Studies of solid liner stability in electromagnetic implosions
- Los Alamos National Lab., NM (United States)
The authors have conducted a series of experiments involving electromagnetic implosion of solid aluminum liners on the Pegasus II capacitor bank. These experiments consisted of liners on which single wavelength perturbations had been cut into the outer surface. Typical liner thickness was 400 mm and the usual material was the 1100 aluminum alloy. This alloy is relatively soft with a high conductivity. Recently comparisons have been made with harder but more resistive alloys. The sinusoidal perturbations ranged in amplitude between 10--100 mm and their wavelength between 0.5 and 2.0 mm. Radiographs of the imploding liners showed that the initial perturbations grew to amplitudes of 2000--4000 mm before completely rupturing and injecting flux into the region interior to the liner. Throughout the growth of the perturbations, there was virtually no coupling to other wavelengths. Even after liner disruption, the series of disk-like structures that resulted remained at the same scale length until impact with a center conductor. Two-dimensional MHD simulations of these experiments with the high conductivity Al-1100 alloy have yielded consistently good agreement, both qualitatively and quantitatively. Because the magnetic diffusion time in this alloy is comparable to or longer than the growth time, they find that the dynamics can be approximated by theories of Rayleigh-Taylor instability for which strength has been included. Recently, the authors have conducted two experiments with other aluminum alloys. These alloys have a significantly higher tensile yield strength than the 1100 alloy, but also somewhat high resistivity. Because the magnetic diffusion, ohmic heating, and loss of strength all occur on shorter times than does the growth, the forces acting on the liner are more distributed throughout the liner thickness than on the previous experiments. Qualitatively different features have been observed in the radiographs of these experiments. Two-dimensional MHD simulations and analysis will be presented of both sets of experiments and interpretations of the effect of conductivity on liner stability will be given.
- OSTI ID:
- 346864
- Report Number(s):
- CONF-980601-; TRN: 99:006131
- Resource Relation:
- Conference: 25. international conference on plasma science, Raleigh, NC (United States), 1-4 Jun 1998; Other Information: PBD: 1998; Related Information: Is Part Of IEEE conference record -- Abstracts. 1998 IEEE international conference on plasma science; PB: 343 p.
- Country of Publication:
- United States
- Language:
- English
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