Shockless compression of $z$-cut quartz to 7 GPa

Using a recently developed compact pulsed power generator (CPPG), $z$-cut quartz samples were subjected to shockless uniaxial strain compression to 7 GPa peak stress. Over this stress range, the behavior of $z$-cut quartz under shock compression [J. Appl. Phys. 88, 5671 (2000)] is nonlinear elastic and in good agreement with predictions based on the measured values of the second and third order elastic constants. In-material and free surface velocities were measured in the present work and analyzed, using a Lagrangian analysis, to provide a continuous loading curve for $z$-cut quartz. The wavelet speed-particle velocity (⁠$Cu-u$⁠, where $Cu≡(Δh/Δt)u$⁠) results were somewhat sensitive to the CPPG panel design details, as well as the velocity data acquisition and reduction techniques. Improvements to provide optimal data were discussed and used to provide accurate longitudinal stress-density response to 7 GPa (6% density compression). The $Cu-u$ curves, a more stringent measure of the material response to nonlinear compression, were within 0.6% of the values predicted using shock compression measurements. This excellent agreement demonstrates that the shockless compression response of quartz is indistinguishable from the shock response in the nonlinear elastic regime and provides a good foundation for comparing the inelastic response of solids under shockless and shock compression. The present work also demonstrated the use of the CPPG as a laboratory capability for examining the shockless compression of materials.