Multichannel laser interferometer-refractometer with high spatial and temporal resolutions

A novel scheme combining an interferometer and refractometer for simultaneous plasma density and plasma density gradient measurements is described. The scheme employs a ribbon laser beam obtained from one-dimensional laser beam expansion by a pair of cylindrical lenses. This beam shape allows measurements at several spatial locations simultaneously. The beam deflection measurements give additional important information on the spatial distribution of plasma density gradient in the direction perpendicular to the major axis of the expanded beam. Fast pin photodiodes are used as light detectors for temporal resolution better than 1 ns. The high power (700 mW) of the Ar ion laser allows 0.1/spl deg/ phase resolution and simultaneously 0.1 mrad refractional deflection angle.