Experimental and simulated study of detector collimation for a portable 3″ × 3″ NaI(Tl) detector system for in-situ measurements

Abstract

The effect of detector collimator and scatterer thickness on multiple Compton backscattered gamma photons is studied. Gamma photons from a 137 Cs source of 5.8 mCi, is allowed to fall on Carbon, Aluminium, Iron and Copper targets and the scattered photons are detected by a properly shielded 76 mm  76 mm NaI(Tl) scintillation detector located at 90 to the incident beam. To extract the contribution of multiple scattered photons from the measured spectra, single scattered distribution is remodelled analytically. The thickness at which the multiple scattered photons saturate is determined for different detector collimator apertures and scatterer thicknesses. The variation of saturation thickness, Signal-to-Noise (S/N) ratio, Multiple Scattering Fraction (MSF) for different materials and collimator sizes are studied and compared with the available literature. Monte Carlo simulated calculations using MCNP code supports the present experimental work.

Model of absorbed gamma radiation in the interaction with rock formation

“…where Q-gamma radiation source intensity, 1/sec, h-distance from gamma radiation source to the irradiated surface, m, dxdy-area element in Cartesian coordinate system, m 2 .…”

“…Analysis of the results of studies and publications on the control of iron content in ore arrays using LS in wells showed that in most cases insufficient attention is paid to the issues of measurement accuracy [1]. Nuclear physics methods for determining the content of the useful component in the ore were considered in works [2][3][4], where attempts were made to improve the accuracy of measurements depending on the number of gamma quanta reflected from the surface of the absorber. In work [5], the parameters of scintillation sensors for recording scattered gamma quanta are considered.…”