Influence of magnetohydrodynamic Rayleigh-Taylor instability on radiation of imploded heavy ion plasmas

The multicharged plasma implosion stability with respect to Rayleigh-Taylor axial modes and its modification by the electromagnetic field diffusion and radiation cooling is considered. The exterior and the interior parts of an imploded plasma shell are examined and stability and conditions for magnetohydrodynamic Rayleigh-Taylor instability are obtained. The external surface is always unstable. The interior instability appears, as a rule, to be under a significant degree of compression near the final stage of implosion. Theoretical results and numerical simulations using the two-dimensional ZETA code are [R. Benattar et al., 4th International Conference on Dense Z pinches, Vancouver (American Institute of Physics, Woodbury, 1997), p. 211] compared. The modeling of the implosion of wire arrays and nested tungsten wire arrays on the Z generator by the two-dimensional magnetohydrodynamic code ZETA, including radiation transport with local thermodynamic equilibrium (LTE)-nonequilibrium (non-LTE) approximation, is performed in order to study the influence of instability level on high-Z plasma radiation and to reproduce the experimental results. It is shown that it is possible to fit the experimental results if a 10% level of initial mass perturbation of the tungsten wire arrays is imposed. The dynamics of the implosion and the development of Rayleigh-Taylor instability are discussed. The plasma of the Z pinch is shown to be in a non-LTE regime. (C) 1999 American Institute of Physics. [S1070-664X(99)02601-4].