Single detectors and pixel arrays based on TlBr

TlBr crystals, grown by hydrothermal and Bridgman-Stockbarger methods, were investigated as potential single and pixel detectors of X- and gamma radiation. Technology of detectors manufactured from TlBr crystals is reported. The spectra of the radionuclides Fe-55, Am-241, Cd-109, Co-57, and Cs-137, measured by single TlBr detectors are presented. Full-width at half-maximum (FWHM) energy resolutions of 500 eV at 5.9 keV; 518 eV at 9.87 keV; 670 eV at 13.92 keV; 777 eV at 22.1 keV; 2.7 keV at 59.5 keV; 3.7 keV at 88 keV; 4.4 keV at 122 keV, and 29 keV at 662 keV have been achieved. Small format (3 × 3) pixel detectors with pads 0.35 × 0.35 mm and gap 0.1 mm were also fabricated on single TlBr crystals of dimensions 2.7 × 2.7 × 1.0 mm3. The interpixel resistivities measured at a bias of 50 V were 400-600 GOhm. The pixel leakage currents at a bias of 250 V were typically less than 0.5 nA. The best spectra were obtained at a temperature of -30°C, a shaping time constant of 6 μs and high voltage of 400 V. Energy resolutions of 2.2, 3.0, 3.7 and 29 keV were measured at input energies of 59.5, 88, 122, and 662 keV, respectively. Values of μτ have been evaluated for two different ingots produced by the Bridgman-Stockbarger method. They are μeτe = 2.5 × 10-4 cm2V-1 and μhτh ∼ 10-6 cm2V-1 for one ingot at -30°C and μeτe = 7 × 10-5 cm2V-1, and μhτh = 1.5 × 10-5 cm2V-1 for the other ingot at -10°C.