Measurement of ablative Richtmyer-Meshkov evolution from laser imprint

Abstract

Experiments were performed to investigate the ablative Richtmyer-Meshkov (RM) instability in plastic (CH2) foils. The two-dimensional (2-D) perturbations were created by laser imprinting using a special phase plate with a 2-D single mode, ∼70 μm wavelength sinusoidal intensity pattern on the plastic foil. The growth of imprinted perturbations was measured by face-on, X-ray radiography using Sm and Ta backlighters in 30-μm and 50-μm thick plastic foils, respectively. After the initial imprinting phase, the 2-D perturbations grew due to ablative RM instability before the onset of foil acceleration when they were further amplified by Rayleigh-Taylor instability. Experimental results agree reasonably well with 2-D hydrodynamic simulations and analytic models showing that the modulation growth in areal density is due to ablative RM instability.