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Activation experiments with quasi mono-energetic neutrons produced by the 7Li(p, n)7Be reaction with proton-energies between 36.4 and 178.8 MeV were performed at UCL and TSL in order to determine cross sections for the production of residual nuclides from 13 target elements. The targets were irradiated in well-characterized neutron fields monitored by various measuring techniques. Residual nuclide abundances were determined by γ-spectrometry. Cross sections were derived from them by an iterative method based on measured and calculated neutron spectra inside the target stacks and starting from “guess” excitation functions calculated by the ALICE-IPPE code. First results for the target element lead are presented.

New results are presented of the intermediate energy neutron- and proton-induced fission cross sections of nuclei in the lead region. These results, together with earlier ones, are used for comparison of the fission probability of nuclei induced by protons and neutrons. Possible physical reasons of observed differences in proton- and neutron-induced fission cross sections are discussed.