Energy dependence of proton induced fission cross sections for heavy nuclei in the energy range 200–1000 MeV

Abstract

Total cross sections for proton induced fission of ${}^{\mathrm{nat}}\mathrm{Pb}$, $^{209}\mathrm{Bi}$, $^{232}\mathrm{Th}$, $^{233}\mathrm{U}$, $^{235}\mathrm{U}$, $^{238}\mathrm{U}$, $^{237}\mathrm{Np}$, and $^{239}\mathrm{Pu}$ nuclei were measured in the range 200--1000 MeV with an energy step of 100 MeV. The experiment was carried out at 1 GeV in a PNPI synchrocyclotron. Complementary fragments of the binary fission from a thin target were detected in coincidence by two parallel plate avalanche counters (PPAC) located close to the target. An assembly of the two PPACs and with the target in between them was placed directly into the beam, which provided a large solid angle acceptance. The beam monitoring system employed a scintillation counter telescope that was used for direct proton counting as well as for registration of the elastic $\mathit{pp}$-scattering events from the auxiliary (${\mathrm{CH}}_{2}){}_{n}$ target. The measured energy dependence of the total fission cross sections is presented. The results are compared with other available experimental data as well as with calculations in the frame of the cascade-evaporation model.