DESCRIPTION (Verbatim from the Applicant's Abstract): It has been demonstrated that multilayer analyzer array detector is advantageous in x-ray fluorescence detection under high flux and dilute metal conditions. With a good rejection rate, about 25 times, and reasonably large solid angle, sub-millimolar concentration can be routinely accessed. However, the performance of the detector is still lagging behind the photon flux and brightness increases at the third or even fourth generation synchrotron sources. With more than 100 to 1000 flux increases at the third generation source, these sources would permit detection of metal concentration in the order of 10 micro-Molar or several ppm range. This will allow the monitoring of some biologically relevant metals in vivo. Thus we propose to develop x-ray fluorescence detector using synthetic multilayer pairs. With two-stage rejection of primary and secondary multilayers, it is anticipated that the rejection rate will exceed 200 times. With a 20 percent throughput, the anticipated gain on the effective count rate can be as high as 40 times on dilute systems. Initial evaluation shows that the detector can be made tunable in a wide energy region and to cover a large solid angle. The major goal for the Phase I project is to design and fabricate a prototype multilayer pair detector. The test and evaluation of the detector performance will aid in the design of a multilayer pair analyzer array detector. Phase II project will develop such a detector to a product. PROPOSED COMMERCIAL APPLICATION: The need for a very sensitive and high count rate x-ray fluorescence detector is well justified. The instrument will be vital to x-ray spectroscopy and micro fluorescence imaging on biological systems under high flux and dilute situations. With ever increasing photon flux at the new synchrotron sources, the detector will have a better market potential than fluorescence ionization chambers and the solid state detectors which are currently available.