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Difference in Electron Transport Between Co- and Counter-NBI-Heated Plasmas in the Inward-Shifted Configurations on LHD

Hisamichi Funaba, Nobuyoshi Ohyabu, Yasuhiko Takeiri, Kiyomasa Watanabe, Shin Kubo, Takashi Shimozuma, Katsumi Ida, Junichi Miyazawa, Ryuichi Sakamoto, Kenichi Nagaoka, Kenji Tanaka, Byron Jay Peterson, Masaki Osakabe, Yoshio Nagayama, Shigeru Inagaki, Yoshiro Narushima, Satoru Sakakibara, LHD Experimental Group, Sadayoshi Murakami

Fusion Science and Technology / Volume 46 / Number 2 / September 2004 / Pages 262-270

Technical Papers / Stellarators /

In the low-density plasmas of the Large Helical Device, the shape of the electron temperature profile changes depending on the direction of the tangential neutral beam injection (NBI) when the magnetic axis position is inward-shifted at R = 3.50 m. Core flattening was observed in plasmas heated by counter-NBI. The electron thermal diffusivities in co-NBI and counter-NBI-heated plasmas are compared. The diffusivity becomes large at the central region in the case of counter-NBI. This result shows that the flattening in the electron temperature profile is not caused simply by a change in the power deposition only. Some magnetic fluctuations are seen during counter-NBI. On the other hand, it is a promising feature that the electron thermal diffusivity at the peripheral region does not increase with the heating power in co-NBI plasmas.

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