Formation of a shock wave in aerogel irradiated with a high-current pulsed electron beam

The propagation of pressure jumps excited by a high-current pulsed electron beam in SiO2 aerogels with density ranging from 0.025 to 0.25 g/cm(3) is investigated using a laser differential interferometer and optical methods. Spallation on the back side of the aerogel targets is observed and the velocity of the spallation fragments is measured. The expansion velocity of the aerogel in the direction of the electron beam is determined. The parameters of the shock adiabat are established in a wide range of aerogel porosities. The depth of the energy-deposition zone of the electron beam is determined experimentally as a function of the aerogel density in the range from 0.015 to 0.25 g/cm(3). A model describing highly porous materials which reflects the fractal properties of highly porous aerogels is developed on the basis of the experimental data. Numerical calculations of the observed phenomena are performed. (C) 1999 American Institute of Physics. [S1063-7842(99)00412-2].