Abstract
Cross sections for the 197Au(γ , n) reaction are broadly used in nuclear physics as a standard for normalizing photonuclear reaction cross-section data at photon beam energies above approximately 8 MeV. In this paper, we report cross-section measurements for the 197Au(γ, n) 196Aug+m1 reaction at beam energies from 13 to 31 MeV. Our measurements provide the first cross-section data for this reaction at beam energies above 20 MeV, enabling the use of this reaction as a cross-section standard up to 30 MeV. Also, this work provides first cross-section measurements for the 197Au(γ , n) 196Aum2 reaction. In addition, we measured cross-section data for the 197Au(γ , 3n) 194Au reaction, which can be used as a cross-section standard above about 25 MeV. These measurements were performed using a new target activation method that is based on the angle-energy correlation of the laser Compton-scattered photon beams at the High Intensity Gamma-ray Source (HIγ S). The technique enables measuring photonuclear reaction cross-sections at several discrete beam energies concurrently via a single irradiation on a stack of different targets. Measurements were carried out by irradiating a stack of concentric-ring targets consisting of Au, TiO2, Zn, Os, and Au (in order of the γ -ray beam direction). Our data for the 197Au(γ , n) 196Aug+m1 reaction in the energy range of 13 to 20 MeV are in good agreement with existing ones measured using monoenergetic γ -ray beams, but differ from data acquired using a bremsstrahlung γ -ray beam. Also, above 18 MeV, our data for the 197Au(γ , n) 196Aug+m1 and 197Au(γ , n) 196Aum2 reactions differ significantly from the most recent TENDL and JENDL evaluations, suggesting a need to update these data libraries. The TENDL evaluation and existing data are consistent with our data for the 197Au(γ , 3n) reaction, but differ significantly from the JENDL evaluation above 26 MeV.