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Journal Articles

Prospect for application of compact accelerator-based neutron source to neutron engineering diffraction

Ikeda, Yoshimasa*; Taketani, Atsushi*; Takamura, Masato*; Sunaga, Hideyuki*; Kumagai, Masayoshi*; Oba, Yojiro*; Otake, Yoshie*; Suzuki, Hiroshi

Nuclear Instruments and Methods in Physics Research A, 833, p.61 - 67, 2016/10

 Times Cited Count:29 Percentile:97.29(Instruments & Instrumentation)

A compact accelerator-based neutron source has been lately discussed on engineering applications such as transmission imaging and small angle scattering as well as reflectometry. However, nobody considers using it for neutron diffraction experiment because of its low neutron flux. In this study, therefore, the neutron diffraction experiments are carried out using Riken Accelerator-driven Compact Neutron Source (RANS), to clarify the capability of the compact neutron source for neutron engineering diffraction. The diffraction pattern from a ferritic steel was successfully measured by suitable arrangement of the optical system to reduce the background noise, and it was confirmed that the recognizable diffraction pattern can be measured by the large sampling volume with 10 mm in cubic for an acceptable measurement time, i.e. 10 minutes. The minimum resolution of the 110 reflection for RANS is approximately 2.5 % at 8 $$mu$$s of the proton pulse width, which is insufficient to perform the strain measurement by neutron diffraction. The moderation time width at the wavelength corresponding to the 110 reflection is estimated to be approximately 30 $$mu$$s, which is the most dominant factor to determine the resolution. Therefore, refinements of the moderator system to decrease the moderation time are important to improve the resolution of the diffraction experiment using the compact neutron source. In contrast, the texture evolution due to plastic deformation was successfully observed by measuring a change in the diffraction peak intensity by RANS. Furthermore, the volume fraction of the austenite phase was also successfully evaluated by fitting the diffraction pattern using a Rietveld code. Consequently, RANS was proved to be capable for neutron engineering diffraction aiming for the easy access measurement of the texture and the amount of retained austenite.

Journal Articles

Non-destructive texture measurement of steel sheets with compact neutron source "RANS"

Takamura, Masato*; Ikeda, Yoshimasa*; Sunaga, Hideyuki*; Taketani, Atsushi*; Otake, Yoshie*; Suzuki, Hiroshi; Kumagai, Masayoshi*; Hama, Takayuki*; Oba, Yojiro*

Journal of Physics; Conference Series, 734(Part B), p.032047_1 - 032047_4, 2016/08

 Times Cited Count:4 Percentile:87.32

Neutron diffraction is well known to be a useful technique for measuring a bulk texture of metallic materials taking advantage of a large penetration depth of the neutron beam. However, this technique has not been widely utilized for the texture measurement because large facilities like a reactor or a large accelerator are required in general. In contrast, RANS (Riken Accelerator-driven Compact Neutron Source) has been developed as a neutron source which can be used easily in laboratories. In this study, texture evolution in steel sheets with plastic deformation was successfully measured using RANS. The results show the capability of the compact neutron source for the analysis of the crystal structure of metallic materials, which leads us to a better understanding of plastic deformation behavior.

Journal Articles

Oxygen isotope separation utilizing two-frequency infrared multiphoton dissociation of 2,3-dihydropyran

Hashimoto, Masashi; Oba, Hironori; Yokoyama, Atsushi

Applied Physics B, 104(4), p.969 - 974, 2011/09

 Times Cited Count:0 Percentile:0(Optics)

Oxygen isotope separation has been examined by utilizing the two-frequency infrared multiphoton dissociation (IRMPD) of 2,3-dihydropyran (DHP). The two-frequency IRMPD reduces remarkably the required laser fluence. For example, dissociation probability of DHP containing $$^{18}$$O (D($$^{18}$$O)) and enrichment factor (S) were obtained to be 1.6$$times$$10$$^{-3}$$ /pulse and 316 respectively by the simultaneous irradiation with 1052.2 cm$$^{-1}$$ photons at 0.45 J/cm$$^{2}$$ and 1031.5 cm$$^{-1}$$ photons at 1.06 J/cm$$^{2}$$. These are comparable with D($$^{18}$$O) = 2.2$$times$$10$$^{-3}$$ /pulse and S = 391 obtained by the single-frequency irradiation of 1033.5 cm$$^{-1}$$ photons at 2.2 J/cm$$^{2}$$. Therefore, the production rate of an $$^{18}$$O enriched dissociation product has been increased to four times or more, compared with the single-frequency IRMPD, and this two-frequency method would promise a practical large scale separation.

Journal Articles

Characterization of ablation plasma from h-BN by excimer laser irradiation

Oba, Hironori; Saeki, Morihisa; Esaka, Fumitaka; Yamada, Yoichi; Yamamoto, Hiroyuki; Yokoyama, Atsushi

Journal of the Vacuum Society of Japan, 52(6), p.369 - 371, 2009/07

no abstracts in English

Journal Articles

Formation of isotopically enriched silicon film from fluorosilane produced by isotopically selective infrared multiphoton dissociation

Oba, Hironori; Suzuki, Hiroshi*; Esaka, Fumitaka; Taguchi, Tomitsugu; Yamada, Yoichi; Yamamoto, Hiroyuki; Sasase, Masato*; Yokoyama, Atsushi

Journal of the Vacuum Society of Japan, 52(6), p.292 - 295, 2009/07

no abstracts in English

Journal Articles

Rotational-coherence molecular laser isotope separation

Akagi, Hiroshi; Oba, Hironori; Yokoyama, Keiichi; Yokoyama, Atsushi; Egashira, Kazuhiro*; Fujimura, Yo*

Applied Physics B, 95(1), p.17 - 21, 2009/04

 Times Cited Count:8 Percentile:42.85(Optics)

We have proposed a laser isotope separation method, utilizing rotational coherence of a simple molecule. In the scheme, photoexcited molecules are isotopically separated by difference of rotational period between them. To illustrate this method, two-pulse photodissociation of mixed $$^{79}$$Br$$_{2}$$/$$^{81}$$Br$$_{2}$$ isotopes has been investigated theoretically. The photodissociation probabilities of $$^{79}$$Br$$_{2}$$ and $$^{81}$$Br$$_{2}$$ have been calculated as a function of time delay between the photoexcitation and dissociation laser pulses. We have demonstrated that isotope enrichment factor of $$^{79}$$Br relative to $$^{81}$$Br can be changed from 0.34 to 1.8, by simply changing the time delay only by 0.2 ns. Additionally, we have shown that this method is effective for heavy isotopes, based on mass dependence of the isotope enrichment factor.

Journal Articles

Effects of ionizing radiation on locomotory behavior and mechanosensation in ${it Caenorhabditis elegans}$

Suzuki, Michiyo; Sakashita, Tetsuya; Yanase, Sumino*; Kikuchi, Masahiro; Oba, Hirofumi; Higashitani, Atsushi*; Hamada, Nobuyuki*; Funayama, Tomoo; Fukamoto, Kana; Tsuji, Toshio*; et al.

Journal of Radiation Research, 50(2), p.119 - 125, 2009/04

 Times Cited Count:6 Percentile:22.92(Biology)

Journal Articles

Characterization of microstructures in ODS steel by a laser assisted 3DAP

Nogiwa, Kimihiro; Nishimura, Akihiko; Oba, Hironori; Yokoyama, Atsushi; Okubo, Tadakatsu*; Hono, Kazuhiro*

Materia, 47(12), P. 626, 2008/12

no abstracts in English

Journal Articles

Practical method for producing a large amount of isotopically enriched silicon by infrared multi-photon dissociation of hexafluorodisilane

Oba, Hironori; Akagi, Hiroshi; Katsumata, Keiichi*; Hashimoto, Masashi; Yokoyama, Atsushi

Japanese Journal of Applied Physics, 47(11), p.8379 - 8381, 2008/11

 Times Cited Count:4 Percentile:20.01(Physics, Applied)

This paper presents a practical method for producing highly enriched silicon isotopes utilizing laser irradiation. One- or two-frequency CO$$_{2}$$ laser irradiation has been employed to separate the desired isotope of silicon by means of infrared multi-photon dissociation (IRMPD) of the hexafluorodisilane (Si$$_{2}$$F$$_{6}$$) molecules using a flow reaction system. The production of Si$$_{2}$$F$$_{6}$$ with $$^{28}$$Si fraction of 99.1% at a rate of 0.67 g($$^{28}$$Si)/h was successfully accomplished with a high yield by the two-frequency laser irradiation. The enriched SiF$$_{4}$$ gas with $$^{30}$$Si exceeding 31% was also continuously obtained at the production rate of 0.12 g/h by the one-frequency laser irradiation.

Journal Articles

Isotopically selective infrared multiphoton dissociation of 2,3-dihydropyran

Yokoyama, Atsushi; Katsumata, Keiichi*; Oba, Hironori; Akagi, Hiroshi; Saeki, Morihisa; Yokoyama, Keiichi

Journal of Physical Chemistry A, 112(29), p.6571 - 6577, 2008/07

 Times Cited Count:4 Percentile:13.09(Chemistry, Physical)

Oxygen isotope separation has been examined by using an infrared multiphoton dissociation of 2,3-dihydropyran. Enrichment factor has been measured by the CO$$_{2}$$ laser irradiation of the samples as a function of laser frequency, laser fluence, and sample pressure. Maximum enrichment factor of 751 has been obtained, and $$^{18}$$O, natural abundance of which is 0.205 %, was enriched to 60 %. Moreover, it was found that the enrichment factor increases with increasing the sample pressure, which was different from the infrared multiphoton dissociation of usual molecules. This phenomenon was discussed on the basis of a simulation by a rate equation model including a collisional vibrational relaxation.

Journal Articles

Effects of locally targeted heavy-ion and laser microbeam on root hydrotropism in ${it Arabidopsis thaliana}$

Miyazawa, Yutaka*; Sakashita, Tetsuya; Funayama, Tomoo; Hamada, Nobuyuki*; Negishi, Hiroshi*; Kobayashi, Akie*; Kaneyasu, Tomoko*; Oba, Atsushi*; Morohashi, Keita*; Kakizaki, Takehiko*; et al.

Journal of Radiation Research, 49(4), p.373 - 379, 2008/07

 Times Cited Count:24 Percentile:62.01(Biology)

We examined the role of root cap and elongation zone cells in root hydrotropism using heavy-ion and laser microbeam. Heavy-ion microbeam irradiation of the elongation zone, but not that of the columella cells, significantly and temporary suppressed the development of hydrotropic curvature. However, laser ablation confirmed that columella cells are indispensable for hydrotropism. Systemic heavy-ion broad-beam irradiation suppressed ${it de novo}$ expression of ${it INDOLE ACETIC ACID 5}$ gene, but not ${it MIZU-KUSSEI1}$ gene. Our results indicate that both the root cap and elongation zone have indispensable and functionally distinct roles in root hydrotropism, and that ${it de novo}$ gene expression might be required for hydrotropism in the elongation zone, but not in columella cells.

Journal Articles

Functional analysis of root elongation zone in hydrotropism in ${it Arabidopsis}$ using heavy-ion microbeam

Miyazawa, Yutaka*; Sakashita, Tetsuya; Negishi, Hiroshi*; Kobayashi, Akie*; Kaneyasu, Tomoko*; Oba, Atsushi*; Morohashi, Keita*; Kakizaki, Takehiko*; Funayama, Tomoo; Hamada, Nobuyuki*; et al.

JAEA-Review 2007-060, JAEA Takasaki Annual Report 2006, P. 116, 2008/03

We examined the role of root cap and elongation zone cells in root hydrotropism of ${it Arabidopsis thaliana}$ using heavy ion and laser microbeam. Heavy ion microbeam irradiation of the elongation zone, but not that of the columella cells, significantly and temporarily suppressed the development of hydrotropic curvature. However, laser ablation confirmed that columella cells are indispensable for hydrotropism. Systemic heavy ion broad beam irradiation suppressed de novo expression of INDOLE ACETIC ACID 5 gene. Our results indicate that both the root cap and elongation zone have indispensable and functionally distinct roles in root hydrotropism, and that de novo gene expression might be required for hydrotropism in the elongation zone, but not in columella cells.

Journal Articles

Local neutron transmutation doping using isotopically enriched silicon film

Yamada, Yoichi; Yamamoto, Hiroyuki; Oba, Hironori; Sasase, Masato*; Esaka, Fumitaka; Yamaguchi, Kenji; Udono, Haruhiko*; Shamoto, Shinichi; Yokoyama, Atsushi; Hojo, Kiichi

Journal of Physics and Chemistry of Solids, 68(11), p.2204 - 2208, 2007/11

 Times Cited Count:6 Percentile:33.03(Chemistry, Multidisciplinary)

$$^{30}$$Si in natural Si has been widely used for a doping source, since $$^{30}$$Si can be transmuted into $$^{31}$$P by thermal neutron (Neutron Transmutation Doping, NTD). NTD of nanostructure fabricated from $$^{30}$$Si-enriched materials can serve as a controlled local doping method with tunable dopant concentration, which cannot be realized by conventional doping methods such as ion implantation. In the present study, $$^{30}$$Si-enriched thin film has been fabricated in order to demonstrate the local NTD. The $$^{30}$$Si-enriched film with thickness of 100 nm was deposited on the Si(100) substrate by plasma enhanced chemical vapor deposition using $$^{30}$$Si-enriched SiF$$_{4}$$ as the source gases. The film contains 7.1 % of $$^{30}$$Si, which is twice higher than that of natural Si. Possible contaminant, fluorine, is lower than 0.6 at.% determined from X-ray photoelectron spectra. Nanostructure of films and changes of electronic properties by the neutron irradiation will also be discussed.

Journal Articles

Identification of the functional tissues for hydrotropism in comparison with those for gravitropism

Miyazawa, Yutaka*; Negishi, Hiroshi*; Sakashita, Tetsuya; Kobayashi, Akie*; Kaneyasu, Tomoko*; Oba, Atsushi*; Funayama, Tomoo; Wada, Seiichi*; Hamada, Nobuyuki*; Kakizaki, Takehiko; et al.

JAEA-Review 2006-042, JAEA Takasaki Annual Report 2005, P. 119, 2007/02

Journal Articles

Spectroscopic study of reaction mechanism of laser-ablated silicon ions and neutrals with benzene molecules

Saeki, Morihisa; Oba, Hironori; Yokoyama, Atsushi

Journal of Physics; Conference Series, 59, p.732 - 735, 2007/00

 Times Cited Count:0 Percentile:0

We have performed laser ablation of silicon in neon gas and benzene vapor. The reaction mechanism of the ablated silicon atoms with the neon atoms and benzene molecules were investigated by space- and time-resolved emission spectroscopy. The ablation in the neon gas suggested that (1) the neutral neon atoms are excited to 2pn states lying in 18-19 eV and (2) the neutral neon atoms are excited by electronic-to-electronic and translational-to-electronic energy transfer from the silicon ions. In the ablation in the benzene vapor, we found that the benzene molecules are decomposed into C2 and CH radicals by the collision with the silicon atoms.

Journal Articles

Laser ablation of silicon in neon gas; Study of excitation mechanism of neon neutrals by ablated silicon ions

Saeki, Morihisa; Hirata, Koichi*; Sakka, Tetsuo*; Oba, Hironori; Yokoyama, Atsushi

Journal of Applied Physics, 98(4), p.044912_1 - 044912_6, 2005/08

 Times Cited Count:3 Percentile:14.36(Physics, Applied)

no abstracts in English

Journal Articles

Diagnostics of pulsed plasma in laser ablation of boron compounds

Oba, Hironori; Saeki, Morihisa; Yokoyama, Atsushi

Proceedings of Plasma Science Symposium 2005/22nd Symposium on Plasma Processing (PSS-2005/SPP-22), p.331 - 332, 2005/01

A plasma produced by a XeCl laser ablation of boron compound was investigated using ion probes and a quadrupole mass spectrometer. Although the ablated neutral boron atoms had a natural abundance ratio, the isotope ratio of singly ionized boron atoms having a greatly different from the natural abundance ratio was observed. The observed isotope ratio of boron ions was different from the natural abundance.

Journal Articles

Silicon isotope separation utilizing infrared multiphoton dissociation of Si$$_{2}$$F$$_{6}$$ irradiated with two-frequency CO$$_{2}$$ laser lights

Yokoyama, Atsushi; Oba, Hironori; Hashimoto, Masashi; Katsumata, Keiichi; Akagi, Hiroshi; Ishii, Takeshi*; Oya, Akio*; Arai, Shigeyoshi*

Applied Physics B, 79(7), p.883 - 889, 2004/11

 Times Cited Count:9 Percentile:43.51(Optics)

Silicon isotope separation has been done utilizing the Infrared Multiphoton Dissociation of Si$$_{2}$$F$$_{6}$$ irradiated with two-frequency CO$$_{2}$$ laser lights. The two-frequency excitation method improved the separation efficiency with keeping the high enrichment factors. For example, Si$$_{2}$$F$$_{6}$$ with the $$^{28}$$Si fraction of 99.4 % was obtained at 40.0 % dissociation of Si$$_{2}$$F$$_{6}$$ after the simultaneous irradiation of 100 pulses with 966.23 cm$$^{-1}$$ photons (0.089 J/cm$$^{2}$$) and 954.55 cm$$^{-1}$$ photons (0.92 J/cm$$^{2}$$), while 1000 pulses were needed to obtain 99.0 % of $$^{28}$$Si at 27.2 % dissociation in the case of single frequency irradiation at 954.55 cm$$^{-1}$$ (0.92 J/cm$$^{2}$$). The single-step enrichment factors of $$^{29}$$Si and $$^{30}$$Si increased with increasing Si$$_{2}$$F$$_{6}$$ pressure. The reason for this enhancement has been discussed in terms of the rotational and vibrational relaxations by collisions with ambient gases.

Journal Articles

Beam-palarization asymmetries for the $$p$$($$overrightarrow{gamma}$$,$$K$$$$^{+}$$)$$Lambda$$ and $$p$$($$overrightarrow{gamma}$$,$$K$$$$^{+}$$)$$Sigma$$$$^{0}$$ reactions for $$E$$$$_{gamma}$$=1.5-2.4 GeV

Zegers, R. G. T.*; Sumihama, Mizuki*; Ahn, D. S.*; Ahn, J. K.*; Akimune, Hidetoshi*; Asano, Yoshihiro; Chang, W. C.*; Dat$'e$, S.*; Ejiri, Hiroyasu*; Fujimura, Hisako*; et al.

Physical Review Letters, 91(9), p.092001_1 - 092001_4, 2003/08

 Times Cited Count:127 Percentile:95.25(Physics, Multidisciplinary)

no abstracts in English

Journal Articles

Evidence for a narrow $$S$$ = +1 Baryon resonance in photoproduction from the neutron

Nakano, Takashi*; Ahn, D. S.*; Ahn, J. K.*; Akimune, Hidetoshi*; Asano, Yoshihiro; Chang, W. C.*; Date, S.*; Ejiri, Hiroyasu*; Fujimura, Hisako*; Fujiwara, Mamoru; et al.

Physical Review Letters, 91(1), p.012002_1 - 012002_4, 2003/07

 Times Cited Count:994 Percentile:99.88(Physics, Multidisciplinary)

no abstracts in English

57 (Records 1-20 displayed on this page)