The Study of Photoproduction of Cobalt Radioisotopes from Copper Nuclei

The process of photoproduction of a series of radioisotopes from copper nuclei at the bremsstrahlung end-point energies $$E_{\gamma }^{{\max }}$$ = 21, 30, and 40 MeV was studied at the AANL (YerPhI) linear electron accelerator. The relative yields of 61Co, 60Co, 58Co, 57Co with respect to the 61Cu are measured; in particular, at $$E_{\gamma }^{{\max }}$$ = 40 MeV they are equal to (2.6 ± 0.3) × 10–2, (2.67 ± 0.04) × 10–2, (9.3 ± 0.6) × 10–2, and (0.76 ± 0.04) × 10–2, respectively. It is shown that the predictions of the TALYS model, as well as the model inserted in the GEANT4 software package are in a contradiction (especially in the case of the GEANT4 code) with the measured relative yields. A continuously decreasing energy dependence was observed for the ratio of unfolded (weighted with the bremsstrahlung spectrum) cross-sections of reactions 65Cu(γ,α)61Co and 63Cu (γ,2n)61Cu, similarly to that observed earlier for the ratio of cross-sections of electronuclear reactions 65Cu(e,e′ + α)61Co and 63Cu (e, e′ + 2n)61Cu. The ratio of the 61Co and 64Cu yields is also measured, being equal to (2. 6± 0.2)×10–3, (3.8 ± 0.6) × 10–3, and (3.2 ± 0.4) × 10–3, respectively, at $$E_{\gamma }^{{\max }}$$ = 21 MeV, 30 MeV, and 40 MeV; its value (2.6 ± 0.2) × 10–3 at $$E_{\gamma }^{{\max }}$$ = 21 MeV is consistent with the general trend of the dependence of this ratio on the atomic number Z, measured recently at $$E_{\gamma }^{{\max }}$$ = 23 MeV for heavier nuclei with the atomic numbers from Z = 47 to Z = 82.