A study was made of vacancy creation, in polycrystalline material under electron irradiation, by using positron annihilation lifetime spectroscopy. The entire irradiation experiment was simulated by using Monte Carlo and molecular dynamics techniques. This permitted estimation of the absolute vacancy concentration. A comparison with experimental positron lifetimes resulted in a positron trapping coefficient, for vacancies, of 2.8 x 1015/s. The calculations showed that 81% of the vacancies were located in the Ni sub-lattice. By using these results, the vacancy concentration range was deduced for which positron annihilation lifetime spectroscopy was sensitive.

Vacancy Concentration in Electron-Irradiated Ni3Al. Van Petegem, S., Zhurkin, E.E., Mondelaers, W., Dauwe, C., Segers, D.: Journal of Physics - Condensed Matter, 2004, 16[4], 591-603