Effects of cascade damages on the dynamical behavior of helium bubbles in Cu

Effects of cascade damage on the behavior of helium bubbles in copper have been studied. To examine the dynamical response of the helium bubbles to irradiation with high energy self ions, in situ TEM observations during irradiation with 400 keV Cu+ at room temperature and 830 K were carried out. Intermittent motion of bubbles of a few nm was observed at room temperature where the bubble was thermally immobile. At high temperature, in addition to Brownian type motions, rapid motion of rather long distances of about 10 nm was observed. The detailed analysis of the frequency and distance of these motions suggested the direct interaction of helium bubbles with sub-cascades and secondary defects.