The effect of the diameter of the detector collimator on saturation thickness in gamma scattering measurement

Abstract

The effect of the diameter of the detector collimator on the saturation thickness in gamma-scattering measurements is studied using the spectrum of singly scattering. Geometric arrangement of gamma-scattering measurement includes: a gamma-ray collimated beam with the energy of 662 keV emitted from ¹³⁷Cs source is irradiated on a rectangular aluminium target with incident angle of 90^o, and detector NaI(Tl) 5.1cmx5.1cm with collimator is used to record the scatterd gamma rays at scattered angle of 120°. The experimental measurements are carried out to obtain scattered spectra with various target thickness and diameter of  detector collimator. The profile of the singly scattering and multiply scattering in the scattered spectra are determined by a spectrum processing technique based on the least squares fitting. The experimental results showed that the saturation thickness of the counts of singly scattering increases with increasing the window diameter of the  detector collimator. These results will support for the non-destructive testing research of application of gamma-scattering method to determine the thickness or the defect of the sample.