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

Ide, Shunsuke; Takenaga, Hidenobu; Isayama, Akihiko; Sakamoto, Yoshiteru; Yoshida, Maiko; Gormezano, C.*; JT-60 Team

Impact of an electron cyclotron range of frequency (ECRF) wave on the internal transport barriers (ITBs) in a weak shear (WS) plasma has been investigated in JT-60U. It has been observed that the ITB in the ion temperature (Ti ITB) in a WS plasma can be degraded by an EC injection. It is clarified for the first time that the degradation effect depends increasingly on the EC power (PEC) but decreasingly with plasma current (Ip). Moreover it was confirmed that an EC injection affects the toroidal rotation profile (Vt (r)) indirectly and results in flattening of Vt (r) regardless to the direction of the target Vt (r) peaking, co- (relative to the Ip direction) or counter. Furthermore, it was newly found that the central Ti and Vt are affected with no delay from the EC onset even by an off-axis EC injection. These results suggest that an EC injection acts on background mechanism that has special structure, and EC deposition in any location in this structure gives instantaneous effect.