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

In this study, a conventional Bonner sphere spectrometer, together with LiI(Eu) inorganic scintillator used as the central detector, was used to obtain the neutron energy spectrum of an Am-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 to 15MeV in 54 energy groups by using the MCNPX2.6 code, and the Am-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 Am-Be neutron source with those of Bonner spheres, cylinders of similar sizes, and standard Am-Be neutron energy spectra shows that the spectrometer with polyethylene cylinders can be used as a potential alternative for conventional Bonner spheres.