Speaker
Description
W is a candidate material for plasma-facing components but is also being considered as a liquid metal corrosion barrier in the breeder blanket of future fusion devices. In both scenarios, the W will be exposed to tritium. Radioactive tritium inventory must be controlled to ensure safe, fuel-efficient powerplant operation; it is essential to understand hydrogen isotope trapping and transport in W.
Deuterium inventory can be quantified using techniques such as thermal desorption spectroscopy (TDS), and information about the types of deuterium trap sites present can be obtained from the TDS spectra through complementary first principles modelling. However, spatial mapping of hydrogen isotopes on length-scales comparable to nanoscale trap sites is challenging since it is difficult to detect low hydrogen concentrations and resolve hydrogen isotopes with most established microscopy techniques.
This work uses atom probe tomography (APT) to map deuterium within ion irradiated and unirradiated W on the nanoscale. Deuterium was introduced through exposure of bulk samples to low-energy deuterium plasma. APT-measured deuterium depth profiles show co-location of deuterium and oxygen. C/O/N clustering is observed, but with no deuterium co-segregation.
Deuterium-grain boundary interactions are revealed in the atom maps of the fine-grained, unirradiated W sample. Experimental observations are complemented by first principles modelling to understand the role of irradiation-induced and as-received defects in trapping and transport of hydrogen isotopes in W and W oxides.
