Neutron self-shielding in hydrogenous samples

Measurements performed in the past to determine sensitivity enhancements (later identified as neutron density increases) in PGNAA as a function of hydrogen concentration in slab-shaped samples are described. The results are compared to the results of Monte Carlo computations. It is concluded that, like H₂O, D₂O can also cause substantial neutron density increases. In one concentrated salt solution, however, D₂O seems to cause a neutron density decrease that cannot be explained from the macroscopic neutron scattering and absorption cross sections in the model used.