Coincidence and Interference Corrections for Dual-Energy Gamma Ray Measurements of Soil Density and Water Content
1973
Mansell, R. S. | Hammond, L. C. | McCurdy, R. M.
Coincidence and interference errors in the dual-energy gamma ray attenuation method are discussed for simultaneous determination of water content and bulk density of soil columns. Collimated radiation from 300 mCi each of ²⁴¹Am and ¹³⁷Cs provides a high intensity beam comprised of 60 and 662 keV photons. Count rates measured by a single detector and a two-channel gamma spectrometer were corrected for coincidence losses due to pulse-resolving time. The lower energy channel counts were also corrected for Compton scattering of Cs radiation and for a counting loss attributable to a special coincidence interference. Mass attenuation coefficients were determined for glass beads, water, and eight soil materials. Errors in soil water content measurement by the dual-energy gamma attenuation method appears to be restricted to standard deviations of approximately 1% due to practical limitations in measurement precision of 60 and 662 keV attenuation coefficients for soil and water.
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