Vacuum ultra violet monochromators

The field of UV monochromators for synchrotron radiation work is surveyed with special emphasis on the 10-300 Angstroem region. The three main classes of instrument considered are the constant deviation Rowland circle types, the plane grating types and the simple rotation toroidal grating monochromator (TGM). It is argued that the Rowland designs are unsatisfactory in various ways and that their good resolution properties can be matched by plane grating devices operating with modern dedicated storage ring sources. For low resolution applications the use of toroidal grating instruments is preferred. Since the desing of TGMs is a relatively young art, a good deal of explanation and discussion is included on the theoretical basis of the procedure. Some detailled consideration of the most important resolution determining aberrations is given and some particular examples and ray traces are shown. (orig.)