Photonuclear Cross Sections for the $^{197}$Au($\gamma$,pn)$^{195m}$Pt Reaction Near Threshold

TL;DR

This study measures photonuclear cross sections for gold-197 to produce platinum-195m, providing crucial data for medical isotope production near the reaction threshold using gamma-ray sources.

Contribution

First experimental cross-section data for the $^{197}$Au($,$n)$^{195m}$Pt reaction near threshold, aiding isotope production technology development.

Findings

Reaction becomes measurable near 30 MeV gamma energy.

Measured cross sections provide constraints for theoretical models.

Higher bremsstrahlung energies needed for effective isotope production.

Abstract

Platinum radioisotopes are of growing interest for targeted cancer therapy and diagnostic imaging because their decay delivers highly localized radiation doses in tissue, herewith enabling precise DNA damage through Auger-electron emission. Developing production technologies that provide platinum isotopes with high specific activity is therefore essential, and photonuclear reactions on stable nuclei offer a viable accelerator-based route when supported by reliable cross-section data. We report photonuclear cross-section measurements for the $^{197}$Au($\gamma$,pn)$^{195m}$Pt reaction at incident $\gamma$-ray energies of 27, 29, and 31 MeV using the activation method. The measurements were performed by irradiating a stack of concentric-ring gold targets with a quasi-monoenergetic $\gamma$-ray beam provided by the High Intensity Gamma-ray Source (HI$\gamma$S). The induced $^{195m}$Pt activity was quantified using off-line $\gamma$-ray spectroscopy. These data provide the first experimental constraints on the $^{197}$Au($\gamma$,pn)$^{195m}$Pt cross section in the near-threshold region. The measured excitation function is compared with PHITS and TALYS calculations and indicates that the reaction becomes measurable only near 30 MeV, with substantially higher bremsstrahlung end-point energies required for practically meaningful production.