Shock impedance matching experiments in foam-solid targets: implications for 'foam-buffered ICF'

The influence of foams on laser-produced shocks has been studied experimentally using sub-ns laser pulses smoothed with phase zone plates and focused on layered foam-aluminium targets. A strong pressure increase was measured when the foam was present in comparison with that obtained by focusing the beam directly onto the aluminium target, due to impedance mismatch at the aluminium-foam interface. Results are compared with computer simulations. The impact of these measurements on the possible use of 'foam-buffered targets' for direct-drive inertial confinement fusion is briefly discussed.