Annealing of γ -irradiation induced hardening in NaCl

Abstract Some new data on the thermal and optical annealing of γ-irradiation induced hardening of NaCl are reported. Mechanical tests have been performed at room temperature and at liquid nitrogen temperature. For crystals irradiated into the late stage of the colouring, isothermal annealing data at temperatures ≲ 200°C suggest the dissolution of the interstitial clusters formed during the irradiation. At ∼300°C the recovery of the crystals is complete. On the other hand, the temperature dependence of the hardening for bleached samples indicates that interstitial clusters are essentially stable throughout the bleaching process.