First proton-beam driven Rayleigh-Taylor experiments on KALIF

We have used a high-power pulsed proton beam (50 ns, 0.15-1 TW/cm(2), 1.7 MeV peak proton energy) of the Karlsruhe Light Ion Facility (KALIF) to ablatively accelerate 20-50 mu m thick planar targets provided with a 2D periodic structure to velocities of similar to 10 km/s. Line-imaging laser-Doppler velocimetry with high spatial(less than or equal to 10 mu m) and temporal ( greater than or equal to 200 ps) resolution is employed to measure the velocity of the rear surface of the targets provided with a small-scale corrugation. From the temporal evolution of the transverse velocity profiles we obtain the feed-through of the hydrodynamic instability developing at the boundary between the condensed part of the target and the ablation plasma. We find stable acceleration during the first wave reverberation cycle. After this an exponential growth is observed at an average rate that amounts to 40-65% of the classical value. The reduction is mainly due to heat transport driven mass convection through the boundary between the condensed part of the target and the ablated plasma. (C) 1998 Elsevier Science B.V. All rights reserved.