H-mode pedestal structure in the variation of toroidal rotation and toroidal field ripple in JT-60U

摘要

The effects of toroidal rotation and toroidal field (TF) ripple on the edge pedestal structure and edge-localized-modes (ELMs) were examined in JT-60U. The amplitude of the TF ripple was changed by the installation of ferritic steel tiles (FSTs). The profile of toroidal rotation V_T became less counter with FSTs, particularly in the case where co-NBI was used in a large volume configuration. In this case, the plasma pressure was raised across the whole profile of the plasma. At the plasma edge, higher pedestal temperature was obtained with the growth of pedestal width. However, the effect of FSTs became less significant in a small volume configuration. As the V_T became less counter at the pedestal, ELM frequency /ELM was reduced and ELM energy loss ΔW_(ELM) was increased at fixed power crossing the separatrix P_(sep). The observed larger ELM energy drop at V_T in a relatively co-direction involves the ELM perturbations of the electron temperature profile across an ELM that extends radially more inward. In addition, the inter-ELM transport loss is reduced and the pedestal pressure p~(ped) is weakly raised. The effect of FSTs appeared clearly in the large volume configuration where p~(ped) is raised even at a given V_T at the pedestal while p~(ped) is not changed by FSTs at the small volume configuration. This suggests that the reduction of the TF ripple, the magnitude of which can affect the V_T profile, plays a role in the increasing of p~(ped). For increased p~(ped) due to the use of co-NBI and the reduction of TF ripple, the spatial width of the pedestal ion temperature became greater.