| Co-Investigator(Kenkyū-buntansha) |
SUZUKI Hajime National Institute for Fusion Science, Department of Large Helical Device Project, Assistant Professor, 大型ヘリカル研究部, 助手 (20260044)
WATANABE Tsuguhiro National Institute for Fusion Science, Department of Large Helical Device Project, Professor, 大型ヘリカル研究部, 教授 (70023728)
OHYABU Nobuyoshi National Institute for Fusion Science, Department of Large Helical Device Project, Professor, 大型ヘリカル研究部, 教授 (60203949)
MASUZAK Suguru National Institute for Fusion Science, Department of Large Helical Device Project, Assistant Professor, 大型ヘリカル研究部, 助手 (80280593)
MORISAKI Tomohiro National Institute for Fusion Science, Department of Large Helical Device Project, Assistant Professor, 大型ヘリカル研究部, 助手 (60280591)
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| Research Abstract |
Aims of this research project are to develop technical and design studies of a local island divertor (LED) and to realize it in fusion-experiment devices, especially in the Large Helical Device (LHD).
The LID is a divertor that uses an m/n=1/1 island formed at the edge region. The outward heat and particle fluxes crossing the island separatrix flow along the field lines to the back of the island, where divertor plates are placed on a divertor head to receive heat and particle loads. The particles recycled there are pumped out by a pumping system. Unlike conventional pump limiters, leading edges of the divertor head are located well inside the island for the standard LID configuration, thereby being protected from the outward heat flux from the core. The principle of the LID has been proved by the experimental study on the Compact Helical System (CHS).
In this research project, a comparison between theory and observation was performed at first, using the experimental results measured in CHS and theoretical predictions obtained, for example, by a Monte Carlo neutral-particle simulation code. This provided us critical information on the edge plasma behavior in the heliotron-type device, and helped us to optimize the design of the LID for LHD. Especially, the geometrical design of the divertor head and pumping duct was completed, and a closed divertor configuration was demonstrated to be realized with high pumping efficiency of > 30%. Highly efficient pumping is the key to realizing the high temperature divertor operation, where a divertor plasma with a temperature of a few keV is produced, leading to a significant energy confinement improvement.
After the technical studies were finished, the LID was fabricated, and installed in LHD at the end of 2002 fiscal year. Preliminary experiments performed in 2003 suggested the existence of fundamental divertor functions expected for the LID, so that the aims of this research project were achieved.
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