Evaluation of pixellated HgI/sub 2/ detectors

Pixellated mercuric iodide (HgI₂) detectors with thickness of 5 and 10 mm have been investigated using depth sensing single polarity charge sensing technique at room temperatures. By acquiring energy spectra of ¹³⁷Cs as a function of the interaction depth, an insensitive region exhibiting poor spectroscopic performance was observed in the vicinity of the cathode surface of a 10 mm thick HgI₂ detector operated at 2500 V, while the other regions of the detector present clear photo peaks with good energy resolutions. The thickness of the insensitive region is estimated to be around 2 mm. The electron mobility-lifetime (mutau) product was estimated based on the change of photopeak amplitude at different bias voltages. The value of electron mutau product was estimated to be around 1.9times10^-3 cm²/V which is smaller than the value of 7.4times10^-3 cm²/V reported earlier