Performance of the first undulator beamline U49-1-SGM at BESSY II

In July 1998, the first undulator beamline of BESSY II consisting of a spherical grating monochromator with variable included angle installed at an 83 period undulator with 49 mm period length was brought into operation. The characterization now has been completed. The energy range extends from about 90–1500 eV. An ultimate determination of the energy resolution of the monochromator generally fails because of the intrinsic lifetime broadening of the gases investigated. However, comparing the results at the N2 K-edge of the U125-1-PGM a very high energy resolution of more than 40,000 can be estimated at 200 eV. For high energy resolution a flux of 109–1012 photons per second has been recorded. The focus at the sample position has a FWHM size of 14 μm×37 μm. The synchronous drive of monochromator and undulator offers improved quality of spectra which have to be recorded over a large photon energy range.