Deuterium concentration in deposited carbon layers in Tore Supra

Deposited carbon layers observed in the tokamak Tore Supra have been sampled in order to quantify their deuterium content using D( 3 He, p) 4 He nuclear reaction analysis. The results show two trends: the D/C ratio in wetted deposited carbon layers is less than 1% and the D concentration depth profile decreases rapidly from the first micrometers of the plasma facing sub-surface to the rear surface, while the D/C ratio in shadowed deposited carbon layers reaches about 10% and shows a more constant profile along the probed depth. Using the information about D concentrations and of the maximum thickness of the different samples and with the estimated deposited areas, an estimated D inventory is found to be about 1 x 10 23 D, which is too low to account for the D retention expected for a whole long plasma discharge campaign.