COMBINING ROTATION AND TRANSLATION IN A VARIABLE LINE SPACE HIGH-RESOLUTION SOFT-X-RAY MONOCHROMATOR - DESIGN REQUIREMENTS AND PERFORMANCE EVALUATION OF A NOVEL GRATING MOUNT

We describe a new fixed-slit single-element spherical-grating monochro mator which has been designed, built and tested for the new high-resol ution soft X-ray beamline at the University of Wisconsin Synchrotron R adiation Center. A novel grating mount utilizes a combined rotation an d translation of a variable line space grating to minimize major aberr ation terms. The resolving power of the aberration-corrected monochrom ator is then primarily determined by the finite figure error and the m echanical performance of the grating mechanism. Assuming a 0.2 arc sec figure error, a resolving power ranging from E/DELTAE = 10(4) to 4.6 x 10(3) over the energy range of 500 to 1150 eV requires grating rotat ion and translation to be synchronized with a precision and accuracy o f the order of 0.1 arc sec and 10 mum respectively. Extensive testing has verified precision and allowed appropriate calibrations to be deve loped to obtain the required accuracy. Calibrations minimize the impac t of specific component behavior such as the compression of linear cro ssed roller bearings, the characteristic signature of a lead screw and the elastic response of the support structure.