Spectroscopic performance of pixellated thallium bromide detectors

The purpose of this study is to evaluate spectroscopic performance of pixellated thallium bromide (TlBr) radiation detectors. Pixellated TlBr detectors have been fabricated from TlBr crystals grown by the traveling molten zone (TMZ) method with zone-refined materials. Charge transport properties of the crystals were measured by performing the Hecht analysis. The TlBr crystals have exhibited the mobility-lifetime product of around 10^-3 cm²/V for electrons, which is three times larger than the previously reported value. The pixellated TlBr detectors with ∼2 mm thickness have 4 pixellated electrodes (0.57 mm × 0.57 mm each) on the anode surface. In order to evaluate the spectroscopic performance, the detectors have been tested with ⁵⁷Co, ¹³⁷Cs, and ⁶⁰Co gamma-ray sources at room temperature. The TlBr detector 1.9 mm thick has demonstrated energy resolutions of 6.7 keV (5.5%) and 22.3 keV (3.4%) for 122 and 662 keV gamma-rays, respectively. Full-energy peaks of 1.17 and 1.33 MeV gamma-rays from the ⁶⁰Co source have also been detected with the detector.