Field-ion microscopy of tungsten bombarded by low-energy argon ions

The investigation of low-energy ion radiation damage in tungsten by field-ion microscopy is discussed. An experimental arrangement is described in which prepared field-ion microscope specimens may be bombarded in situ by ions from an ion gun. The background pressure in the range of 10 −11 Torr allows bombardment to be carried out while the high voltage is off. Results of specimens bombarded with Ar + ions in the 150–450 eV range at 63 °K are described. Diffusion of self-interstitials upon annealing the irradiated specimen from 63 to 78 °K has been observed. Besides point defects, clusters of vacancies and interstitials have been observed on specimens bombarded with 400 and 450 eV Ar + ions. The irradiation-induced defect density on the side of the microscope specimen facing the ion beam is approximately double that on the far side.