Airborne gamma-ray spectrometry surveys consist of mapping the occurrence of naturally occurring Potassium⁴⁰ (K) concentration and equivalent Uranium²³⁸ (U) and Thorium²³² (Th) concentration on the survey’s surface. This is a particularly useful tool for geological mapping of rock alteration and concentration of radioactive element.

The 512-channel gamma-ray spectrometer detects gamma-rays originating from the disintegration of radioactive element’s nuclide. Out of the three main geological radioactive elements, only Potassium40 emits gamma-rays directly. Uranium²³⁸ and Thorium²³² emit gamma-rays through their decay series. It is the 1.76MeV gamma-ray emitted by Bi²¹⁴, which is considered a diagnostic of U²³⁸ and the 2.61MeV gamma-rays emitted by Tl²⁰⁸ that is considered a diagnostic for Th²³². The reason for this is that neither U²³⁸ nor Th²³² emit gamma-ray and those given off by the other daughters between U²³⁸ and Bi²¹⁴ or Th²³² and Tl²⁰⁸ in their decay series are of lower energy and are difficult to resolve.

This is the reason why the concentrations of Uranium and Thorium are considered equivalent assuming that U²³⁸ and Th²³² and their daughters are in equilibrium, which happens after 2 million years for U²³⁸, and after 100 years for Th²³² if none of the decay series’ elements are removed during that time.

GPR propose the AGRS gamma-ray spectrometer. The AGRS series of gamma-ray spectrometers are widely used in geological and geophysical exploration and mapping as well as environmental and nuclear surveillance.

Advantages of the AGRS system for Gamma-Spectrometry

The AGRS system is a self-calibrating Gamma Ray spectrometer using NaI (Tl) large volume detector arrays. Individual, independent, detector processing provides real time gain and linearity correction. All dedicated electronics modules are housed within the detector’s container.  With its high degree of accuracy and its reliability. The system’s stabilization algorithm makes these spectrometer systems fully automated and self-stabilizing on natural radioactive elements. This eliminates the requirement for regular, time consuming, and frequent system checking and re-calibration. Furthermore, it provides excellent accuracy and reliability of the gamma-ray measurements. New design techniques for the electronics peak detection almost completely eliminate 'pulse pile up' and 'Dead Time' effects.

Ongoing research to improve the system stabilization algorithms make these spectrometer systems fully automated and self-stabilizing on natural radioactive elements. This eliminates the requirement for regular, time consuming, and frequent system checking and re-calibration by the user. Furthermore it provides excellent accuracy and reliability of the gamma measurements.

For more information, please contact our Airborne Survey Team