Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5467580 | Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms | 2017 | 7 Pages |
Pure tungsten samples were irradiated to 1.0Â ÃÂ 1016, 5.0Â ÃÂ 1016 and 1.0Â ÃÂ 1017Â ions/cm2 at room temperature with 500 and 200Â keV helium ions, respectively, to understand the growth of vacancy like defects in tungsten induced by helium irradiation. The doppler broadening spectroscopy of slow positron annihilation was used to characterize the behavior of vacancy like defects, such as HeliumnVacancym (i.e. HenVm) complexes, induced by He irradiation. When the irradiation fluence is below 1.0Â ÃÂ 1017Â ions/cm2, the size and density of vacancy like defects show increasing trends with increasing fluences. The density of vacancy like defects decreases with increasing depths due to the increasing amounts or n/m ratios in HenVm complexes. When the ratios reach certain values, the size of vacancy like defects increases. When the 200Â keV He irradiation fluence increases to 1.0Â ÃÂ 1017Â ions/cm2, the size of vacancy like defects decreases. When the 500Â keV He irradiation fluence increases to 1.0Â ÃÂ 1017Â ions/cm2, the size and density of vacancy like defects grow larger. The formation and evolution of irradiation induced defects and the growth mechanism of HenVm complexes are discussed in this paper on the bases of dpa levels, He concentrations, CHe/dpa ratios and electronic energy loss depositions.