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X-ray Bragg ptychography

Principal investigator: Virginie Chamard

Imaging crystalline properties at the nano-scale

In the x-ray range, focusing components have very limited performances. Therefore, solving the inverse problem is a relevant strategy, which allows (i) to reach high spatial resolution in spite of limited apertures, (ii) to obtain quantitative information of the object (related to physical properties such as density, strain, crystal coherence, etc.).

Our efforts focus on Bragg ptychography, a synchrotron based coherent diffraction imaging method we have recently established. Bragg ptychography, which is compatible with a vast variety of nanostructured materials, opens access to the 3D high-resolution image of the crystalline properties.

The on-going implementations of Bragg ptychography at several synchrotron beamline (ESRF, Soleil, APS, MaxIV, etc…) ensure exciting perspectives for material nano-science.

From theoretical developments to experimental implementations

The specificities of Bragg ptychography require dedicated theoretical efforts, aiming at covering the questions raised by the Bragg geometry, the three-dimensionality of the problem, the choice of the inversion algorithm strategy and the image quality with respect to noise level.

The development of new inversion schemes leverages the retrieval of 3D information from a data set acquired at a single viewing angle, accelerating and simplifying the acquisition procedure.

Our 3D Bragg ptychography code, designed to perform experimental planning and data inversion, is used by many of our collaborators worldwide.

Experimental validations on test objects

The Bragg ptychography imaging method is thoroughly tested on specifically designed crystalline objects, to highlight potential limits, optimize the method and provide alternative reconstruction strategies. These studies ensure regular and robust progresses in method developments and relevant applications for physical or biological complex crystalline problems.