17 September 2012 Functional tests of modular elements of segmented optics for x-ray telescopes via an expanded beam facility
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Abstract
Future large X-ray observatories will be equipped with very large optics obtained by assembling modular optical elements. The final quality of the modular optic is determined by the accuracy in the assembly alignment, but also by the compliance of the focusing elements to the nominal shape and the roughness tolerance in order to avoid excessive levels of X-ray scattering. Because of the large number of modules, quality tests need to be routinely performed to assess the technology readiness, and, in a later phase, to select the most performing stacked blocks to be integrated into the final optic. Besides the usual metrology based on profile and roughness measurements, a direct, at-wavelength, focusing measurement in X-rays would be the most reliable test. Synchrotron light beams are in general not sufficiently broad to cover the aperture of a block without scanning it, which requires a focal spot reconstruction. To this end, we designed a 12 m long X-ray facility to be realized at INAF/ OAB, devoted to the functional tests of the focusing elements. A grazing incidence parabolic mirror and an asymmetric Silicon crystal will produce a wide, parallel, and uniform beam of X-rays to illuminate the entire aperture of the focusing elements. A X-ray camera at the focal distance from the mirrors directly records the image. The tests will be performed at 4.5 keV, with the components operating in gaseous Helium to minimize the absorption.
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Daniele Spiga, Daniele Spiga, Giovanni Pareschi, Giovanni Pareschi, Carlo Pelliciari, Carlo Pelliciari, Bianca Salmaso, Bianca Salmaso, Gianpiero Tagliaferri, Gianpiero Tagliaferri, "Functional tests of modular elements of segmented optics for x-ray telescopes via an expanded beam facility", Proc. SPIE 8443, Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray, 84435F (17 September 2012); doi: 10.1117/12.927280; https://doi.org/10.1117/12.927280
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