An exchangeable Bragg/Laue polychromator for energy-dispersive XAFS

An original design for a cooled exchangeable polychromator for energy-dispersive XAFS (X-ray absorption fine structure) working either in the transmission configuration (Laue case) or in the reflection configuration (Bragg case) is presented. It enables the acquisition of X-ray absorption spectra between 5 and 25 keV with a spot size on the sample that can reach to less than 20 microm FWHM for some energies. Only 1 h is needed to exchange both benders in operative mode. Parallel transmission spectra with a bandpass between 5 and 10% can be obtained in the full energy range. The dispersive optics and mechanics of ID24 (ESRF, Grenoble, France) have been designed to obtain XAFS spectra in less than 1 s and, in some cases, in the millisecond range.