Measurements of Rayleigh-Taylor Growth Rate of Planar Targets Irradiated Directly by Partially Coherent Light

We report the first measurements of laser-driven Rayleigh-Taylor instability at the linear growth regime in an imprint-free condition. Initially rippled polystyrene foils were irradiated by the partially coherent light. We measured temporal evolution of areal-density perturbation by the face-on x-ray backlighting technique. The observed maximum growth factor was nearly 50. We also measured the acceleration of the irradiated foil. The growth rate was approximately 50% of the classical growth rate. These experimental results were well reproduced by a two-dimensional simulation coupled with the Fokker-Planck treatment of electron heat transport. {copyright} {ital 1997} {ital The American Physical Society}