Development Of High Precision Mirrors Using Algorithm-Based Stitching Interferometry And Profile Coating Technique

High precision metrology and deterministic fabrication are two indispensable techniques for making advanced X-ray mirrors. Among the various metrology and fabrication methods, we are currently developing stitching interferometry and profile coating/differential deposition techniques as a first step for this. For the development of curved focusing mirror, stitching interferometry method was studied. It is based on a global stitching algorithm taking into account the information in the overlapped area of several neighboring subapertures to finish the measurement. The method was tested on a spherical mirror with a radius of 100 m. A smallest repeatability error of 0.24 nm RMS over the two-dimensional surface is demonstrated. The stitched result was compared with NOM in Shanghai Synchrotron Radiation Facility to examine the absolute accuracy. Based on the stitching interferometry, a vertical focusing mirror of KB system was fabricated by using the profile coating technique. Through several iterations, an initial sphere mirror was modified into the desire elliptical mirror with a one-dimensional figure error (along the center line) of around 1.49 mu rad RMS over 50 mm length compared with the designed ellipse.