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The dimension of 20 × 20 × 15 mm 3 has been selected as standard pixelated CdZnTe detector size for many years. Energy resolution of 0.31% full-width at half-maximum (FWHM) at 662 keV for single-pixel events was achieved in one of the best direct-attachment detectors based on VAD_UM v2.2 application-specific integrated circuit (ASIC). Energy resolution under 0.40% was obtained for most of the direct-attachment detectors. The consistent good performance drives the desire to build larger crystals. The increment of size is beneficial in many aspects, such as higher detection efficiency, better imaging performance, better spectroscopic resolution, and potentially lower cost. This article presents the performance of recently delivered 40 × 40 × 10 and 40 × 40 × 15-mm 3 CdZnTe crystals manufactured by Redlen Technology and Kromek Group. The result will be analyzed and the feasibility of mass producing 40 × 40-mm 2 crystals will be discussed. [ABSTRACT FROM AUTHOR]

In collaboration between the University of Michigan and Los Alamos National Laboratory, a 3D position-sensing CdZnTe (CZT) detector prototype was built and integrated into a high-altitude balloon platform to evaluate its performance in a space-like mixed-radiation environment. The detector prototype, Orion Eagle, was designed to operate in near-vacuum environments without any temperature regulation. Orion Eagle was hand-launched from NASA's Columbia Scientific Balloon Facility (CSBF) at Fort Sumner, NM on September 26, 2021, and successfully operated throughout a 9-hour flight, which reached 38.5 km in altitude. The flight met its objectives, successfully detecting atmospheric gamma rays and galactic cosmic rays, and raising the Technical Readiness Level from 4 to 6 for large-volume 3D CZT detector technology for space applications. Ionization tracks produced by charged particles create spatial signatures in the detector that are distinguishable from discrete gamma-ray interactions. Therefore, the 3D position-sensing capabilities using pixelated electrodes on a CZT detector can help enable discrimination of background charged particles from gamma-ray events without an anticoincidence shield. The potential for background rejection capability, ambient-temperature operation, gamma-ray coded-aperture and Compton imaging, and near High Purity Germanium (HPGe) energy resolution motivate the use of large-volume 3D CZT imaging spectrometers in future space missions. [ABSTRACT FROM AUTHOR]

Intrinsic photopeak efficiency of pixelated CdZnTe detectors is an important property for quantitative measurements and analysis, especially for detection and characterization of special nuclear material (SNM). The intrinsic photopeak efficiency of a single 20 mm × 20 mm × 15 mm CdZnTe detector from 59 keV to 2614 keV are measured in experiment. However, compared to the simulated ideal intrinsic photopeak efficiency, the measured efficiency showed deficit. A detailed simulation model including gamma-ray interaction physics, readout electronic as well as signal reconstruction process is built to explain this observed efficiency deficit. The simulated efficiencies of the new model match with experimental results well after taking these factors into account. Efficiency loss due to the guard ring and anode side inaccurate reconstruction are the most important factors. Other miscellaneous efficiency loss mechanisms are discussed too. [ABSTRACT FROM AUTHOR]

Maintaining good energy resolution in 3-D position-sensitive cadmium zinc telluride (CdZnTe) detectors without temperature regulation is desired in field operations to lower power consumption. This requires several calibration measurements at various ambient temperatures. However, required calibration times and storage space for calibration data increase linearly with working temperature range. In this experiment, gamma-ray interactions were measured by 3-D, position-sensitive CdZnTe detectors read out via VAD_UM v2.2 ASICs at various ambient temperatures. Physical causes of changes in detector behavior were studied. A proposed method to reconstruct events using only one complete calibration measurement, and several faster measurements at different ambient temperatures is discussed. Calibration data estimated using the proposed method showed almost identical performance compared to measured calibration data for measurements for various ambient temperatures at equilibrium. The paper also discusses experimental results that showed good resolution in 3-D CdZnTe detector systems can be achieved even if temperature regulation is fully discarded. [ABSTRACT FROM AUTHOR]

Abstract: The charge sharing effect in pixelated CdZnTe (CZT) detectors with a common anode steering grid has been studied. The impact on energy resolution of weighting potential cross-talk and ballistic deficit due to cathode signal shaping has been investigated. A detailed system modeling package considering charge induction, electronic noise, pulse shaping, and ASIC triggering procedures has been developed to study the characteristics of common-grid CZT detectors coupled to the VAS_UM/TAT4 ASIC. Besides an actual common-grid CZT detector coupled to VAS_UM/TAT4 ASIC, a prototype digital read-out system has been developed to better understand the nature of the charge sharing effect. [Copyright &y& Elsevier]