Age of Californium-252 Fission Neutrons to Indium Resonance Energy in Water

The age of ²⁵²Cf fission neutrons to indium resonance energy (1.44 eV) was measured in water using a source encapsulated in a 7.6-mm-diam by 7.6-mm-high cylinder. The correction for the displacement of the moderator by the source was experimentally determined to be -0.13 cm² or about -0.5% in approximate agreement with calculation. The distribution of indium resonance energy neutrons close to the source was measured to be Gaussian. The age measured for this experiment was 28.69 ± 0.39 cm². An average energy for the ²⁵²Cf neutron spectrum of 2.21 ± 0.05 MeV is inferred from this age.