Finite electron temperature effects in plasma polarimetry and interferometry

The effects of a finite electron temperature on the refractive index N and on the evolution of polarization for radiation propagating in a magnetized plasma are considered. Analytic expressions for N and for the Stokes vector evolution equation are found to lowest order in Te/mec2. For interferometric and polarimetric measurements on typical plasma confinement configurations, the thermal effects are found to be significant. Neglecting them can lead to systematic errors in polarimetry greater than 10% for a temperature of 5 keV and to a systematic (positive) error on electron density from interferometry of 3% for Te=15 keV.