Conclusions about the use of tungsten in the divertor of ASDEX Upgrade

Tungsten divertor plates have been used in ASDEX Upgrade for a full experimental campaign of approximately 800 discharges. Key issues investigated were the plasma performance, tungsten erosion, redeposition and migration, hydrogen isotope retention and the consequences of the simultaneous use of carbon and tungsten as plasma facing materials. Tungsten behavior was investigated by spectroscopic observation of line and quasi-continuum radiation and by surface analysis of material probes and of samples taken from plasma facing components after the experimental campaign. Code simulations were used to gain further understanding of the observed tungsten erosion properties and of tungsten plasma transport processes. The results obtained so far are presented and the implications with respect to the construction of future fusion devices are discussed.