Deuterium retention in MeV self-implanted tungsten: Influence of damaging dose rate

Highlights: • Widely used setup for tungsten self-damaging at IPP Garching is explained in detail. • Average damage dose rate for W self-implantation is varied by three orders of magnitude, peak damage dose rate by factor of five. • No effect on D retention is observed – neither at room temperature nor at 800 K where defect evolution is substantial. • As damaging rates by fusion neutrons in future fusion devices will be even smaller and hence timescale between events larger no effect of the lower damage rates on D retention in a future reactor is to be expected. - Abstract: Recrystallized, polycrystalline tungsten was self-damaged by 20 MeV tungsten ions up to a calculated damage dose in the damage peak of 0.23 dpa. The time to acquire this dose and hence the average damaging dose rate was varied from 6 × 10^-3 to 4 × 10^-6 dpa/s, the latter coming close to the damage dose rate expected from fusion neutrons in future devices such as ITER and DEMO. One series was conducted at 295 K and one at 800 K to check for possible effects of defect evolution at elevated temperature. The created damage was decorated afterwards with a deuterium plasma at low ion energy of 19 D/m² until saturation to derive a measure for the defect density that can retain hydrogen isotopes. ³He nuclear reaction analysis (NRA) was applied to derive the deuterium depth profile and the maximum concentration in the damage peak. Neither for the 295 K nor for the 800 K series a variation in deuterium retention with damage dose rate was found.