A MONTE CARLO SIMULATION OF SURFACE-TYPE NEUTRON MOISTURE GAUGE

The surface-type neutron moisture gauge has been simulated with a modified version of the 05R Monte Carlo code available from the Radiation Shielding Information Center at Oak Ridge, Tennessee. Results were obtained for 19 different sample media representative of a range of moisture contents for typical construction soils. These results are in the form of the following information for each neutron emerging from the sample surface: distance from source to point of emergence, neutron energy at emergence, and three direction cosines characteristic of the emergent direction of motion. The counting yield of two BF3-filled proportional counter detectors was predicted by the Monte Carlo simulation for 10 samples, and these predictions were compared to experimental results. The correspondence between the Monte Carlo simulation and the experimental results was found to be quite good. Results are given to indicate the effect of iron content and sample density on gauge response. The uses of the Monte Carlo simulation program and results are discussed, including optimum gauge design studies and calibrations of existing neutron gauges. © 1969.