The Role of Ion Acoustic Instability in the Development of the Azimuthal Current Density Profile in Liner Experiments at 1 MA

Recent work reported on the current density in pulsed-power-driven liners where a vacuum gap was introduced in the power feed connecting the liner to the generator. The resultant gap flashover generates azimuthally localized current-carrying plasma channels, which can create an azimuthal nonuniformity in the current density. The current density evolves during the current pulse, but nonuniformity is observed through the experiment timescale. Magnetohydrodynamic simulation work in 3-D demonstrates the difficulty in reproducing the experimental data within a limited computational domain, and those boundary conditions may dominate this paper. The development of current-driven instabilities in the plasma channels can explain the liner current density evolution, and specifically the ion acoustic instability can account for the main features observed in the experiments.