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Journal Articles

Durability of secondary electron emission for high-intensity beam on SiC wire

Meigo, Shinichiro; Nakano, Keita; Okubo, Nariaki; Yuyama, Takahiro*; Ishii, Yasuyuki*

Proceedings of 18th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.296 - 301, 2021/10

no abstracts in English

Journal Articles

Diffusion of tritiated water, $$^{137}$$Cs$$^{+}$$, and $$^{125}$$I$$^{-}$$ in compacted Ca-montmorillonite; Experimental and modeling approaches

Fukatsu, Yuta; Yotsuji, Kenji*; Okubo, Takahiro*; Tachi, Yukio

Applied Clay Science, 211, p.106176_1 - 106176_10, 2021/09

 Times Cited Count:1 Percentile:76.68(Chemistry, Physical)

Journal Articles

Pore distribution of compacted Ca-montmorillonite using NMR relaxometry and cryoporometry; Comparison with Na-montmorillonite

Okubo, Takahiro*; Yamazaki, Akio*; Fukatsu, Yuta; Tachi, Yukio

Microporous and Mesoporous Materials, 313, p.110841_1 - 110841_11, 2021/01

 Times Cited Count:1 Percentile:69.4(Chemistry, Applied)

Pore distributions in water-saturated Ca-montmorillonite were investigated using $$^{1}$$H NMR measurements under various dry densities (0.8 - 1.6 g/cm$$^{3}$$) and porewater salinity conditions (deionized water, 0.1 and 1 M CaCl$$_{2}$$), at the temperature range of 233 - 303 K. The volume fractions of the interlayer pore including two and three hydrated layers and the non-interlayer pore in compacted Ca-montmorillonite were quantified by NMR relaxometry including $$T1$$ and $$T1/T2$$ distribution analysis, and were compared with NMR cryoporometry and X-ray diffractometry. These analysis provided consistent pictures on the pore distributions in compacted Ca-montmorillonite, in contrast to Na-montmorillonite. The main factor affecting the pore distribution in compacted Ca- and Na-montmorillonite is the density, whereas the effect of porewater salinity is relatively smaller. The effect of interlayer cations is also relatively smaller at higher density, although the differences in the pore structures are significant at low density.

Journal Articles

New insights into the Cs adsorption on montmorillonite clay from $$^{133}$$Cs solid-state NMR and density functional theory calculations

Okubo, Takahiro*; Okamoto, Takuya*; Kawamura, Katsuyuki*; Gu$'e$gan, R.*; Deguchi, Kenzo*; Oki, Shinobu*; Shimizu, Tadashi*; Tachi, Yukio; Iwadate, Yasuhiko*

Journal of Physical Chemistry A, 122(48), p.9326 - 9337, 2018/12

 Times Cited Count:6 Percentile:45.29(Chemistry, Physical)

The structures of Cs adsorption on montmorillonite were investigated by the nuclear magnetic resonance (NMR) spectroscopy. The NMR spectra of Cs adsorbed on montmorillonite samples were measured under different Cs contents and relative humidity levels. NMR parameters were evaluated by the first principle calculations in order to identify the relationship between adsorbed Cs structures and NMR parameters. The comparisons between experimental and theoretical NMR spectra revealed that Cs is preferentially adsorbed at sites near Al for low Cs substituted montmorillonites, and that non-hydrated Cs present in partially Cs substituted samples, even after being hydrated under high relative humidity.

Journal Articles

Diffusion model considering multiple pore structures in compacted bentonite

Yotsuji, Kenji; Tachi, Yukio; Okubo, Takahiro*

CMS Workshop Lectures, Vol.21, p.251 - 257, 2016/06

We have developed integrated sorption and diffusion model (ISD model) for assessment of diffusion parameters consistent with sorption processes in compacted bentonite. The ISD model gives consistent consideration to porewater chemistry, sorption and diffusion processes in compacted bentonite. The diffusion component based on the electric double layer theory and the homogeneous pore model in the ISD model accounts consistently for cation De overestimation and anion exclusion in narrow pores. The current ISD model can quantitatively account for diffusion of monovalent cations and anions, however, the model predictions disagree with diffusion data for multivalent cation and complex species. To improve the applicability of the model, it is necessary to consider the atomic level interactions between solute, solvent or clay mineral, and try that we apply the current ISD model to heterogeneous pore structure. In this study we try the application of the current ISD model to multiple pore structure. As results of numerical analysis of these models, the salinity dependence of effective diffusivity for the multi-pore model is comparatively smaller than that for the homogeneous pore model and the current diffusion model is improved.

Journal Articles

Pore distribution of water-saturated compacted clay using NMR relaxometry and freezing temperature depression; Effects of density and salt concentration

Okubo, Takahiro*; Ibaraki, Moe*; Tachi, Yukio; Iwadate, Yasuhiko*

Applied Clay Science, 123, p.148 - 155, 2016/04

 Times Cited Count:19 Percentile:73.19(Chemistry, Physical)

The pore distribution of water-saturated compacted clay (Na-montmorillonite at 0.8 and 1.4 g/cm$$^{3}$$ saturated by three salt concentrations) was evaluated using $$^{1}$$H NMR relaxometry and freezing point depression. The populations of interlayer water with four hydrated state and non-interlayer water were calculated from the assumed thresholds. The sample with lower density exhibits higher population of non-interlayer water up to 55%. Low-temperature $$^{1}$$H NMR experiments in view of freezing point depression indicated that mesopore water in approximately 4 nm space observed in the calorimetric study was considered as non-interlayer water and the threshold temperature. The result showed that population of non-interlayer water by expected from freezing point depression agreed with $$^{1}$$H NMR relaxometry within 10%. Correlation experiments between longitudinal ($$T_{1}$$) and transverse relation times ($$T_{2}$$) at -10$$^{circ}$$C suggested that high-mobility bulk-like water molecules existed at a clay density of 1.4 g/cm$$^{3}$$.

JAEA Reports

Light ion microbeam analysis / processing system and its improvement

Koka, Masashi; Ishii, Yasuyuki; Yamada, Naoto; Okubo, Takeru; Kada, Wataru*; Kitamura, Akane; Iwata, Yoshihiro*; Kamiya, Tomihiro; Sato, Takahiro

JAEA-Technology 2016-006, 41 Pages, 2016/03

JAEA-Technology-2016-006.pdf:14.03MB

A MeV-class light ion microbeam system has been developed for micro-analysis and micro-fabrication with high spatial resolution at 3-MV single-ended accelerator in Takasaki Ion Accelerators for Advanced Radiation Application of Takasaki Advanced Radiation Research Institute, Sector of Nuclear Science Research, Japan Atomic Energy Agency. This report describes the technical improvements for the main apparatus (the accelerator, beam-transport lines, and microbeam system), and auxiliary equipments/ parts for ion beam applications such as Particle Induced X-ray/Gamma-ray Emission (PIXE/PIGE) analysis, 3-D element distribution analysis using PIXE-Computed Tomography(CT), Ion Beam-Induced Luminescence (IBIL) analysis, and Proton Beam Writing with the microbeam scanning, with functional outline of these apparatus and equipments/parts.

Journal Articles

Particle induced X-ray emission-computed tomography analysis of an adsorbent for extraction chromatography

Sato, Takahiro; Yokoyama, Akihito; Kitamura, Akane; Okubo, Takeru; Ishii, Yasuyuki; Takahatake, Yoko; Watanabe, So; Koma, Yoshikazu; Kada, Wataru*

Nuclear Instruments and Methods in Physics Research B, 371, p.419 - 423, 2016/03

 Times Cited Count:4 Percentile:45.9(Instruments & Instrumentation)

Journal Articles

Radiation response of silicon carbide metal-oxide-semiconductor transistors in high dose region

Oshima, Takeshi; Yokoseki, Takashi; Murata, Koichi; Matsuda, Takuma; Mitomo, Satoshi; Abe, Hiroshi; Makino, Takahiro; Onoda, Shinobu; Hijikata, Yasuto*; Tanaka, Yuki*; et al.

Japanese Journal of Applied Physics, 55(1S), p.01AD01_1 - 01AD01_4, 2016/01

 Times Cited Count:10 Percentile:49.94(Physics, Applied)

Journal Articles

Current status of electrostatic accelerator at TIARA

Usui, Aya; Chiba, Atsuya; Yamada, Keisuke; Yokoyama, Akihito; Kitano, Toshihiko*; Takayama, Terumitsu*; Orimo, Takao*; Kanai, Shinji*; Aoki, Yuki*; Hashizume, Masashi*; et al.

Dai-28-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.117 - 119, 2015/12

no abstracts in English

Journal Articles

A Development of super radiation-hardened power electronics using silicon carbide semiconductors; Toward MGy-class radiation resistivity

Hijikata, Yasuto*; Mitomo, Satoshi*; Matsuda, Takuma*; Murata, Koichi*; Yokoseki, Takashi*; Makino, Takahiro; Takeyama, Akinori; Onoda, Shinobu; Okubo, Shuichi*; Tanaka, Yuki*; et al.

Proceedings of 11th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-11) (Internet), p.130 - 133, 2015/11

Journal Articles

Present status of TIARA at JAEA

Yuyama, Takahiro; Ishibori, Ikuo; Kurashima, Satoshi; Yoshida, Kenichi; Ishizaka, Tomohisa; Chiba, Atsuya; Yamada, Keisuke; Yokoyama, Akihito; Usui, Aya; Miyawaki, Nobumasa; et al.

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.302 - 304, 2015/09

no abstracts in English

Journal Articles

Current status of electrostatic accelerators at TIARA

Usui, Aya; Uno, Sadanori; Chiba, Atsuya; Yamada, Keisuke; Yokoyama, Akihito; Kitano, Toshihiko*; Takayama, Terumitsu*; Orimo, Takao*; Kanai, Shinji*; Aoki, Yuki*; et al.

Dai-27-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.118 - 121, 2015/03

no abstracts in English

Journal Articles

Status report on technical developments of electrostatic accelerators

Yamada, Keisuke; Saito, Yuichi; Ishii, Yasuyuki; Matoba, Shiro; Chiba, Atsuya; Yokoyama, Akihito; Usui, Aya; Sato, Takahiro; Okubo, Takeru; Uno, Sadanori

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 159, 2014/03

no abstracts in English

Journal Articles

Operation of electrostatic accelerators

Uno, Sadanori; Chiba, Atsuya; Yamada, Keisuke; Yokoyama, Akihito; Usui, Aya; Saito, Yuichi; Ishii, Yasuyuki; Sato, Takahiro; Okubo, Takeru; Nara, Takayuki; et al.

JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 179, 2014/03

Three electrostatic accelerators at TIARA were operated on schedule in fiscal year 2012 except changing its schedule by cancellations of users. The yearly operation time of the 3 MV tandem accelerator, the 400 kV ion implanter and the 3MV single-ended accelerator were in the same levels as the ordinary one, whose operation time totaled to 2,073, 1,847 and 2,389 hours, respectively. The tandem accelerator had no trouble, whereas the ion implanter and the single-ended accelerator stopped by any troubles for one day and four days, respectively. The molecular ion beam of helium hydride was generated by the ion implanter, because the users required irradiation of several cluster ions in order to study the effect of irradiation. As a result, its intensity of beam was 50 nA at 200 kV. The ion beam of tungsten (W) at 15 MeV was accelerated by the tandem accelerator, whose intensity was 20 nA at charge state of 4+, because of the request from a researcher in the field of nuclear fusion.

Journal Articles

Current status of electrostatic accelerators at TIARA

Uno, Sadanori; Chiba, Atsuya; Yamada, Keisuke; Yokoyama, Akihito; Usui, Aya; Kitano, Toshihiko*; Takayama, Terumitsu*; Orimo, Takao*; Kanai, Shinji*; Aoki, Yuki*; et al.

Dai-26-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.79 - 81, 2013/07

Three electrostatic accelerators at TIARA were operated on schedule in fiscal year 2012 except changing its schedule by cancellations of users. The yearly operation time of the 3MV tandem accelerator, the 400 kV ion implanter and the 3 MV single-ended accelerator were in the same levels as the ordinary one, whose operation time totaled to 2,073, 1,847 and 2,389 hours, respectively. The tandem accelerator had no trouble, whereas the ion implanter and the single-ended accelerator stopped by any troubles for one day and four days, respectively. The ion implanter generated molecular ion beam of helium hydride by using the Freeman type ion source, because of the request from the user. As a result, its intensity of beam was 50 nA at 200 kV.

Journal Articles

Micromachining of commodity plastics by proton beam writing and fabrication of spatial resolution test-chart for neutron radiography

Sakai, Takuro; Yasuda, Ryo; Iikura, Hiroshi; Nojima, Takehiro; Matsubayashi, Masahito; Kada, Wataru; Koka, Masashi; Sato, Takahiro; Okubo, Takeru; Ishii, Yasuyuki; et al.

Nuclear Instruments and Methods in Physics Research B, 306, p.299 - 301, 2013/07

 Times Cited Count:7 Percentile:54.8(Instruments & Instrumentation)

Journal Articles

Development of beam generation and irradiation technology for electrostatic accelerators

Yamada, Keisuke; Chiba, Atsuya; Yokoyama, Akihito; Saito, Yuichi; Ishii, Yasuyuki; Sato, Takahiro; Okubo, Takeru; Uno, Sadanori

JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 155, 2013/01

no abstracts in English

Journal Articles

Operation of electrostatic accelerators

Uno, Sadanori; Chiba, Atsuya; Yamada, Keisuke; Yokoyama, Akihito; Saito, Yuichi; Ishii, Yasuyuki; Sato, Takahiro; Okubo, Takeru; Nara, Takayuki; Kitano, Toshihiko*; et al.

JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 173, 2013/01

The three electrostatic accelerators at the TIARA had no mechanical damage when the Tohoku earthquake happened on March 11, 2011. But, they could not be operated during April, due to the influence of planned power outage by TEPCO. These accelerators additionally operated on Saturday for ten days in order to compensate for the lost experiment time. As a result, the yearly operation time had kept the same level as the ordinary one. The ion beam of erbium (Er) with 11.7MeV was accelerated newly by the tandem accelerator, whose intensity was 20nA at charge state of 3+. The sequential generation/irradiation of two different kinds of fullerene ions was achieved at the ion implanter by a mixed powder method without exchange of the Freeman type ion source by the user's request.

Journal Articles

Mach-Zehnder polymer waveguides fabricated using proton beam writing

Miura, Kenta*; Sato, Takahiro; Ishii, Yasuyuki; Koka, Masashi; Kiryu, Hiromu*; Ozawa, Yusuke*; Takano, Katsuyoshi*; Okubo, Takeru; Yamazaki, Akiyoshi; Kada, Wataru; et al.

JAEA-Review 2012-046, JAEA Takasaki Annual Report 2011, P. 126, 2013/01

131 (Records 1-20 displayed on this page)