Effect of carbon pre-implantation on deuterium retention in tungsten

The effect of pre-implanted carbon on deuterium retention in tungsten was investigated using polycrystalline tungsten foils. Pre-implantation was performed with 1 keV C+ ions to fluences of 1021 C+/m2 and 1022 C+/m2 at 300 and 500 K. Using this newly created W/C structure, a deuterium retention study with 1.5 keV D+3 (500 eV/D+) ions was performed as a function of incident D+ fluence and implantation temperature. For 1 keV C+ implantations to 1021 C+/m2 at 300 K followed by 1.5 keV D+3 implantations to <1023D+/m2 at 300 and 500 K, the amount of D retained was reduced by an order of magnitude compared with W specimens without a C+ pre-implantation. At higher D+fluences, ⩾1024 D+/m2, the retention values were equivalent to those of D+ on pure tungsten. For C+ implantations to 1021 C+/m2 at 500 K, the amount of D retained tended to follow the behaviour of the pure W case. Carbon pre-implantations to a higher fluence (1022 C+/m2) resulted in D retention values higher than in pure W for D+ fluences <1023 D+/m2. At higher D+ fluences, the retention behaviour differed significantly, depending on the D+ implantation temperature. A possible mechanism is suggested to explain the observed results.