Design of Capacitive Frisch Grid TlBr Detectors for Radionuclide Identification

Room-temperature operable semiconductor gamma-ray detectors offer the potential of superior energy resolution compared to scintillators, which can be valuable in the design of radionuclide identification equipment. To achieve the best energy resolution and simultaneously provide good sensitivity, multiple detection elements must be arrayed to operate in parallel. This paper describes efforts to construct such an array from multiple elements of thallium bromide (TlBr), a material that inherently offers a high interaction probability and photopeak efficiency for gamma rays. The base design of the array comprises capacitive Frisch grid (CFG) elements. A key objective is optimizing the energy resolution of each element, for which the single-carrier characteristics of the CFG design were chosen. Gains are realized through signal processing that accounts for 1-D or 3-D material inhomogeneity and charge collection variations. Fully corrected energy resolution reaches values of 1.6% FWHM at 662 keV.