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Charge losses at the inter‐pixel gap are typical drawbacks in cadmium–zinc–telluride (CZT) pixel detectors. In this work, an original technique able to correct charge losses occurring after the application of charge‐sharing addition (CSA) is presented. The method, exploiting the strong relation between the energy after CSA and the beam position at the inter‐pixel gap, allows the recovery of charge losses and improvements in energy resolution. Sub‐millimetre CZT pixel detectors were investigated with both uncollimated radiation sources and collimated synchrotron X‐rays, at energies below and above the K‐shell absorption energy of the CZT material. The detectors are DC coupled to fast and low‐noise charge‐sensitive preamplifiers (PIXIE ASIC) and followed by a 16‐channel digital readout electronics, performing multi‐parameter analysis (event arrival time, pulse shape, pulse height). Induced‐charge pulses with negative polarity were also observed in the waveforms from the charge‐sensitive preamplifiers (CSPs) at energies >60 keV. The shape and the height of these pulses were analysed, and their role in the mitigation of charge losses in CZT pixel detectors. These activities are in the framework of an international collaboration on the development of energy‐resolved photon‐counting systems for spectroscopic X‐ray imaging (5–140 keV). [ABSTRACT FROM AUTHOR]

Cadmium--zinc--telluride (CZT) arrays with photon-counting and energyresolving 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 µm, 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 µm 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 mm pitch array (250 µm pitch array), sharing percentages of 36% (52%) and 60% (82%) at 22.1 and 59.5 keV, respectively, were measured. The potential of the pulse shape analysis technique for chargesharing detection for corner/border pixels and at high rate conditions (250 kcps pixel-1), where the TCA fails, is also shown. Measurements demonstrated that significant amounts of charge are lost for interactions occurring in the volume of the inter-pixel gap. This charge loss must be accounted for in the correction of shared events. These activities are within the framework of an international collaboration on the development of energyresolved photon-counting systems for high-flux energy-resolved X-ray imaging (1-140 keV). [ABSTRACT FROM AUTHOR]