Development of a new energy scanned (4-20 keV) EXAFS-II spectrometer at LURE

The new energy scanned EXAFS spectrometer (EXAFS-II) which has been recently installed on beam line D2 at LURE (Orsay) is described in this paper. The key component of the spectrometer is a versatile monochromator operating in a vacuum of approx.=10-3 Torr. It uses a vertically dispersing two separated crystal design in the (+, -) arrangement which offers an exit beam of constant offset and direction relative to the incident beam, optional sagittal focusing and order sorting. Also optional is the energy modulation provided by a piezoelectric transducer capable of small angular oscillations of up to 1 kHz. Conventional gas filled ion chambers are used as detectors - even for fluorescence EXAFS - but each detector is incorporating a home-made, ultralow noise, fast preamplifier capable of detecting weak signals even at a high modulation frequency (1 kHz). Glitch-free spectra have been recorded over the whole energy range covered by DCI in standard operating conditions. (orig.)