Spectroscopic performance and long-term stability of thallium bromide radiation detectors

Thallium bromide (TlBr) is a very promising detector material used for X- and gamma-ray spectroscopy due to its high atomic number (Tl: 81 and Br: 35), high density (7.56 g/cm3) and wide band gap (2.68 eV). This paper reports results of research on spectroscopic performance and long-term stability of TlBr radiation detectors. TlBr detectors with simple planar structure have been fabricated from crystals grown by the traveling molten zone method. The TlBr detectors have thickness of around 0.4 mm. Gold electrodes (7 mm2) were formed on the opposite two surfaces of the crystals by vacuum evaporation. Spectroscopic performance of the TlBr detectors was evaluated by measuring gamma-ray spectra (60Co). The TlBr detector operated at −20 °C exhibited an FWHM energy resolution of 57 keV (4.3%) for 1.33 MeV gamma-rays. The influence of long-term operation on spectral response of the TlBr detectors has been observed by acquiring energy spectra (137Cs) for a period of time at room temperature and at −20 °C. Although the TlBr detectors exhibited the polarization phenomena at room temperature, they exhibited no significant degradation in spectral response for 100 h at −20 °C.