The impact of the current density profile on heat transport and pedestal structure in JT-60U

摘要

H-modes operated at higher l_i with the current ramp down have shown higher energy confinement with higher density in JT-60U. The H-factor evaluated for the core plasma depends strongly on l_i with the relation of H_(89core) α l_i~(0.8) for the case without sawtooth activities. Centre peaked profiles of electron density and electron temperature are obtained in high l_i H-modes. While the peripheral current density profiles are largely modified by the current ramp, the pedestal pressure is not significantly changed. The enhanced energy confinement in high l_i H-modes is attributed to the core improvement with the peaked profiles of electron density and electron temperature while no explicit difference in pedestal profile is observed. The electron heat diffusivity is reduced at the plasma core in the high l_i case, resulting in the centre peaked T_e profile while the T_i profiles are approximately unchanged.