Equation of state measurements using single Fabry-Perot velocimeter

Abstract

Accurate measurement of projectile and free surface velocity of target is a crucial part of any high pressure physics experiments involving hyper velocity impact. Fabry Perot velocimeter (FPV) is a widely accepted technique for single surface velocity measurements. In the present work a possibility of using single FPV for two surface velocity measurements is experimentally explored. The laser light is launched in such a way that it illuminates both the surfaces under study and reflected light coming from the flyer as well as from the target is used to generate interference fringes. Therefore by recording fringe displacements due to Doppler shift in reflected light corresponding to movement of both the surfaces at different time instants, velocity profile of both target and projectile can be computed. This technique has been utilized for equation of state measurements of polyurethane based retro-reflective tape at 12 GPa and aluminum at 15 GPa. Measured peak particle velocities at the target-glass interface have been found in good agreement with the reported equation of state data.