ELM propagation and fluctuations characteristics in H- and L-mode SOL plasmas on JT-60U

Radial transport of the SOL plasma was recently studied in order to understand heat and particle loading to the first wall. Fast propagation of the ELM plasma and fluctuation properties in H- and L-modes were determined both at high-field-side (HFS) and low-field-side (LFS) SOL using reciprocating Mach probes in JT-60U. Large and short (10-20μs) peaks were found in ELM plasma flux (js) mostly at LFS SOL, which was enhanced after each ELM event (magnetic turbulence). Radial propagation of the first large js peak was determined with velocity of 0.4-3km/s and large decay length of 7.5 cm. Fast heat and particle transport (and deposition) was measured near the separatrix above HFS baffle (Δrmid < 0.4 cm) just after ELM event, producing the flow reversal due to large particle recycling in the HFS divertor. Statistical analysis of a probability distribution function (p.d.f.) was applied to describe intermittent (non-diffusion) transport in SOL plasma fluctuations. It was found that statistical properties were different between ELMy H-mode and L- ode plasmas. In ELMy H-mode, positive skewness (i.e. bursty events) was seen in narrow area near the separatrix (Δrmid < 3 cm) for HFS and LFS SOLs. On the other hand, in L-mode, bursty events were mostly observed at LFS midplain, which extended to the far SOL (Δrmid < 10 cm). (author)