Fluorescence detection, in principle, permits the detection of the extended x-ray absorption fine structure (EXAFS) of more dilute atoms than can be obtained in absorption. To take advantage of this it is necessary, in practice, to eliminate the background that normally accompanies the fluorescence signal. We describe an x-ray filter assembly that accomplishes this purpose. The unique characteristic of the assembly is a slit system that minimizes the fluorescence background from the filter. The theory of the slit assembly is presented and is found to agree with measurements made on the Fe EXAFS of a dilute sample. The filter assembly has a better effective counting rate in this case than that of a crystal monochromator design.
Bibliographical noteFunding Information:
One of us (EAS) is indebted to a stimulating conversation with Dr. David F. Anderson which sparked the line of thought leading to the design presented here. Our thanks are also due to Dave Garcia and Don Russell for machining the slit assembly. SSRL is supported by the National Science Foundation in cooperation with the Department of Energy. This work was supported in part by a research grant from the National Science Foundation.