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Author(s):
Y. Takeiri et al.
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Title:
Confinement Improvement in High-ion Temperature Plasmas Heated with High-energy Negative-NBI in LHD
Date of publication:
Oct. 2006
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Key words:
21 IAEA Fusion Energy Conference , EX/P4-42
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Abstract:
The increase in the ion temperature due to transport improvement has been observed in plasmas heated with high-energy negative-NBI, in which electrons are dominantly heated, in Large Helical Device (LHD). When the centrally focused ECRH is superposed on the NBI plasma, the ion temperature is observed to rise, accompanied by formation of the electron-ITB. This is ascribed to the ion transport improvement with the transition to the neoclassical electron root with a positive radial electric field. In high-Z plasmas, the ion temperature is increased with an increase in the ion heating power, and reaches 13.5keV. The central ion temperature increases with an increase in a gradient of the electron temperature in an outer plasma region of rho=0.8, suggesting the ion transport improvement in the outer plasma region induced by the neoclassical electron root. These results indicate the effectiveness of the electron-root scenario for obtaining high-ion temperature plasmas in helical systems.
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