At 4th-generation synchrotron nanoprobes with optimized photon density, focusing optics systems often require mirrors arrangements with high demagnification factors to achieve diffraction-limited beam sizes (∠ 100 nm) and still high photon flux. All the components’ contributions to the surface error must be at the same level (a few nanometers) and angular stability (lower than 10 nrad RMS) becomes a bottleneck issue. Therefore, the design of ultra-stable mirror mechanics has to follow a systems perspective, where precision engineering, metrology and alignment strategies are considered simultaneously. For the latest design at Sirius/LNLS, an exactly-constrained KB set with minimum number of adjustment degrees for increased stiffness and stability was also bounded by an alignment error budget in the order of tens of microns by construction, pushing metrology limits during alignment and validation phases. This work presents a two-phase strategy for metrology-assisted assembly and figure validation of elliptical mirror sets, starting at a Fizeau Interferometer system (FZI) and finishing at a Coordinate Measuring Machine (CMM). The first phase validates surface quality by scanning mirror position and automatically realigning interferometry fringe patterns, while pixel-level stitching techniques are employed to characterize the surface error over the mirror’s length. The stitching algorithm includes self-calibration of lens errors and uses multiple CPU cores for expedite processing. The second phase consists of fiducializing the elliptical figures of each mirror into their own substrates and assembling both mirrors with regard to each other by using a least-squares fit of the center and rotation angle of each fixed ellipse, obtained from the manufacturer’s documentation, and confirmed at the first phase. This workflow was applied and demonstrated at an ultra-stable exactly-constrained KB system, reaching sufficient alignment accuracy.
Side-deflecting cylindrical mirrors with sagittal curvature horizontally deflect and focus the beam in the vertical direction. This optical scheme applied to fourth-generation synchrotron light source beamlines has potential advantages leading to nearly aberration-free focus and variable beam size or focus position. We characterize the surface quality of sagittal cylinders in the low spatial frequency range with the long trace profiler (LTP) and the Fizeau interferometer (FZI). In the standard LTP, the sagittal curvature of the cylindrical mirror causes the reflected laser beam to diverge, which consequently shifts the focus out of the detector plane, turning a reliable measurement impossible. Therefore, a positive cylinder lens is placed at Cat's eye position to recollimate the beam. In this paper, we describe the alignment procedure and dene the required accuracy of each degree of freedom for both the cylinder lens and the cylindrical mirror to be characterized. Measurements with the FZI are limited to optics with small curvatures when measuring with a flat reference. We show that measuring a sagittal cylinder slightly out-of-focus overcomes this limitation. Measurements with the FZI also allow to characterize the deformations caused by clamping forces due to fixation. We compare the measured deformation with Finite Element Analysis (FEA) simulation results. We present measured surface height and slope profiles (LTP and FZI) of cylindrical mirrors for SIRIUS beamlines.
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