Development of advanced thin foil substrate for large X-ray telescope

沃尔特i型光学系统是x射线天文学中应用最广泛的一种光学系统，由共聚焦抛物面和双曲面反射器组成。我们建议为未来高空间分辨率的大型x射线望远镜开发一种具有Wolter光学的先进薄膜衬底。本研究的目的是利用液压机和热成形技术，将薄片制成具有沃尔特几何形状的高级薄片，并演示具有沃尔特几何形状的薄片的复制。(1) Wolter型两段式箔片的研制我们压制了一张长度为200mm /段式、厚度为0.3 mm的Mg箔片，形成了峰峰误差约为+/-30mm的Wolter型箔片。图形误差使我们能够在薄箔上进行复制以实现光滑表面。使用镁合金作为望远镜衬底是首次实验，镁合金有助于减轻x射线望远镜的重量。(2)两级箔的复制已经建立了短箔（100mm长）的复制，但长薄箔（400mm/两级）的复制是我们的第一个实验。我们与名古屋大学合作，尝试复制两阶段箔。表面光滑的薄片成功地从玻璃芯棒上复制出来。我们用ISAS x射线束设备评估了薄片的成像质量。虽然x射线波段的图像质量受到玻璃芯棒精度的限制，但我们演示了薄箔的复制。通过这项研究，我们获得了制作大型x射线反射镜的关键技术。该技术是未来研制高空间分辨率大型x射线望远镜所必需的。

Wolter type-I optics, which are the most widely used in X-ray astronomy, consists of confocal paraboloidal and hyperboloidal reflectors. We proposed to develop an advanced thin foil substrate having the Wolter optics for future large X-ray telescopes with a high spatial resolution. The goals of our research are make an advanced thin foil with the Wolter geometry from one sheet of thin foil by hydraulic press and thermal forming, and to demonstrate replication of the thin foil with Wolter geometry.(1) Development of the Wolter shaped two-stage foilWe pressed one sheet of Mg foil which has a length of 200 mm/stage and a thickness of 0.3 mm, and formed a Wolter shaped foil with a figure error of about a peak-to-peak value of +/-30mm. The figure error enables us to make a replication to realize a smooth surface on the thin foil. The use of Mg foil for a telescope substrate is the first experiment, and Mg alloy is useful to reduce weight of X-ray telescope.(2) Replication of the two-stage foilReplication of a short foil (100mm long) has been established, but the replication of a long thin foil (400mm/two-stage) was the first experiment for us. We tried replication of the two-stage foil in collaboration with Nagoya University. The thin foil with a smooth surface was successfully replicated off from a glass mandrel. We evaluated an image quality of the thin foil with the ISAS X-ray beam facility. Although the image quality in the X-ray band is limited by an accuracy of our glass mandrel, we demonstrated the replication of the thin foil.Through this research, we obtained the key technique to make a large X-ray mirror. This technique is necessary for fabrication of a large X-ray telescope with a high spatial resolution carried on future X-ray missions.