NEW PLANE-GRATING MONOCHROMATORS FOR 3RD-GENERATION SYNCHROTRON-RADIATION LIGHT-SOURCES

For the electron storage ring BESSY II a new type of plane-grating mon ochromators working with collimated light is proposed. The operation w ith collimated light is a well-known optical technique, which enables us to keep the focusing condition fulfilled automatically for all phot on energies. The additional degree of freedom gained allows the monoch romator to comply with the most different needs of the users. An addit ional feature of the design is the further extension of the already wi dely accessible energy range of a PGM towards lower photon energies. T he BESSY beamline concept, which requires an additional mirror in fron t of the monochromator allows the collimation of the light with the pr esently planned number of optical elements.