Experimental observation of Rayleigh-Taylor growth as a function of wavelength in the warm dense matter regime*

``Classical'' Rayleigh-Taylor (RT) growth is characterized by a growth rate $\gamma=\sqrt{k g A_n }$, where $k$ is the wavelength of the unstable mode, $g$ is the acceleration, and the Atwood $A_n$ number characterizes the magnitude of the density jump at the interface. Here we present the results of a set of experiments using face-on x-ray radiography to measure RT growth in a plastic rippled sample. Acceleration of the sample is provided by the stagnation of a releasing shocked plastic ``reservoir,'' which is directly driven by approximately 1 kJ of laser energy at the OMEGA facility. The growth of pre-imposed ripples is recorded using transmission x-ray radiography of a vanadium He$_\alpha$ source, where the opacity of the sample is calibrated to the ripple amplitude. We report the results of experiments at 30 $\mu$m and 60 $\mu$m initial wavelengths, and compare the data to 2D hydrodynamic simulations.