Ballistic properties of debris produced by laser shock-induced micro-spallation of tin samples

International audienceDynamic fragmentation in the liquid state after melting under shock compressionor upon release leads to the ejection of a cloud of droplets. This phenomenon, called microspallation,remains essentially unexplored in most metals. We present laser shock experimentsperformed on tin, to pressures ranging from about 60 to 220 GPa. Experimental diagnosticsinclude skew Photonic Doppler Velocimetry (PDV) measurements of the droplets velocities,transverse observations of the expanding cloud of droplets, and soft recovery of ejecta withina low density gel. Optical microscopy of the gel reveals the presence of droplets whichconfirm shock-induced melting prior to fragmentation. To quantify size distribution of thedebris, 3D X-ray micro-tomography has been performed at the ESRF synchrotron facility inFrance (similar to US Advanced Photon Source), where sub-micrometer resolution could beachieved. In this paper, the resulting velocity and size distributions are presented andcompared with theoretical predictions based on a one-dimensional description accounting forlaser shock loading, wave propagation, phase transformations, and fragmentation.Discrepancies between measured and calculated distributions are discussed. Finally,combining size and velocity data provides estimates of the ballistic properties of debris andtheir kinetic energy, which are key issues for anticipating the damage produced by theirimpacts on nearby equipments