Numerical and experimental studies of magnetic Rayleigh-Taylor instabilities in solid liners

Summary form only given. We have studied the nonlinear evolution of Magnetic Rayleigh-Taylor (MRT) instability in solid aluminum liners. Two-dimensional MHD modeling of the configuration have been performed using the measured current pulseform of the PEGASUS II capacitor bank as a magnetic field source. The liner configuration consisted of a solid aluminum annulus 20 mm long and 0.4 mm thick. The outer surface of the liner was machined with a sinusoidal ripple. Half of the liner was scribed with one wavelength, the other half with another wavelength. A series of experiments was conducted with a smooth surface and ripple wavelengths of 0.5, 0.75, and 2.0 mm. The peak-to-peak ripple amplitude was varied between 0.025 and 0.10 mm, but the ration of the initial amplitude to wavelength never exceeded 7%. Diagnostics consisted of radiography, a center-conductor B-dot probe, and transmission line pulsed power diagnostics. The inner surfaces of the liners were coated with a thin film of gold (Au) to permit measurement of material deformation at various stages of the instability growth. Three radiographs, at different times, were taken for each experiment. The center-conductor magnetic probe was used to measure the magnetic field penetration through the liner. Initial comparisons between the data and the MHD calculations showed excellent agreement with respect to nonlinear instability growth and with the time of field rupture of the liner.