Field ion microscopy of 180-230 keV Xe+ion damage in tungsten

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Abstract
Field ion microscopy was used in order to study the radiation damage structure in tungsten after heavy ion bombardment. Thin needle seecimens of tungsten were irradiated with 180 keV Xe− ions at liquid nitrogen temperature (∼ 80 K) in situ in the field ion microscope (FIM), or at room temperature with 230 Xe+ ions in an alternate vacuum system. All irradiated specimens were subsequently examined by FIM at 80 K by the pulse field evaporation technique. Some of the irradiated samples were, after FIM investigation, warmed to room temperature and then reanalysed at 80 K. The irradiation doses varied between 2×1011 and 4×1012 ions/cm2. Detailed investigation of damage structure was made in areas close to {222}, {233}, {433}, and {411} poles since these regions possess atomic resolution. The observed radiation damage could be classified, as: (1) Small vacancy clusters with 1 to 15 vacancies; (2) Larger vacancy clusters with more than 15 vacancies. No self-interstitial atoms (SIAs) or their clusters were found. The influence on the appearance of defects of crystallinity, temperature and energy of primary recoiled atoms is discussed.