Deuterium retention and removal in liquid lithium determined by in-situ NRA in Magnum-PSI

In this work, Li-filled 3D-printed porous tungsten samples were exposed to deuterium (D) plasma in Magnum-PSI with a wide ion flux from 4×1022 to 1.5×1024 m-2s-1 and with a corresponding wide temperature range from below Li melting point (180.5 °C) to above Li deuteride (LiD) melting point (~ 690 °C). The formation, decomposition and melting of LiD have been directly observed in the experiment via infra-red thermometry and visually post-mortem while still in vacuo, and correlated to the D retained content. The LiD formation was characterized by a solid precipitate layer formed on the surface with high emissivity (0.6 ~ 0.9) characterized by a blue or dark blue colour after exposure. The melting of Li-LiD layer was found to occur close to the temperature predicted by Li-LiD phase diagram. In-situ Nuclear Reaction Analysis (NRA) was applied to perform the measurement of D retained in Li samples immediately after exposure without breaking the vacuum. D depth profiles were determined by NRA, in which the highest D concentration (15 – 45 at.%) was found in the top several micrometers and decreases with depth to low levels (