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"Double-loop" theory was determined by deriving a correlation between turbulent fluctuating kinetic energy and water vapor volume fraction from the momentum equation, which further logically revealed the mystery of cavitation breaking around a three-dimensional symmetry hydrofoil based on the numerical results of large eddy simulation and Zwart-Gerber-Belamri cavitation model. When the second-order fluctuation moment V'xV'x and the streamwise velocity Vx are depleted, a vortex is generated, leading to alternating cavitation interface fluctuations. In one state, cavitation naturally breaks outward from the inner zone, triggering an up-and-down fluctuation in the normal velocity in the gap vortex and transferring external energy to the inner zone. In another state, cavitation collapse caused by a reentrant jet stagnates the reverse Vx so that V'xV'x tends to zero. It triggers a rise in an upward normal velocity in the attached vortex, creating an exchange of energy through the wake. The pressure implosion resulting from the Shrinkage of the "Like-Rayleigh-Plesset" cavity at the cavitation onset is stronger than the pressure implosion created by the vortex field during cavitation breaking. [ABSTRACT FROM AUTHOR]

Abstract: 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). [Copyright &y& Elsevier]

Abstract: Low-z dopants such as argon are used to characterize the plasma properties in imploding inertial confinement fusion (ICF) capsules. Higher z dopants will be used as the temperature of the capsules is increased especially as we approach ignition on the National Ignition Facility (NIF). The presence of the higher z dopants also affects the dynamics of the implosion as it increases the electron density, which increases the radiation losses from the plasma allowing the plasma to compress to a smaller volume. In the present study, we examine the effects at higher dopant densities. While a normal glass capsule loses energy to radiation during compression, the high-z shells will confine the radiation even as equilibrium burn is approached. We have fielded thin 1-mm diameter glass shells filled with varying amounts of xenon and krypton gas to study the progression from non-equilibrium to equilibrium burn as the dopant gas concentration is increased. The shells used for these experiments also contained 3He to measure the proton spectrum from the D3He reaction providing information about the target temperature and the density-radius product, ρR. Here we present results using the X-ray measurements, as well as discuss some of the issues and the progress we made. [Copyright &y& Elsevier]