Off-Hugoniot strength measurement of tantalum up to 3.3 Mbar using multi-shock loading

We present experimental details and initial results from multi-shock experiments designed to measure the off-Hugoniot strength of tantalum at pressures ranging from 2.5 to 3.3 Mbar, the first reports of strength measurements made on a gas gun at pressures that exceed the shock-melt pressure. A three-layered gas gun impactor consisting of materials arranged from low to high impedance can produce a quasi-isentropic loading path with a low homologous temperature. This impactor design provides a means of accessing high pressures without melting a material and allows for measuring strength on initial release from high pressure. Additionally, we detail the impactor design modifications implemented to prevent delamination. Comparisons to forward modeling simulation and ramp-release techniques will be presented.