239Pu(n,2n)238Pu cross section deduced using a combination of experiment and theory

Abstract

The ${}^{239}\mathrm{Pu}{(n,2n)}^{238}\mathrm{Pu}$ cross section has been deduced using a combination of measured partial $\ensuremath{\gamma}$-ray cross sections and enhanced Hauser-Feshbach reaction modeling from threshold to ${E}_{n}<~20 \mathrm{MeV}.$ Eight ${}^{239}\mathrm{Pu}(n,2n\ensuremath{\gamma}{)}^{238}\mathrm{Pu}$ partial $\ensuremath{\gamma}$-ray cross sections were measured using the GEANIE spectrometer, the time-of-flight technique, and energetic neutrons produced at the LANSCE/WNR facility. The $(n,2n)$ cross section was obtained by multiplying the sum of observed noncoincident partial $\ensuremath{\gamma}$-ray cross sections by the calculated ratio of the $(n,2n)$ cross section divided by the sum of the same partial $\ensuremath{\gamma}$-ray cross sections. A comparison between the data and model calculations indicates potential deficiencies in the modeling of the $\ensuremath{\gamma}$-ray cascade.