A new loop-punching mechanism for helium bubble growth in tungsten

Growth of helium (He) bubbles with different initial sizes in tungsten (W) has been investigated by performing molecular dynamics simulations. Based on the simulation results a new loop punching mechanism for the large helium bubble growth is proposed. Different from the growth of small-size He bubbles by pushing out self-interstitial atoms and then rearranging into a prismatic dislocation loop, a large-size bubble grows by pushing out a dislocation, subsequently cross-slipping of its screw components and finally evolving into a prismatic dislocation loop. Such dislocations may react with each other to form a dislocation net around the bubble rather than to convert to prismatic dislocation loops.