Deuterium plasma flow in the scrape-off layer of ASDEX Upgrade

Measurements of the plasma flow parallel to the magnetic field in the scrape-off layer (SOL) of ASDEX Upgrade were performed using Mach probes. The parallel flow was studied at various densities in L- and H-mode discharges with lower and upper single null configuration applying normal and reversed toroidal field. Two reciprocating probes allow for flow measurements in the outer midplane and in front of the lower divertor, slightly below the X-point, covering the inner and outer divertor leg. Strong parallel flows were observed with Mach numbers of up to 0.6 in the outer midplane and even larger than 1.0 above the divertor. Such a flow can connect the particle loss of the confined plasma predominantly happening on the torus outside to the strong recycling observed at the torus inside. The plasma flow varies with plasma density and ion drift direction.