Spectral analysis of the photoconductivity for characterization of CdTe И CdZnTe detectors

The results of the application of optical methods are considered: spectral analysis of photoconductivity in the range 400–1800 nm and field measurements of stationar photoconductivity to study the bulk and surface characteristics of CdTe and CdZnTe gamma-ray detectors. The studies of the photoresponse of the samples were carried out in different irradiation modes: modulated at a frequency of 25 Hz and a constant light flux. The measurements were carried out at room temperature on domestic and foreign materials of detector quality. Using the spectral photoconductivity method, the parameters of deep levels, which affect the detector properties, have been estimated in the studied materials. Based on the calculations of the field dependences of the photoconductivity, the volume and surface parameters of the capture and recombination of non-equilibrium carriers in the investigated detectors were determined. The results of calculating the transport characteristics of charge transfer by electrons μτe in detectors are compared with similar parameters measured using the traditional method of irradiating the detector with alpha particles. To measure the band gap in CdTe and CdZnTe at room temperature the method was modified for calculating ΔEg. The possibility of monitoring the Zn content in CdZnTe detectors using the spectral photoconductivity method is shown.

Design and implementation of the distributed dosimetric system based on the principles of IoT

This paper describes the architecture and components of the distributed information and management system for collecting, processing, storing, and distributing data on a radiometric and dosimetric experiment using the principle of the Internet of Things. Data exchange between elements in the system, as well as the analysis of the received information, involves active application of the ThingSpeak cloud service. Two-way communication with the cloud with a 15-second loop has been implemented. Data are processed in the MATLAB (America) environment, integrated into the cloud. The developed hardware and software solutions demonstrate an increased accuracy of measurements due to the use of promising cadmium telluride (CdZnTe) detectors, modern microcontroller and micro communication technology, and a new algorithm for correcting the dependence of detector sensitivity on radiation energy. Measurement with correction by the method of average charge pulse amplitude is carried out in the energy range from 60 keV to 3 MeV. The resolution of the spectrometric channel is 6.5 % at the peak of 662 keV of full absorption from the reference source, Cesium (Сs – 137). The module for a laboratory sensor network, designed to measure the dose of ionizing radiation, has a built-in spectrometric analog-digital converter, microcontroller control, and a communication unit. Constructing the diagrams demonstrates the operation of the interrupt handler in the form of a series of events occurring when requests arrive from a Web server. The peculiarity of the system is the absence of intermediate devices that make it possible to establish a connection with the Internet. The developed system, equipment, algorithms, and programs are used for experimental studies of radiation and nuclear-physical processes. Elements of the system were useful for remote laboratory work by students

Characteristics of X-ray and gamma radiation detectors based on polycrystalline CdTe and CdZnTe films

Based on CdTe and CdZnTe detectors a number of promising devices were created, which found their application in metallurgy, in solving the problems of customs control and control of nuclear materials, as well as matrix detectors created for the manufacture of medical devices and devices for space research. Detectors, created on the basis of polycrystalline semiconductor CdTe and CdZnTe films with a columnar structure on a molybdenum substrate with a thickness d = 30150 μm, had a specific resistance p > 10^5 10^8 W-cm. The energy resolution of the CdTe and CdZnTe detectors at room temperature reached ~ 5 keV on the 59.6 keV 241Am line.

Charge Sharing and Charge Loss in High-Flux Capable Pixelated CdZnTe Detectors

Cadmium zinc telluride (CdZnTe) detectors are known to suffer from polarization effects under high photon flux due to poor hole transport in the crystal material. This has led to the development of a high-flux capable CdZnTe material (HF-CdZnTe). Detectors with the HF-CdZnTe material have shown promising results at mitigating the onset of the polarization phenomenon, likely linked to improved crystal quality and hole carrier transport. Better hole transport will have an impact on charge collection, particularly in pixelated detector designs and thick sensors (>1 mm). In this paper, the presence of charge sharing and the magnitude of charge loss were calculated for a 2 mm thick pixelated HF-CdZnTe detector with 250 μm pixel pitch and 25 μm pixel gaps, bonded to the STFC HEXITEC ASIC. Results are compared with a CdTe detector as a reference point and supported with simulations from a Monte-Carlo detector model. Charge sharing events showed minimal charge loss in the HF-CdZnTe, resulting in a spectral resolution of 1.63 ± 0.08 keV Full Width at Half Maximum (FWHM) for bipixel charge sharing events at 59.5 keV. Depth of interaction effects were shown to influence charge loss in shared events. The performance is discussed in relation to the improved hole transport of HF-CdZnTe and comparison with simulated results provided evidence of a uniform electric field.