Effect of W-Cu joining on D transport behavior in plasma-facing components for fusion reactors

In future fusion reactors, W-Cu joining technology will be utilized to fabricate plasma facing components. In this study, hydrogen isotope gas-driven permeation (GDP) and thermal desorption spectrometry (TDS) are performed for W-Cu, W and Cu samples to understand the impact of W-Cu joining on fuel transport. GDP results reveal that the diffusion activation energy of the W-Cu sample is 0.289 eV, significantly smaller than that of the reference sample. Compared with the reference sample, the deuterium (D) retention in the W-Cu sample is doubled. High resolution transmission electron microscope (HRTEM) images indicate the presence of a mixed region of about 20 nm at the W-Cu interface, with a dislocation density in this region of 7.38×1016 m-2, three orders of magnitude higher than that in W and Cu. Simultaneously, energy dispersive spectrometer (EDS) data show that significant oxygen (O) impurities within the mixed region. Results from first principles simulations suggest that the presence of O at the interface can significantly alter the formation energy of H. The mixed layer not only serves as a diffusion barrier but also has the capacity to capture D. The presence of a high number of dislocations and O impurities in the mixed layer greatly impacts D transport in the W-Cu component.