Electrode biasing experiments were carried out in the Tohoku University Heliac (TU-Heliac) to investigate the role of ion viscosity maxima in the L-H transition. To investigate the relation between ion viscosity and poloidal Mach number, the driving force of the poloidal rotation and poloidal rotation velocity must be normalized by the ion temperature Ti and ion pressure Pi. Doppler spectroscopy was used to directly measure the ion temperature and the poloidal rotation velocity. Therefore, the dependence of the ion temperature and poloidal rotation velocity on the electrode current was obtained. The relation between the normalized driving force of the poloidal rotation and the poloidal Mach number Mp was non-linear. Bifurcation phenomena in the poloidal rotation appeared at Mp ~ -3. These results qualitatively agreed with the neoclassical theory.
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