Recent progress in thallium bromide detectors for X- and γ-ray spectroscopy

Recent progress in the development of room-temperature TlBr detectors is presented. Higher-performance TlBr detectors have been fabricated from high-purity TlBr crystals grown by the traveling molten zone method. The TlBr crystals have exhibited large mobility–lifetime products of 2.6×10−4 and 3.7×10−5 cm2/V for electrons and holes, respectively. An energy resolution of 29.8 keV (5.8%) FWHM has been recorded for 511 keV γ-rays with a TlBr detector at room temperature. Timing properties of the TlBr detectors have been studied by recording the coincidence timing spectra between a TlBr detector and a BaF2 scintillator coupled to a photomultiplier tube. Timing resolution of 21.3 ns FWHM has been measured for 511 keV positron annihilation γ-rays from a 22Na source. By using a single TlBr detector in current mode, an X-ray CT scanner system of a first-generation type has been developed. The performance of the system has been evaluated by observing tomographic images. Images with good spatial resolution have been obtained by the scanner with the TlBr detector.