Measurement of 232Th(p, x)225Ac reaction cross-section at CSNS APEP facility up to 80 MeV

he radioisotope actinium-225 (225Ac) has been successfully used for targeted alpha therapy in preclinicaland clinical applications because of its excellent nuclear characteristics. Medium- and high-energy protonspallation reactions on thorium are the most important methods for producing 225Ac. This study examinesthe possibility of producing 225Ac by irradiating thorium oxide with medium-energy protons. Thorium-oxidesheets were irradiated with 40-, 50-, 60-, 70-, and 80-MeV protons on the Associated Proton-beam ExperimentPlatform (APEP) of the China Spallation Neutron Source (CSNS). The cross sections for the formation of 225Acwere measured using the activation method and offline gamma-ray spectrometric technique. The experimentalresults were compared with the existing data from EXFOR as well as the theoretical data from the TALYS-based evaluated nuclear-data library. Based on the experimental cross section and theoretical calculations, theproduction yield of 225Ac in the irradiated thorium targets was examined. The results showed that APEP canproduce sufficient quantities of 225Ac for purification and clinical therapy. This work is the first measurementof proton-induced nuclear-reaction cross sections at the CSNS APEP.