ENDF/B-VII.1 Nuclear Data for Science and Technology: Cross Sections, Covariances, Fission Product Yields and Decay Data

Single-crystal perovskite devices 2–3 mm thick exhibit 16.4% X-ray detection efficiency with sensitivity four times higher than α-Se X-ray detectors.

Sensitive X-ray detectors made of methylammonium lead tribromide perovskite single crystals

Over the last decade, cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) wide band gap semiconductors have attracted increasing interest as X-ray and gamma ray detectors. Among the traditional high performance spectrometers based on silicon (Si) and germanium (Ge), CdTe and CdZnTe detectors show high detection efficiency and good room temperature performance and are well suited for the development of compact and reliable detection systems. In this paper, we review the current status of research in the development of CdTe and CdZnTe detectors by a comprehensive survey on the material properties, the device characteristics, the different techniques for improving the overall detector performance and some major applications. Astrophysical and medical applications are discussed, pointing out the ongoing Italian research activities on the development of these detectors.

https://www.mdpi.com/1424-8220/9/5/3491/pdf?view=inline

Progress in the Development of CdTe and CdZnTe Semiconductor Radiation Detectors for Astrophysical and Medical Applications

Cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) have been regarded as promising semiconductor materials for hard X-ray and /spl gamma/-ray detection. The high atomic number of the materials (Z/sub Cd/=48, Z/sub Te/=52) gives a high quantum efficiency in comparison with Si. The large bandgap energy (Eg/spl sim/1.5 eV) allows us to operate the detector at room temperature. However, a considerable amount of charge loss in these detectors produces a reduced energy resolution. This problem arises due to the low mobility and short lifetime of holes. Recently, significant improvements have been achieved to improve the spectral properties based on the advances in the production of crystals and in the design of electrodes. In this paper we summarize 1) advantages and disadvantages of CdTe and CdZnTe semiconductor detectors and 2) the technique for improving energy resolution and photopeak efficiencies. Applications of these imaging detectors in future hard X-ray and /spl gamma/-ray astronomy missions are briefly discussed.

Recent progress in CdTe and CdZnTe detectors

The Shockley–Ramo theorem is reviewed based on the conservation of energy. This review shows how the energy is transferred from the bias supplies to the moving charge within a device. In addition, the discussion extends the original theorem to include cases in which a constant magnetic field is present, as well as when the device medium is heterogeneous. The rapid development of single polarity charge sensing techniques implemented in recent years on semiconductor γ-ray detectors are summarized, and a fundamental interpretation of these techniques based on the Shockley–Ramo theorem is presented.

/pdf/review-of-the-shockley-ramo-theorem-and-its-application-in-1xqbmy5vmk.pdf

Review of the Shockley–Ramo theorem and its application in semiconductor gamma-ray detectors

This review paper presents the current state of the art imaging systems using room-temperature CdTe and CdZnTe X-ray and gamma-ray detectors. Imaging systems composed of both single elements and monolithic segmented CdTe and CdZnTe arrays are used in medical diagnostics, astronomy, research and industry. This paper is divided into three sections: The first section describes different types and configurations of CdTe or CdZnTe detectors used in imaging systems, with the emphasis on single charge carrier collection detectors and front-end read-out electronics in the form of Application Specific Integrated Circuits associated with these detectors. The second section discusses the advantages, disadvantages and limitations with respect to the efficiency and area of the imaging systems using CdTe and CdZnTe detectors compared to other types of X and gamma ray detectors. The third section describes several examples of imaging systems utilizing CdZnTe detectors: 1) A large area imaging telescope for the detection of gamma ray bursts using a coded aperture collimator. 2) A large area medical nuclear camera for cardiology and scintimammography using a parallel hole collimator. 3) A large field of view gamma camera based on a rotating slat collimator and 4) A prototype of an electronically collimated Compton camera.

CdTe and CdZnTe X-ray and gamma-ray detectors for imaging systems

We describe a method for obtaining optimum spectroscopic performance from CZT γ- and X-ray detectors with segmented readout. This method allows to circumvent the effects of incomplete charge collection and to obtain energy resolution approaching the limitation due to detector and electronic noise. It is insensitive to hole trapping over most of the detector volume, while a modest amount of electron trapping can be tolerated. The method requires segmentation of the positive electrode. Signals from the common electrode, taken in coincidence with those of the segmented positive electrode, provide a measure of the depth of interaction. A distinct correlation profile exists between the signals of the segmented element and the common electrode. These profiles can be linearized to yield very sharp energy lines with high photopeak efficiency. Additional cuts can be made to improve peak-to-valley ratio, with small loss in efficiency. We present measurements taken with CZT detectors with pad segmentation. Illuminating with a 133 Ba source, we obtain for the 356 keV line a FWHM of 1.0–1.5%, with a peak-to-valley ratio of ∼100/1.

Optimum spectroscopic performance from CZT γ- and X-ray detectors with pad and strip segmentation

NUCAM3 is the latest generation of solid-state pixelated gamma cameras developed at Soreq NRC. The NUCAM3 head is based on segmented pad monolithic CdZnTe detectors that currently provide a useful field of view of 18.5 cm/spl times/20.1 cm. The camera is designed for cardiac SPECT, breast scintimammography, thyroid, and other small organ evaluation. The camera contains 528 detectors. Each detector is 5 mm thick and is divided to a matrix of 16 square pixels, with a pitch of 2.1 mm. The use of pixelated CdZnTe detectors and low-noise electronics provides a camera with an average energy resolution of 4.5% full width half maximum (FWHM) at 140.5 keV and 9.5% FWHM at 59.6 keV and an intrinsic spatial resolution of 2.1 mm, regardless of the photon energy. We present the analysis of over 1300 CdZnTe monolithic detectors, the physical and imaging characteristics of the NUCAM3 camera and their comparison to state of the art Anger cameras. We show the advantages of CdZnTe technology, which are due to the camera pixel structure and superior energy resolution. These advantages lead to better detectability of small size cold and hot lesions in a scatter environment.

NUCAM3-a gamma camera based on segmented monolithic CdZnTe detectors

Methods for obtaining excellent spectroscopy with pixelated CdZnTe gamma detectors are explored experimentally and theoretically. For a monolithic CdZnTe detector with pad segmentation, the dependence of the induced charge on the depth of interaction is found to be much weaker than for a planar detector, even for coarse pad segmentation and despite the large hole trapping. Two methods are described for removing the dependence on depth of gamma interaction for pixelated detectors. One method is by introducing a mild amount of electron trapping to compensate for the almost complete hole trapping found in most CdZnTe detectors. Proper tuning of the electron trapping by adjusting the detector applied voltage can remove the dependence on depth of interaction over most of the detector volume. At the optimum voltage, we obtain an energy resolution of 1.7% full width at half maximum (FWHM) for the 356 keV line of 133 Ba. Excellent quantitative agreement with theoretical calculations provides a basis for detector design based on these calculations. A second method for obtaining excellent spectroscopy is achieved by simultaneously measuring the pad signal and the signal from the common electrode. Individual gamma lines are observed as sharp bands in the correlation profile between these two signals. A correction is performed to linearize these bands so that they will project onto the photopeak. Using this procedure, we obtain for the 356 keV gamma line of 133 Ba an energy resolution of 1.0–1.5% FWHM with a peak-to-valley ratio approaching 100/1.

Spectroscopy with pixelated CdZnTe gamma detectors – experiment versus theory

We show a method for obtaining excellent spectroscopic performance for CdZnTe γ- and X-ray detectors with segmented readout. Best spectroscopic performance is obtained by tuning the electron trapping in the detector material to obtain optimum compensation for the incomplete charge collection caused by the large amount of hole trapping. For a CdZnTe detector with pad segmentation, we obtain for 57 Co a photopeak resolution of better than 3.5% FWHM with a peak-to-valley ratio of ∼100/1.

Spectroscopy with CdZnTe γ- and X-ray detectors by modifying the electron trapping to compensate for incomplete charge collection caused by large hole trapping

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