Proton radiography measurements and models of ejecta structure in shocked Sn*

We discuss experimental validation of ejecta source mass and velocity models using proton radiography. We have performed ejecta measurements at the Los Alamos proton radiography facility on 7 mm thick 81 mm diameter Sn samples driven with a plane-wave high explosive lens (PBX9501$+$ TNT). The surface of the Sn, in contact with He gas at an initial pressure of 7 atmospheres, was machined to have 4 concentric sinusoidal features with a wavelength of $\lambda =$2 mm in the radial direction and amplitude h$_{\mathrm{0}}=$0.159 mm (kh$_{\mathrm{0}}=$2$\pi $h$_{\mathrm{0}}$/$\lambda =$0.5). The shock pressure was 27 GPa. 42 images were obtained between 0 and 14 $\mu $s from the time of shock breakout at 275 and 400 ns intervals. The Abel inverted density profiles evolve to a self-similar density distribution that depends on a scaling variable z/v$_{\mathrm{s}}$t where v$_{\mathrm{s}}$ is the spike tip velocity, z is the distance from the free surface and t is the time after shock breakout. Both the density profiles and the time dependence of the mass per unit area in the evolving spikes are in good agreement with a Richtmyer-Meshkov instability based model for ejecta production and evolution.