Obervation of Flow Reversal in SOL Plasmas
Utilizing a set of scanning Mach probes on the midplane and electro-static probes on the divertor region and on the diveror target plates situated as shown in Fig.1, the plasma ion flow in the scrape-off layer (SOL) has been studied in JT-60U since last January.
Although the SOL flow is widely believed to be pointed at the divertor target plates, it has been found that the direction of SOL flow between the divertor and the main SOL regions is revered in most discharges as shown in Fig. 2. This suggestes that there is a stagnation point of the flow between the two regions.
Directions of the SOL flow should have large impacts on impurity transport along the SOL, particle flux in the divertor, divertor pumping capability. To resolve the machanisms of the flow in detail, further experiment and analysis are ongoing in JT-60U.
