Measurements of laser driven spallation in tin and zinc using an optical recording velocity interferometer system

Measurements of the dynamic strength, in tin and zinc, shocked by a high power pulsed laser to tens of kilobars pressures are reported. The strain rates in these experiments are of the order of 10⁷ s^-1, higher by two-to-three orders of magnitude than those reached with conventional shock generators like plane impacts or explosives. The free surface velocity time history, which is related to the spallation process, was measured with an optical recording velocity interferometer system. This diagnostic technique is noninterfering and provides a highly accurate continuous measurement in time. The spall strength estimated from the free surface velocity profile was compared with the theoretical upper limit for the spall strength, calculated from a wide range equation of state for metals.