Observation of Laser Ablation in Al Using Ultrafast X-Ray Diffraction*

The mechanisms of laser matter interactions with an ablator such as Al, are fundamental to understanding how strong shock waves are driven into materials as a function of laser energy and pulse duration. Using 130 fs x-rays at the LCLS Materials at Extreme Conditions (MEC) beamline, we interrogated the initial ablation of Al driven by 120 ps pulses and observed the strength of the shock induced and the amount of material which was ablated. The samples consisted of 2 microns of Al deposited on 2 microns of Zr, which for this study served as a calibrant. The Al samples were dynamically compressed to pressures up to 100 GPa, driven with energies in the range of 2.5-250 mJ. The experimental observations were compared to laser matter interaction simulations using two different hydrodynamic codes: DRACO and FLASH. These codes were chosen to compare the impact of laser absorption physics included in the simulation on the predicted ablation depths.