Precision measurement of the238Pu(n,γ) cross section

Abstract

The neutron-capture cross section for ${}^{238}\mathrm{Pu}$ was measured by using the detector for advanced neutron-capture experiments (DANCE) array, which is a highly segmented and highly efficient $4\ensuremath{\pi}$ $\ensuremath{\gamma}$-ray calorimeter. The neutron-capture events were recognized by the total $\ensuremath{\gamma}$-ray energy deposited in DANCE, which is equal to the reaction $Q$ value plus the incident neutron energy. The absolute neutron-capture cross section was derived as a function of incident neutron energy from thermal to about 30 keV. The measured cross section for incident neutron energy below 18 eV was performed for the first time by using the direct method and does not support the most recently adopted changes in endf/b-vii.1 where the neutron-capture cross section was lowered by as much as a factor of $\ensuremath{\sim}3$ in the neighborhood of 0.3 eV from those evaluated in endf/b-vii.0.