Hierarchical radioscopy using polychromatic and partially coherent hard synchrotron radiation.

Pushing synchrotron x-ray radiography to increasingly higher image-acquisition rates (currently up to 100,000 fps) while maintaining spatial resolutions in the micrometer range implies drastically reduced fields of view. As a consequence, either imaging a small subregion of the sample with high spatial resolution or only the complete specimen with moderate resolution is applicable. We introduce a concept to overcome this limitation by making use of a semi-transparent x-ray detector positioned close to the investigated sample. The hard x-rays that pass through the sample either create an image on the first detector or keep on propagating until they are captured by a second x-ray detector located further downstream. In this way, a process can be imaged simultaneously in a hierarchical manner within a single exposure and a projection of the complete object with moderate resolution as well as a subregion with high resolution are obtained. As a proof-of-concept experiment, image sequences of an evolving liquid-metal foam are shown, employing frame rates of 1000  images/s (1.2 μm pixel size) and 15,000  images/s (18.1 μm pixel size) for the first and second detector, respectively.