Quantitative lateral resolution of a Quantum 2000 X‐ray microprobe

Abstract

AbstractThe minimal primary X‐ray beam size of a Quantum 2000 scanning X‐ray microprobe is in the order of 10 µm. This value is obtained by measuring the distance required for a 20–80% signal increase when scanning over a material edge. But for a more precise determination of the quantitative lateral resolution of the instrument the long tail contributions of the primary X‐ray beam have to be taken into account.To measure these long tail contributions, Pt apertures of different diameters usually used in electron microscopes are utilized. When the primary X‐ray beam is positioned in the center of the aperture, the Pt count rate gives an estimation of the long tail X‐ray contributions from outside the aperture radius. This count rate can then be normalized by a second measurement on homogeneous Pt metal.In this way, the quantitative lateral resolution function for a Quantum 2000 X‐ray microprobe was determined. In particular, it was found that independent from the primary X‐ray beam size, an aperture size of approximately 450 µm is necessary to reduce the Pt signal to 1% of the reference signal. A knowledge of the quantitative lateral resolution function is essential to estimate the accuracy of trace element detection on small sample features because of the trade‐off between lateral spatial resolution and elemental detection limit. Copyright © 2008 John Wiley & Sons, Ltd.