Supersonic jet formation and propagation in x-pinches

Abstract

Observations of supersonic jet propagation in low-current x-pinches are reported. X-pinches comprising of four 7. 5 μm diameter tungsten wires were driven by an 80 kA, 50 ns current pulse from a compact pulser. Coronal plasma surrounding the wire cores was accelerated perpendicular to their surface due to the global J×B force, and traveled toward the axis of the x-pinch to form an axially propagating jet. These jets moved towards the electrodes and, late in time (~150 ns), were observed to propagate well above the anode with a velocity of 3. 3±0. 6×104 m/s. Tungsten jets remained collimated at distances of up to 16 mm from the cross point, and an estimate of the local sound speed gives a Mach number of ~6. This is the first demonstration that supersonic plasma jets can be produced using x-pinches with such a small, low current pulser. Experimental data compares well to three-dimensional simulations using the GORGON resistive MHD code, and possible scaling to astrophysical jets is discussed. © 2011 The Author(s).