Circular Unit Cell Gratings for X-ray Dark-Field Imaging

Matias Kagias,Pablo Villanueva-Perez,Konstantins Jefimovs,Zhentian Wang,Amogha Pandeshwar,Marco Stampanoni

doi:10.1088/1742-6596/849/1/012053

Abstract

Dark-field imaging has been demonstrated to provide complementary information about the unresolved microstructure of the investigated sample. The usual implementation of a grating interferometer, which can provide access to the dark-field signal, consists of linear gratings limiting the sensitivity to only one direction (perpendicular to the grating lines). Recently, a novel grating design, composed of circular unit cells, was proposed allowing 2D-omnidirectional dark-field sensitivity in a single shot. In this work we present a further optimisation of the proposed grating by changing the arrangement of the unit cells from a Cartesian to a hexagonal grid. We experimentally compare the two designs and demonstrate that the latter has an improved performance.

Highlights

Grating interferometry (GI) is a phase and scattering sensitive method capable of providing complementary information to standard absorption imaging of a sample [1, 2, 3]
In this work we present a further optimisation of the proposed grating by changing the arrangement of the unit cells from a Cartesian to a hexagonal grid
If the unit cells are arranged in a honeycomb manner (HPG) the packing ratio increases to √π ≈ 0.906 leading to a higher unit cell density in the final image

Summary

Introduction

Grating interferometry (GI) is a phase and scattering sensitive method capable of providing complementary information to standard absorption imaging of a sample [1, 2, 3]. The usual realisation of a grating interferometer is based on linear gratings Such a design allows differential phase and dark-field sensitivity in only the direction perpendicular to the grating lines. A method based on a single phase grating, capable of being sensitive to scattering in all the directions of the imaging plane has been proposed [14] This was achieved by utilising a phase grating that is composed by a mosaic repetition of circular gratings. A square packing of the unit cells is undoubtedly the most straightforward implementation of such a grating design since the layout of the unit cells defines the pixel matrix Such an implementation comes with a number of limitations. We fabricate such a grating and perform experimental comparison to demonstrate the improved performance of the design

Materials and methods

Results

Conclusion