Coupling a gas gun with an X-pinch x-ray source to perform x-ray diffraction under shock loading.

Abstract

X-ray diffraction is an appropriate technique to probe crystalline materials and better understand their response under shock loading, particularly when they experience phase transition. This technique was already used at various large-scale facilities. Here, we present an alternative way to perform x-ray diffraction under shock loading at the laboratory scale by coupling an X-pinch x-ray generator with a single stage gas gun. This x-ray source is capable of generating a single polychromatic x-ray flash shorter than 100 ns. Preliminary static diffraction tests gave promising results, and then, an experimental apparatus was set up to perform in situ x-ray diffraction in a shock-loaded material. X-ray diffraction is performed in reflection at the interface between the studied sample and an anvil window to ensure a homogeneous pressure state within the probed region. A specific target configuration was designed to synchronize the x-ray emission with the temporary shocked state. The synchronization is achieved by the use of a trigger chain whose adjustable delay is chosen prior to the experiment based on the expected travel time of the shock wave throughout the target. The technique was successfully used to investigate the solid-solid phase transition of tin between β and γ phases. Results indicate a satisfying synchronization between the shock wave arrival and the x-ray emission. Diffractograms under shock loading show a disappearance of the static ambient figure (parent phase) and the development of a new diffraction pattern (daughter phase).