Mechanisms of Laser Driven Shocks in Tamped Materials

Understanding the enhanced pressure generated in laser driven tamped targets has been a long standing problem. In this work we have used the Janus Laser at LLNL to collect data on over 130 targets to investigate the laser induced pressure in Al and Ti targets, while varying parameters such as drive intensity from 10⁹ – 10¹¹ W/cm² , drive duration from 0.5 – 20 nanoseconds, laser wavelength from 1.053 (IR) – 0.526 (green) microns, and drive side tamper materials including sapphire, LiF, and fused silica. In particular these experiments obtained velocimetry (line VISAR) to determine the induced pressure and also obtained side-view images of the ablation plume thermal emission and density using streaked optical pyrometry and interferometry, respectively.  This suite of diagnostics allowed us to compare the laser ablated plume for bare vs tamped samples under these varied conditions, and correlate the tamper optical response to the pressure generated at the ablator for different drive-side tampers.