Wavefront metrology measurements at SACLA by means of X-ray grating interferometry.

Yves Kayser,Simon Rutishauser,Makina Yabashi,Uwe Flechsig,Takashi Kameshima,Christian David,Haruhiko Ohashi,Tetsuo Katayama

doi:10.1364/oe.22.009004

Abstract

The knowledge of the X-ray wavefront is of importance for many experiments at synchrotron sources and hard X-ray free-electron lasers. We will report on metrology measurements performed at the SACLA X-ray Free Electron Laser by means of grating interferometry which allows for an at-wavelength, in-situ, and single-shot characterization of the X-ray wavefront. At SACLA the grating interferometry technique was used for the study of the X-ray optics installed upstream of the end station, two off-set mirror systems and a double crystal monochromator. The excellent quality of the optical components was confirmed by the experimental results. Consequently grating interferometry presents the ability to support further technical progresses in X-ray mirror manufacturing and mounting.

Highlights

Hard X-ray free electron lasers (XFELs), like the Linac Coherent Light Source (LCLS) [1], SPring-8 Angstrom Compact free electron Laser (SACLA) [2] and other upcoming facilities, provide X-ray radiation with an unprecedented brightness, spatial coherence and pulse duration
The grating rotation scan yielded a radius of curvature (ROC) in the horizontal direction of 153.2±0.6 m and 155.1±0.6 m, respectively
Grating interferometry, which measures the phase gradient of the incident wavefront, was employed for in-situ, at-wavelength measurements at the SACLA hard XFEL and allowed for a spatially resolved study of the X-ray wavefront

Summary

Introduction

Hard X-ray free electron lasers (XFELs), like the Linac Coherent Light Source (LCLS) [1], SPring-8 Angstrom Compact free electron Laser (SACLA) [2] and other upcoming facilities, provide X-ray radiation with an unprecedented brightness, spatial coherence and pulse duration. Because of its sensitivity regarding the local wavefront propagation direction X-ray grating interferometry was applied at synchrotron facilities for the metrology of X-ray optics, e.g., for the characterization of a multilayer mirror [13], the comparison of the coherence and wavefront properties of beam line optics [14, 15], the analysis of the wavefront distortions induced by a Be lens [16] or the investigation of the surface deformation of a double crystal monochromator under different heat loads [17]. The presented measurements were realized in the moiremode which enabled us to profit from the single-shot capabilities of the grating interferometer in the investigation of the X-ray wavefront

Experimental

Data analysis

Results

Conclusion