Refractive index and elastic properties of z-cut quartz shocked to 60 kbar

Shock wave experiments were performed to characterize z-cut, alpha -quartz as an optical window for velocity interferometry measurements. Refractive i ndex changes and shock velocities were determined to 60 kbar peak stress. R esults indicate that the window correction to velocity measurements is a co nstant fraction of the actual particle velocity, Deltau/u=0.081 07. Shock v elocity measurements provide the Hugoniot curve to 60 kbar, and yield the f ourth-order elastic constant, C-3333=174 810 kbar. By combining the velocit y correction factor and the shock velocity measurements, the refractive ind ex is determined to be a linear function of density. This finding is used t o show that the velocity correction appropriate for a step jump may be appl ied to monotonically time-dependent wave forms with negligible error. The p resent work has demonstrated the use of z-cut quartz as an optical window t o 60 kbar. (C) 2000 American Institute of Physics. [S0021-8979(00)02023-5].