Effect of toroidal field ripple and toroidal rotation on H-mode performance and ELM characteristics in JET/JT-60U similarity experiments

Oyama, Naoyuki; Saibene, G.*; Kamada, Yutaka; Kamiya, Kensaku; Loarte, A.*; Lnnroth, J.*; Parail, V.*; Sakamoto, Yoshiteru; Salmi, A.*; Sartori, R.*; Shinohara, Koji; Takenaga, Hidenobu; Urano, Hajime; de Vries, P.*; Yoshida, Maiko; JT-60 Team; JET-EFDA Contributors*

The effect of the toroidal field ripple and the edge toroidal rotation on H-mode and pedestal performance as well as ELM characteristics are investigated both in JET and JT-60U. In JT-60U, the amplitude of TF ripple was reduced from 1.2 % to 0.5 % after the installation of ferritic steel tiles. In JET, the ripple amplitude can actively be varied. In both devices, edge rotation in the same direction to the plasma current was reduced with increasing the ripple amplitude. Even at the same amplitude of 0.5 %, the achievable edge rotation in JT-60U was still lower than that in JET. A series of power and density scans performed at several ripple amplitude indicated that plasmas with smaller ripple amplitude and/or larger co-rotation are favorable to achieve higher pedestal pressure and plasma confinement in both devices. As for ELM characteristics, larger co-rotation seems to increase the ELM energy loss together with the reduction of the ELM frequency.