2005 Fiscal Year Final Research Report Summary
Studies on Fine Structures on the Electron Temperature Profiles of Helical Plasma
| Project/Area Number |
14380221
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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 |
NARIHARA Kazumichi National Institute for Fusion Science, Department of Large Helical Device, Professor, 大型ヘリカル研究部, 教授 (90109356)
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| Co-Investigator(Kenkyū-buntansha) |
YAMADA Ichihiro National Institute for Fusion Science, Department of Large Helical Device, Research Associate, 大型ヘリカル研究部, 助手 (80222371)
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| Project Period (FY) |
2002 – 2005
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| Keywords | LHD / Thomson scattering / Electron temperature profile / Internal Transport Barrier / Filamentation |
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| Research Abstract |
Through a continuous effort to improve the performance and the calibration method of the LHD Thomson scattering diagnostic, we can measure electron temperature profile(Te) with much better data quality as well as electron density profile (ne), though not yet of high quality. Thus we measured variety of Te profiles and obtained the following phenomenological knowledge.
1.We reconfirmed with a higher confidence that the vacuum magnetic island formed by an error magnetic field do ‘self-heal' in the presence of plasma and found that (1)the ‘self-healing' of a magnetic island becomes weaker as the magnetic axis position is shifted in wards ; (2)the width of the magnetic island becomes smaller as the Te (or pressure) at the island increases ; (3)If the width of the vacuum magnetic island exceeds a threshold, the island never disappears even in a high Te plasma ; (4)plasma current responsible for the ‘self-healing' is really present
2.Knees on a Te profile sometimes appear not only in the edge
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region but also in the inner region. The transport property seems to be different between two regions separated by the knee surface.
3.Using laser beams with different energies, we demonstrated that a seeming structure on Te profile arises from the noise on the optical detectors. Applying a higher-energy-laser on a higher-density-plasma, we confirmed with a high confidence that there appears a sharp symmetric structure in response to a highly focused electron cyclotron heating, which resembles in some sense a filamentation observed on RTP.
4.As the beta (plasma pressure/magnetic pressure)increases, flat regions on Te profile first appear in the inner region and then in the outer region. The Te profile with the highest beta value sometimes accompanies a flat region on the foot in the low field side, which resembles a ballooning mode.
5.We observed a hollow Te profile, a Te profile with bulges at the island position, and a stair-like Te profile.,We also observed that the pellet-induced inward electron flux is almost completely blocked.
We are planning to study the two-dimensional property of the magnetic island by installing another laser beam path 20cm below the magnetic axis Less
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