Tecnai on-line help manual -- Alignments - UT Southwestern

<strong>Tecnai</strong> on-line help Alignments 80<strong>Tecnai</strong> 12 Software version 215 LM-EFTEM Procedure15.1 LM-EFTEM PreparationPurpose: Set up microscope for aligning the column for EFTEM.Importance: ESSENTIAL to make sure the alignment is done for the correct conditions: centered C2aperture, eucentric height and specimen in focus. Also find a recognizable image feature for lateralignment steps.Notes:• Because of the difficulty of aligning the microscope for EFTEM (image/diffraction shift and cross-overcorrection are often quite critical, otherwise there is no image or diffraction pattern visible on theImaging Filter), the EFTEM alignment procedure contains two parts, one a pre-alignment, where allalignments are done with the screen down, the other the final alignment where all is aligned on theFilter itself. Once the microscope has been aligned properly, the pre-alignment should not benecessary anymore and the final alignment can be used for fine-tuning.• The EFTEM alignments are in many cases (lower magnifications and camera lengths) sensitive tohysteresis. It is therefore important to use the normalization facility of the microscope to make imageand diffraction-pattern positions reproducible.15.2 LM-EFTEM Image-shift pivot pointsPurpose: Align image shift pivot point = make sure that the diffraction pattern does not shift when theimage shift is changed.Importance: ESSENTIAL for the proper functioning of image shifts and cross-over correction.Method: Minimize the movement of the diffraction pattern. The microscope 'wobbles' the image shiftwhich should cause no diffraction shift.ProcedureThe alignment procedure consists of six steps :• Two preparation steps for setting up the image in normal and EFTEM modes.• Two steps for setting up the diffraction pattern in normal and EFTEM modes.• Two steps in which the X and Y pivot points are aligned.In EFTEM a misaligned image shift will lead to an apparent diffraction shift when the cross-overcorrection is changed.DescriptionThe alignment of the pivot points of the image deflection coils is essential to the proper functioning ofmany other alignments and calibrations: image shifts, diffraction shifts, detector alignments andmeasurement functions.The image coils pivot points (image shift and diffraction shift) alignment is reasonably insensitive to theoperating conditions and normally needs to be done only once. It is important that the image coils pivotpoints are aligned prior to aligning other parts of the microscope where the image coils are used,otherwise the latter alignments may have to be redone. Alignments where the image coils are used arethose where images or diffraction patterns are moved (image shift, diffraction shift/diffraction alignment).15.3 LM-EFTEM Diffraction-shift pivot pointsPurpose: Align the diffraction shift pivot point = make sure the image does not move when the diffractionshift is changed.