Studies of hydrodynamics relevant to supernovae remnant physics with laser driven blast waves

Todd Ditmire,
University of Texas at Austin

Abstract: The evolution of hydrodynamic perturbations on radiative blast waves often plays an important role in shaping the structure of the interstellar medium. For example, the pressure-driven thin shell overstability, or Vishniac overstability, has been postulated by astrophysicists to account for much of the structure seen in certain supernova remnants, and may play an important role in the formation of stars. It was first postulated in 1983 by Ryu and Vishniac as a result of analysis of the effects of perturbations on thin shell blast waves. These hydrodynamic phenomena can be studied in the laboratory by the production of high Mach number blast waves in a gas driven by a high power laser driven explosion. In this talk, I will describe a variety of experiments which have produced blast waves in gases from the explosion of a laser plasma. Our experiments use both high energy (100 J to 1 kJ) laser pulses driving spherical explosions from irradiated solid targets, as well as cylindrical explosions in gases irradiated by ultrashort pulse lasers. In these laser experiments, we are able to produce blast waves with velocities up to 100 km/s. We have examined blast waves in a number of gases of varying composition and density. With these experiments we have, for example, observed shock trajectories in the radiative and non-radiative regimes, examined the formation of a radiative precursor ahead of a strongly radiating shock, and compared measured hydrodynamic perturbation evolution rates with well known theories.