Issues concerning solid state detectors for EXAFS
Fluorescence extended x-ray absorption fine structure spectroscopy (EXAFS) is a commonly used technique in conjunction with x-ray synchrotron radiation for studying the local atomic structure of dilute elements in biological, geological and materials systems. Due to the nature of the EXAFS technique, and the difficulties associated with the detection of low energy x-rays, EXAFS has been used primarily in the energy range above 5 keV. However, there are a number of elements of interest with K- or L-absorption edges below 5 keV, which have not been easily accessible with existing EXAFS instrumentation. Several characteristics of solid state detectors must be optimized for use in low energy EXAFS measurements. The detector entrance window, or ``dead layer,`` must be as thin as possible to minimize the attenuation of the fluorescent signal. The detector spectral backgrounds must be minimized so that the tailing background on the low energy side of the scattered photopeak is as low as possible to maximize the S/N of the fluorescent photopeak. Based on our work, a thin Pd surface barrier contact on a Si(Li) detector offers the thinnest detector dead layer and also the lowest spectral background for the Si(Li) and Ge detectors studied to date. To maximize the S/N, the detectors must be operated at as high a count rate as possible, without compromising detector energy resolution. High count rates can be achieved using multiple detector arrays; close packing of the detector elements can further increase the S/N by utilizing the ``best`` portion of the scattered polarized synchrotron beam.
- Research Organization:
- Lawrence Berkeley Lab., CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 10107942
- Report Number(s):
- LBL-31419; CONF-9109322-1; ON: DE92004173
- Resource Relation:
- Conference: European workshop on X-ray detectors for synchrotron radiation sources,Aussois (France),23 Sep - 4 Oct 1991; Other Information: PBD: Oct 1991
- Country of Publication:
- United States
- Language:
- English
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