Novel convergent hydrodynamic instability experiments on Z

Hydrodynamic instabilities are critically important for a variety of physical phenomenon. In astrophysics, the Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities can break the spherical symmetry in supernovae explosions and the associated mixing can enable the synthesis of heavy and intermediate mass elements. In inertial confinement fusion, they impact the confining ability of the tamper and mix impurities into the hot fuel, ultimately degrading the thermonuclear fusion production.

At the Z Machine at Sandia National laboratories, we recently developed a novel platform for investigating these phenomena in a high-energy-density, converging system.¹ A cylindrical liner is filled with liquid deuterium and magnetically imploded with 24 MA of current. This launches a radially converging shock in the deuterium that interacts with an on-axis beryllium rod machined with sinusoidal perturbations. The passage of the shock drives the RM process, causing perturbations to grow as the rod implodes. In the final stage of evolution, the shock reflects off-axis and re-shocks the perturbed interface, introducing additional vorticity and complex instability development.

In this talk, we will present the evolution of single- and multi-mode perturbations designed to investigate linear-to-non-linear growth and material mixing. These data provide challenging tests for theoretical models and hydrodynamic simulations such as xRage that explicitly model the perturbation evolution with adaptive-mesh-refinement. Detailed comparisons to these models will be presented.

*SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.

¹Knapp et al., Phys. Plasmas, 27, 092707 (2020).