PGM beamline with constant energy resolution mode for U49-2 undulator at BESSY-II

A PGM beamline has been designed for the U49-2 undulator at BESSY-II in whi ch the collimation by the preoptics is done in the dispersive and horizonta l direction. The beamline is characterized by high flux, high brightness, h igh spectral resolution (E/DeltaE>5000) over a wide spectral range of simil ar to 70-1500 eV and a relatively small spot size of 70 um x 20 um (fwhm). To achieve high spectral flux two interchangeable blazed gratings are used in the monochromator. For this beamline a new drive mode has been derived i n which almost constant spectral resolution can be maintained while driving the monochromator on-blaze. This constant resolution is maintained even fo r gratings with different line densities. (C) 2001 Elsevier Science B.V. Al l rights reserved.