MicroXAFS Using Tapered Capillary X-Ray Concentrators. Dale L. Brewe^*, Steve M. Heald^**, Bill Barg^*, Frederick. C. Brown^*, Kyungha H. Kim^*, and Edward A. Stern^*, ^*University of Washington Dept. of Physics, Seattle WA, ^**Pacific Northwest National Laboratory, Richland, WA

Tapered capillaries are a means to concentrate x-rays from synchrotron sources into microbeams with diameters on the order of 1 micrometer or less, and with fluxes at third generation sources comparable to or greater than those available in macroscopic beams at second generation sources. At third generation sources flux densities can exceed 10¹⁰ ph/sec/micron². Thus, capillary concentrators can enable techniques such as x-ray absorption spectroscopy with spatial resolution at the submicrometer level, and with signal quality comparable to that available for macroscopic measuments in the past. This ability will be important in characterizing complex multiphase materials, in particular those with environmental impact such as wastes at former nuclear weapons production sites. Practical problems, however, such as the proper way to normalize to incident intensities, must be solved. The Pacific Northwest Consortium Collaborative Access Team at the Advanced Photon Source is developing capillary concentrators, and beamlines with an emphasis on microbeam capabilities, including microXAFS. The potential for performing microXAFS spectroscopy at the APS will be discussed, as well as initial results in obtaining micro-XAFS spectra and x-ray micro-images using capillary concentrators, and practical issues involved in achieving further progress.