Neutron Capture Cross Sections from 0.1 to 3 MeV by Activation Measurements

Neutron capture cross sections for, ²³⁸U, ²³⁷Np, ²³²Th, ¹⁹⁷Au, ¹⁹³Ir, ¹⁹¹Ir, ¹⁸⁷Re, ¹⁸⁵Re, ¹⁸⁶W, ¹⁸¹Ta, and ¹¹⁴Cd relative to the ²³⁵U fission cross sections have been determined for neutron energies from 120 keV to 2.9 MeV by the measurement of the activation products. Neutrons were produced by the ³H(H,n)³He reaction on tritium gas targets on the Los Alamos Scientific Laboratory vertical Van de Graaff accelerator. Metal foils were exposed at selected angles and distances from the neutron source to achieve a selection of neutron energies. Neutron fluxes were measured with ²³⁵U fission detectors placed at various angles for different proton energies. Scattering corrections were applied to the experimental results through the use of Monte Carlo computer simulation techniques. Corrections were also calculated for the purely geometrical effects on energy resolution due to finite source and sample width and thickness.