Incoherent Diffraction Imaging with hard X-rays: Single-shot characterization of 2D spatial coherence of a focused X-ray beam

Achieving a compact and accessible way of performing nanoscale imaging would represent a ground-breaking step in this field. This vision is the main goal of the NanoXCAN project, which aims to develop an X-ray microscope capable of operating outside the strict coherence and infrastructure requirements of conventional X-ray imaging.

A promising approach to achieve this is Incoherent Diffraction Imaging (IDI), a recently proposed technique that exploits the partial coherence of typically considered incoherent sources. To assess its feasibility in the hard X-ray regime, we conducted an experimental campaign at the Nanoscopium beamline, SOLEIL. Using custom diffusers, speckle patterns were successfully generated and characterized. Speckles suitable for IDI were produced sufficiently out of focus, where the plane-wave approximation is valid, and for small source sizes.

Under these conditions, fully developed speckle patterns were obtained, validating the diffuser design for this setup. Moreover, we performed a single-shot characterization of the 2D spatial coherence using these custom diffusers’ far-field speckle pattern. This coherence analysis provided single-shot qualitative and quantitative measurements of the transverse coherence length and global degree of coherence, confirming the expected inverse dependence of coherence on source size.

Under optimal conditions, the measured coherence length reached ∼ 1 μm. These results establish the experimental groundwork for future IDI demonstrations with hard X-rays and advance the NanoXCAN goal of enabling high-resolution lensless imaging beyond large-scale facilities.