Helium-dislocation interaction in aluminium

Helium-dislocation interaction during the isochronal annealing of high ener gy He-implanted aluminium is studied using positron annihilation techniques . While helium is strongly trapped by the dislocations, the binding appears not to be strong enough to delay the annealing stages significantly. The n ucleation of helium bubbles is delayed but the helium atoms do not hold the dislocations stable against annealing. The estimation of the helium bubble parameters was carried out taking into consideration the expansion of the lattice during the annealing and the bubble pressure is higher than that at room temperature, as expected. A polynomial relation is obtained between t he helium melting temperature and the helium atom density. The bubbles are highly overpressurized and could serve as ideal systems for exploring the S imon-Glatzel transition expected at low temperatures.