Design of backscatter type moisture/density RI gauge by MCNP4A code

This study suggests geometrical arrangement of RI gauge that makes use of backscattered radiation. Calculations of important parameters such as distance between the source and detectors, the number of detectors and the position of the detectors were carried out using a Monte Carlo computer code MCNP4A. Depth of soil that is meaningful in determining wet and dry density was also calculated by MCNP4A. Cf-252 neutron source and He-3 detectors were adopted for wet density measurement and Cs-137 gamma source and G·M detectors were used for dry density measurement