Comparative assessment of ²²⁹Th production routes from ²³²Th for nuclear clocks

摘要: Nuclear clocks operate on the basis of transitions in atomic nuclei, which offer superior resistance to external perturbations and make them crucial tools for fundamental physics research and precision metrology applications. The nuclide ²²⁹Th is currently the leading candidate for nuclear clocks due to its unique low-energy nuclear transition, while its scarcity and high cost present significant challenges. Here, we evaluate the production of ²²⁹Th through nuclear reactions induced by irradiating ²³²Th targets with γ-ray, proton and neutron particle sources. The interaction between the particle beams and the target was modeled using Geant4, where the relevant reaction channels were constructed and supplemented, and the reaction cross-sections were calculated using TALYS. Using beam parameters representative of existing facilities, the calculated one-year yields of ²²⁹Th are 43.001 mg for a 100 MeV, 1 mA electron beam generating bremsstrahlung photons, 73.728 mg for a 100 MeV, 520 μA proton beam, and 27.227 ng for the adopted PWR neutron spectrum at a flux of 1.21 × 10^{11 -2} s^-1. Proton irradiation gives the highest yield among the three scenarios, while both proton irradiation and electron-beam-driven photonuclear production achieve milligram-scale yields. The radioactive decay accumulation of the products in the ²²⁹Th production chain was recorded, revealing the main contributors to ²²⁹Th.