EFFECT OF ELECTRON-EXCITATION ON RADIATION-DAMAGE IN FCC METALS

Defect production, radiation annealing and defect recovery are studied in several fcc metals (Al, Cu, Ni, Ag and Pt) irradiated with low-ene rgy (approximately 1 MeV) and high-energy (approximately 100 MeV) ions . Irradiation of the metals with strong electron-lattice interaction ( Al, Ni and Pt) by approximately 100 MeV ions causes an anomalous reduc tion, or even a complete disappearance of stage-I recovery. This exper imental result shows that the energy transferred from excited electron s to lattice atoms through the electron-lattice interaction contribute s to the annihilation of single interstitials. This effect is also obs erved in Ni as a large cross section for radiation annealing, and a de crease of the damage efficiency. On the other hand, in Cu and Ag thin foils, we find that lattice defects are produced not only through elas tic interactions, but also through a process strongly associated with electron excitation. In the latter process, the defect production cros s section is proportional to S(e)1.7 in Cu and S(e)1.5 in Ag. The near ly quadratic dependence of the cross section on S(e) suggests that the mutual Coulomb repulsion of ions positively charged by electron excit ation causes the defect production.