Dave Mitchell's DigitalMicrograph™ Scripting Website

Function

A plugin designed to monitor EDS detector performance.

Version

version:20221112, v2.0

Author

D. R. G. Mitchell

Acknowledgements

Vincent Hou's improved version of my Gaussian Fitting script is used herein. Ray Twesten is thanked for his TIA EDS spectrum reading code.

Comments

The merits of using a NiO thin film on a Mo grid as an EDS monitoring specimen have been demonstrated by Hovington et al. (Microbeam Analysis 2 (1993) 277), Egerton and Cheng (Ultramicroscopy 55 (1994) 43) and others. A wide range of detector performance parameters can be obtained, including resolution (interpolated to Mn Ka), Fiori number, solid angle, X-ray cleanliness, the extent of ice and carbon contamination etc. It is designed with the FEI Super-X EDS array in mind. This windowless SDD system has the potential to develop ice and carbon contamination layers during use. Effective monitoring will enable appropriate warm-up cycles to be applied and tested for efficacy. However, this plugin can be used to monitor any EDS system (SDD or SiLi) on any TEM operating at between 100kV and 400kV. Even windowed systems have the potential to ice-up due to permeability of the window and/or perforations therein. I know Oxford windowed EDS systems have a conditioning cycle to de-ice the detector. This warms just the detector crystal while the dewar is maintained at liquid nitrogen temperature. This software will help assess the effectiveness of this cycle.

The plugin will read Gatan (.dm3 and .dm4), TIA .ser, EMSA/M, Bruker text and Noran .emsa files. If spectra can be read into DigitalMicrograph via any other route, then such spectra can also be processed. This plugin is also useful for evaluating new EDS installations for alignment and performance against manufacturers' specifications.

Updates included in v2.0: In GMS 3, dialogs are no longer treated as floating windows, and this caused things to move around in unexpected ways. This has been resolved and other minor formatting issues addressed to make this script compatible with GMS 3. There is no new functionality in the script, so if you are using an older version in GMS 2.x - there is no need need to update.

System Requirements

Tested on GMS 2.32 and 3.2 running under Windows 10. Spectra from NiO thin films on Mo support grids are required for this analysis. Suitable specimens can be purchased from Ted Pella Inc. and a very useful technical note on the methods can be found at: here.

Known Issues

The dialog is quite large, and a small laptop screen may not be big enough to display it.

WARNING: A liquid nitrogen cooled SiLi detector should, generally never be warmed to room temperature, unless specifically designed to do so. If the detector must be warmed for any reason, then the detector bias must be off, otherwise the detector will be destroyed. Ideally power down the entire EDS system to be absolutely certain it is not energised. The dewar must be actively pumped by a turbo pump during the warm up. If not, the sorb in the dewar, which has absorbed any minor leaks over the months/years it has been kept cold, will outgas and could pressurise the vacuum space. This is often enough to burst the thin window and ruin the detector - and seriously mess up your column vacuum, if there is no gate valve. Always consult your vendor before warming an EDS detector which is meant to be kept cold permanently. In contrast to SiLi detectors, SDD detectors are peltier cooled and so can be readily warmed and cooled, because there is no dewar/sorb. FEI's Super-X is unusual amongst SDDs in that it doesn't use peltier cooling. Instead indirect liquid nitrogen cooling is provided from the anticontamination device. This detector is designed to be warmed up periodically.

Supported

Yes

Included Files

zip archive containing a plugin and a PDF manual. A sample spectrum is included for experimentation. The experimental details of the acquisition are in the spectrum's file name.

Source Code