Preferential sputtering induced Cr-Diffusion during plasma exposure of WCrY smart alloys

WCrY Smart Alloys are developed as first wall material of future fusion devices such as DEMO. They aim at behaving like pure W during plasma operation due to depletion of the alloying elements Cr and Y. The Cr concentration gradients induced by preferential plasma sputtering cause Cr-diffusion. The exposure of WCrY and W samples to pure D plasma, with a plasma ion energy of 220eV, is simulated using the dynamic version of SDTrimSP. Cr-diffusion is included into the model. Simulation results are compared with experimental results. At sample temperatures of more than 600∘C and sputtering by D plus residual oxygen in the plasma ion flux, the Cr-transport to the surface leads to enhanced erosion for WCrY samples. A diffusion coefficient for Cr in WCrY of the order of 1⋅10−17m2/s is determined. The suitability of WCrY as first wall armour and the influence of further effects, considering especially Cr-diffusion, is discussed.