Passive Gamma-Ray Detection With Compact Lightweight Imager for Nuclear Safeguards.

Localizing and quantifying special nuclear materials (SNMs) is desired for effective nuclear security and robust nuclear power management. Here, we demonstrate a compact radiation imaging system based on a coded aperture that allows one to form a quantified radionuclide distribution map for small amounts of SNM. The imager is based on the active scintillating medium: cerium-doped gadolinium aluminum gallium garnet [Gd3Al2Ga3O12(Ce) or GAGG(Ce)], which even in arrayed form exhibits excellent detection efficiency and good energy resolution over a wide energy range. With a $12 \times12$ array of $4\times 4\times20$ mm3 pixels, the instrument can image, at a target-to-imager separation of 1 m, 1 g of highly enriched uranium (HEU) in 4 min, 75 g of depleted uranium (DU) within 11 min, and 100 g of uranyl nitrate hexahydrate (UNH) within 11 min. The instrument, termed EPSILON-G, can also measure the ambient dose equivalent, H*(10), for radionuclides inside the unit’s 45° field of view (FOV), allowing one to accurately reconstruct the radiation dose map inside buildings. The system provides a precise determination of the H*(10) within a short acquisition time when compared to a Geiger–Muller (GM) survey meter due to the sizable area of the GAGG(Ce) scintillator array and its high density and $Z_{\text {eff}}$. Furthermore, one can identify, in real time, by means of gamma-ray detection, the accurate locations of neutron-gamma sources, as demonstrated with mixed emitters 252Cf, 239PuBe, and 241AmLi all while maintaining a gamma-ray analytical capability. [ABSTRACT FROM AUTHOR]