Preliminary study on current disruption induced by magneto-Rayleigh-Taylor instability in Z-pinch plasmas

In Z pinch experiments, a thin plasma shell is accelerated inward by magnetic pressure. Severe magneto Rayleigh Taylor (MRT) instability on the outer side may tear the plasma shell and cause fuel mixture in inerial confinement fusion (ICF). To keep the integrity of the implosion shell, it is crucial to estimate the nonlinear development of MRT instability and establish indicators to describe the state of shell disruption. First, based on the thin layer approximation [Ott, Phys. Rev. Lett. 29, 1429 (1972)], the nonlinear MRT instability evolution of preseeded single mode perturbation is numerically calculated. To capture the saturation of the MRT instability caused by the reduction of driving current in the bubble region as the instability develops and the spikes expand, a partition function is introduced. Using the revised thin layer model, the decreasing trend in shell thickness at the bubble center is quantified. Second, based on open source MHD code PLUTO, the implosion process of the thin plasma shell under 0.5% random density perturbation is simulated. The characteristic time when the plasma shell disruption occurs with the minimum shell thickness as the main indicator is obtained. While observing oscillations in the axial kinetic energy of the shell and the growth rate of the current layer width a near the characteristic time, the time interval of shell disruption behavior is established with all the characters. Finally, the theoretical disruption time is computed from the revised thin layer model using the dominated wavelength from MHD simulation, and show good agreement with the simulated time interval.