Experimental Investigation of Micrometer Scale Areal Density Variations in Metal Liners Driven by the 1 MA COBRA Pulsed Power Generator*

On the 20 MA Z machine, the seed for the MRT instability was mitigated in the Magnetized Liner Inertial Fusion experiment using a thick dielectric coating.$^{\mathrm{1\thinspace }}$We have used high-resolution radiography to study the development of small-scale (\textasciitilde 10-30 $\mu $m) features in thin foils on the 1 MA, 100-200 ns COBRA pulsed power generator$^{\mathrm{2}}$. We examined those features quantitatively in a 16 \textmu m thick cylindrical Al liner, where we show areal density variation of up to 40-50{\%}. We then show how the features' wavelength decreases when the material is changed from Al to Ni, Cu, and Ti, going from 21 \textpm 4 \textmu m for Al to 11 \textpm 2 \textmu m for Ti. Moreover, we show that expansion inhibition on both sides by dielectric material reduces small-scale feature size and density, and we show how pattern seeding can affect those parameters. 1. T. J. Awe \textit{et al.}, ``Experimental Demonstration of the Stabilizing Effect of Dielectric Coatings on Magnetically Accelerated Imploding Metallic Liners'', Phys. Rev. Lett., 2016, \textbf{116} 065001. 2. J. D. Douglass \textit{et al.}, ``Capabilities of the Reconfigured COBRA Accelerator'', Proceedings of the 15th IEEE Pulsed Power Conference, June 13-17, 2005, pp. 273-276.