Optical stability of NaCl crystals irradiated under stress

The plastification effect of the mechanically stress-irradiated crystals has been researched. It is shown that the threshold density of the energy of the optical breakdown for the γ-ray stress-irradiated NaCl crystals depends on the exposure dose as well as on the mechanical stress, to which the crystal is subjected in the process of irradiation. When the stress is in the yield point region and the irradiation dose is about 1.5x106 R, the NaCl crystal optical strength against the CO2-laser beam increases 2.5-fold. Different failure characters of the free- and stress-irradiated crystals are due to the different relaxability of stresses in these crystals