Plasma formation sourced from initial condition perturbations on high-current-density conductors

The electrothermal instability (ETI) is a Joule heating-driven instability that drives runaway heating in conductors driven to high current density and generates azimuthally correlated temperature and density perturbations in solid state metal. ETI may seed magneto Rayleigh-Taylor (MRT) instability growth in current-carrying, fuel-filled metallic liners used in magnetic direct drive fusion targets, reducing the stagnation pressure and temperature of the fuel. Previous z-pinch experiments examined growth of ETI from 99.999% pure aluminum rods by monitoring characterized micron-scale engineered defects (ED) machined into the rod surface. ED drive local current density amplification which drives early surface plasma formation. Informed design and material alterations have helped to better understand these high-current density explosions. The emission evolution of axially vs. azimuthally oriented ED pairs of varying size/separation has been studied. Sinusoidal perturbations, which are theorized to amplify current density, have been studied to determine how the varying ratio of amplitude over wavelength (A/λ) drives surface heating and plasma formation. Experimental data will be compared with 3D-MHD simulations.