Abstract
Bragg coherent diffraction imaging (BCDI) is a powerful X-ray imaging technique for crystalline materials, providing high resolution maps of structure and strain. The technique is typically used to study a small isolated object, and is in general not compatible with a bulk polycrystalline sample, due to overlap of diffraction signals from various crystalline elements. In this paper, we present an imaging method for bulk samples, based on the use of a coherent source. The diffracted X-ray beam from a grain or domain of choice is magnified by an objective before being monitored by a 2D detector in the far field. The reconstruction principle is similar to the case of BCDI, while taking the magnification and pupil function into account. The concept is demonstrated using numerical simulations and reconstructions. We find that by using an object-lens distance shorter than the focal length, the numerical aperture is larger than in a traditional imaging geometry, and at the same time the setup is insensitive to small phase errors by lens imperfections. According to our simulations, we expect to be able to achieve a spatial resolution smaller than 20 nm when using the objective lens in this configuration.
Highlights
Coherent X-ray diffraction imaging, CDI, is a microscopy method aiming at producing a highly resolved quantitative image of a sample illuminated by a coherent plane wave without the need of an objective [1,2]
We present an imaging method for bulk samples, based on the use of a coherent source
The diffracted X-ray beam from a grain or domain of choice is magnified by an objective before being monitored by a 2D detector in the far field
Summary
Coherent X-ray diffraction imaging, CDI, is a microscopy method aiming at producing a highly resolved quantitative image of a sample illuminated by a coherent plane wave without the need of an objective [1,2]. CDI approaches are relevant for crystalline imaging, as recently illustrated by the in-operando monitoring of the motion of a dislocation [6] and the propagation of a shockwave [7] Those specific crystalline imaging methods, referred to as Bragg coherent diffraction imaging (BCDI), exploit the oversampled intensity patterns measured in the vicinity of a Bragg peak produced by a finite-sized crystal under hard X-ray illumination [8]. In this configuration, the full 3D intensity pattern is derived from 2D patterns acquired at equidistant angular positions during a scan where the sample is tilted around an axis perpendicular to the incoming beam. A last section comprises a discussion of the limitations and further opportunities for this technique
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