The effect of material properties on solid line r stability during magnetic implosion

Summary form only given, as follows. We have been conducting studies of both stable and unstable solid aluminum liners in a Z-pinch configuration using a variety of pulse-power sources. The peak magnetic fields produced by these systems have ranged from 0.5 to 1.7 megagauss. Potential applications for such liners include studies of shock formation and propagation, equation of state, strength properties of materials at high strain rates, and the production of megagauss magnetic fields through flux compression. These applications all require a stable, well-characterized liner with reproducible behavior to drive these experiments. Unfortunately, the onset of what has been called Magneto-Rayleigh-Taylor instabilities, when excessive current is used to drive a liner, has been a limitation on the design of these liners. Conventional wisdom is that only material strength would delay the onset of these instabilities, and once the liner surface has melted the instabilities were free to grow. Analysis of the data from a wide range of experiments and comparison to one- and two-dimensional MHD simulations has permitted us to identify some of the dominant mechanisms that appear to contribute to the onset of these instabilities in a limited but important range of parameters. Careful variations of drive conditions, initial liner surface conditions, and eos properties (including conductivity) in an attempt to predict if a liner would be stable or unstable has brought to light a strong dependence on the nature of the material properties at or near the saturated liquid line of aluminum. Hence, while the nature of the instability may still be fundamentally driven by the acceleration of a fluid interface, the effect is drastically accentuated by the onset of liquid to vapor phase change in super heated liquid aluminum.