Experimental cross sections and mass distribution of fission products of thorium-232 irradiated with protons in energy range 20–140 MeV

Proton-induced fission of 232Th was studied in a wide proton energy range 20–140 MeV. A large amount of experimental cross sections for individual and cumulative formation of 232Th fission products were determined by means of stacked-foil irradiation followed by high-resolution γ-ray spectrometry. The obtained results were compared with available literature data and theoretical calculations performed with cascade–evaporation–fission model. The fission-product mass distribution in the given proton energy range was described with a three-peak curve representing asymmetric and symmetric fission modes. The fraction of symmetric fission mode increased along with the incident proton energy up to 60–70 MeV reaching a plateau at the value around 0.65.