Strongly shocked cylindrically convergent implosions were conducted on the OMEGA laser. The directly driven targets consist of a low-density foam core and an embedded aluminum shell covered by an epoxy ablator. The outer surface of the aluminum shell has imposed single-mode perturbations with wave numbers k = 0.25, 0.7, 1.05, and 2.5 (rad/μm) and initial amplitudes η0 /λ = 0.04, 0.11, 0.33, and 0.4. In our convergent geometry, perturbation growth without evidence of saturation, for η/λ as large as 4.5 is observed for k < 1. For k > 1 growth rate scaling with wavenumber breaks down and transition to turbulence is suggested.

The system of differential equations for the non-ablated mass, the average implosion velocity, and the ablation radius of an indirectly driven capsule in acceleration phase, has been obtained from conservation principles of hydrodynamics. Two phases are distinguished during acceleration, according to the uniformity of the velocity in the non-ablated shell. The results of the integration of this system are well compared with numerical simulation of optimized capsules. Assuming that the ablation pressure depends only on the Hohlraum temperature, the relations between the non-ablated mass, the implosion velocity, and the ablation radius are obtained for optimized temperature shape. These relations provide the maximum implosion velocity and the remaining non-ablated mass in terms of the initial capsule and the maximum temperature (or the initial capsule mass in terms of the remaining non-ablated mass) useful to determine the required ablator thickness for optimized capsules. These results are also compared with numerical simulations of different capsules.