Dark-field X-ray ptychography

The dynamic range of X-ray detectors is a key factor limiting both the spatial resolution and sensitivity of X-ray ptychography as well as the coherent flux of incident X-rays. Here, we propose a method for high-resolution and high-sensitivity X-ray ptychography named "dark-field X-ray ptychography", which compresses the dynamic range of intensities of diffraction patterns. In this method, a small reference object is aligned upstream of the sample. The scattered X-rays from the object work as a reference beam for in-line holography. Ptychographic diffraction patterns including the in-line hologram are collected, and then the image of the sample is reconstructed by an iterative phasing method. This method allows us to obscure the low-Q region of the diffraction patterns using a beamstop since the in-line hologram complements structural information in the low-Q region, resulting in the compression of the dynamic range of intensities of diffraction patterns. A numerical study shows that the dynamic range of intensities of diffraction patterns is decreased by about three orders of magnitude.