New plane-grating monochromators for third generation synchrotron radiation light sources

For the electron storage ring BESSY II a new type of plane-grating monochromators working with collimated light is proposed. The operation with collimated light is a well-known optical technique, which enables us to keep the focusing condition fulfilled automatically for all photon energies. The additional degree of freedom gained allows the monochromator to comply with the most different needs of the users. An additional feature of the design is the further extension of the already widely accessible energy range of a PGM towards lower photon energies. The BESSY beamline concept, which requires an additional mirror in front of the monochromator allows the collimation of the light with the presently planned number of optical elements.