Electron diffraction pattern of crystal foils containing a high density of point-defect agglomerates

It has been shown that during irradiation at voltages above the threshold voltage for atomic displacements an extremely high density of small point-defect agglomerates (PDA) is produced in nickel and copper specimens. If the nominal displacements per atom exceed about 5 × 10^-2 the contrasts of the PDA overlap to such an extent that they can no longer be resolved on the micrographs.