Three-dimensional simulations of Nova high growth factor capsule implosion experiments

Abstract

Capsule implosion experiments carried out on the Nova laser [E. M. Campbell et al., Rev. Sci. Instrum. 57, 2101 (1986)] are simulated with the three-dimensional HYDRA radiation hydrodynamics code [NTIS Document No. DE-96004569 (M. M. Marinak et al. in UCRL-LR-105821-95-3)]. Simulations of ordered, near single mode perturbations indicate that structures which evolve into round spikes can penetrate farthest into the hot spot. Bubble-shaped perturbations can burn through the capsule shell fastest, in which case they cause even more damage. A simulation of a capsule with a multimode perturbation of moderate amplitude shows spike amplitudes evolving in good agreement with a saturation model during the deceleration phase. The presence of sizable low mode asymmetry, caused either by drive asymmetry or perturbations in the capsule shell, can dramatically affect the manner in which spikes approach the center of the hot spot. Three-dimensional coupling between the low mode shell perturbations intrinsic to Nova capsules and the drive asymmetry is found to be important, bringing the simulated neutron yields into closer agreement with the experimental values.

Simulations of X-ray emission from Omega fill tube experiments

“…Earlier studies of the growth rates of single perturbation modes have shown that the modes l•40 are responsible for most of the amplitude of the distortions in the interface [12]. The surface roughness and the bump on the capsule both are made up from many l-modes.…”

The first experiments on the national ignition facility

“…The goals of the hydrodynamics experiments were firstly to exercise x-ray backlighting capabilities on NIF, and secondly, to extend the study of hydrodynamic jets [41,42] to 3D and multjjet geometries for validating new 3D codes [43]. Figure 13 shows the experimental set-up.…”

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“…Three dimensional radiation hydrodynamic simulations and experiments (Marinak 1996) show that for smooth capsules the neutron yield of high growth factors implosion on Nova should be the measured 30% of the calculated 1D yield for C, -12. The Omega laser has the capability of using 40 of its 60 beams into a hohlraum producing better symmetry than Nova (Decker et al 1998).…”