Supersonic jet formation and propagation in x-pinches |
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Authors: | D M Haas S C Bott J Kim D A Mariscal R E Madden Y Eshaq U Ueda G Collins IV K Gunasekera F N Beg J P Chittenden N Niasse C A Jennings |
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Institution: | 1. University of California San Diego, La Jolla, CA, USA 2. Imperial College London, London, UK 3. Sandia National Laboratories, Albuquerque, NM, USA
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Abstract: | Observations of supersonic jet propagation in low-current x-pinches are reported. X-pinches comprising of four 7.5 ??m 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. |
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