Large-scale high-resolution simulations of high gain direct-drive inertial confinement fusion targets

Abstract

Targets have been designed that produce moderate to high gain when directly driven by lasers. The intrinsic sensitivity of these targets to hydro instabilities is found using the FAST(2D) multidimensional radiation hydrocode [J. H. Gardner, A. J. Schmitt, J. P. Dahlburg et al., Phys. Plasmas 5, 1935 (1998)], which simulates the simultaneous behavior of a large bandwidth (e.g., l=2–256) of perturbations from compression to acceleration, and then to stagnation and burn. The development of the structure in these multimode simulations is benchmarked to theoretical analysis and single-mode calculations, which reveals the need to “renormalize” the simulation after compression. The simulations predict that a direct drive point design is expected to degrade significantly from its one-dimensional clean yield, yet still ignite and give appreciable gain. Simulations of high-gain pellets using a spike prepulse to inhibit Richtmyer–Meshkov growth show a considerable robustness, with high (>100) gains possible even with nominal surface finishes and laser imprint.