基于负压热弯玻璃镜片的Wolter-I型X射线聚焦望远镜关键技术研究

X-ray focusing optics is one of the most important technologies for X-ray astronomy with capabilities of direct imaging, low background and high sensitivity. The observing and imaging of the highly energetic object by using the X-ray imaging telescope with high performance make it possible to understand the formation and structure of the universe. Enhanced X-ray Timing and Polarimetry Mission (eXTP) is a science mission designed to study the state of matter under extreme conditions of density, gravity and magnetism. The Polarimetry Focusing Array (PFA), a set of 4 X-ray telescopes, can reach the high angular resolution of less than 30 arc-seconds. The nested Wolter-I type X-ray telescope has high-throughput, compact and good imaging properties and is a hot topic in recent years for X-ray observational tools as well. Further, the nested X-ray imaging telescope with high resolution and high effective collecting area are the base of the research on a variety of astronomical objects. Unfortunately, there is not any successful example in China for making X-ray imaging telescope，because of the difficulty of mirror fabrication and telescope integration. It is very important to develop this kind of telescopes, both for eXTP project and for X-ray astronomy observation in our country..This project will focus on the research of thin glass slumping and integration of X-ray imaging telescope with slumped glass segments in order to reach 30 arc-seconds angular resolution. This project is put forward a new thin glass segment fabrication method, which is based on high precision porous ceramic mold and a vacuum assisted thermal slumping glass technology, to making angle second precision segments. Paraboloid-hyperboloid composite mirror can realize the integration between primary and secondary mirror, which will reduce the difficulty of telescope assembly. The improved on-machine measurement technique and ray tracing method for nested telescope will help quantitatively analyzing the accuracy change of the segments and optimizing the "online detection, simulation assessment and feedback "assembly process. .All of these breakthroughs in key technologies in the nested Wolter-I telescope will lay the foundations for eXTP project and Chinese X-ray astronomy observation.

X射线聚焦光学技术是X射线天文学最重要的技术之一，具有直接成像能力和高灵敏度的特点，推动X射线天文学成为了观测宇宙新窗口。我国已提出增强型X射线时变与偏振卫星（eXTP），其独特的偏振聚焦望远镜阵列（PFA）要求至少30角秒角分辨率。嵌套式标准Wolter-I型聚焦望远镜是满足eXTP PFA要求的唯一形式，但镜片制作难、装配要求高，我国尚未有成功研制角秒级分辨率X射线望远镜的先例。我国目前仅仅只有少数单位在开展X射线聚焦望远镜研究，且最高角分辨率仅有3角分左右，因此eXTP FPA的聚焦望远镜只能通过国际合作方式研制。开展相关技术自主研究，对推进eXTP FPA的国产化和主动权，以及X射线天文具有重要科学价值和意义。.本项目在综合比较了超薄玻璃热弯镜片技术、镍电镀镜片技术和硅孔光学技术的基础上，提出采用多孔陶瓷模具、负压热弯成形技术制作高精度“抛物面-双曲面”超薄玻璃镜片，获得角秒级分辨率的高精度镜片；在嵌套式镜片装配方法上，发展嵌套式望远镜装配在线检测和掠入射光线高效追迹方法，定量分析镜片装配精度变化规律，优化“在线检测-模拟评估-反馈”装配流程和方法，力争突破角秒级精度镜片制作和角秒级望远镜装配两大关键技术，实现角秒级分辨率X射线聚焦望远镜研制。.该项目的完成，有望支持我国自主研制角秒级X射线聚焦望远镜，对改变我国在高精度X射线聚焦望远镜研制上只能依赖进口的局面，对提升eXTP的自主研制比例和推动我国X射线天文观测都有重要意义。

X射线聚焦光学技术是X射线天文学最重要的技术之一，具有直接成像能力和高灵敏度的特点，推动X射线天文学成为了观测宇宙的新窗口。我国已提出增强型X射线时变与偏振卫星（eXTP）,，都需要大集光面积高角分辨的X射线聚焦望远镜。嵌套式标准Wolter-I型聚焦望远镜是满足这种要求的唯一形式，但我国尚未有成功研制角秒级分辨率嵌套式望远镜的先例。.本项目提出基于负压热弯成形制作玻璃镜片的Wolter-I型X射线聚焦望远镜关键技术研究。采用单点金刚石车削和抛光的复合制作技术制作了Wolter-I型X射线显微镜芯轴。总结了车削后NiP合金表面微观形貌的产生规律，揭示了NiP合金表面微观形貌的形成机理，建立了NiP合金表面微观形貌与车削参数间的量化关系和表面微观形貌与表面衍射的关系。采用了半刚性盘机械抛光方法，实现了Wolter-I芯轴抛光，制作了面形优于±50nm表面粗糙度均方根值为0.66nm，在5μm×5μm区域内的为0.23nm，Wolter-I型X射线显微镜芯轴。.通过对现有的热成形炉进行改造，设计制作了热真空负压镜片成形装置，通过基于面积均分的气道设计和抽气孔布局方案，获得了均匀的抽气负压分布。优化超薄镜片的热成形工艺，获得了30角秒精度的薄玻璃镜片。.对望远镜研制全流程的误差来源和精度控制进行了全面分解，构建了高精度“在线检测-模拟评估-反馈”的装配流程和方法，发展超薄玻璃镜片在线装配检测技术，掌握了镜片装配精度变化规律，研制了多台望远镜样机。其中焦距2m的X射线聚焦望远镜样机角分辨率为58″±2″@1.49keV，和美国NuSTAR相当，由于望远镜焦距仅有2m，理论几何误差HPD49″，远大于10m焦距的NuSTAR 14″的理论误差，表明望远镜的镜片制作和装配精度优于美国NuSTAR望远镜，Wolter-I型聚焦望远镜装配精度优于30角秒。本项目的成果将有力支撑我国相关X射线天文望远镜的研制。