Measurement of neutron fluence for energies between 20 MeV and 65 MeV using a proton recoil telescope

A proton recoil telescope (PRT) based on n-p scattering at center-of-mass angles between 1480 and 1800 was employed to determine the neutron fluence in nearly monoenergetic neutron fields. The efficiency of the PRT was calculated with a Monte Carlo program which simulates the production of recoil protons in the radiator of the PRT and the transport of these protons through the PRT. Events from n-p scattering in a polyethylene (PE) radiator were experimentally discriminated from other events by means of a ΔE versus E analysis and by additional measurements replacing the PE radiator by a graphite radiator. Examples of measurements at 31.0 MeV and 62.6 MeV are given. The total relative uncertainties of the measured neutron fluences were estimated to be 3.4% and 10.0%, respectively