Tracking ultrafast dynamics of intense shock generation and breakout at target rear

We report upon the picosecond plasma dynamics at the rear surface of a thin aluminium foil (of either 5.5 um or 12 um thickness) excited by high contrast (picosecond intensity contrast of 10^10), 800 nm, femtosecond pulses at an intensity of 3 x 10^19 W/cm2. We employ ultrafast pump-probe reflectometry using a second harmonic probe (400 nm) interacting with the rear surface of the target. A rise in the probe reflectivity 30 picoseconds after the pump pulse interaction reveals the breakout of a shock wave at the target rear surface which reflects the 400 nm probe pulse. Simulations using the ZEPHYROS hybrid particle-in-cell code were performed to understand the heating of the target under the influence of the high intensity laser pulse, and the temperature profile was then passed to the radiation-hydrodynamics simulation code HYADES in order to model the shock wave propagation in the target. A good agreement was found between the calculations and experimental results.