Highly accurate approximate solutions of the stokes equation for high electron density and long laser-wavelength

Imazawa, Ryota; Kawano, Yasunori; Kusama, Yoshinori

We have transformed the Stokes equation to new equations written in the polarization ellipse parameters: orientation angle, , ellipticity angle, , auxiliary angle, and phase shift angle. The new equations enable us to easily and comprehensively understand change of the polarization ellipse in the plasma. We have obtained new approximate solutions of the transformed Stokes equation in order to connect the measured values of and to the plasma parameters (the electron density and the magnetic field). We have compared our solutions and the approximate solutions proposed by other groups. Our solutions are the most accurate in the condition of magnetic confinement fusion plasmas and need the fewest assumptions. The approximation errors of our solutions are less than 2% of the domain of each polarization parameter ( and ) in up to the high electron density (710 m) and the long laser-wavelength (170 m).