The Influence of Vacancies and Impurities on the Damage Production in Platinum Electron‐Irradiated at 90 °K

In platinum foils of 99.999 and 99.9% purity different vacancy concentrations are frozen in by quenching. The foils are then irradiated with 3 MeV electrons at 90 °K. The difference between the radiation damage build‐up in these foils and the damage built‐up in annealed foils which are irradiated simultaneously is investigated up to electron doses corresponding to induced resistivities of 3 × 10 −7 Ωcm. It is found that 1. pre‐quenching can reduce the initial damage rate by a factor of more than 20; 2. the initial damage rate of the annealed samples is independent of their purity; 3. with further irradiation, the rate of decrease of the damage rate for the annealed samples increases with the purity of the samples; 4. for large damages the dose dependence of the damage lies between Δϱ ∼ φ and Δϱ ∼ φ 1/2; . The results can easily be explained by interstitials which migrate freely at 90 °K and are either annihilated by vacancies or converted into another interstitial configuration at impurities. The direct production of immobile interstitials at 90 °K can be excluded.