Precision measurement of the 238 Pu ( n , γ ) cross section

The neutron-capture cross section for Pu-238 was measured by using the detector for advanced neutron-capture experiments (DANCE) array, which is a highly segmented and highly efficient 4 pi gamma-ray calorimeter. The neutron-capture events were recognized by the total 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 similar to 3 in the neighborhood of 0.3 eV from those evaluated in ENDF/B-VII.0.