The Potential Of Real-Time, Fast Neutron And Gamma Radiography For The Characterization Of Low-Mass, Solid-Phase Media

Most techniques that are used for transmission imaging with ionizing radiation use X-rays, which have the advantage of providing quick, high-resolution images with a relatively small dose of radiation. However, they also have the disadvantage that their penetrating power can be limited in some forms of matter. This can make the discrimination of materials with a low atomic number particularly challenging. Of specific interest in this regard is the need to screen a diversity of manmade items that are heterogeneous and with the tendency to have many interfaces between components that can comprise a diversity of low-mass elements and compounds. These items usually have a compact geometry and a high density of components, which can make them less easy to be imaged quickly and effectively with X-rays. This limit of current screening technology necessitates further stages of examination reducing the ease with which this is done for manufacturing and quality assurance applications. The results presented in this paper demonstrate that, either via fast-neutron radiography or tomography, the potential exists to discern a variety of low-A compounds from one another. Via Monte Carlo simulations, it will be shown that fast-neutron radiography undertaken with a portable, isotopic radiation source (californium-252), absorption and scattering by the doped polymeric materials yields a degree of distinction from other substances. Considering these results, the state-of-the-art of the technique leading to the realization of a combined, real-time fast-neutron and gamma-ray radiography system will also be presented, as well as the first experimental results.