End-On Laser Interferometry of Wire Array Z-Pinch Implosions on the MAGPIE Generator

End-On interferometric measurements of the electron density distribution of wire array z-pinches has revealed striking differences in the behavior of ablation plasmas. A change in wire material from aluminum to tungsten results in a change from a highly collisional structure dominated by shock formations to a much less collisional regime. Analysis of the results will be presented and comparisons made to both simulations produced using the GORGON MHD code, and calculations of the expected mean-free-path of the plasma. Experiments were carried out on the MAGPIE generator (1.4 MA peak, 240ns rise) at Imperial College, London. A two-color Mach-Zender imaging interferometer was used to collect the data. This uses the 2$^{nd}$ and 3rd harmonics (532nm and 355nm) of a pulsed Nd:YAG laser with a pulse duration of $\sim $500ps.