We have experimentally studied the effect of neutrals on the H-mode transition in JT-60U. The neutral density near the separatrix (n 95 0 ) was evaluated with the DEGAS code. The effective edge ion collisionality (ν * i eff ) right before the H-mode transition tends to decrease with the increase of n 95 0 /n 95 e . L-and H-mode phases are clearly separated in the ν * i eff -n 95 0 /n 95 e plane. This result suggests that the edge neutrals have a substantial influence on the condition of the H-mode transition.

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Experiments of a reversed field pinch device REPUTE-1 constructed in University of Tokyo started in 1984. The conductivity electron temperature and the line-averaged electron density increase approximately linearly with the increase of plasma current in the range up to 240 kA. The study of the effect of the bias toroidal field on the discharge characteristics shows that a higher bias field gives lower resistivity and a higher flat top plasma current. The toroidal flux at the current flat top tends to be a selective value independent of the initial bias field.

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