Sample Size for Laboratory Calibration of Subsurface Neutron Moisture Gauges
The estimation of adequate sample size is critical to all laboratory methods of calibration of neutron moisture gauges. Neutron gauge response is a function of the true sample geometry rather than an arbitrarily defined spherical geometry. A two-group solution is obtained for neutron flux in a homogeneous, finite, cylindrical sample. The theoretical flux distributions for this solution and for infinite and spherical samples are compared for three representative media. The results show that significant reductions of sample size are possible for media with low moisture contents if the true cylindrical geometry is considered.