EUROFER as wall material: Reduced sputtering yields due to W surface enrichment

For temperatures below 180 °C the erosion yield of EUROFER was lower than for pure Fe already at the lowest fluence of 3 × 1023 D+ m−2, and decreased further to values of less than 1/10 of those for Fe at 6 × 1025 D+ m−2. Ion beam analysis showed the enrichment of W at the exposed surface correlating with the yield reduction; however, the experimental depth resolution of about 1 nm did not allow resolving the predicted W enrichment within the first two monolayers. Therefore, it remains unclear whether the W enrichment is the only reason for the yield reduction or if surface oxidation and topography changes contribute to the observed effects. First results for different surface temperatures, however, indicated that at 500 °C the erosion yield remains close to the values for pure Fe, indicating that the exposure temperature is also an important factor for the sputtering process of EUROFER.