Spectroscopic investigation of the dynamics of ions and neutrals in the ASDEX Upgrade Divertor II

Detachment at the separatrix is a promising possibility to reduce the peak power load onto the divertor target plates. We investigated this topic spec troscopically at ASDEX Upgrade by measuring particle velocities using Doppl er spectroscopy. The experimental data show a reduction of the chord averag ed hydrogen velocity along the separatrix by about a factor of 3. Another i mportant subject is flow reversal: after a brief discussion of 2D-code pred ictions and the conditions for detection we present spectroscopic evidence for flow reversal of Cf-ions in the ASDEX Upgrade divertor II. The comparis on of these spectroscopic data with B2-EIRENE modeling shows good qualitati ve and quantitative agreement. (C) 1999 Elsevier Science B.V. All rights re served.