Measurement of the linear polarization of Parametric X-radiation

The linear polarization of Parametric X-radiation (PXR) produced by 80.5 MeV electrons in a 13 μm thick silicon single crystal has been analyzed by means of a novel method of polarimetry exploiting directional information of the photoeffect in a charge coupled device consisting of 1.3×10 6 square pixels of 6.8 μm. The experiment was carried out at the Darmstadt superconducting linear accelerator S-DALINAC providing a low-emittance electron beam. The linear polarization of the (2 2 0) reflection observed in eight narrow angular bins between 20 ∘ and 21 ∘ with respect to the electron beam direction is consistent with complete local linear polarization. The orientation of the polarization plane, within measurement errors of typically 10 ∘ , varies over the diffraction pattern in such a way as to be expected from kinematical theory. The result of this experiment is in contradiction to the only other PXR polarization measurement performed so far.