Dynamics of low-density coronal plasma in low current x-pinches

A series of experiments have been performed to study the low-density coronal plasma formation in x-pinches driven by a current generator capable of producing an 80 kA current with a rise time of 40 ns. Various wire materials including: aluminum. copper, nickel, stainless steel, molybdenum and tungsten were used. Simultaneous optical probing techniques, (schlieren, interferometry) and gated XUV imaging were used to record information in various density ranges. X-pinches consisting of aluminum, copper and molybdenum showed the coronal plasma streams towards the mid plane, where it converges. It then forms a sheath on either side of the cross-point, which moves with a velocity 6 x 10$^{5}$ \textit{cm s}$^{-1}$ towards the electrodes. The coronal plasma dynamics were significantly different in tungsten x-pinches, where no such sheath formation was observed. Experimental results quantitatively agree with 2D MHD simulations.