Photoproduction of the ${^{55-57}}$Co nuclei on ${^{\rm nat}}$Ni at the bremsstrahlung end-point energy of 35-94 MeV

TL;DR

This study measured the production cross-sections of ${^{55-57}}$Co nuclei via photonuclear reactions on natural nickel using bremsstrahlung gamma rays, comparing experimental data with theoretical predictions and highlighting discrepancies for ${^{55}}$Co.

Contribution

First experimental measurement of flux-averaged cross-sections for ${^{55-57}}$Co production on natural nickel at energies 35-94 MeV, with comparison to TALYS-based theoretical models.

Findings

Experimental cross-sections agree with literature for ${^{56,57}}$Co.

Theoretical models match experimental data for ${^{56,57}}$Co but not for ${^{55}}$Co.

Discrepancies suggest need for improved nuclear reaction modeling.

Abstract

Production of the ${^{55-57}}$Co nuclei on ${^{\rm nat}}$Ni in photonuclear reactions using bremsstrahlung gamma photon irradiation with end-point energy $E_{\rm{\gamma max}}$ between 35 and 94~MeV has been studied. The experiment was performed at the electron linear accelerator LUE-40 NSC KIPT using the methods of $\gamma$ activation and off-line $\gamma$-ray spectroscopy. The obtained experimental flux-averaged cross-sections $\langle{\sigma(E_{\rm{\gamma max}})}\rangle$ agree with the data found in literature. The theoretical flux-averaged cross-sections $\langle{\sigma(E_{\rm{\gamma max}})}\rangle_{\rm{th}}$ for the production of ${^{55-57}}$Co and ${^{55-57}}$Ni were estimated using the cross-section values $\sigma(E)$ from the TALYS1.95 code and bremsstrahlung spectra of gamma photons calculated by GEANT4.9.2. The experimental results for ${^{56,57}}$Co agree with the cumulative $\langle{\sigma(E_{\rm{\gamma max}})}\rangle_{\rm{th}}$. However theoretical prediction fails to reproduce the measured cross-sections for the production of ${^{55}}$Co.