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

Abstract

Pulsed laser probing using Moiré deflectometry and Normaski interferometry was performed simultaneously to diagnose the electron density in a wire z-pinch plasma. The Moiré deflectometer 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 (1016 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.