Spectroscopic performance of pixellated thallium bromide 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 for electrons, which is three times larger than the previously reported value. The pixellated TlBr detectors have thicknesses of ~2 mm and 4 pixellated electrodes (0.57 mmtimes0.57 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 5.5% (6.7 keV) and 3.4% (22.3 keV) 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