Sputtering of EUROFER: The Role of Roughness

The lifetime of a plasma-facing component is determined by sputtering due to the bombardment with energetic particles. At the first wall, the impinging particle flux is dominated by charge-exchange neutral hydrogen isotopes with energies below about 200 eV, but comprising also small fractions of high-energy species with energies up to several keV. RAFM steels contain small amounts of tungsten. Upon exposure to energetic hydrogen ions from the plasma, a W-enriched layer will be formed at the surface due to preferential sputtering. Such a W-enriched layer could lower the erosion rate to acceptable levels. We report on simulations and experiments aiming at quantifying the achievable reduction of erosion rates. In particular, we want to study the influence of surface roughening on sputtering.