High-Resolution Laser Schlieren Imaging of Coronal Plasma Evolution in 80-kA $X$-Pinches

X-pinches driven by an 80-kA current are investigated by using high-resolution dark-field laser Schlieren imaging. Results demonstrate the evolution of the low-density coronal plasma and the formation of an axial jet. Quantitative measurements of plasma expansion rates and the jet velocity are carried out for several materials.