Radiation Damage Dependence of Positron Lifetimes in Sodium Halide Crystals

Position lifetime spectra in NaCl and NaF single crystals were measured and analyzed as a function of the crystal defect concentration introduced by proton and gamma irradiation. In the irradiated sodium chloride samples a long‐lived component was observed with a lifetime ${\mathrm{(\tau }}_B)$ of ${\text{8.2\hspace{0.17em}×\hspace{0.17em}10}}^{\text{−10}}$ sec and an intensity ${\mathrm{(I}}_B)$ of up to 28%. Thermal annealing of the sample caused a drastic reduction of the intensity of this component ${\mathrm{(I}}_B)$ to about 10%. Similar observations were made in the positron lifetime spectra in the NaF system.