Determination of241Pu(n,f) cross sections by the surrogate-ratio method

Abstract

The ${}^{241}$Pu(n,f) cross sections have been determined by the surrogate ratio method in the equivalent neutron energy range 11.0--16.0 MeV by using ${}^{238}$U(${}^{6}$Li,$d$)${}^{242}$Pu and ${}^{232}$Th(${}^{6}$Li,$d$)${}^{236}$U transfer reactions at E${}_{\text{lab}}=39.6$ and 39.0 MeV, respectively. Results have been compared with direct measurement of ${}^{241}$Pu(n,f) cross-section data and predictions of statistical model code empire 3.1 for different sets of values of fission barrier heights from evaluated data libraries. The present ${}^{241}$Pu(n, f) cross-section data are observed to be consistent with the direct measurements, suggesting the applicability of surrogate methods. However, the empire 3.1 predictions are not in complete agreement with the experimental data in the neutron energy range 2.0--20.0 MeV for any set of the fission barrier data libraries. The consistency of experimental results on ${}^{241}$Pu(n,f) cross section data from direct and surrogate measurements suggests the need for fission barrier heights for Pu isotopes that are different from those used in standard libraries. The fission barrier heights for various Pu isotopes have been obtained for best fit to the experimental data in the neutron energy range 2.0--20.0 MeV.