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ceramicsVauchy, R.; Hirooka, Shun; Watanabe, Masashi; Yokoyama, Keisuke; Sunaoshi, Takeo*; Yamada, Tadahisa*; Nakamichi, Shinya; Murakami, Tatsutoshi
Ceramics International, 49(2), p.3058 - 3065, 2023/01
Times Cited Count：2 Percentile：41.9(Materials Science, Ceramics)Amekura, Hiroshi*; Toulemonde, M.*; Narumi, Kazumasa*; Li, R.*; Chiba, Atsuya*; Hirano, Yoshimi*; Yamada, Keisuke*; Yamamoto, Shunya*; Ishikawa, Norito; Okubo, Nariaki; et al.
Scientific Reports (Internet), 11(1), p.185_1 - 185_11, 2021/01
Times Cited Count：10 Percentile：80.51(Multidisciplinary Sciences)We report the track formation of 10 nm in diameter in silicon irradiated with 6 MeV C
, i.e., much lower energy than the previously reported energy threshold.
Hamamoto, Takafumi*; Shibutani, Sanae*; Ishida, Keisuke*; Fujisaki, Kiyoshi*; Yamada, Motoyuki*; Tachi, Yukio
Proceedings of 6th East Asia Forum on Radwaste Management Conference (EAFORM 2017) (Internet), 6 Pages, 2017/12
NUMO has developed a generic safety case to demonstrate the feasibility and safety of geological disposal of HLW and TRU in Japan and to provide a basic structure for the safety case which will be applicable to any potential site. In this safety case, the safety assessment was carried out for the repositories tailored to site descriptive models developed for three representative rock groups (plutonic, Neogene sedimentary and Pre-Neogene sedimentary rocks). Radionuclide migration parameters in rocks, i.e. distribution coefficients (Kds) and effective diffusion coefficients (Des), were derived to allow safety analysis for a range of scenarios. In this generic stage, the values of these parameter were given as the statistical values derived from laboratory data for certain rock types. The data were extracted from the latest database, with interpretation based on radionuclide speciation derived from relevant groundwater thermodynamic modelings.
ion production by electron attachment using cesium sputter ion sourceUsui, Aya; Chiba, Atsuya; Yamada, Keisuke
JAEA-Technology 2016-034, 21 Pages, 2017/03
JAEA-Technology-2016-034.pdf:82.52MB
In the TIARA (Takasaki Ion Accelerators for Advanced Radiation Application), in order to propel the studies on the swift cluster ions, a novel technique was developed to increase the beam intensity of the fullerene ions which would have a considerably larger irradiation effect than any cluster ions. As a new method of negative ion production, the ionization mechanism by electron attachment was introduced as an alternative to the traditional method with the cesium sputtering to the existing cesium sputter type ion source (SNICS). In consequence, the intensity of the negative C ion beam produced using an existing ion source with a novel technique was increased thousand times as high as those using the previous one for 12 hour operation. In this report, we describe the problems in the traditional ionization method and explain the production technique of the negative C ions ionized via electron attachment process, which solves that only by the minor changes in SNICS.
Shimizu, Kenichi*; Koike, Yuki*; Yamada, Taiki*; Oharada, Kazuya*; Tanaka, Keisuke*; Shobu, Takahisa
Zairyo, 65(9), p.657 - 664, 2016/09
The internal stress in crystalline thermoplastics, polyphenylene sulphide (PPS), reinforced by carbon fibers of 30 mass% was measured by the diffraction method using synchrotron with energy of 12.3 keV. The stress in the matrix was determined by the sin2psi method with side-inclination optics of transmitted X-ray diffractions. Using skin-layer strips cut parallel, perpendicular and 45 degree to the molding direction of the injection molded plates, the matrix stress was measured under the uniaxial applied stress. The experimental values were at least qualitatively agreed with the prediction derived based on micromechanics. The quantitative difference between experiment and prediction is mainly due to the neglect of the distribution of fiber orientations in the micromechanics prediction. These residual stresses were caused by the mismatch of the thermal expansion coefficient between matrix and fibers.
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
Chiba, Atsuya; Usui, Aya; Yamada, Keisuke
Dai-28-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.53 - 56, 2015/12
no abstracts in English
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
Chiba, Atsuya; Usui, Aya; Yamada, Keisuke
Dai-27-Kai Tandemu Kasokuki Oyobi Sono Shuhen Gijutsu No Kenkyukai Hokokushu, p.56 - 59, 2015/03
Utilization of the swift fullerene ion beam in TIARA using the tandem accelerator tends to increase year after year. However, only a few currents obtained by a generating method of negative ions with a cesium sputtering is hindrance to the progress of study. A generating method of the negative fullerene ions is developed on the basis of an electron attachment. As a result, the method permits us to obtain stable beam intensity more than a thousand-fold compared with that produced by the sputtering method.
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
O
Tomiyasu, Keisuke*; Iwasa, Kazuaki*; Ueda, Hiroaki*; Niitaka, Seiji*; Takagi, Hidenori*; Kawamura, Seiko; Kikuchi, Tatsuya; Inamura, Yasuhiro; Nakajima, Kenji; Yamada, Kazuyoshi*
Physical Review Letters, 113(23), p.236402_1 - 236402_5, 2014/12
Times Cited Count：14 Percentile：66.88(Physics, Multidisciplinary)Spin fluctuations were studied over a wide momentum (
) and energy (
) space in the frustrated 
-electron heavy-fermion metal LiVO by time-of-flight inelastic neutron scattering. We observed the overall 
evolutions near the characteristic 
= 0.6 
peak and found another weak broad magnetic peak around 2.4 . The data are described by a simple response function, a partially delocalized magnetic form factor, and antiferromagnetic short-range spatial correlations, indicating that heavy-fermion formation is attributable to spin-orbit fluctuations with orbital hybridization.
Chiba, Atsuya; Narumi, Kazumasa; Yamada, Keisuke; Matoba, Shiro; Saito, Yuichi
JAEA-Review 2013-059, JAEA Takasaki Annual Report 2012, P. 167, 2014/03
Coulomb explosion caused in an early phase affects the subsequent process significantly in the interaction of a swift cluster ion with a material, so it is considered that the Coulomb explosion is one of the most important phenomena on understanding the mechanisms of the irradiation effects on the cluster ion bombardment. In experiments, charge states and spatial distributions of C
constituent ions dissociated by the collision with an atom in a gas target were measured on the event-by-event basis. After the trajectory analysis of the constituent ions using a simulation model, it turned out that the interatomic distance of the constituent ions grows approximately 1.5 times as long as the ground state, before they dissociate.
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
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.
Takahashi, Nobuaki*; Murata, Hirohiko*; Mitsubori, Hitoshi*; Sakuraba, Junji*; Soga, Tomohiro*; Aoki, Yasushi*; Kato, Takanori*; Saito, Yuichi; Yamada, Keisuke; Ikenaga, Noriaki*; et al.
Review of Scientific Instruments, 85(2), p.02C306_1 - 02C306_3, 2014/02
Times Cited Count：2 Percentile：11.84(Instruments & Instrumentation)Yamada, Keisuke; Saito, Yuichi; Yokota, Wataru
Review of Scientific Instruments, 85(2), p.02A920_1 - 02A920_3, 2014/02
Times Cited Count：1 Percentile：6.11(Instruments & Instrumentation)Yamada, Katsunori; Fujii, Katsutoshi; Kanda, Hiroshi; Higashi, Daisuke; Kobayashi, Toshiaki; Nakagawa, Masahiro; Fukami, Tomoyo; Yoshida, Keisuke; Ueno, Yumi; Nakajima, Junya; et al.
JAEA-Review 2013-033, 51 Pages, 2013/12
JAEA-Review-2013-033.pdf:2.73MB
After the accident at Fukushima Dai-ichi Nuclear Power Plant, various numerical criteria relevant to radiation protection were defined. We surveyed these criteria through internet. As a result of survey, the following 13 items were identified: (1) criteria for taking stable iodine tablets, (2) criteria for the screening of surface contamination, (3) evacuation area, sheltering area, etc., (4) activity concentrations in food, drinking water, etc., (5) dose limit for radiation workers engaged in emergency work, (6) guideline levels of radioactive substances in bathing areas, (7) criteria for use of school buildings and schoolyards, (8) restriction on planting rice, (9) acceptable activity concentrations in feedstuff, (10) acceptable activity concentrations in compost, (11) criteria for export containers and ships, (12) criteria for contaminated waste, (13) standards for radiation workers engaged in decontamination work. In this report, the basis of and issues on these criteria are summarized.
Chiba, Atsuya; Saito, Yuichi; Narumi, Kazumasa; Yamada, Keisuke; Kaneko, Toshiaki*
Nuclear Instruments and Methods in Physics Research B, 315, p.81 - 84, 2013/11
Times Cited Count：1 Percentile：11.98(Instruments & Instrumentation)The average charge of the constituent ions resulting from foil-induced dissociation of cluster ion is smaller than that of the single ion passing through the foil at same speed. This charge reduction effect is one of the most important phenomena for understanding the interaction of cluster ions with electrons in a solid, and the theories suggested that it strongly depends on the internuclear distance of the constituent ions. However, the relationship between the internuclear distance and the charge state has still not been shown quantitatively. We developed a method to evaluate the relationship by analyzing the divergence angle of the constituent ions after foil penetration using Coulomb explosion imaging technique. As a result for 6-MeV C, it was shown quantitatively that the charge reduction effect decreases with increasing the internuclear distance of the constituent ion in the solid.
Hirata, Koichi*; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Narumi, Kazumasa
Nuclear Instruments and Methods in Physics Research B, 314, p.39 - 42, 2013/11
Times Cited Count：4 Percentile：34.1(Instruments & Instrumentation) ions through micro- and nano-capillariesTsuchida, Hidetsugu*; Majima, Takuya*; Tomita, Shigeo*; Sasa, Kimikazu*; Narumi, Kazumasa; Saito, Yuichi; Chiba, Atsuya; Yamada, Keisuke; Hirata, Koichi*; Shibata, Hiromi*; et al.
Nuclear Instruments and Methods in Physics Research B, 315, p.336 - 340, 2013/11
Times Cited Count：3 Percentile：27.62(Instruments & Instrumentation)