Abstract: | Recent high-voltage electron microscopy has provided evidence that substantial submicroscopic changes may occur in specimens examined in the HVEM under conditions where no visible radiation damage occurs. These are the introduction of vacancies by plastic deformation, rapid accumulation of invisible vacancy clusters by electron irradiation, and radiation-induced contamination and refining of materials. These processes are analysed in terms of defect interactions and the consequences for in-situ experiments are discussed. |