Use of low-density foams as pressure amplifiers in equation-of-state experiments with laser-driven shock waves

The applicability of foams to equation of state experiments with laser-produced shocks has been studied. The pressure increase due to impedance mismatch at the payload-foam interface was measured experimentally using sub-ns laser pulses smoothed with phase zone plates. Foams of density in the range $5–900\hspace{0.5em}{\mathrm{m}\mathrm{g}/\mathrm{c}\mathrm{m}}^3$ and of thicknesses of 50–150 μm were used. A model has been developed to study pressure amplification and the conditions under which the shock is stationary. Two-step two-material targets, allowing simultaneous measurements of the shock velocities in the two materials, were then used to obtain relative equation of state data. Pressures higher than 100 Mbar were achieved in gold.