Modeling of tungsten erosion and diffusion in the limiter and ramp-up phases of DTT tokamak with the ERO code

The interaction between plasma and plasma-facing components (PFCs) such as the first wall and the divertor can in general strongly influence the plasma performance. This is particularly relevant when the PFCs are made of tungsten as in DTT [1] and also during limiter and ramp-up phases when the plasma boundary is in direct contact or very close to the first wall. To study these conditions and quantify possible plasma contamination, the plasma was first modeled during the limiter and ramp-up phases with the ASTRA code, in the confined region, and, across the separatrix and in the SOL, with SOLEDGE2D. The possible effect of intrinsic impurities such as oxygen was also considered by including in the edge modeling a source of oxygen from the first wall at locations of strong plasma-wall interaction. Uncertainty in the edge heat flux decay length was also considered in edge modeling using different transport values. The resulting plasma was then used in the ERO2.0 3D code to study W erosion and subsequent diffusion to the plasma core. ERO modeling was performed with different first wall implementations varying from a toroidally symmetric one to one with a small number of poloidal limiters on the inner side of the torus.

The results indicate that with higher transport (long heat flux decay length) the resulting plasma contamination is low but may increase unacceptably for lower edge transport. The shape of the plasma wall also appears to influence the resulting contamination of the core with a higher W concentration in case of a reduced number of limiters.