Magneto-Rayleigh-Taylor Instability Driven by a Rotating Magnetic Field: Cylindrical Liner Configuration

We investigate and revisit the deployment of a directional time-varying (rotating) driving magnetic field to suppress the magneto-Rayleigh-Taylor (MRT) instability in dynamic Z-pinches. A rotational driving magnetic field is equivalent to two magnetic-field components, Θ and Z, that alternate in time, referred to as an alternate Theta-Z-pinch configuration. We consider a finitely thick cylindrical liner configuration in this paper. We numerically integrate the perturbation equation to stagnation time based on the optimal background unperturbed trajectories. We assess the cumulative growth of the dominant mode selected by some mechanism at the beginning of an implosion. The maximum e-folding number at the stagnation of the dominant mode of an optimized alternate Theta-Z-pinch is significantly lower than that of the standard Theta- or Z-pinch. The directional rotation of the magnetic field acts to suppress instabilities, independent of the finite thickness of the liner. The finite thickness effect plays a role only when the orientation of the magnetic field varies in time, whereas it does not play a role in the standard Theta- or Z-pinch. The rotating frequency of the magnetic field and the thickness of the liner both have a monotonic effect on suppression. Their synergistic effect can enhance the suppression of the MRT instability. Because the MRT instability can be well suppressed in this way, the alternate ThetaZ-pinch configuration has potential applications in liner inertial fusion that uses a magnetically driven liner to directly compress the fuel target to initiate fusion.