Study of the time-resolved, 3-dimensional current density distribution in solid metallic liners at 1 MA

Abstract

We present a study of the time varying current density distribution in solid metallic liner experiments at the 1 MA level. Measurements are taken using an array of magnetic field probes which provide 2D triangulation of the average centroid of the drive current in the load at 3 discrete axial positions. These data are correlated with gated optical self-emission imaging which directly images the breakdown and plasma formation region. Results show that the current density is azimuthally non-uniform and changes significantly throughout the 100 ns experimental timescale. Magnetic field probes show clearly motion of the current density around the liner azimuth over 10 ns timescales. If breakdown is initiated at one azimuthal location, the current density remains non-uniform even over large spatial extents throughout the current drive. The evolution timescales are suggestive of a resistive diffusion process or uneven current distributions among simultaneously formed but discrete plasma conduction paths.