2006 Fiscal Year Final Research Report Summary
Study on hydrogen recycling during long term plasma-wall interaction
| Project/Area Number |
16560724
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Nuclear fusion studies
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| Research Institution | Kyushu University |
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Principal Investigator |
SAKAMOTO Mizuki Kyushu University, Research Institute for Applied Mechanics, Assoc.Prof., 応用力学研究所, 助教授 (30235189)
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| Co-Investigator(Kenkyū-buntansha) |
ZUSHI Hideki Kyushu University, Research Institute for Applied Mechanics, Prof., 応用力学研究所, 教授 (20127096)
YOSHIDA Naoaki Kyushu University, Research Institute for Applied Mechanics, Prof., 応用力学研究所, 教授 (00127317)
TOKUNAGA Kazutoshi Kyushu University, Research Institute for Applied Mechanics, Assoc.Prof., 応用力学研究所, 助教授 (40227583)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Plasma / Plasma-wall interaction / Hydrogen recycling / Wall pumping / Long duration discharge / Codeposition |
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| Research Abstract |
We have developed multi-channel visible spectroscopic system and real time erosion and deposition diagnostics to study hydrogen recycling during long term plasma-wall interaction. Moreover, material probe experiments were carried out to study the hydrogen recycling from a material point of view.
The relation between the line averaged electron density and toroidal profile of Hα line intensity was obtained. The characteristic length λ of the toroidal profile of Hα line intensity gradually decreases with increase in the density n_e (i.e.λ∝ n^<-0.2>_e). The DEGAS simulation of the dependence of λ on n_e revealed that the neutral transport in a scrape-off layer and a peripherally plasma is important for a formation of the toroidal profile of Hα intensity. The wall pumping rate has been estimated using global particle balance in the vacuum vessel. In the case of low temperature wall (T<60℃), global wall saturation was not occurred during 5 h 16 min discharge and the averaged wall pumping rate was 8.6x10^<16> H m^<-2> s^<-1>,which is about 3.6 times higher than that of the high temperature wall case (T<120℃). In the case of the high temperature wall, the wall saturation occurred. The wall pumping seems to be attributed to codeposition of hydrogen with molybdenum which has sputtered at a limiter or divertor plates. During the 5 h 16 min discharge, the thickness of a deposited layer almost monotonically increased with the discharge duration. This is similar to the time evolution of the wall inventory. From the material probe experiments, it becomes obvious that the codeposited layer of molybdenum has a high capability of hydrogen absorption, which is comparable to that of carbon. The hydrogen absorption rate estimated from the material probe is good agreement with the wall pumping rate estimated from the global particle balance.
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