A vacuum ultraviolet polarimeter with quadruple-reflectors: Polarization measurements at the TERAS BL-5 beamline

Variable-polarization synchrotron radiation is useful for measurements of circular dichroism (CD) in the vacuum ultraviolet (VUV) and soft X-ray regions. Since the polarization of the radiation is modified by beamline optics, it is therefore necessary to directly measure the polarization state of the light incident onto a sample in order to achieve quantitative measurements of the CD spectra. A reflection type polarimeter was designed and constructed to examine the polarization characteristics of the variable-polarization synchrotron radiation. The polarimeter consists of two quadruple reflectors which function as a phase shifter and a quasi-linear polarizer. The polarimeter is designed to be very compact. The compact size allows for easy and fast measurements of the complete set of Stokes parameters. The polarization states of the light output from the TERAS BL-5 beamline were measured using the new polarimeter in the vacuum ultraviolet range. The polarization states data of the light at the beamline were used for CD measurements, which yielded quantitative CD spectra in the VUV range.