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 10 21 C + /m 2 and 10 22 C + /m 2 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 10 21 C + /m 2 at 300 K followed by 1.5 keV D + 3 implantations to <10 23 D + /m 2 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, ≥10 24 D + /m 2 , the retention values were equivalent to those of D + on pure tungsten. For C + implantations to 10 21 C + /m 2 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 (10 22 C + /m 2 ) resulted in D retention values higher than in pure W for D - fluences < 10 23 D + /m 2 . 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.