Temperature dependence of surface morphology and deuterium retention in polycrystalline ITER-grade tungsten exposed to low-energy, high-flux D plasma

Surface topography and deuterium retention in polycrystalline ITER-grade tungsten have been examined after exposure to a low-energy (38 eV/D), high-flux (1022 D/m2 s) deuterium plasma with ion fluences of 1026 and 1027 D/m2 at various temperatures. The methods used were scanning electron microscopy equipped with focused ion beam, thermal desorption spectroscopy, and the D(3He,p) 4He nuclear reaction at 3He energies varied from 0.69 to 4.0 MeV. During exposure to the D plasma at temperatures in the range from 320 to 815 K, small blisters of size in the range from 0.2 to 5 μm, depending on the exposure temperature and ion fluence, are formed on the W surface. At an ion fluence of 1027 D/m2, the deuterium retention increases with the exposure temperature, reaching its maximum value of about 1022 D/m2 at 500 K, and then decreases below 1019 D/m2 at 800 K.