ELM propagation in the low- and high-field-side Scrape-off Layer of the JT-60U tokamak

Asakura, Nobuyuki; Kawashima, Hisato; Ono, Noriyasu*; Matsunaga, Go; Nakano, Tomohide; Oyama, Naoyuki

In JT-60U, the filament structure was measured at three poloidal locations, and its time evolution were investigated at the inner (high-field-side) SOL as well as outer (low-field-side) SOL. At the inner SOL, filament structure with 7-8 multi-peaks was, for the first time, determined only close to sepatratrix. Delay of the first peak after start of MHD activity was faster than characteristic time of the parallel convection from the outer midplane, and Mach numbers reached ion sonic level. These results show that ELM filaments extend from outer to inner plasma edge, and a part of the filaments are exhausted to the inner SOL. Toroidal mode number (n) and size of the filament (dz) were evaluated from the interval of the multi-peaks and duration of each peak: n 15-25 and dz 2-4 cm at the HFS SOL, and n was smaller than and dz was comparable to those at the LFS SOL. After the multi-peak appearance, flow reversal of SOL plasma was generated over wide region of the inner SOL.