ENERGY-RESOLVING X-RAY-FLUORESCENCE DETECTION USING SYNTHETIC MULTILAYERS

The potential of synthetic multilayers for energy-resolving the X-ray fluorescence in X-ray absorption fine structure (XAFS) experiments is discussed. Two detection systems, one using curved multilayers and the other using graded multilayers to select X-ray fluorescence photons, have been designed to cover a wide energy range with a usefully large solid angle. Such a detector will be more advantageous than the barrel -like crystal-array detector because of the unique properties of synth etic multilayers, such as larger horizontal acceptance angles and band width. In addition, the detector should be much simpler to construct a nd readily accommodates energy changes, especially the detector using graded multilayers. Comparison of the multilayer array detector with c onventional detectors, such as ionization chambers and conventional 13 -element Ge detectors, shows that the proposed system will be superior , particularly with the increased photon fluxes available from inserti on devices and with decreased sample concentration, since this detecti on system eliminates the 'bad' photons before they enter any X-ray det ector. Consequently, the X-ray detector proper for this system does no t suffer from the incident-count-rate bottleneck common to current X-r ay fluorescence detectors with energy resolution by signal processing. Thus, this new fluorescence detection system will provide tremendous opportunities for XAFS measurements on dilute systems, such as biologi cal systems, at third-generation synchrotron sources.