Neutron Absorption Cross Section of Americium-241

The ²⁴¹Am neutron absorption cross section, which is predominantly capture, has been measured from 0.01-eV to 370-keV neutron energy. The Oak Ridge Electron Linear Accelerator was used as the source of pulsed neutrons. Resonance parameters have been derived for the data up to 50 eV. The capture gamma-ray detector used was the “total energy detector,” which is a modification of the Moxon-Rae detector. This detector required that the events be weighted by their pulse height in the detector and that the net efficiency of the detector be low. The cross section was normalized at thermal-neutron energies (0.02 to 0.03 eV), and the shape of the neutron flux was measured relative to the ¹⁰B(n, α) cross section up to 2 keV and relative to the ⁶Li(n, α) cross section at higher neutron energies. The results of the measurement indicate a lower cross section (∼25%) between 0.3 and 100 eV than has been previously indicated and an appreciably higher cross section (by 100% at 100 keV) from 20 to 370 keV.