Investigation of the small pixel effect in CdZnTe detectors

Wilson, Matthew D.; Seller, P.; Veale, Matthew C.; Sellin, P.J.

doi:10.1109/nssmic.2007.4437231

Cited by 30 publications

(21 citation statements)

References 13 publications

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“…The small aspect ratios bring further benefits in virtue of the small pixel effect. 12 The limit on the energy resolving capabilities is mainly set by the electronic noise. As a result of the direct photon conversion and despite the unavoidable charge sharing, the spatial resolution remains excellent.…”

Section: A Sensor Materialsmentioning

confidence: 99%

Assessment of the spectral performance of hybrid photon counting x‐ray detectors

Trueb¹,

Zambon²,

Broennimann³

2017

Medical Physics

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Purpose: Hybrid Photon Counting (HPC) detectors profoundly improved x-ray diffraction experiments at third generation synchrotron facilities. Enabling the simultaneous measurement of x-ray intensities in multiple energy bins, they also have many potential applications in the field of medical imaging. A prerequisite for this is a clean spectral response. To quantify how efficiently HPC detectors are able to assign photons to the correct energy bin, a quantity called Spectral Efficiency (SE) is introduced. This figure of merit measures the number of x-rays with correctly assigned energy normalized to the number of incoming photons. Methods: A prototype HPC detector has been used to perform precision measurements of x-ray spectra at the BESSY synchrotron. The detector consists of a novel ASIC with pixels of 75 9 75 lm 2 size and a 750 lm thick CdTe sensor. The experimental data are complemented by the results of a Monte-Carlo (MC) simulation, which not only includes the physical detection process but also pulse pile-up at high photon fluxes. The spectra and the measured photon flux are used to infer the Spectral Efficiency. Results: In the energy range from 10 to 60 keV, both the Quantum Efficiency and the Spectral Efficiency were precisely measured and simulated. Good agreement between simulation and experiment has been achieved. For the small pixels of the prototype detector, a SE between 15% and 77% has been determined. The MC simulation is used to predict the SE for various pixel sizes at different photon fluxes. For a typical flux of 5•10 7 photons/mm 2 /s used in human Computed Tomography (CT), the highest SE is achieved for pixel sizes in the range between 150 9 150 lm 2 and 300 9 300 lm 2 . Conclusions: The Spectral Efficiency turns out to be a useful figure of merit to quantify the spectral performance of HPC detectors. It allows a quantitative comparison of detectors with different sensor and ASIC configurations over a broad range of x-ray energies and fluxes. The maximization of the SE is a prerequisite for a successful usage of HPC detectors in the field of medical imaging.

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Section: A Sensor Materialsmentioning

confidence: 99%

Assessment of the spectral performance of hybrid photon counting x‐ray detectors

Trueb¹,

Zambon²,

Broennimann³

2017

Medical Physics

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“…The TCAD package allows the user to generate 2D, or 3D, CdTe detectors with different electrode geometries and uses a drift diffusion model to simulate the detector response. At each point of the model the Poisson and charge carrier continuity equations are solved and the electrostatic potential and carrier concentrations calculated [15]- [18].…”

Section: Simulation Of Edgeless Detectorsmentioning

confidence: 99%

Characterization of Edgeless CdTe Detectors for use in Hard X-Ray Imaging Applications

Veale

Bell

Jones

et al. 2012

IEEE Trans. Nucl. Sci.

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Segmentation of the anode-side of a CdTe diode produces detectors with excellent spatial and energy resolution while maintaining an active area that extends to the detector edge. The CdTe pixel detectors reported have 250 ìm pitch, a detector thicknesses of 1 mm and are bonded to a spectroscopic readout ASIC. The results from an edgeless CdTe detector with indium-diffused anodes, produced via diamond blade segmentation, are compared to those of a CdTe Schottky pixel detector with aluminium anodes and guard band produced using standard photolithographic techniques. The energy resolution at 59.54 keV was measured to be 1.4% and 1.3% for the standard and edgeless detector respectively. The spectroscopic performance of pixels located at the detector edges are discussed with reference to TCAD simulations and X-ray micro-beam measurements.

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“…Nevertheless, there are tradeoffs such as surface resistance and pixel crosstalk issues that one must take into consideration when optimizing and designing pixel arrays of this order. Issues to be considered here include the charge sharing effect [10,11] between adjacent pixels and the polarization (or screening) effect [12,13], which can both lead to unwanted and faulty performance of the device.…”

Section: Direct Conversion Detectormentioning

confidence: 99%

Direct and indirect detectors for X-ray photon counting systems

Prekas

Sabet

Bhandari

et al. 2011

2011 IEEE Nuclear Science Symposium Conference Record

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Most currently available X-ray or gamma ray imaging detectors are based on energy integration over a certain period of time. We have been developing X-ray and gamma ray detectors based on the photon counting (with energy determination) concept using both direct and indirect radiation conversion, together with associated application-specific integrated circuits (ASICs). As an alternative to our ASIC design approach, we are also exploiting the potential of state-of-the-art silicon photomultipliers (SiPMs) and discrete electronics. In this paper we discuss the advantages and disadvantages of these two approaches and we report our latest results on our ASIC design efforts and our achievements on SiPMlCsI:TI detector configurations. We will also discuss the potential uses and advantages that each offers to applications in medicine, imaging, homeland security and industry.

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Investigation of the small pixel effect in CdZnTe detectors

Cited by 30 publications

References 13 publications

Assessment of the spectral performance of hybrid photon counting x‐ray detectors

Assessment of the spectral performance of hybrid photon counting x‐ray detectors

Characterization of Edgeless CdTe Detectors for use in Hard X-Ray Imaging Applications

Direct and indirect detectors for X-ray photon counting systems

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