Two-dimensional Rayleigh-Taylor instability in SATURN Z-pinch implosions

Summary form only given, as follows. Experiments and numerical simulations have shown some examples of marked differences between annular and uniform core gas puff implosions using the SATURN pulsed power generator. Analytic modeling and magnetohydrodynamic simulations have been used to further investigate the instability of the plasma vacuum interface in gas puff implosions driven to velocities in excess of 100 cm//spl mu/sec. Numerical calculations were carried out using the two-dimensional single-fluid magnetohydrodynamic code MACH2. The instabilities develop in both the annular and uniform puffs from the nonuniform gas flow field that forms as the gas expands from the injection nozzle into the vacuum diode. For both the annular and the uniform puff the characteristics of the instability remain qualitatively the same as long as there is gas in front of the unstable plasma region. The instability develops in a classical fashion with fast growing short wavelength modes. The instabilities are confined to a narrow region consisting of a shock wave/current sheath which propagates into the undisturbed gas in front of the sheath. During this phase of instability development, growth is limited to the narrow unstable region and has characteristics indicative of ´snowplow stabilization´. After the unstable region breaks through the inner edge of the annular puff nonlinear growth increases as mass ejected from the bubble regions is not replenished by the ´snowplow´ effect.