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R.P. Drake, P.A. Keiter (Univ. of Michigan), H.A. Robey, O.A. Hurricane, B.A. Remington, D.D. Ryutov, J.O. Kane, R.J. Wallace (Lawrence Livermore Nat. Lab.), J. Knauer (Lab. Laser Energetics), Y. Zhang, J. Glimm (SUNY Stony Brook), J. Grove (Los Alamos Nat. Lab.), D. Arnett (Univ. of Arizona)
Results of the first spherically diverging, hydrodynamically unstable laboratory experiments of relevance to supernovae are reported. The experiments are accomplished by using laser radiation to explode a hemispherical plastic capsule that is embedded within a volume of low-density foam. The laser-generated shock briefly accelerates the capsule material outward, after which there is a long period of deceleration against the thick layer of less-dense foam. According to simulations, the spatial structure, near the interface between the two materials, is similar to that produced at the H / He interface in SN 1987A. In both the experiment and the SN, the interface is hydrodynamically unstable. In the experiment, the instability is seeded by an initial perturbation at this interface. The spherical divergence is sufficient to increase the wavelength of the perturbation more than threefold during the experiment. The evolution of the experiment, like that of a supernova, is well described by the Euler equations. The structure at the interface is diagnosed using x-ray radiography. Two-dimensional simulations of the experiment were performed both by using a radiation-hydrodynamics code and by using a pure hydrodynamics code with front tracking. The comparison with the data will be discussed, as will the comparison with data from a planar experiment.
Work supported by the US Department of Energy.