Interferometry and refraction measurements in plasmas of elliptical cross-section

The measurement of electron densities using interferometry and refraction measurements in plasmas with cross-sections where the electron density contours are concentric ellipses is examined. Transforms are found for both interferometrically deduced optical path-length differences and refraction angle data obtained from elliptical cross-section plasmas, which in the limit of small amounts of refraction adjust the data to values which appear as if they were obtained from equivalent circular cross-section plasmas. The transformed data can be inverted to give electron densities using standard techniques developed for circular cross-section plasmas (e.g. Abel inversion). To check the accuracy of the transforms for moderate to large amounts of refraction (>or=0.1 rad), refraction of light in elliptical cross-section plasmas is examined using numerical ray tracing.