Incomplete Charge Collection at Inter-Pixel Gap in Low- and High-Flux Cadmium Zinc Telluride Pixel Detectors

Abstract

The success of cadmium zinc telluride (CZT) detectors in room-temperature spectroscopic X-ray imaging is now widely accepted. The most common CZT detectors are characterized by enhanced-charge transport properties of electrons, with mobility-lifetime products μeτe > 10−2 cm2/V and μhτh > 10−5 cm2/V. These materials, typically termed low-flux LF-CZT, are successfully used for thick electron-sensing detectors and in low-flux conditions. Recently, new CZT materials with hole mobility-lifetime product enhancements (μhτh > 10−4 cm2/V and μeτe > 10−3 cm2/V) have been fabricated for high-flux measurements (high-flux HF-CZT detectors). In this work, we will present the performance and charge-sharing properties of sub-millimeter CZT pixel detectors based on LF-CZT and HF-CZT crystals. Experimental results from the measurement of energy spectra after charge-sharing addition (CSA) and from 2D X-ray mapping highlight the better charge-collection properties of HF-CZT detectors near the inter-pixel gaps. The successful mitigation of the effects of incomplete charge collection after CSA was also performed through original charge-sharing correction techniques. These activities exist in the framework of international collaboration on the development of energy-resolved X-ray scanners for medical applications and non-destructive testing in the food industry.

Advances in High-Energy-Resolution CdZnTe Linear Array Pixel Detectors with Fast and Low Noise Readout Electronics

“…Such tailing effects are more prominent in the lines associated to high energy photons, which are stopped deeper inside the detector volume [ 42 ]. This allows inferring that the presented spectroscopic performance could be further improved by applying appropriate corrections in the spectral reconstruction using time coincidence analysis, or depth of interaction correction techniques as widely discussed in the scientific literature of detection systems with imaging capability [ 43 , 44 ]. Figure 10 also shows the decomposition of the experimental data in terms of series and parallel noise components, represented using black dashed lines.…”

Window-Based Energy Selecting X-ray Imaging and Charge Sharing in Cadmium Zinc Telluride Linear Array Detectors for Contaminant Detection

“…As is well documented in the literature [ 30 , 31 , 32 , 33 , 34 ], the charge sharing events, rejected by CSD, can be recovered in counting and energy through the application of the charge sharing addition (CSA) technique. This technique consists in a simple addition of the energy of the charge sharing events.…”

“…This technique consists in a simple addition of the energy of the charge sharing events. Unfortunately, the summed energy is often characterized by deficits due to incomplete charge collection effects at the inter-pixel gap [ 30 , 31 , 32 , 33 , 34 ]. These energy deficits were also observed in our measurements, as shown in Figure 12 .…”

“…Generally, the deficit was lower than that of detectors with 50 µm inter-pixel gap (5 keV at 59.5 keV), demonstrating the benefits in reducing this gap (25 µm inter-pixel gap in our detector). Concerning the origin of these charge losses, several interpretations have been given; some researchers attributed these effects to the hole trapping [ 33 ], others to the presence of distortions of the electric field lines near the inter-pixel gap [ 30 , 31 , 34 ]. To better clarify this issue, we measured the shared events after CSA in temporal coincidence with the cathode signals.…”

Perovskite CsPbBr3 Single‐Crystal Detector Operating at 1010 Photons s−1 mm−2 for Ultra‐High Flux X‐ray Detection

“…A CdTe detector was shown to suffer from significant radiation-induced polarization at a flux of ~ 9×10 10 keV/s/mm 2 18 . CdZnTe (CZT) detectors have also received lots of attention for high flux X-ray detection 19,20 , but CZT detectors also exhibit various degrees of radiation-induced polarization depending on crystal quality 6,21 (Supplementary Table 1). The most recently developed high-flux CZT detectors can operate at 𝜙𝜙 𝑝𝑝 ~ 10 8 p/s/mm 2 for 120 kVp tungsten X-rays tested at photon counting mode 6,22 .…”