The evolution of He bubbles was monitored by means of  in situ  electron microscopy during 400keV Ar-ion bombardment at 500K. The bubbles were produced by the implantation of 3keV He ions into pre-thinned samples at 500K, followed by annealing to 670K. During Ar bombardment, the bubbles underwent thermal migration, coalescence and disintegration. The bubbles, after annealing, were under-pressured. However, the Ar bombardment brought the bubbles up to equilibrium pressure after a dose of 0.6dpa. The bubble behavior was explained in terms of their interaction with adjacent cascades. It was proposed that a discrete bubble jump was induced by the melt-zone that formed during the thermal spike phase of a contiguous cascade. The rate of bubble migration was modelled under the assumption that the jump distance was determined by the bubble and cascade volumes.

S.E.Donnelly, R.C.Birtcher, C.Templier, V.Vishnyakov: Physical Review B, 1995, 52[6], 3970-5