Transient Behavior in TlBr Gamma-Ray Detectors and Its Analysis Using 3-D Position Sensing

TlBr detectors have been investigated as room-temperature or close to ambient temperature operational semiconductor gamma-ray spectrometers. The three-dimensional position-sensitive single-polarity charge sensing technique, successfully used on CdZnTe gamma-ray imaging spectrometers, has been applied to 5-mm thick TlBr detectors and has resulted in energy resolutions as good as 0.73% FWHM and 0.97% FWHM at 662 keV on the best anode pixel and from all nine pixelated anodes respectively. The application of the three-dimensional position-sensing readout technology has significantly improved the spectroscopic performance of TlBr detectors, and has also enabled the study of transient behavior immediately following the application of cathode bias as a function of three-dimensional location within the TlBr detector material. This work presents the latest spectroscopic performance and characteristic initial transient behavior observed at -20^°C on a number of 5-mm thick TlBr detectors manufactured by Radiation Monitoring Devices. Characterizing the initial transient behavior observed in TlBr detectors results in reconstruction technique improvement and may also lead to device fabrication improvements such that stable operation occurs immediately following bias for practical applications.