Arbitrary polarization control with a segmented APPLE-II undulator

A newly developed four-segmented APPLE-II undulator enables arbitrary polarization control in the soft to tender X-ray region. The undulator is installed at NanoTerasu BL13U, aiming for X-ray absorption spectroscopy over a wide energy range, 180-3000 eV, with versatile photon polarizations. By adjusting the phase difference of the synchrotron radiation using electromagnetic phase shifters, arbitrary orientations of linear polarization were obtained from left and right circularly polarized radiation. Elliptically polarized radiation was also generated from vertical and horizontal linearly polarized radiation. In addition, the ellipticity angles were successfully controlled. Circularly polarized radiation in the tender X-ray region is considered to be achieved by utilizing the third harmonic. Methods and performance of polarization control of the segmented APPLE-II undulator using the phase shifters are presented.