Photon Doppler velocimetry of ejecta from shock-loaded samples

The report addresses the problem of recovering the ejecta parameters from PDV data. The results of PDV-measurements of ejecta production from shock-loaded Pb samples are presented. Shockwaves were generated by a flyer-plate accelerated up to 3 km/s. Depending on the sample thickness, the shock-breakout pressure varied from 23 to 45 GPa. The ejecta transport occurred in air. Spectral profile $E(\omega)$ of heterodyne beats underlies our analysis of the experiments. Under the assumption that ejected particles are disordered, the profile square $\vert E(\omega)\vert^2$ is subject to the transport equation which accounts for multiple scattering and absorption of the probing beam in the ejecta cloud. We solve the transport equation with the discrete-ordinate code. Adjusting the free surface velocity, the optical thickness and the parameters of the velocity distribution of the ejecta scattering coefficient, we gain a good fit of the calculated profile to the PDV-measured one. Such an approach enables us, based on the ejecta optical model, to recover the areal density and the density-velocity distribution from PDV data, e.g., to determine how this distribution changes in time due to the particle slowing-down in air.