evaluation of the thermal design aspect for FBR MOX fuels

Ikusawa, Yoshihisa; Kikuchi, Keiichi; Ozawa, Takayuki; Maeda, Seiichiro; Nakajima, Hiroshi*; Koike, Naoto

no journal, , 

To study the thermal performance of Am-MOX fuels, the high linear power irradiation test with Am-MOX fuels "B14 irradiation test" was carried out in the fast experimental reactor "JOYO". From the result of the irradiation test, the thermal performance for Am-MOX fuel was confirmed and the fuel irradiation behavior code was verified.

Oral presentation

Spectroscopic measurement of LX-rays emitted by transuranium elements using TES microcalorimeter

Maeda, Makoto*; Maehata, Keisuke*; Iyomoto, Naoko*; Ishibashi, Kenji*; Takasaki, Koji; Nakamura, Keisuke; Aoki, Katsunori; Mitsuda, Kazuhisa*; Tanaka, Keiichi*

no journal, , 

no abstracts in English

Oral presentation

The Spectroscopy of LX-rays emitted from transuranium element using transition edge sensor microcalorimeter

Nakamura, Keisuke; Maeda, Makoto*; Aoki, Katsunori; Yasumune, Takashi; Takasaki, Koji; Maehata, Keisuke*; Iyomoto, Naoko*; Ishibashi, Kenji*; Mitsuda, Kazuhisa*; Tanaka, Keiichi*

no journal, , 

no abstracts in English

Oral presentation

Study of high resolution spectroscopy of LX-rays emitted from TRU using TES microcalorimeter

Nakamura, Keisuke; Aoki, Katsunori; Takasaki, Koji; Maeda, Makoto*; Maehata, Keisuke*; Iyomoto, Naoko*; Ishibashi, Kenji*; Mitsuda, Kazuhisa*; Tanaka, Keiichi*

no journal, , 

no abstracts in English

Oral presentation

Characterization study of candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station, 1; General outline

Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Maeda, Makoto; Nauchi, Yasushi*; Sagara, Hiroshi*; Kureta, Masatoshi; Tomikawa, Hirofumi; Okumura, Keisuke; Heinberg, C.; et al.

no journal, , 

no abstracts in English

Oral presentation

Characterization study of candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station, 1; General outline

Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Nauchi, Yasushi*; Sagara, Hiroshi*; Kosuge, Yoshihiro*; Okumura, Keisuke; Maeda, Makoto; Toh, Yosuke; Hori, Keiichiro

no journal, , 

no abstracts in English

Oral presentation

Characterization study of four candidate technologies for nuclear material quantification in fuel debris at Fukushima Daiichi Nuclear Power Station, 1; General outline

Nagatani, Taketeru; Komeda, Masao; Shiba, Tomooki; Nauchi, Yasushi*; Sagara, Hiroshi*; Kosuge, Yoshihiro*; Okumura, Keisuke; Maeda, Makoto; Toh, Yosuke; Hori, Keiichiro

no journal, , 

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