Generation of linearly polarized transition radiation X-ray beam

We have successfully produced almost linearly polarized X-ray beam by extracting Transition Radiation (TR) X-rays through a rectangular slit 3 mrad long and 0.2 mrad wide placed downstream of a 7.5-μm thick Kapton foil stack radiator bombarded with a 1-GeV electron beam. Our calculation predicted that the linearity of TR photon was 94% for both a vertical and a horizontal slit. The measured results for the vertical slit agreed with the calculation, and the linearity of obtained TR X-ray beam was more than 90%. For the horizontal slit, the measured results differed from our expectations due to a prolonged electron beam profile. In the polarization measurement of TR photon we used the Bragg reflection on a lithium fluoride crystal [LiF(200)] which acted as both a polarimeter and a spectrometer.