In recent years, micro-columnar cesium iodide (CsI) scintillation films remain a highly desirable sensor for digital X-ray imaging due to its superior spatial resolution, bright emission, high absorption efficiency and ready availability. The micro-columnar structure of the CsI scintillation films can reduce the lateral diffusion of scintillation light and greatly constrain the transmission behavior of fluorescence. However, CsI scintillation films exposed to humid air are easily deliquescent and damaged. In this paper, the preparation methods and anti-deliquescence measures of CsI scintillation films in recent years are mainly summarized and their respective characteristics and limitations are also comprehensively compared and analyzed, which can provide a reference for the preparation and application of high-performance CsI columnar microcrystalline scintillation films in the future.
Because of the obvious deformation difference for the alkali resistant glass tubes with different internal stress, in this paper, a new method for evaluating the internal stress and annealing quality of alkali resistant glass tubes based on digital image correlation algorithm is proposed. According to the deformation change rate of alkali resistant glass tube that obtained by digital image correlation algorithm, it can directly determine whether the internal stress meets the production standard. The alkali resistant glass tubes which have undergone abnormal(annealing time less than 5 hours and annealing temperature lower than 630 ℃) and normal annealing operation were selected as samples of experimental group and control group. The samples of these two groups were heated to 200 ℃ and then cooled to room temperature. The displacement fields between deformed images and the initial image are calculated by digital image correlation algorithm and the mean values change rate of the displacement fields are regard as the evaluated basis for the internal stress and annealing quality. Since the new method has many advantages such as simple, efficient and non-contact and only two continuous pictures are required in the detection process, it has been applied in the actual industrial production testing. In addition, this method provides a new approach for the internal stress detection of other solid materials.
The anti-vignetting glass (AVG) is the key material for super-second and third-generation low-light image intensifiers. With the development of low-light night vision technology, the requirements of high precision and low damage are put forward to AVG. However, traditional measurement methods, such as vernier calipers, micrometers, dial indicators, etc., are all contact measurement, which will inevitably cause damage to AVG during the measurement process. They cannot meet the technical requirements for low damage. Non-contact measurement technology is a non-destructive testing method that realizes the geometric measurement of AVG by writing measurement programs and setting measurement parameters. However, due to the special structure of AVG, the non-contact measurement technology has measurement errors and cannot meet the high-precision measurement requirements. In this paper systematically analyzes the causes of errors in non-contact measurement technology by studying the characteristics of the light source, the difference in light intensity, and the way of grabbing contour edges. Through the error correction technology, the error of the non-contact measurement technology is eliminated, the AVG high-precision and low-damage non-destructive testing is realized.
The microchannel plate (MCP) as the most important component of image intensifiers and ultraviolet detectors, is avalanche two-dimensional electron multiplier device. The emission point as a pattern noise, which is characterized by a bright or a flickering point at a fixed position of the fluorescent screen, affects the visual quality and reliability of the MCP. Therefore, eliminating the emission point is an effective way to improve the performances of the MCP. In this paper, the inner wall morphology and structure defect of the channel were studied, the MCPs with different inner wall morphlogies were analyzed by SEM, and the emission point were tested by using the photoelectric imaging integrated tester. Using the above-mentioned research methods, a specific relationship between the inner wall morphology and the emission point was established. According to the field emission theory, the mechanism of the emission point was analyzed and discussed. The results show that the inner wall structure defects of the channel are the main reasons for the emission point. Furthermore, the study found that the matching of the thermal physical properties between core glass and clad glass is the main reason for the occurrence of structure defects. The structure defects of the inner wall can be effectively reduced by optimizing the composition of the glass material, make the two glasses have the suitable performance matching, avoid forming residual pores at the interface position, the inner wall of the channel will have a smooth, defect free microstructure, thereby effectively controlling the emission point of the MCP.
Micro-channel plate (MCP) is a two dimensional arrays of microscopic channel charge particle multiplier. Silicate composition and hydrogen reduction are keys to determine surface morphology of micro-channel wall in MCP. In this paper, lead silicate glass micro-channel plates in two different cesium contents (0at%, 0.5at%) and two different hydrogen reduction temperatures (400°C,450°C) were present. The nano-scale morphology, elements content and chemical states of microporous wall surface treated under different alkaline compositions and reduction conditions was investigated by Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS), respectively. Meanwhile, the electrical characterizations of MCP, including the bulk resistance, electron gain and the density of dark current, were measured in a Vacuum Photoelectron Imaging Test Facility (VPIT).The results indicated that the granular phase occurred on the surface of microporous wall and diffuses in bulk glass is an aggregate of Pb atom derived from the reduction of Pb2+. In micro-channel plate, the electron gain and bulk resistance were mainly correlated to particle size and distribution, the density of dark current (DDC) went up with the increasing root-mean-square roughness (RMS) on the microporous wall surface. Adding cesiums improved the size of Pb atomic aggregation, lowered the relative concentration of [Pb] reduced from Pb2+ and decreased the total roughness of micro-channel wall surface, leading a higher bulk resistance, a lower electron gain and a less dark current. Increasing hydrogen reduction temperature also improved the size of Pb atomic aggregation, but enhanced the relative concentration of [Pb] and enlarged the total roughness of micro-channel wall surface, leading a higher bulk resistance, a lower electron gain and a larger dark current. The reasons for the difference of electrical characteristics were discussed.
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