Deuterium Retention in the Near-Surface Layer of W Single Crystal Irradiated with 6 keV Deuterium Ions
The D retention in W (100) single crystal irradiated with 6 keV deuterium ions up to a fluence of 1 × 1022 D/m2 at temperatures of 300, 430 and 480 K has been studied by TDS. Moreover, the structural evaluation of D irradiated W with depth has been investigated by using X-ray diffraction technique. The obtained results show that the retention curve of implanted deuterium deviates from the line of 100 trapping at RT. Almost all (about 99 ) trapped deuterium was accumulated in the near-surface layer with a thickness less than 0.25 μm at an average D concentration of about 5 at.%. No changes (within ±10%) of retained D for a long holding time (more than 600 h) between the irradiation and TDS experiments was observed. Increasing the temperature of the irradiated target from 300 to 430 K leads to a decrease of the amount of trapped D by a factor of about 30. The retention of D at 480 K and the fluence of 1 × 1022 D/m2 was below the detection limit of 2.5 × 1018 D/m2. The structural analysis has shown that during the irradiation at 300 K mainly vacancy type defects (vacancy clusters and cavities) in the near surface layer (∼0.5 μm) and interstitial type defects (dislocation loops) within a layer of a ∼2 μm were formed.