Dave Mitchell's DigitalMicrograph™ Scripting Website

Function

Analyses all open CCD images of converged probes - STEM, CBD etc and reports dimensions (FWHM, FWTM), intensities, current and displays intensity profiles.

Version

version:20130201, v1.0

Author

D. R. G. Mitchell.

Acknowledgements

-

Comments

WARNING: Converged probes can be extremely intense and have the potential to damage a CCD. Ensure the intensity in the probe is not too high; use 1x binning at the CCD and use a very high magnification to spread the probe out over the CCD. If vertical streaks occur (blooming) the probe current is too high. The probe should be roughly centred in the image, but it is not too critical.

This script is particularly useful with FEI TEMs which have the ability to image the STEM probe. On JEOL TEMs one can image a CBD alpha 9 probe, which is used in STEM, but there are no guarantees that what you see in CBD mode, is what you are using in STEM mode, especially if your STEM alignment is not good.

This script will analyse all open images (any open 1D profiles will be ignored) and do the following: collapse the image vertically into a 1D intensity profile, calculate the full width half and tenth maxima in calibrated units - ie how wide the probe is, the intensity of the FWHM part of the probe relative to that contained within the FWTM. If the image contains an intensity calibration (counts to electrons) then from the exposure time and total counts in the image, the current in the probe is calculated. On the FEI Osiris TEM the agreement with the current indicated on the FluCam screen is to within a factor of two.

Data are output to the Results window and to a text window in tab delimited format. Simply save the latter as a normal text (script .s) file and then open it in Excel - use the default import options and analyse the data further.

System Requirements

Probe images can be recorded on any camera but high bit depth (16bit), high resolution (2k x 2k) cameras such as the Ultrascan, give best results. Compatible with GMS 1.x and 2.x.

Known Issues

The CCD current value is entirely dependent on the the intensity calibration (counts to electrons) being present. It usually is on GIF-based systems, but may not be present on camera-based systems. If so, the current reported by the script will read zero. Use the current readout from the fluorescent screen - remember to multiply it by 1.3 for backscatter losses (200kV) or 1.1 (300kV). The screen readout current on the Osiris is factory calibrated according to FEI, but no details of this are provided by the engineer. Accurate currents are best obtained from a Faraday cup holder or by using the Drift Tube on the GIF.

Supported

Yes.

Included Files

Script File.

Source Code