A large-volume plastic detector for use in aerial gamma-ray spectroscopy has been evaluated by the U.S. Geological Survey. The purpose of the evaluation was to compare the plastic polyvinyl toluene (PVT) detector with thallium-activated sodium iodide [NaI(T1)] detectors in ability to define the surface distribution of gamma radiation from the decay of natural thorium, uranium, and potassium. Good performance from PVT detectors will allow aerial gamma-ray detection to be less expensive and much less susceptible to physical or thermal shock compared to the use of NaI(T1) detectors.The experimental results indicate that PVT detectors can be used to measure the surface distribution of potassium (K), equivalent uranium (eU), and equivalent thorium (eTh). However, because of the relatively low-energy resolution of the PVT detector and the subsequent increased interference among the energy windows used to measure K, eU, and eTh, the results of data reduction are statistically less accurate than those obtained using NaI(T1).

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