Many synchrotron experimental techniques require a variable size x-ray photon beam on the sample or on the detector. The easiest way to achieve this, with the minimum set of optical elements, is to defocus the beam, typically by changing the bending radius of the focusing mirrors. Nevertheless, to defocus the beam from sample has the problem that the beam profile is heavily modulated by striations caused by the surface error of the focusing optics. To our knowledge, a relationship between these modulations of the beam and the surface errors that originates them has not been properly established. In this work we show that beam modulation of a defocused beam has a nonlinear dependence on the slope profile of the mirror. From the derived relationships it follows that the relative contributions to beam striations of slope error lower and higher spatial frequencies vary depending on how far away the measurement plane is from the image plane. We explore the relationship between the amplitude of the striations and the power spectral density of the slope errors.

Date Published: 27 September 2013
PDF: 7 pages
Proc. SPIE 8848, Advances in X-Ray/EUV Optics and Components VIII, 884810 (27 September 2013); doi: 10.1117/12.2024528

Published in SPIE Proceedings Vol. 8848:
Advances in X-Ray/EUV Optics and Components VIII
Ali Khounsary; Shunji Goto; Christian Morawe, Editor(s)