Determination of moisture content and density of selected wood samples using gamma rays

Wood is hygroscopic in nature which means it naturally absorbs or releases water to balance its internal moisture content with surrounding environment. The present study reports the determination of mass attenuation coefficients of Dek and Poplar wood samples at varying moisture levels using gamma ray transmission method. Measurements were performed using NaI (Tl) scintillation detector and a radioactive source ¹³⁷Cs having energy 0.662 MeV and strength of 1.0 micro-Curie. The moisture content of wood samples was varied by placing them in an oven for fixed duration of time. A graph was plotted between the measured relative transmitted intensities versus the thickness of wood samples and the mass attenuation coefficient as the slope of the fitted plot was obtained. These mass attenuation coefficients when plotted against the relative moisture content of wood samples showed that attenuation coefficient increased with decreasing moisture content, i.e. mass attenuation coefficient was the lowest for completely wet samples and the highest for the oven dried samples.