Performance Studies of Position-Sensitive Capacitive Frisch-Grid TlBr Detectors

Results from testing of position-sensitive capacitive Frisch-grid (PSCFG) TIBr gamma-ray detectors are presented. Due to its high atomic number, high density, and low Fano factor, TIBr offers excellent energy resolution and high detection efficiency over a wide energy range, thus providing significant advantages over other detector materials commonly used in hand-held instruments. Using high-fidelity 3-D position sensing enables the response non-uniformity caused by defects in the TIBr crystal to be corrected, thereby offering an approach to overcome one of the technical barriers limiting the use of this promising semiconductor material. By utilizing the 3-D position information, temporal and spatial variations of the charge collection efficiency are presented, which provide microscopic characterization of the PSCFG devices. Using the 3-D response correction technique, the best energy resolution measured is <1.6% (FWHM) at 662 keV; it is expected that this resolution will improve further with the introduction of the ASIC-based front-end electronics discussed in this paper. The results presented demonstrate the great potential of PSCFG TIBr detectors and the need for better understanding and control of ionic migration processes in order to achieve good long-term performance.