Measurement of detection efficiency and response functions for an Si(Li) x‐ray spectrometer in the range 0.1–5 keV

Abstract

AbstractEfficiency and response functions were determined for a modern commercial energy‐dispersive x‐ray spectrometer in the photon energy range 0.1–5 keV using dispersed and undispersed synchrotron radiation. The spectrometer was equipped with an Si(Li) detector crystal, a thin‐film window and a digital pulse processor. Monochromatized synchrotron radiation from the PTB VUV radiometry beamline at the electron storage ring BESSY was used for the absolute determination of the detection efficiency with a typical relative uncertainty of 1–2% in the photon energy range 0.1–1.5 keV by direct comparison with calibrated photodiodes. At higher photon energies, the efficiency was found by comparison of the measured and calculated undispersed synchrotron radiation spectrum. The absolute intensity of the synchrotron radiation was known with a relative uncertainty of less than 1%. In the overlapping region, the results from the two independent experiments are in full agreement. The energy dependence of the measured efficiency can be explained only with a detector model assuming that there is no dead layer. A simple model for the effect of incomplete charge collection (ICC) was applied to describe the measured response functions. Consequences of the ICC such as broadening and shift of low‐energy peaks and redistribution of counts around 1.84 keV are explained with the model, in accordance with the experimental results. Copyright © 2001 John Wiley & Sons, Ltd.