Erosion of tungsten coated tiles on the central column of ASDEX Upgrade

There are plans at ASDEX Upgrade to cover the heat shield of the inner main chamber wall with tungsten coated graphite tiles. Four tiles were installed at different poloidal positions of the heat shield and removed after a full experimental campaign. The tiles were analysed by means of Rutherford backscattering (RBS) analysis before insertion and by both RBS and particle induced X ray emission after removal. This is an investigation of the poloidal and toroidal erosion profiles on the tiles due to sputtering by charge exchange neutral and ion impact.