Am-241 Neutron Capture Cross Section in the keV region using Si and Fe-filtered neutron beams

The neutron capture cross-section of Am-241 was measured in the keV neutron range using the recently implemented neutron filtering system of the Accurate Neutron-Nucleus Reaction Measurement Instrument (ANNRI) beamline in the materials and life science (MLF) facility of the Japan Proton Accelerator Research Complex (J-PARC). Filter arrays consisting of 20 cm of Fe-nat and Si-nat were employed in separate measurements to provide filtered neutron beams with averaged neutron energies of 23.5 (Fe), 51.5 and 127.7 (Si) keV. The present Am-241 results were obtained relative to the Au-197 neutron capture yield by applying the total energy detection principle together with the pulse-height weighting technique. The Am-241 neutron capture cross-section was determined as 2.72(29) b at 23.5 keV, 2.14(26) b at 51.5 keV and 1.32(10) b at 127.7 keV with total uncertainties in the range of 8 to 12%, much lower in comparison to the latest time-of-flight experimental data available.