‘Mixed-material evolution analysis of the ITER divertor’

Evolution of the ITER outer divertor target surface is analyzed for the case of wall-sputtered beryllium transported to an initially tungsten divertor. Coupled codes for the convective edge plasma, impurity transport, and mixed-surface sputtering, give the wall-source beryllium flux to the divertor, the sputtering erosion/redeposition response, and the resulting beryllium surface content/growth. The analysis shows zero net Be growth over most (∼80%) of the divertor, due to high re-sputtering and reflection—with an equilibrium Be/W surface quickly formed (∼10 s)—but with a region near the strike point having substantial (∼1 nm/s) growth.