Airborne Gamma-Ray Spectrometry

CIM Bulletin, 1970

A. G. DARNLEY, Head, Remote Sensing Methods, Exploration Geophysics Division, Geological Survey of Canada, Ottawa, Ontario

The Geological Survey of Canada is devoting considerable effort to finding ways to make airborne radiometric measurements both quantitative and reproducible. Equipment has been designed by Atomic Energy of Canada Ltd. to provide high count rates in order to minimize statistical uncertainty, this being essential to justify applying terrain clearance and Compton scattering corrections to the data. Correction factors have been determined experimentally and can be applied automatically. Considerable ground work has been undertaken in parallel with equipment development in order to determine field parameters. Two airborne gamma-ray spectrometers are described. One is based on three 5- by 5-inch Nal(Tl) detector crystals and is used in a helicopter; the other em ploys twelve 9- by 9-inch detectors and is used from a Skyvan aircraft. The former is being used to investigate the range of radiometric response from specific rock types, and for the correlation of ground and air measurements; the latter has completed initial trials and will be commencing experimental surveys during 1969. Results are given to show the comparative sensitivities of the various detector sizes, and operational requirements for a gamma-ray spectrometer survey are discussed briefly.
Keywords: Airborne Gamma-ray Spectrometer Experiments, Compton scattering, Geological Survey of Canada, thorium, uranium, Data, Equipment, Geological Survey of Canada, Radiation, Spectrometers, Survey, Surveys, Systems, Thorium, uranium