Neutron Capture and Total Cross Section of Thorium-232 from 0.006 to 18 eV

The neutron total cross section and the shape of the neutron capture cross section of ²³²Th have been measured in the energy range from 0.006 to 18 eV at the Rensselaer Polytechnic Institute Gaerttner Linac Laboratory. The neutron total cross section was obtained from transmission measurements using metallic ²³²Th samples and a ⁶Li glass neutron detector. The total cross section above 0.1 eV is in good agreement with the ENDF/B-V evaluation. Below 0.1 eV, where Bragg scattering is important, the measured total cross section is significantly lower than the evaluated total cross section. The shape of the neutron capture cross section was obtained from 0.009 to 18 eV using a ThO₂ sample and a 1.25-m-diam liquid scintillator detector. The shape of the measured capture cross section above 0.1 eV is in good agreement with a recent shape measurement at Brookhaven National Laboratory. The neutron capture cross section below 0.1 eV is found to increase less rapidly than 1/v with decreasing neutron energy.