BURN-THROUGH OF THIN ALUMINUM FOILS BY LASER-DRIVEN ABLATION

Aluminum foils 1-75 μm thick were irradiated by 500-psec Nd-glass laser pulses with intensities 6×1012 to 1014 W/cm 2. The reflected and transmitted light and the produced x rays were measured using PIN photodiodes and crystal spectrometers. Two torsion pendula were used to measure the target and the plasma momenta. Both measurements are consistent with a simple hydrodynamic model. We obtain plasma pressures in the range 1.5-13 Mbars, shock-wave velocities between 0.9×106 and 2.6×106 cm/sec, penetration depths of the ablation surface in the domain of 3-10 μm for laser intensities in the range 6×10 12 to 1014 W/cm2. The burn-through times (i.e., the times that a hole is opened in the foil) for foils 25, 50, and 75 μm thick are measured to be 8±5, 18±5, and 25±5 nsec, respectively.