New measurements of high-field side (HFS) scrape-off layer (SOL) flows were conducted in AS-DEX Upgrade by Doppler spectroscopy of injected N impurities. N 2 was injected into the plasma 13 cm above the HFS midplane during similar low-density L-mode discharges. The emission of N was observed both toroidally and poloidally at different radial locations by the HFS edge CXRS system. The flow velocities were determined from the Doppler shift of selected N(II) and N(III) lines within 460-465 nm. The results show migration of impurities towards the lower HFS divertor at the separatrix and away from it in the near SOL, the reversal being most probably driven by the perpendicular E × B drift. The results also suggest only partial equilibration of the N + ions with the background flow. Hence, the background D flow velocity cannot be directly determined from the measured N flows but has to be addressed by modelling of the injection experiment.
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