2002 Fiscal Year Final Research Report Summary
Vortex Formation and Its Interaction in Real Plasmas
| Project/Area Number |
12680486
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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 |
プラズマ理工学
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| Research Institution | National Institute for Fusion Science |
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Principal Investigator |
TANAKA Masayoshi National Institute for Fusion Science, R&D Division, Associate Professor, 大型ヘリカル研究部, 助教授 (90163576)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHIMURA Shinji National Institute for Fusion Science, R&D Division, Research Associate, 大型ヘリカル研究部, 助手 (50311204)
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| Project Period (FY) |
2000 – 2002
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| Keywords | plasma hole / Burgers vortex / dissipative vortex structure / velocity vector field / vorticity / anomalous viscosity / tripolar vortex / anti-ExR rotation |
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| Research Abstract |
A new method of measuring flow velocity has been developed with the symmetry principle on ion saturation current of a directional Langmuir probe. The general relation between ion flow velocity and probe signal has been obtained. Measuring ExB rotation velocity by a directional Langmuir probe and an emissive probe, we have demonstrated that the effect of magnetic field on the probe current can be eliminated, and that the directional probe method for flow velocity measurements is valid in magnetized plasmas.
Using this method, we have measured velocity fields, and examined vortex formation in plasmas, by constructing the vorticity distribution. Two types of vortex, which have never been observed in plasmas, have been found. One is Burgers vortex (plasma hole). This vortex appears with a density cavity in its center and viscosity of the plasma exhibits anomaly.
The second type of vortex is a tripolar vortex, which rotates in the inverse direction of ExB drift. It is found that strong inhomogeneity in the back ground neutrals causes a neutral flow, whose momentum is transported into the ions by the charge exchange interactions, and then produces a net radial force stronger than the internal radial electric field. The tripolar vortex is the first observation of vortex in a plasma caused by a mechanism other than ExB drift.
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