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25 from x ray creation to quantitative results there

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Unformatted text preview: nd the underlying principles (physics) behind the data-analysis – such that you are a sophisticated analyst rather than a mere user (and slave to canned systems). The data reduction software will often present procedure choices; by understanding the physics, one can make beneficial choices. CBEMS 164 – XRD, SEM & Microanalysis: Lecture 13 ! 25 From X-Ray Creation to Quantitative Results! •  There are two parts to the problem –  What happens to the x-ray signal within the sample before exiting in the direction of the detector –  What happens to the signal within the detector before a count is added to a channel in the multichannel analyzer (MCA) CBEMS 164 – XRD, SEM & Microanalysis: Lecture 13 ! 26 Problem is Worked Backwards! •  The data is the spectrum •  For a quantitative analysis –  need to work backwards to calculate what x-ray intensities needed to have been generated within the sample –  Detector artifacts need to be identified –  Corrections for in-sample events need to be accounted for - ZAF corrections CBEMS 164 – XRD, SEM & Microanalysis: Lecture 13 ! 27 Issues with Quantitation! •  Electron beam impinges on sample –  Interacts with sample within an interaction volume –  Energy loss in incident beam during multiple interaction events result in generation of characteristic and background x-radiation •  X-rays leave point of creation in all directions –  Intensity generated is f(Z) –  Some...
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