Direct imaging of shock wave splitting in diamond at Mbar pressure

Understanding the behavior of matter at extreme pressures of the order of a megabar(Mbar) is essential to gain insight into various physica phenomena at macroscales—the formation of planets,young stars,and the cores of super-Earths,and at microscales—damage to cerami materials and high-pressure plastic transformation and phase transitions in solids.Under dynamic compression of solids up to Mbar pres sures,even a solid with high strength exhibits plastic properties,causing the induced shock wave to split in two:an elastic precursor and plastic shock wave.This phenomenon is described by theoretical models based on indirect measurements of material response.The adven of x-ray free-electron lasers(XFELs) has made it possible to use their ultrashort pulses for direct observations of the propagation of shoc waves in solid materials by the method of phase-contrast radiography.However,there is still a lack of comprehensive data for verificatio of theoretical models of different solids.Here,we present the results of an experiment in which the evolution of the coupled elastic-plasti wave structure in diamond was directly observed and studied with submicrometer spatial resolution,using the unique capabilities of the x-ra free-electron laser(XFEL).The direct measurements allowed,for the first time,the fitting and validation of the 2D failure model for diamon in the range of several Mbar.Our experimental approach opens new possibilities for the direct verification and construction of equations c state of matter in the ultra-high-stress range,which are relevant to solving a variety of problems in high-energy-density physics.