Three-dimensional Rayleigh-Taylor instability in Saturn z-pinch implosions: a study with MACH3

Summary form only given. A new portable parallel physics simulation code, called MACH3 (multiblock arbitrary coordinate hydrodynamics code in three spatial dimensions), has been developed by the Phillips Laboratory for performing three dimensional collisional plasma simulations. This code is based on the widely-used and useful two-dimensional code, MACH2. Both are arbitrary Lagrangian Eulerian codes with sophisticated physics and numerical models to allow the user great flexibility in solving non-ideal magnetohydrodynamic (MHD) problems. A preliminary series of calculations has been performed to investigate three-dimensional effects in an imploding annular plasma gas puff driven by the Saturn pulsed power generator at Sandia. Plasma instabilities are seeded by an initial periodic density perturbation in the azimuthal direction, with a random component in the r-z plane. Results show the interaction between the r-z plane and the r-/spl thetav/ plane modes and their effect on the sheath dynamics during the /spl sim/65 ns implosion. Comparison between calculations using MACH2 and MACH3 show the degree of applicability of the premise of the dominance of r-z plane growth usually made to justify 2-dimensional simulations.