Michael Wadas, University of Michigan
In high-energy-density shock-compression experiments, the desired state of compression is typically achieved by requiring shocks to pass through a sequence of different materials. In the present work, a theoretical approach for transiently strengthening such shock waves passing through interfaces of experimentally relevant impedance ratios is examined. A semi-analytical method based on characteristics analysis is used to solve the problem of a shock passing from one material to another through a region of non-uniform impedance. By appropriately designing this region, a greater shock strength can be achieved in the second material for a finite duration than in the absence of this region of non-uniform impedance. In the simplest case, a single intermediate material is used to bridge the impedance mismatch between the two outer materials and strengthen the shock. Incorporating multiple intermediate impedance steps between the two outer materials can further increase the strength of the transmitted shock wave, with an exponential discretization of intermediate impedance steps being the most effective distribution for shock strengthening. The technique is applied to the design of laser-driven dynamic compression experiments and the results of the analysis are verified via comparison to simulations performed with the HYADES hydrodynamics code. This shock-strengthening technique can be readily incorporated on existing experimental platforms and can extend experimental access to even more extreme pressure and temperature regimes that are important for both discovering new physics and validating existing equation of state models.
Abstract Author(s): Michael Wadas, Griffin Cearley, Jon Eggert, Eric Johnsen, Marius Millot