A novel Compton camera with an annular absorber for enhancing the imaging efficiency in regions directly ahead: A simulation study

Compton camera is an extremely important technology to observe the prompt emissions from gamma-ray bursts. To improve the imaging efficiency of regions directly ahead of the system, a novel Compton camera with an annular absorber was proposed and evaluated. The sensitivity and angular resolution of such a Compton camera were compared with those of a typical Compton camera with two planar detectors. The scatterers of the two cameras were identical and contained 8 x 8 GAGG crystals, with dimensions 10 x 10 x 5 mm(3). The absorber in the typical Compton camera contained 8 x 8 GAGG crystals, each measures 10 x 10 x 10 mm(3). Sixty-four GAGG crystals, each also measuring 10 x 10 x 10 mm(3), were arranged in an annular shape with an inner radius of similar to 51.5 mm and an outer radius of similar to 73.9 mm. A point gamma-ray source (511 keV) and a distributed source placed 1000 mm away from the center of the scatterer were subsequently imaged by the two cameras. By changing the scatterer-to-absorber distance, the efficiency and angular resolution of the two cameras were calculated and compared with each other. With slightly better angular resolution, the novel Compton camera significantly enhanced the system detection efficiency. This enhancement depended on scatterer-to-absorber distance. When the distance was 130 mm, the enhancement was nearly 50%.