Investigation on pixellated CZT detectors coupled with a low power readout ASIC

In this work, we investigated on the spectroscopic performances of two pixellated CZT detectors coupled with a custom low noise and low power readout ASIC. The detectors (10 × 10 × 1 mm³ and 10 × 10 × 2 mm³ single crystals) consist of an array of 256 pixels with a geometric pitch of 0.5 mm. The ASIC, fabricated in 0.8 μm BiCMOS technology, is equipped with eight independent channels (preamplifier and shaper) characterized by a dynamic range from 10 keV to 100 keV, low power consumption (0.5 mW/channel) and low noise (150-500 electrons r.m.s.). The spectroscopic results point out the good energy resolution of both detectors at room temperature (5.8 % FWHM at 59.5 keV for the 1 mm thick detector; 5.5 % FWHM at 59.5 keV for the 2 mm thick detector) and low tailing, confirming the single charge carrier sensing properties of the CZT detectors equipped with a pixellated anode layout. Temperature measurements show optimum performances of the system (detector and electronics) at T = 10 ⁰C and performance degradations at lower temperatures. The detectors and the ASIC, designed by our collaboration, represent two small focal plane detector prototypes for hard X-ray telescopes operating in the 10-100 keV energy range.