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Journal Articles

Experimental study of the $$Gamma_{p1}/Gamma_{p0}$$ ratios of resonance states in $$^{8}$$Be for deducing the $$^{7}$$Be($$n$$,$$p_{1}$$)$$^{7}$$Li$$^{*}$$ reaction rate relevant to the cosmological lithium problem

Iwasa, Naohito*; Ishikawa, Shunki*; Kubono, Shigeru*; Sakakibara, T.*; Kominato, Kazuya*; Nishio, Katsuhisa; Matsuda, Makoto; Hirose, Kentaro; Makii, Hiroyuki; Orlandi, R.; et al.

Physical Review C, 103(1), p.015801_1 - 015801_5, 2021/01

 Times Cited Count:1 Percentile:19.67(Physics, Nuclear)

Journal Articles

Optimization of mechanical properties in aluminum alloys $$via$$ hydrogen partitioning control

Toda, Hiroyuki*; Yamaguchi, Masatake; Matsuda, Kenji*; Shimizu, Kazuyuki*; Hirayama, Kyosuke*; Su, H.*; Fujihara, Hiro*; Ebihara, Kenichi; Itakura, Mitsuhiro; Tsuru, Tomohito; et al.

Tetsu To Hagane, 105(2), p.240 - 253, 2019/02

 Times Cited Count:0 Percentile:0(Metallurgy & Metallurgical Engineering)

no abstracts in English

Journal Articles

Density and X-ray emission profile relationships in highly ionized high-Z laser-produced plasmas

Yoshida, Kensuke*; Fujioka, Shinsuke*; Higashiguchi, Takeshi*; Ugomori, Teruyuki*; Tanaka, Nozomi*; Kawasaki, Masato*; Suzuki, Yuhei*; Suzuki, Chihiro*; Tomita, Kentaro*; Hirose, Ryoichi*; et al.

Applied Physics Letters, 106(12), p.121109_1 - 121109_5, 2015/03

 Times Cited Count:8 Percentile:34.82(Physics, Applied)

Journal Articles

Efficient extreme ultraviolet emission from one-dimensional spherical plasmas produced by multiple lasers

Yoshida, Kensuke*; Fujioka, Shinsuke*; Higashiguchi, Takeshi*; Ugomori, Teruyuki*; Tanaka, Nozomi*; Ohashi, Hayato*; Kawasaki, Masato*; Suzuki, Yuhei*; Suzuki, Chihiro*; Tomita, Kentaro*; et al.

Applied Physics Express, 7(8), p.086202_1 - 086202_4, 2014/08

 Times Cited Count:28 Percentile:73.87(Physics, Applied)

We demonstrate high conversion efficiency for extreme ultraviolet (EUV) emission at 6.5-6.7 nm from multiple laser beam-produced one-dimensional spherical plasmas. Multiply charged-state ions produce strong resonance emission lines, which combine to yield intense unresolved transition arrays in Gd, Tb, and Mo. The maximum in-band EUV conversion efficiency was observed to be 0.8%, which is one of the highest values ever reported due to the reduction of plasma expansion loss.

Journal Articles

Single crystal growth and various electronic states in Yb-based compounds

Hirose, Yusuke*; Yoshiuchi, Shingo*; Nishimura, Naoto*; Sakaguchi, Junya*; Enoki, Kentaro*; Iwakawa, Ken*; Miura, Yasunao*; Sugiyama, Kiyohiro*; Onuki, Yoshichika; Settai, Rikio*; et al.

Journal of the Korean Physical Society, 62(12), p.1858 - 1861, 2013/06

 Times Cited Count:0 Percentile:0(Physics, Multidisciplinary)

Journal Articles

Photoluminescence properties of carbon-doped $$beta$$-FeSi$$_{2}$$ nanocrystals

Maeda, Yoshihito; Nishimura, Kentaro*; Nakajima, Takahito*; Matsukura, Bui*; Narumi, Kazumasa; Sakai, Seiji

Physica Status Solidi (C), 9(10-11), p.1884 - 1887, 2012/10

 Times Cited Count:4 Percentile:88.56

We report enhancement of intrinsic photoluminescence (PL) from $$beta$$-FeSi$$_{2}$$ nanocrystals by doping carbon. In the appropriate dose of C$$_{60}$$$$^{+}$$ ion implantation into the average nanocrystal size of 14 nm, the PL intensity was enhanced by 260% and increase of the exciton binding energy of 1.8 meV in comparison with that of the non-doped nanocrystal. Furthermore, we found that there was a clear correlation between the PL enhancement and increase of the exciton binding energy. This important result suggests that carbon atoms doped in the silicide lattice may play as an isoelectronic trap and probably form bound excitons with stable states as predicted theoretically. We found a new mechanism of the PL enhancement for $$beta$$-FeSi$$_{2}$$ nanocrystals.

Journal Articles

Enhancement of IR light emission from $$beta$$-FeSi$$_{2}$$ nanocrystals embedded in Si

Maeda, Yoshihito; Nishimura, Kentaro*; Nakajima, Takahito*; Matsukura, Bui*; Narumi, Kazumasa; Sakai, Seiji

Physica Status Solidi (C), 9(10-11), p.1888 - 1891, 2012/10

 Times Cited Count:3 Percentile:83.37

We have systematically investigated photoluminescence (PL) properties of $$beta$$-phase nanocrystals which are formed by a phase transition from metastable $$gamma$$-FeSi$$_{2}$$ with a Fluorite structure to $$beta$$-FeSi$$_{2}$$, and succeeded in enhancement of the PL intensity in the optimum conditions of double annealing process. For the PL enhancement, the time of postannealing at 800$$^{circ}$$C is dominated by the time of the preannealing at 400 or 500$$^{circ}$$C which is related to amount of the $$gamma$$-phase. After discussing some possible factors, we speculate that the PL enhancement observed in this study may be attributed mainly to improvement of the interface condition between the nanocrystal and Si, because the crystallographic epitaxial relationship among the phases, Si(111)//$$gamma$$(111)//$$beta$$(202)/(220) can be maintained during precipitation of the nanocrystal on Si(111).

Journal Articles

Transmission imaging and strain mapping in the vicinity of internal crack tip using synchrotron white X-ray

Shibano, Junichi*; Kajiwara, Kentaro*; Kiriyama, Koji*; Shobu, Takahisa; Suzuki, Kenji*; Nishimura, Suguru*; Miura, Setsuo*; Kobayashi, Michiaki*

Materials Science Forum, 638-642, p.2476 - 2481, 2010/01

Journal Articles

Study on imaging and strain mapping in the vicinity of internal crack tip using synchrotron white X-ray

Shibano, Junichi*; Kajiwara, Kentaro*; Kiriyama, Koji; Shobu, Takahisa; Suzuki, Kenji*; Nishimura, Suguru*; Miura, Setsuo*; Kobayashi, Michiaki*

Zairyo, 57(7), p.667 - 673, 2008/07

Journal Articles

Irradiation effect of 14 MeV neutron on interlaminar shear strength of glass fiber reinforced plastics

Nishimura, Arata*; Hishinuma, Yoshimitsu*; Seo, Kazutaka*; Tanaka, Teruya*; Muroga, Takeo*; Nishijima, Shigehiro*; Katagiri, Kazumune*; Takeuchi, Takao*; Shindo, Yasuhide*; Ochiai, Kentaro; et al.

AIP Conference Proceedings 824, p.241 - 248, 2005/09

Design activity of International Thermonuclear Experimental Reactor clarifies intense neutron streaming from ports for neutral beam injectors. Energy spectrum of the streaming is very wide and 14 MeV neutron and $$gamma$$ ray are the typical radiations. Large amount of glass fiber reinforced plastics will be used in a superconducting magnet system as an electric insulation material and a support structure, for such organic material is easy to manufacture, and light and cheap. In this report, effects of 14 MeV neutron and $$gamma$$ ray irradiation on interlaminar shear strength and fracture mode are investigated using G-10CR small specimen of which configuration was proposed as a standard for evaluation of the interlaminar shear strength.

Oral presentation

Activation properties of Nb$$_{3}$$Sn, NbTi and GFRP irradiated with D-T neutrons

Ochiai, Kentaro; Nishimura, Arata*; Nishitani, Takeo; Nishijima, Shigehiro*

no journal, , 

Nb$$_{3}$$Sn, NbTi wires and glass fiber reinforced plastics (GFRP) are prospective candidate materials of the superconducting coil assembly for fusion reactors. These materials are activated by D-T neutrons penetrating through the reactor core. From the radioactive waste point of view, it is important to investigate the activation properties for these candidate materials. However, no experiment has been done to investigate the activation properties for these materials. Therefore, we have carried out the experimental investigation of the activation properties of Nb$$_{3}$$Sn, NbTi wires and GFRP materials. The neutron irradiation experiment has been done by the FNS D-T neutron source of JAEA. We used complex multi-filaments wires of Nb$$_{3}$$Sn and NbTi produced by FURUKAWA-electric Ltd. and a commercial GFRP (G10CR) plate. These samples were irradiated up to the neutron fluence of 4$$times$$10$$^{19}$$n/m$$^{2}$$ corresponding to about one twentieth neutron fluence expected for ITER life time. After the cooling time, the dose rates and the emitted $$gamma$$-ray spectra were measured with a survey meter and a Ge detector, respectively. Induced major radioactive nuclides are Nb-92m, Sn-117m, Sn-113 and Co-60 for Nb$$_{3}$$Sn, and Nb-92m, Sc-46 and Co-60 for NbTi. Also Na-24, Na-22, Sc-47, Co-57, As-74, Rb-83, Mn-54 and some unknown radioactive nuclides were observed from the irradiated GFRP. It is considered that those radioactive elements are due to the activation of the additive compounds in GFRP. The initial dose rates of the irradiated Nb$$_{3}$$Sn, NbTi and GFRP samples were 160$$mu$$Sv/h, 120$$mu$$Sv/h and 20$$mu$$Sv/h, respectively. After 5 months from the irradiation, these dose rates were reduced to 2-4$$mu$$Sv/h. Also, from the measured $$gamma$$-ray spectra, it was found that the final dose rates of Nb$$_{3}$$Sn and NbTi wires were dominated by Co-60 (5.27y) and the that of GFRP was dominated by Na-22 (2.60y).

Oral presentation

Irradiation effect of D-T neutron on superconducting magnet materials for fusion

Nishimura, Arata*; Hishinuma, Yoshimitsu*; Seo, Kazutaka*; Tanaka, Teruya*; Muroga, Takeo*; Nishijima, Shigehiro*; Katagiri, Kazumune*; Takeuchi, Takao*; Shindo, Yasuhide*; Ochiai, Kentaro; et al.

no journal, , 

A fusion device which creates burning plasma will be equipped with a superconducting magnet system to provide strong magnetic field and maintain the burning plasma. The fusion device also will have plasma heating devices such as neutral beam injectors and electron cyclotron systems. Since these systems need several ports to carry in the energy into plasma, the fusion device has large ports connecting to the systems locates in outside of cryostat. Through these ports, D-T neutron will come out of the burning plasma and damage the surrounding materials. The superconducting magnets also will be irradiated by the streaming neutron. To investigate mechanisms of degradation of superconducting properties, and to construct database of irradiation effect on superconducting magnet materials, a cryogenic target system has been install in Fusion Neutronics Source (FNS) at Japan Atomic Energy Agency (JAEA). The irradiation tests with D-T neutron have been carried out three times and some irradiation effects on superconducting magnet materials are clarified. In this paper, the present status of the cryogenic target system and some irradiation test results will be summarized and presented.

Oral presentation

Stress measurement of welding zone in steel material by high energy white synchrtron radiation

Kiriyama, Koji; Shibano, Junichi*; Nishimura, Suguru*; Shobu, Takahisa; Kaneko, Hiroshi; Kajiwara, Kentaro*; Suzuki, Kenji*

no journal, , 

no abstracts in English

Oral presentation

Strain measurement and computed tomography of cracking zone in steel material by high energy white synchrotron radiation

Kiriyama, Koji; Shibano, Junichi*; Kajiwara, Kentaro*; Shobu, Takahisa; Suzuki, Kenji*; Kaneko, Hiroshi; Nishimura, Suguru*; Arai, Takayuki*

no journal, , 

Residual stress measurement is important to understand SCC (Stress Corrosion Cracking) process. In this study, CT (Computed Tomography) imaging and inner strain mapping of steel material (alpha-Fe) have performed at BL28B2 at SPring-8. The result showed that artificial cracking in the sample was clearly measured by CT and that strain maps quite correspond to CT image. Therefore, these methods are very effective tool to measure an inner state of steel material.

Oral presentation

Measurement of stress and imaging in the vicinity of fatigue crack in steel material using synchrotron radiation white X-rays

Kiriyama, Koji; Shibano, Junichi*; Kajiwara, Kentaro*; Shobu, Takahisa; Suzuki, Kenji*; Kaneko, Hiroshi; Nishimura, Suguru*; Arai, Takayuki*; Miura, Setsuo*; Kobayashi, Michiaki*

no journal, , 

Residual stress measurement is important to understand Stress Corrosion Cracking process. In this study, measurements of imaging and inner stress mapping around a crack-tip in steel material (alpha-Fe) have performed at beam-line BL14B1 and BL28B2 at SPring-8. The results showed that artificial cracking in the sample was clearly measured by imaging and that stress maps quite correspond to the result of imaging. Therefore, these methods are very effective tool for measurement of inner state of steel material.

Oral presentation

Neutron irradiation effect on superconducting magnet materials

Nishimura, Arata*; Takeuchi, Takao*; Nishijima, Shigehiro*; Ochiai, Kentaro; Takakura, Kosuke; Shikama, Tatsuo*; Sato, Isamu*; Watanabe, Kazuo*; Nishijima, Gen*

no journal, , 

no abstracts in English

Oral presentation

Dependence of Mn content on interdiffusion behaviors at Fe$$_{2}$$MnSi/Ge(111) interfaces

Matsukura, Bui*; Nakajima, Takahito*; Nishimura, Kentaro*; Narumi, Kazumasa; Sakai, Seiji; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

Light emission from C$$_{60}$$ ion implanted $$beta$$-FeSi$$_{2}$$ with different crystal morphologies

Nakajima, Takahito*; Nishimura, Kentaro*; Matsukura, Bui*; Narumi, Kazumasa; Sakai, Seiji; Maeda, Yoshihito

no journal, , 

no abstracts in English

Oral presentation

Combination of LIBS and fiber endoscopic observation in limited tubular space

Nishimura, Akihiko; Ito, Fuyumi; Terada, Takaya; Tomiyoshi, Kentaro; Oka, Kiyoshi

no journal, , 

no abstracts in English

Oral presentation

Thermal stability of Fe$$_{2}$$MnSi/Ge(111) heteroepitaxial interfaces; Mn-concentration dependence

Maeda, Yoshihito; Nishimura, Kentaro*; Nagasawa, Yoshiyuki*; Narumi, Kazumasa; Sakai, Seiji

no journal, , 

no abstracts in English

28 (Records 1-20 displayed on this page)