Impact of toroidal magnetic field ripple on edge pedestal characteristics in JET and JT-60U

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

The effect of TF ripple on the edge pedestal characteristics are examined in the TF ripple scan experiments in JET and JT-60U. The TF ripple is defined at the separatrix on the outer midplane. By the installation of ferritic inserts (FIs), TF ripple was reduced from to in JT-60U. In JET, TF ripple was varied from to by feeding different currents to the odd and even set of coils. The pedestal pressures in both devices were similar for the variation of TF ripple. The core and edge toroidal rotation clearly decreases in counter direction by increased TF ripple. In JT-60U, by the installation of FIs, the ELM frequency decreased by . In JET, ELM frequency increases only slightly with increased TF ripple. From this inter-machine experiment, TF ripple less than does not strongly affect the pedestal pressure. The effect of TF ripple on pedestal characteristics at lower collisionality close to ITER should be investigated as a next step study.