Spectroscopic Performance of Thick HgI₂ Detectors

This paper presents the spectroscopic performance of two newly developed pixelated HgI₂ detectors. These detectors are 1 × 1 × 0.814 cm³ and 1 × 1 × 1.016 cm³ in size. Each detector has four closely packed 1 × mm² anode pixels at the center of one of the 1 × 1 cm² surfaces. These anode pixels are surrounded by a large anode. All results presented here are based on events from a sub-volume underneath the anode pixels. In these detectors, signals were read out by a discrete electronics based on multiple A-250 pre-amplifiers and a digital oscilloscope for sampling pulse waveforms. Depth sensing technique was used to correct the depth-dependent variation in photopeak amplitude. Main results presented are: (1) energy resolutions of 0.85 ~ 1.3% have been achieved on these detectors; (2) the electron mobility-lifetime product was measured to be ~1 × 10^-2 cm²/V and the measured electron lifetime was ~200 μs and (3) variation in electron drifting properties under different anode pixels were observed. Significant non-uniformity in internal electric field strength was also experimentally demonstrated.