Detachment physics in SOLPS simulations

Since the divertor for ITER has been designed to operate in a partially detached mode on the basis of SOLPS calculations, the understanding of the physics of detachment is crucial. The results of SOLPS calculations with fluid and Monte-Carlo neutrals; with pure deuterium and with carbon impurities; with and without drifts; with horizontal and vertical targets; and with and without ELMs will be presented. In addition, the possible role of fast electrons which can be expected to strongly modify the ionization rates without much affecting the recombination rates, will be investigated. Calculations with SOLPS indicate a strong enhancement of the ionization rate in the inner divertor leg by the fast electrons, followed by an enhanced volume recombination of these ions giving rise to an enhanced 'volume recycling'. This can then increase the volumetric losses in the inner divertor region.