Digital fast pulse shape and height analysis on cadmium – zinc – telluride arrays for high-flux energy-resolved X-ray imaging

Cadmium – zinc – telluride (CZT) arrays with photon-counting and energy-resolving capabilities are widely proposed for next-generation X-ray imaging systems. This work presents the performance of a 2   mm-thick CZT pixel detector, with pixel pitches of 500 and 250   µ m, dc coupled to a fast and low-noise ASIC (PIXIE ASIC), characterized only by the preamplifier stage. A custom 16-channel digital readout electronics was used, able to digitize and process continuously the signals from each output ASIC channel. The digital system performs on-line fast pulse shape and height analysis, with a low dead-time and reasonable energy resolution at both low and high fluxes. The spectroscopic response of the system to photon energies below (109Cd source) and above (241Am source) the K-shell absorption energy of the CZT material was investigated, with particular attention to the mitigation of charge sharing and pile-up. The detector allows high bias voltage operation (>5000   V   cm − 1) and good energy resolution at moderate cooling (3.5% and 5% FWHM at 59.5   keV for the 500 and 250   µ m arrays, respectively) by using fast pulse shaping with a low dead-time (300   ns). Charge-sharing investigations were performed using a fine time coincidence analysis (TCA), with very short coincidence time windows up to 10   ns. For the 500   µ m pitch array (250   µ m pitch array), sharing percentages of 36% (52%) and 60% (82%) at 22.1 and 59.5   keV, respectively, wer...
Source: Journal of Synchrotron Radiation - Category: Physics Authors: Tags: digital pulse shape analysis X-ray and γ -ray detectors CdZnTe detectors high flux charge sharing energy-resolved photon counting detectors research papers Source Type: research
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