Research for fabrication method of ultra thin mirror substrate for high throughput X-ray telescope using diamond machining

角分辨率的提高是未来高通量x射线天文任务中研制高通量x射线望远镜的重要问题之一。为此，制作精确镜像图形的工艺是一项关键技术。我们开发了一种用于高通量x射线望远镜的超薄反射镜的新方法，其设计目标是角分辨率达到1弧分（半能宽）。该方法采用由水溶性胶粘剂制成的特殊支撑夹紧结构，对铝镜面基片进行金刚石加工成形。控制金刚石加工过程中基片的内部应变是实现图形误差最小化的关键工艺之一。采用浸漆法获得光滑的表面，并采用真空沉积法在表面镀上一层金。利用这种方法，我们制作了直径为150 mm、高度为100 mm、掠射角为1度、不同厚度的锥形反射镜。我们发现这种方法可以提供厚度低至0.3 mm的超薄衬底。初步的机械、光学和x射线测试结果表明，二级圆锥反射镜系统的角分辨率为1.7弧分（半能宽）。

An improvement of angular resolution is one of the most important provlem in the development of high throughput X-ray telescope for future X-ray astronomy missions. For this purpose, a process to make precise mirror figure is a critical technology.We have developed a new method to make ultra thin mirror for the high throughput X-ray telescope, whose design goal is an angular resolution of 1 arc min(half energy width). In this method, aluminium mirror substrate is figured by diamond machining using special support and chucking structure made of water solvable adhesive. One of a critical process to minimize the figure error is to control of internal strain of substrate generated by the diamond machining. The smooth surface is obtained by dip lacquering and the reflective layer is gold coated on this surface by the vacuum deposition.Using this method, we have made test conical mirrors with the diameter of 150 mm, the height of 100 mm, grazing angle of 1 degree and various thickness. We found that this method can provide ultra thin substrate of thickness down to 0.3 mm. The first results of mechanical, optical and X-ray test indicate that angular resolution is 1.7 arc min(half energy width) for 2 stage conical mirror system.