Proton-induced fission has an advantage for studying nuclear reactions because it involves simpler reaction mechanisms compared to reactions induced by heavier nuclei. Moreover, as charged particles, proton beams can be precisely accelerated and controlled over a wide energy range, allowing systematic analysis of fission fragment yields and improving the production efficiency of rare isotopes. In this work, we investigate proton-induced fission of ${}^{238}\mathrm{U}$ and ${}^{232}\mathrm{Th}$ at incident energies of 20–80 MeV, which are relevant to experiments at the isotope separation on-line (ISOL) facility of the Rare isotope Accelerator complex for ON-line experiments (RAON) in South Korea. The stochastic dynamics of the excited compound nuclei is modeled using the Langevin approach, incorporating a charge-asymmetry coordinate as an additional degree of freedom. This extension enables simultaneous determination of both mass and charge distributions of fission fragments. To estimate the contribution of each fission chance in multichance fission (MCF), we adopt the Fermi gas model instead of the General Fission (GEF) code, in order to include nuclear structure effects such as nuclear pairing. We find that our results for the fission fragment mass distribution (FFMD) are consistent with the available experimental data. Furthermore, we consider prompt neutron emission from primary fragments to calculate the independent fission cross sections, which show reasonable agreement with experimental observations. We also observe that, in the case of proton-induced fission of ${}^{232}\mathrm{Th}$, the nuclear level density parameter plays an important role.

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• Fission
• H & He induced nuclear reactions
• A ≥ 220
• Langevin algorithm
• Thermal & statistical models