Efficiency calculation of proton recoil neutron telescope with relativistic correction for neutron energy 4 to 20 MeV.

The efficiencies of a proton recoil neutron telescope for neutron energies ranging from 4 MeV to 20 MeV were calculated for different geometries given by Bame et al., for the case of an isotropic point neutron source colinear with the radiator and charge particle detector that are parallel & coaxial to each other. An analytical expression for the efficiency was obtained as a function of the radiator size, detector aperture, source-radiator & radiator-detector distances and n-p differential scattering cross section. The relativistic transformation of n-p differential scattering cross section from center-of-mass to laboratory system was used in the calculations, taking into account the angular anisotropy of the n-p scattering. The accuracies of the calculations were checked by comparing with published efficiency values by Thomas & Axton and Bame et al. The difference between calculated and published efficiencies were small and, in most cases, it was below 1%. Finally, efficiency of the telescope was calculated using the latest n-p scattering cross section data from the evaluated nuclear data file (ENDF) VII for neutron energies ranging from 4 MeV to 20 MeV.