Use of an intrinsic germanium detector array for an aerial survey of surface nuclear radiation

This report describes the results of an experiment to measure the natural gamma radiation emitted from the earth's surface with the aid of radiation detectors mounted in an aircraft. For comparison, two detector systems were used: an array of intrinsic germanium detectors with a total active volume of 0.4 liter and a single NaI(Tl) scintillation detector 30.5 cm diam X 30.5 cm long. Data were recorded on flights at altitudes of 60, 120, 240, 300 and 5,100 meters and with average airspeed of 200 knots. A discussion is presented on the application of germanium detectors to the atmospheric radon problem; in particular, on the use of the photons with energy 295, 352 and 609 keV to determine the respective contributions from the air and the surface.