Cross Check of Electron Density Distribution by Moiré-Schlieren Technique and Mach-Zehnder Interferometry

Simultaneous measurements of the electron density in a plasma focus by a Moiré-Schlieren technique and Mach-Zehnder interferometry were carried out to investigate the unavoidable error in the interferometry generated by refraction of the probe beam by the density gradient. The refraction angle was measured precisely by the Moiré-Schlieren technique, and the spatial distribution of the electron density calculated from the refraction angle agreed well with that obtained by Mach-Zehnder interferometry. The error produced by the refraction is found to be negligible if an N 2 -laser is employed as the light source for the plasma focus.