Mechanisms of retention and blistering in near-surface region of tungsten exposed to high flux deuterium plasmas of tens of eV

The mechanisms of hydrogen retention and blistering in tungsten exposed to high flux deuterium plasmas of tens of eV were studied with a variety of techniques, such as TEM/SEM and TDS. Cross-sectional TEM observations showed that small blisters with diameters around 30 nm and microcracks formed in the near-surface region before the formation of larger blisters with diameters up to a few microns (comparable to grain sizes). The TDS results indicated that deuterium mainly existed in the molecular form in tungsten after the plasma exposure. These results suggest that crystal defects like vacancies could be generated by the intrusion of a large number of hydrogen isotope atoms in the near-surface region of tungsten.