Development and performance evaluation of large-area hybrid gamma imager (LAHGI)

We report the development of a gamma-ray imaging device, named Large-Area Hybrid Gamma Imager (LAHGI), featuring high imaging sensitivity and good imaging resolution over a broad energy range. A hybrid collimation method, which combines mechanical and electronic collimation, is employed for a stable imaging performance based on large-area scintillation detectors for high imaging sensitivity. The system comprises two monolithic position-sensitive NaI(Tl) scintillation detectors with a crystal area of 27 x 27 cm(2) and a tungsten coded aperture mask with a modified uniformly redundant array (MURA) pattern. The performance of the system was evaluated under several source conditions. The system showed good imaging resolution (i.e., 6.0-8.9 degrees FWHM) for the entire energy range of 59.5-1330 keV considered in the present study. It also showed very high imaging sensitivity, successfully imaging a 253 mu Ci Cs-137 source located 15 m away in 1 min; this performance is notable considering that the dose rate at the front surface of the system, due to the existence of the Cs-137 source, was only 0.003 mu Sv/h, which corresponds to similar to 3% of the background level. (C) 2021 Korean Nuclear Society, Published by Elsevier Korea LLC.