Measurement of the polarization characteristics of coherent diffraction radiation in the subterahertz range

A cycle of measurements of the polarization characteristics of coherent transition radiation and coherent diffraction radiation at the LUCX accelerator has been performed. It has been shown that the results of measurements of the linear polarization component in both cases are well described by a theoretical model according to which the degree of elliptical polarization of diffraction radiation is close to 100%. This fact indicates a significant contribution (up to 90%) of the circularly polarized component of diffraction radiation for radiation angles with respect to the direction of mirror reflection exceeding $\gamma^-$ ($\gamma$ is the Lorentz factor).