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Two reciprocating probe systems, in the same poloidal position at the top of the JET torus but toroidally separated by 180 o , have been used to measure parallel flow in the Scrape-Off Layer (SOL). One system uses the entrance slit plates of a Retarding Field Analyser (RFA) to record upstream and downstream flux densities, and the second system uses two pins of a nine pin Turbulent Transport Probe, (TTP). Measurements have been made in both forward and reverse field directions.Results from both systems are similar.In the forward field direction, that is with B r ∇ drifts downward towards the divertor, there is a strong parallel flow in the direction outer to inner divertor. The flow generally has a low value, Mach number M~0.2, close to the separatrix and rises in the region of high magnetic shear close to the separatrix to a maximum of M~0.5 some 20mm outside of the separatrix. The flow in the reverse field direction is small, close to zero, and generally is again in the same direction as that for forward field close to the separatrix, with M~0.2. Code results using EDGE2D with drifts suggested an almost symmetrical flow about zero when the field direction was changed in an earlier work, [1]. However, this was for particularly low density, high temperature edge conditions, and the predicted symmetry is not evident for more usual edge conditions, reported here. Experimentally, the flow is found to be quite asymmetric about zero, particularly at high density. There is some symmetry in flow, but about an offset value of M~0.2. The form of M(r) is similar to experiment but the major code result is the low value of M generally < 0.1. The effect of gas (deuterium) and impurity (carbon) puffing in the code has been investigated. We are unable to say why the magnitude of M(r) from experimental data and codes do not agree. However, results presented in this paper suggest that the probe itself may be exhibiting an influence on the magnitude of the flow as measured in the SOL.

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