| Project/Area Number |
16206092
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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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 |
KOMORI Akio National Institute for Fusion Science, Department of LHD project, Professor (50143011)
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| Co-Investigator(Kenkyū-buntansha) |
OHYABU Nobuyoshi National Institute of Fusion Science, Department of LHD project, Professor (60203949)
MORISAKI Tomohiro National Institute of Fusion Science, Department of LHD project, Associate Professor (60280591)
KANNO Ryutaro National Institute of Fusion Science, Department of LHD project, Associate Professor (30270490)
MASUZAKI Suguru National Institute of Fusion Science, Department of LHD project, Associate Professor (80280593)
SHOJI Mamoru National Institute of Fusion Science, Department of LHD project, Associate Professor (00280602)
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| Project Period (FY) |
2004 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥49,270,000 (Direct Cost: ¥37,900,000、Indirect Cost: ¥11,370,000)
Fiscal Year 2007: ¥9,490,000 (Direct Cost: ¥7,300,000、Indirect Cost: ¥2,190,000)
Fiscal Year 2006: ¥14,690,000 (Direct Cost: ¥11,300,000、Indirect Cost: ¥3,390,000)
Fiscal Year 2005: ¥13,910,000 (Direct Cost: ¥10,700,000、Indirect Cost: ¥3,210,000)
Fiscal Year 2004: ¥11,180,000 (Direct Cost: ¥8,600,000、Indirect Cost: ¥2,580,000)
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| Keywords | divertor / magnetic island / edge plasma control / edge plasma / ergodic layer / heliotron configuration / LID |
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| Research Abstract |
During the research for four years, we discovered a high density operational regime by the central fuelling with the pellet injection and the strong pumping with the Local Island Divertor (LID). In this discharge, the superdense core region with the density more than 5×10^<20> m_<-3> and the temperature of〜0.8 keV is maintained by an Internal Diffusion Barrier (IDB) formed in the confinement region. These high parameters in the core plasma consequently provided the highest plasma performance (fusion triple product, n_0T_0τe=2.8×10^<19>m_<-3>keVs) obtained so far in the Large Helical Device (LHD). The LID is a kind of island divertor which utilizes an m/n=1/1 magnetic island artificially induced by the perturbation coils. The LID has the efficient pumping capability with its closed configuration and strong pumping system despite its compactness, which therefore brings about low particle recycling, i.e. low edge density.
In the recent experiments, however, it was found that such a high de
… More
nsity discharge with peaked electron density profile could be obtained not only in the LID configuration but in the Helical Divertor (HD) configuration, if only the reduced recycling could be achieved by the exhaustive wall conditioning. In the HD configuration with large flexibility of the magnetic field configuration, experiments were performed shifting the magnetic axis from standard position to outward shifted one. After the optimization of operational conditions, it was often observed that the central density collapse (CDC) took place with the increase of the central plasma pressure. In the CDC, the abrupt density decay at the center and the increase at the edge region were observed, suggesting the particle flush from the core region. In order to avoid the CDC, an attempt to suppress the Shafranov shift (outward shift of the plasma column) was made by changing the plasma shape. An effective result was obtained in the experiment with the expansion of the plasma parameters. The impurity behavior during the high density discharge was also investigated. In spite of the peaked density profile with IDB, no serious impurity accumulation was observed, although a certain quantity of carbon was sputtered on the surface of the divertor plates. This experimental result was also demonstrated by the numerical calculation with the EMC3-EIRENE code which suggests the strong parallel flow in the ergodic region to play an important role in impurity screening with its strong frictional force. Less
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