1 cm thick HgI2 gamma-ray spectrometers

Thick mercuric iodide (HgI₂) detectors are investigated as potential room temperature gamma-ray spectrometers. By using pixelated anodes the induced charge on the electrode is dependent mainly on electron movement and is almost independent of the depth of interaction. Moreover, by reading out the planar cathode signal simultaneously, the depth of interaction can be determined and any effects of electron charge loss can be corrected. We present recent results from a new 1 cm thick pixelated HgI₂ gamma-ray spectrometer where the pixels have been moved next to each other. Depth corrected resolutions under 2% from a Cs-137 (662 keV) source have been observed while operating these detectors at a relatively low electric field (2500 V/cm) and modest shaping times (4-16 μs). The large surrounding anode was also connected, allowing for the observation of the pulse waveforms on the large non-collecting anode. This allowed for the observation of electron charge sharing between the anode pixel and surround large anode.