Abstract The growth of F -centers in LiF irradiated at room temperature with 40- and 85-MeV protons and with 90 Sr electrons was found to be proportional to the square root of the absorbed energy over the range 0.5 to 2.3 Mrad which corresponds to an F -center density range of 1 × 10 16 to 1.5 × 10 17 per cm 3 . The production efficiency was 5 × 10 3 eV per F -center at an absorbed energy of 2.3 Mrad. The density of F -centers produced in MgF 2 by 40- and 85-MeV protons was measured over an absorbed energy range of 0.2 to 29 Mrad which corresponds to a maximum F -center density of 2 × 10 16 per cm 3 . The production efficiency for MgF 2 was 4 × 10 5 eV per F -center at an absorbed energy of 16 Mrad.