Three-dimensional multimode simulations of the ablative Rayleigh–Taylor instability

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Abstract
Multimode simulations of the evolution of the laser‐driven, ablative Rayleigh–Taylor instability on planar, plastic targets are performed in three dimensions, with FAST3D–CM. The initial mass density target perturbations are random, with a power law dependence of k −2, a RMS surface finish of 0.1 μm, and perturbation wave numbers ranging from 2π/d max to √2×(12π/d max), for d max=128 μm. At early nonlinear times, the perturbations grow to tile the target with approximately hexagonal bubbles that are of the shortest, initially seeded wavelengths not stabilized by density gradients. This tiling occurs on a time scale that is comparable to the eddy turnover time of the dominant bubble wavelength. When the target thickness is large compared to the dominant, short wavelengths, the bubbles continue to burn into the target and to evolve to progressively longer spatial scales. Predictions from second‐order mode coupling and saturation models are found to be consistent with the simulation results.