The development of shock pressure in direct laser ablation of Au

This work presents high-intensity laser direct ablation experiments on Au foil samples of 10-40 μm thickness, during which the average shock and free surface velocities were measured using a modified PDV diagnostic [1]. For laser intensities of 4x10¹² - 10¹⁴ W/cm², the shock pressure was estimated to be at 2.2 – 10.3 Mbar, respectively. A clear measurement of the free surface velocity for up to about 2 ns from shock breakout, combined with the average shock velocity measurement, shows that for short times after the beginning of the ablation process, the pressure wave propagates with a velocity much higher than the roughly steady shockwave pressure that stabilizes at later times. This effect manifests as large deviations from the material’s u_s-u_p EOS for thin targets in such irradiation setup.