The Possibility of Reconstructing the Low-Energy Part of the Neutron Spectrum of a Photoneutron Source via Neutron Activation Analysis

Resumo

Ways of reconstructing the form of the energy spectrum of the W–Be photoneutron source at the Russian Academy of Sciences’ Institute for Nuclear Research are considered, along with contributions to the spectrum of thermal and epithermal neutrons. A comparative analysis of neutron capture cross sections for various nuclei is performed, accompanied by convolutions of these cross sections with different energy regions of the model neutron spectrum. A number of elements are selected as samples for irradiation by source neutrons and subsequent neutron activation analysis. Only thermal and epithermal neutrons or combinations of them make an appreciable contribution to the measured activities of these elements. The samples are irradiated and the activation spectra are measured using a low-background gamma spectrometer. The shape of the source neutron spectrum in the low-energy part of the spectrum is reconstructed. The values of the neutron flux density for these regions of the spectrum are estimated.