| Scripting Resources for DigitalMicrograph™ |
| HADES - High Accuracy Dual EELS System | |
Function |
A script-based implementation of Dual EELS which also permits dispersion calibration and measurement of non-uniformity in dispersion and HT stability. |
Version |
version:20230320, v1.0 |
Author |
D. R. G. Mitchell |
Acknowledgements |
The HADES calibration function permits measurement of the non-uniformity of the spectrometer EELS dispersion using the method of Webster et al. Some of their script functions are used herein. HADES dual EELS data combined with non-uniformity of dispersion calibration data can be used to correct the non-uniformity using Webster et al.'s correction script. This can be downloaded from a Git Hub repository - linked in their paper. |
Comments |
Dual EELS is a technique by Gatan which uses fast hardware acquisition to (almost) simultaneoulsy acquire low loss and core loss data, permitting accurate determination of EELS edge energies, independent of any drift in the microscope HT. This script package attempts to do something similar using existing Gatan hardware (GIF and CCD) and script. Due to the absence of fast hardware, there are many limitations with using script control. However, the technique can work and it is certainly a good way of demonstrating the utility of the techique and for building a case to obtain funding for a Gatan Dual EELS system. The Calibration function in HADES permits the average dispersion of the spectrometer to be measured along with any non-uniformity in that dispersion across the spectrum. Webster el al. developed a technique to measure and correct such non-uniformities, to further enhance the accuracy of edge energies. Data produced with this script can be used with their correction script (available via a Git Hub repository - detailed in their paper), to correct the dispersion non-uniformity in dual EELS data obtained with this script. This script produces data sets comprising a low loss spectrum image and a core loss spectrum image. Supporting scripts enable any energy drift in the former to be corrected and then applied to the latter. The calibrated dispersion can be used in place of the nominal dispersion of the spectrometer and calibration data can be analysed to measure the HT stability of the microscope. |
System Requirements |
This script should be compatible with all recent versions of DigitalMicrograph, but was tested exclusively on GMS 2.32. If using in GMS 3.x, have only one workspace open. The HADES script was tested exclusively on a JEOL ARM200F. However, there is no specific microscope dependency, the only requirement being that the system is capable of EFTEM, since during calibration the script will change the microscope HT. This was tested on a Gatan model 963 Quantum GIF. However, it should be compatible with any similar GIF. The script needs to change the GIF drift tube voltage and provided the system permits that then it should work fine. The critical hardware limitation is that this script will only work on a system which has a CCD camera - it was tested on a GIF fitted with an Ultrascan 2k x 2k camera. The camera frame refresh during calibration/acquisition is used to synchronise the acquisition - with typical frame times of 1-10s. With a newer CMOS camera, such as the Rio16 or OneView, the refresh rate is 25 frames per second, and the synchronisation will not work. |
Known Issues |
WARNING: This script will expose the camera to intense zero loss peaks. Careless or incorrect use could result in the camera scintillator being permanently damaged by excessive beam intensity. This software must only be used by experienced EELS practitioners and then, only after obtaining the approval of the microscope manager to do so. This script will only work on EELS systems using CCD cameras. It will NOT work on systems with rapid refresh (25fps) CMOS-type cameras. There are many compromises which must be made to get a script-based dual EELS system working. Due to the need to keep zero loss intensities within safe ranges, beam intensities used may be much weaker than are typically used for regular EELS. This can result in core loss spectra with low signal-to-noise ratios or requring very long integration times. The drift tube shuttering of the zero loss peak results in an overshoot peak in the low loss spectrum. This is described in the manual. It will not adversely effect energy correction, but the use of such low loss spectra for deconvoluting plural scattering is questionable. The methods described for controlling beam intensity during use include changing the FEG extraction voltage. This has the potential to damage some types of FEGs, if done incorrectly. Again, only experienced practitioners should attempt these methods, and then only after receiving approval of the microscope manager to do so. This software is provided in good faith by the author. However, no warranty is provided as to its fitness for purpose. Users of this software accept full responsibility for any damages or losses which might arise from its use.
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Supported |
Yes. Due to budget cutbacks my job has now ended and I no longer have access to microscope hardware. If you have issues with this script I will attempt to resolve them. However, it may not be possible for me troubleshoot, especially where your system is different to that on which I developed this (see System Requirements). |
Included Files |
zip archive containing the scripts and a manual. |
Source Code |
see attached zip archive |