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

<strong>Tecnai</strong> on-line help Alignments 41<strong>Tecnai</strong> 12 Software version 28 Image LM Procedure8.1 Preparation Image LM alignmentPurpose: Set up microscope for aligning the lower part of the column (imaging system) in LM.Importance: ESSENTIAL to make sure that the alignment is done for the correct conditions: centeredC2 aperture, eucentric height and specimen in focus.Method:C2 aperture centering:• Focus spot and center it on the screen• Turn INTENSITY overfocus (clockwise)• Center aperture until illuminated area is symmetrical around the screen centerEucentric height: with the CompuStage switch on the Alpha wobbler and minimize image movement bychanging the Z height.8.2 Pivot point image shift LMPurpose: Align image shift pivot point = make sure that the LAD diffraction pattern does not shift whenthe image shift is changed.Importance: ESSENTIAL for the proper functioning of image shifts.Method: Minimize the movement of the diffraction pattern. The microscope 'wobbles' the image shiftwhich should cause no diffraction shift.ProcedureThe alignment procedure consists of four steps:• Two preparation steps for setting up the image and diffraction pattern, respectively.• Two steps in which the X and Y pivot points are aligned.Note: Diffraction focus: in LAD the objective lens (which is here the focusing lens) is switched to fixedsetting. To focus the diffraction pattern to a spot pattern the Intensity should be used, not the Focus.Only if the pattern cannot be focused with the Intensity should the Focus knob (objective lens) be used.In the latter case, turn the Intensity completely overfocus (clockwise), then focus the LAD pattern withthe Focus knob.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).8.3 Pivot point diffraction shift LMPurpose: Align the diffraction shift pivot point = make sure the image does not move when the diffractionshift is changed.Importance: ESSENTIAL for the proper functioning of image and diffraction shifts.