Shock-timing experiments in polystyrene target

Direct-drive and indirect-drive inertial confinement fusion (ICF) targets use temporally shaped drive pulses to optimize target performance. The timing of multiple shock waves is crucial to the performance of ICF ignition targets. Velocity interferometer system for any refiector (VISAR) is the principal diagnostic tool for shock-timing experiments. We present velocity measurements from the shock waves in polystyrene targets driven by two 200-ps pulses separated by 1-2 ns. These pulses drive two shock waves that coalescence in the target. Coalescence time and transit times are observed by VISAR.