2006 Fiscal Year Final Research Report Summary
Investigation of loss mechanism of NBI-generated high-energy particles by Alfven eigenmode in helical system
| Project/Area Number |
16360460
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 |
TAKEIRI Yasuhiko National Institute for Fusion Science, Department of Large Helical Device Project, Professor, 大型ヘリカル研究部, 教授 (60179603)
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| Co-Investigator(Kenkyū-buntansha) |
OSAKABE Masaki National Institute for Fusion Science, Department of Large Helical Device Project, Research Associate, 大型ヘリカル研究部, 助手 (90280601)
IKEDA Katsunori National Institute for Fusion Science, Department of Large Helical Device Project, Research Associate, 大型ヘリカル研究部, 助手 (20321614)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Alfven eigenmode / high-energy particle / Large Helical Device / neutral beam injection system / neutral particle analyzer / slowing-down process |
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| Research Abstract |
The objective of this research is to clarify the loss mechanisms of the energetic particles by the Alfven eigenmodes (AE modes) excited by the high-energy NBI-heating beams in the helical system with a three-dimensional magnetic configuration. For this, the energy spectra of the energetic particles with a neutral particle analyzer and the heat load profiles in the divertor region due to the loss particles with an IR camera have been measured in Large Helical Device. As a result, the following conclusions are obtained.
1.As well in tokamaks, the interaction between the AE mode and the energetic particles occurs in the helical system, which enhances the radial transport of the energetic particles at around a mode gap identified from the two-dimensional shear-Alfven spectra, and that often leads to the energetic particle loss.
2.The energetic particles interacting with the AE mode show the behavior depending on their co-/counter direction. This is not because the interaction itself between the energetic particles and the AE mode has the dependence on the co-/counter direction, but because the loss-cone structure to the energetic particles has the dependence on it.
3.It is the main mechanism of the energetic particle loss by the AE mode that the energetic particles, the radial transport of which is enhanced by the interaction with the AE mode, enter the loss-cone region and that they are lost from the plasma as a consequence.
4.It is found that the heat load in the divertor region is almost proportional to the square of the magnetic fluctuation intensity. That suggests that the enhancement of the radial transport of the energetic particles by the AE mode is caused by the overlapping of the magnetic islands formed by the AE modes. The orbit calculation considering the fluctuation is required, and it is a future work.
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