Performance evaluation of tungsten coded-aperture masks with different tungsten material densities for a miniature gamma camera

This study presents a material-density engineering approach to further miniaturize gamma-ray imaging systems for unmanned platforms with strict payload limitations. Three coded-aperture masks were fabricated with identical geometry but different densities: pure tungsten (19.3 g/cm3) and tungsten filament composites (7.8 g/cm3 and 4.0 g/cm3). These masks were integrated into a miniature gamma camera and systematically evaluated in terms of spectroscopic and imaging performance, with results benchmarked against the commercial Energetic Particle Sensor for the Identification and Localization of Originating Nuclei-Gamma (EPSILON-G) system. Spectroscopic tests with a 137Cs source demonstrated an energy resolution of 6.35 %, representing an improvement of about 2 % compared with EPSILON-G, along with favorable peak-to-Compton ratio (PCR) and peak-to-Valley ratio (PVR) values. Imaging results showed that lower mask density generally reduced field of view, angular resolution, and sensitivity. However, the 7.8 g/cm3 tungsten filament mask achieved the optimal balance, yielding 5.6° angular resolution and sensitivity 2–3 times higher than EPSILON-G. Notably, EPSILON-G required up to 150 s for image reconstruction under the same dose-rate conditions, whereas the miniature system localized sources more rapidly due to additional shielding suppressing background radiation. The 7.8 g/cm3 mask reduced weight by 57 % relative to pure tungsten, and the complete miniature gamma camera weighed only ∼700 g, underscoring its suitability for unmanned deployment.