A novel approach to Hugoniot measurements utilizing transparent crystals

Abstract

A new absolute equation of state measurement technique is described and demonstrated measuring the shock state and the refractive index of MgO up to 226 GPa. This technique utilizes steady shock waves and the high-pressure transparency of MgO under dynamic shock compression and release. Hugoniot measurements performed using this technique are consistent with the previous measurements. A linear dependence of the shocked refractive index and density is observed up to 226 GPa, over a magnitude greater in pressure that previous studies. The transparency of MgO along the principal Hugoniot is higher than any other material reported to date. We observe a significant change in the refractive index of MgO as the Hugoniot elastic limit is exceeded due to the transition from uniaxial to hydrostatic strain. Measurements of the elastic-plastic two-wave structure in MgO indicate a nucleation time for plastic deformation.