| Summary: | This paper deals with the design of a novel spectrometer of fast neutrons in
nuclear safeguards applications based on the liquid organic scintillator
EJ-309 with materials of different thickness surrounding the detector. The
investigation was performed on the simulated data obtained by the
MCNPX-PoliMi numerical code based on the Monte Carlo method. Among the
various materials (polyethylene, iron, aluminum, and graphite) investigated
as layers around the scintillator, polyethylene and iron have shown the most
promising characteristics for evaluation of fast neutron energy spectra. The
simulated pulse height distributions were summed up for each energy bin in
the neutron energy range between 1 MeV and 15 MeV in order to obtain better
counting statistics. The unfolded results for monoenergetic neutron sources
obtained by a first order of Tikhonov regularization and non-linear neural
network show very good agreement with the reference data while the evaluated
spectra of neutron sources continuous in energy follow the trend of the
reference spectra. The possible advantages of a novel spectrometer include a
less number of input data for processing and a less sensitivity to the noise
compared to the scintillation detector without surrounding materials.
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