Single-exposure X-ray phase imaging microscopy with a grating interferometer.

Silja Flenner,Andreas Schropp,Stefan Funk,Mareike Weule,Gisela Anton,Veronika Ludwig,Maria Seifert,Bernhard Akstaller,Pascal Meyer,Andreas Wolf,Max Schuster,Silvia Cipiccia,Johannes Hagemann,Thilo Michel

doi:10.1107/s160057752200193x

Abstract

The advent of hard X-ray free-electron lasers enables nanoscopic X-ray imaging with sub-picosecond temporal resolution. X-ray grating interferometry offers a phase-sensitive full-field imaging technique where the phase retrieval can be carried out from a single exposure alone. Thus, the method is attractive for imaging applications at X-ray free-electron lasers where intrinsic pulse-to-pulse fluctuations pose a major challenge. In this work, the single-exposure phase imaging capabilities of grating interferometry are characterized by an implementation at the I13-1 beamline of Diamond Light Source (Oxfordshire, UK). For comparison purposes, propagation-based phase contrast imaging was also performed at the same instrument. The characterization is carried out in terms of the quantitativeness and the contrast-to-noise ratio of the phase reconstructions as well as via the achievable spatial resolution. By using a statistical image reconstruction scheme, previous limitations of grating interferometry regarding the spatial resolution can be mitigated as well as the experimental applicability of the technique.

Highlights

Single-exposure X-ray phase imaging microscopy with a grating interferometer was demonstrated in an experiment using synchrotron radiation
Previous implementations of grating-based X-ray microscopy were based on X-ray imaging microscopes, where the sample is placed in a conjugate plane upstream of the X-ray optics, and relied on the phase stepping approach and on the acquisition of multiple frames (Yashiro et al, 2009, 2010)
We could demonstrate a broader applicability of grating interferometry through a statistical image reconstruction method

Summary

Introduction

Owing to its penetration power and its small wavelengths, hard X-ray imaging is suited for nondestructive and quantitative probing of matter down to the nanometre scale, where it can give access to projective or volumetric structural information by two- or three-dimensional imaging, respectively. In the hard X-ray regime, the real part of the refractive index, which governs the phase shift due to the sample, can be orders of magnitude larger than the imaginary part, which sets the absorption (Fitzgerald, 2000) This is of special relevance for the study of materials with low atomic numbers Z as well as for micro- and nanoscopic imaging where specimens show little or no attenuation contrast (Withers, 2007). The referenced single-pulse experiments at synchrotron sources either employed simple X-ray radiography or propagation-based phase contrast imaging (PBPCI) (Snigirev et al, 1995; Cloetens et al, 1996, 1999). The latter approach has found first applications at XFELs (Schropp et al, 2015; Vagovicet al., 2019; Hagemann et al, 2021).

Experimental implementation at I13-1

Data acquisition and evaluation

Imaging microscope with OSA

Quantitative contrast

Imaging at different Talbot orders

Summary and outlook