Freeze out of the RMI instability in cylindrically converging geometries

We present preliminary results from an experimental campaign demonstrating suppression of cylindrically converging Richtmyer-Meshkov instabilities (RMI) by the use of engineered voids. A compact pulsed-power generator (120 kA in 600 ns) vaporizes a cylindrical wire array of 30mm diameter, driving a cylindrically converging shock wave traveling at ∼ 2 kms⁻¹ through a surrounding gelatin dielectric. The shock wave interacts with shaped voids in the gelatin that redistribute the shock energy into several smaller shocks. These, in turn, interact with a concentric, sinusoidal interface between gelatin and air; characterized by Atwood number A = -1, wavelength λ = 0.9 mm, and amplitude a₀ = 0.1 mm.

Through differing vorticity delivered to the perturbed interface, the deconstructed shock wave ’freezes out’ the growth rate of RMI amplitude [1] as compared to cases without voids. Variations in amplitude and wavelength of the sinusoidal interface test the consistency of the suppression mechanism over different defect sizes. Hydrodynamics were captured by multi-MHz X-ray radiography at 32 μm spatial resolution and 176 ns interframe time, provided by the ID19 beamline of the European Synchrotron. Previous investigation showed that the engineered void technique was able to suppress RMI growth rate by 60% in planar geometry [2].

Extension of the presented work will utilize machine learning to optimize void shaping [3] and explore mitigation of single defects for potential application in ICF revolver schemes [4]