Pre-irradiation effect on deuterium retention after high-flux plasma exposure at two temperatures

The effects of 3.5 MeV iron (Fe¹³⁺) ions pre-irradiation on deuterium (D) retention and blistering in recrystallized tungsten were investigated after exposure to low-energy (40 eV) and high-flux (1.8 × 10²² D m⁻² s⁻¹) D plasma at two temperatures (480 K and 630 K) with the high fluence of 2.6 × 10²⁶ m⁻². Surface observations showed a high density of small intragranular blisters on the pristine sample and sparse blisters on pre-irradiated samples at 480 K exposure, while severe surface blisters with maximum sizes reaching several tens of micrometers are present on both pristine and pre-irradiated samples at 630 K exposure. Thermal desorption spectra (TDS) of D indicate different types and amounts of D traps formed in the target sample between the two plasma exposures. Additional high-temperature desorption peaks located above 950 K are present in the TDS of both pristine and pre-irradiated samples at 630 K exposure. Large vacancy clusters are supposed to be trapping sites for the high-temperature desorbed D, and they are most likely the result of the evolution of blistering-induced defects. Total D retention calculation indicates that the pre-irradiation enhances D retention at 480 K exposure, but reduces it at 630 K exposure, suggesting a reversal of the enhancement effect at the higher temperature of 630 K. Since the high-temperature desorption region (900–1100 K) accounts for approximately 80 % of the total D retention—and D desorption in this region is higher in the pristine sample—the reversed enhancement effect is primarily attributed to the source of the high-temperature desorption, namely, large vacancy clusters formed by the evolution of blistering-induced defects. This interpretation is supported by blistering observations, where pre-irradiation suppressed surface blistering and thereby reduced associated defects and large vacancy clusters. This work further reveals the complex influence of pre-irradiation on D behavior in tungsten.