Development of new CdZnTe detectors for room-temperature high-flux radiation measurements

Recently, CdZnTe (CZT) detectors have been widely proposed and developed for room-temperature X-ray spectroscopy even at high fluxes, and great efforts have been made on both the device and the crystal growth technologies. In this work, the performance of new travelling-heater-method (THM)-grown CZT detectors, recently developed at IMEM-CNR Parma, Italy, is presented. Thick planar detectors (3mm thick) with gold electroless contacts were realised, with a planar cathode covering the detector surface (4.1mm x 4.1mm) and a central anode (2mm x 2mm) surrounded by a guard-ring electrode. The detectors, characterized by low leakage currents at room temperature (4.7nAcm(-2) at 1000Vcm(-1)), allow good room-temperature operation even at high bias voltages (>7000Vcm(-1)). At low rates (200countss(-1)), the detectors exhibit an energy resolution around 4% FWHM at 59.5keV (Am-241 source) up to 2200V, by using commercial front-end electronics (A250F/NF charge-sensitive preamplifier, Amptek, USA; nominal equivalent noise charge of 100electrons RMS). At high rates (1Mcountss(-1)), the detectors, coupled to a custom-designed digital pulse processing electronics developed at DiFC of University of Palermo (Italy), show low spectroscopic degradations: energy resolution values of 8% and 9.7% FWHM at 59.5keV (Am-241 source) were measured, with throughputs of 0.4% and 60% at 1Mcountss(-1), respectively. An energy resolution of 7.7% FWHM at 122.1keV (Co-57 source) with a throughput of 50% was obtained at 550kcounts s(-1) (energy resolution of 3.2% at low rate). These activities are in the framework of an Italian research project on the development of energy-resolved photon-counting systems for high-flux energy-resolved X-ray imaging.