A Precision Measurement of the Total Cross Section of Pu²³⁹ between 0.00291 and 0.1 ev

The total neutron cross section of Pu²³⁹ has been measured at seventeen neutron energies between 0.00291 ev and 0.10 ev with a crystal spectrometer. The absorption cross section was obtained by subtracting the relatively small scattering cross section from the measured total cross section. The sample used was a plutonium-aluminum metallic foil containing 1% aluminum. The isotopic content of the plutonium was 99.82% Pu²³⁹, 0.15% Pu²⁴⁰, and 0.03% Pu²⁴¹. The value obtained for the absorption cross section of Pu²³⁹ at 2200 meters/sec was σ_a = 1007 ± 8 barns.