The effect of High-Temperature Pre-Damage on Vacancy-Type defects and deuterium retention in tungsten

This work investigated tungsten samples that were pre-damaged at room (300 K) and high temperatures (573 and 873 K) using 3.5 MeV iron ions and then exposed to the high-flux deuterium plasma. The vacancy-type defects and the behavior of deuterium retention in the investigated tungsten were characterized and compared to study the effect of high-temperature pre-damage. Results of slow positron annihilation with Doppler broadening spectroscopy indicate the introduction of numerous defects by the room-temperature damage and the formation of larger-sized vacancy clusters by the high-temperature pre-damage. Surface observation demonstrates that the pre-damage at room temperature effectively suppressed the formation of intra-granular blisters, while the pre-damage at high temperature did not exhibit such a significant suppression effect on blister formation. Thermal desorption results show that pre-damage at room temperature significantly increases deuterium desorption. Pre-damage at high temperatures also strengthens deuterium desorption, not as significantly as room-temperature pre-damage, and meanwhile produces additional desorption at around 900 K. These results indicate differences between room-temperature and high-temperature pre-damage in the generation of defects and their impact on deuterium retention. Compared to room-temperature pre-damage, high-temperature predamage tends to generate defects with a larger average size, weakening the suppression effect on deuterium aggregation and blistering within the grains of tungsten, reducing the quantity of deuterium trapping sites and producing higher-energy deuterium traps.