Cross section structure of²³²Th in the unresolved resonance region

Abstract

An analysis of the 232Th neutron total and neutron capture cross sections has been performed in the energy region between 4 keV and 140 keV. The experimental data are analysed in terms of average resonance parameters utilizing a new statistical method for modelling of the resonance cross section structure in the region of experimentally unresolved resonances. The method exploits the characteristic function of the R-matrix elements distribution in Wigner's theory of nuclear reactions. To improve the representation of the 232Th cross section, the neutron strength functions for s- and p-waves are fitted to the experimental data in order to reproduce their observable fluctuations in (4–140) keV. Our method offers analytical expressions even for nonlinear functionals (observables) of neutron cross section as a transmission ratio. These functionals are incorporated into the evaluation process as a simple benchmark test for verification of the 232Th resonance parameters.