Finite Electron Temperature Effects on Interferometric Measurements in Fusion Plasmas

Finite electron temperature effects on interferometry and polarimetry measurments in burning plasma are considered. In the limit when the wave frequency is much higher than the electron cyclotron frequency, the dispersion relation is derived to lowest order in $T_{e}/m_{e}c^2 \ll 1$. Previous analysis of the problem included non-relativistic dispersive corrections only [1]. We show that the relativistic effects are equally important and result in a change of the sign of the thermal correction to the Faraday rotation angle. Experimental observation of the ``sign'' effect could be important verification of fundamental relativistic physics in high-temperature plasma devices. The implication of the thermal corrections for ITER interferometer diagnostics is discussed. \newline \newline [1] S.E.Segre, V.Zanza, Physics of Plasmas, ${\bf 9}$, 2919 (2002)