Multiple plasma transport states in the H-mode transition on JT-60U

Multiple turbulent plasma states in the edge transport barriers formation are studied on JT-60U. Following a slow L–H transition, which causes significant reduction in the ion thermal transport in the pedestal towards the neoclassical level with a weak negative E _r value, we found clear and fast changes in the particle transport in association with the change in E _r towards a strong negative value at the later H-phase. It has also been suggested that there is a clear difference in responses between ion and electron transports due to the change in the inhomogeneity in E _r. This observation suggests the presence of multiple types of turbulent fluctuations in the H-mode plasma state, which affects the ion energy and other channels of transport differently. The nonlinear dynamics that induce the E _r-bifurcation are also analyzed in terms of the radial current generation. These analyses contribute to understanding of the L–H transition condition. (paper)