A multi-shock and release platform for measuring strength on a gas-gun up to 5 Mbar

We have developed a multi-shock loading platform for measuring strength in the Mbar regime on a two-stage gas-gun. Multi-shock loading can be used to achieve an off-Hugoniot state that exceeds the single-shock melt pressure while maintaining the solid state. Upon initial release from the multi-shocked state, loading reversal provides sensitivity to material strength. As shown through ARES hydrocode simulations, an impactor consisting of a low-, medium-, and high-impedance material, such as TPX, Al, and Ta or Pt, can produce a quasi-isentropic loading path in Ta up to 5 Mbar pressure with a low homologous temperature (T/ Tmelt=0.1–0.25). Simulations are used to evaluate sensitivity to strength and sources of error from impactor non-uniformity. Example designs for impactors and multi-step targets are developed for low and high compressibility materials as well Ta, which serves as a strength benchmark material.