Monitoring airborne gamma ray spectrometer sensitivities using the natural background.

Abstract

In many airborne gamma-ray surveys, uranium and thorium sources are required to verify that the airborne system maintains the same sensitivity for each survey flight. Recently, due to radioactive material regulations, it has become increasingly difficult to transport these radioactive sources around the world. Measurements of the natural radioactivity of the ground, recorded as part of source tests carried out in Tanzania were analysed. These data involved three different aircraft at two bases of operation. The results have shown that in all cases the potassium and thorium background measurements were more consistent than the measurements from the uranium and thorium sources. In addition, the variations in the potassium and thorium measurements could be reduced even further by removing the effect of airborne radon daughter fluctuations using stripping ratios derived from measurements on concrete calibration pads.