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 now permits us 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. We present here our 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. It is anticipated that this new ability to compute spatially distributed sensitivity functions for neutron interactions will be an important aid in well-logging tool design.
