QUASI-ISOTROPIC APPROXIMATION OF GEOMETRICAL OPTICS METHOD WITH APPLICATIONS TO DENSE PLASMA POLARIMETRY

Abstract

Basic equations of quasi-isotropic approximation (QIA) of geometrical optics method are presented, which describe electro- magnetic waves propagation in weakly inhomogeneous and weakly anisotropic media. It is shown that in submillimiter range of elec- tromagnetic spectrum plasma in all modern thermonuclear reactors, both acting and under construction, manifest properties of weakly in- homogeneous and weakly anisotropic medium, even for extreme elec- tron density Ne » 10 14 cm i3 and magnetic fleld B0 » 5T accepted for project ITER. In these conditions QIA serves as natural theoret- ical basis for plasma polarimetry in tokamaks and stallarators. It is pointed out that Stokes vector formalism (SVF), widely used in po- larimetry, can be derived from QIA in a generalized form, admitting the rays to be curvilinear and torsiened. Other important result of QIA is development of angular variables technique (AVT), which deals directly with angular parameters of polarization ellipse and operates with the system of two difierential equations against three equations in form of SVF.