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Amekura, Hiroshi*; Chettah, A.*; Narumi, Kazumasa*; Chiba, Atsuya*; Hirano, Yoshimi*; Yamada, Keisuke*; Yamamoto, Shunya*; Leino, A. A.*; Djurabekova, F.*; Nordlund, K.*; et al.
Nature Communications (Internet), 15, p.1786_1 - 1786_10, 2024/02
Injecting high-energy heavy ions in the electronic stopping regime into solids can create cylindrical damage zones called latent ion tracks. Although these tracks form in many materials, none have ever been observed in diamond, even when irradiated with high-energy GeV uranium ions. Here we report the first observation of ion track formation in diamond irradiated with 2-9 MeV C fullerene ions. Depending on the ion energy, the mean track length (diameter) changed from 17 (3.2) nm to 52 (7.1) nm. High resolution scanning transmission electron microscopy (HR-STEM) indicated the amorphization in the tracks, in which -bonding signal from graphite was detected by the electron energy loss spectroscopy (EELS).
Sanada, Yukihisa; Abe, Tomohisa; Sasaki, Miyuki; Kanno, Marina*; Yamada, Tsutomu*; Nakasone, Takamasa*; Miyazaki, Nobuyuki*; Oshikiri, Keisuke*; Watabe, Hiroshi*
Journal of Nuclear Science and Technology, 10 Pages, 2023/00
The "treated water" from which the main radioactive materials were removed contains tritium, and stakeholders in Japan have been debating how to treat it. The amount of treated water stored in the facility has reached its limit, and the Japanese government has decided that the treatment method will be to discharge the water into the ocean by FY 2023 (FY: Fiscal Year). The present research developed a simple and practical tritium monitor for the Fukushima Daiichi Nuclear Power Station (FDNPS) tritiated water release. A simple and practical tritium monitor was developed for FDNPS tritiated water release based on thin plastic scintillator sheets. The developed devices were calibrated using standard tritium solutions and a method for calculating the minimum detectable activity. Fifteen 0.25 mm-thick scintillators can be placed in the 0.26 L flow cell where the sample water is fed, yielding an active surface area of 3,200 mm. The efficiency of tritiated water with full water is 0.000035 cps Bq. The minimum detectable activity under simple shielding conditions was 7,800 Bq L (Measurement time was 3,600 s).
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:75.98(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.
Usui, Aya; Chiba, Atsuya; Yamada, Keisuke
JAEA-Technology 2016-034, 21 Pages, 2017/03
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.
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
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:11.31(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:5.83(Instruments & Instrumentation)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:11.56(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:33.13(Instruments & Instrumentation)Tsuchida, 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:26.8(Instruments & Instrumentation)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.
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
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.