Determination of the detection efficiency of an UTW detector and modelling of spectra used for the quantification of EDS analyses of light elements

The increased use of Si(Li) energy dispersive x-ray spectrometers (EDS) with a windowless (WL) or ultra thinwindow (UTW) detectors has made the detection of light elements down to Be a routine laboratory procedure. The quantification of EDS spectra implies that the net intensity of the characteristic peak of interest must be determined accurately. For light-element x-rays for which the background is non linear and for which the Kα lines can often overlap with the L and M lines of transition metals, the simple determination of the characteristic intensity is not a straightforward operation and often requires sophisticated data processing. The use of a conventional least-squares fitting technique with prefiltering of standard spectra for deconvolution is made difficult by the non-linearity of the background, the presence of the triggered noise peak below 0.3 KeV, and the lack of appropiate standards. In addition to the difficulty associated with the determination of the net intensity, the uncertainties for the detection efficiency below 1 Kev has limited the use of standardless procedures for quantification.