Hydrogenous content identification in heterogeneous cargoes via multiple monoenergetic neutron radiography

TL;DR

This paper demonstrates a method using multiple monoenergetic neutron radiography to accurately identify and quantify hydrogenous materials in heterogeneous cargoes, enhancing cargo security screening capabilities.

Contribution

It applies pulse-height analysis of transmitted neutrons to quantify hydrogen content in complex cargo mock-ups, advancing neutron radiography techniques for security.

Findings

Able to detect up to 30 g/cm$^2$ of HDPE mixed with metals

Effective in quantifying hydrogenous content in heterogeneous cargo

Potential to improve cargo imaging and elemental analysis

Abstract

The determination of hydrogenous content in commercial cargoes is an important challenge in cargo security. Prior work has shown the feasibility of hydrogenous cargo classification in radiographic applications. This result was achieved by using the significant material to material differences in the energy dependence of their neutron scattering cross-sections. The work presented here details the application of this technique to multiple-monoenergetic neutron transmission measurements of several heterogeneous cargo mock-ups with the goal of quantifying hydrogenous content. It demonstrates the ability to determine the hydrogenous content of a cargo container by performing analysis of pulse-height data of transmitted neutrons. The set-up used for these feasibility studies was able to detect and quantify areal densities of up to 30 g/cm$^2$ of high density polyethylene (HDPE), even when mixed with metallic materials. Accurate determination of the hydrogenous content of the cargo has two important uses: it can allow for better imaging and discrimination of conventional contraband during cargo screening; it may also allow the unfolding of the individual elemental contributions from an effective atomic number, $Z_{\mathrm{eff}}$, as determined from multiple monoenergetic gamma radiography (MMGR). This combination of capabilities could make multiple monoenergetic neutron radiography applications a significant contribution to cargo security.