Proton-induced fission at 190 MeV ofnatW,197Au,natPb,208Pb,and232Th

Abstract

Proton-induced fission at 190 MeV of ${}^{\mathrm{nat}}\mathrm{W},$ ${}^{197}\mathrm{Au},$ ${}^{\mathrm{nat}}\mathrm{Pb},$ ${}^{208}\mathrm{Pb},$ and ${}^{232}\mathrm{Th}$ is studied by means of an innovative method based on activation analysis. The fission-product mass distribution is reconstructed from the fission-product yields, which are obtained from off-line observed $\ensuremath{\gamma}$-ray spectra. For ${}^{\mathrm{nat}}\mathrm{W}{,}^{197}\mathrm{Au}{,}^{208}\mathrm{Pb},$ and ${}^{\mathrm{nat}}\mathrm{Pb}$ the fission process results in a symmetric mass distribution. In the case of ${}^{232}\mathrm{Th}$ the mass yield curve is decomposed into a mixed symmetric-asymmetric contribution originating from fissioning nuclides in the neighborhood of the target mass and a purely symmetric contribution from very neutron-deficient nuclides. The fission cross sections are extracted by integrating over the reconstructed mass distribution. The width of the mass distribution is determined as a function of target mass. The results for the fission cross sections are compared with other experimental data as well as with theoretical model calculations using the LAHET and the ALICE-91 codes.