MHD instabilities in non-equilibrium Z-pinch driven by a multi-megaampere current

Magnetohydrodynamic (MHD) instabilities play a critical role in a number of pulsed power experiments in which multi-megaampere currents melt solid conductor surfaces and turn them into hot plasmas in a matter of microseconds or less. Complex motions that these plasmas exhibit lead to the development and growth of violent MHD instabilities that have the potential of disrupting the currents flowing through the conducting material or of introducing conductor material into locations where such material is not desired. The accelerated boundary of a non-equilibrium Z-pinch driven by a multi-megaampere current exhibits both curvature-driven m=0 (sausage) and Rayleigh-Taylor instabilities. The interplay between these instabilities and the effect it may have on the dynamics of the z-pinch is studied through a number of 2-D magnetohydrodynamic simulations performed with the state-of-the-art MHD code MHRDR. In result of the numerical simulations we have found that even though the magneto RT instability may have been developed during the discharge, the dominant instability for the current non-equilibrium Z pinch is m=0 instability. We have estimated that for the most of the discharge it grows exponentially with a constant growth rate, suggesting that the predictions of the ideal MHD theory can be applied to study the instability development of non-ideal, non-equilibrium Z pinches without any significant error.