Determination of the effective detector area of an energy-dispersive X-ray spectrometer at the scanning electron microscope using experimental and theoretical X-ray emission yields

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.A method is proposed to determine the effective detector area for energy-dispersive X-ray spectrometers (EDS). Nowadays, detectors are available for a wide range of nominal areas ranging from 10 up to 150 mm2. However, it remains in most cases unknown whether this nominal area coincides with the “net active sensor area” that should be given according to the related standard ISO 15632, or with any other area of the detector device. Moreover, the specific geometry of EDS installation may further reduce a given detector area. The proposed method can be applied to most scanning electron microscope/EDS configurations. The basic idea consists in a comparison of the measured count rate with the count rate resulting from known X-ray yields of copper, titanium, or silicon. The method was successfully tested on three detectors with known effective area and applied further to seven spectrometers from different manufacturers. In most cases the method gave an effective area smaller than the area given in the detector description

EDXTOOLS - Computer Programmes for the Determination of Critical EDX Spectrometer Parameters

Quality assurance according to ISO or EN norms entails a periodical check of critical instrumental parameters. Not yet all commercial software purchased with instruments supports the related measurements and their fast evaluation. EDXTOOLS consist of a programme library which complements the existing software for electron excited energy dispersive X-ray spectrometry (EDS) in this respect. EDXTOOLS can be used to check the detection efficiency by the evaluation of the L/K intensity ratio in a copper or nickel spectrum or by the calculation of the thickness of absorbing detector layers from experiments, which can be performed on any scanning electron microscope. Moreover, measured spectra can be modified by the transmission curve of absorbing media to estimate their influence on the result of quantitative analysis. EDXTOOLS allow the determination of the signal to background ratio from an Fe-55 spectrum and the fitting of measured FWHM's of K-lines to find the resolution curve DE = Ö{DE 2el + DE 2det}. They are completed by the possibility of calculating EDX spectra for the K-lines of light elements and to compare the resulting spectra for different formulae, physical data tables, and detector parameters chosen for the calculation. EDXTOOLS are written in MATLAB®, a wide spread interpreter language. This has the advantage that the programmes are readable text files. A user can check each computational step and modify it. The installation of MATLAB® and its optimization toolbox is necessary to work with EDXTOOLS