Abstract
The Nike KrF laser facility was used to study the evolution of isolated defects with characteristic sizes of <1 to 10s of μm in laser-accelerated plastic foils. The experimental platform permitted, for the first time, the systematic study of localized perturbation growth, which is inherently multimode, through ablative Richtmyer-Meshkov and Rayleigh-Taylor stages and into the strongly nonlinear regime. Initial target defects were relatively large amplitude, but spatially localized, and emulated tent, fill-tube, and other nonuniformities that are present in inertial confinement fusion capsules. Face-on x-ray radiography indicated initial growth of the perturbation in both depth and width, followed by its apparent closure due to oblique spike growth. Hollow jetlike profiles of laterally expanding, rising, Rayleigh-Taylor bubbles were observed on the rear surface of the target from each isolated defect. Radiation hydrodynamic simulations provided insight into the mechanism of the closure and other features of the bubble and spike evolution specific to isolated defects.
Highlights
Accelerated inertial confinement fusion targets are subject to hydrodynamic instabilities, which lead to the growth of nonuniformities
Defect-induced mix experiments (DIME) on OMEGA [16,17] and NIF [18] measured and modeled the influence of localized defects on P2 asymmetry at stagnation and neutron yields which showed that modeling of the fine-scale interaction of the groove feature is a very challenging task [16,17,18]
There is extensive literature on strong-shock-driven flows affected by localized preshock nonuniformities and structures, including distortion of shock fronts and formation of jets [19,20]
Summary
Accelerated inertial confinement fusion targets are subject to hydrodynamic instabilities, which lead to the growth of nonuniformities. These studies do not directly address the growth of the bubbles and spikes, the lateral mass redistribution, or similar instability manifestations that start from small seeds and cause the target distortion and mix.
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