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.