Deceleration phase Rayleigh-Taylor instability growth of engineered perturbations in cylindrical implosions*

Deceleration stage Rayleigh-Taylor instability (RTI) is believed to be a significant cause of yield degradation in current inertial confinement fusion implosions, but experimental measurements of RTI growth in convergent geometry are lacking. Recently, we have revived a cylindrical implosion platform at the Omega laser facility to measure deceleration phase RTI growth. Perturbations are engineered on the inner surface of a 500 um long aluminum marker layer that is embedded within a plastic ablator. The targets are filled with CH foam at a density of 60 mg/cc and 300 mg/cc, allowing control of convergence from 2.5 – 6.0.  Using x-ray radiography, we have measured the growth of single-mode (mode 10 or mode 20) and two-mode (mode 10 and 20) sine-wave perturbations with initial amplitudes between 2-4 microns. Measurements show growth factors up to ~15. The measurements are compared to simulations of the experiments using the LANL rad-hydro code xRAGE with a laser package. The measurements are consistent with the simulation results.  The measurements will also be compared to both the Epstein linear model and the nonlinear Buoyancy-Drag model.