Comprehensive Am 242 m neutron-induced reaction cross sections and resonance parameters

The Am242 metastable isomer's neutron-induced destruction mechanisms were studied at the Los Alamos Neutron Science Center using the Detector for Advanced Neutron-Capture Experiments array with a compact parallel-plate avalanche counter. New Am242m neutron-capture cross sections were determined from 100 meV to 10 keV, and the absolute scale was set with respect to a concurrent measurement of the well-known Am242m neutron-induced-fission cross section. The new fission cross section spans an energy range from 100 meV to 1 MeV and was normalized to the ENDF/B-VII.1 evaluated cross section to set the absolute scale. Our Am242m(n,f) cross section agrees well with the cross section of Browne [Phys. Rev. C 29, 2188 (1984)]PRVCAN0556-281310.1103/PhysRevC.29.2188 over this large energy interval. The new neutron-capture cross section measurement complements and agrees well with our recent results reported below 1 eV in Buckner [Phys. Rev. C 95, 024610 (2017)]2469-998510.1103/PhysRevC.95.024610. This new work comprises the most comprehensive study of Am242m(n,γ) above thermal energy. Neutron-induced resonance energies and parameters were deduced with the sammy R-matrix code for incident neutron energies up to 45 eV, and the new average Γγ is 13% higher than the evaluated average γ width.