Effects of tungsten on thermal desorption of helium from Fe–9Cr–2W ferritic alloy irradiated with low energy helium ions

Thermal desorption of helium gas atoms from Fe–9Cr–2W ferritic alloy which was irradiated with 5 keV He+ ions has been studied, particularly to extract tungsten effects, by Thermal Desorption Spectroscopy (TDS) at temperatures from room temperature to 1370 K. Three small peaks (peaks I, II, III) and three large peaks (peaks IV, V, VI) appeared, and dependence of these peaks on the irradiation temperature and fluence has been demonstrated. The small peaks I, II and III have been related to the release of helium atoms by shrinkage or glide of different size dislocation loops. The large peaks have been attributed to release of helium gas atoms by migration of different size bubbles to the specimen surface. In comparison with TDS spectra in Fe–9Cr, these large peaks have been found to shift to higher temperatures. The present results suggest that tungsten atoms precipitated on the bubble surface could retard the bubble migration.