Computational Magnetohydrodynamic Investigation of Flux Compression and Implosion Dynamics in a Z-pinch Plasma with an Azimuthally Opposed Magnetic Field Configuration

Magnetic flux compression is a well established technique for the generation of ultrahigh magnetic fields, large currents, and large energy densities. It has been suggested as a means for power density amplification on Z-pinch generators such as Decade Quad, at Arnold Engineering Development Center, and it may be especially suitable as a means for producing higher powers of K-shell radiation from high atomic number loads such as titanium. Although many one-dimensional models of flux compression on Z-pinch generators exist, an improvement in understanding is needed about the physics and implosion dynamics on a two-dimensional level. To this end, a two-dimensional resistive magnetohydrodynamic code was used to study a particular flux compression concept for use on Decade Quad. In the concept under study, compression occurs for self generated opposing azimuthal magnetic fields. In order to provide appropriate boundary conditions for the simulations, a non-linear circuit model was developed to enable calculation of the dynamically changing inductive and resistive impedances of the two coupled current paths such that they are consistent with the developing plasma. Good flux compression is observed despite magnetic flux losses. Two dimensional calculations are shown to match reasonably well with one-dimensional results. However, results also indicate Rayleigh-Taylor instabilities significantly affect implosion dynamics through the creation of isolated magnetic flux pockets, formation of circular currents, and the redistribution of current flow. It is also found that the Aluminum plasma armature shorts out on the stator, and thereby causes a nonideal current distribution in the titanium plasma. Consequently, the titanium plasma does not receive sufficient energy transfer for efficient K-shell radiative emission.

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