Photonuclear cross sections for Au 197 : An update on the gold standard

Le résumé fourni par la source

Cross sections for the $^{197}\mathrm{Au}(\ensuremath{\gamma},n)$ 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 $^{197}\mathrm{Au}{(\ensuremath{\gamma},n)}^{196}{\mathrm{Au}}^{g+m1}$ 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 $^{197}\mathrm{Au}(\ensuremath{\gamma},n)^{196}\mathrm{Au}^{m2}$ reaction. In addition, we measured cross-section data for the $^{197}\mathrm{Au}(\ensuremath{\gamma},3n)^{194}\mathrm{Au}$ 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 ($\mathrm{HI}\ensuremath{\gamma}\mathrm{S}$). 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, ${\mathrm{TiO}}_{2}$, Zn, Os, and Au (in order of the $\ensuremath{\gamma}$-ray beam direction). Our data for the $^{197}\mathrm{Au}(\ensuremath{\gamma},n)^{196}\mathrm{Au}^{g+m1}$ reaction in the energy range of 13 to 20 MeV are in good agreement with existing ones measured using monoenergetic $\ensuremath{\gamma}$-ray beams, but differ from data acquired using a bremsstrahlung $\ensuremath{\gamma}$-ray beam. Also, above 18 MeV, our data for the $^{197}\mathrm{Au}(\ensuremath{\gamma},n)^{196}\mathrm{Au}^{g+m1}$ and $^{197}\mathrm{Au}(\ensuremath{\gamma},n)^{196}\mathrm{Au}^{m2}$ 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 $^{197}\mathrm{Au}(\ensuremath{\gamma},3n)$ reaction, but differ significantly from the JENDL evaluation above 26 MeV.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.