Impact of plastic deformation on plasma induced damage and deuterium retention in tungsten

Recent theoretical and subsequent experimental studies suggest that the uptake and release of deuterium (D) in tungsten (W) under high flux ITER-relevant plasma exposure is controlled by dislocation microstructure. Thanks to numerical calculations, a comprehensive mechanism for the nucleation and growth of D bubbles on dislocation network was proposed. The process of bubble nucleation can be described as D atom trapping at a dislocation line, its in-core migration, the coalescence of several D atoms into a multiple cluster eventually transforming into a nano-bubble. This view implies that the initial microstructure might be crucial for D uptake and degradation of the sub-surface layer under prolonged plasma exposure. In this work, we apply several experimental techniques to investigate the microstructure and mechanical properties of surface and sub-surface layer of W in recrystallized and plastically-deformed condition exposed to the high flux plasma. We use transmission and scanning electron microscopy, thermal desorption spectroscopy as well as nano-indentation measurements.