Development of high-resolution and light-weight x-ray optics with deformed silicon wafers

We report on our development of hot plastic deformation of silicon wafer for high-resolution and light-weight X-ray optics. The highly polished silicon wafer with an excellent flat surface is a promising candidate for the next generation space X-ray telescopes. Deformation accuracy and stability, especially if elastic deformation is used, are issues. The hot plastic deformation of the silicon wafer allows us 3-dimensional shaping without spring back after the deformation. As a first step of R & D, we conducted the hot plastic deformation of 4-inch silicon (111) wafers with a thickness of 300 μm by using hemispherical dies with a curvature radius of 1000 mm. The deformed wafer kept good surface quality but showed a slightly large curvature of 1030 mm. We measured the X-ray reflectivity of the deformed wafer at Al K _α 1.49 keV. For the first time, we detected the total X-ray reflection on the deformed wafer. Estimated rms surface roughness was 0-1 nm and no significant degradation from the bare silicon wafers was seen.