First observation of density profile in directly laser-driven polystyrene targets for ablative Rayleigh–Taylor instability research

The temporal evolution of the density profile of a directly laser-driven polystyrene target was observed for the first time using an x-ray penumbral imaging technique coupled with side-on x-ray backlighting at the GEKKO XII [C. Yamanaka et al., IEEE J. Quantum Electron. QE-17, 1639 (1981)]–High Intensity Plasma Experimental Research laser facility (IL=0.7×1014 W/cm2, λL=0.35 μm). This density measurement makes it possible to experimentally confirm all physical parameters [γ(k),k,g,ṁ,ρa,Lm] appearing in the modified Takabe formula for the growth rate of the ablative Rayleigh–Taylor instability. The measured density profiles were well reproduced by a one-dimensional hydrodynamic simulation code. The density measurement contributes toward fully understanding the ablative Rayleigh–Taylor instability.