Imaging of Hydrodynamic Perturbation Evolution in a Laser-Driven Foil with a Rippled Rear Surface Using a Fresnel Phase Zone Plate*

Two-dimensional x-ray radiography is used to measure hydrodynamic perturbation evolution in a laser-driven foil with a rippled rear surface. The ablatively driven system was generated on the OMEGA laser with up to few-nanosecond-duration laser pulses at focused intensities above 10$^{\mathrm{14}}$ W/cm$^{\mathrm{2}}$. The modulated rear-surface dynamics were imaged following the passage of a strong, unsupported shock wave. Radiographs were obtained using a 4.75-keV Ti or 6.70-keV Fe He-like resonance line area backlighting source coupled to a Fresnel phase zone plate imager and an SI-800 x-ray charge-coupled device. Static resolution grid tests confirm the achievement of sub-2-$\mu $m spatial resolution. The hydrodynamic evolution of planar targets with initial rear surface perturbations of varying wavelength, with and without mid-Z dopants or a high-Z rear-surface coating, are studied and compared with synthetic x-ray radiographs generated from numerical simulations using the computer codes DRACO and Spect3D.