Precise wavefront characterization of X-ray optical elements using a laboratory source

TL;DR

This paper introduces a laboratory setup using a commercial X-ray source and ptychographic X-ray speckle tracking to precisely characterize X-ray optical elements, matching synchrotron-level accuracy and enabling routine lab-based measurements.

Contribution

The authors develop and validate a lab-based X-ray wavefront characterization method that achieves high precision comparable to synchrotrons, facilitating faster and more accessible optical performance assessments.

Findings

Lab setup accurately measures wavefront distortions.

Results comparable to synchrotron measurements.

Successful phase error correction of a multilayer Laue lens.

Abstract

Improvements in X-ray optics critically depend on the measurement of their optical performance. The knowledge of wavefront aberrations, for example, can be used to improve the fabrication of optical elements or to design phase correctors to compensate for these errors. Nowadays, the characterization of such optics is made using intense X-ray sources such as synchrotrons. However, the limited access to these facilities can substantially slow down the development process. Improvements in the brightness of lab-based X-ray micro-sources in combination with the development of new metrology methods, and in particular ptychographic X-ray speckle tracking, enable characterization of X-ray optics in the lab with a precision and sensitivity not possible before. Here, we present a laboratory set-up that utilizes a commercially available X-ray source and can be used to characterize different types of X-ray optics. The set-up is used in our laboratory on a routine basis to characterize multilayer Laue lenses of high numerical aperture and other optical elements. This typically includes measurements of the wavefront distortions, optimum operating photon energy and focal length of the lens. To check the sensitivity and accuracy of this laboratory set-up we compared the results to those obtained at the synchrotron and saw no significant difference. To illustrate the feedback of measurements on performance, we demonstrated the correction of the phase errors of a particular multilayer Laue lens using a 3D printed compound refractive phase plate.