Replacement of Bonner spheres with polyethylene cylinders for the unfolding of an 241Am–Be neutron energy spectrum

Abstract

In this study, a conventional Bonner sphere spectrometer, together with 6LiI(Eu) inorganic scintillator used as the central detector, was used to obtain the neutron energy spectrum of an 241Am–Be source. To achieve this, we calculated the response matrices corresponding to eight different sizes of polyethylene spheres for the neutron energies ranging from about 10-7 to 15 MeV in 54 energy groups by using the MCNPX2.6 code, and the 241Am–Be neutron spectrum was obtained using a modified version of the neutron spectrum unfolding code, AFITBUNKI. In a feasibility study, similar calculations were performed with different sizes of polyethylene cylinders. A comparison between the unfolded spectra of a typical 241Am–Be neutron source with those of Bonner spheres, cylinders of similar sizes, and standard 241Am–Be neutron energy spectra shows that the spectrometer with polyethylene cylinders can be used as a potential alternative for conventional Bonner spheres.