Comparison of sensitivities of Moiré deflectometry and interferometry to measure electron densities inz-pinch plasmas

Pulsed laser probing using Moir´ e deflectometry and Normaski interferometry was performed simultaneously to diagnose the electron density in a wire z-pinch plasma. The Moirdeflectometer has a higher sensitivity while the Nomarski interferometer is able to probe higher densities. The advantages of each technique permitted us to measure a wider range of densities. This includes the low-density coronal plasma with density of an order of magnitude lower (10 16 cm −3 ) than that which can be measured by interferometry. Furthermore, our optical probing presents a low response to mechanical vibrations as it is not necessary to use a separate reference beam as in a Mach-Zehnder interferometer. The experiments were performed on a 160 kA current generator at Imperial College, London, for three different discharge configurations in order to study the initial resistive heating stage of the wire z-pinch. (Some figures in this article are in colour only in the electronic version)