Prompt-gamma activation analysis and neutron imaging of layered metal structures

Abstract

We present here Monte Carlo computer simulations to broaden the scope of the prompt-gamma activation analysis (PGAA) from the elemental composition measurement of ideal, point-like, homogeneous samples towards non-homogeneous or heterogeneous but still regularly-shaped samples. The successful correction for the negative matrix effect related to the neutron self-shielding and gamma self-absorption is a key step in the quantitative analysis of layered metal structures. This geometry is relevant to practical cases where corrosion layer, patina, paint, coating, gilding, or segregation are present on the surface of a core metal. Linear neutron attenuation coefficients are measured in a polychromatic neutron beam by radiography, while the gamma attenuation calculations by MCNP6 simulations were validated by gamma transmission measurements. Finally, the method was successfully applied to correct for the PGAA matrix effect in double- and triple-layer metal stacks and a real structured numismatic sample.