High-mode Rayleigh-Taylor growth in NIF ignition capsules

An assessment of short wavelength hydrodynamic stability is an essential component in the optimization of NIF ignition target designs. Using highly-resolved massively-parallel 2D Hydra simulations [Marinak, M.M. et al., Physics of Plasmas (1998). 5(4): 1125], we routinely evaluate target designs up to mode numbers of 2000 (λ∼2 μm) [Hammel, B.A. et al., Journal of Physics: Conference Series, 2008. 112(2): p. 02200]. On the outer ablator surface, mode numbers up to ∼300 (λ∼20 μm) can have significant growth in CH capsule designs. At the internal fuel:ablator interface mode numbers up to ∼2000 are important for both CH and Be designs. In addition, “isolated features” on the capsule, such as the “fill-tube” (∼5 μm scale-length) and defects, can seed short wavelength growth at the ablation front and the fuel:ablator interface, leading to the injection of ∼10's ng of ablator material into the central hot-spot. We are developing methods to measure high-mode mix on NIF implosion experiments. X-ray spectroscopic methods are appealing since mix into the hot-spot will result in x-ray emission from the high-Z dopant (Cu or Ge) in the ablator material (Be or CH).