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.
Vladimir Ryzhykov, Leonid Gal'chinetskii, Konstantin Katrunov, Olga Zelenskaya, Elena Lysetskaya, Nikolay Starzhynskiy, Vyacheslav Chernikov, S. Kostioukevitch, Boris Grin'ov
A new large area detector of high-energy x-ray and b-radiation has been designed and studied. The design includes wedge-shaped light transducers. A composite material based on small crystalline ZnSe(Te) was applied onto the wide surface of light transducer. This design ensures optimum light collection from large sensitive surface onto the output window of much smaller size. An experimental specimen has been prepared, which showed β-sensitivity Cβ=5.5 cm2. The spectrograms of a 90Sr+90Y β-source obtained with the specimen under study make it possible to evaluate the age of the source by the ratio of low- and high-energy regions of the spectrum. Other designs are proposed for application of large-area detectors possessing wedge-shaped light transducers as elements of assembled constructions for high efficiency detectors operating under flow conditions.
Properties are reported of new types of active module 32- channel scintielectronic detectors of 'scintillator- photodiode' type with step h equals 0,8 mm for low-energy x-ray introscopic systems. As scintillator, 'fast' modification of crystal ZnSe(Te) was used in three variants: individual single crystal elements for each channel, a single crystal plate common for all channels, and a small crystalline composite plate with grain size d equals 0,25 divided by 0,5 h. Active detectors based on ZnSe(Te) scintillators and active 32-channel photoarrays with combined pattern of preliminary transformation and sequential sampling ensures x-ray sensitivity of 0,8 divided by 2.
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.
Evaluation was made of changes in scintillation and dynamic characteristics of detection blocks of 'scintillator- photodiode' type based on crystals ZnSe(Te) and CsI(Tl) after long-term storage of unprotected crystals under normal climatic conditions, as well as after action of water vapor. It is shown that changes of energy resolution of large CsI(Tl) crystal are not significant; only the radiation noise threshold is changed due to the phosphorescence of the disturbed surface layer of the crystal. For single crystals ZnSe(Te), which are used for spectrometry of charged particles and short-range gamma-radiation as thin plates, both dynamic noise threshold and spectrometric characteristics are changed. Possibilities to restore the initial crystal properties are discussed, and ways to protect the crystal surface from environmental effects are considered.
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