NOVEL SILICON DETECTORS FOR EXAFT STUDIES

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DESCRIPTION (Provided by Applicant): The availability of intense sources of synchrotron X-rays has made possible advanced studies of biological materials using the method of X-ray absorption spectroscopy (XAS). The advances, both in intensity as well as optics of these sources enables exploition of ultra-dilute spectroscopy and fluorescence QuEXAFS techniques [Farrow]. Current biophysical research utilizing these techniques includes studies of enzyme reactions, hemoglobin, and general study of metabolic processes. In these biological XAS studies, the experiments are now mostly limited by the X-ray detectors because they are not able to take full advantage of the available X-ray flux. Central to the design of modern XAS instrumentation is a very low noise X-ray detector, which must detect the fluorescence X-rays from the samples. It is important for the detector to operate with very high energy resolution and maintain that resolution at very high count-rates. Currently, germanium and lithium drifted silicon are the most popular detectors for XAS and EXAFS studies. Both these detector systems, while capable of excellent energy resolution, have some limitations. Si(Li) detectors have relatively high capacitance for larger sizes which increases their noise when operated at fast integration times. For High purity germanium (HPGe) detectors, the presence of Ge Ka fluorescence (9.876 keV) and the associated escape peaks in energy range of interest compromises the EXAFS data collection for hard X-ray experiments. In order to overcome these limitations, we propose to investigate a novel low capacitance detector design with high purity silicon as the detector material.