Laser driven shock wave acceleration experiments using plastic foams

In this letter, we present an experimental study of shock propagation in a decreasing density gradient which is a common feature in many astrophysical objects. An original scheme for the targets has been designed to investiga te the case of a discrete density step. Using foams in a wide density range (20-400 mg/cm(-3)), we obtained accurate data on shock acceleration at the solid-foam interface. Results are discussed and compared with models. (C) 1999 American Institute of Physics. [S0003-6951(99)02245-7].