Beecroft Building, Department of Physics, University of Oxford, Parks Road, Oxford, OX1 3PU
Dr Patrick Heighway, University of Oxford
Abstract
Dynamic compression science concerns the behaviour of matter at the most extreme pressures and temperatures accessible on Earth. The singularly powerful combination of high-intensity-laser platforms coupled to ultrabright x-ray free-electron lasers (XFELs) now allows us to witness dramatic, microstructural dynamics precipitated by compression of solid matter to planetary pressures at strain rates approaching those of meteoric impacts. The ability to diagnose the extraordinary conditions accessible only via dynamic compression is essential to understanding the formation and structure of planetary bodies, building models of metals and ceramics under colossal stress for aerospace and defence, and discovering exotic phases of matter with unique mechanical and electrical properties.
Despite tremendous progress characterising the end result of extreme dynamic compression, our understanding of what takes place during rapid pressurisation is largely incomplete. In this seminar, I discuss recent work undertaken by our group to better understand the ultrafast dynamics unfolding in the wake of a strong compression wave, leveraging the unmatched diagnostic capability of the XFEL and sophisticated materials models spanning multiple length-scales. I will describe: diffraction-based measurements of catastrophic, stress-induced, homogeneous nucleation of crystal defects in shock-compressed tantalum; direct observation of concurrent, competing phase-transition mechanisms in zirconium; and our group’s recent demonstration of single-shot, thermal-diffuse-scattering-based temperature measurements of an elemental metal under shock compression.