2007 Fiscal Year Final Research Report Summary
Development and research of transport simulation analysis of CxHy series hydrocarbon molecules in the plasma periphery
| Project/Area Number |
18560794
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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 | National Institute for Fusion Science |
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Principal Investigator |
SHOJI Mamoru National Institute for Fusion Science, National Institute for Fusion Science, LHD projects, Assistant Professor (00280602)
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| Project Period (FY) |
2006 – 2007
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| Keywords | HydroCarbon / Impurity transport / Peripheral plasma / Divertor / Image measurement / Large Helical Device |
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| Research Abstract |
It is very important to clarify the behavior of hydrocarbon molecules in the plasma periphery for aiming at future nuclear fusion reactors. We tried to measure the profile of a visible line emission (CH-band) emitted by hydrocarbon molecules. For this purpose, we installed a CCD camera with an interference filter in an outer port (7-O) in the LHD vacuum vessel in order to observe lower divertor legs in the plasma periphery and plasma-wall interactions on divertor plates installed near a lower port. The viewing angle and exposure time of the camera are fully controlled from the remote side (from the LHD control room). Using the CCD camera, we have succeeded in measuring the emission profile on the lower divertor legs in the plasma periphery and extending the important knowledge for investigating the behavior of hydrocarbon molecules in the peripheral plasma. The movement of the emission area of the CH-band from the downstream side to the upstmam side on the divertor leg was observed dur
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ing the process to radiation collapse by increasing the plasma density due to excessive gas fueling. This phenomenon can give us very important information to investigate the physical mechanism of the transport of the hydrocarbon molecules in the divertor region The investigation can contribute to clarification of the effect of the hydrocarbon molecules to the radiation collapse in LHD plasmas.
For detailed analysis of the transport of the hydrocarbon molecules in the divertor region, a three-dimensional neutral particle transport simulation code is an essential tool. We found that the parallel computing of the three-dimensional neutral particle transport simulation code is necessary for detailed analysis of the transport of the hydrocarbon molecules on the divertor legs. Thus, we tried to modify the code for the parallel computing and succeeded in shortening the computation time significantly. The database of the cross-section of the atomic and molecular process of hydrocarbon molecules has been updated. We can expect detailed analysis of the transport of the hydrocarbon molecules by combination of the updated database and the fully parallelized simulation code in the LHD plasma periphery. Less
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