Abstract
High-energy (260keV) He+ pre-damaged and undamaged polycrystalline tungsten samples were irradiated with low-energy (220eV) and high-flux (∼1021ions/m2s) He+ at a sample temperature of 873K to a fluence of 1.0×1025ions/m2. Microscopic evolution of these samples was carried out using non-destructive conductive atomic force microscopy and a nanohardness test. Analysis indicates that a large number of nanometer-sized protuberances of irradiated tungsten samples results from over-high internal pressure of nanometer-sized helium bubbles. Ordered and nanostructured helium bubbles with the same diameter and average spacing can be formed due to the self-trapping and self-organizing of helium atoms in the tungsten materials. In the case of pre-damaged, low-energy He+ irradiation results in a random distribution of nanostructured helium bubbles, indicating that high-energy He+ implantation results in serious irradiation damage of tungsten materials, acting as nuclei for helium bubbles.
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