A Shack-Hartmann Sensor for Single-Shot Multi-Contrast Imaging with Hard X-rays

Tomy Dos Santos Rolo,Danays Kunka,Stefan Reich,Sergey Gasilov,Tilo Baumbach,Edwin Fohtung,Anton Plech,Dmitry Karpov

doi:10.3390/app8050737

Abstract

An array of compound refractive X-ray lenses (CRL) with 20 × 20 lenslets, a focal distance of 20cm and a visibility of 0.93 is presented. It can be used as a Shack-Hartmann sensor for hard X-rays (SHARX) for wavefront sensing and permits for true single-shot multi-contrast imaging the dynamics of materials with a spatial resolution in the micrometer range, sensitivity on nanosized structures and temporal resolution on the microsecond scale. The object’s absorption and its induced wavefront shift can be assessed simultaneously together with information from diffraction channels. In contrast to the established Hartmann sensors the SHARX has an increased flux efficiency through focusing of the beam rather than blocking parts of it. We investigated the spatiotemporal behavior of a cavitation bubble induced by laser pulses. Furthermore, we validated the SHARX by measuring refraction angles of a single diamond CRL, where we obtained an angular resolution better than 4 μ rad.

Highlights

The broad availability of X-ray sources such as synchrotrons and free electron lasers with very high brightness paved the way to tackle the formidable demands of imaging the structural evolution of hierarchical materials by means of multi-contrast imaging
Phase-contrast imaging modalities assess the relative variations in the real part of the refractive index
We show the application of the analogue of a Shack-Hartmann sensor in the hard X-ray spectral range (SHARX), which permits for single-shot imaging of absorption, phase and diffraction contrast

Summary

Introduction

The broad availability of X-ray sources such as synchrotrons and free electron lasers with very high brightness paved the way to tackle the formidable demands of imaging the structural evolution of hierarchical materials by means of multi-contrast imaging. Phase-contrast imaging modalities assess the relative variations in the real part of the refractive index (propagation-based phase-contrast [1,2,3], crystal-based [4], edge illumination method [5], and grating-based interferometry [6,7,8,9,10]). Grating-based interferometry and diffraction-enhanced imaging can provide scattering contrast, thereby extending the accessible information to the full set of scalar wave-matter interactions in transmission geometry [11]. The requirement to record several sub-images interrupted by mechanical motion Sci. 2018, 8, 737 or different angles of the analyzer crystal) complicate the investigation of dynamics on the microsecond scale [12]. Successful approaches have used a canted interferometer setup to retrieve the phase shifts by Fourier analysis of the Moiré pattern [9] and could use polychromatic X-rays [13]

Methods

Results

Conclusion