Gamma Spectrometry in the Presence of Fast Neutrons

Abstract

Purpose: In some gamma spectroscopy experiments, neutrons may also be present, so depending on experimental conditions, Gamma spectroscopy can be influenced by the presence of neutrons.

Materials and Methods: In this study, a NaI(Tl)(63 mm×63 mm) detector is used to investigate the effects of fast neutrons on the spectrum of gamma photons. The radiation source used in these experiments is made up of two point sources: an AmBe (50 mCi) neutron source and a ¹³⁷Cs(10 mCi) gamma source.

Results: Results were determined through both measurements and Monte Carlo simulation (MCNPX) under two different experimental conditions and were compared. When the detector is placed under an angle to the source, gamma photon energy peaks resulting from inelastic interactions of the fast neutrons with the detector materials and surrounding materials in the energy range of 0.1-0.9(MeV) are pretty visible in the gamma main spectrum. These results can be used to optimize industrial tomography experiments carried out with NaI(Tl) scintillators.

Conclusion: Also, the results show that the detection of fast neutrons with a NaI(Tl) scintillator is possible with low efficiency.