THE ROLE OF THE RAYLEIGH-TAYLOR INSTABILITY IN LASER-DRIVEN BURNTHROUGH EXPERIMENTS

Experiments were conducted to confirm that the Rayleigh-Taylor instability is the main process controlling the burnthrough time in imploding spherical experiments. In these experiments the laser irradiates targets overcoated with a parylene layer, in which one or more thin signature layers of moderate- to high-Z material are embedded to signal the penetration of the heat front. Target parameters were varied to study the effect on the burnthrough time of changes to target acceleration, Atwood number, and ablation velocity. The effects of improved laser uniformity through the introduction of smoothing by spectral dispersion are also presented. The results agree well with those obtained from a multimode mix model. This suggests that burnthrough experiments can be used to measure improvements in laser-irradiation or target-fabrication uniformity and to test methods to mitigate the growth of the Rayleigh-Taylor instability.