Influence of Plasma-wall interactions on the behaviour of ELMs in JT-60U

Chankin, A. V.; Asakura, Nobuyuki; Fukuda, Takeshi; Isayama, Akihiko; Itami, Kiyoshi; Kamada, Yutaka; Kubo, Hirotaka; Miura, Yukitoshi; Nakano, Tomohide; Oyama, Naoyuki; Takeji, Satoru; Takenaga, Hidenobu

In JT-60U, extensive plasma-neutral exchange during a typical type I ELM leads to a transient increase in the total number of charged particles in the plasma. The density rise is especially large at the edge, with the increase in the inner vertical interferometer signal (FIR1) of up to 40%, in the case of a giant ELM. Fast measurements of edge plasma density, electron temperature, magnetic fluctuations and Bremsstrahlung emission have been conducted to study the dynamics of the ELM evolution. In order to pinpoint the exact location of the density rise, a dedicated set of experiments with the horizontal plasma sweep to scan the separatrix position at the inner midplane with respect to the FIR1 chord, has been carried out at different wall conditions.