Kume Takehiro, Hiraguri Kentaro, Imamura Yoichi, Matsuzawa Yusuke, Saito Takahiro, Miyashita Hiroaki, Takeo Yoko, Senba Yasunori, Kishimoto Hikaru, Ohashi Haruhiko, Hashizume Hirokazu, Mimura Hidekazu
Technology Center, Natsume Optical Corporation, 1200-29 Kawaji, Iida, Nagano 399-2431, Japan.
The Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan.
Rev Sci Instrum. 2022 Jun 1;93(6):063101. doi: 10.1063/5.0087171.
The monolithic Wolter mirror is an ideal optical device for focusing soft x rays to a submicron-sized spot, with the advantages of high efficiency, large acceptance, achromaticity, and robustness to alignment error. The fabrication process for this type of mirror has not been established because of the difficulty in highly accurate figure measurement of free-form surfaces with small radii of curvature and steep profiles. In this study, we employed tactile scanning measurement for surface characterization to fabricate a high-precision Wolter mirror. First, it was demonstrated that the touch probe measurement did not leave scratches on the raw surface of the mirror substrate. Next, the measurement capability of the surface profiler was assessed, and the data analysis conditions were determined. Finally, the Wolter mirror was fabricated through repeated figure correction based on the tactile measurement, and the figure error of the final surface was evaluated. Wave-optical simulations that used this error as reference suggested that the size of the beam focused by the mirror was equivalent to the theoretical value at 1000 eV. The reflected image with uniform intensity distribution obtained at SPring-8 also revealed the effectiveness of the present fabrication approach based on tactile measurement.
整体式沃尔特镜是一种将软X射线聚焦到亚微米级光斑的理想光学器件，具有效率高、接受角大、消色差以及对对准误差具有鲁棒性等优点。由于难以对具有小曲率半径和陡峭轮廓的自由曲面进行高精度形状测量，这种类型镜子的制造工艺尚未确立。在本研究中，我们采用触觉扫描测量来表征表面，以制造高精度的沃尔特镜。首先，证明了接触式探头测量不会在镜基板的原始表面上留下划痕。其次，评估了表面轮廓仪的测量能力，并确定了数据分析条件。最后，基于触觉测量通过反复的形状校正制造出了沃尔特镜，并评估了最终表面的形状误差。以该误差为参考的波动光学模拟表明，该镜子聚焦的光束尺寸在1000 eV时与理论值相当。在SPring-8获得的具有均匀强度分布的反射图像也揭示了基于触觉测量的当前制造方法的有效性。
