The Study of Photoproduction of Cobalt Radioisotopes from Copper Nuclei

Abstract

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.