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

https://doi.org/10.1016/j.nima.2016.06.127

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 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 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.

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

https://doi.org/10.1007/s00340-011-4630-0

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 O (D(O)) and enrichment factor (S) were obtained to be 1.610 /pulse and 316 respectively by the simultaneous irradiation with 1052.2 cm photons at 0.45 J/cm and 1031.5 cm photons at 1.06 J/cm. These are comparable with D(O) = 2.210 /pulse and S = 391 obtained by the single-frequency irradiation of 1033.5 cm photons at 2.2 J/cm. Therefore, the production rate of an 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.

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

Effects of ionizing radiation on locomotory behavior and mechanosensation in

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

https://doi.org/10.1269/jrr.08087

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

https://doi.org/10.1143/JJAP.47.8379

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

Effects of locally targeted heavy-ion and laser microbeam on root hydrotropism in

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

https://doi.org/10.1269/jrr.07131

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 expression of gene, but not gene. Our results indicate that both the root cap and elongation zone have indispensable and functionally distinct roles in root hydrotropism, and that gene expression might be required for hydrotropism in the elongation zone, but not in columella cells.

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

https://doi.org/10.1016/j.jpcs.2007.08.056

Si in natural Si has been widely used for a doping source, since Si can be transmuted into P by thermal neutron (Neutron Transmutation Doping, NTD). NTD of nanostructure fabricated from 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, Si-enriched thin film has been fabricated in order to demonstrate the local NTD. The Si-enriched film with thickness of 100 nm was deposited on the Si(100) substrate by plasma enhanced chemical vapor deposition using Si-enriched SiF as the source gases. The film contains 7.1 % of 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.

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

https://doi.org/10.1088/1742-6596/59/1/156

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.

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.

Beam-palarization asymmetries for the (,) and (,) reactions for =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, S.*; Ejiri, Hiroyasu*; Fujimura, Hisako*; et al.

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

https://doi.org/10.1103/PhysRevLett.91.092001

no abstracts in English