System Development for Fabricating Mandrel of Soft X-ray Rotating-Body Mirror (1st Report): Deveropment of Shape Correction Processing System for Circumferential Direction

We have developed the deterministic figure correction process for fabricating the mandrel of a soft x-ray mirror. In this process, the figure correction is performed on the basis of the measured profile. We used roundness measuring machine equipped with a rotary air-bearing stage and laser displacement sensors. Repeatability higher than 1 nm was achieved by averaging the 10 measured profiles. We employed nozzle-type EEM (Elastic Emission Machining) to remove the surface material with a controllability of 1 nm. In the figure corrections, the dwelling time distribution of the EEM head is a parameter to adjust the removal profile. In this study, a rod lens was used as the test sample. The figure error of a profile in the circular direction could be improved. Finally, the circularity was achieved to be 10 nm in peak to valley.