LNLS, Campinas, Brazil
Next-generation nanoprobes, empowered by diffraction-limited storage rings, as Sirius/LNLS, present high-performance requirements aiming at high spatial resolution and throughput. For the focusing optics, this means assuring a small and non-astigmatic probe, high flux density, and remarkably high position stability, while also preserving beam wavefront. At stations further dedicated to spectromicroscopy and in-situ experiments, these requirements add up to having achromatic design and suitable working distance, respectively. In this way, Kirkpatrick-Baez (KB) mirrors have been chosen as the most appropriate solution for Sirius focusing optics. At TARUMÃ*, the first delivered nanoprobe at Sirius, the KB focuses the beam down to a 120 nm spot size (>8 keV) with a 440 mm working distance. This brought the requirements on the mirror’s angular stability to less than 10 nrad RMS, surface quality to single-digit nanometers, and alignment tolerances to the range of hundreds of nrad, which can be even tighter for other nanoprobes. Such specifications are particularly challenging regarding clamping, vibration, and thermal expansion budgets, even testing optical metrology limits during alignment and validation phases. The resulting KB mechanism is an opto-mechanical system with an exactly-constrained, deterministic design**, and suspension modes well above 250 Hz, sufficiently coupling optics to sample in the same 6-DoF base. It provides low-order aberration corrections by single degree-of-freedom alignment with piezo actuators, while higher order aberrations from clamping and thermal deformations are mitigated by gluing each mirror to flexure-based mounting frames. This contribution presents the design, assembly, and commissioning of the KB system at TARUMÃ as a reference case.
*Tolentino, H.C.N., et al. "TARUMÃ station for the CARNAÚBA beamline at SIRIUS/LNLS" SPIE 11112 19
**Geraldes, R.R., et al. "The Design of Exactly-constrained X-ray Mirror Systems for Sirius." MEDSI18
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