Impact of charge exchange neutrals on plasma facing components of Tore Supra

The inner vessel of a tokamak is submitted to high particle fluxes bombardment, resulting in a contamination of the core plasma and in a limited lifetime for the plasma facing components. In the Tore Supra tokamak, a major upgrade in terms of power exhaust and pulse length, called the CIEL project, is taking place (power coupled to the plasma up to 25 MW, pulse duration up to 1000 s). In this paper, the effect of charge exchange neutrals on the stainless steel protection panels covering the inner vessel is investigated in the CIEL configuration. Based upon simulations of full power CIEL discharges by a neutral transport code, it is found that erosion by charge exchange neutrals might lead to the contamination of the plasma by heavy impurities. Therefore, various methods allowing to shield the protection panels from the charge exchange neutrals, such as carbonisation, boronisation, B4C coating, are discussed.