Investigation of pixellated TlBr detectors using digital signal processing techniques

Pixellated TlBr detectors are studied for room temperature gamma-ray spectrometers. 4-mm thick TlBr detectors pixellated Au anodes were made by RMD Inc.. Each detector has a planar cathode and four anode pixels surrounded by a guard ring. The pixel pitch is 1 mm. Digital pulse waveforms of preamplifier outputs were recorded using a multi-channel GaGe PCI board. Digital CR-RC shaping filters were used, with 6μs shaping time for the anode pixel and 10μs shaping time for the cathode. After depth correction using cathode-to-anode signal ratio technique, an energy resolution of 2.4% FWHM at 662 keV was obtained at room temperatures from single pixel, when the cathode was biased to −600V. Current TlBr detectors suffer from polarization, which causes performance degradation over time when high voltage is applied. The polarization effect is observed after four hours of operation. This effect can be partially mitigated by reversing the polarity of high voltage bias applied to the detector.