Undulator QEXAFS at the ESRF beamline ID26

Undulator Q-EXAFS with continued scanning of undulator gap is routinely performed at the ESRF beamline ID26. The undulator gap is changed at constant speed while the monochromator angle is changed at variable speed. The flux loss when doing this, if any, can be kept below 10 % of the photon flux one would obtain when moving the undulator step by step. Spectra reproducibility is better than 0.1 eV. The acquisition time of a 1 keV scan goes from seconds to minutes as function of energy, harmonic selected and resolution required. Present limits of the technique and its applications are presented.