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

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.