Driving mechanism of sol plasma flow and effects on the divertor performance in JT-60U

Asakura, Nobuyuki; Takenaga, Hidenobu; Sakurai, Shinji; Porter, G. D.*; Rognlien, T. D.*; Rensink, M. E.*; Shimizu, Katsuhiro; Higashijima, Satoru; Kubo, Hirotaka

The measurements of the SOL flow and plasma profiles both at the high-field-side (HFS) and low-field-side (LFS), for the first time, found out the SOL flow pattern and its driving mechanism. "Flow reversal" was found near the HFS and LFS separatrix of the main plasma for the ion ▽B drift direction towards the divertor. Radial profiles of the SOL flow were similar to those calculated numerically using the UEDGE code with the plasma drifts included although Mach numbers in measurements were faster than those obtained numerically. Particle fluxes towards the HFS and LFS divertors produced by the parallel SOL flow and ErB drift flow were evaluated. The particle flux for the case of intense gas puff and divertor pump (puff and pump) was investigated, and it was found that both flow velocity and collisionality were enhanced, in particular, at HFS SOL. Drift flux in the private flux region was also evaluated, and important physics issues for the divertor design and operation, such as in-out asymmetries of the heat and particle fluxes, and control of impurity ions were investigated.