Measurements of the flux of metallic impurities to the ASDEX divertor plates

Metal impurity (Fe, Cu) fluxes to the divertor plates of ASDEX were measured using a collector probe during discharges with various plasma parameters. The Cu deposition shows generally a different distribution across the scrape-off layer compared to the Fe deposition. The maximum Cu deposition is close to the Cu divertor plates indicating evaporation or sputtering from these plates. In the center of the SOL, Fe fluxes are indicative of the Fe content in the central plasma. Variations of the Cu and Fe fluxes with auxiliary heating and vessel carbonisation are analysed and discussed in respect of impurity production mechanisms. (orig.)