A feedback control system for synchrotron radiation double crystal instruments

Abstract An analog feedback control system has been built for instruments which use synchrotron X-radiation and double cyrstal arrangements in a parallel setting as monochromator or plane wave generators. A normalized signal as measure for the crystal reflectivity is used to maintain the relative crystal alignment. The working point can be set on either side of the rocking curve. The system is stable during an energy scan as well as at a fixed angle. It can therefore be used for X-ray spectroscopic studies such as EXAFS and for diffraction work such as X-ray standing wave analysis and topography.