Two-dimensional diagnostic of edge plasma structure using a lithium beam probe in a compact helical system
- Graduate University for Advanced Studies, 322-6 Oroshi-Cho, Toki 509-5292 (Japan)
A neutral lithium beam probe for two-dimensional diagnosis of edge plasmas has been designed and installed on the compact helical system. A lithium beam with an energy of 15 keV and a current of 0.1 mA is used. The spatial resolution is about 10 mm, and the time response is about 10 ms. The beam penetration depth is expressed in terms of the line integral density <n{sub e}l>, which is about 2x10{sup 18} m{sup -2}. The beam injection angle can be varied and the observation point covers the edge and separatrix region of the helical diverter configuration. Two-dimensional electron density profiles for electron cyclotron heating and neutral beam injection (NBI) heated plasmas are obtained near and outside the last closed flux surface (LCFS). Analysis for two-dimensional density profile reconstruction indicates that significant amounts of surface plasma are confined outside the LCFS for NBI plasmas even though the ergodic layer is cut by the vacuum chamber wall (inboard limiter configuration). The use fullness of this new two-dimensional diagnostic in the edge region is demonstrated.
- OSTI ID:
- 20644058
- Journal Information:
- Review of Scientific Instruments, Vol. 76, Issue 1; Other Information: DOI: 10.1063/1.1809284; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
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