Neutron Capture Cross-Section Ratios of ²⁴⁰Pu, ²⁴²Pu, ²³⁸U, and ¹⁹⁷Au in the Energy Range from 10 to 90 keV

The neutron capture cross sections of ²⁴⁰Pu and ²⁴²Pu were measured in the energy range from 10 to 90 keV. The capture cross sections of both ¹⁹⁷Au and ²³⁸U were chosen as standards. Neutrons were produced via the ⁷Li(p,n) reaction with the Karlsruhe 3-MV pulsed Van de Graaff accelerator. Capture events were detected by a Moxon-Rae detector. The high neutron flux available at flight paths as short as ∼10 cm offers a signal-to-background ratio one order of magnitude better than obtained in previous experiments. The cross-section ratios could therefore be determined with a total statistical and systematic uncertainty of 4 to 10% for ²⁴⁰Pu and 6 to 10% for ²⁴²Pu. The results agree with previous data, while discrepancies to the evaluated files ENDF/B-IV and KEDAK 3 were found (up to 30% for ²⁴⁰Pu and up to 50% for ²⁴²Pu).