Main processes of plasma-wall interaction and impurity transport in fusion devices and their impact on the availability of the devices are discussed. According modelling tools, in particular the three-dimensional Monte-Carlo code ERO, are introduced.
The capability of ERO is demonstrated on the example of tungsten erosion and deposition modelling. The dependence of tungsten deposition on plasma temperature and density is studied by simulations with simplified geometry. The amount of deposition increases with increasing electron temperature and density. It is seen that up to 100% of eroded tungsten can be promptly deposited near to the location of erosion at very high densities (~1e14 cm-3). The effect of the sheath characteristics on tungsten prompt deposition is investigated by using PIC data to spatially resolve the plasma parameters inside the sheath. Applying PIC data instead of non-resolved sheath leads in general to smaller tungsten deposition, which is mainly due to a density and temperature decrease towards the surface within the sheath.
Two-dimensional tungsten erosion/deposition simulations, assuming symmetry in toroidal direction, have been carried out for the JET divertor. The simulations reveal, similar to experimental findings, that tungsten erosion is dominated by the intra-ELM phases. Also, the simulated deposition fraction of about 84% in between ELMs is in line with spectroscopic observations from which a lower limit of 50% has been estimated.
Finally, simulations for the linear devices PSI-2 and PISCES-B will be presented. The benchmarking of modelled light emission and erosion/deposition with observations will be illustrated.