Development of divertor simulation research in the GAMMA 10/PDX tandem mirror

Nakashima, Yosuke*; Sakamoto, Mizuki*; Yoshikawa, Masayuki*; Oki, Kensuke*; Takeda, Hisahito*; Ichimura, Kazuya*; Hosoi, Katsuhiro*; Hirata, Mafumi*; Ichimura, Makoto*; Ikezoe, Ryuya*; et al.

Proceedings of 25th IAEA Fusion Energy Conference (FEC 2014) (CD-ROM), 8 Pages, 2014/10

Competition between magnetic ordering and random spin freezing in DyPtS

Li, D.*; Yamamura, Tomoo*; Homma, Yoshiya*; Yubuta, Kunio*; Shikama, Tatsuo*; Aoki, Dai*; Nimori, Shigeki*; Haga, Yoshinori

Journal of the Korean Physical Society, 62(12), p.2233 - 2238, 2013/06

https://doi.org/10.3938/jkps.62.2233

Japanese contribution to the DEMO-R&D program under the Broader Approach activities

Nishitani, Takeo; Yamanishi, Toshihiko; Tanigawa, Hiroyasu; Nozawa, Takashi; Nakamichi, Masaru; Hoshino, Tsuyoshi; Koyama, Akira*; Kimura, Akihiko*; Hinoki, Tatsuya*; Shikama, Tatsuo*

Fusion Engineering and Design, 86(12), p.2924 - 2927, 2011/12

https://doi.org/10.1016/j.fusengdes.2011.07.004

Several technical R&D activities related to the blanket materials are newly launched as a part of the Broader Approach (BA) activities, which was initiated by the EU and Japan. According to the common interests of these parties for DEMO, R&Ds on reduced activation ferritic/martensitic (RAFM) steels as structural material, SiCf/SiC composites as a flow channel insert material and/or alternative structural material, advanced tritium breeders and neutron multipliers, and tritium technology are carried out through the BA DEMO R&D program, in order to establish the technical bases on the blanket materials and the tritium technology required for DEMO design. This paper describes overall schedule of those R&D activities and recent progress in Japan carried out by JAEA as the domestic implementing agency on BA, collaborating with Japanese universities and other research institutes.

Effects of neutrons and gamma-rays on polymethylmethacrylate plastic optical fiber

To, Kentaro; Sakasai, Kaoru; Nakamura, Tatsuya; Soyama, Kazuhiko; Shikama, Tatsuo*

Journal of Nuclear Materials, 417(1-3), p.814 - 817, 2011/10

https://doi.org/10.1016/j.jnucmat.2010.12.258

Plastic optical fibers (POFs) are very useful and widely used for signal transmission because they have the following advantages: (1) they do not produce electrical noise, (2) they are inexpensive and lightweight, and (3) they have wide optical signal bands. In this study, the effects of 14-MeV neutron and -ray irradiation on a POF were investigated. Strong radiation damage (radiation-induced transmission loss) was caused by irradiation with both neutrons and -rays, particularly at short wavelengths. To determine the effects of neutron and -ray irradiation, the amount of energy absorbed in the PMMA POF was calculated by using a Monte Carlo simulation using PHITS code. The similar radiation effect with both neutrons and -rays was observed at an absorbed energy less than 510 eV.

Feasibility study on cryogenic irradiation facility in JMTR

Inaba, Yoshitomo; Tsuchiya, Kunihiko; Shikama, Tatsuo*; Nishimura, Arata*; Kawamura, Hiroshi

Fusion Engineering and Design, 86(2-3), p.134 - 140, 2011/03

https://doi.org/10.1016/j.fusengdes.2010.09.024

The Japan Materials Testing Reactor (JMTR) of the Japan Atomic Energy Agency is a testing reactor with first criticality in March 1968. The reactor has been utilized for various neutron irradiation tests on nuclear fuels and materials, as well as for radioisotope production. The operation of JMTR stopped temporarily in August 2006 for refurbishment and improvement. The renewed JMTR will resume operation in Japanese fiscal year 2011. For the resumption of the new JMTR, the new irradiation facilities, the usability improvements, the target, and the expected roles of the new JMTR have been discussed. As one of the new irradiation facilities, the cryogenic irradiation facility, which is used for the investigation on the low-temperature irradiation behavior of materials such as superconducting magnet materials for fusion reactors, has been desired. In this study, the feasibility of low-temperature irradiation tests with the cryogenic irradiation facility was investigated, and the conceptual design of the facility was carried out. As a result, it was found that irradiation tests at temperatures below 20 K for the development of the superconducting magnet materials can be realized by the installation of an irradiation capsule into an irradiation hole with low heating and by the adoption of vacuum jacketed tubes to connect between the capsule and a cooling system.

Ion irradiation effects on the optical properties of tungsten oxide films

Nagata, Shinji*; Fujita, Haruka*; Inoue, Aichi; Yamamoto, Shunya; Tsuchiya, Bun*; Shikama, Tatsuo*

Nuclear Instruments and Methods in Physics Research B, 268(19), p.3151 - 3154, 2010/10

https://doi.org/10.1016/j.nimb.2010.05.076

A tungsten tri-oxide (WO) film covered with a thin catalyst layer is one of the candidates for hydrogen sensing devices that show a reversible coloration under hydrogen exposure. While the injection of the cations and/or the formation of the oxygen vacancies can be responsible for the coloration of the film, the mechanism of the gasochromic phenomenon is not fully understood. In the present work, the changes of the optical properties in the WO film by ion irradiation were investigated to clarify the relation between the coloration and oxygen vacancies. WO films of 300-500 nm thicknesses were deposited on SiO substrates by magnetron sputtering. Oxygen ions at energies between 200 and 800 keV were irradiated to the WO films. The optical absorption of the film was measured in the wavelengths between 190 and 1000 nm. The results show that the change of optical-absorption coefficient in WO films depends on both electronic and nuclear stopping powers.

Fusion materials development program in the Broader Approach activities

Nishitani, Takeo; Tanigawa, Hiroyasu; Jitsukawa, Shiro; Nozawa, Takashi; Hayashi, Kimio; Yamanishi, Toshihiko; Tsuchiya, Kunihiko; Mslang, A.*; Baluc, N.*; Pizzuto, A.*; et al.

Journal of Nuclear Materials, 386-388, p.405 - 410, 2009/04

https://doi.org/10.1016/j.jnucmat.2008.12.146

The establishment of the breeding blanket technology is one of the most important engineering issues on the DEMO development. For the DEMO blanket, developments of the structural materials and functional materials such as tritium breeder and neutron multiplier. Which should be used under the savior circumstance such as high neutron fluence, high temperature and strong magnetic field, are urgent issues. In the Broader Approach activities initiated by EU and Japan, developments of reduced activation ferritic martensitic steels as a DEMO blanket structural material, SiC/SiC composites, advanced tritium breeders and neutron multiplier for DEMO blankets, are planed as common interest issues of EU and Japan. This paper describes the overview of the development program.

Damage process and luminescent characteristics in silica glasses under ion irradiation

Nagata, Shinji*; Katsui, Hirokazu*; Tsuchiya, Bun*; Inoue, Aichi; Yamamoto, Shunya; To, Kentaro; Shikama, Tatsuo*

Journal of Nuclear Materials, 386-388, p.1045 - 1048, 2009/04

https://doi.org/10.1016/j.jnucmat.2008.12.246

no abstracts in English

Ion induced structural modification and nano-crystalline formation of Zr-Al-Ni-Cu metallic glasses

Nagata, Shinji*; Sasase, Masato*; Takahiro, Katsumi*; Tsuchiya, Bun*; Inoue, Aichi; Yamamoto, Shunya; Shikama, Tatsuo*

Nuclear Instruments and Methods in Physics Research B, 267(8-9), p.1514 - 1517, 2009/03

https://doi.org/10.1016/j.nimb.2009.01.079

In this study, effects of the ion implantation on the phase transformation and nano-crystalline formation were examined in Zr-based metallic glasses. Samples were 2 mm thick plates and thin films of ZrAlNiCu prepared by casting in a copper mold and by using RF magnetron sputtering, respectively. Ions of Mg, P, Au and Bi with 100-500 keV were implanted in the samples up to 2 10 ions/cm at room temperature. Nano-crystalline structure was found in implanted samples by TEM observation, while the long-range order in the structure was not found for the X-ray diffraction patterns. The electron diffraction patterns indicated the formation of fcc-ZrCu in the P, Au, and Bi implanted region. Changes of the binding energy of the core level electron and valence band structure suggested the formation of Au-Zr or Au-Cu alloys in the Au ion implanted region.

Effects of catalyst on gasochromic properties in tungsten oxide films

Inoue, Aichi; Yamamoto, Shunya; Nagata, Shinji*; Yoshikawa, Masahito; Shikama, Tatsuo*

Transactions of the Materials Research Society of Japan, 33(4), p.1127 - 1130, 2008/12

We investigated effects of catalyst on gasochromic properties in tungsten oxide films. Amorphous WO films coated with Pd and Pt catalysts were prepared on SiO substrates by employing reactive RF magnetron sputtering. The field emission scanning electron microscope (FE-SEM) showed that particles with a dozes nm diameter of Pd and with a few nm of Pt grew on the surface at beginning of deposition. The continuous catalytic layers were observed with increasing the amounts of more than 2 nm for Pd and 0.2 nm for Pt catalysts, respectively. When the continuous layers formed on WO surface, the excellent gasochromic properties were obtained. The results indicated that Pt catalysts were suitable for high sensitive hydrogen sensors consisting of gasochromic WO films.