Determination of the tungsten divertor retention at ASDEX Upgrade using a sublimation probe

Abstract

For the measurement of the divertor retention at ASDEX Upgrade, a sublimation probe has been built with which it is possible to puff metallic impurities into the divertor plasma. This probe offers the opportunity to cross calibrate the influx of the metal with the influx of carbon or oxygen. For the measurement of the divertor retention R, a special deposition probe was used in the main chamber. The value found for R is in good agreement with earlier estimations from long-term deposition probes and computer modelling. The different measurements suggest a propagation of tungsten within the scrape-off layer from the divertor into the main chamber and from there across the separatrix into the confined plasma.