The Effect of Pre-irradiation on Deuterium Retention and Desorption Behavior in Tungsten and Tungsten Alloys

The D retention and desorption behaviors were studied using Thermal desorption Spectroscopy (TDS), Doppler-broadening Spectroscopy (DBS) of Positron Annihilation, Transmission Electron Microscopy (TEM), and Scanning Electron Microscopy (SEM). SRIM simulations were also conducted to model the defect and D atom distributions in the materials. [Results] Fe13+ ion irradiation induced significant vacancy-type defects in both materials, with higher defect concentrations in pure W compared to the alloy.

D retention was observed to be higher in pure W, with desorption occurring at approximately 250°C and 700°C. In contrast, the 97W-2Ni-1Fe alloy showed reduced D retention, with desorption peaks at 200°C and 700°C. The TDS results revealed that pure W retained 2-3 times more D than the alloy. Pre-irradiation with Fe13+ ions further enhanced D retention, especially in pure W, where more D bubbles formed. TEM analysis confirmed the formation of D bubbles in the defect regions, especially under high-dose irradiation.

[Conclusions] The 97W-2Ni-1Fe alloy demonstrates superior performance in minimizing D retention, with significantly lower D desorption and reduced bubble formation compared to pure W. The TDS results show that pure W retains 2-3 times more D than the 97W-2Ni-1Fe alloy, indicating that the alloy's defect structure and composition contribute to its lower D retention. TEM analysis further confirms that the alloy exhibits fewer D bubbles and less damage, particularly in the form of less D bubble formation during irradiation and plasma exposure.

These findings suggest that the 97W-2Ni-1Fe alloy is a more favorable material for applications where minimizing D retention and associated damage is critical, such as in fusion reactors. The results highlight the importance of material composition and defect structure in controlling D behavior under irradiation and plasma conditions, offering valuable insights into the design of next-generation plasma-facing materials.