Dispersive EXAFS apparatus at Frascati

We report the successful design and test of a dispersive extended x-ray absorption fine structure (EXAFS) apparatus at Frascati. This technique is capable of measuring x-ray absorption spectra in fractions of a second and makes time-resolved structural studies possible. We describe the design of the instrument and compare the experimental performance with theoretical predictions. An energy resolution of 2-3×10-4, an energy dispersion ranging from 350 to 870 eV (at 7 to 11 keV), a spot size between 0.5 to 1 mm, and a flux of the order of 106 photons/s/pixel/100 mA was achieved. EXAFS spectra with good signal-to-noise ratio can be obtained in 100 to 600 ms on concentrated samples.