Polarization Measurement and Modeling of Visible Synchrotron Radiation at Spear3

Synchrotron radiation from dipole magnets is linearly polarized in the plane of acceleration and evolves toward circular polarization with increasing vertical observation angle. The intensity of the x-y field components can be modeled with Schwinger's theory for the angular-spectral power distribution. Combined with Fresnel's laws for reflection at a mirror surface, it is possible to model field polarization of visible SR light in the laboratory. The polarization can also be measured with a polarizer and quarter wave plate to yield Stokes' parameters S0-S3. In this paper we present measurements and modeling of the visible SPEAR3 SR beam in terms of Stokes' parameters and plot on the results on the Poincaré sphere.