CsI（Tl）膜抗潮解技术及光转换组件结构设计研究

发布时间：2018-06-24 09:18

本文选题：掺铊碘化铯薄膜 + 抗潮解　；参考：《电子科技大学》2017年硕士论文

【摘要】：闪烁体X射线探测器在医用检测和安检等方面都有很重要的应用。而其中掺铊碘化铯由于它的光学性能很好、成本低和易于生长等优点成为了热门的闪烁体材料。就材料本身而言,虽然掺铊碘化铯性能出众,但是由于它易潮解的特性,当它暴露在潮湿空气中时会使得其光转换性能下降,因此对抗潮解掺铊碘化铯的研究就显得非常重要;就闪烁体X射线探测器件而言,X射线经过闪烁体后转化为发散的可见光并且由于闪烁体存在转换效率,部分X射线会直接进入CCD并对CCD造成辐射损伤。因此需要设计光转换组件来收集可见光信号及分离X射线与可见光。因此,本文从理论与实验上研究了潮解对掺铊碘化铯薄膜结构与性质的影响并且设计出针对掺铊碘化铯薄膜的抗潮解方案,并对X射线探测器光转换组件进行了设计及优化。首先,本文从通过对掺铊碘化铯薄膜傅里叶红外光谱的测试,证实了其暴露于潮湿空气中的潮解现象。然后研究了掺铊碘化铯薄膜暴露于不同湿度的潮湿空气对其结构以及荧光光谱的影响并分析了原因,结果表明掺铊碘化铯薄膜暴露在相对湿度更高的潮湿空气中更长时间,其光转换性能下降越多。其次,针对掺铊碘化铯薄膜易潮解的特性设计了多种抗潮解方案。最终选择了铝保护膜层、二氧化硅保护膜层以及氮化硅保护膜层作为掺铊碘化铯薄膜的保护膜层。为了确保保护膜层能尽量地使得可见光信号透过,对三种保护膜层对可见光的透射图谱做了仿真并设计了达到对目标波长光的高透过率需要的膜层具体厚度。最后运用磁控溅射法与PECVD技术制备了三种保护膜层,并测试分析了它们对掺铊碘化铯薄膜的抗潮解效果,结果表明铝抗潮解保护膜的综合性能最好。之后,根据对X射线探测器光转换组件设计的要求并通过成像计算公式计算得到了基础光转换组件的设计参数。根据设计参数在ZEMAX上搭建了基础光转换组件的光路图并对基础光转换组件的成像质量进行了全面的评价。最后,由于设计的基础光转换组件的成像质量并不理想,利用ZEMAX建立合适的优化函数对基础光转换组件的成像质量进行了优化。虽然优化后光转换组件的综合像差、波前光程差、像散等均有了较大的改善,但是弥散斑和衍射能力上仍存在较大不足。在受到三片式物镜的启发下对光转换组件进一步优化,设计出了三透镜光转换组件。在对优化后的三透镜光转换组件的成像质量的评价中,发现其在各个方面均有了很大的改善,成像质量已经基本达到了要求。因此将使用这一优化后的三透镜光转换组件设计作为实际光转换组件设计的重要参考模型来完成后续的整体X射线探测器的设计。
[Abstract]:Scintillator X-ray detectors have important applications in medical detection and security inspection. Among them, thallium-doped cesium iodide has become a popular scintillator because of its good optical properties, low cost and easy growth. As far as the material itself is concerned, although the properties of thallium iodide doped cesium iodide are outstanding, it is very important to study the resistance of thallium iodide doped cesium iodide when exposed to moist air. As far as scintillator X-ray detector is concerned, X-ray is transformed into divergent visible light after it passes through scintillator. Because of the conversion efficiency of scintillator, some X-ray rays will enter CCD directly and cause radiation damage to CCD. Therefore, a light conversion module is needed to collect visible light signals and separate X-ray from visible light. Therefore, in this paper, the influence of tidal decomposition on the structure and properties of thallium-doped cesium iodide films is studied theoretically and experimentally, and the anti-moisture scheme for thallium-doped cesium iodide films is designed, and the X-ray detector photoconversion module is designed and optimized. Firstly, the FT-IR spectra of thallium iodide doped cesium iodide films are measured and the results show that they are exposed to moist air. Then the effects of thallium-doped cesium iodide film on the structure and fluorescence spectrum of the thin film exposed to moist air with different humidity were studied. The results show that thallium doped cesium iodide film is exposed to higher relative humidity in humid air for a longer time. The more the optical conversion performance decreases. Secondly, according to the characteristics of thallium iodide-doped cesium iodide film, a variety of anti-moisture solution schemes are designed. Finally, aluminum protective film, silica protective film and silicon nitride protective film are selected as the protective film of thallium-doped cesium iodide film. In order to ensure that the protective film can make the visible light signal pass through as much as possible, the transmission spectra of the visible light of the three protective coatings are simulated and the specific thickness of the film to achieve the high transmittance of the target wavelength light is designed. Finally, three kinds of protective coatings were prepared by magnetron sputtering and PECVD technique. The results showed that the comprehensive properties of the protective films were the best for thallium iodide doped cesium iodide films. After that, the design parameters of the basic optical conversion module are calculated according to the requirements of the design of the X-ray detector photoconversion module and the imaging calculation formula. According to the design parameters, the optical circuit diagram of the basic optical conversion module is built on ZEMAX and the imaging quality of the basic optical conversion module is evaluated comprehensively. Finally, because the imaging quality of the designed basic optical conversion module is not ideal, the imaging quality of the basic optical conversion module is optimized by using ZEMAX to establish an appropriate optimization function. Although the synthesis aberration, wavefront optical path difference and astigmatism of the optimized optical conversion module have been greatly improved, the diffusivity and diffractive ability are still largely inadequate. A three-lens optical conversion module is designed by optimizing the optical conversion module inspired by a three-slice objective lens. In the evaluation of the imaging quality of the optimized three-lens optical conversion module, it is found that it has been greatly improved in all aspects, and the imaging quality has basically met the requirements. Therefore, this optimized three-lens optical conversion module is used as an important reference model for the practical optical conversion module design to complete the subsequent design of the overall X-ray detector.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TL816.1;O484

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