Experimental observation of Rayleigh-Taylor modes in solids with strength
- Los Alamos National Lab., NM (United States); and others
Magnetically imploded cylindrical metal shells (z-pinch liners) can be used to drive a wide variety of hydrodynamics and materials properties experiments if they can be imploded at high velocity with good azimuthal symmetry and axial uniformity. As in all z-pinches, the outer surface of the liner is magneto-Rayleigh-Taylor (RT) unstable during acceleration and large-scale distortion of the liners from RT modes growing from initial imperfections could make liners unusable. According to first principles, material strength in the liner should reduce the growth rate of RT modes and material strength can render some modes analytically stable. To study the evolution of RT modes in liners, a series of experiments have been conducted in which high purity aluminum liners were accelerated with 6 MA, 7ms risetime driving currents. Initial sub-millimeter perturbations were machined into the outer surface of the liner and perturbation growth monitored with x-ray imaging optical, magnetic and impact probes, described in a companion paper. Results 2D MHD simulations were in excellent agreement with observed perturbation growth through the entire course of the implosions. Analytic theory of instability threshold in materials with strength adequately predicted the onset of instability growth and is also in good agreement with 2D calculations. When internal stress substantially exceeded the yield strength of the material, fluid like growth rates were observed as predicted by analytic theory. In general, for high conductivity and soft materials, theory and simulation adequately predicted the behavior of classic magneto-RT modes. This is the first direct verification of the growth of magneto RT in solids with strength known to the authors. Based on these results higher strength liner materials should further reduce the growth of RT modes. Two similar experiments have also been conducted with substantially higher strength, but also lower conductivity, alloys in which dramatically different behavior has been noted. Results of these experiments with higher strength are reported elsewhere in this conference.
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- OSTI ID:
- 346863
- Report Number(s):
- CONF-980601--
- Country of Publication:
- United States
- Language:
- English
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