In-situ X-ray diffraction under shock loading: cristallographic study of Tin polymorphic transitions.

The purpose of this study is to collect experimental information about material undergoing phase transition under shock loading in order to improve current models and numerical simulations. However the comprehension of the mechanisms involved remains a great issue. Past studies have shown that macroscopic measurements on shocked materials do not provide enough information to fully understand the mechanism involved.

X-ray diffraction is a complementary technique to investigate the microstructure on shocked single crystals or polycrystalline materials. The continuous improvement of X-ray generation techniques has provided X-ray sources capable of generating intense short pulses to perform X-ray diffraction under shock loading. X-ray diffraction experiments were carried out two facilities to investigate the beta-gamma transition in Tin: At CEA Gramat using an X-Pinch generator and at the Advanced Photon Source at Argonne using a synchrotron beam. Shocks were generated by plate impact experiments on gas gun.

Similar diffraction patterns are obtained from single crystals below and above the transition to study the evolution of the cristallographic structure of Tin under shock loading with a specific configuration of Xray diffraction in reflexion geometry. A specific tool was designed and developped to analyse and simulate diffraction patterns. On this new experimental basis, some hypothesis could be proposed regarding the material dynamic behavior.