High-mode Rayleigh-Taylor growth in NIF ignition capsules

• Published in: High energy density physics Vol. 6; no. 2; pp. 171 - 178
• Main Authors: Hammel, B.A., Haan, S.W., Clark, D.S., Edwards, M.J., Langer, S.H., Marinak, M.M., Patel, M.V., Salmonson, J.D., Scott, H.A.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-06-2010
• Subjects: Hydrodynamic simulation; Implosions; Inertial confinement fusion; Rayleigh-Taylor instabilities; Implosions; Inertial confinement fusion; Rayleigh-Taylor instabilities; Hydrodynamic simulation
• ISSN: 1574-1818; 1878-0563
• DOI: 10.1016/j.hedp.2009.12.005

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).