Experimental determination of the energy dependence of defect production

A knowledge of primary damage production as a function of recoil energy is essential for predicting defect production in radiation environments of practical interest. The damage function $\text{ν(T)}$, i.e., the number of Frenkel pairs as a function of recoil energy, is determined for Cu from electron and ion damage-rate measurements. $\text{ν(T)}$ shows a plateau at $\text{ν = 0.54}$ which extends up to ~ $\text{7T}{}_{\mathrm{d}}{}^{\min }$. Therefore, simple damage models, such as the modified Kinchin-Pease expression, are strongly deficient, not only at high recoil energies where stimulated recombination in cascades reduces defect production, but also in the single displacement regime. As a consequence, no simple relation between $\text{T}{}_{\mathrm{d}}{}^{\min }$ and $\text{T}{}_{\mathrm{d}}{}^{\mathrm{av}}$ is expected to exist. A procedure is suggested which uses anisotropy measurements in combination with polycrystal electron and ion irradiations to construct absolute damage functions in metals.