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Title: A model of an incompressible multi-wire z-pinch
Author: Radosavljevic, Slobodan
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2013
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Despite having been studied for many years, z-pinches still pose many questions of researchers. On the one hand, the combinations of skin effects, magnetism, thermodynamics and fluid mechanics are often too complex to model accurately together, yet on the other hand it is difficult to observe the whole broad range of phenomena experimentally because of the nanosecond timescales of the pinch implosions. This work takes a magnetohydrodynamic approach to studying the implosion dynamics of a multi-wire z-pinch. A model of an array of incompressible vaporised wires is introduced. The free surface is evolved under the influence of inertial and magnetic effects using a Boundary Element Method (BEM). While there are some results available for perfectly conducting wires, we will also look at the other extreme, of low conductivity, to assess the different physical effects. Array implosions rates and deformation of the wire plasma along the azimuth are shown to be different in the two cases. However, there are some shared traits; in both conductivity limits, the plasma is shown to oscillate in a remarkably similar manner for small wire numbers. The effect of varying the current pulse profile is also considered. Attempts are made to model the collision and coalescence of the plasma columns upon impact, and to study the post-merge dynamics of the resulting annulus. There is evidence of jets being emitted from either side of the collision, into both the magnetically contained exterior and into the (effectively) pressure-free interior. While the BEM seems to cope with the exterior jet, the interior becomes unstable, possibly due to a lack of the stabilising effect otherwise provided by the magnetic field.
Supervisor: Mestel, Jonathan Sponsor: Engineering and Physical Sciences Research Council ; Atomic Weapons Establishment
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available