Experimental Benchmarking and Stability Analysis of Double Shell Implosions on the National Ignition Facility

Double-shell ICF implosions are being performed on NIF as an alternative to the more widely investigated case of single-shell implosions. Double shells offer a complementary approach to achieving ignition in that they operate at lower convergence ratios and potentially ignite at lower temperatures. Due to the multiple interfaces, however, double shells can suffer from interfacial instability growth that will degrade performance. In this talk, we report results from integrated hohlraum simulations using the radiation-hydrodynamics code HYDRA [1]. The simulations are first compared with data from NIF double-shell experiments, which were performed to quantify both the high-energy (Au L-shell) preheat environment and the implosion trajectory and timing. The performance of these experimentally benchmarked simulations is then assessed, and this tuned implosion is used to quantify the degradation due to surface roughness on the multiple interfaces of a double shell. Both lower-resolution full-sphere and more highly resolved wedge capsule-only simulations are used to quantify the degradations due to interfacial instability. Mitigation strategies to reduce these degradations are discussed.



[1] M. M. Marinak, G. D. Kerbel, N. A. Gentile, O. Jones et al., Phys. Plasmas 8, 2275 (2001).