GROWTH OF THE RAYLEIGH-TAYLOR INSTABILITY IN AN IMPLODING Z-PINCH

Rayleigh-Taylor (RT) instability of cylindrical, imploding plasma Line rs in a Z-pinch is analysed. The reduction in total perturbation growt h for multicascade systems (multiple imploding shells) is presented. T his reduction is effective if the pressure produced by the impacting s hell exceeds the magnetic pressure at the time of impact. Analytical a nd numerical solutions are also obtained for the RT instability of an imploding plasma liner accelerated into undisturbed plasma. The snowpl ow model is used in which the mass encountered by the imploding magnet ic piston is swept into an infinitely thin sheath. A shock front launc hed ahead of the liner is shown to reduce the growth rate. It is also shown that accumulating the mass increases the growth rate. However, t he total perturbation growth can be reduced if the liner accumulates t he mass during the implosion compared to a liner with the same mass im ploding into vacuum. Finally, it is shown that the final kinetic energ y density for a given shell nonuniformity is largest if the final line r mass is accumulated during the implosion. (C) 1997 American Institut e of Physics.