The film radiographic inspection remains among the most reliable methods for inspection of pipelines and metalwares.
The worldwide trend of transition from film radiography to digital radiography requires creation of advanced digital
radiography systems. The main direction of digital radiography systems development is improvement of spatial
resolution. The pixel size of the X-ray film is several microns, while solid-state detector pixels have dimensions of
several hundred or several thousand microns. For the most common detectors of "scintillator-photodiode" type, it is
impossible in principle to obtain the film pixel sizes. However, the detecting ability for substances that differ by their
density and atomic number achieved using "scintillator-photodiode" detectors is by several orders higher. Using a
standard experiment scheme with dual-energy detector arrays, our aim was to show that it could be possible to
substantially increase the accuracy of supervision of the inspected object. For obtaining shadow X-ray images, a
receiving-detecting circuit with a detector array was developed for 200 mm scanning field. Using model digital
radiographic systems and standard testing we have evaluated spatial resolution (not worse than 1.25 line pairs/mm) and
detecting ability (better than 0.2 mm steel wire behind 6 mm steel).
Development and studies of characteristics are reported for X-ray radiation detectors of "scintillator-photodiode" type
showing improved spatial resolution with photosensitive area step of 1.6, 0.8, 0.4 and 0.2 mm and number of channels
16, 32, 128 and 256, respectively. The receiving-detecting channel has been adjusted and tested, appropriate software has
been developed, and shadow X-ray images of tested objects were obtained. Evaluations were made of spatial resolution,
resolution over thickness and detecting ability of the digital radiographic sysyem based on the detector array.
Recommendations are formulated on application of such devices for non-destructive testing and technical diagnostics.
Further studies on obtaining two-energy images show possibilities of substantial broadening of the application fields of
the digital radiographic system, allowing determination of the effective atomic number Zeff for component substances of
the tested objects. A possibility is shown of substance discrimination by their effective atomic number even for "light"
elements with Zeff from 6 to 13. Clear distinction could be observed between such substances as water (H2O) with
Zeff≈7.43 and glycerol (CH2OHCHOHCH2OH) with Zeff≈ 6.87.
We used detector arrays of types "scintillator-photodiode" (S-PD) and scintillator-photoreceiving device (PRD). In non-destructive testing systems using S-PD arrays it is possible to use scintillators of different atomic number and density, which allows functioning in the energy range from 20 keV to 10 MeV, i.e., steel equivalent thickness I from 100μm to 300mm. For different objects and different purposes, different types of detector arrays and methods of control can be recommended. Results of experimental studies of detector arrays S-PD and S-PRD used for X-ray digital radiography have shown that there exist further possibilities to increase spatial resolution of this system for up to 2-3 line pairs per mm. It was investigated experimental results with used two array detectors for low-energy and high - energy detections (HED and LED). It is show in principle to distinguish not only organic from inorganic materials, but so as safety organic from explosive. Our aim was to show (theoretically and experimentally) that is could be possible to substantially increase the accuracy of separation of substances in the inspected object by their atomic number, as well as to increase the sensitivity of the method as a whole by using a multi-energy approach and detectors that have substantially different sensibility in the low-and high-energy range of the X-ray emitter spectrum. It was show the possibility to distinct materials with effective atomic number difference about 10-15%. It can be used in inspection systems, including anti-terrorist activities, in technical diagnostics, medicine.
A thermodynamic analysis has been carried out for interaction of the components in the ZnSe-ZnTe-Se-H2-C system. Studies of thermodesorption, thermodynamics and kinetics of interaction reactions in the ZnSe-ZnTe-Se-H2-C system indicate high probability of formation of fine-dispersed fullerene-like particles of hydrated carbon black in this system at the stage of ZnSe(Te) charge synthesis. It has been established that carbon black particles preserve their stability at the stage of ZnSe(Te) crystal growth and can substantially affect crystallophysical, optical and physico-chemical properties of these crystals.
Electro optical characteristics of the semiconductor compounds has been researched from the discovery of the semiconductor materials. One of the perspective ideas in this field was the possibility to obtain "cool" phosphorescence’s by means of the relaxations of the energy by recombination of excited electroni -holder pairs. In this work the conditions of obtaining of the electro luminescent structures based ZnSe(Te), their characteristics and structure of optical - and electro-luminescence centers are investigated. The Structure Me|ZnSe(Te):Zn|ZnO|ITO has shown the characteristics of the led, having bands of the radiation in the field of 540, 640 and 740 nm. The branch of the direct mode had a negative nonmonotonic area, because the thickness of ZnO quantum-dimensioned. The resemblance o
the spectrums of electroluminescence of the crystals in abundance of Zn and film structures, which were obtained using the method of vacuum condensation results in that surface, cathode, nature of luminescence of ZnSe(Te) is possible to b explained in account of injection of the carriers in semiconductor.
Relationship has been studied between preparation conditions of the raw charge, crucible material, growth regimes and structure defectness and electrophysical properties of crystals Cd1-xZnxTe. The crystals were grown both from the raw material which had been pre-synthesized in quartz ampoules, and from the raw material synthesized from the elements directly in the growth furnace. It is shown that the best values of electric resistivity (rho) and sensitivity to x-ray and gamma-radiation are obtained for crystals grown in crucibles of highly pure coal graphite material from the pre-synthesized raw charge. Correlation has been established between values of (rho) and crystal defectness: decrease of dislocation density by 104 times led to 107 times higher values of resistivity. Concentration of dislocation etching pits regularly decreased with higher purity of the raw material and optimization of crystal preparation technology.
Scintillators based on AIIBVI compounds, having relative small effective atomic numbers, can be used for measurement and spectrometry of fluxes of light and heavy charged particles. In this paper we attempted to specify the possibilities and limitations of the development of new types of solid-state detectors of charged particles and corresponding instruments on the basis of CdS(Te) and ZnSe(Te) scintillator single crystals produced by STC RI of the Concern `Institute for Single Crystals'. Principal attention was paid to a promising system S-PD-PA, combined with modern computer facilities. For the best specimens of instruments, we obtained energy resolution for alpha- particles with E(alpha ) equals 5.15 MeV R(alpha ) equals 4- 5%, for electrons with Ee equals 0.624 MeV equals Re equals 11-12%, alpha to beta ratio (alpha) /(gamma) equals 1.0 +/- 0.1, beta to gamma ratio (beta) /(gamma) - more than 100. A possibility is discussed of a combined method of detection and spectrometry of electrons in the energy range of 0.015 - 3.0 MeV using a windowless silicon PIN-PD (0.01 - 3.0 MeV), as well as a scintillation detector comprising a scintillator and a PIN-PD (0.2 - 3.0 MeV).
The evolution of the radioluminescence (RL) spectra and spectral-kinetic characteristics of ZnSe100-xTex (0.01 <EQ x <EQ 0.96) crystals were studied at 77 K as a function of concentration of metallic Se added to the initial charge. The crystals were grown from the melt under argon pressure. The elemental composition of the samples was checked by x-ray luminescence and chemical analysis. It is shown that, depending upon the degree of doping with Te, different RL bands compete with each other. Thus, at 0.01 <EQ x <EQ 0.20 the short-wave luminescence should be probably treated as a self-activated luminescence band caused by recombination in the complex {V Zn- + D+}, where V is the Zn vacancy, a D-donor. The green-blue luminescence at 0.20 <EQ x <EQ 0.96 can be probably associated with Te clusters, while the formation of the `green' RL band is presumably due to Zn vacancies. The presence of the intense `red' band in ZnSe100-xTex samples, corresponding to the whole range of x, is considered as an indication of the fact that the luminescence center {V Zn- + Te0 + Zn+} comprises the isovalent dopant Te and the excess Zn.
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