Reconstruction of an astigmatic hard X-ray beam and alignment of K-B mirrors from ptychographic coherent diffraction data

Abstract

We have used coherent X-ray diffraction experiments to characterize both the 1-D and 2-D foci produced by nanofocusing Kirkpatrick-Baez (K-B) mirrors, and we find agreement. Algorithms related to ptychography were used to obtain a 3-D reconstruction of a focused hard X-ray beam waist, using data measured when the mirrors were not optimally aligned. Considerable astigmatism was evident in the reconstructed complex wavefield. Comparing the reconstructed wavefield for a single mirror with a geometrical projection of the wavefront errors expected from optical metrology data allowed us to diagnose a 40 μrad misalignment in the incident angle of the first mirror, which had occurred during the experiment. Good agreement between the reconstructed wavefront obtained from the X-ray data and off-line metrology data obtained with visible light demonstrates the usefulness of the technique as a metrology and alignment tool for nanofocusing X-ray optics.

High-resolution three-dimensional partially coherent diffraction imaging

“…The ability to perform these measurements at partially coherent sources (including lab-based X-ray 21 ) or to utilize more flux to reduce the lengthy data acquisition times will be of huge benefit to materials and biological sciences. In addition, the ability to recover the coherence properties of an illuminating beam will find widespread use in characterising optical components 22 for synchrotron or XFEL sources.…”

X-ray metrology and performance of a 45-cm long x-ray deformable mirror

“…10,11 A second option to characterize optics is ptychography. 25,26 We will use a target of known structure and estimate the unknown electric field in our system, and hence the shape of the XDM. Ptychography will require more measurements and more computation than grating interferometry.…”

Coherent X-ray diffractive imaging on the single-cell-level of microbial samples

“…More recent ptychographic studies investigate the maximum derivable information from ptychographic data under non-simple experimental conditions for the illuminating wave-eld or the object such as position uncertainties [20,110,182], partial coherence and multiple wavelenghts [15,44,78,299], multiple object planes [181,284] and undersampling of the recorded di racted intensities [71]. In the rst place, however, the probably most important result has been the understanding that the ptychographic method not only is able to solve for the encoded object information but also for the illuminating wave-eld [183,294,296] making ptychography a valuable tool for analysing the wave-elds of X-rays [134,144,159,160,265,268]. In principle, the decoupling of object and illuminating wave-eld makes the retrieved object information free of aberrations.…”