基于LIGA技术的空间X射线成像元件微缝光学的研制和性能研究

X-ray optics for planetary applications are so far prohibitive due to the mass constraint, since the space X-ray telescopes used for astrophysical missions include long and heavy parts as mirrors. Much effort has been put into light-weight and high-resolution X-ray optics exploration for such application. Micro-slot optics (MSO) as a form of X-ray optics with evident advantages attracts increasing interest in recent years. The sidewall surfaces of the micro-slot with very low roughness can be used as mirrors reflecting X-rays with a possible total external reflection due to the less-than-unity refractive index of X-ray, making it ideal for focusing application..MSO fabricated by LIGA technique has more advantages than MPO monopolized by foreign company in terms of fabrication technique in application of Wolter-type imaging optics. The most important parameters of a MSO mirror are the sidewall surface roughness and the aspect ratio of the micro-slot. Ion beam etching technique is chosen considering its non-contact polishing mode and the ability for removing materials in an atomic level. In order to improve the aspect ratio of the micro-slot of MSO, a new process is invented. Metal filter screen and SU8 sheet with micro-slot are used as substrate and cover layer,respectively. The filter screen can increase the adhesion of PMMA and the cover layer can fasten the PMMA columns together to prevent them from falling, which can basically improve the aspect ratio of the PMMA column array, resulting in the improvement of the micro-slot aspect ratio of MSO. Iridium coating on the sidewall of the MPO plate is explored using atomic layer deposition technique to increase the critical angle of X-ray total reflection. The dependence of the X-ray imaging contrast ratio and focusing efficiency on the material and the surface roughness of the mirror will be studied, aiming at supporting the fabrication by understanding the physical mechanism of limiting the high aspect ratio of the micro-slot..The achievement of this project will accumulate experimental data for providing the direction for optimizing fabrication process and enhance the fabrication capacity of LIGA technique on the field in X-ray optics.

微缝光学（MSO）是目前有效面积质量比最大的X射线成像手段，是实现轻重量空间X射线成像的首选。随着国家探空项目的发展，迫切需要打破国际MPO元件的垄断，满足探空战略性自主发展的需要。MSO相比MPO在制备工艺和在Wolter型聚焦光学的应用上更有优势。本项目使用LIGA技术并以离子束抛光技术辅助，研制超光滑侧壁的MSO成像元件，并进行X射线反射率和成像性能的测试分析。具体内容是：采用钢网-PMMA-SU8胶网的独特工艺，制备大面积孤立胶结构阵列，深入理解限制实现大高宽比结构的物理机制，克服国际上使用LIGA技术制备此元件的困难；利用离子束抛光技术对MSO微狭缝侧壁进行抛光，实现超光滑的目标；研究元件侧壁反光层材料、表面粗糙度对X光反射率和成像对比度、集光效率等性能的影响，为提高成像质量提供技术优化方向与实验数据积累，并提高LIGA技术在X射线光学元件领域的加工能力。

微缝光学（MSO）是目前有效面积质量比最大的X射线成像手段，是实现轻重量空间X射线成像的首选。随着国家探空项目的发展，迫切需要新型的低成本轻量化的X射线聚焦手段，满足探空战略性自主发展的需要。MSO相比MPO在制备工艺和在Wolter型聚焦光学的应用上更有优势。本项目使用了LIGA技术并以离子束抛光技术辅助，研制了超光滑侧壁的MSO成像元件，并进行了X射线成像性能的测试分析。具体内容是：采用钢网-PMMA-SU8胶网的独特工艺，制备了大面积孤立胶结构阵列，深入理解了限制实现大高宽比结构的物理机制；利用离子束抛光技术对MSO微狭缝侧壁进行抛光，实现了侧壁粗糙度1纳米左右的水平；对MSO镜片进行X光的聚焦成像性能测试，分析了镜片对焦斑的形状影响，得到了镜片的微结构精度水平；对集光效率进行了测试，得到了现有技术水平与实用需求水平的对比关系；给出了现有技术的工艺环节对提高成像性能的指导方案。