An in situ field-ion microscope research of radiation damage in tungsten

Results of experiments in which tungsten was irradiated in situ in the field-ion microscope with inert gas ions are described. Tungsten field-ion specimens were irradiated at 78 K with ions in the 0.5 to 9 keV energy range. Sputtering and displacement of surface atoms which had occurred during irradiation were observed directly in field-ion images. Large scale damage such as vacancy clusters were rarely found. From the ion acceleration voltage and the accommodation coefficient, the displacement energy of tungsten surface atoms in the electric field of about 44 MV/mm is estimated as nearly 22 eV. Damage was observed on the shielded side of the tip apex as well as on the ion incident side, and this fact is discussed in comparison with the channelling of ions in tungsten. (author)