Speaker
Prof.
Kazuaki Hanada
(Advanced Fusion Research Center, Research Institute for Applied Mechanics, Kyushu University)
Description
Hydrogen (H) recycling and wall pumping properties on a dynamic retention dominant wall (metal wall) have been investigated in a medium size spherical tokamak QUEST. The plasma facing wall on QUEST originally made of stainless steel type 316L (SS316L) and partially coated by atmosphere plasma splay tungsten has been already covered with re-deposition layer of 5-100 nm in thickness due to plasma exposure. The re-deposition layer is composed of carbon, tungsten, ferrite, chromium and nickel according to X-ray photoelectron spectroscopy (XPS) measurement. Nuclear reaction analysis (NRA) is applied to specimens exposed QUEST H plasmas with exposing deuterium (D) plasma of approximately 1 eV, and presence of H-isotope barrier (HB) between the re-deposition layer and the substrate (SS316L) is confirmed due to little penetration to the substrate around 300-350K of the sample holder temperature. The HB must give a significant impact to H dynamic retention and a surface-recombination limiting model with HB is proposed. The model predicts a typical time constant representing wall saturation, which is relating to H flux to the wall, surface recombination coefficient, and thickness of re-deposition layer. In fact, the H storing capability on QUEST clearly depends on H flux and wall temperature experimentally. Especially time derivative wall stored H, that is wall pumping rate, has a clear relation to wall storing H and is well-fitted by the proposed model. Recently a hot wall is installed on QUEST to control H dynamic retention via modification of surface-recombination coefficient and its controllability of H dynamic retention in the range of 393K-473K is experimentally confirmed.
| Country or International Organization | Japan |
|---|---|
| Paper Number | EX/P4-49 |
Primary author
Prof.
Kazuaki Hanada
(Advanced Fusion Research Center, Research Institute for Applied Mechanics, Kyushu University)
Co-authors
Aki HIGASHIJIMA
(Research Institute for Applied Mechanics , Kyushu University)
Prof.
Akihide FUJISAWA
(Research Institute for Applied Mechanics , Kyushu University)
Dr
Arseniy Kuzmin
(Kyushu University, RIAM, AFRC, Japan, Kasuga)
Prof.
Atsushi Fukuyama
(Kyoto University)
Hideki Zushi
(Riam Kyushu University)
Dr
Hideo WATANABE
(Research Institute for Applied Mechanics , Kyushu University)
Dr
Hiroshi Idei
(Research Institute for Applied Mechanics, Kyushu University)
Mr
Hisatoshi NAKASHIMA
(Research Institute for Applied Mechanics , Kyushu University)
Prof.
Ikuji TAKAGI
(Graduate School of Engineering, Kyoto University, Japan)
Prof.
Kazuo NAKAMURA
(Research Institute for Applied Mechanics , Kyushu University)
Dr
Kazutoshi TOKUNAGA
(Research Institute for Applied Mechanics , Kyushu University)
Dr
Makoto HASRGAWA
(Research Institute for Applied Mechanics , Kyushu University)
Dr
Mituki MIYAMOTO
(Interdisciplinary Faculty of Science and Engineering, Shimane University)
Prof.
Naoaki YOSHIDA
(Research Institute for Applied Mechanics , Kyushu University)
Prof.
Osamu MITARAI
(School of Industrial Engineering,Tikai University)
Dr
Osamu WATANABE
(Research Institute for Applied Mechanics , Kyushu University)
Mr
Shoji KAWASAKI
(Research Institute for Applied Mechanics , Kyushu University)
Mr
Takahiro HIRATA
(Graduate School of Engineering, Kyoto University, Japan)
Mr
Takahiro NAGATA
(Research Institute for Applied Mechanics , Kyushu University)
Mr
Takumi HONDA
(Research Institute for Applied Mechanics , Kyushu University)
Dr
Takumi ONCHI
(Research Institute for Applied Mechanics , Kyushu University)
Dr
Yasuhisa Oya
(Shizuoka University)
Dr
Yoshihiko NAGASHIMA
(Research Institute for Applied Mechanics , Kyushu University)
Prof.
Yuichi Takase
(University of Tokyo)
Mr
Zhengxing WANG
(Research Institute for Applied Mechanics , Kyushu University)
