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Journal Articles

Design for detecting recycling muon after muon-catalyzed fusion reaction in solid hydrogen isotope target

Okutsu, Kenichi*; Yamashita, Takuma*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.

Fusion Engineering and Design, 170, p.112712_1 - 112712_4, 2021/09

A muonic molecule which consists of two hydrogen isotope nuclei (deuteron (d) or tritium (t)) and a muon decays immediately via nuclear fusion and the muon will be released as a recycling muon, and start to find another hydrogen isotope nucleus. The reaction cycle continues until the muon ends up its lifetime of 2.2 $$mu$$s. Since the muon does not participate in the nuclear reaction, the reaction is so called a muon catalyzed fusion ($$mu$$CF). The recycling muon has a particular kinetic energy (KE) of the muon molecular orbital when the nuclear reaction occurs. Since the KE is based on the unified atom limit where distance between two nuclei is zero. A precise few-body calculation estimating KE distribution (KED) is also in progress, which could be compared with the experimental results. In the present work, we observed recycling muons after $$mu$$CF reaction.

Journal Articles

Time evolution calculation of muon catalysed fusion; Emission of recycling muons from a two-layer hydrogen film

Yamashita, Takuma*; Okutsu, Kenichi*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.

Fusion Engineering and Design, 169, p.112580_1 - 112580_5, 2021/08

A muon ($$mu$$) having 207 times larger mass of electron and the same charge as the electron has been known to catalyze a nuclear fusion between deuteron (d) and triton (t). These two nuclei are bound by $$mu$$ and form a muonic hydrogen molecular ion, dt$$mu$$. Due to the short inter-nuclear distance of dt$$mu$$, the nuclear fusion, d +t$$rightarrow alpha$$ + n + 17.6 MeV, occurs inside the molecule. This reaction is called muon catalyzed fusion ($$mu$$CF). Recently, the interest on $$mu$$CF is renewed from the viewpoint of applications, such as a source of high-resolution muon beam and mono-energetic neutron beam. In this work, we report a time evolution calculation of $$mu$$CF in a two-layered hydrogen isotope target.

Journal Articles

Rapid analysis of $$^{90}$$Sr in cattle bone and tooth samples by inductively coupled plasma mass spectrometry

Koarai, Kazuma; Matsueda, Makoto; Aoki, Jo; Yanagisawa, Kayo*; Terashima, Motoki; Fujiwara, Kenso; Kino, Yasushi*; Oka, Toshitaka; Takahashi, Atsushi*; Suzuki, Toshihiko*; et al.

Journal of Analytical Atomic Spectrometry, 36(8), p.1678 - 1682, 2021/08

 Times Cited Count:0 Percentile:0.02(Chemistry, Analytical)

Rapid analysis of $$^{90}$$Sr in bone and tooth samples of cattle were achieved by an inductively coupled plasma mass spectrometry (ICP-MS) coupled with mass shift and solid phase extraction techniques. Limit of detection (LOD) in the ICP-MS measurement of 0.1 g samples was lower than that of the radioactivity measurement. Analytical time of the ICP-MS method was reduced from 20 days to 11 hours, compared with the radiometric method. Therefore, the ICP-MS method can be rapid and useful procedure of $$^{90}$$Sr in small bone and tooth samples derived from terrestrial animals.

Journal Articles

Radioactivity and radionuclides in deciduous teeth formed before the Fukushima-Daiichi Nuclear Power Plant accident

Takahashi, Atsushi*; Chiba, Mirei*; Tanahara, Akira*; Aida, Jun*; Shimizu, Yoshinaka*; Suzuki, Toshihiko*; Murakami, Shinobu*; Koarai, Kazuma; Ono, Takumi*; Oka, Toshitaka; et al.

Scientific Reports (Internet), 11(1), p.10355_1 - 10355_11, 2021/05

 Times Cited Count:1 Percentile:65.97(Multidisciplinary Sciences)

Journal Articles

Morphological reproductive characteristics of testes and fertilization capacity of cryopreserved sperm after the Fukushima accident in raccoon (${it Procyon lotor}$)

Komatsu, Kazuki*; Iwasaki, Tsugumi*; Murata, Kosuke*; Yamashiro, Hideaki*; Goh, V. S. T.*; Nakayama, Ryo*; Fujishima, Yohei*; Ono, Takumi*; Kino, Yasushi*; Shimizu, Yoshinaka*; et al.

Reproduction in Domestic Animals, 56(3), p.484 - 497, 2021/03

We have established an archive system of livestock and wild animals from the surrounding ex-evacuation zone. Wildlife within the alert zone have been exposed to low-dose-rate (LDR) radiation for a long and continuous time. In this study, we analysed the morphological characteristics of the testes and in vitro fertilization (IVF) capacity of cryopreserved sperm of raccoons from the ex-evacuation zone of the FDNPP accident. This study revealed that the chronic and LDR radiation exposure associated with the FDNPP accident had no adverse effect on the reproductive characteristics and functions of male raccoons.

Journal Articles

External exposure dose estimation by electron spin resonance technique for wild Japanese macaque captured in Fukushima Prefecture

Oka, Toshitaka; Takahashi, Atsushi*; Koarai, Kazuma; Mitsuyasu, Yusuke*; Kino, Yasushi*; Sekine, Tsutomu*; Shimizu, Yoshinaka*; Chiba, Mirei*; Suzuki, Toshihiko*; Osaka, Ken*; et al.

Radiation Measurements, 134, p.106315_1 - 106315_4, 2020/06

 Times Cited Count:1 Percentile:39.17(Nuclear Science & Technology)

The relationship between the CO$$_{2}$$ radical intensity and the absorbed dose (dose response curve) of tooth enamel of Japanese macaque was observed by electron spin resonance and the detection limit of our system was estimated to be 33.5 mGy, which is comparable to the detection limit for human molar teeth. Using the dose response curve, external exposure dose for seven wild Japanese macaques captured in Fukushima prefecture were examined. The results suggest that the external exposure dose for the wild Japanese macaques were ranged between 45 mGy to 300 mGy.

Journal Articles

Achievement of 500 keV negative ion beam acceleration on JT-60U negative-ion-based neutral beam injector

Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.

Nuclear Fusion, 51(8), p.083049_1 - 083049_8, 2011/08

 Times Cited Count:42 Percentile:88.1(Physics, Fluids & Plasmas)

Hydrogen negative ion beams of 490 keV, 3 A and 510 keV, 1 A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of 2 m$$^{2}$$ for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m$$^{2}$$). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60SA and ITER.

Journal Articles

Demonstration of 500 keV beam acceleration on JT-60 negative-ion-based neutral beam injector

Kojima, Atsushi; Hanada, Masaya; Tanaka, Yutaka*; Kawai, Mikito*; Akino, Noboru; Kazawa, Minoru; Komata, Masao; Mogaki, Kazuhiko; Usui, Katsutomi; Sasaki, Shunichi; et al.

Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03

Hydrogen negative ion beams of 490keV, 3A and 510 keV, 1A have been successfully produced in the JT-60 negative ion source with three acceleration stages. These successful productions of the high-energy beams at high current have been achieved by overcoming the most critical issue, i.e., a poor voltage holding of the large negative ion sources with the grids of $$sim$$ 2 m$$^{2}$$ for JT-60SA and ITER. To improve voltage holding capability, the breakdown voltages for the large grids was examined for the first time. It was found that a vacuum insulation distance for the large grids was 6-7 times longer than that for the small-area grid (0.02 m$$^{2}$$). From this result, the gap lengths between the grids were tuned in the JT-60 negative ion source. The modification of the ion source also realized a significant stabilization of voltage holding and a short conditioning time. These results suggest a practical use of the large negative ion sources in JT-60 SA and ITER.

Journal Articles

Energy spectra of bremsstrahlung X-rays emitted from an FRP insulator

Tanaka, Yutaka; Ikeda, Yoshitaka; Hanada, Masaya; Kobayashi, Kaoru; Kamada, Masaki; Kisaki, Masashi; Akino, Noboru; Yamano, Yasushi*; Kobayashi, Shinichi*; Grisham, L. R.*

IEEE Transactions on Plasma Science, 37(8), p.1495 - 1498, 2009/08

 Times Cited Count:1 Percentile:4.64(Physics, Fluids & Plasmas)

Voltage holding capability of the JT-60 negative ion source is limited by surface flashover on the FRP insulator. To improve the voltage holding capability of the ion source, the understanding of the surface flashover is required. In this study, electron energy is estimated by measuring the bremsstrahlung X-ray emitted from an FRP insulator. Energy spectra of X-ray were measured for 3 different positions and compared with those of the vacuum gap between electrodes. Near the anode, X-ray spectrum was dominated by the monoenergetic electron. Near the cathode, spectrum peak shifted to low energy compared with that near the anode. This result showed that a large amount of low energy electrons was generated on the surface of the FRP insulator near the cathode.

Journal Articles

Characteristics of voltage holding capability in multi-stage large electrostatic accelerator for fusion application

Kobayashi, Kaoru; Hanada, Masaya; Akino, Noboru; Sasaki, Shunichi; Ikeda, Yoshitaka; Takahashi, Masahiro*; Yamano, Yasushi*; Kobayashi, Shinichi*; Grisham, L. R.*

IEEE Transactions on Dielectrics and Electrical Insulation, 16(3), p.871 - 875, 2009/06

 Times Cited Count:1 Percentile:12.71(Engineering, Electrical & Electronic)

Voltage holding capability of a 500kV, 22A three-stage electrostatic accelerator, where large-area grids of 0.28 m$$^{2}$$ and large FRP insulators of 1.8 m in diameter are used, was examined. High voltage was independently applied to each acceleration stage, where the voltage holding capabilities of 130 kV were obtained. To identify whether the breakdowns occur in the gaps between the grids or the FRP insulators, high voltages were applied to the accelerator with and without the grids. Breakdown voltages without grids, i.e., the FRP insulator itself reached 170 kV of design value for each stage. These results show that the breakdown voltage of the accelerator was mainly determined by the gaps between the large-area grids. In this paper, the influence of non-uniform electric field and multi-stage grids on the voltage holding capabilities was also discussed.

Journal Articles

Recent R&D activities of negative-ion-based ion source for JT-60SA

Ikeda, Yoshitaka; Hanada, Masaya; Kamada, Masaki; Kobayashi, Kaoru; Umeda, Naotaka; Akino, Noboru; Ebisawa, Noboru; Inoue, Takashi; Honda, Atsushi; Kawai, Mikito; et al.

IEEE Transactions on Plasma Science, 36(4), p.1519 - 1529, 2008/08

 Times Cited Count:8 Percentile:34.65(Physics, Fluids & Plasmas)

The JT-60SA N-NBI system is required to inject 10 MW for 100 s at 500 keV. Three key issues should be solved for the JT-60SA N-NBI ion source. One is to improve the voltage holding capability. Recent R&D tests suggested that the accelerator with a large area of grids may need a high margin in the design of electric field and a long time for conditioning. The second issue is to reduce the grid power loading. It was found that some beamlets were strongly deflected due to beamlet-beamlet interaction and strike on the grounded grid. The grids are to be designed by taking account of beamlet-beamlet interaction in three-dimensional simulation. Third is to maintain the D- production for 100 s. A simple cooling structure is proposed for the active cooled plasma grid, where a key is the temperature gradient on the plasma grid for uniform D- production. The modified N-NBI ion source will start on JT-60SA in 2015.

JAEA Reports

Horonobe Underground Research Laboratory project synthesis of phase I investigation 2001-2005 volume "Geological Disposal Research"

Fujita, Tomo; Taniguchi, Naoki; Matsui, Hiroya; Tanai, Kenji; Nishimura, Mayuka; Kobayashi, Yasushi; Hiramoto, Masayuki; Maekawa, Keisuke; Sawada, Atsushi; Makino, Hitoshi; et al.

JAEA-Research 2007-045, 140 Pages, 2007/03

JAEA-Research-2007-045-1.pdf:38.33MB
JAEA-Research-2007-045-2.pdf:44.62MB

This report summarizes the progress of research and development on geological disposal during the surface-based investigation phase (2001-2005) in the Horonobe Underground Research Laboratory project (HOR), of which aims are to apply the design methods of geological disposal and mass transport analysis to actual geological environments and derive future subjects based on the results. The design methods of geological disposal were reviewed based on the recent knowledge and the advertences were identified. Then the parameters for virtual design of engineered barrier system, backfill deposition hole and tunnel were set up based on actual geological conditions obtained from the surface-based investigations in HOR as an example of actual geological environment. The conceptual structure from site investigation and evaluation to mass transport analysis was represented as a work flow at first. Then following this work flow a series of procedures for mass transport analysis were carried out based on actual geological conditions obtained from the surface-based investigations in HOR to illustrate the functioning of the work flow and the applicability of this methodology. Consequently, knowledge that will help follow-up or future execution and planning activities was obtained.

JAEA Reports

Research on spherically converging ion-beam fusion neutron source for the fundamental research of atomic energy, JAERI's nuclear research promotion program, H10-050 (Contract research)

Yoshikawa, Kiyoshi*; Inoue, Nobuyuki*; Yamazaki, Tetsuo*; Makino, Keisuke*; Yamamoto, Yasushi*; Toku, Hisayuki*; Masuda, Kai*; Kii, Toshiteru*; Onishi, Masami*; Horiike, Hiroshi*; et al.

JAERI-Tech 2002-020, 63 Pages, 2002/03

JAERI-Tech-2002-020.pdf:4.94MB

no abstracts in English

Oral presentation

Development of knowledge management system for geologica disposal technology, 2

Umeki, Hiroyuki; Osawa, Hideaki; Naito, Morimasa; Nakano, Katsushi; Makino, Hitoshi; Miyamoto, Yoichi; Takase, Hiroyasu*; McKinley, I. G.*; Umeda, Koji; Asamori, Koichi; et al.

no journal, , 

no abstracts in English

Oral presentation

Conditioning characteristic of DC 500keV electrostatic accelerator with large FRPs

Kobayashi, Kaoru; Hanada, Masaya; Kamada, Masaki; Akino, Noboru; Sasaki, Shunichi; Ikeda, Yoshitaka; Takahashi, Masahiro*; Yamano, Yasushi*; Kobayashi, Shinichi*

no journal, , 

no abstracts in English

Oral presentation

Fabrication of silver solder electrode for vacuum breakdown test and its XPS analysis

Yamano, Yasushi*; Akashi, Keisuke*; Kobayashi, Shinichi*; Tanaka, Yutaka; Kobayashi, Kaoru; Akino, Noboru; Hanada, Masaya; Ikeda, Yoshitaka

no journal, , 

no abstracts in English

Oral presentation

Impact of locally strong electric field on voltage holding capability for long gap electrodes in vacuum

Kojima, Atsushi; Tanaka, Yutaka*; Nakano, Shusuke*; Shimizu, Tatsuo; Akino, Noboru; Hanada, Masaya; Yamano, Yasushi*; Kobayashi, Shinichi*

no journal, , 

JT-60 negative ion source suffered from a low voltage holding capability for long time. Recently, the voltage holding was much improved by tuning the gap lengths and minimum lengths between the acceleration grids of the ion source. This improvement is attributed to voltage holding tests of the accelerator. However, in order to design the next ion sources such as ITER and JT-60SA, further understandings and databases of vacuum insulation are required. As for the effect of the electric field, a small electrodes with small aperture which has the locally strong electric field were tested in this time. We found that the maimum electric field did not affect on the breakdown voltage, and large area of the electric filed profile decreased the breakdown voltage.

Oral presentation

Improvement of voltage holding capability toward JT-60SA ion source

Kojima, Atsushi; Shimizu, Tatsuo; Akino, Noboru; Hanada, Masaya; Yamano, Yasushi*; Kobayashi, Shinichi*; JT-60NBI Group

no journal, , 

Production of 500 keV, 3 A beams has been successfully achieved in the JT-60 negative by overcoming the low voltage holding of the accelerator. Toward the design of next ion source, we need to have database for the voltage holding capability based on experimental results. Up to now, voltage holding tests were carried out in terms of local electric field and surface area on large acceleration grids. This time, because outgas from FRP insulators has a possibility to affect the voltage holding of the acceleration grids, insulators made of low outgas epoxy was tested. As a result, because low outgas epoxy has small deviation of breakdown voltages, stable sustainment with 1.6 times higher voltage was attained than general epoxy insulators.

Oral presentation

Present status of a new pulsed neutron imaging instrument in J-PARC MLF

Shinohara, Takenao; Kai, Tetsuya; Segawa, Mariko; Oi, Motoki; Oikawa, Kenichi; Harada, Masahide; Nakatani, Takeshi; Sakai, Kenji; Iikura, Hiroshi; Aizawa, Kazuya; et al.

no journal, , 

no abstracts in English

46 (Records 1-20 displayed on this page)