A method of determining the bremsstrahlung flux-weighted average photonuclear cross section

Based on a developed analytical model, a method is proposed for measuring the photonuclear cross section averaged over bremsstrahlung flux without application of additional target-monitor of photon flux. The method involves the use of a thin isotopic target, that completely overlaps the photon beam (a photonuclear converter), as well as an algorithm for processing the data on the yield of a reaction under study in such a target. The novel technique was validated on the reactions 100Mo(γ,n)99Mo and 58Ni(γ,n)57Ni in the range of photon end-point energy of 40.7–93.9 MeV. The photon flux-weighted average cross sections of the reactions measured experimentally are in good agreement with Monte Carlo simulations and TALYS predictions on their excitation functions. •Effect of bremsstrahlung converter thickness on photon flux-weighted average (PFWA) cross section is shown.•Reference spectrum for above-threshold bremsstrahlung photons and its realization are proposed.•Weight function for bremsstrahlung photons integrable with reaction cross section in Lorentz form is derived.•Explicit relationship between Lorentz parameters of giant dipole resonance and PFWA cross section has been established.