Rayleigh-Taylor Growth of Isolated Bubbles and Spikes in Laser-Driven Foils

Rayleigh-Taylor (RT) perturbation growth in laser fusion capsules can be triggered by isolated target non-uniformities, such as fill tubes, mounting stalks, tents, etc. Recently, the first experimental study of the perturbation evolution caused by isolated non-uniformities, straight grooves characteristic sizes of < 1 to 10s of $\mu \mathrm{m}$ machined on planar plastic targets, has been carried out on the Nike KrF laser at NRL. Initial target defects are relatively large-amplitude, inherently multi-mode, and grow into the strongly nonlinear regime. Face-on monochromatic x-ray radiography used to diagnose the areal-mass perturbation development indicated an early-time growth of the localized cavity in the target in depth and width, followed by its apparent closure. The initial “scar” on the target appears to be self-healing, making the accelerated foil more uniform instead of being cut through.