Fission Neutron Multiplicity for the ^242mAm(n,f) Reaction

The fission neutron multiplicity, , of ^242mAm(n,f) was measured relative to that of ²³⁵U(n,f) using the neutron time-of-flight facility at the Lawrence Livermore National Laboratory 100-MeV electron Linac. Incident neutron energies ranged from 0.037 to 30 MeV. Fission fragments were detected using two hemispherical ionization chambers each containing ∼400 µg of 99.2% pure ^242mAm. A separate fission chamber with 8.3 mg of ²³⁵U was situated between the two ²⁴²Am chambers and provided a normalization at every data point. Fission neutrons were detected in a liquid benzene scintillator using pulse-shape discrimination to separate gamma rays from neutrons. A comparison of the measured energy dependence of is made with semi-empirical models of neutron emission from the actinides.