Conical Wire Array Z-Pinches as a Tool to Explore the Physics of Wire Array Z-Pinches and for Radiation Pulse-Shaping

Abstract

Summary form only given. We investigate the use of the conical wire array Z-pinch to test the understanding of wire array Z-pinches using the MAGPIE generator (1 MA, 240 ns). In contrast to previous experiments that have used the precursor plasma flows in a conical wire array to model proto-stellar jets, here we concentrate on the dynamics of the conical wire array. The variation in magnetic field and inter-wire gap along the wire make conical arrays apt for testing the understanding of wire ablation. Mass ablation at different axial positions agrees with a rocket model with a fixed ablation velocity, and hence the mass ablation rate is inversely proportional to radius. Modulations in wire ablation are observed similar to those in cylindrical wire arrays. The wavelength of these modulations is similar to those in cylindrical arrays, and is fixed along the length of the wire. Near the wire the ablated plasma streams display an un-expected curved trajectory towards the anode. The axial variation of global magnetic field also affects the implosion phase of conical wire arrays, with wire breakage occurring first at the smaller diameter, cathode end of the array. The X-ray pulse shape is different from cylindrical wire arrays, partially due to an axial variation in the implosion time. In experiments with a large wire inclination angle a current carrying bubble is formed at the base of the array which propagates upwards