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Dynamics of laser-driven shock waves in fused silica

University of British Columbia

The formation of a laser-driven shock in fused silica was observed experimentally. Fused silica slabs were irradiated with 0.53 /µm laser light in a pulse of 2 ns FWHM at intensities ranging from 10¹² W/cm² to 5 x 10¹³ W/cm², producing a pressure pulse ranging from < 30 GPa to 500 GPa. Shock trajectories were observed using streaked shadowgram and schlieren methods. The experiment was modelled with a one-dimensional Lagrangean laser-plasma hydrocode. Comparison of the simulation results with the experimental observations indicate that the high pressure shock develops anomalously slowly at intensities > 1 x 10¹³ W/cm². Furthermore the shock displayed non-steady propagation for a transient period following its formation. The non-steady propagation is interpreted to be due to a relaxation process in the phase transformation of the fused silica to the high pressure stishovite phase which occurs in the shock front. The slow formation of the shock at high intensities is consistent with a significant volume collapse (phase transition) possibly induced by isentropic compression; however, this interpretation is uncertain due to the complications introduced by non-equilibrium thermodynamics and the possibility of two-dimensional motion.

Text

2010-07-27

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http://hdl.handle.net/2429/26970

Physics

University of British Columbia

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