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In soft x-ray fluorescence yield near edge spectroscopy (FYNES) experiments it is desirable to reduce the ratio of scattered relative to fluorescent radiation emerging from the sample. Just above an absorption edge the fluorescent and elastically scattered photons have similar energies and cannot be electronically discriminated in our proportional counter detector. For low concentration (10 ppm) samples a large detector area maximizes collected light but allows scattered radiation over a large solid angle to contribute. One approach to improve photon collection in FYNES employs a focusing multilayer mirror analyzer. This device would intercept a significant fraction of solid angle around the sampling point. Photons would arrive at near-normal incidence, be energy analyzed, reflected, and focused onto the detector element. The problem of a multilayer's low reflectivity may be counterbalanced by its large area, ability to concentrate flux and, particularly, its ability to discriminate between fluorescent and scattered light. Model multilayer mirror devices have been obtained and we have undertaken an examination of their soft x-ray performance at the National Synchrotron Light Source. The mirrors were energy calibrated and found to possess unwanted azimuthal grading of 2d spacing. In fluorescence yield tests a multilayer mirror used as an analyzer exhibited filtering behavior at special angles which utilized only small regions of the mirror surface. It is expected that improvements in mirror fabrication or reevaluation of experimental geometry will make multilayer mirror analysis the procedure of choice for low background, low concentration FYNES studies.
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