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Mean Free Path Estimator

Category: Math functions & Calculations
Description: Script to generate a calculator-type dialog box, which allows the user to estimate the mean free path from the supplied experimental parameters. This script is based on the parameterised aproach of Malis et al., J. Electron Microsc. Tech. vol. vol. 8 (1988) p193., and so yields an approximate value - apparently usually good to within 20%. See also Carter and Williams, 'Transmission Electron Microscopy', section 39.5 "Measuring Thickness from The EELS". Note the collection angle has an effect on the mean free path. If you are capturing thickness maps with no objective aperture, then the collection semiangle (beta) will be >100mrad.This is outside the valid range for the equation. The script can also be used as a simple converter to convert at% to wt% and vice verse. Select which values (at% or wt%) you are supplying in the 'Calculate Using' radio box. The corresponding at% or wt% values will then be calculated. If you find bugs or errors with this script please let me know. This script was tested on DM 3.8.2 and 3.9.0. 1.4 Updated version: The reset button now resets the pulldown menus, improved trapping prevents nonsense values being geneated, and some bugs were fixed.
Comments: Some sections of code for this script were based on Bernhard Schaffer's EELS-Edges-Chart script. Lists of elemental data are from W Grogger (FELMI). The listing of atomic weights is by D. Mitchell
Acknowledgements: This script has not implemented the use of cross sections - the accurate way of calculating effective average atomic number. The difference between values calculated using cross sections and those based on a simple arithmetic mean (used in this script) are not great for compounds where the components are of similar mass eg for NiO the difference is 7%. However for WC the difference is 28%. I may implement cross sections in a future version.
Script version: 1.4
DM/GMS version: 3.9.2
Script written as a function: No
Source: Show code
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