Monte Carlo differential neutron sensitivity calculations for nuclear well-logging

The spatial response of neutron porosity measurements, particularly their depth of investigation and their vertical resolution, is of considerable interest for understanding the physics of neutron logging tools. A generalized numerical technique using Monte Carlo simulation has been developed which makes it possible to compute sensitivity functions for essentially any type of nuclear well-logging measurement, including various neutron tools. Calculations of the sensitivity functions are implemented through modification of the MCNP Monte Carlo transport code. The authors present analyses of the spatial responses of an epithermal logging tool using sensitivity function calculations. The results are found to be in good agreement with the empirical data