Two Systems for Direct Radiographic Miniaturization
The direct miniaturization of radiographic images is discussed, and two systems are analyzed in detail. The performance and relative advantages of a large, high-performance X-ray image intensifier (¿18-in or 46-cm diameter) and an optically coupled radiographic intensifier are presented. These systems are estimated to have comparable performance and costs. The X-ray image intensifier system is superior in quantum efficiency and gain, while the radiographic intensifier is superior in contrast. While, as expected, the resolution, contrast, and sensitivity of these systems are not as good as a conventional screen-film cassette system under all circumstances, their performance may be adequate for all but the most demanding radiologic applications.
Design Considerations On X-Ray Image Intensifier Systems
1. As a rule it is a difficult task, with any imaging device, to combine high quantum detection efficiency with a high degree of fidelity to the original image. This is particularly true of X-ray imaging systems, due to two main factors: the strong penetrative power of X-rays through matter, and the complex of particle conversion processes involved.
Photoreflectance characterization of vanadium-doped GaAs layers grown by metalorganic vapor phase epitaxy
Abstract We characterized the vanadium-doped (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy. The conductivity of the samples is checked by the Hall effect measurements, and it is n type with electrons concentration ranging from 2×10 13 to 2×10 17  cm −3 . We used the photoreflectance technique (PR) to study the effect of vanadium doping on the optical properties of GaAs. Our experimental results show that the built-in electric field F and the broadening parameter Γ 0 increase with V-doping concentration. Furthermore, the temperature dependence of the built-in electric field and the broadening parameter of GaAs:V samples have been investigated by PR. It has been observed that these parameters increase with increasing temperature. The decrease of the built-in electric field with decreasing temperature is due to the photovoltage effect.We characterized the vanadium-doped GaAs (GaAs:V) layers grown on GaAs substrate by metalorganic vapor phase epitaxy.