Study of the spectral response of CZT multiple-electrode detectors

Cadmium zinc telluride (CZT) is a promising material for room temperature X-ray and gamma-ray detectors. The high atomic number and the wide band-gap give high quantum efficiency and good room temperature performances. Due to hole trapping, particular electrode structures have been developed to provide single-charge carrier collection (electrons), exploiting the excellent charge transport properties of the electrons. In this work, the spectroscopic performances of two CZT detectors (CZT1: 5 mm times 5 mm times 0.90 mm; CZT2: 4.8 mm times 5 mm times 0.55 mm) with five electrodes (cathode, anode and three steering electrodes) were studied. The anode-collecting electrode, surrounded by three steering electrodes (biased for optimum charge collection), is mostly sensitive to electron carriers, overcoming the effects of hole trapping in the measured spectra (hole tailing). We investigated on the spectroscopic response (241Am source; 59.5 keV) of the detectors at different bias voltages of the electrodes. The detectors exhibit excellent energy resolution (CZT1: 2.0% FWHM at 59.5 keV; CZT2: 1.7% FWHM at 59.5 keV; working temperature -10degC) and low tailing (CZT1: FW.1M to FWHM ratio of 1.93 at 59.5 keV; CZT2: 2.35 at 59.5 keV). This study stresses on the excellent spectroscopic properties of the CZT detectors equipped with a custom anode layout, making them very attractive candidates as x-ray spectrometers mainly for medical applications

Gamma-spectrometric module based on HPGe detector for radiation portal monitors

The appearance of small-sized and powerful enough electric cryocoolers of various types on the market, has opened the perspective of HPGe detectors application, cooled by such coolers, in radiation portal monitors. The first results of a spectrometric module based on HPGe detector with relative efficiency of 45% cooled by a Stirling-cycle cryocooler, are presented. The spectrometer has provided energy resolutions of less than 0.95 keV and 1.95 keV at energies of 122 keV and 1332 keV, respectively. The deterioration of the energy resolution of HPGe detector cooled by electric cryocooler in comparison to the resolution with liquid nitrogen cooling was about 8% at the energy of 1332 keV. With the use of activated filters to suppress pulses produced by the mechanical vibrations, the energy resolution of the spectrometer was 0.8 keV and 1.8 keV, respectively, however, the detector relative efficiency at the energy of 1332 keV has dropped to 39 %

The development of waste assay monitors based on the HPGe detectors

The results from the development and the evaluation of radioactive waste monitors for small, medium, and large volumes of those wastes are presented. The efficiency calibration of monitors was made using the standard sources in point geometry as well as by using the complex calculation of the efficiency curves using the Monte Carlo simulation method. The volumetric activity sources were manufactured in the form of real 200, 400, and 700 litre barrels with matrix-fillers in order to calibrate the monitors using the direct verification method. The peculiarities of the software that controls the monitors are presented

Industrial X-ray Fluorescence Analyzer for Real-Time Thickness Measurements of Aluminium Coatings on Rolled Steel

Aluminium coatings that are formed by physical vapour deposition (PVD) on rolled steel products are more resistant to atmospheric and seawater corrosion than zinc coatings. We developed a coating thickness analyzer (CTA) with an X-ray fluorescence (XRF) measuring head, that is integrated into the PVD pilot line. In this study, to conduct measurements of elements with atomic numbers less than 20 while avoiding the problem of registration of light elements, the measuring head was integrated into a process vacuum chamber to maintain a vacuum during the measurements. To validate the proposed tool, cold-rolled steel strips of different grades are used as substrates, and aluminium was deposited on the surface via PVD in thicknesses ranging from 1 to 20 g/m2. The thin-film thickness measurements during a pre-acceptance test were found to have a relative accuracy of less than 5% and a relative precision of less than 1–2%. The proposed CTA can be readily integrated in the factory’s automatic process control system and the real-time measurements in operating and calibration modes, and the status of all spectrometric equipment (X-ray tube, detector etc.) can be transmitted to the upper-level computer. Thus, the process engineer can properly control the deposition process

Application of Industrial XRF Coating Thickness Analyzer for Phosphate Coating Thickness on Steel

The results of industrial application of an online X-ray fluorescence coating thickness analyzer for measuring the thickness of phosphate coatings on moving steel strips are considered in the article. The target range of coating thickness to be measured is from tens to hundreds of mg/m2 in a measurement time of 10 s. The measurement accuracy observed during long-duration factory acceptance test was 10–15%. The coating thickness analyzer consists of two XRF gauges, mounted above and below the steel strip and capable of moving across the moving strip system for their suspension and relocation and electronic control unit. Fully automated software was developed to automatically and continuously (24/7) control both gauges, scanning both sides of the steel strip, and develop and test methods for measuring new coatings. It allows performing offline storage and retrieval of the measurement results, remotely controlling the analyzer components and measurement modes from a control room. The developed XRF coating thickness analyzer can also be used for real-time measurement of other types of coatings, both metallic and non-metallic

Optimization of array design for TIBr imaging detectors.

Thallium bromide (TlBr) has attracted attention as an exceptional radiation detector material. Due to its high atomic number (81 for Tl, 35 for Br) it has excellent stopping power for hard X-ray and gamma rays and due to its high bandgap (2.7 eV) its operation requires no or only modest cooling. Promising energy resolutions have been demonstrated with detectors fabricated from high-purity samples (3.3 keV for 60 keV photons). These properties make TlBr the material of choice for hard X-ray imaging spectrometers in applications where small weight and/or size is important (e.g. space astrophysics and nuclear medicine). The charge response and spectroscopic performance of a semiconductor imaging array depend not only on material properties but on the pixel properties as well. It has been demonstrated, for instance, that the ratio between pixel size and thickness of the detector is an important factor for the charge response. This is known as the small-pixel or near-field effect. In this paper we investigate the optimization of TlBr pixel properties in a broader context, taking into account material properties (electron and hole mobility, diffusion and trapping), fabrication details and the specific energy range of application, with a view to optimizing both the response and energy resolution