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.

Effect of 14-MeV neutrons on strontium-aluminate-based long-lasting phosphor

To, Kentaro; Shikama, Tatsuo*; Katsui, Hirokazu*; Nagata, Shinji*; Tsuchiya, Bun*; Yamauchi, Michinori*; Nishitani, Takeo

Journal of Nuclear Materials, 386-388, p.1027 - 1029, 2009/04

https://doi.org/10.1016/j.jnucmat.2008.12.205

Fluorescence and long-lasting emission properties of two types of Long-lasting phosphors (LLPs), SrAlO:Eu,Dy and SrAlO:Eu,Dy, were examined under 14-MeV neutron irradiation. The fluorescent spectra of the LLPs have characteristic peaks due to their dopants and the fluorescent intensity of SrAlO:Eu,Dy shows good radiation resistance for the neutrons fluence up to 10 n/m. Long-lasting emissions are exhibited after neutron irradiation, and the emission spectra have one peak due to Eu. Further, it is found that there is an optimum neutron fluence at which the longest decay time is obtained.

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

Hydrogen retention induced by ion implantation in tungsten trioxide films

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

Nuclear Instruments and Methods in Physics Research B, 267(8-9), p.1480 - 1483, 2009/03

https://doi.org/10.1016/j.nimb.2009.01.139

We quantitatively studied the relation between hydrogen retention and optical properties induced by hydrogen ion implantation in tungsten trioxide (WO) films. Films of WO (300 nm) covered with tungsten metal layers (200 nm) were prepared on transparent SiO substrates by a reactive sputtering in Ar and O mixture. When H ions were implanted into the samples at an acceleration voltage of 10 kV, the concentration of hydrogen retaining in the WO films increased up to 0.4 H/W in proportion to the fluence of H ions. The optical absorption coefficient at 750 nm of samples increased linearly by 3 m with increasing the concentration of hydrogen implanted up to 0.1 H/W. And then, increased and saturated at 4 m with the increase of hydrogen concentration higher than 0.1 H/W. It was found that the hydrogen retention up to 0.1 H/W in tungsten trioxide layers can be monitored by measuring the optical absorbance.

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.