Mitigation of the Rayleigh–Taylor instability by sheared axial flows

The stabilizing effect of sheared axial flows on the Rayleigh–Taylor instability in Z-pinch implosions is investigated. Dispersion relations are derived that include the effects of a density discontinuity and a sheared flow which produce the Rayleigh–Taylor and Kelvin–Helmholtz instabilities. The dispersion relations are examined in two limiting cases of practical interest, a uniform plasma implosion and an annular plasma implosion. The analytical results show a region of parameter space which provides complete stability. The analytical model is verified with nonlinear calculations using experimental implosion parameters and geometries. The results indicate that mitigation of the Rayleigh–Taylor instability is possible with a sufficient sheared axial flow.