Retention of ion-implanted deuterium in tungsten pre-irradiated with carbon ions

Deuterium (D) ion implantation and retention at room temperature was studied in pure and carbon (C) implanted tungsten single crystals. Pre-implantation with C was done at 40 keV and D implantation at 10 keV with the range confined in the carbon modified layer and at 100 keV with the range exceeding the carbon modified layer. The range distributions were investigated in situ using 1 MeV He-3 ions analysing the energy distributions of alpha particles from the D(He-3, p)alpha reaction while the total amount of retained D was obtained from the p-integral. The range distribution of carbon was obtained from the backscattered He-3 energy distribution. C pre-impantation influences the D retention only if the range of the D ions is confined within the carbon modified surface layer. In this case, D diffusion beyond the ion range distribution does not occur and the retained D amount is smaller than in the pure W crystal. At D energies exceeding the carbon modified layer the retention occurs in the dislocation zone up to 1 mum and the total retained amount is the same for carbon implanted and pure W samples. (C) 2000 Elsevier Science B.V. All rights reserved.