Modeling of beryllium-carbon dynamics in the ITER divertor region

One of the main materials issues present in the ITER current design is the formation of mixed materials in the divertor region. Presently, the component where most of the energy is deposited in the ITER divertor are the vertical inboard and outboard plates, which are to be manufactured with composite carbon fiber (CFC) according to the latest design. The first wall, on the other hand, has beryllium as the plasma-exposed material. Some beryllium eroded from the first wall is able to find its way into the divertor region, where it can strike the carbon plates and get implanted or deposited. The presence of beryllium in the divertor has the negative effect of enhancing tritium trapping via co deposition, hence reducing the net available fuel for the reactor. In this study, the dynamic composition of a carbon target subject to bombardment by deuterium, tritium and beryllium with ITER-like fluxes and energies is studied. The effect of carbon and beryllium redeposition on the target compositional and erosion behavior is studied as well. Simulation results show that both the partial sputtering of beryllium and carbon atoms as well as the energy distributions play an important role in beryllium accumulation on the vertical target plate. As a benchmark, conditions similar to those encountered in the PISCES facility are modeled and compared to the experimental results. Therefore discrepancies between the model and the experiment will be discussed in the context of chemical and morphological state evolution of the beryllium-deposited carbon surface.