Studies on impact of electron cyclotron wave injection on the internal transport barriers in JT-60U weak shear plasmas

Ide, Shunsuke; Takenaga, Hidenobu; Isayama, Akihiko; Sakamoto, Yoshiteru; Yoshida, Maiko; Gormezano, C.*

Impact of the electron cyclotron range of frequency wave (ECRF) on the internal transport barriers (ITBs) in a weak shear (WS) plasma has been investigated in JT-60U. It is observed that the ion temperature () ITB in a WS plasma can be degraded by ECRF. It is clarified for the first time that the degradation depends increasingly on the EC power () but decreasingly on the plasma current (). Moreover it is confirmed that ECRF affects the toroidal rotation () indirectly and results in flattening of profiles regardless of the direction of the target . Furthermore, it is newly found that and in the whole ITB region are affected with almost no delay from the EC onset even with off-axis EC deposition. These results indicate that the EC injection unveiled a semi-global structure that characterizes ITB in a WS plasma.