A study of fission fragment damage in tungsten with the field-ion microscope

The field-ion microscope has been used for the first time to study the utomic details of fission fragment damage in tungsten. Needle-shaped specimens have been bombarded with collimated uranium fission fragment and the dose adjust so that the interaction of a single fission fragment with each specimen can be studied. Large hemispherical craters ∼ 250 Å radius were formed where a fragment interacted with the specimen surface and by using controlled field exaporation the exact geometry of such craters could be found. Field evaporation also enabled the damage in depth to be investigated; and a number of vacamcy clusters ∼ 35 Å diameter were found.