Single detectors and pixel arrays based on TlBr

Abstract

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/spl times/3) pixel detectors with pads 0.35/spl times/0.35 mm and gap 0.1 mm were also fabricated on single TlBr crystals of dimensions 2.7/spl times/2.7/spl times/1.0 mm/sup 3/. 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/spl deg/C, a shaping time constant of 6 /spl mu/s 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 /spl mu//spl tau/ have been evaluated for two different ingots produced by the "Bridgman-Stockbarger" method. They are /spl mu//sub e//spl tau//sub e/=2.5/spl times/10/sup -4/ cm/sup 2/ V/sup -1/ and /spl mu//sub h//spl tau//sub h//spl sim/10/sup -6/ cm/sup 2/ V/sup -1/ for one ingot at -30/spl deg/C and /spl mu//sub e//spl tau//sub e/=7/spl times/10/sup -5/ cm/sup 2/ V/sup -1/, and /spl mu//sub h//spl tau//sub h/=1.5/spl times/10/sup -5/ cm/sup 2/ V/sup -1/ for the other ingot at -10/spl deg/C.