Circularly polarized undulator radiation from the new double crossed undulator beamline at BESSY and its first use for spin resolved Auger electron emission spectroscopy

David R, Stoppmanns P, Yu S-W, Kuntze R, Müller N, Heinzmann U. Circularly polarized undulator radiation from the new double crossed undulator beamline at BESSY and its first use for spin resolved Auger electron emission spectroscopy. Nuclear Instruments and Methods in Physics Research A: Accelerators, Spectrometers, Detectors and Associated Equipment. 1994;343(2-3):650-654.The new beamline U2-FSGM at BESSY provides now circularly polarized radiation of high flux for photon energies between 20 eV and 200 eV. For users working at this beamline it is essential to measure the photon polarization. We have developed a new apparatus consisting of a Rabinovitch detector for analyzing the photon polarization, a 90° spherical electron spectrometer and a small retarding spherical Mott polarimeter (45 keV) for determining the electron spin polarization. As a first application we have measured the M3VV Auger emission from Cu(100) spin resolved after photo excitation by means of circularly polarized radiation of 76 eV