
Proceedings Paper
X-ray optical systems: from metrology to Point Spread FunctionFormat | Member Price | Non-Member Price |
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Paper Abstract
One of the problems often encountered in X-ray mirror manufacturing is setting proper manufacturing tolerances to
guarantee an angular resolution - often expressed in terms of Point Spread Function (PSF) - as needed by the specific
science goal. To do this, we need an accurate metrological apparatus, covering a very broad range of spatial frequencies,
and an affordable method to compute the PSF from the metrology dataset. In the past years, a wealth of methods, based
on either geometrical optics or the perturbation theory in smooth surface limit, have been proposed to respectively treat
long-period profile errors or high-frequency surface roughness. However, the separation between these spectral ranges is
difficult do define exactly, and it is also unclear how to affordably combine the PSFs, computed with different methods
in different spectral ranges, into a PSF expectation at a given X-ray energy. For this reason, we have proposed a method
entirely based on the Huygens-Fresnel principle to compute the diffracted field of real Wolter-I optics, including
measured defects over a wide range of spatial frequencies. Owing to the shallow angles at play, the computation can be
simplified limiting the computation to the longitudinal profiles, neglecting completely the effect of roundness errors.
Other authors had already proposed similar approaches in the past, but only in far-field approximation, therefore they
could not be applied to the case of Wolter-I optics, in which two reflections occur in sequence within a short range. The
method we suggest is versatile, as it can be applied to multiple reflection systems, at any X-ray energy, and regardless of
the nominal shape of the mirrors in the optical system. The method has been implemented in the WISE code,
successfully used to explain the measured PSFs of multilayer-coated optics for astronomic use, and of a K-B optical
system in use at the FERMI free electron laser.
Paper Details
Date Published: 17 September 2014
PDF: 16 pages
Proc. SPIE 9209, Advances in Computational Methods for X-Ray Optics III, 92090E (17 September 2014); doi: 10.1117/12.2061657
Published in SPIE Proceedings Vol. 9209:
Advances in Computational Methods for X-Ray Optics III
Manuel Sanchez del Rio; Oleg Chubar, Editor(s)
PDF: 16 pages
Proc. SPIE 9209, Advances in Computational Methods for X-Ray Optics III, 92090E (17 September 2014); doi: 10.1117/12.2061657
Show Author Affiliations
Daniele Spiga, INAF—Osservatorio Astronomico di Brera (Italy)
Lorenzo Raimondi, Elettra Sincrotrone Trieste S.C.p.A. (Italy)
Published in SPIE Proceedings Vol. 9209:
Advances in Computational Methods for X-Ray Optics III
Manuel Sanchez del Rio; Oleg Chubar, Editor(s)
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