Speaker
Masayuki Tokitani
(Department of Helical Plasma Research)
Description
The study is focused on modification of surfaces of the tungsten-coated divertor tiles used in the first campaign (2011-2012) of the JET tokamak with the ITER-lLike Wall (JET-ILW). The analyses by means of several material research techniques have been carried out at International Fusion Energy Research Centre (IFERC), JAEA Rokkasho.
Samples, in the form of disks (17 mm in diameter), extracted from the inner divertor were studied: Tiles 1, 3 and 4, i.e. upper, vertical and horizontal targets, respectively. The selection of samples for detailed examination was based on the result of an imaging plate (IP) analysis. A specimen from the apron of Tile 1 was deposition-dominated. Thin and stratified mixed-material layers deposited on the original tungsten substrate were composed of Be, W, Ni, O and C. Their total thickness was ~200-400 nm. By means of transmission electron microscopy (TEM) large bubbles with size of over 100 nm were identified in that layer. They could be related to deuterium retention in the layer dominated by beryllium. Indeed, it has been reported earlier that the amount of deuterium on top of Tile 1 was highest among the three tiles. The surface microstructure of the sample from Tile 4 also showed deposition: a stratified mixed-material layer with the total thickness of ~200 nm. The electron diffraction pattern obtained with TEM indicated beryllium as the major component of the layer. No bubble-like structures have been identified. The surface of Tile 3, originally coated by Mo, was identified as the erosion zone. This is agreement with the fact that the strike point was often located on that tile during the plasma operation.
In summary, the study revealed the micro- and nano-scale modification of the inner tile surface of the JET-ILW. Especially, complex mixed-material deposition layer could affect the hydrogen isotope retention and dust formation.
Co-authors
Anna M Widdowson
(Culham Centre for Fusion Energy, Culham Science Centre, Abingdon, OX14 3DB, United Kingdom)
Contributors JET
(Culham Centre for Fusion Energy, Culham Science Centre, Abingdon, OX14 3DB, United Kingdom)
Dai Hamaguchi
(Rokkasho Fusion Institute, Japan Atomic Energy Agency, 2-166 Omotedate, Obuchi, Rokkasho-mura, Kamikita-gun, Aomori, Japan)
Hironori Kurotaki
(Rokkasho Fusion Institute, Japan Atomic Energy Agency, 2-166 Omotedate, Obuchi, Rokkasho-mura, Kamikita-gun, Aomori, Japan)
Kanetsugu Isobe
(Rokkasho Fusion Institute, Japan Atomic Energy Agency, 2-166 Omotedate, Obuchi, Rokkasho-mura, Kamikita-gun, Aomori, Japan)
Makoto Oyaidzu
(Rokkasho Fusion Institute, Japan Atomic Energy Agency, 2-166 Omotedate, Obuchi, Rokkasho-mura, Kamikita-gun, Aomori, Japan)
Marek Rubel
(Department of Fusion Plasma Physics, Royal Institute of Technology, 100 44 Stockholm, Sweden)
Masayuki Tokitani
(Department of Helical Plasma Research, National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu, Japan)
Mitsutaka Miyamoto
(Department of Materials Science, Shimane University, 1060 Nishi-Kawatsu, Matsue, Shimane, Japan)
Nobuyuki Asakura
(Rokkasho Fusion Institute, Japan Atomic Energy Agency, 2-166 Omotedate, Obuchi, Rokkasho-mura, Kamikita-gun, Aomori, Japan)
Ryuichi Sakamoto
(Department of Helical Plasma Research, National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu, Japan)
Suguru Masuzaki
(Department of Helical Plasma Research, National Institute for Fusion Science, 322-6 Oroshi, Toki, Gifu, Japan)
Takumi Suzuki
(Rokkasho Fusion Institute, Japan Atomic Energy Agency, 2-166 Omotedate, Obuchi, Rokkasho-mura, Kamikita-gun, Aomori, Japan)
Teppei Otsuka
(Interdisciplinary Graduate School of Engineering Science, Kyushu University, 6-10-1 Hakozaki, Fukuoka, Japan)
Yasuhisa Oya
(College of Science, Academic Institute, Shizuoka University, 836 Ohya, Suruga-ku,Shizuoka, Japan)
Yuji Hatano
(Hydrogen Isotope Research Center, University of Toyama, 3190 Gofuku,Toyama, Japan)
Yuta Fujii
(Department of Materials Science, Shimane University, 1060 Nishi-Kawatsu, Matsue, Shimane, Japan)
