Characterisation of fast transient phenomena using X-ray phase contrast imaging

The aim of this post-doctorate is to develop a measurement chain dedicated to the observation and characterisation of Rapid Transient Phenomena (RTP) using X-ray phase contrast imaging (XPCI). The challenge is to provide a measurement system that can be deployed in the laboratory on a wide range of experiments that cannot be moved to the synchrotron. The performance targets are justified by the problems associated with additive manufacturing, the propagation of shock waves in low-density polymers, and the diagnosis of carbon composite materials impacted by an electric arc. For objects with low absorption, such as low-density polymers, liquids or plasmas, conventional X-ray imaging, which provides contrast due to the absorption cross-sections variations, is insufficient. To complete absorption, it is possible to exploit the phase of X-rays, which provides better detection of inhomogeneities and interfaces. The method used here to measure the phase is the multilateral shearing interferometry (IDML). It uses a single two-dimensional checkerboard phase grating that generates a reference interference pattern on the detector. The introduction ofan object between the grating and the detector modifies the reference interference pattern, which is then analysed by Fourier transform to reconstruct the phase image. By requiring only a single phase grid and exhibiting minimal X-ray flux loss, this method has favourable intrinsic characteristics in terms of sensitivity, robustness, ease of alignment and versatility, for application to dynamic imaging.