Photoneutron Cross Sections for Natural Cu,Cu63, andCu65

Using monochromatic gamma rays obtained from the annihilation-in-flight of fast positrons, the ($\gamma ,n$) and ($\gamma ,2n$) cross sections for samples of natural Cu, ${\mathrm{Cu}}^{63}$ enriched to 99.3% and ${\mathrm{Cu}}^{65}$ enriched to 99.7% were measured. The ($\gamma ,n$) cross sections for natural Cu, ${\mathrm{Cu}}^{63}$, and ${\mathrm{Cu}}^{65}$ were found to have maximum values of 71±7, 70±7, and 75±7 mb, respectively, while the maximum ($\gamma ,2n$) cross sections are 15.4±2, 13.5±1, and 28±3 mb, respectively. The corresponding values for the ($\gamma ,n$) integrated cross sections up to 28 MeV are 525±52, 523±52, and 437±43 MeV-mb, and the ($\gamma ,2n$) integrated cross sections are 110±11, 80±8, and 195±19 MeV-mb.