Statistical analysis to the SOL plasma fluctuation in JT-60U

Intermittent events and their temporal scale were studied in the L-mode SOL plasma by applying statistical analysis of probability distribution function and conditional average to js and Vf measured with the Mach probes at the HFS and LFS. Fluctuation level was large (20–70%) at the LFS midplane, compared to those near the X-point (4–20%) and the HFS SOL (4–10%). ‘Burst events’ were measured mostly at the LFS midplane, where positive skewness (S = 0.3–0.8) extended from the separatrix to the far SOL (rmid < 10 cm). Time scale of the ‘burst events’ was short (∼5 μs). When the divertor plasma was detached up to the vicinity of the X-point, large ‘burst events’ characterized by S ∼ 1.8 and long time scale of 40–80 μs occurred in the outer SOL near the X-point (0.5 < rmid < 1.5 cm). The large ‘burst events’ can therefore be considered as a candidate mechanism to enhance the radial transport and SOL flow in the divertor.