Introduction
This guide from the Center for Microscopy and Image Analysis, UZH, Zurich, Switzerland shows how tune the BioQuantum energy filter of the K3 Gatan camera, at the transmission electron microscope Titan Krios G3i.
Please find more detailed information about the system here.
To be done once a week after every camera cycle, but also whenever the energy filter is not stable or before the data acquisition of your life.
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Go to a void area of your grid (broken mesh/void).
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Select the linear mode of the K3 camera and click binning 1x.
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Bring the electron dose to 900 e-/pic/sec. Be sure to use the the same mag you would use for image acquisition. Usually, for such dose rate, you would need to use the C2 aperture of 150 um, spot size 1 and the illuminated area of around 900 nm.
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Be sure to be on the linear imaging mode, otherwise you could burn the K3 camera!!!!
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To tune the Energy Filter Click on "Tune GIF".
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Click on the little wheel to check what the quick and full tune include.
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The GIF alignemnt setup window will pop up, and you can see what tuning parameters are selected for full and quick tune.
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Select, with the tick in the "Quick Tune" column: Image centering, Spectrum focus and Spectrum aberration, click OK.
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Tune the energy Filer, by clicking "Quick Tune".
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When it is done, reopen the GIF alignment Setup, and select the "Achromaticity", click OK.
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Perform the "Quick Tune".
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When it is done, reopen the GIF alignment Setup, and select the "Image Distortion", click OK.
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Perform the "Quick Tune"
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Image distortion tuning is followed by image magnification tuning. Examples of expected results of both are shown on the corresponding image: the distortion error should be in the range of 0.001-0.010 (marked in red). The measured values for image magnification (marked in blue) should correspond to target values (marked in green).
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Importantly, both image distortion and magnification tuning use a mask with regularly spaced circular holes (marked in orange). If the pattern of circular holes becomes distorted (for examples please see the next image), the tuning didn't work as expected.
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In this case, please wait until the tuning is finished and then press "Undo the last tuning" (marked with a pink arrow). Then repeat the tuning by clicking "Quick Tune" again.
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Important: If you redo the tuning without undoing the previously unsuccessful tuning, the result will be even worse. In this case please reload the GIB settings (as described in Step 12 of this guide) and start Tune GIF from scratch.
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