Positron Annihilation Studies On The Nature And Thermal Behaviour Of Irradiation Induced Defects In Tungsten

Positron Annihilation Lifetime Spectroscopy has been performed with a pulsed positron beam to investigate the nature and evolution of implantation-induced defects created in the track region (TR) of 800 keV He-3 ions at different fluences. At high fluence - 5x10(16) cm(-2) - lifetime decomposition exhibits a predominant (98%) positron lifetime of 200 ps which is attributed to irradiation induced monovacancy. The increasing average lifetime as a function of the post-implantation annealing temperature has allowed to identify vacancy clustering due to vacancy migration (that occurs from 473 K). (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim