Surface blistering and deuterium retention in tungsten exposed to low-energy deuterium plasma at different temperatures

Surface morphology and deuterium retention in tungsten have been examined after exposure to a low-energy deuterium plasma with an ion fluence of 6.0 × 1024 D/m2 at various temperatures. Optical differential interference contrast microscope and scanning electron microscope equipped with focused ion beam were applied for surface observations. D (3He, p) 4He nuclear reaction at 3He energies varying from 0.5 to 4.5 MeV was used to determine the deuterium depth distributions within the depth of 8.0 μm. The thermal desorption spectroscopy was applied for deuterium retention measurement. The observed surface blistering and deuterium retention are found to strongly depend on the exposure temperature. At 230 K, many small blisters are formed on the tungsten surface. As the exposure temperature increases to 370 K, the blisters become sparser and larger. At 520 K no blisters appear. The deuterium retention is 1.4 × 1020 D/m2 at 230 K. Then it increases to 1.1 × 1021 D/m2 as the exposure temperature rises to 370 K, and decreases to 2.3 × 1020 D/m2 at 520 K.