SIMULATION OF THE RAYLEIGH-TAYLOR INSTABILITY IN COLLIDING, ABLATIVELY DRIVEN LASER FOILS

This paper reports results from a series of numerical simulations of a pair of independently accelerated rectilinear foils in the presence of the ablative Rayleigh-Taylor (RT) instability on the laser-side surfaces. The foil thickness and laser intensity are chosen to be in the range relevant to high-gain inertial fusion pellets, with 80-mu-m thick plastic (CH) foils accelerated toward each other from a separation distance of 650-mu-m by a 1/4-mu-m laser beam with an intensity of 3 X 10(14) W/cm2. At early times the foils are physically well separated from one another, and evolve independently in a way that is fully consistent with the previously studied evolution of ablatively RT unstable planar targets [Gardner et al., Phys. Fluids B 3, 1070 (1991)]. Subsequently, pressure builds up in the region between the foils, causing them to decelerate. This stabilizes the RT growth on the laser sides, while driving the RT instability on the inner sides. For thin foils, laser-side RT bubbles become rapidly growing inner surface RT spikes which mix and coalesce as the foils are pressed together.