Kume Takehiro, Takei Yoshinori, Egawa Satoru, Motoyama Hiroto, Takeo Yoko, Yamaguchi Gota, Mimura Hidekazu
Department of Precision Engineering, Graduate School of Engineering, The University of Tokyo, 7-3-1 Bunkyo-ku, Hongo, Tokyo 113-0033, Japan.
Rev Sci Instrum. 2019 Feb;90(2):021718. doi: 10.1063/1.5057432.
An x-ray ellipsoidal mirror is an ideal tool for focusing soft x-rays. Because nanometer-level shape accuracy is required in the internal surface of a mirror having a small diameter, it is difficult to fabricate the mirror by processing the surface directly. We developed a fabrication process for soft x-ray ellipsoidal mirrors in which the surface of a high-precision quartz mandrel with the inverted shape of the designed mirror is replicated by nickel sulfamate electroforming. In this study, an ellipsoidal mirror of 40-mm length was fabricated and the shape accuracy of the replicated surface was evaluated by a measurement method using a contact probe. The root mean square (RMS) of the replication error in the entire measured surface was 27.2 nm. When the evaluated area was half the replicated surface near the middle of the mirror, the RMS of the replication error was 14.7 nm. Wave-optical simulation suggested that it is possible to focus soft x-rays to a spot with a diameter of 400 nm.
X射线椭球面镜是聚焦软X射线的理想工具。由于小直径镜面的内表面需要纳米级的形状精度，直接加工表面来制造镜面很困难。我们开发了一种软X射线椭球面镜的制造工艺，其中通过氨基磺酸镍电铸复制具有设计镜面倒置形状的高精度石英芯轴的表面。在本研究中，制造了一个长度为40毫米的椭球面镜，并通过使用接触式探头的测量方法评估复制表面的形状精度。整个测量表面复制误差的均方根（RMS）为27.2纳米。当评估区域为镜面中部附近复制表面的一半时，复制误差的RMS为14.7纳米。波光学模拟表明，有可能将软X射线聚焦到直径为400纳米的光斑上。
